JP6575137B2 - Discharge lamp driving device, light source device, projector, and discharge lamp driving method - Google Patents

Description

  The present invention relates to a discharge lamp driving device, a light source device, a projector, and a discharge lamp driving method.

  For example, Patent Document 1 describes a configuration in which the frequency of an alternating current supplied to a high-pressure discharge lamp is switched between a first frequency and a second frequency that is higher than the first frequency.

JP 2011-124184 A

  For example, in Patent Document 1, a period in which an alternating current of a first frequency is supplied in a half cycle length to a high-pressure discharge lamp (discharge lamp) is provided for the purpose of suppressing wear at the tip of the electrode. ing. However, in this method, for example, as the high-pressure discharge lamp deteriorates, there is a problem that the wear of the tip portion of the electrode cannot be sufficiently suppressed. Therefore, there is a problem that the life of the high-pressure discharge lamp cannot be sufficiently improved.

  One aspect of the present invention is made in view of the above problems, and is a discharge lamp driving device capable of improving the life of a discharge lamp, a light source device including such a discharge lamp driving device, and such Another object is to provide a projector provided with a simple light source device. Another object of one aspect of the present invention is to provide a discharge lamp driving method capable of improving the life of a discharge lamp.

One aspect of the discharge lamp driving device of the present invention includes a discharge lamp driving unit that supplies a driving current to a discharge lamp having electrodes, a control unit that controls the discharge lamp driving unit, and an inter-electrode voltage of the discharge lamp. A voltage detection unit for detecting, the control unit, a first period in which an alternating current having a first frequency is supplied to the discharge lamp, a second period in which a direct current is supplied to the discharge lamp, The discharge lamp driving unit is controlled such that a mixing period is alternately repeated, the first frequency includes a plurality of different frequencies, and the first period includes an alternating current supplied to the discharge lamp. The first frequency has a plurality of AC periods different from each other, and in the first period, the first frequency of the AC current becomes smaller in the AC period provided later in time, and the control unit detects The voltage between the electrodes and the Based on at least one of the driving power supplied to the lamp, and wherein the changing each of the first frequency of the plurality of the AC period.
One aspect of the discharge lamp driving device of the present invention includes a discharge lamp driving unit that supplies a driving current to a discharge lamp having electrodes, a control unit that controls the discharge lamp driving unit, and an inter-electrode voltage of the discharge lamp. A voltage detection unit for detecting, the control unit, a first period in which an alternating current having a first frequency is supplied to the discharge lamp, a second period in which a direct current is supplied to the discharge lamp, The discharge lamp driving unit is controlled so as to provide a mixing period in which the alternating current is alternately repeated, the first frequency includes a plurality of different frequencies, and the control unit detects the detected interelectrode voltage and the discharge voltage. The first frequency is changed based on at least one of driving power supplied to an electric lamp.

  For example, when the discharge lamp deteriorates and the voltage between the electrodes increases and when the driving power decreases, the driving current supplied to the discharge lamp decreases. Therefore, the bright spot of arc discharge tends to become unstable and easily moved. When the bright spot of the arc discharge moves, the melting position and the melting amount in the electrode change. As a result, the shape of the electrode becomes unstable and may be easily consumed. Therefore, there is a possibility that the life of the discharge lamp cannot be sufficiently improved.

  On the other hand, according to one aspect of the discharge lamp driving device of the present invention, the control unit sets the first frequency based on at least one of the interelectrode voltage and the driving power. Therefore, the bright spot of the arc discharge can be easily stabilized by increasing the first frequency as the drive current decreases. Thereby, consumption of an electrode can be suppressed and the lifetime of a discharge lamp can be improved.

  Moreover, since the first frequency includes a plurality of different frequencies, the thermal load applied to the electrode in the first period can be varied. Therefore, it is easy to maintain the shape of the protrusion of the electrode.

The control unit may set the first frequency based on the detected interelectrode voltage, and the first frequency may be set to increase as the interelectrode voltage increases.
According to this configuration, when the discharge lamp is deteriorated, it is easy to stabilize the bright spot of arc discharge.

The control unit may set the first frequency based on the driving power, and the first frequency may be set larger as the driving power is smaller.
According to this configuration, it is easy to stabilize the bright spot of arc discharge when the driving power is reduced.

The first period includes a plurality of AC periods in which frequencies of AC current supplied to the discharge lamp are different from each other, and the frequency of the AC current decreases in the first period as the AC period provided later in time. It is good also as a structure.
According to this configuration, when the first period and the second period are switched, the fluctuation of the thermal load applied to the electrode can be further increased.

The control unit may be configured to change the length of the second period based on at least one of the detected interelectrode voltage and the driving power.
According to this configuration, it is easy to maintain the shape of the projection of the electrode even when the discharge lamp is deteriorated. Moreover, according to this structure, it is easy to suppress that the thermal load applied to an electrode becomes large excessively.

When the detected voltage between the electrodes is larger than a first predetermined value, or when the driving power supplied to the discharge lamp is smaller than a second predetermined value, the control unit, instead of the second period, The discharge lamp driving unit is controlled to provide a third period, and the third period is supplied to the discharge lamp in a first DC period in which a DC current is supplied to the discharge lamp and in the first DC period. Alternately including second DC periods in which a DC current having a polarity opposite to the polarity of the DC current is supplied to the discharge lamp. The length of the first DC period is greater than the length of the second DC period. The length of the second DC period may be smaller than 0.5 ms.
According to this configuration, when the detected interelectrode voltage is larger than the first predetermined value, or when the driving power supplied to the discharge lamp is smaller than the second predetermined value, the first DC periods having different polarities from each other And a third period having a second DC period. Therefore, when one electrode heats, it can suppress that the temperature of the other electrode falls too much.

One embodiment of the light source device of the present invention is characterized with electric light release you emits light, and the discharge lamp driving apparatus, in that it comprises.

  According to one aspect of the light source device of the present invention, since the discharge lamp driving device is provided, the life of the discharge lamp can be improved.

  One aspect of the projector of the present invention includes the light source device, a light modulation device that modulates light emitted from the light source device according to an image signal, and a projection that projects light modulated by the light modulation device. And an optical system.

  According to one aspect of the projector of the present invention, since the light source device is provided, the life of the discharge lamp can be improved.

One aspect of a discharge lamp driving method of the present invention is a discharge lamp driving method for driving a discharge lamp by supplying a driving current to a discharge lamp having an electrode, the AC having a first frequency in the discharge lamp. A mixing period in which a first period in which current is supplied and a second period in which direct current is supplied to the discharge lamp is alternately provided is provided, and the first frequency includes a plurality of different frequencies, The first period includes a plurality of AC periods in which the first frequency of the AC current supplied to the discharge lamp is different from each other. In the first period, the AC period that is provided later in time corresponds to the AC current. The first frequency is reduced, and each of the first frequencies in the plurality of AC periods is changed based on at least one of the detected interelectrode voltage and the driving power supplied to the discharge lamp. To.
One aspect of a discharge lamp driving method of the present invention is a discharge lamp driving method for driving a discharge lamp by supplying a driving current to a discharge lamp having an electrode, the AC having a first frequency in the discharge lamp. A mixing period in which a first period in which current is supplied and a second period in which direct current is supplied to the discharge lamp is alternately provided is provided, and the first frequency includes a plurality of different frequencies, based on at least one of the driving power supplied to the detected electrostatic inter-electrode voltage and the discharge lamp, and wherein the varying the first frequency.

  According to one aspect of the discharge lamp driving method of the present invention, the life of the discharge lamp can be improved in the same manner as described above.

It is a schematic block diagram of the projector of 1st Embodiment. It is a figure which shows the discharge lamp in 1st Embodiment. It is a block diagram which shows the various components of the projector of 1st Embodiment. It is a circuit diagram of the discharge lamp lighting device of a 1st embodiment. It is a block diagram which shows the example of 1 structure of the control part of 1st Embodiment. It is a figure which shows the mode of the protrusion of the electrode tip of a discharge lamp. It is a figure which shows an example of the drive current waveform of the mixing period in 1st Embodiment. It is a graph which shows an example of the relationship between the lamp voltage and 1st frequency in 1st Embodiment. It is a graph which shows an example of the relationship between the drive electric power and 1st frequency in 1st Embodiment. It is a figure which shows an example of the drive current waveform of the mixing period in 2nd Embodiment. It is a flowchart which shows an example of the control procedure of the discharge lamp drive part by the control part in 2nd Embodiment. It is a schematic diagram which shows the change of the period when a drive current is supplied to the discharge lamp in 3rd Embodiment. It is a figure which shows an example of the drive current waveform of the 4th period in 3rd Embodiment. It is a figure which shows an example of the drive current waveform of the 5th period in 3rd Embodiment. It is a flowchart which shows an example of the control procedure of the discharge lamp drive part by the control part in 3rd Embodiment.

Hereinafter, a projector according to an embodiment of the invention will be described with reference to the drawings.
The scope of the present invention is not limited to the following embodiment, and can be arbitrarily changed within the scope of the technical idea of the present invention. Moreover, in the following drawings, in order to make each structure easy to understand, the actual structure may be different from the scale, number, or the like in each structure.

<First Embodiment>
As shown in FIG. 1, the projector 500 of the present embodiment includes a light source device 200, a collimating lens 305, an illumination optical system 310, a color separation optical system 320, and three liquid crystal light valves (light modulation devices) 330R. , 330G, 330B, a cross dichroic prism 340, and a projection optical system 350 are provided.

  Light emitted from the light source device 200 passes through the collimating lens 305 and enters the illumination optical system 310. The collimating lens 305 collimates the light from the light source device 200.

  The illumination optical system 310 adjusts the illuminance of light emitted from the light source device 200 to be uniform on the liquid crystal light valves 330R, 330G, and 330B. Furthermore, the illumination optical system 310 aligns the polarization direction of the light emitted from the light source device 200 in one direction. The reason is that the light emitted from the light source device 200 is effectively used by the liquid crystal light valves 330R, 330G, and 330B.

  The light whose illuminance distribution and polarization direction are adjusted enters the color separation optical system 320. The color separation optical system 320 separates incident light into three color lights of red light (R), green light (G), and blue light (B). The three color lights are respectively modulated according to the video signal by the liquid crystal light valves 330R, 330G, and 330B associated with the respective color lights. The liquid crystal light valves 330R, 330G, and 330B include liquid crystal panels 560R, 560G, and 560B, which will be described later, and polarizing plates (not shown). The polarizing plates are disposed on the light incident side and the light emitting side of the liquid crystal panels 560R, 560G, and 560B, respectively.

  The three modulated color lights are combined by the cross dichroic prism 340. The combined light enters the projection optical system 350. The projection optical system 350 projects incident light onto the screen 700 (see FIG. 3). As a result, an image is displayed on the screen 700. As each configuration of the collimating lens 305, the illumination optical system 310, the color separation optical system 320, the cross dichroic prism 340, and the projection optical system 350, a well-known configuration can be adopted.

  FIG. 2 is a cross-sectional view showing the configuration of the light source device 200. The light source device 200 includes a light source unit 210 and a discharge lamp lighting device (discharge lamp driving device) 10. FIG. 2 shows a cross-sectional view of the light source unit 210. The light source unit 210 includes a main reflecting mirror 112, a discharge lamp 90, and a sub reflecting mirror 113.

  The discharge lamp lighting device 10 supplies the drive current I to the discharge lamp 90 to light the discharge lamp 90. The main reflecting mirror 112 reflects the light emitted from the discharge lamp 90 in the irradiation direction D. The irradiation direction D is parallel to the optical axis AX of the discharge lamp 90.

  The shape of the discharge lamp 90 is a rod shape extending along the irradiation direction D. One end of the discharge lamp 90 is a first end 90e1, and the other end of the discharge lamp 90 is a second end 90e2. The material of the discharge lamp 90 is a translucent material such as quartz glass, for example. The central portion of the discharge lamp 90 swells in a spherical shape, and the inside is a discharge space 91. The discharge space 91 is filled with a gas that is a discharge medium containing a rare gas, a metal halide, or the like.

