JP2013098147A - Discharge lamp lighting device, projector and method for driving discharge lamp - Google Patents

Abstract

Disclosed is a discharge lamp lighting device and a projector capable of suppressing electrode deterioration of a discharge lamp and increasing a power variable width.
A first DC drive process and a first AC drive process are alternately performed in a first section, and a second DC drive process and a second AC drive process are alternately performed in a second section. In the first DC drive process, control is performed to supply a first DC current composed of the first polarity component starting from the first polarity, and in the first AC drive process, the first AC component is repeated with the first polarity component and the second polarity component. Control for supplying current, control for supplying a second DC current composed of a second polarity component starting from the second polarity in the second DC drive processing, and first polarity component and second polarity component in the second AC drive processing If the predetermined condition is satisfied, the length of at least one of the period for performing the first DC driving process and the period for performing the second DC driving process is set. Change it to be shorter.
[Selection] Figure 3

Description

  The present invention relates to a discharge lamp lighting device, a projector, a discharge lamp driving method, and the like.

  As a light source of a projector, a discharge lamp (discharge lamp) such as a high-pressure mercury lamp or a metal halide lamp is used. In these discharge lamps, the shape of the electrode changes due to a decrease in meltability due to the consumption of the electrode due to the discharge or the progress of crystallization of the electrode as the cumulative lighting time elapses. In addition, if a plurality of protrusions grow at the electrode tip part or the irregular consumption of the electrode body part proceeds, the arc starting point moves and the arc length (distance between the electrodes) changes. These phenomena are undesirable because they cause a reduction in luminance and flickering of the discharge lamp, and shorten the life of the discharge lamp.

  As a method for solving this problem, a discharge lamp lighting device (Patent Document 1) that drives a discharge lamp using alternating currents having different frequencies is known. There is also known a discharge lamp lighting device (Patent Document 2) that supplies a drive current obtained by intermittently inserting a direct current into a high frequency alternating current to a discharge lamp.

JP 2006-59790 A Japanese Patent Laid-Open No. 1-112698

Recent projectors often turn on the discharge lamp with multiple operating powers, and generally have a function to switch between the high-brightness mode and the low-brightness mode. The purpose is to reduce. Therefore, in recent years, it is desired to further reduce the operating power in the low luminance mode, that is, to increase the variable range of the operating power. However, a discharge lamp that is steadily lit has a so-called arc discharge with thermionic emission between a pair of electrodes. Therefore, in a low-brightness mode with low operating power, the temperature of the electrodes decreases and flicker is reduced. The situation is likely to occur. Further, when the distance between the electrodes is increased due to the deterioration of the electrodes, the temperature at the tip of the electrode is lowered, and thus noticeable flicker is generated.
In order to cope with such a problem, the discharge lamp is simply driven using alternating currents having different frequencies as in Patent Document 1, or the direct current is intermittently applied to high-frequency alternating current as in Patent Document 2. Even if the inserted drive current is supplied to the discharge lamp, it does not correspond to the operating power, so it may cause flicker early in the low brightness mode, or conversely in the high brightness mode. There is a possibility that electrode consumption will be accelerated.

  The present invention has been made in view of the above problems. According to some embodiments of the present invention, the flickering in the low luminance mode is suppressed and the high luminance is controlled in order to control the molten state and shape of the protrusion formed on the electrode tip of the discharge lamp with respect to the operating power. It is possible to provide a discharge lamp lighting device, a discharge lamp lighting device control method, and a projector that suppress electrode consumption in the mode and have a wide variable operating power.

  A discharge lamp lighting device according to one aspect of the present invention includes a discharge lamp driving unit that supplies a driving current to the discharge lamp and drives the discharge lamp, and a control unit that controls the discharge lamp driving unit, The control unit alternately performs a first DC driving process and a first AC driving process in a first section, and performs a second DC driving process and a second AC driving process in a second section different from the first section. In the first DC driving process, the first DC driving process performs control to supply a first DC current composed of a first polarity component starting from the first polarity as the driving current, and in the first AC driving process, Control is performed to supply a first alternating current that repeats a first polarity component and a second polarity component as a driving current, and the second direct current driving process includes a second polarity component starting from the second polarity as the driving current. The second DC current to be supplied is controlled, In the second AC driving process, a control is performed to supply a second AC current that repeats the first polarity component and the second polarity component as the driving current, and when a predetermined condition is satisfied, the first DC current is processed. The length of at least one of the period for performing the driving process and the period for performing the second DC driving process is changed to be short.

  The first direct current may be composed of a plurality of current pulses of the first polarity component, and the second direct current may be composed of a plurality of current pulses of the second polarity component.

  According to this discharge lamp lighting device, when a predetermined condition is satisfied, in order to change the length of at least one of the period of performing the first DC driving process and the period of performing the second DC driving process to shorten, By controlling the melting area in the case of the anode and the cooling time in the case of the cathode, the flicker is suppressed while maintaining the optimal shape of the protrusion formed on the tip of the electrode.

  In this discharge lamp lighting device, when the predetermined condition is satisfied, the control unit has an average value of at least one frequency of a period in which the first AC driving process is performed and a period in which the second AC driving process is performed. May be raised.

  According to this discharge lamp lighting device, the average value of at least one of the period during which the first AC driving process is performed and the period during which the second AC driving process is performed is changed so as to increase when a predetermined condition is satisfied. Thus, the alternating time of the polarity in the AC drive processing period can be shortened, so that flicker can be suppressed while keeping the shape of the protrusion formed at the tip of the electrode optimal.

  In this discharge lamp lighting device, the control unit increases the length of at least one of the period for performing the first AC driving process and the period for performing the second AC driving process when the predetermined condition is satisfied. It may be changed so as to.

  According to this discharge lamp lighting device, the length of at least one of the period for performing the first AC driving process and the period for performing the second AC driving process is changed so as to increase when a predetermined condition is satisfied. By reducing the ratio of the DC driving process period to the AC driving process period and reducing the melting area of the protrusion formed on the tip of the electrode, the flicker can be suppressed while keeping the protrusion shape optimal. it can.

  In this discharge lamp lighting device, the predetermined condition may be that a signal for reducing the operating power of the discharge lamp by a predetermined value or more is received from the outside.

  According to this discharge lamp lighting device, when the discharge lamp lighting device receives a signal for changing the operating power from an external interface or the like, the period during which the first DC driving process is performed and the second DC driving process are performed. The length of at least one of the periods to be performed is changed to be shortened, and the average value of the frequency of at least one of the period for performing the first AC driving process and the period for performing the second AC driving process is increased. In order to change the length of at least one of the period during which the AC driving process is performed and the period during which the second AC driving process is performed so as to increase when a predetermined condition is satisfied, the luminance is reduced when the operating power is reduced. In addition to suppressing flicker in the mode, it is possible to suppress electrode consumption in the high luminance mode.

  In this discharge lamp lighting device, the predetermined condition may be a case where a lighting voltage at a steady time of the discharge lamp rises to a predetermined value or more.

