JP4239800B2 - Electrodeless discharge lamp lighting device - Google Patents

Description

  The present invention relates to an electrodeless discharge lamp lighting device.

  Conventionally, various types of electrodeless discharge lamp lighting devices (electrodeless discharge lamp devices) have been proposed and are commercially available. For example, an electrodeless discharge lamp lighting device as shown in FIG. 21 receives a power supply from an AC power supply Vin and outputs a DC voltage VDC, and a power supply from the DC power supply E receives a high-frequency voltage Vcoil. , An induction coil 91 connected to the output of the inverter circuit 90, and an electrodeless discharge lamp L disposed in proximity to the induction coil 91.

  The DC power source E is composed of a boost chopper circuit composed of a rectifying diode bridge 920, an FET 921, an inductor 922, a diode 923, a control circuit 924, and a smoothing capacitor 925. The inverter circuit 90 includes FETs 90a and 90b, an inductor 901, capacitors 902 and 903. The electrodeless discharge lamp L has a transparent spherical glass bulb or a spherical glass bulb with an inner surface coated with a phosphor, and a discharge gas (for example, mercury and a rare gas) such as an inert gas or a metal vapor. The inverter circuit 90 energizes the induction coil 91 with a high frequency current of several tens of kHz to several hundreds of MHz, thereby generating a high frequency electromagnetic field in the induction coil 91 and supplying high frequency power to the electrodeless discharge lamp L. . In response to this, a high frequency plasma current is generated in the electrodeless discharge lamp L to generate ultraviolet rays or visible light.

  Further, the drive circuit 94 outputs substantially rectangular wave drive signals to the FETs 90a and 90b between the Hout-H-GND terminals and between the Lout-L-GND terminals at a frequency corresponding to the control voltage Vf (not shown) ( The phase difference between them is approximately 180 °).

Patent Document 1 discloses the following invention. In a discharge lamp device in which a coil is wound around a valve filled with low-pressure gas and the output of a high-frequency generator is supplied to the coil, a temperature detection circuit that detects the ambient temperature and an operation based on the output of the temperature detection circuit And a switching circuit that switches the magnitude or frequency of the current supplied to the coil. When the temperature is low, a current that does not cause the coil to start discharging is supplied in advance by Joule heat generated in the coil itself. It is characterized in that the lamp is started by switching the coil current after raising the temperature.
Japanese Patent Application Laid-Open No. Sho 62-163296 (pages 2 to 3 and FIG. 1)

  However, the above conventional electrodeless discharge lamp lighting device has the following problems. When the electrodeless discharge lamp L is started by the above method, the set value Vset of the output voltage of the inverter circuit 90 is normally constant regardless of the ambient temperature Ta as shown by the dotted line in FIG. The starting voltage Vign of the discharge lamp L, that is, the voltage necessary for starting the ignition, becomes a curve that tends to increase as the temperature decreases. That is, in the case of the electrodeless discharge lamp L, the temperature coefficient of the starting voltage Vign with respect to the ambient temperature Ta (for example, −20 ° C. to + 60 ° C.) is always negative, which is different from, for example, an electroded FL lamp. In the case of the FL lamp, the temperature coefficient is not always negative but has a characteristic of being positive on the high temperature side. For this reason, in the case of the electrodeless discharge lamp L, when the ambient temperature Ta is low, the difference between the output voltage set value Vset and the starting voltage Vign becomes small. For example, when starting in a dark state or around the electrodeless discharge lamp L When the starting voltage Vign is equivalently increased due to the influence of the adjacent conductor, etc., there is a problem that the starting property of the electrodeless discharge lamp L is deteriorated or the lighting is not turned on in the worst case. On the other hand, when the ambient temperature Ta is high, there is a problem that the difference between the output voltage set value Vset and the starting voltage Vign becomes larger than necessary, and the constituent circuit elements are destroyed due to thermal stress.

  Further, when the electrodeless discharge lamp L is started, the inverter circuit 90 requires a larger output power than when it is normally lit, and the DC power source E shown in FIG. Voltage fluctuations such as ripples are likely to occur. In a conventional electrodeless discharge lamp lighting device or the like, as a result of the voltage fluctuation of the output voltage VDC, the output voltage set value Vset is also affected and fluctuates. As a result, the output voltage set value Vset is lowered and startability is increased. There were also problems such as worsening.