  In the discharge space 91, the tips of the first electrode (electrode) 92 and the second electrode (electrode) 93 protrude. The first electrode 92 is disposed on the first end portion 90 e 1 side of the discharge space 91. The second electrode 93 is disposed on the second end 90 e 2 side of the discharge space 91. The shape of the first electrode 92 and the second electrode 93 is a rod shape extending along the optical axis AX. In the discharge space 91, the electrode tip portions of the first electrode 92 and the second electrode 93 are arranged to face each other with a predetermined distance. The material of the first electrode 92 and the second electrode 93 is, for example, a metal such as tungsten.

  A first terminal 536 is provided at the first end 90 e 1 of the discharge lamp 90. The first terminal 536 and the first electrode 92 are electrically connected by a conductive member 534 that penetrates the inside of the discharge lamp 90. Similarly, a second terminal 546 is provided at the second end 90e2 of the discharge lamp 90. The second terminal 546 and the second electrode 93 are electrically connected by a conductive member 544 that penetrates the inside of the discharge lamp 90. The material of the first terminal 536 and the second terminal 546 is, for example, a metal such as tungsten. As a material of the conductive members 534 and 544, for example, a molybdenum foil is used.

  The first terminal 536 and the second terminal 546 are connected to the discharge lamp lighting device 10. The discharge lamp lighting device 10 supplies a driving current I for driving the discharge lamp 90 to the first terminal 536 and the second terminal 546. As a result, arc discharge occurs between the first electrode 92 and the second electrode 93. Light (discharge light) generated by the arc discharge is radiated in all directions from the discharge position, as indicated by the dashed arrows.

  The main reflecting mirror 112 is fixed to the first end 90e1 of the discharge lamp 90 by a fixing member 114. The main reflecting mirror 112 reflects the light traveling toward the opposite side of the irradiation direction D in the discharge light toward the irradiation direction D. The shape of the reflecting surface (the surface on the discharge lamp 90 side) of the main reflecting mirror 112 is not particularly limited as long as the discharge light can be reflected in the irradiation direction D. Parabolic shape may be sufficient. For example, when the shape of the reflecting surface of the main reflecting mirror 112 is a parabolic shape, the main reflecting mirror 112 can convert the discharge light into light substantially parallel to the optical axis AX. Thereby, the collimating lens 305 can be omitted.

  The sub-reflecting mirror 113 is fixed to the second end 90 e 2 side of the discharge lamp 90 by a fixing member 522. The shape of the reflecting surface (surface on the discharge lamp 90 side) of the sub-reflecting mirror 113 is a spherical shape surrounding the portion of the discharge space 91 on the second end 90e2 side. The sub-reflecting mirror 113 reflects the light traveling toward the side opposite to the side on which the main reflecting mirror 112 is disposed in the discharge light toward the main reflecting mirror 112. Thereby, the utilization efficiency of the light radiated | emitted from the discharge space 91 can be improved.

  The material of the fixing members 114 and 522 is not particularly limited as long as it is a heat-resistant material that can withstand the heat generated from the discharge lamp 90, and is, for example, an inorganic adhesive. The method of fixing the arrangement of the main reflecting mirror 112 and the sub reflecting mirror 113 and the discharge lamp 90 is not limited to the method of fixing the main reflecting mirror 112 and the sub reflecting mirror 113 to the discharge lamp 90, and any method can be adopted. . For example, the discharge lamp 90 and the main reflecting mirror 112 may be independently fixed to the housing (not shown) of the projector 500. The same applies to the sub-reflecting mirror 113.

Hereinafter, the circuit configuration of the projector 500 will be described.
FIG. 3 is a diagram illustrating an example of a circuit configuration of the projector 500 according to the present embodiment. In addition to the optical system shown in FIG. 1, the projector 500 includes an image signal conversion unit 510, a DC power supply device 80, liquid crystal panels 560R, 560G, and 560B, an image processing device 570, and a CPU (Central Processing Unit) 580. It is equipped with.

  The image signal conversion unit 510 converts an image signal 502 (such as a luminance-color difference signal or an analog RGB signal) input from the outside into a digital RGB signal having a predetermined word length to generate image signals 512R, 512G, and 512B. This is supplied to the image processing device 570.

  The image processing device 570 performs image processing on each of the three image signals 512R, 512G, and 512B. The image processing device 570 supplies drive signals 572R, 572G, and 572B for driving the liquid crystal panels 560R, 560G, and 560B to the liquid crystal panels 560R, 560G, and 560B, respectively.

  The DC power supply device 80 converts an AC voltage supplied from an external AC power supply 600 into a constant DC voltage. The DC power supply device 80 includes an image signal conversion unit 510 on the secondary side of a transformer (not shown, but included in the DC power supply device 80), an image processing device 570, and a discharge lamp lighting device 10 on the primary side of the transformer. Supply DC voltage.

  The discharge lamp lighting device 10 generates a high voltage between the electrodes of the discharge lamp 90 at the time of startup, and causes a dielectric breakdown to form a discharge path. Thereafter, the discharge lamp lighting device 10 supplies the drive current I for the discharge lamp 90 to maintain the discharge.

  Liquid crystal panels 560R, 560G, and 560B are provided in the liquid crystal light valves 330R, 330G, and 330B, respectively. The liquid crystal panels 560R, 560G, and 560B modulate the transmittance (luminance) of color light incident on the liquid crystal panels 560R, 560G, and 560B via the optical system described above based on the drive signals 572R, 572G, and 572B, respectively. .

  The CPU 580 controls various operations from the start of lighting of the projector 500 to the turning off of the projector 500. For example, in the example of FIG. 3, a lighting command or a lighting command is output to the discharge lamp lighting device 10 via the communication signal 582. The CPU 580 receives lighting information of the discharge lamp 90 from the discharge lamp lighting device 10 via the communication signal 584.

Hereinafter, the configuration of the discharge lamp lighting device 10 will be described.
FIG. 4 is a diagram illustrating an example of a circuit configuration of the discharge lamp lighting device 10.
As shown in FIG. 4, the discharge lamp lighting device 10 includes a power control circuit 20, a polarity inversion circuit 30, a control unit 40, an operation detection unit 60, and an igniter circuit 70.

  The power control circuit 20 generates driving power to be supplied to the discharge lamp 90. In the present embodiment, the power control circuit 20 includes a down chopper circuit that receives the voltage from the DC power supply device 80 as an input, steps down the input voltage, and outputs a DC current Id.

  The power control circuit 20 includes a switch element 21, a diode 22, a coil 23, and a capacitor 24. The switch element 21 is composed of, for example, a transistor. In the present embodiment, one end of the switch element 21 is connected to the positive voltage side of the DC power supply device 80, and the other end is connected to the cathode terminal of the diode 22 and one end of the coil 23.

  One end of a capacitor 24 is connected to the other end of the coil 23, and the other end of the capacitor 24 is connected to the anode terminal of the diode 22 and the negative voltage side of the DC power supply device 80. A current control signal is input to the control terminal of the switch element 21 from a control unit 40 described later, and ON / OFF of the switch element 21 is controlled. For example, a PWM (Pulse Width Modulation) control signal may be used as the current control signal.

  When the switch element 21 is turned on, a current flows through the coil 23 and energy is stored in the coil 23. Thereafter, when the switch element 21 is turned OFF, the energy stored in the coil 23 is released through a path passing through the capacitor 24 and the diode 22. As a result, a direct current Id corresponding to the proportion of time during which the switch element 21 is turned on is generated.

  The polarity inversion circuit 30 inverts the polarity of the direct current Id input from the power control circuit 20 at a predetermined timing. As a result, the polarity inversion circuit 30 generates and outputs a drive current I that is a direct current that lasts for a controlled time, or a drive current I that is an alternating current having an arbitrary frequency. In the present embodiment, the polarity inverting circuit 30 is configured by an inverter bridge circuit (full bridge circuit).

  The polarity inversion circuit 30 includes, for example, a first switch element 31, a second switch element 32, a third switch element 33, and a fourth switch element 34 configured by transistors. In the polarity inversion circuit 30, the first switch element 31 and the second switch element 32 connected in series, and the third switch element 33 and the fourth switch element 34 connected in series are connected in parallel to each other. It has a configuration. The polarity inversion control signal is input from the control unit 40 to the control terminals of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34, respectively. Based on this polarity inversion control signal, the ON / OFF operation of the first switch element 31, the second switch element 32, the third switch element 33, and the fourth switch element 34 is controlled.

  In the polarity inversion circuit 30, the operation of alternately turning on / off the first switch element 31 and the fourth switch element 34, and the second switch element 32 and the third switch element 33 is repeated. Thereby, the polarity of the direct current Id output from the power control circuit 20 is alternately inverted. The polarity inversion circuit 30 is controlled from the common connection point between the first switch element 31 and the second switch element 32 and the common connection point between the third switch element 33 and the fourth switch element 34. A drive current I that is a direct current that continues the same polarity state or a drive current I that is an alternating current having a controlled frequency is generated and output.

  In other words, the polarity inverting circuit 30 is configured such that when the first switch element 31 and the fourth switch element 34 are ON, the second switch element 32 and the third switch element 33 are OFF, When the fourth switch element 34 is OFF, the second switch element 32 and the third switch element 33 are controlled to be ON. Therefore, when the first switch element 31 and the fourth switch element 34 are ON, the drive current I flowing from the one end of the capacitor 24 in the order of the first switch element 31, the discharge lamp 90, and the fourth switch element 34 is generated. To do. When the second switch element 32 and the third switch element 33 are ON, a drive current I that flows from one end of the capacitor 24 in the order of the third switch element 33, the discharge lamp 90, and the second switch element 32 is generated.

  In the present embodiment, the combined portion of the power control circuit 20 and the polarity inversion circuit 30 corresponds to the discharge lamp driving unit 230. That is, the discharge lamp driving unit 230 supplies the driving current I for driving the discharge lamp 90 to the discharge lamp 90.

  The control unit 40 controls the discharge lamp driving unit 230. In the example of FIG. 4, the control unit 40 controls the power control circuit 20 and the polarity inversion circuit 30, thereby maintaining the drive current I with the same polarity, the current value of the drive current I (the power value of the drive power). ), Control parameters such as frequency. The control unit 40 performs polarity reversal control for the polarity reversing circuit 30 to control the holding time during which the drive current I continues at the same polarity, the frequency of the drive current I, and the like according to the polarity reversal timing of the drive current I. The control unit 40 performs current control for controlling the current value of the output direct current Id on the power control circuit 20.

  In the present embodiment, the control unit 40 can execute AC driving, DC driving, and mixing driving. The AC drive is a drive in which an AC current is supplied to the discharge lamp 90. The direct current drive is a drive in which a direct current is supplied to the discharge lamp 90. Mixed drive is drive in which alternating current drive and direct current drive are executed alternately. The drive current waveform of the drive current I supplied to the discharge lamp 90 by each discharge lamp drive will be described in detail later.

  The configuration of the control unit 40 is not particularly limited. In the present embodiment, the control unit 40 includes a system controller 41, a power control circuit controller 42, and a polarity inversion circuit controller 43. Note that a part or all of the control unit 40 may be configured by a semiconductor integrated circuit.

  The system controller 41 controls the power control circuit 20 and the polarity inversion circuit 30 by controlling the power control circuit controller 42 and the polarity inversion circuit controller 43. The system controller 41 may control the power control circuit controller 42 and the polarity inversion circuit controller 43 based on the lamp voltage (interelectrode voltage) Vla and the drive current I detected by the operation detection unit 60.

In the present embodiment, a storage unit 44 is connected to the system controller 41.
The system controller 41 may control the power control circuit 20 and the polarity inversion circuit 30 based on information stored in the storage unit 44. The storage unit 44 may store, for example, information related to drive parameters such as a holding time during which the drive current I continues with the same polarity, a current value of the drive current I, a frequency, a waveform, and a modulation pattern.