  According to this discharge lamp lighting device, when the electrode of the discharge lamp deteriorates and the voltage during steady lighting rises to a predetermined value or more, when the control is performed to keep the average power generally performed in a projector or the like constant. Since the current value decreases, flicker is more likely to occur. Therefore, a first AC driving process is performed in which at least one of the period during which the discharge lamp driving device performs the first DC driving process and the period during which the second DC driving process is performed is shortened. Increasing the average value of the frequency of at least one of the period and the period of performing the second AC drive process, and further, at least one length of the period of performing the first AC drive process and the period of performing the second AC drive process, Since the length is changed so as to be longer when a predetermined condition is satisfied, flickering in the low luminance mode can be suppressed and electrode consumption in the high luminance mode can be suppressed when the driving voltage decreases.

  In this discharge lamp lighting device, the predetermined condition may be a case where a lighting current in a steady state of the discharge lamp decreases to a predetermined value or less.

  According to this discharge lamp lighting device, when control is performed to keep the average power generally performed in a projector or the like, when the discharge lamp electrode deteriorates and the drive voltage rises, the current value is a predetermined value. The flicker is more likely to occur. Therefore, a first AC driving process is performed in which at least one of the period during which the discharge lamp driving device performs the first DC driving process and the period during which the second DC driving process is performed is shortened. Increasing the average value of the frequency of at least one of the period and the period of performing the second AC drive process, and further, at least one length of the period of performing the first AC drive process and the period of performing the second AC drive process, Since the length is changed so as to be longer when a predetermined condition is satisfied, flickering in the low luminance mode can be suppressed when the driving current is reduced, and electrode consumption in the high luminance mode can be suppressed.

  The projector which is one aspect of the present invention includes any one of these discharge lamp lighting devices.

  According to this projector, it is possible to suppress flicker while keeping the shape of the protrusion formed at the tip of the electrode optimal.

  The discharge lamp driving method according to one aspect of the present invention alternately performs the first DC driving process and the first AC driving process in the first section, and the second section in the second section different from the first section. A direct current drive process and a second alternating current drive process are alternately performed. In the first direct current drive process, control is performed to supply a first direct current composed of a first polarity component starting from the first polarity as the drive current. In the first AC drive process, control is performed to supply a first AC current that repeats a first polarity component and a second polarity component as the drive current. In the second DC drive process, the first AC current is used as the drive current. Control is performed to supply a second DC current composed of a second polarity component starting from two polarities, and in the second AC driving process, a second polarity component is repeated that repeats the first polarity component and the second polarity component as the driving current. Control to supply alternating current, If certain conditions are met, varied to shorten the length of at least one of the period of performing the first DC driving processing period and the second DC driving processing performed.

  According to this discharge lamp driving method, when a predetermined condition is satisfied, at least one of the period for performing the first DC driving process and the period for performing the second DC driving process is changed to be shortened. The protrusion formed at the tip of the electrode suppresses flicker while maintaining the optimal protrusion shape by controlling the melted area at the time of anode and the cooling time at the time of cathode.

  In this discharge lamp lighting method, when the predetermined condition is satisfied, the frequency is changed so as to increase the frequency of at least one of the period for performing the first AC driving process and the period for performing the second AC driving process. May be.

  According to this discharge lamp lighting method, the average value of the frequency of at least one of the period in which the first AC driving process is performed and the period in which the second AC driving process is performed is changed so as to increase when a predetermined condition is satisfied. Thus, the alternating time of the polarity in the AC drive processing period can be shortened, so that flicker can be suppressed while keeping the shape of the protrusion formed at the tip of the electrode optimal.

  In this discharge lamp lighting method, when the predetermined condition is satisfied, a change is made to increase the length of at least one of the period for performing the first AC driving process and the period for performing the second AC driving process. You may let them.

  According to this discharge lamp lighting method, the length of at least one of the period in which the first AC driving process is performed and the period in which the second AC driving process is performed is changed so as to increase when a predetermined condition is satisfied. By reducing the ratio of the DC driving process period to the AC driving process period and reducing the melting area of the protrusion formed on the tip of the electrode, the flicker can be suppressed while keeping the protrusion shape optimal. it can.

1 is an explanatory diagram showing a projector as an embodiment of the present invention. Explanatory drawing which shows the structure of the light source device as one Example of this invention. The example of the circuit diagram of the discharge lamp lighting device as one Example of this invention. The figure for demonstrating the structure of the control part as one Example of this invention. FIGS. 5A to 5D are explanatory diagrams showing the relationship between the polarity of the drive current supplied to the discharge lamp and the temperature of the electrodes. 6A and 6B are diagrams for explaining the first section and the second section in the first embodiment of the present invention. FIG. 7A shows an example of the waveform of the drive current I in the first section in the first embodiment of the present invention, and FIG. 7B shows the waveform of the drive current I in the second section of the first embodiment of the present invention. The timing chart which shows an example. FIG. 8A shows a waveform example of the drive current I obtained by changing the period of the DC drive process in the first section in the first embodiment of the present invention, and FIG. 8B shows the waveform in the first embodiment of the present invention. The timing chart which shows the example of a waveform of the drive current I which changed the period of the DC drive process in 2 area. FIG. 9A shows a waveform example of the drive current I obtained by changing the frequency of the AC drive processing in the first section in the second embodiment of the present invention, and FIG. 9B shows the waveform in the second embodiment of the present invention. The timing chart which shows the waveform of the drive current I which changed the frequency and the frequency | count of the period of the alternating current drive process in 1 area. The flowchart which shows the example of control of the discharge lamp lighting device of 3rd Embodiment of this invention. 1 is a diagram illustrating an example of a circuit configuration of a projector as an embodiment of the present invention.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present invention.

1. Optical System of Projector FIG. 1 is an explanatory diagram showing a projector 500 as a first embodiment of the invention. The projector 500 includes a light source device 200, a collimating lens 305, an illumination optical system 310, a color separation optical system 320, three liquid crystal light valves 330R, 330G, and 330B, a cross dichroic prism 340, and a projection optical system 350. And have.

  The light source device 200 includes a light source unit 210 and a discharge lamp lighting device 10. The light source unit 210 includes a main reflecting mirror 112, a sub reflecting mirror 50, and a discharge lamp 90. The discharge lamp lighting device 10 supplies power 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. Light from the light source unit 210 passes through the collimating lens 305 and enters the illumination optical system 310. The collimating lens 305 collimates the light from the light source unit 210.

  The illumination optical system 310 makes the illuminance of light from the light source device 200 uniform in the liquid crystal light valves 330R, 330G, and 330B. The illumination optical system 310 aligns the polarization direction of light from the light source device 200 in one direction. This is because the light 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 (R), green (G), and blue (B). The three color lights are respectively modulated by the liquid crystal light valves 330R, 330G, and 330B associated with the respective colors. The liquid crystal light valves 330R, 330G, and 330B include liquid crystal panels 560R, 560G, and 560B and polarizing plates that are disposed on the light incident side and the emission side of the liquid crystal panels 560R, 560G, and 560B, respectively. The modulated three 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 a screen (not shown). Thereby, an image is displayed on the screen.

  Note that various well-known configurations can be adopted as the configurations 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.

FIG. 2 is an explanatory diagram 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 10. In the drawing, a cross-sectional view of the light source unit 210 is shown. The light source unit 210 includes a main reflecting mirror 112, a discharge lamp 90, and a sub reflecting mirror 50.
The shape of the discharge lamp 90 is a rod shape extending along the irradiation direction D from the first end 90e1 to the second end 90e2. The material of the discharge lamp 90 is a translucent material such as quartz glass, for example. A central portion of the discharge lamp 90 swells in a spherical shape, and a discharge space 91 is formed therein. The discharge space 91 is filled with a gas that is a discharge medium containing a rare gas, a metal halide, mercury, or the like.