  The present invention has been made in view of the above-mentioned points. The object of the present invention is to prevent the startability from deteriorating or not lighting when the ambient temperature Ta is low, and to the circuit element when the ambient temperature Ta is high. The object is to provide an electrodeless discharge lamp lighting device with low thermal stress.

The invention described in claim 1 includes an induction coil that generates a high-frequency magnetic field for an electrodeless discharge lamp, a switching element that converts DC power into high-frequency power, and a resonance circuit, and supplies the high-frequency power to the induction coil. A power conversion circuit; a drive circuit that generates a drive signal for varying the on / off frequency of the switching element according to the magnitude of the control voltage and outputs the drive signal to the switching element; and a temperature detection unit whose output varies depending on the ambient temperature; The drive circuit is controlled by varying the magnitude of the control voltage when starting the electrodeless discharge lamp to vary the on / off frequency of the switching element, thereby varying the frequency of the high-frequency voltage. and a voltage control unit for varying the of the drive circuit, charging and discharging operations by the capacitor has a capacitor An oscillation unit that oscillates by repeatedly performing, and a drive unit that varies the frequency of the drive signal according to the frequency of the output voltage from the oscillation unit and outputs the drive signal to the switching element, Is a charge voltage of the capacitor, and compares the triangular wave voltage obtained by the charge / discharge operation with a reference voltage and outputs a rectangular wave voltage to the drive unit, and the temperature detection unit, The temperature detection unit is a mirror circuit composed of a semiconductor element whose conduction resistance changes with respect to a temperature change, and the capacitor according to the magnitude of the control voltage of the voltage control unit and the change of the conduction resistance of the semiconductor element The charging / discharging frequency of the capacitor is changed by changing the magnitude of the charging / discharging current to the capacitor and switching charging / discharging of the capacitor by the output of the operational amplifier. It allows the electrodeless discharge lamp of the at the time of low-temperature output using the ambient temperature of the temperature detecting unit varies the frequency of the drive signal so as to increase the high-frequency voltage from the high temperature at the time of starting and the high-frequency voltage It characterized the Turkey by varying the frequency of.

  In this structure, the voltage of the high-frequency power output from the power conversion circuit is higher when the ambient temperature is low than when the ambient temperature is low, so that the startability of the electrodeless discharge lamp can be improved when the ambient temperature is low, At high temperatures, thermal stress on the circuit elements can be reduced.

In this structure, the drive signal can be varied from the temperature characteristics of the semiconductor element.

  According to the present invention, the startability of the electrodeless discharge lamp can be improved when the ambient temperature is low, and the thermal stress on the circuit element can be reduced when the ambient temperature is high.

( Basic form )
First, the structure of a basic form is demonstrated using FIGS. The electrodeless discharge lamp lighting device of the basic form stably starts and lights the electrodeless discharge lamp L in a wide range of ambient temperature Ta (for example, −20 ° C. to + 60 ° C.), as shown in FIG. DC power source E, inverter circuit 1, induction coil 2, drive circuit 3, voltage detection circuit 4, temperature detection unit 5, and voltage control unit 6 are provided.

  The electrodeless discharge lamp L has a transparent spherical glass bulb or a spherical glass bulb with an inner surface coated with a phosphor, and a discharge gas (for example, mercury or a rare gas) such as inert gas or metal vapor is enclosed. Yes. Then, the high frequency power supplied from the induction coil 2 generates a high frequency plasma current in the electrodeless discharge lamp L to generate ultraviolet rays or visible light.

  The DC power source E converts AC power from an AC power source Vin such as a commercial power source into DC power and supplies it to the inverter circuit 1. The DC power source E is constituted by, for example, a step-up chopper circuit including a diode bridge 70 that full-wave rectifies AC power, an FET 71, an inductor 72, a diode 73, a control circuit 74, and a smoothing capacitor 75. The control circuit 74 is connected to the gate of the FET 71. Note that the chopper circuit includes a step-up type, a step-down type, a polarity reversal type, and the like, which are selectively used according to the application.

  The inverter circuit 1 is a power conversion circuit that converts DC power supplied from the DC power source E into a high-frequency voltage Vcoil and outputs it. For example, a high-frequency voltage Vcoil of several tens to several hundreds of MHz is applied to the induction coil 2. Supply. The inverter circuit 1 includes two switching elements 10 a and 10 b and a resonance circuit 11.