  The power control circuit controller 42 controls the power control circuit 20 by outputting a current control signal to the power control circuit 20 based on the control signal from the system controller 41.

  The polarity inversion circuit controller 43 controls the polarity inversion circuit 30 by outputting a polarity inversion control signal to the polarity inversion circuit 30 based on the control signal from the system controller 41.

  The control unit 40 is realized using a dedicated circuit, and can perform the above-described control and various types of control of processing to be described later. On the other hand, for example, the control unit 40 can function as a computer when the CPU executes a control program stored in the storage unit 44, and can perform various controls of these processes.

  FIG. 5 is a diagram for explaining another configuration example of the control unit 40. As shown in FIG. 5, the control unit 40 is configured to function as a current control unit 40-1 that controls the power control circuit 20 and a polarity reversal control unit 40-2 that controls the polarity reversing circuit 30 according to a control program. May be.

  In the example shown in FIG. 4, the control unit 40 is configured as a part of the discharge lamp lighting device 10. On the other hand, the CPU 580 may be configured to bear a part of the function of the control unit 40.

  In the present embodiment, the operation detection unit 60 includes a voltage detection unit that detects the lamp voltage Vla of the discharge lamp 90 and outputs lamp voltage information to the control unit 40. Further, the operation detection unit 60 may include a current detection unit that detects the drive current I and outputs drive current information to the control unit 40. In the present embodiment, the operation detection unit 60 is configured to include a first resistor 61, a second resistor 62, and a third resistor 63.

  In the present embodiment, the voltage detection unit of the operation detection unit 60 detects the lamp voltage Vla in parallel with the discharge lamp 90 using the voltage divided by the first resistor 61 and the second resistor 62 connected in series with each other. . In the present embodiment, the current detection unit detects the drive current I based on the voltage generated in the third resistor 63 connected in series to the discharge lamp 90.

  The igniter circuit 70 operates only when the discharge lamp 90 starts to be lit. The igniter circuit 70 is a high voltage (discharge) necessary for forming a discharge path by dielectric breakdown between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93) at the start of lighting of the discharge lamp 90. A voltage higher than that during normal lighting of the lamp 90) is supplied between the electrodes of the discharge lamp 90 (between the first electrode 92 and the second electrode 93). In the present embodiment, the igniter circuit 70 is connected in parallel with the discharge lamp 90.

  6A and 6B show the tip portions of the first electrode 92 and the second electrode 93. Protrusions 552p and 562p are formed at the tips of the first electrode 92 and the second electrode 93, respectively.

  The discharge generated between the first electrode 92 and the second electrode 93 is mainly generated between the protrusion 552p and the protrusion 562p. When there are the protrusions 552p and 562p as in the present embodiment, the movement of the discharge position (arc position) in the first electrode 92 and the second electrode 93 can be suppressed as compared with the case where there is no protrusion.

  FIG. 6A shows a first polarity state in which the first electrode 92 operates as an anode and the second electrode 93 operates as a cathode. In the first polarity state, electrons move from the second electrode 93 (cathode) to the first electrode 92 (anode) by discharge. Electrons are emitted from the cathode (second electrode 93). Electrons emitted from the cathode (second electrode 93) collide with the tip of the anode (first electrode 92). Heat is generated by this collision, and the temperature of the tip (projection 552p) of the anode (first electrode 92) rises.

  FIG. 6B shows a second polarity state in which the first electrode 92 operates as a cathode and the second electrode 93 operates as an anode. In the second polarity state, electrons move from the first electrode 92 to the second electrode 93, contrary to the first polarity state. As a result, the temperature of the tip (projection 562p) of the second electrode 93 rises.

  Thus, the drive current I is supplied to the discharge lamp 90, so that the temperature of the anode where the electrons collide increases. On the other hand, the temperature of the cathode that emits electrons decreases while the electrons are emitted toward the anode.

  The interelectrode distance between the first electrode 92 and the second electrode 93 increases with the deterioration of the protrusions 552p and 562p. This is because the protrusions 552p and 562p are worn out. As the distance between the electrodes increases, the resistance between the first electrode 92 and the second electrode 93 increases, and the lamp voltage Vla increases. Therefore, by referring to the lamp voltage Vla, it is possible to detect a change in the distance between the electrodes, that is, the degree of deterioration of the discharge lamp 90.

  In addition, since the 1st electrode 92 and the 2nd electrode 93 are the same structures, in the following description, only the 1st electrode 92 may be demonstrated as a representative. In addition, since the protrusion 552p at the tip of the first electrode 92 and the protrusion 562p at the tip of the second electrode 93 have the same configuration, in the following description, only the protrusion 552p may be described as a representative.

  Hereinafter, control of the discharge lamp driving unit 230 by the control unit 40 of the present embodiment will be described. In the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 by mixed driving in which alternating current driving and direct current driving are alternately repeated.

  FIG. 7 is a diagram illustrating an example of a drive current waveform according to the present embodiment. In FIG. 7, the vertical axis indicates the drive current I, and the horizontal axis indicates time T. The drive current I is shown as positive when it is in the first polarity state and negative when it is in the second polarity state.

  As shown in FIG. 7, in the present embodiment, a mixing period PH1 in which a first period (AC driving period) P1 and a second period (DC driving period) P2 are alternately repeated is provided. The mixing period PH1 is a period during which mixing driving is executed. The first period P1 is a period during which AC driving is executed. The second period P2 is a period in which DC driving is executed. The number of first periods P1 and the number of second periods P2 in the mixed period PH1 are not particularly limited.

  The first period P1 is a period in which an alternating current having the first frequency f1 is supplied to the discharge lamp 90. In the present embodiment, the first period P1 includes a first AC period (AC period) P11, a second AC period (AC period) P12, a third AC period (AC period) P13, and a fourth AC period (AC period). ) P14. The first AC period P11, the second AC period P12, the third AC period P13, and the fourth AC period P14 are continuously provided in this order.

  In the present embodiment, the alternating current in the first alternating period P11, the second alternating period P12, the third alternating period P13, and the fourth alternating period P14 is, for example, between the current value Im1 and the current value −Im1. And a rectangular wave alternating current whose polarity is inverted a plurality of times.

  The first frequency f11 in the first AC period P11, the first frequency f12 in the second AC period P12, the first frequency f13 in the third AC period P13, and the first frequency f14 in the fourth AC period P14 are: Different from each other. That is, the first frequency f1 includes a plurality of different frequencies, and the first period P1 has a plurality of AC periods in which the frequencies of the AC current supplied to the discharge lamp 90 are different from each other.

  The first frequency f11, the first frequency f12, the first frequency f13, and the first frequency f14 decrease in this order. That is, in the first period P1, the frequency of the alternating current becomes smaller in the alternating period provided later in time.

  In the present embodiment, the control unit 40 sets the first frequencies f11 to f14 based on both the lamp voltage Vla detected by the voltage detection unit in the operation detection unit 60 and the driving power Wd supplied to the discharge lamp 90. . That is, the control unit 40 sets the first frequencies f11 to f14 based on at least one of the lamp voltage Vla and the driving power Wd. That is, in the present embodiment, the control unit 40 changes the first frequencies f11 to f14 based on at least one of the lamp voltage Vla and the driving power Wd.

  FIG. 8 is a graph showing an example of the relationship between the lamp voltage Vla and the first frequencies f11 to f14. In FIG. 8, the vertical axis represents the first frequency f1, and the horizontal axis represents the lamp voltage Vla. FIG. 8 shows the relationship between the lamp voltage Vla and the first frequencies f11 to f14 when the driving power Wd is a constant value.

  In the example of FIG. 8, the first frequencies f11 to f14 are constant in the range where the value of the lamp voltage Vla is less than the predetermined value Vla1. In the example of FIG. 8, in the range where the value of the lamp voltage Vla is equal to or greater than the predetermined value Vla1, the first frequencies f11 to f14 are set to increase as the lamp voltage Vla increases. In the range where the value of the lamp voltage Vla is equal to or higher than the predetermined value Vla1, the relationship between the first frequencies f11 to f14 and the lamp voltage Vla is expressed by a linear function, for example.

  In the example of FIG. 8, the slope of the change of the first frequency f1 with respect to the lamp voltage Vla in the range where the value of the lamp voltage Vla is equal to or greater than the predetermined value Vla1 is the first frequency f14, the first frequency f13, the first frequency f12, The frequency increases in the order of one frequency f11. That is, as the lamp voltage Vla increases, the value difference between the first frequencies f11 to f14 increases.

  FIG. 9 is a graph illustrating an example of the relationship between the driving power Wd and the first frequencies f11 to f14. In FIG. 9, the vertical axis indicates the first frequency f1, and the horizontal axis indicates the drive power Wd. FIG. 9 shows the relationship between the driving power Wd and the first frequencies f11 to f14 when the lamp voltage Vla is a constant value.

  In the example of FIG. 9, the first frequencies f11 to f14 are set larger as the driving power Wd is smaller. The relationship between the first frequencies f11 to f14 and the driving power Wd is represented by a linear function, for example. In the example of FIG. 9, the slope of the change in the first frequency f1 with respect to the drive power Wd is the same in any of the first frequencies f11 to f14, for example.

  In the present embodiment, the first frequency f1 is set based on both the change in the first frequency f1 with respect to the lamp voltage Vla shown in FIG. 8 and the change in the first frequency f1 with respect to the drive power Wd shown in FIG. The Specifically, for example, the first frequency f1 is obtained by adding or subtracting the change in the first frequency f1 due to the change in the drive power Wd to the value of the first frequency f1 set for the lamp voltage Vla. The value of is set. The value of the first frequency f1 is, for example, between 50 Hz and 50 kHz.

  In the present specification, the first frequency f1 is set to be larger as the lamp voltage Vla is larger, as in the example of FIG. 8, only when the value of the lamp voltage Vla is within a predetermined range. Alternatively, it may be within all the possible ranges of the value of the lamp voltage Vla.

  Further, in the present specification, the first frequency f1 is set to be larger as the driving power Wd is smaller in the entire range where the value of the driving power Wd can be taken as in the example of FIG. Alternatively, the value of the drive power Wd may be only within a predetermined range.

  Further, in the present specification, the first frequency f1 is set to be larger as the lamp voltage Vla is larger, which includes setting the driving frequency Wd in this way. Further, in the present specification, the first frequency f1 is set to be larger as the driving power Wd is smaller, which includes setting in this way when the lamp voltage Vla is constant.

  That is, for example, when the first frequency f1 is set based on both the lamp voltage Vla and the driving power Wd as in the present embodiment, the driving power Wd increases even when the lamp voltage Vla increases. The actual first frequency f1 may be reduced, and even when the drive power Wd is increased, the actual first frequency f1 may be increased by decreasing the lamp voltage Vla.

  In the present embodiment, the start polarity of the first period P1 is, for example, the period provided immediately before, that is, the polarity opposite to the end polarity of the second period P2 in this embodiment. The start polarity is the polarity of the drive current I when a certain period starts. The end polarity is the polarity of the drive current I when a certain period ends.

  Specifically, for example, when the polarity of the direct current supplied to the discharge lamp 90 in the second period P2 provided immediately before the first period P1 is the second polarity, the end polarity of the second period P2 is Since it becomes the 2nd polarity, the start polarity of the 1st period P1 is the 1st polarity. In the present embodiment, the start polarity of the first period P1 is the start polarity of the first AC period P11.

  As shown in FIG. 7, in this embodiment, the length t11 of the first AC period P11, the length t12 of the second AC period P12, the length t13 of the third AC period P13, and the fourth AC period P14. For example, the length t14 is the same. The number of alternating current cycles T1 included in each AC period is set based on both the lamp voltage Vla and the driving power Wd, for example. In this embodiment, the cycle number T1 of the alternating current included in each alternating period is set based on the first frequency f1 set based on both the lamp voltage Vla and the driving power Wd, for example.