  In the discharge space 91, two electrodes (first electrode 92 and second electrode 93) protrude from the discharge lamp 90. The first electrode 92 is disposed on the first end 90 e 1 side of the discharge space 91, and 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 (also referred to as “discharge ends”) of the respective electrodes 192 and 93 face each other at 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 passes through the inside of the discharge lamp 90. Similarly, a second terminal 546 is provided at the second end 90 e 2 of the discharge lamp 90. The second terminal 546 and the second electrode 93 are electrically connected by a conductive member 544 that passes through the inside of the discharge lamp 90. The material of each terminal (the first terminal 536 and the second terminal 546) is, for example, a metal such as tungsten. Further, as each of the conductive members 534 and 544, for example, a molybdenum foil is used.
These terminals (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 an alternating current to these terminals 536 and 546. As a result, Arc discharge occurs between the two electrodes (the first electrode 92 and the second electrode 93) The light (discharge light) generated by the arc discharge is directed in all directions from the discharge position, as indicated by the dashed arrows. Radiated.

  The main reflecting mirror 112 is fixed to the first end 90 e 1 of the discharge lamp 90 by a fixing member 114. The shape of the reflecting surface (the surface on the discharge lamp 90 side) of the main reflecting mirror 112 is a spheroid shape. The main reflecting mirror 112 reflects the discharge light in the irradiation direction D. The shape of the reflecting surface of the main reflecting mirror 112 is not limited to the spheroid shape, and various shapes that reflect the discharge light toward the irradiation direction D can be employed. For example, a rotating parabolic shape may be adopted. In this case, the main reflecting mirror 112 can convert the discharge light into light substantially parallel to the optical axis AX. Therefore, the collimating lens 305 can be omitted.

  The sub-reflecting mirror 50 is fixed to the second end 90 e 2 side of the discharge lamp 90 by a fixing member 522. The shape of the reflective surface (surface on the discharge lamp 90 side) of the sub-reflecting mirror 50 is a spherical shape that surrounds the second end 90e2 side of the discharge space 91. The sub-reflecting mirror 50 reflects 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.

  As a material for the fixing members 114 and 522, any heat-resistant material (for example, an inorganic adhesive) that can withstand the heat generated by the discharge lamp 90 can be used. Further, the method of fixing the arrangement of the main reflecting mirror 112 and the sub-reflecting mirror 50 and the discharge lamp 90 is not limited to the method of fixing the main reflecting mirror 112 and the sub-reflecting mirror 50 to the discharge lamp 90, and any method can be used. It can be adopted. For example, the discharge lamp 90 and the main reflecting mirror 112 may be independently fixed to a housing (not shown) of the projector. The same applies to the sub-reflecting mirror 50.

2. 1. Discharge lamp lighting device according to first embodiment (1) Configuration of discharge lamp lighting device FIG. 3 is an example of a circuit diagram of a discharge lamp lighting device according to the present embodiment.

  The discharge lamp lighting device 10 includes a power control circuit 20. 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 DC power supply 80 and steps down the input voltage to output a DC current Id.

  The power control circuit 20 can be configured to include a switch element 21, a diode 22, a coil 23, and a capacitor 24. The switch element 21 can be 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 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 80. A current control signal is input from the control unit 40 to the control terminal of the switch element 21 to control ON / OFF of the switch element 21. For example, a PWM (Pulse Width Modulation) control signal may be used as the current control signal.

  Here, 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 discharge lamp lighting device 10 includes a polarity inversion circuit 30. The polarity inversion circuit 30 receives the direct current Id output from the power control circuit 20 and reverses the polarity at a given timing, so that the polarity inversion circuit 30 can be a direct current that lasts for a controlled time or has an arbitrary frequency. The drive current I is generated and output. 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, first to fourth switch elements 31 to 34 such as transistors, and the first and second switch elements 31 and 32 connected in series and the first switch elements 31 and 32 connected in series. The third and fourth switch elements 33 and 34 are connected in parallel to each other. Polarity inversion control signals are input from the control unit 40 to the control terminals of the first to fourth switch elements 31 to 34, respectively, and ON / OFF of the first to fourth switch elements 31 to 34 is controlled.

  The polarity inverting circuit 30 is configured to output direct current output from the power control circuit 20 by alternately turning on and off the first and fourth switch elements 31 and 34 and the second and third switch elements 32 and 33 alternately. The polarity of the current Id is alternately inverted and continues for a controlled time from the common connection point of the first and second switch elements 31 and 32 and the common connection point of the third and fourth switch elements 33 and 34. A drive current I that is a direct current or an alternating current having an arbitrary frequency is generated and output.

  That is, when the first and fourth switch elements 31 and 34 are ON, the second and third switch elements 32 and 33 are turned OFF, and when the first and fourth switch elements 31 and 34 are OFF, the second and third switch elements 31 and 34 are OFF. The third switch elements 32 and 33 are controlled to be turned on. Therefore, when the first and fourth switch elements 31 and 34 are ON, a drive current I that flows from 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. Further, when the second and third switch elements 32 and 33 are turned on, a drive current I flowing from the 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 power control circuit 20 and the polarity inversion circuit 30 are combined to correspond to the discharge lamp driving unit.

  The discharge lamp lighting device 10 includes a control unit 40. The control unit 40 controls the power control circuit 20 and the polarity inversion circuit 30 to control the holding time during which the drive current I continues with the same polarity, the current value of the drive current I, the frequency, and the like. The control unit 40 performs polarity reversal control for controlling the holding time for the drive current I to remain the same polarity, the frequency of the drive current I, and the like based on the polarity reversal timing of the drive current I with respect to the polarity reversal circuit 30. Further, the control unit 40 performs current control for controlling the current value of the output direct current Id to the power control circuit 20.

  Although 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 reversing circuit 30 by controlling the power control circuit controller 42 and the polarity reversing circuit controller 43. The system controller 41 controls the power control circuit controller 42 and the polarity inversion circuit controller 43 based on the drive voltage Vla and the drive current I detected at the time of steady lighting by a voltage detector 60 provided inside the discharge lamp lighting device 10 described later. May be.

  In the present embodiment, the system controller 41 includes a storage unit 44. The storage unit 44 may be provided independently of 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 information on 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.

  Note that the control unit 40 can be realized by a dedicated circuit to perform the above-described control and various kinds of control of processing to be described later. For example, a control in which a CPU (Central Processing Unit) is stored in the storage unit 44 or the like. It is also possible to function as a computer by executing the program and to perform various controls of these processes. That is, as shown in FIG. 4, the control unit 40 functions as current control means 40-1 for controlling the power control circuit 20 and polarity reversal control means 40-2 for controlling the polarity reversal circuit 30 according to the control program. You may comprise.

  The discharge lamp lighting device 10 may include an operation detection unit. The operation detection unit includes, for example, a voltage detection unit 60 that detects the drive voltage Vla during steady lighting of the discharge lamp 90 and outputs drive voltage information, and a current detection unit that detects the drive current I and outputs drive current information. May be included. In the present embodiment, the voltage detection unit 60 includes first and second resistors 61 and 62.

The voltage detector 60 corresponds to an operation detector that detects the state of the first electrode 92 and the second electrode 93 of the discharge lamp 90 in the present invention. That is, since the drive voltage Vla serves as an index of the distance between the tips of the first electrode 92 and the second electrode 93, the voltage detector 60 detects the drive voltage Vla as a value representing the degree of deterioration of the electrodes.
In the present embodiment, the voltage detection unit 60 detects the drive voltage Vla by the voltage divided by the first and second resistors 61 and 62 connected in series with each other in parallel with the discharge lamp 90. 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 discharge lamp lighting device 10 may include an igniter circuit 70. The igniter circuit 70 operates only at the start of lighting of the discharge lamp 90. At the start of lighting of the discharge lamp 90, the igniter circuit 70 breaks down the electrodes of the discharge lamp 90 and forms a discharge path to form a discharge path. A voltage higher than that during normal lighting) is supplied between the electrodes of the discharge lamp 90. In the present embodiment, the igniter circuit 70 is connected in parallel with the discharge lamp 90.

  5A to 5D are explanatory diagrams showing the relationship between the polarity of the drive current supplied to the discharge lamp 90 and the electrode temperature. 5A and 5B show the operating states of the two first electrodes 92 and the second electrode 93. FIG. In the figure, tip portions of two electrodes (first electrode 92 and second electrode 93) are shown. Protrusions 552p and 562p are provided at the tips of the first electrode 92 and the second electrode 93, respectively. Discharge occurs between these protrusions 552p and 562p. In the present embodiment, the movement of the discharge position (arc position) in each electrode (first electrode 92, second electrode 93) can be suppressed as compared with the case where there is no protrusion. However, such protrusions may be omitted.

  FIG. 5A shows a first polarity state P1 in which the first electrode 92 operates as an anode and the second electrode 93 operates as a cathode. In the first polarity state P1, 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. 5B shows a second polarity state P2 in which the first electrode 92 operates as a cathode and the second electrode 93 operates as an anode. In the second polarity state P2, electrons move from the first electrode 92 to the second electrode 93, contrary to the first polarity state P1. As a result, the temperature of the tip (projection 562p) of the second electrode 93 rises.

  Thus, the temperature of the electrode at the anode tends to be higher than the temperature of the electrode at the cathode. Here, the continued high state of the temperature of one electrode compared to the other electrode can cause various problems. For example, when the tip of the high temperature electrode melts excessively, unintended electrode deformation may occur. As a result, the arc length may deviate from an appropriate value. Moreover, when the melting | fusing of the front-end | tip of a low-temperature electrode is inadequate, the fine unevenness | corrugation produced at the front-end | tip may remain without melting. Similarly, when the tip of the low temperature electrode is insufficiently melted, the protrusion is exposed to a halfway temperature and flattened. As a result, a phenomenon called so-called arc jump or flicker may occur.

  As a technique for suppressing such inconvenience, AC driving in which the polarity of each electrode is repeatedly changed can be used. FIG. 5C is a timing chart showing an example of the drive current I supplied to the discharge lamp 90 (FIG. 2). The horizontal axis indicates time T, and the vertical axis indicates the current value of the drive current I. The drive current I indicates the current flowing through the discharge lamp 90. A positive value indicates the first polarity state P1, and a negative value indicates the second polarity state P2. In the example shown in FIG. 5C, a rectangular wave alternating current is used. Then, the first polarity state P1 and the second polarity state P2 are alternately repeated. Here, the first polarity section Tp indicates the time that the first polarity state P1 continues, and the second polarity section Tn indicates the time that the second polarity state P2 continues. The average current value in the first polarity section Tp is Im1, and the average current value in the second polarity section Tn is -Im2. The frequency of the drive current I suitable for driving the discharge lamp 90 can be determined experimentally according to the characteristics of the discharge lamp 90 (for example, a single value or a plurality of values in the range of 30 Hz to 1 kHz are adopted). ) Other values Im1, −Im2, Tp, and Tn can be determined experimentally in the same manner.

  FIG. 5D is a timing chart showing the temperature change of the first electrode 92. The horizontal axis represents time T, and the vertical axis represents temperature H. In the first polarity state P1, the temperature H of the first electrode 92 increases, and in the second polarity state P2, the temperature H of the first electrode 92 decreases. Further, since the first polarity state P1 and the second polarity state P2 state are repeated, the temperature H periodically changes between the minimum value Hmin and the maximum value Hmax. Although illustration is omitted, the temperature of the second electrode 93 changes in a phase opposite to the temperature H of the first electrode 92. That is, in the first polarity state P1, the temperature of the second electrode 93 decreases, and in the second polarity state P2, the temperature of the second electrode 93 increases.

  In the first polarity state P1, the tip of the first electrode 92 (projection 552p) is melted, so that the tip of the first electrode 92 (projection 552p) is smooth. Thereby, the movement of the discharge position in the 1st electrode 92 can be suppressed. In addition, since the temperature at the tip of the second electrode 93 (projection 562p) falls, excessive melting of the second electrode 93 (projection 562p) is suppressed. Thereby, unintended electrode deformation can be suppressed. In the second polarity state P2, the positions of the first electrode 92 and the second electrode 93 are reversed. Accordingly, by repeating the two states P1 and P2, problems in each of the two electrodes (first electrode 92 and second electrode 93) can be suppressed.

  Here, when the waveform of the current I is symmetric, that is, when the waveform of the current I satisfies the condition “| Im1 | = | −Im2 |, Tp = Tn”, two electrodes (first electrode 92 , The condition of the supplied power is the same between the second electrodes 93). Therefore, it is estimated that the temperature difference between the two electrodes (the first electrode 92 and the second electrode 93) becomes small. However, even when driving with such a symmetric current waveform is continued, the first electrode 92 and the second electrode 93 are consumed due to heat accompanying arc discharge, and the deformation of the protrusions 552p and 562p is generally performed. Will progress. When the protrusions 552p and 562p are further deformed and further flattened, the luminescent spot of the discharge becomes unstable, so that flicker is likely to occur, and the image quality is disturbed on the irradiation screen of the projector.

  When an alternating current having a relatively low frequency is supplied, the electrode is heated too much over a wide range when the anode is used (an arc spot (a hot spot on the electrode surface due to arc discharge) becomes large). Accordingly, the shape of the electrode collapses due to excessive melting, and at the same time, scattering of the electrode material increases. Conversely, if the electrode is too cold (the arc spot is small), the tip of the electrode cannot be sufficiently melted and the tip cannot be returned smoothly. In addition, when supplying a low frequency, the period of exposure to particle collision becomes longer while being a halfway at the cathode. That is, the tip of the electrode is easily deformed by these factors. On the other hand, when AC driving is performed at a high frequency, since the arc spot becomes small, only weak protrusions are formed, and the electrode protrusions that become arc luminescent spots are unclear, so that a plurality of electrode protrusions are formed. An arc jump is likely to occur between the protrusions. Therefore, if a uniform energy supply state is continued with respect to the electrode, the tip of the electrode (protrusions 552p and 562p) is deformed into an unintended shape or a flicker phenomenon is likely to occur.

  Further, recent projectors generally have a high luminance mode and a low luminance mode in many cases. In the low luminance mode in which the power supplied to the discharge lamp 90 is lower than that in the high luminance mode in which the rated power is supplied to the discharge lamp 90, the temperature during discharge of the two electrodes (first electrode 92 and second electrode 93) is lower. Therefore, the discharge tends to be difficult to stabilize, and flicker is more likely to occur.