  That is, the cycle number T11 in the first AC period P11 shown in FIG. 7 is set based on the first frequency f11. The cycle number T12 of the second AC period P12 is set based on the first frequency f12. The number of cycles T13 of the third AC period P13 is set based on the first frequency f13. The cycle number T14 of the fourth AC period P14 is set based on the first frequency f14. Specifically, for example, a value obtained by multiplying each first frequency f1 by the length of each period is the number of periods.

In the present embodiment, the length t1 of the first period P1, that is, the total length of the lengths t11 to t14 is, for example, not less than 10 ms (milliseconds) and not more than 10 s (seconds). By length t1 of the first period P1 is set in this manner, it can be added suitably heat load to the protrusion 562 p of protrusions 552p and the second electrode 93 of the first electrode 92.

  The second period P2 is a period during which a direct current is supplied to the discharge lamp 90. In the example shown in FIG. 7, in the second period P2, the first polarity drive current I having a constant current value Im1 is supplied to the discharge lamp 90. The polarity of the direct current supplied to the discharge lamp 90 in the second period P2 of the mixing period PH1 is reversed every time the second period P2 is provided.

  That is, in the mixing period PH1, the direct current supplied to the discharge lamp 90 in the second period P2 provided immediately before the first period P1, and the discharge lamp 90 in the second period P2 provided immediately after the first period P1. The polarity of the supplied direct current is different. For example, the polarity of the direct current supplied to the discharge lamp 90 in the second period P2 provided immediately before the first period P1 is the same as the direct current supplied to the discharge lamp 90 in the second period P2 shown in FIG. In the case of the first polarity, the polarity of the direct current supplied to the discharge lamp 90 in the second period P2 provided immediately after the first period P1 is a second polarity opposite to the first polarity. In this case, in the second period P2 provided immediately after the first period P1, the second polarity drive current I having a constant current value −Im1 is supplied to the discharge lamp 90.

  The length t2 of the second period P2 shown in FIG. 7 is larger than the length of the half cycle of the alternating current having the first frequency f11 in the first period P1. The length t2 of the second period P2 is, for example, not less than 10 ms (milliseconds) and not more than 20 ms (milliseconds). By setting the length t <b> 2 of the second period P <b> 2 in this way, a heat load can be suitably applied to the protrusion 552 p of the first electrode 92.

  In the present embodiment, the control unit 40 sets the length t2 of the second period P2 based on both the lamp voltage Vla and the driving power Wd. That is, in the present embodiment, the control unit 40 sets the length t2 of the second period P2 based on at least one of the lamp voltage Vla and the driving power Wd. In other words, in the present embodiment, the control unit 40 changes the length t2 of the second period P2 based on at least one of the lamp voltage Vla and the driving power Wd. For example, the length t2 of the second period P2 is set to be larger as the lamp voltage Vla is larger. For example, the length t2 of the second period P2 is set to be smaller as the driving power Wd is larger.

  The relationship between the length t2 of the second period P2 and the lamp voltage Vla can be expressed by, for example, a linear function when the driving power Wd is constant. The relationship between the length t2 of the second period P2 and the driving power Wd can be expressed by, for example, a linear function when the lamp voltage Vla is constant.

  In the present specification, the length t2 of the second period P2 is set to be larger as the lamp voltage Vla is larger, which means that the value of the lamp voltage Vla is only within a predetermined range. The value of the lamp voltage Vla may be in all possible ranges.

  In the present specification, the length t2 of the second period P2 is set to be smaller as the driving power Wd is larger, which may be that the value of the driving power Wd is only within a predetermined range. It may be within all the possible ranges of the drive power Wd.

  That is, when the lamp voltage Vla is equal to or lower than a predetermined value, for example, the length t2 of the second period P2 may be constant. Further, when the drive power Wd is equal to or less than a predetermined value, for example, the length t2 of the second period P2 may be constant.

  Further, in this specification, the length t2 of the second period P2 is set to be larger as the lamp voltage Vla is larger, which includes setting in this way when the driving power Wd is constant. Further, in this specification, the length t2 of the second period P2 is set to be smaller as the drive power Wd is larger, which includes setting in this way when the lamp voltage Vla is constant.

  That is, for example, when the length t2 of the second period P2 is set based on both the lamp voltage Vla and the driving power Wd as in the present embodiment, the driving power Wd is increased even when the lamp voltage Vla increases. By increasing, the length t2 of the second period P2 provided may be reduced, and even when the drive power Wd increases, the lamp voltage Vla decreases, thereby causing the length t2 of the provided second period P2. Can grow.

  The control by the control unit 40 described above can also be expressed as a discharge lamp driving method. That is, one aspect of the discharge lamp driving method of the present embodiment is a discharge lamp driving method for driving the discharge lamp 90 by supplying the driving current I to the discharge lamp 90 having the first electrode 92 and the second electrode 93. There is a mixing period PH1 in which a first period P1 in which an alternating current having a first frequency f1 is supplied to the discharge lamp 90 and a second period P2 in which a direct current is supplied to the discharge lamp 90 are alternately repeated. The first frequency f1 includes a plurality of different frequencies, and changes the first frequency f1 based on at least one of the detected lamp voltage Vla and the driving power Wd supplied to the discharge lamp 90. Features.

  For example, when the discharge lamp 90 is deteriorated and the lamp voltage Vla is increased, the drive current I supplied to the discharge lamp 90 is decreased, so that the bright spot of arc discharge is likely to be unstable and easily moved. When the bright spot of the arc discharge moves, the melting position and the melting amount in the first electrode 92 change. As a result, the shape of the first electrode 92 becomes unstable and may be easily consumed. Therefore, the life of the discharge lamp 90 may not be sufficiently improved.

  Similarly, when the drive power Wd is small, the drive current I is small. Therefore, the bright spot of arc discharge becomes unstable, and the first electrode 92 may be easily consumed. Therefore, the life of the discharge lamp 90 may not be sufficiently improved.

  With respect to these problems, according to the present embodiment, the control unit 40 sets the first frequency f1 based on at least one of the lamp voltage Vla and the driving power Wd. Therefore, at least one of the above problems can be solved.

  Specifically, when the first frequency f1 is set based on the lamp voltage Vla, arc discharge occurs when the discharge lamp 90 is deteriorated by setting the first frequency f1 higher as the lamp voltage Vla increases. It is easy to stabilize the bright spot. This is due to the following reason.

  When the frequency of the alternating current supplied to the discharge lamp 90 is relatively large, the volume of the melted portion of the protrusion 552p of the first electrode 92 is relatively small. The bright spot of the arc discharge is located on the tip surface where the protrusion 552p is melted and flattened. When the volume of the portion to be melted in the protrusion 552p is small, the area of the tip surface to be planarized is relatively small. Therefore, the region where the arc discharge bright spot moves is reduced, and the position of the arc discharge bright spot can be stabilized.

  Therefore, according to this embodiment, when the discharge lamp 90 deteriorates, it can suppress that the 1st electrode 92 becomes easy to wear out.

  On the other hand, when the first frequency f1 is set based on the driving power Wd, the first frequency f1 is set to be larger as the driving power Wd is smaller. f1 can be made relatively large. Thereby, similarly to the above, the bright spot of the arc discharge can be stabilized, and the first electrode 92 can be prevented from being easily consumed.

  As described above, according to the present embodiment, the consumption of the first electrode 92 can be suppressed, and the life of the discharge lamp 90 can be improved.

  According to the present embodiment, since the first frequency f1 is set based on both the lamp voltage Vla and the driving power Wd, all of the above problems can be solved. Therefore, the life of the discharge lamp 90 can be further improved.

  Further, according to the present embodiment, the first frequency f1 includes a plurality of different frequencies. Therefore, the heat load applied to the first electrode 92 can be varied within the first period P1. Therefore, according to this embodiment, the protrusion 552p of the first electrode 92 can be easily grown.

  Further, according to the present embodiment, in the first period P1, the first frequency f1 becomes smaller in the alternating period provided later in time. That is, in the first period P1, the first frequency f1 is the largest in the first AC period P11 that is provided at the earliest in time. In other words, the first frequency f11 of the alternating current supplied to the discharge lamp 90 in the first alternating period P11 is the largest among the first frequencies f1. As the frequency of the alternating current supplied to the discharge lamp 90 increases, the temperature of the first electrode 92 tends to decrease.

  Therefore, in the mixing period PH1, by providing the first AC period P11 having a large first frequency f1 immediately after the second period P2 having a larger thermal load than the first period P1, the first period heated by the second period P2 is provided. The temperature of the first electrode 92 is easily lowered, and the first electrode 92 is easily stimulated by a change in heat load. As a result, according to the present embodiment, the protrusion 552p is more easily grown.

  Further, according to the present embodiment, the control unit 40 sets the length t2 of the second period P2 based on at least one of the lamp voltage Vla and the driving power Wd. Therefore, by setting the length t2 of the second period P2 to be larger as the lamp voltage Vla is larger, when the discharge lamp 90 is deteriorated, the protrusion 552p is easily melted and the shape of the protrusion 552p is easily maintained. In addition, by setting the length t2 of the second period P2 to be smaller as the driving power Wd is larger, it is possible to suppress the protrusion 552p of the first electrode 92 from being excessively melted, and to easily maintain the shape of the protrusion 552p.

  Further, according to the present embodiment, the polarity of the direct current supplied to the discharge lamp 90 in the second period P2 of the mixing period PH1 is reversed every time the second period P2 is provided. Therefore, in the mixing period PH1, the protrusion 552p of the first electrode 92 and the protrusion 562p of the second electrode 93 can be grown in a balanced manner, and both the shape of the protrusion 552p and the shape of the protrusion 562p can be easily maintained.

  In the present embodiment, the following configurations and methods may be employed.

  In the present embodiment, the mixing period PH1 may be always provided while the discharge lamp 90 is lit, or a plurality of mixing periods PH1 may be provided intermittently with another period interposed therebetween.

  In the present embodiment, the plurality of first frequencies f1 may be provided in any manner. In the present embodiment, for example, in the first period P1, the first frequency f1 may be increased in the alternating period provided later in time.

  In the present embodiment, the number of AC periods included in the first period P1 is not particularly limited. In the present embodiment, the first period P1 may have two or three alternating periods, and may have five or more alternating periods. In the present embodiment, for example, the number of AC periods included in each first period P1 may be different.

  In the present embodiment, the lengths of the AC periods included in the first period P1 may be different from each other. That is, the length t11 of the first AC period P11, the length t12 of the second AC period P12, the length t13 of the third AC period P13, and the length t14 of the fourth AC period P14 are different from each other. It may be.

  In the present embodiment, the control unit 40 may set the first frequency f1 based only on the lamp voltage Vla, or may set the first frequency f1 based only on the driving power Wd.

  In the present embodiment, the control unit 40 may set the length t2 of the second period P2 based only on the lamp voltage Vla, or may set the length t2 of the second period P2 based only on the driving power Wd. It may be set. In the present embodiment, the length t2 of the second period P2 may not change.

  In the present embodiment, the control unit 40 may set the length t2 of the second period P2 based on at least one of the lamp voltage Vla and the driving power Wd every time the second period P2 is provided, When a plurality of mixing periods PH1 are provided, the length t2 of the second period P2 may be set based on at least one of the lamp voltage Vla and the driving power Wd once every time the mixing period PH1 is provided. When the length t2 of the second period P2 is set every time the second period P2 is provided, the length t2 of each second period P2 may be different from each other in one mixed period PH1. On the other hand, when the length t2 of the second period P2 is set once every time the mixed period PH1 is provided, the length t2 of each second period P2 is the same in one mixed period PH1.

  In the present embodiment, when a plurality of mixing periods PH1 are provided, the control unit 40 performs the second operation based on at least one of the lamp voltage Vla and the driving power Wd once every time a predetermined number of mixing periods PH1 are provided. The length t2 of the period P2 may be set.