  Further, when the discharge lamp 90 is used for a long time, the first electrode 92 and the second electrode 93 are consumed, and the distance between the two electrodes (arc length) is increased, the voltage during steady lighting (drive voltage Vla) is increased. To rise. In the case of a constant power operation generally used in a projector, as the drive voltage Vla of the discharge lamp 90 increases, the current value when the discharge lamp 90 is turned on decreases, and flicker is likely to occur. Become.

(2) Control Example of Discharge Lamp Lighting Device Next, a specific example of control of the discharge lamp lighting device 10 according to the first embodiment will be described.
The control unit 40 operates the igniter circuit 70 immediately after the lighting of the discharge lamp 90 and breaks the insulation between the electrodes of the discharge lamp 90 to form a discharge path. When the discharge path is formed, the control unit 40 stops the operation of the igniter circuit 70, and controls the power control circuit 20 and the polarity reversing circuit 30 under the driving conditions for starting lighting for a predetermined period of time. In the meantime, a driving current for starting is supplied. After that, when the discharge lamp 90 can be driven with a constant power, the control unit 40 causes the power control circuit 20 and the polarity inversion circuit 30 to supply predetermined power to the discharge lamp 90 according to the driving conditions during steady lighting. Control.

  The controller 40 of the discharge lamp lighting device 10 according to the first embodiment performs the first DC driving process D1 (first DC driving process) and the first AC driving process A1 (first AC driving) in the first section during steady lighting. Process) are alternately performed, and the second DC driving process D2 (second DC driving process) and the second AC driving process A2 (second AC driving process) are alternately performed in a second section different from the first section. .

  6A and 6B are diagrams for explaining the first section and the second section during steady lighting.

  In the example illustrated in FIG. 6A, the control unit 40 performs a first section in which the first DC driving process D1 and the first AC driving process A1 are alternately performed, a second DC driving process D2, and a second AC driving process. The discharge lamp driving unit is controlled so that second sections alternately performing A2 appear alternately.

  In the example shown in FIG. 6A, in the first section, the first DC drive process D1 and the first AC drive process A1 start with the first DC drive process D1 and end with the first AC drive process A1. And alternately. Similarly, in the second section, the second DC driving process D2 and the second AC driving process A2 are alternately performed so as to start with the second DC driving process D2 and end with the second AC driving process A2.

  The control unit 40 may control the discharge lamp driving unit so that a third section different from the first section and the second section appears. For example, in the example shown in FIG. 6B, the control unit 40 sets the discharge lamp driving unit so that the third section in which the third AC driving process A3 is performed appears between the first section and the second section. I have control.

  In the first DC driving process D1, the control unit 40 performs control to supply a first DC current including a first polarity component starting from the first polarity as the driving current I. In the first AC driving process A1, As the drive current I, control is performed to supply a first alternating current that repeats the first polarity component and the second polarity component at the first frequency.

  In the second DC driving process D2, the control unit 40 performs control to supply a second DC current including the second polarity component starting from the second polarity as the driving current I, and in the second AC driving process A2, As the drive current I, control is performed to supply a second alternating current that repeats the first polarity component and the second polarity component at the second frequency.

  For example, in the example shown in FIGS. 6A and 6B, the first frequency in the first AC driving process A1 and the second frequency in the second AC driving process A2 may be the same.

  For example, in the example shown in FIG. 6B, in the third AC driving process A3, the control unit 40 uses the first polarity component and the first frequency as the driving current I at a third frequency different from the first frequency and the second frequency. You may perform control which supplies the 3rd alternating current which repeats a bipolar component.

  FIG. 7A shows a waveform example of the drive current I in the first section of the high luminance mode in which the rated power is supplied to the discharge lamp 90 during steady lighting, and FIG. 7B shows the rated power during steady lighting. 6 is a timing chart showing a waveform example of a drive current I in a second section of a high luminance mode supplied to the discharge lamp 90. 7A and 7B, the first polarity drive current I is a positive value, and the second polarity drive current I is a negative value.

  In the example shown in FIG. 7A, the control unit 40 performs the first DC driving process D1 during the period from time t0 to time t1, and the first AC driving process A1 during the period from time t1 to time t2. The first DC driving process D1 is performed during the period from time t2 to time t3, and the first AC driving process A1 is performed during the period from time t3 to time t4.

  In the example shown in FIG. 7A, in the first DC drive process D1, the control unit 40 has the same polarity (the first polarity) over a period longer than ½ cycle of the drive current I in the first AC drive process A1. The control is performed to supply the drive current I holding (1 polarity).

  In the example shown in FIG. 7A, the control unit 40 in the first AC driving process A1 starts from a phase having the same polarity (first polarity) as that of the immediately preceding first DC driving process D1. Control is performed to supply an alternating drive current I.

  In the example shown in FIG. 7B, the control unit 40 performs the second DC driving process D2 in the period from time t5 to time t6, and the second AC driving process A2 in the period from time t6 to time t7. The second DC driving process D2 is performed during the period from time t7 to time t8, and the second AC driving process A2 is performed during the period from time t8 to time t9.

  In the example shown in FIG. 7B, in the second DC drive process D2, the control unit 40 has the same polarity (the first polarity) over a period longer than ½ cycle of the drive current I in the second AC drive process A2. Control is performed to supply a drive current I that maintains (two polarities).

  In the example shown in FIG. 7B, the control unit 40 has the same polarity (first polarity) as that of the first DC driving process D1 in the second AC driving process A2, similarly to the first AC driving process A1. Control is performed to supply a drive current I that is a rectangular wave alternating current starting from the phase.

  Since the current flows with the same polarity during the period in which the drive current I is direct current, the arc spot becomes large, and the tip of the electrode including the unnecessary protrusions can be melted smoothly. During the period in which the drive current I is alternating current, a current that alternates between the first polarity and the second polarity flows, so that the arc spot is reduced and the growth of protrusions at the electrode tip necessary as a discharge starting point is promoted. it can.

  Accordingly, by appropriately setting the driving conditions (the frequency during the period in which the driving current I is AC, the length of the period in which the driving current I is DC, the length of the period in which the AC is AC, etc.), the driving current I becomes DC By alternately repeating the period of alternating current and the period of alternating current, a good electrode shape can be maintained and the discharge lamp 90 can be lit stably.

  However, when the above driving conditions are appropriately set in order to extend the life in accordance with the high luminance mode for supplying the rated power to the discharge lamp 90, the low luminance for sharing the power lower than the rated power with the discharge lamp 90 If the lighting is performed under the same conditions in the mode, the projecting portion of the electrode on the cathode side is deformed or the driving current I is AC when the DC current of the driving current I is too long and DC driving is performed. The projection 552p and the projection 562p may be deformed due to the frequency of the period being too low or the length of the AC period being too short, and the bright spot may not be stable and flicker may occur.

  Further, if the discharge lamp 90 is continuously lit in the same mode under the same driving condition, the first electrode 92 and the second electrode 93 are consumed, the projection 552p and the projection 562p are deformed, the bright spot is not stabilized, and flicker is generated. May occur.

  Therefore, in the discharge lamp lighting device 10 of the first embodiment, the control unit 40 determines at least one length of the period for performing the first DC driving process D1 and the period for performing the second DC driving process D2 according to the supplied power. Change. For example, in the example of the circuit configuration of the projector shown in FIG. 11, when the external signal for changing from the high luminance mode to the low luminance mode is received from the CPU 580 by the CPU 580 according to the user's request, the control unit 40 You may change so that the length of at least one of the period which performs the 1st DC drive process D1 and the period which performs the 2nd DC drive process D2 may be shortened. Thereby, deformation of the protrusion 552p and the protrusion 562p can be suppressed, the bright spot can be stabilized, and flicker can be suppressed.

  In the present embodiment, the control unit 40 performs power control for adjusting the drive current I so that the power supplied to the discharge lamp 90 is maintained at a constant 230 W in the high luminance mode, and in the low luminance mode. Power control is performed to adjust the drive current I so that the power supplied to the discharge lamp 90 is kept constant at 160 W. In the high luminance mode, the period for performing the first DC processing D1 and the period for performing the second DC processing D2 are set to 0.077 [s] as in the example shown in FIGS. 7A and 7B. The frequency of the first AC processing A1 and the second AC processing A2 is 95 Hz, and the number of cycles is 3.

  When the discharge lamp 90 is lit as in the example shown in FIGS. 7A and 7B in the high luminance mode, the amount of heat generated by the discharge and the thermal characteristics of the first electrode 92 and the second electrode 93 are reduced. Therefore, the driving current I is appropriately controlled, so that the protrusion 552p and the protrusion 562p are kept good, and problems such as blackening hardly occur, and a long-life discharge lamp can be realized.

  However, when the discharge lamp 90 is turned on as in the example shown in FIGS. 7A and 7B in the low luminance mode, a period for performing the first DC process D1 and a period for performing the second DC process D2 are obtained. Since the first electrode 92 and the second electrode 93 are deformed when the cathode is too long, the arc may not be stable and flicker may occur.

  On the other hand, when the low luminance mode is selected at the time of steady lighting, as shown in FIGS. 8A and 8B, the period for performing the first DC processing D1 and the second DC processing are performed. The period in which D2 is performed is 0.059 [s], the frequency of the first AC processing A1 and the second AC processing A2 is 95 Hz, and the number of cycles is 3.

  In this embodiment, when the low luminance mode is selected, the example shown in FIGS. 7A and 7B in the high luminance mode is shown in FIGS. 8A and 8B. Change the example immediately. As a result, the direct current period is shortened even when the temperature of the tip portions of the first electrode 92 and the second electrode 93 decreases and the meltability of the protrusions 552p and 562p decreases due to the low luminance mode. Accordingly, it is possible to suppress the deformation of the electrode on the cathode side, maintain a projection having a good shape, and suppress flicker.

  As another example, when the control unit 40 receives an external signal for changing from the high luminance mode to the low luminance mode, a period in which the first DC driving process D1 is performed and a period in which the second DC driving process D2 is performed. The length of at least one of these may be changed with time so as to decrease stepwise.

  In the above-described example, the example in which the lengths of both the period in which the first DC driving process D1 is performed and the period in which the second DC driving process D2 is performed has been described. However, for example, the first electrode 92 of the discharge lamp 90 and If the thermal conditions of the second electrode 93 (ease of increasing the electrode temperature, etc.) are significantly different, either the period of performing the first DC driving process D1 or the length of the period of performing the second DC driving process D2 May be changed.

3. Discharge lamp lighting device according to the second embodiment In the discharge lamp lighting device 10 of the second embodiment, when the low luminance mode is selected at the time of steady lighting, the control unit 40 performs a period of performing the first DC drive processing D1 and The length of at least one of the periods during which the second DC driving process D2 is performed is shortened, and the frequency of at least one of the first AC driving process A1 and the second AC driving process A2 is further increased.
In the first embodiment described above, when the low luminance mode is selected, the driving current I supplied to the discharge lamp 90 is changed from the example shown in FIG. 7 in the high luminance mode to the example shown in FIG. While changing quickly, the DC period can be shortened and deformation of the electrode on the cathode side can be suppressed, while the value of the drive current I supplied in the low brightness mode is lower than in the high brightness mode and the DC period is shortened. As a result, the temperatures of the tips of the first electrode 92 and the second electrode 93 at the time of anode may decrease, and the meltability of the protrusions 552p and 562p may decrease.
Therefore, in this embodiment, when the low luminance mode is selected, the deformation of the electrode on the cathode side is suppressed by shortening the DC period, and the arc stability is increased by increasing the AC frequency. This makes it possible to keep the protrusions of good shape on both electrodes and suppress flicker.

  Further, when the low luminance mode is selected, the control unit 40 changes so as to increase at least one of the period in which the first AC driving process A1 is performed and the period in which the second AC driving process A2 is performed. You may let them.

FIG. 9A is a timing chart showing a waveform example of the drive current I in the first section in the high luminance mode during steady lighting. FIG. 9B is a timing chart showing the waveform of the drive current I in the first section in the low luminance mode during steady lighting.
As shown in FIG. 9B, the drive current I in the low luminance mode in this embodiment is a frequency of 95 Hz for performing the first AC drive processing A1 shown in FIG. 8B as the first embodiment. In contrast to the example, an example in which the frequency is increased to 165 Hz is shown.
In the present embodiment, the driving current I in the low luminance mode shown in FIG. 9B is 95 [Hz] in the first AC driving processing A1 in the high luminance mode shown in FIG. 9A. In the example, the frequency in the first AC driving process A1 is 165 Hz with respect to the frequency, and the number of cycles is increased from 3 to 11. In the drive current I in the present embodiment, the frequency and the number of cycles of the second AC drive process A2 in the second section are also set to the frequency and the number of cycles of the first embodiment as shown in FIG. It changes similarly to the drive current I in the first section.

  By changing the frequency in the first AC driving process A1 shown in the example of FIG. 9B, the time held in one polarity during the AC driving period is shortened. In the low luminance mode, the meltability at the tips of the first electrode and the second electrode 93 is lower than that in the high luminance mode. Therefore, if the period held in one polarity is too long, the protrusion deformation on the cathode side is further increased. It becomes easy to cause. Therefore, by increasing the frequency of the AC drive processing period, the effect of suppressing the deformation of the protrusions by shortening the DC drive period in the low luminance mode can be made even more effective, even when operating with low power The occurrence of flicker can be further suppressed.

  Furthermore, as in the example shown in FIG. 9B, the frequency in the AC driving process is increased, the number of cycles is increased, and the frequency of the DC driving process period is appropriately reduced, so that the operation can be performed with lower power. Also when flickering, the occurrence of flicker can be suppressed.

4). Discharge lamp lighting device according to the third embodiment In the discharge lamp lighting device 10 of the first and second embodiments, the control unit 40 suppresses electrode consumption by control as in the examples illustrated in FIGS. 7 to 9. However, when the discharge lamp 90 is lit for a long time in the same mode (high luminance mode or low luminance mode), the distance between the protrusion 552p of the first electrode 92 and the protrusion 562p of the second electrode 93 is reduced. The increase, that is, the progress of deterioration cannot be stopped.
Therefore, in the present embodiment, a change in which at least one of the period in which the first DC driving process D1 is performed and the period in which the second DC driving process D2 is performed is shortened, the period in which the first AC driving process A1 is performed, and the second AC driving. A change that increases at least one frequency during the period in which the process A2 is performed, and a change that increases the number of periods of at least one of the period in which the first AC drive process A1 is performed and the period in which the second AC drive process A2 is performed are the inter-electrode distances. Depending on the stage. Generally, when the distance between the protrusion 552p and the protrusion 562p increases due to electrode consumption, the drive voltage Vla during steady lighting increases. Therefore, for example, the control unit 40 may perform the above-described stepwise change based on the drive voltage Vla detected by the voltage detection unit 60 provided inside the discharge lamp lighting device 10.