  In the present embodiment, the control unit 40 may not reverse the polarity of the direct current supplied to the discharge lamp 90 in the second period P2 of the mixing period PH1 every time the second period P2 is provided. That is, in the present embodiment, the second period P2 in which the direct current having the same polarity is supplied to the discharge lamp 90 may be continuously provided twice or more.

Second Embodiment
The second embodiment differs from the first embodiment in that a third period (divided DC drive period) P3 is provided. In addition, about the structure similar to the said embodiment, description may be abbreviate | omitted by attaching | subjecting the same code | symbol suitably.

  In the present embodiment, the control unit 40 can execute divided DC driving in addition to the driving described in the first embodiment. In the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 so that a third period P3, which is a period in which the divided DC driving is executed, is provided. The third period P3 is a period provided instead of the second period P2 under a predetermined condition.

  FIG. 10 is a diagram illustrating an example of a drive current waveform in the third period P3. In FIG. 10, the vertical axis indicates the drive current I, and the horizontal axis indicates time T. The drive current I is shown as positive when it is in the first polarity state and negative when it is in the second polarity state.

  As shown in FIG. 10, in this embodiment, a mixing period PH2 is provided. In the mixed period PH2, the first period P1 and the second period P2 are alternately repeated, or the first period P1 and the third period P3 are alternately repeated. That is, in the mixed period PH2, whether the first period P1 and the second period P2 are alternately repeated or the first period P1 and the third period P3 are alternately repeated according to a predetermined condition. Different.

  In the example of FIG. 10, the case where the first period P1 and the third period P3 are alternately repeated in the mixed period PH2 is shown. When the first period P1 and the second period P2 are alternately repeated in the mixed period PH2, the drive current waveform in the mixed period PH2 is the same as the drive current waveform in the mixed period PH1 of the first embodiment.

  The third period P3 is a period including the first DC period P31 and the second DC period P32 alternately. The first DC period P31 is a period in which a DC current is supplied to the discharge lamp 90. In the example shown in FIG. 10, in the first DC period P31, the first polarity drive current I having a constant current value Im1 is supplied to the discharge lamp 90.

  The second DC period P32 is a period in which a DC current having a polarity opposite to the DC current supplied to the discharge lamp 90 in the polarity of the first DC period P31 is supplied to the discharge lamp 90. That is, in the example shown in FIG. 10, the second polarity drive current I having a constant current value −Im1 is supplied to the discharge lamp 90 in the second DC period P32.

  The polarity of the direct current supplied to the discharge lamp 90 in the first direct current period P31 and the polarity of the direct current supplied to the discharge lamp 90 in the second direct current period P32 are reversed every time the third period P3 is provided. That is, in the third period P3 provided next to the third period P3 shown in FIG. 10, the polarity of the direct current supplied to the discharge lamp 90 in the first direct current period P31 becomes the second polarity, and the second direct current The polarity of the direct current supplied to the discharge lamp 90 in the period P32 is the first polarity.

  The length t31 of the first DC period P31 is longer than the length t32 of the second DC period P32. The length t31 of the first DC period P31 is, for example, not less than 10 times the length t32 of the second DC period P32. By setting the length t31 of the first DC period P31 in this way, it is possible to suitably suppress the temperature of the other electrode from being excessively lowered while appropriately heating one electrode in the third period P3. .

  The length t31 of the first DC period P31 is, for example, not less than 5.0 ms (milliseconds) and not more than 20 ms (milliseconds). The length t32 of the second DC period P32 is smaller than 0.5 ms (milliseconds). The total length t31 of the first DC period P31 in the third period P3 is greater than the length t2 of the second period P2 provided when a predetermined condition is not satisfied.

  The sum of the lengths t31 of the first DC periods P31 in the third period P3 is a length obtained by adding the lengths t31 of all the first DC periods P31 included in the third period P3. In the example of FIG. 10, the third period P3 includes, for example, three first DC periods P31. Therefore, the sum of the lengths t31 of the first DC periods P31 in the third period P3 is a length obtained by adding the lengths t31 of the three first DC periods P31.

  The total length t31 of the first DC period P31 in the third period P3 is, for example, not less than 5.0 ms (milliseconds) and not more than 100 ms (milliseconds). By setting the total length t31 of the first DC period P31 in the third period P3 in this way, the heat load applied to the protrusion 552p of the first electrode 92 can be suitably increased.

  In the following description, the sum of the lengths t31 of the first DC periods P31 in the third period P3 may be simply referred to as the total length of the first DC periods P31.

  The length t31 of the first DC period P31 may be the same or different from each other. In the example of FIG. 10, the length t31 of the first DC period P31 is the same.

  In the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 so that periods alternately repeated in the mixing period PH2 are switched according to a predetermined condition. That is, the control unit 40 controls the discharge lamp driving unit 230 such that the third period P3 is provided instead of the second period P2 according to a predetermined condition. Details will be described below.

  FIG. 11 is a flowchart illustrating an example of control of the control unit 40 in the mixing period PH2. As illustrated in FIG. 11, the control unit 40 starts AC driving (step S12) after starting mixing driving (step S11). Thereby, the first period P1 in the mixing period PH2 is started.

  Next, as described in the first embodiment, the control unit 40 sets the length t2 of the second period P2 in which the DC driving is performed based on the lamp voltage Vla and the driving power Wd (step S13). Then, the control unit 40 determines whether or not the set length t2 of the second period P2 is greater than a predetermined value (step S14). That is, in the present embodiment, the predetermined condition is whether or not the set length t2 of the second period P2 is larger than a predetermined value.

  When the length t2 of the second period P2 is equal to or less than the predetermined value (step S14: NO), the control unit 40 performs DC driving (step S15). Thereby, the second period P2 is started. That is, in this case, the drive current waveform in the mixed period PH2 is a waveform in which the first period P1 and the second period P2 are alternately repeated.

  On the other hand, when the length t2 of the second period P2 is larger than the predetermined value (step S14: YES), the control unit 40 performs the divided DC drive (step S16). Thereby, the third period P3 is started. That is, in this case, the drive current waveform in the mixed period PH2 is a waveform in which the first period P1 and the third period P3 are alternately repeated. The predetermined value in step S14 is, for example, 20 ms (milliseconds).

  As described above, in the present embodiment, when the set length t2 of the second period P2 is larger than the predetermined value, the control unit 40 releases the third period P3 in place of the second period P2. The electric light driving unit 230 is controlled. That is, in the present embodiment, when the length t2 of the second period P2 is set to be larger than a predetermined value, the second period P2 is not provided. Therefore, the length t2 of the provided second period P2 is equal to or less than a predetermined value.

  The total length t31 of the first DC period P31 in the third period P3 shown in FIG. 10 is the same as the set length t2 of the second period P2. That is, when the set length t2 of the second period P2 is larger than the predetermined value, the period during which the direct current is supplied to the discharge lamp 90 is set instead of the second period P2. It is divided into a plurality of first DC periods P31 by t2. Since the third period P3 includes the second DC period P32 in addition to the first DC period P31, the total length of the first DC period P31 is equal to or less than the predetermined length t2 of the set second period P2. It is longer than the length t2 of the second period P2 provided in the case.

  Specifically, for example, when the predetermined value is 20 ms (milliseconds), when the length t2 of the second period P2 is set to be longer than 20 ms (milliseconds) and 40 ms (milliseconds) or less, the control unit 40 divides the second period P2 into two first DC periods P31 and controls the discharge lamp driving unit 230 so that the second DC period P32 is provided between the first DC periods P31. For example, when the length t2 of the second period P2 is set to be greater than 40 ms (milliseconds) and less than or equal to 60 ms (milliseconds), as illustrated in the example illustrated in FIG. P2 is divided into three first DC periods P31, and the discharge lamp driving unit 230 is controlled such that the second DC period P32 is provided between the first DC periods P31.

  In the example of FIG. 11, every time AC driving (first period P1) is performed in the mixing period PH2, next, of DC driving (second period P2) and divided DC driving (third period P3). It is the structure which selects which of these is performed. Therefore, both the second period P2 and the third period P3 may be provided in one mixed period PH2. For example, consider a case where the first period P1 and the second period P2 are alternately repeated in the initial stage of the mixing period PH2. In this case, when the set value of the length t2 of the second period P2 becomes larger than a predetermined value due to the lamp voltage Vla increasing in the middle, the driving current waveform in the mixing period PH2 is changed from the middle to the first period. The driving current waveform is such that P1 and the third period P3 are alternately repeated.

  As described above, in the present embodiment, the control unit 40 determines which of the second period P2 and the third period P3 is provided based on the set length t2 of the second period P2. . In the present embodiment, the length t2 of the second period P2 is set based on both the lamp voltage Vla and the driving power Wd. That is, in the present embodiment, the control unit 40 determines which of the second period P2 and the third period P3 is provided based on both the lamp voltage Vla and the driving power Wd.

  For example, when the second period P2 in which the length t2 is set larger than a predetermined value is provided in the mixing period PH2, the temperature of the electrode opposite to the electrode heated in the second period P2, for example, the second electrode 93 is There is a risk that it will drop too much.

  On the other hand, according to the present embodiment, when the set length t2 of the second period P2 is larger than the predetermined value, it is supplied to the discharge lamp 90 in the first DC period P31 instead of the second period P2. A third period P3 having a second DC period P32 in which a DC current having a polarity opposite to that of the DC current is supplied to the discharge lamp 90 is provided. The total length of the first DC period P31 in the third period P3 is the same as the set length t2 of the second period P2. Therefore, it is possible to suppress the temperature of the second electrode 93 opposite to the first electrode 92 from being excessively lowered while sufficiently heating the electrode heated in the second period P2, for example, the first electrode 92.

  Further, according to the present embodiment, the total length t31 of the first DC period P31 in the third period P3 is not less than 5.0 ms (milliseconds) and not more than 100 ms (milliseconds). Therefore, it is possible to more suitably heat the electrode serving as the anode in the first DC period P31.

  Further, according to the present embodiment, the sum of the lengths t31 of the first DC periods P31 in the third period P3 is the second period provided when the set length t2 of the second period P2 is equal to or less than a predetermined value. It is larger than the length t2 of P2. Therefore, compared with the case where the second period P2 is provided, the electrode on the side serving as the anode in the first DC period P31 can be further heated.

  In the present embodiment, the following configuration may be employed.

  In the present embodiment, when a plurality of mixed periods PH2 are provided, the control unit 40 determines which of the second period P2 and the third period P3 is provided in the mixed period PH2 once every time the mixed period PH2 is provided. May be determined. In this case, in one mixed period PH2, only the first period P1 and the second period P2 are alternately repeated, or only the first period P1 and the third period P3 are alternately repeated. That is, in this case, in one mixed period PH2, only one of the second period P2 and the third period P3 and the first period P1 are provided.

  In the present embodiment, when a plurality of mixing periods PH2 are provided, the control unit 40 performs the second period P2 and the third period P3 in the mixing period PH2 once every time a predetermined number of mixing periods PH2 are provided. Which of these may be provided may be determined.

  In the above description, the control unit 40 determines whether the second period P2 or the third period P3 is based on the length t2 of the second period P2 set according to the lamp voltage Vla and the driving power Wd. Although it was set as the structure which determines which is provided, it is not restricted to this. In the present embodiment, the control unit 40 does not determine whether the length t2 of the second period P2 set according to the lamp voltage Vla and the driving power Wd is greater than a predetermined value, but more directly. In particular, it may be determined which of the second period P2 and the third period P3 is provided based on at least one of the lamp voltage Vla and the driving power Wd.