表１には、低輝度モードにおいて駆動電圧Ｖｌａに応じて、駆動パラメーターを変更する例を示している。表１に示すテーブルにおいては、駆動電圧Ｖｌａが高くなると、交流駆動処理期間における周波数が高くなり、さらに駆動電圧Ｖｌａが高くなると、交流駆動処理期間における周期数が多くなる。

Table 1 shows an example in which the drive parameter is changed according to the drive voltage Vla in the low luminance mode. In the table shown in Table 1, when the drive voltage Vla is increased, the frequency in the AC drive processing period is increased, and when the drive voltage Vla is further increased, the number of cycles in the AC drive process period is increased.

FIG. 10 is a flowchart showing an example of control during steady lighting of the discharge lamp lighting device 10 of the third embodiment. In the flowchart shown in FIG. 10, control from when the discharge lamp 90 is steadily turned on to when it is turned off is shown.
First, the voltage detector 60 detects the drive voltage Vla (step S100). Next, the control unit 40 selects a drive condition corresponding to the drive voltage Vla detected in step S100 from the table shown in Table 1 stored in the storage unit 44 (step S102).
After selecting the driving condition in step S102 of FIG. 10, the control unit 40 determines whether or not the driving condition needs to be changed (step S104). When the control unit 40 determines that the drive condition needs to be changed (YES in step S104), the drive unit 90 is changed to the drive condition selected in step S102 and the discharge lamp 90 is driven (step S106). . When the control unit 40 determines that it is not necessary to change the driving condition (NO in step S104), the discharge lamp 90 is continuously driven under the previous driving condition.
In the case of NO in step S104 and after step S106, the control unit 40 determines whether or not there is an instruction to turn off the discharge lamp 90 (step S108). When the control unit 40 determines that there is a turn-off command (YES in step S108), the lighting of the discharge lamp 90 is terminated (turned off) (step S110). When the control unit 40 determines that there is no turn-off command (NO in step S108), the control from step S100 to step S108 is repeated until there is a turn-off command.

  As a result, even when the driving duration time in the same mode is increased and the electrode of the discharge lamp 90 is consumed, the driving current Ila is reduced, and flicker is likely to occur in the low luminance mode. Flicker can be suppressed by changing the above-described driving process parameters in accordance with the driving voltage Vla. When the frequency and the number of cycles in the AC drive processing period are suddenly increased, the amount of melting of the protrusions 552p and 562p is decreased, resulting in a minute protrusion, which increases the distance between the electrodes. In contrast, in the present embodiment, flicker can be suppressed while suppressing an increase in the interelectrode distance by changing the driving condition of the discharge lamp 90 in a stepwise manner in accordance with the driving voltage Vla.

  Although Table 1 shows an example of the low luminance mode, the high luminance mode can be similarly handled.

  Further, the range of the driving voltage Vla and the number of times of changing the driving parameter shown in Table 1 can be appropriately set according to the specification of the discharge lamp, and one of the frequency or the cycle number in the AC driving processing period A1 and the AC driving processing period A2. However, they may be changed at the same time.

(1) Modification 1 of the third embodiment
In the third embodiment, when the driving voltage Vla during steady lighting increases, the frequency in the AC driving process period increases, and when the driving voltage Vla further increases, the driving condition (Table) increases the number of cycles in the AC driving process period. A driving condition suitable for the detected driving voltage Vla was selected from the table of 1). In the modified example 1, when the drive voltage Vla is further increased, it is possible to set a drive condition (Table 2) that shortens the length of the DC drive processing period.

表２には、低輝度モードにおいて駆動電圧Ｖｌａに応じて、駆動パラメーターを変更する例を示している。表２に示すテーブルにおいては、駆動電圧Ｖｌａが高くなると、交流駆動処理期間における周波数が高くなり、さらに駆動電圧Ｖｌａが高くなると、交流駆動処理期間における周期数が多くなるとともに、駆動電圧Ｖｌａが高くなると、直流駆動処理期間が長くなる。

Table 2 shows an example in which the drive parameter is changed according to the drive voltage Vla in the low luminance mode. In the table shown in Table 2, when the drive voltage Vla is increased, the frequency during the AC drive processing period is increased, and when the drive voltage Vla is further increased, the number of cycles in the AC drive process period is increased and the drive voltage Vla is increased. Then, the DC drive processing period becomes long.

(2) Modification 2 of the third embodiment
In the third embodiment, the driving condition is selected according to the value of the driving voltage Vla detected during steady lighting as the predetermined condition. However, the driving current Ila is detected during steady lighting and the detected driving current Ila is detected. It is also possible to select a driving condition using the above as a predetermined condition.

表３には、低輝度モードにおいて駆動電流Ｉｌａに応じて、駆動パラメーターを変更する例を示している。表３に示すテーブルにおいては、駆動電圧Ｉｌａが低くなると、交流駆動処理期間における周波数が高くなり、さらに駆動電流Ｉｌａが低くなると、交流駆動処理期間における周期数が多くなるとともに、駆動電流Ｉｌａが高くなると、直流駆動処理期間が長くなる。

Table 3 shows an example in which the drive parameter is changed according to the drive current Ila in the low luminance mode. In the table shown in Table 3, when the drive voltage Ila decreases, the frequency during the AC drive processing period increases, and when the drive current Ila decreases further, the number of cycles in the AC drive process period increases and the drive current Ila increases. Then, the DC drive processing period becomes long.

5. Circuit Configuration of Projector FIG. 11 is a diagram illustrating an example of a circuit configuration of the projector according to the present embodiment. In addition to the optical system described above, the projector 500 includes an image signal conversion unit 510, a DC power supply device 520, a discharge lamp lighting device 10, a discharge lamp 90, liquid crystal panels 560R, 560G, and 560B, and an image processing device 570.

  The image signal converter 510 converts an externally input image signal 502 (such as a luminance-color difference signal or an analog RGB signal) 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 the three image signals 512R, 512G, and 512B, and outputs drive signals 572R, 572G, and 572B for driving the liquid crystal panels 560R, 560G, and 560B, respectively.

  The DC power supply device 520 converts an AC voltage supplied from an external AC power supply 600 into a constant DC voltage, and an image signal conversion unit on the secondary side of a transformer (not shown, but included in the DC power supply device 520). 510, a DC voltage is supplied to the image processing device 570 and the discharge lamp lighting device 10 on the primary side of the transformer.

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

  The liquid crystal panels 560R, 560G, and 560B modulate the luminance of the color light incident on each liquid crystal panel via the optical system described above by the drive signals 572R, 572G, and 572B, respectively.

  A CPU (Central Processing Unit) 580 controls operations from the start of lighting of the projector to the extinction thereof. For example, a lighting command or a lighting command may be output to the discharge lamp lighting device 10 via the communication signal 582. Further, the CPU 580 may receive lighting information of the discharge lamp 90 from the discharge lamp lighting device 10 via the communication signal 532.

  The projector 500 configured as described above can further suppress the formation of steady convection in the discharge lamp 90 and prevent uneven consumption of electrodes and uneven deposition of electrode materials.

  In each of the above embodiments, a projector using three liquid crystal panels has been described as an example. However, the present invention is not limited to this, and one, two, four or more liquid crystal panels are used. It can also be applied to projectors.

  In each of the above embodiments, a transmissive projector has been described as an example. However, the present invention is not limited to this, and can be applied to a reflective projector. Here, “transmission type” means that an electro-optic modulation device as a light modulation means such as a transmission type liquid crystal panel transmits light, and “reflection type” means This means that an electro-optic modulator as a light modulator such as a reflective liquid crystal panel or a micromirror type light modulator is a type that reflects light. As the micromirror light modulator, for example, DMD (digital micromirror device; trademark of Texas Instruments) can be used. Even when the present invention is applied to a reflective projector, the same effect as that of a transmissive projector can be obtained.

  The present invention can be applied to a front projection type projector that projects from the side that observes the projected image, or to a rear projection type projector that projects from the side opposite to the side that observes the projected image. is there.

  In addition, this invention is not limited to the above-mentioned embodiment, A various deformation | transformation implementation is possible within the range of the summary of this invention.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  For example, in the above-described embodiment, as the alternating current supplied as the drive current I, the alternating current that alternately repeats the period in which the predetermined current value of the first polarity continues and the period in which the predetermined current value of the second polarity continues ( (Rectangular wave alternating current) has been described as an example, but the alternating current supplied as the drive current I may be an alternating current whose current value changes during the period in which the first polarity or the second polarity continues.

  In addition, for example, the period during which the first DC driving process and the second DC driving process are performed, the frequency and the number of cycles for performing the first AC driving process and the second AC driving process are arbitrarily set according to the specifications of the discharge lamp and the like. It is possible.

  Further, the period for performing the first DC driving process and the second DC driving process, the frequency and the number of cycles for performing the first AC driving process and the second AC driving process are the same, but the discharge lamp 90 and the first electrode 92 are used. A difference may be provided as appropriate, for example, when the second electrode 93 is placed thermally or optically asymmetric.

  It is also possible to continuously change the period for performing the first DC driving process and the second DC driving process, the frequency and the period for performing the first AC driving process and the second AC driving process to a predetermined set value.

  In the projector of the present invention, the high luminance mode and the low luminance mode are shown as examples. However, when there are two or more luminance modes, the first AC driving process and the second DC driving process are performed. It is possible to appropriately set the frequency and the number of cycles for performing the driving process and the second AC driving process for each luminance mode.

  DESCRIPTION OF SYMBOLS 10 Discharge lamp lighting device, 20 Power control circuit, 21 Switch element, 22 Diode, 23 Coil, 24 Capacitor, 30 Polarity inversion circuit, 31-34 Switch element, 40 Control part, 40-1 Current control means, 40-2 Polarity Inversion control means, 41 system controller, 42 power control circuit controller, 43 polarity inversion circuit controller, 44 storage unit, 50 sub-reflecting mirror, 60 voltage detection unit, 61-63 resistor, 70 igniter circuit, 80 DC power supply, 90 discharge lamp 91 discharge space, 92 first electrode, 93 second electrode, 112 main reflector, 114 fixing member, 200 light source device, 210 light source unit, 305 collimating lens, 310 illumination optical system, 320 color separation optical system, 330R, 330G, 330B liquid crystal light valve, 340 Loss dichroic prism, 350 projection optical system, 500 projector, 502 image signal, 510 image signal converter, 512R image signal (R), 512G image signal (G), 512B image signal (B), 520 DC power supply, 522 fixed Member, 532 Communication signal, 534 Conductive member, 536 First terminal, 544 Conductive member, 546 Second terminal, 552p Protrusion, 560G Liquid crystal panel (G), 560B Liquid crystal panel (B), 562p Protrusion, 570 Image processing apparatus 572R liquid crystal panel (R) drive signal, 572G liquid crystal panel (G) drive signal, 572B liquid crystal panel (B) drive signal, 580 CPU, 582 communication signal, 600 AC power supply, 700 screen.

Claims (10)

A discharge lamp driving unit for supplying a driving current to the discharge lamp and driving the discharge lamp;
A control unit for controlling the discharge lamp driving unit,
The controller is
In the first section, the first DC driving process and the first AC driving process are alternately performed,
In the second section different from the first section, the second DC driving process and the second AC driving process are alternately performed,
In the first DC driving process, control is performed to supply a first DC current composed of a first polarity component starting from the first polarity as the driving current,
In the first AC driving process, control is performed to supply a first AC current that repeats a first polarity component and a second polarity component as the driving current,
In the second DC driving process, control is performed to supply a second DC current composed of a second polarity component starting from the second polarity as the driving current,
In the second AC driving process, control is performed to supply a second AC current that repeats a first polarity component and a second polarity component as the driving current,
A discharge lamp lighting device that changes a length of at least one of a period for performing the first DC driving process and a period for performing the second DC driving process when a predetermined condition is satisfied. In the discharge lamp lighting device according to claim 1,
When the predetermined condition is satisfied, the control unit increases the average value of at least one of a frequency during the first AC driving process and a period during the second AC driving process. . In the discharge lamp lighting device according to claim 1 or 2,
When the predetermined condition is satisfied, the control unit increases the length of at least one of a period during which the first AC driving process is performed and a period during which the second AC driving process is performed. In the discharge lamp lighting device according to claims 1 to 3,
The discharge lamp lighting device, wherein the predetermined condition is to receive a signal for reducing the operating power of the discharge lamp from the outside by a predetermined value or more. In the discharge lamp lighting device according to claims 1 to 3,
The predetermined condition is the discharge lamp lighting device in which the voltage during steady lighting of the discharge lamp is increased to a predetermined value or more. In the discharge lamp lighting device according to claims 1 to 3,
The predetermined condition is the discharge lamp lighting device in which a current during steady lighting of the discharge lamp is reduced to a predetermined value or less.   A projector comprising the discharge lamp lighting device according to claim 1. A method for driving a discharge lamp that is lit by supplying a driving current to the discharge lamp,
In the first section, the first DC driving process and the first AC driving process are alternately performed,
In the second section different from the first section, the second DC driving process and the second AC driving process are alternately performed,
In the first DC driving process, control is performed to supply a first DC current composed of a first polarity component starting from the first polarity as the driving current,
In the first AC driving process, control is performed to supply a first AC current that repeats a first polarity component and a second polarity component as the driving current,
In the second DC driving process, control is performed to supply a second DC current composed of a second polarity component starting from the second polarity as the driving current,
In the second AC driving process, control is performed to supply a second AC current that repeats a first polarity component and a second polarity component as the driving current,
A discharge lamp driving method in which when a predetermined condition is satisfied, at least one of a period during which the first DC driving process is performed and a period during which the second DC driving process is performed is changed. A method for driving a discharge lamp according to claim 8,
When the predetermined condition is satisfied, the discharge lamp driving method changes the frequency so as to increase at least one of the period during which the first AC driving process is performed and the period during which the second AC driving process is performed. A discharge lamp driving method according to any one of claims 8 to 9,
When the predetermined condition is satisfied, the discharge lamp driving method is configured to change the length of at least one of the period for performing the first AC driving process and the period for performing the second AC driving process.

Images