  In this case, the length t2 of the second period P2 may not change according to the lamp voltage Vla or the driving power Wd. That is, the control unit 40 may control the discharge lamp driving unit 230 so that the third period P3 is provided instead of the second period P2, based on at least one of the lamp voltage Vla and the driving power Wd. More specifically, when the lamp voltage Vla is larger than a predetermined value (first predetermined value) or the driving power Wd is smaller than a predetermined value (second predetermined value), the control unit 40 The discharge lamp driving unit 230 may be controlled so that the third period P3 is provided instead of the two periods P2. That is, in the present embodiment, the predetermined condition is whether or not the lamp voltage Vla is larger than a predetermined value, or whether or not the driving power Wd is smaller than a predetermined value. In this case, for example, the control unit 40 sets the total length t31 of the first DC period P31 in the third period P3 based on at least one of the detected lamp voltage Vla and driving power Wd.

  In the present embodiment, the control unit 40 determines the polarity of the direct current supplied to the discharge lamp 90 in the first direct current period P31 and the polarity of the direct current supplied to the discharge lamp 90 in the second direct current period P32. It is not necessary to invert every time period P3 is provided. That is, in the present embodiment, the polarity of the direct current supplied to the discharge lamp 90 in the first direct current period P31 and the polarity of the direct current supplied to the discharge lamp 90 in the second direct current period P32 are continuously performed twice or more. There may be provided a third period P3 in which are the same.

<Third Embodiment>
The third embodiment is different from the first embodiment in that a fourth period (low frequency AC driving period) P4 and a fifth period (one side driving period) P5 are provided. In addition, about the structure similar to the said embodiment, description may be abbreviate | omitted by attaching | subjecting the same code | symbol suitably.

  In the present embodiment, the control unit 40 can perform low-frequency AC driving and offset driving in addition to the driving described in the first embodiment. The low frequency AC driving is driving in which an AC current having a frequency lower than that of the AC driving AC current is supplied to the discharge lamp 90. The unidirectional drive is a drive in which direct currents having different polarities are alternately supplied to the discharge lamp 90, and the length of the direct current of one polarity is sufficiently longer than the length of the direct current of the other polarity.

  In the present embodiment, the control unit 40, in addition to the mixing period PH1 in which the first period P1 and the second period P2 are alternately repeated, the fourth period P4 in which the low-frequency AC driving is performed, and the offset driving The discharge lamp driving unit 230 is controlled so that a fifth period P5, which is a period in which the is executed, is provided.

  FIG. 12 is a schematic diagram showing a change in a period during which the drive current I is supplied to the discharge lamp 90 in the present embodiment. As shown in FIG. 12, in the present embodiment, the control unit 40 controls the discharge lamp driving unit 230 so that the driving cycle C is repeated. In the present embodiment, the driving cycle C has a first period P1, a second period P2, a fourth period P4, and a fifth period P5. That is, the drive cycle C is executed by the controller 40 performing four drives. The driving cycle C is provided with a mixed period PH1 in which the first period P1 and the second period P2 are alternately repeated. In the present embodiment, a plurality of mixing periods PH1 are provided.

  In the present embodiment, the fourth period P4 is provided between the mixed periods PH1 that are temporally adjacent. For example, the fourth period P4 is provided immediately after the first period P1. For example, the fourth period P4 is provided immediately before the first period P1.

  FIG. 13 is a diagram illustrating an example of a drive current waveform in the fourth period P4. In FIG. 13, the vertical axis represents the drive current I, and the horizontal axis represents time T. The drive current I is shown as positive when it is in the first polarity state and negative when it is in the second polarity state.

  As shown in FIG. 13, the fourth period P4 is a period in which an alternating current having a second frequency f2 smaller than the first frequency f1 is supplied to the discharge lamp 90. That is, the second frequency f2 of the alternating current in the fourth period P4 is smaller than any of the first frequencies f11 to f14. The value of the second frequency f2 is, for example, between 10 Hz and 100 Hz.

  In the fourth period P4, the start polarity is reversed every time it is provided. In the example of FIG. 13, the start polarity of the fourth period P4 is, for example, the first polarity. Therefore, in the fourth period P4 provided after the fourth period P4 shown in FIG. 13, the start polarity is the second polarity.

  For example, the length t4 of the fourth period P4 is larger than the length t2 of the second period P2. The length t4 of the fourth period P4 is not less than the length of 6 cycles of the alternating current having the second frequency f2 and not more than 30 cycles. By setting the length t4 of the fourth period P4 in this way, the shape of the protrusion 552p of the first electrode 92 can be suitably adjusted.

  As shown in FIG. 12, the fifth period P5 is provided between the mixed periods PH1 that are temporally adjacent to each other. For example, the fifth period P5 is provided immediately after the first period P1. For example, the fifth period P5 is provided immediately before the first period P1.

  FIG. 14 is a diagram illustrating an example of a drive current waveform in the fifth period P5. In FIG. 14, the vertical axis indicates the drive current I, and the horizontal axis indicates time T. The drive current I is shown as positive when it is in the first polarity state and negative when it is in the second polarity state.

  As shown in FIG. 14, the fifth period P5 is a period including the third DC period P51 and the fourth DC period P52 alternately. The third DC period P51 is a period during which a DC current is supplied to the discharge lamp 90. In the example shown in FIG. 14, in the third DC period P51, the first polarity drive current I having a constant current value Im1 is supplied to the discharge lamp 90.

  The fourth DC period P52 is a period in which a DC current having a polarity opposite to the polarity of the DC current supplied to the discharge lamp 90 in the third DC period P51 is supplied to the discharge lamp 90. That is, in the example shown in FIG. 14, the second polarity drive current I having a constant current value −Im1 is supplied to the discharge lamp 90 in the fourth DC period P52.

  The polarity of the direct current supplied to the discharge lamp 90 in the third direct current period P51 and the polarity of the direct current supplied to the discharge lamp 90 in the fourth direct current period P52 are reversed every time the fifth period P5 is provided. That is, in the fifth period P5 provided next to the fifth period P5 shown in FIG. 14, the polarity of the DC current supplied to the discharge lamp 90 in the third DC period P51 is the second polarity, and the fourth DC The polarity of the direct current supplied to the discharge lamp 90 in the period P52 is the first polarity.

  The length t51 of the third DC period P51 is greater than the length t52 of the fourth DC period P52. The length t51 of the third DC period P51 is, for example, 10 times or more the length t52 of the fourth DC period P52. By setting the length t51 of the third DC period P51 in this way, it is possible to suitably suppress the temperature of the other electrode from being excessively lowered while appropriately heating one electrode in the fifth period P5. .

  The length t51 of the third DC period P51 is, for example, not less than 5.0 ms (milliseconds) and not more than 20 ms (milliseconds). The length t52 of the fourth DC period P52 is smaller than 0.5 ms (milliseconds).

  The sum of the lengths t51 of the third DC period P51 in the fifth period P5 is larger than the length t2 of the second period P2, and the AC current of the fourth period P4, that is, the half cycle of the AC current having the second frequency f2 Greater than the length of. The total of the lengths t51 of the third DC periods P51 in the fifth period P5 is a length obtained by adding the lengths t51 of all the third DC periods P51 included in the fifth period P5. In the example of FIG. 14, the fifth period P5 includes, for example, four third DC periods P51. Therefore, the sum of the lengths t51 of the third DC periods P51 in the fifth period P5 is a length obtained by adding the lengths t51 of the four third DC periods P51.

  The total length t51 of the third DC period P51 in the fifth period P5 is, for example, not less than 10 ms (milliseconds) and not more than 1.0 s (seconds). By setting the total length t51 of the third DC period P51 in the fifth period P5 in this way, the heat load applied to the protrusion 552p of the first electrode 92 can be suitably increased.

  In the following description, the total of the lengths t51 of the third DC periods P51 in the fifth period P5 may be simply referred to as the total length of the third DC periods P51.

  The length t51 of the third DC period P51 may be the same or different from each other. In the example of FIG. 14, the length t51 of the third DC period P51 is the same.

  In the present embodiment, the control unit 40 sets the total length of the third DC period P51 based on both the lamp voltage Vla and the driving power Wd. That is, in the present embodiment, the control unit 40 sets the total length of the third DC period P51 based on at least one of the lamp voltage Vla and the driving power Wd. In other words, in the present embodiment, the control unit 40 changes the total length of the third DC period P51 based on at least one of the lamp voltage Vla and the driving power Wd. The total length of the third DC period P51 is set to be larger as the lamp voltage Vla is larger, for example. For example, the total length of the third DC period P51 is set to be smaller as the driving power Wd is larger.

  The relationship between the total length of the third DC periods P51 and the lamp voltage Vla can be expressed by, for example, a linear function when the driving power Wd is constant. The relationship between the total length of the third DC periods P51 and the driving power Wd can be expressed by, for example, a linear function when the lamp voltage Vla is constant.

  In the present specification, the total of the length t51 of the third DC period P51 in the fifth period P5 is set to be larger as the lamp voltage Vla is larger. The value of the lamp voltage Vla is only within a predetermined range. It may also be within all possible ranges of the value of the lamp voltage Vla.

  Further, in this specification, the total of the length t51 of the third DC period P51 in the fifth period P5 is set to be smaller as the drive power Wd is larger. The value of the drive power Wd is only within a predetermined range. Or within all possible ranges of the value of the drive power Wd.

  That is, when the lamp voltage Vla is equal to or lower than a predetermined value, for example, the total length of the third DC period P51 may be constant. Further, when the drive power Wd is equal to or less than a predetermined value, for example, the total length of the third DC period P51 may be constant.

  In the present specification, the total of the length t51 of the third DC period P51 in the fifth period P5 is set to be larger as the lamp voltage Vla is larger. This is the case when the driving power Wd is constant. Including being set to In the present specification, the total of the length t51 of the third DC period P51 in the fifth period P5 is set to be smaller as the drive power Wd is larger. This is the case when the lamp voltage Vla is constant. Including being set to

  That is, for example, when the total length of the third DC period P51 is set based on both the lamp voltage Vla and the driving power Wd as in the present embodiment, the driving power Wd even when the lamp voltage Vla increases. May increase the actual total length of the third DC period P51, and even when the drive power Wd increases, the lamp voltage Vla decreases to reduce the total length of the actual third DC period P51. The height can be large.

  The number of third DC periods P51 included in the fifth period P5 is determined based on, for example, the total length of the third DC periods P51. The number of third DC periods P51 is determined so that, for example, the set total length of the third DC periods P51 can be realized within a range in which the length t51 of each third DC period P51 is equal to or less than a predetermined value. It is done. That is, the number of third DC periods P51 included in the fifth period P5 increases, for example, as the total length of the third DC periods P51 increases.

  Specifically, for example, when the predetermined value is set to 20 ms (milliseconds), when the total length of the third DC period P51 is greater than 20 ms (milliseconds) and not more than 40 ms (milliseconds), the fifth The number of third DC periods P51 included in the period P5 is two. Further, when the total length of the third DC periods P51 is greater than 40 ms (milliseconds) and not more than 60 ms (milliseconds), the number of third DC periods P51 included in the fifth period P5 is three.

  In the example shown in FIG. 14, the number of third DC periods P51 included in the fifth period P5 is four. That is, for example, when the predetermined value is set to 20 ms (milliseconds), the total length of the third DC period P51 is greater than 60 ms (milliseconds) and not more than 80 ms (milliseconds).

  By setting as described above, the total length of the set third DC periods P51 can be realized while setting the length t51 of each third DC period P51 to be a predetermined value (20 ms) or less.

  As described above, in the present embodiment, the fourth period P4 and the fifth period P5 are provided between the mixed periods PH1 that are temporally adjacent to each other. In the present embodiment, the fourth period P4 and the fifth period P5 are periodically provided along a certain pattern. Details will be described below.

  FIG. 15 is a flowchart illustrating an example of control in the drive cycle C by the control unit 40 of the present embodiment. As shown in FIG. 15, when the control unit 40 starts the driving cycle C (step S21), the control unit 40 first executes mixing driving (step S22). Thereby, the mixing period PH1 is started. Then, the control unit 40 determines whether or not the first predetermined time has elapsed since the drive cycle C was started (step S23).

  Here, the first predetermined time is a time from the time when the driving cycle C is started to the first predetermined time. In the present embodiment, a plurality of first predetermined times are set at equal intervals. Therefore, a plurality of first predetermined times are provided in the present embodiment.

  Specifically, for example, in the present embodiment, the predetermined time is set every 30 s (seconds). That is, the first predetermined time is, for example, a time that is 30 s (seconds), 60 s (seconds), or 90 s (seconds) with the time point when the driving cycle C is started as a base point. That is, the first predetermined time is, for example, 30 s (seconds), 60 s (seconds), or 90 s (seconds). Immediately after starting the driving cycle C, the first predetermined time is set to an initial value (30 s).

  When the first predetermined time has not elapsed since the drive cycle C was started (step S23: NO), the control unit 40 continues the mixing drive. On the other hand, when the first predetermined time has elapsed since the drive cycle C was started (step S23: YES), the control unit 40 determines whether or not the second predetermined time has elapsed since the drive cycle C was started. (Step S24).

  Here, the second predetermined time is a time from the start of the driving cycle C to the second predetermined time. The second predetermined time is, for example, a time of 90 s (seconds) with the time point when the driving cycle C is started as a base point. That is, the second predetermined time is, for example, 90 s (seconds). The second predetermined time is larger than the initial value (for example, 30 s) of the first predetermined time.

  When the second predetermined time has not elapsed since the start of the driving cycle C (step S24: NO), the control unit 40 performs the offset driving (step S25). Thereby, the fifth period P5 is started. After the fifth period P5 ends, the control unit 40 sets the first predetermined time to the next value (60 s) (step S26), and executes the mixing drive again (step S22).

  On the other hand, when the second predetermined time has elapsed since the drive cycle C was started (step S24: YES), the control unit 40 performs low-frequency AC driving (step S27). Thereby, the fourth period P4 is started. After the fourth period P4 ends, the controller 40 ends the driving cycle C (step S28) and starts the next driving cycle C (step S21).

  As described above, for example, when the first first predetermined time (30 s) has elapsed since the drive cycle C started, and when the second first predetermined time (60 s) has elapsed since the drive cycle C started. In such a case, the offset driving is executed, and the fifth period P5 is provided.

  On the other hand, when the third first predetermined time (90 s) has elapsed since the start of the driving cycle C, since the second predetermined time (90 s) has also elapsed, low-frequency AC driving is performed, Four periods P4 are provided.

  Thus, the fourth period P4 and the fifth period P5 are periodically provided along a certain pattern. That is, in the present embodiment, the control unit 40 is configured so that one of the fourth period P4 and the fifth period P5 is provided every first predetermined interval, in the above example, every 30 s (seconds), and The discharge lamp driving unit 230 is controlled so that the fourth period P4 is provided every second predetermined interval, in the above example, every 90 s (seconds). The second predetermined interval is greater than the first predetermined interval.

  In the above example, after the fifth period P5 is provided every 30 s (seconds), the fourth period P4 is provided. That is, two fifth periods P5 are provided from when the fourth period P4 is provided to when the next fourth period P4 is provided. The fifth period P5 is provided for the polarity of the DC current supplied to the discharge lamp 90 in the third DC period P51 in the fifth period P5 and the polarity of the DC current supplied to the discharge lamp 90 in the fourth DC period P52. Invert every time. Therefore, in the two fifth periods P5 provided between the fourth periods P4 that are temporally adjacent to each other, the polarities of the drive currents I supplied to the discharge lamp 90 are opposite to each other.

  In other words, in the present embodiment, the control unit 40 has the third DC period P51 in which the first polarity DC current is supplied to the discharge lamp 90 and the second polarity DC in the second predetermined interval in which the fourth period P4 is provided. A fifth period P5 alternately including fourth DC periods P52 in which current is supplied to the discharge lamp 90, a third DC period P51 in which a second polarity DC current is supplied to the discharge lamp 90, and a first polarity DC The discharge lamp driving unit 230 is controlled so as to provide two fifth periods P5, which are fifth periods P5 alternately including fourth DC periods P52 in which current is supplied to the discharge lamp 90. In other words, these two fifth periods P5 are provided in a period sandwiched between the fourth periods P4 that are temporally adjacent.

  According to the present embodiment, in addition to the mixing period PH1 in which the first period P1 in which the alternating current is supplied to the discharge lamp 90 and the second period P2 in which the direct current is supplied to the discharge lamp 90 are alternately repeated, A period P4 and a fifth period P5 are provided. In the fourth period P4, an alternating current having a second frequency f2 smaller than the first frequency f1 of the alternating current in the first period P1 is supplied to the discharge lamp 90. Therefore, the thermal load applied to the first electrode 92 in the fourth period P4 is larger than the thermal load applied to the first electrode 92 in the first period P1.

  In the fifth period P5, a third DC period P51 and a fourth DC period P52 are provided. The length t51 of the third DC period P51 is greater than the length t52 of the fourth DC period P52, and the length t52 of the fourth DC period P52 is less than 0.5 ms (milliseconds). Therefore, in the fifth period P5, the electrode that becomes the anode in the third DC period P51 can be heated. In the following description, it is assumed that the heated electrode is, for example, the first electrode 92.

  Further, the total length of the third DC period P51 is larger than the length t2 of the second period P2, and is longer than the half cycle length of the AC current in the fourth period P4. Therefore, the thermal load applied to the first electrode 92 heated in the fifth period P5 is larger than the thermal load applied to the first electrode 92 heated in the second period P2.

  Thus, in the fourth period P4 and the fifth period P5, the thermal load applied to the first electrode 92 is greater than that in the first period P1 or the second period P2. Therefore, by periodically providing the fourth period P4 and the fifth period P5, the thermal load applied to the first electrode 92 can be changed more greatly than in the case of only the mixing period PH1. Thereby, according to this embodiment, the shape of the protrusion 552p can be more easily maintained, and the life of the discharge lamp 90 can be further improved.

  The fifth period P5 includes a fourth DC period P52 in which a DC current having a polarity opposite to the DC current supplied to the discharge lamp 90 in the third DC period P51 is supplied to the discharge lamp 90. It can suppress that the temperature of the 2nd electrode 93 on the opposite side to the 1st electrode 92 heated in the period P5 falls too much. For example, if the temperature of the second electrode 93 is too low, when the second electrode 93 is heated and melted, it is difficult to raise the temperature of the second electrode 93 and the protrusion 562p of the second electrode 93 may be difficult to melt. There is.

  In addition, since the length t52 of the fourth DC period P52 is smaller than 0.5 ms (milliseconds), the temperature of the first electrode 92 is unlikely to decrease during the fourth DC period P52. Therefore, it is easy to heat the first electrode 92 suitably by the third DC period P51.

  Further, in the fourth period P4 and the fifth period P5, the thermal load applied to the first electrode 92 is likely to increase in the fifth period P5. Therefore, for example, if the period in which the fifth period P5 is periodically provided continues for a long time, the protrusion 552p of the first electrode 92 may be excessively melted.

  On the other hand, according to the present embodiment, in addition to the fifth period P5, by periodically providing the fourth period P4 in which the thermal load applied to the first electrode 92 is likely to be smaller than in the fifth period P5. In the fifth period P5, the protrusion 552p can be prevented from being excessively melted, and the shape of the protrusion 552p can be adjusted.

  Further, according to the present embodiment, the fifth period P5 is provided between the mixed periods PH1 that are temporally adjacent. Therefore, it is easy to appropriately provide the fifth period P5 in which the heat load applied to the first electrode 92 is relatively large. Therefore, according to this embodiment, the shape of the protrusion 552p can be more easily maintained, and the life of the discharge lamp 90 can be further improved.

  Further, in the first period P1 and the second period P2, the heat load applied to the first electrode 92 is likely to be smaller in the first period P1. According to the present embodiment, the fifth period P5 is provided immediately after the first period P1. For this reason, it is easier to increase the fluctuation of the thermal load due to the transition from the mixing period PH1 to the fifth period P5. Therefore, it is easier to grow the protrusion 552p of the first electrode 92.

  Further, according to the present embodiment, the fourth period P4 is provided between the mixed periods PH1 that are temporally adjacent. Therefore, it is easy to appropriately provide the fourth period P4 in which the heat load applied to the first electrode 92 is relatively large. Therefore, according to this embodiment, the shape of the protrusion 552p can be more easily maintained, and the life of the discharge lamp 90 can be further improved.

  According to the present embodiment, the fourth period P4 is provided immediately after the first period P1. In the first period P1 and the fourth period P4, an alternating current is supplied to the discharge lamp 90. Therefore, when the period during which the alternating current is supplied to the discharge lamp 90 continues and changes from the first period P1 to the fourth period P4, the frequency is changed from the first frequency f1 to the second frequency f2 smaller than the first frequency f1. It becomes. Thereby, compared with the case where the fourth period P4 is provided immediately after the second period P2 in which the direct current is supplied to the discharge lamp 90, the variation in the thermal load applied to the first electrode 92 can be easily moderated. In the period P4, the shape of the protrusion 552p of the first electrode 92 can be easily adjusted.

  In addition, according to the present embodiment, one of the fourth period P4 and the fifth period P5 is provided at each first predetermined interval. Therefore, the thermal load applied to the protrusion 552p of the first electrode 92 can be periodically increased, and the shape of the protrusion 552p can be easily maintained suitably.

  Further, according to the present embodiment, the fourth period P4 is provided for each second predetermined interval that is larger than the first predetermined interval. Therefore, it is easy to make the frequency at which the fourth period P4 is provided lower than the frequency at which the fifth period P5 is provided. Accordingly, the fourth period P4 can be provided after the fifth period P5 is provided several times. Therefore, the shape of the protrusion 552p can be adjusted while the protrusion 552p of the first electrode 92 is suitably melted.

  Further, according to the present embodiment, the polarity of the direct current supplied to the discharge lamp 90 in the third direct current period P51 and the polarity of the direct current supplied to the discharge lamp 90 in the fourth direct current period P52 are the fifth period P5. Whenever is provided, it is reversed. Therefore, it is easy to heat the first electrode 92 and the second electrode 93 alternately in a balanced manner. Therefore, according to the present embodiment, the protrusion 552p of the first electrode 92 and the protrusion 562p of the second electrode 93 can be grown in a balanced manner, and both the shape of the protrusion 552p and the shape of the protrusion 562p can be easily maintained.

  Moreover, according to the present embodiment, the start polarity is inverted every time the fourth period P4 is provided. Therefore, even in the case where the polarity of the direct current supplied to the discharge lamp 90 is reversed in the second period P2 and the fifth period P5, the fourth period P4 changes from the period immediately before the fourth period P4, and the fourth period P4. The polarity can be reversed when the period changes from the period P4 to the immediately following period. That is, the polarity of the drive current I supplied to the discharge lamp 90 can be reversed before and after the period changes. Therefore, according to this embodiment, the protrusion 552p of the first electrode 92 and the protrusion 562p of the second electrode 93 can be grown in a more balanced manner, and the shape of the protrusion 552p and the shape of the protrusion 562p can be more easily maintained.

  For example, when the discharge lamp 90 is deteriorated, the protrusion 552p of the first electrode 92 is hardly melted, and the shape of the protrusion 552p is difficult to maintain. Therefore, even in the fifth period P5 in which the heat load applied to the first electrode 92 is relatively large, the shape of the protrusion 552p may not be sufficiently maintained.

  For example, when the driving power Wd supplied to the discharge lamp 90 is relatively large, the thermal load applied to the first electrode 92 tends to increase. Therefore, the provision of the fifth period P5 may cause an excessive increase in the thermal load applied to the first electrode 92.

  With respect to these problems, according to the present embodiment, the control unit 40 sets the total length of the third DC period P51 based on at least one of the lamp voltage Vla and the driving power Wd. Therefore, at least one of the above problems can be solved.

  Specifically, when the total length of the third DC period P51 is set based on the lamp voltage Vla, the total length of the third DC period P51 is set larger as the lamp voltage Vla increases. When the lamp 90 is deteriorated, the heat load applied to the first electrode 92 in the fifth period P5 can be further increased. Thereby, when the discharge lamp 90 is deteriorated, the protrusion 552p of the first electrode 92 is easily melted suitably by the fifth period P5, and the shape of the protrusion 552p is easily maintained.

  On the other hand, when the total length of the third DC period P51 is set based on the drive power Wd, the drive power Wd is set by decreasing the total length of the third DC period P51 as the drive power Wd increases. When it is relatively large, the heat load applied to the first electrode 92 in the fifth period P5 can be reduced. Thereby, it can suppress that the processus | protrusion 552p of the 1st electrode 92 is fuse | melted excessively, and it is easy to maintain the shape of the processus | protrusion 552p.

  According to the present embodiment, since the total length of the third DC period P51 is set based on both the lamp voltage Vla and the driving power Wd, all of the above problems can be solved.

  Further, for example, in the fifth period P5, if the difference (ratio) between the length t51 of the third DC period P51 and the length t52 of the fourth DC period P52 is small, the first electrode 92 of the third DC period P51 The difference between the temperature increase width and the temperature decrease width of the first electrode 92 in the fourth DC period P52 is small. Therefore, it is difficult to increase the temperature of the first electrode 92 in the fifth period P5. As a result, the thermal load applied to the first electrode 92 in the fifth period P5 cannot be sufficiently increased, and the protrusion 552p may not be sufficiently melted.

  On the other hand, according to the present embodiment, the length t51 of the third DC period P51 is 10 times or more the length t52 of the fourth DC period P52. Therefore, the temperature increase width of the first electrode 92 in the third DC period P51 can be sufficiently larger than the temperature decrease width of the first electrode 92 in the fourth DC period P52. Thereby, according to the present embodiment, it is possible to suitably apply a heat load to the first electrode 92 in the fifth period P5, and it is easier to maintain the shape of the protrusion 552p.

  Further, according to the present embodiment, the total length t51 of the third DC period P51 in the fifth period P5 is not less than 10 ms (milliseconds) and not more than 1.0 s (seconds). Therefore, it is easy to sufficiently increase the heat load applied to the first electrode 92 in the fifth period P5, and it is easier to maintain the shape of the protrusion 552p.

  Further, according to the present embodiment, the length t4 of the fourth period P4 is equal to or longer than six periods of the AC current having the second frequency f2 supplied to the discharge lamp 90 in the fourth period P4, and is 30 periods. It is below the length. Therefore, the shape of the protrusion 552p of the first electrode 92 can be more suitably arranged in the fourth period P4.

  In the present embodiment, the following configurations and methods may be employed.

  In the present embodiment, the first period P1, the second period P2, the fourth period P4, and the fifth period P5 may be provided in any manner within the range in which the mixed period PH1 is provided. For example, in the above description, only the case where the first period P1 and the second period P2 are provided alternately and continuously in the mixed period PH1 has been described. However, the present invention is not limited to this and may be provided separately from each other. Good. Further, for example, the second period P2 and the fourth period P4, the second period P2 and the fifth period P5, and the fourth period P4 and the fifth period P5 may be provided continuously.

  In the present embodiment, the fourth period P4 and the fifth period P5 provided between the temporally adjacent mixed periods PH1 may be provided immediately after the second period P2.

  In the above description, the end polarity of a certain period and the start polarity of a period provided immediately after a certain period are different from each other, but the present invention is not limited to this. In the present embodiment, the end polarity of a certain period and the start polarity of a period provided immediately after a certain period may be the same.

  In the present embodiment, the control unit 40 may set the total length of the third DC period P51 in the fifth period P5 based only on the lamp voltage Vla, or the fifth period based only on the driving power Wd. The total length of the third DC period P51 in P5 may be set. In the present embodiment, the total length of the third DC period P51 in the fifth period P5 may not change.

  Further, in the present embodiment, the control unit 40 applies at least one of the lamp voltage Vla and the driving power Wd in the same manner as the total length of the third DC period P51 in the fifth period P5 and the length t2 of the second period P2. Based on this, the length t4 of the fourth period P4 may be set. That is, in the present embodiment, the control unit 40 may change the length t4 of the fourth period P4 based on at least one of the lamp voltage Vla and the driving power Wd.

  In the present embodiment, the mixing period PH2 of the second embodiment may be provided instead of the mixing period PH1. In this case, the total length of the third DC period P51 in the fifth period P5 is greater than the total length of the first DC period P31 in the third period P3 of the mixing period PH2.

  In the present embodiment, the control unit 40 may not reverse the start polarity of the fourth period P4 every time the fourth period P4 is provided. That is, in the present embodiment, the fourth period P4 in which the alternating current having the second frequency f2 having the same start polarity is supplied to the discharge lamp 90 may be continuously provided twice or more.

  In the present embodiment, the control unit 40 sets the polarity of the DC current supplied to the discharge lamp 90 in the third DC period P51 and the polarity of the DC current supplied to the discharge lamp 90 in the fourth DC period P52. It is not necessary to invert every time period P5 is provided. That is, in the present embodiment, the polarity of the DC current supplied to the discharge lamp 90 in the third DC period P51 and the polarity of the DC current supplied to the discharge lamp 90 in the fourth DC period P52 are consecutively performed twice or more. May be provided in the fifth period P5.

  In each of the above embodiments, an example in which the present invention is applied to a transmissive projector has been described. However, the present invention can also be applied to a reflective projector. Here, the “transmission type” means that a liquid crystal light valve including a liquid crystal panel or the like is a type that transmits light. “Reflective type” means that the liquid crystal light valve reflects light. The light modulation device is not limited to a liquid crystal panel or the like, and may be a light modulation device using a micromirror, for example.

  Further, in each of the above embodiments, the example of the projector 500 using the three liquid crystal panels 560R, 560G, and 560B (liquid crystal light valves 330R, 330G, and 330B) has been described. However, the present invention only includes one liquid crystal panel. The present invention is also applicable to a projector that uses four or more liquid crystal panels.

  Further, the configurations of the first to third embodiments described above can be combined as appropriate within a range that does not contradict each other.

  DESCRIPTION OF SYMBOLS 10 ... Discharge lamp lighting device (discharge lamp drive device), 40 ... Control part, 90 ... Discharge lamp, 92 ... 1st electrode (electrode), 93 ... 2nd electrode (electrode), 200 ... Light source device, 230 ... Discharge lamp Drive unit, 330R, 330G, 330B ... Liquid crystal light valve (light modulation device), 350 ... Projection optical system, 500 ... Projector, 502, 512R, 512G, 512B ... Image signal, f1, f11, f12, f13, f14 ... No. 1 frequency, I ... drive current, P1 ... first period, P11 ... first AC period (AC period), P12 ... second AC period (AC period), P13 ... third AC period (AC period), P14 ... first 4 AC periods (AC periods), P2 ... 2nd period, P3 ... 3rd period, P31 ... 1st DC period, P32 ... 2nd DC period, PH1, PH2 ... mixing period, Vla ... lamp voltage (interelectrode voltage) , Wd Driving power

Claims (10)

A discharge lamp driving section for supplying a driving current to a discharge lamp having an electrode;
A control unit for controlling the discharge lamp driving unit;
A voltage detector for detecting a voltage between the electrodes of the discharge lamp;
With
The control unit is provided with a mixing period in which a first period in which an alternating current having a first frequency is supplied to the discharge lamp and a second period in which a direct current is supplied to the discharge lamp are alternately repeated. Control the discharge lamp driving unit,
The first frequency includes a plurality of different frequencies,
The first period has a plurality of AC periods in which the first frequency of the AC current supplied to the discharge lamp is different from each other,
In the first period, the first frequency of the alternating current becomes smaller in the alternating period provided later in time,
The controller changes each of the first frequencies in the plurality of AC periods based on at least one of the detected interelectrode voltage and driving power supplied to the discharge lamp. Electric light drive device. A discharge lamp driving section for supplying a driving current to a discharge lamp having an electrode;
A control unit for controlling the discharge lamp driving unit;
A voltage detector for detecting a voltage between the electrodes of the discharge lamp;
With
The control unit is provided with a mixing period in which a first period in which an alternating current having a first frequency is supplied to the discharge lamp and a second period in which a direct current is supplied to the discharge lamp are alternately repeated. Control the discharge lamp driving unit,
The first frequency includes a plurality of different frequencies,
The control unit changes the first frequency based on at least one of the detected inter-electrode voltage and driving power supplied to the discharge lamp,
When the detected voltage between the electrodes is larger than a first predetermined value, or when the driving power supplied to the discharge lamp is smaller than a second predetermined value, the control unit may replace the second period. And controlling the discharge lamp driving unit to provide a third period,
The third period includes a first direct current period in which a direct current is supplied to the discharge lamp, and a direct current having a polarity opposite to the polarity of the direct current supplied to the discharge lamp in the first direct current period. Alternately including second DC periods supplied to the discharge lamp,
The length of the first DC period is greater than the length of the second DC period,
The discharge lamp driving device according to claim 1, wherein a length of the second DC period is smaller than 0.5 ms. The first period has a plurality of AC periods in which frequencies of AC current supplied to the discharge lamp are different from each other,
3. The discharge lamp driving device according to claim 2 , wherein in the first period, the frequency of the alternating current decreases as the alternating period provided later in time. The control unit sets the first frequency based on the detected interelectrode voltage,
4. The discharge lamp driving device according to claim 1, wherein the first frequency is set to be larger as the inter-electrode voltage is larger. 5. The control unit sets the first frequency based on the driving power,
The discharge lamp driving device according to any one of claims 1 to 4, wherein the first frequency is set to be larger as the driving power is smaller. The discharge lamp driving according to any one of claims 1 to 5 , wherein the control unit changes the length of the second period based on at least one of the detected inter-electrode voltage and the driving power. apparatus. A discharge lamp that emits light;
The discharge lamp driving device according to any one of claims 1 to 6,
A light source device comprising: The light source device according to claim 7;
A light modulation device that modulates light emitted from the light source device according to an image signal;
A projection optical system that projects the light modulated by the light modulation device;
A projector comprising: A discharge lamp driving method for driving a discharge lamp by supplying a driving current to a discharge lamp having an electrode,
A mixing period is provided in which a first period in which an alternating current having a first frequency is supplied to the discharge lamp and a second period in which a direct current is supplied to the discharge lamp are alternately provided;
The first frequency includes a plurality of different frequencies,
The first period has a plurality of AC periods in which the first frequency of the AC current supplied to the discharge lamp is different from each other,
In the first period, the first frequency of the alternating current becomes smaller in the alternating period provided later in time,
A discharge lamp driving method comprising: changing each of the first frequencies in a plurality of the AC periods based on at least one of a detected interelectrode voltage and driving power supplied to the discharge lamp. A discharge lamp driving method for driving a discharge lamp by supplying a driving current to a discharge lamp having an electrode,
A mixing period is provided in which a first period in which an alternating current having a first frequency is supplied to the discharge lamp and a second period in which a direct current is supplied to the discharge lamp are alternately provided;
The first frequency includes a plurality of different frequencies,
Based on at least one of the detected interelectrode voltage and the driving power supplied to the discharge lamp, the first frequency is changed,
When the detected voltage between the electrodes is larger than a first predetermined value, or when the driving power supplied to the discharge lamp is smaller than a second predetermined value, a third period is used instead of the second period. Driving the discharge lamp as provided,
The third period includes a first direct current period in which a direct current is supplied to the discharge lamp, and a direct current having a polarity opposite to the polarity of the direct current supplied to the discharge lamp in the first direct current period. Alternately including second DC periods supplied to the discharge lamp,
The length of the first DC period is greater than the length of the second DC period,
The discharge lamp driving method according to claim 1, wherein the length of the second DC period is smaller than 0.5 ms.

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