  For example, FETs are used as the switching elements 10a and 10b, and the operation frequency finv of the high-frequency voltage Vcoil is swept by changing the switching state (ON and OFF).

  The resonance circuit 11 includes, for example, a coil 110 and capacitors 111 and 112, and outputs a large high-frequency voltage Vcoil near the resonance frequency. Further, when the electrodeless discharge lamp L is used as a load, since it is an inductor load at the start of ignition, a larger electric power is required at the start than other light sources such as an electroded FL lamp. Therefore, in order to perform stable starting and lighting, it is necessary to set the Q of the resonance circuit 11 high.

  FIG. 2 shows the change of the high-frequency voltage Vcoil output from the inverter circuit 1 with respect to the operating frequency finv. At the time of starting the electrodeless discharge lamp L, the high frequency voltage Vcoil is gradually increased by decreasing the operating frequency finv from fs to fe and by sweeping the frequency so as to approach the resonance frequency of the resonance circuit 11, and this frequency sweep. Since the electrodeless discharge lamp L is designed to exceed the minimum voltage required for starting ignition during the period of time, the electrodeless discharge lamp L is lit at a certain frequency between fs and fe. Immediately after the lighting, the high-frequency voltage Vcoil moves on the lighting-side curve in FIG. 2 and decreases.

  The start by the frequency sweep as described above is, for example, when there is a load impedance fluctuation factor of the inverter circuit 1 such as a change in the ambient temperature Ta or a proximity of the metal housing around the electrodeless discharge lamp L, and the high frequency voltage Vcoil changes greatly. Even if it exists, since the influence of load impedance fluctuation | variation can be absorbed, the electrodeless discharge lamp L can be started stably and can be lit. Such a start by frequency sweep is particularly effective in the case of an electrodeless discharge lamp load.

  As shown in FIG. 1, the induction coil 2 is connected to the output side of the inverter circuit 1, and the high frequency voltage Vcoil is supplied from the inverter circuit 1. Thereby, the induction coil 2 generates a high-frequency electromagnetic field and supplies high-frequency power to the electrodeless discharge lamp L.

  The drive circuit 3 has a frequency that varies according to the magnitude of the control voltage Vf from the voltage control unit 6, and is substantially rectangular with respect to the switching elements 10a and 10b between the Hout-H-GND terminals and between the Lout-L-GND terminals. This is a drive circuit that outputs a wavy drive signal (the phase difference between them is approximately 180 °). At this time, as shown in FIG. 3, the drive signal is output so that the higher the control voltage Vf, the lower the operating frequency finv of the high-frequency voltage Vcoil.

  As shown in FIG. 1, the voltage detection circuit 4 includes, for example, resistors 40 and 41, diodes 42 and 43, and a capacitor 44. The voltage detection circuit 4 detects, rectifies and smoothes the high-frequency voltage Vcoil output from the inverter circuit 1 and outputs it to the voltage control unit 6.

  The temperature detection unit 5 is provided in, for example, the voltage control unit 6, uses the DC power supply E 1 as a power source, an impedance circuit 50 that is an impedance element and a temperature detection element for temperature detection, and an integration circuit including a capacitor 51, The capacitor 51 is composed of a charge discharge switch 52, a resistor 53, and the like, and its output varies depending on the ambient temperature Ta. In the temperature detection unit 5, when the charge discharge switch 52 is switched from ON to OFF, the capacitor 51 is charged through the temperature-sensitive resistor 50 by receiving power supply from the DC power source E1, and an operational amplifier (described later) uses the voltage VC1 across the capacitor 51. It outputs to 60 non-inverting input terminals. The temperature-sensitive resistor 50 has an impedance value that varies depending on the ambient temperature Ta, and the resistance value can be varied substantially linearly depending on the ambient temperature Ta. For example, if the ERA series manufactured by Matsushita Electronic Parts Co., Ltd. is used, various positive temperature coefficients of +1000 ppm / ° C. to +4700 ppm / ° C. can be selected. If such a component is used, the relationship between the ambient temperature Ta and the resistance value of the temperature-sensitive resistor 50 (R1) changes substantially linearly with a positive slope as shown by the solid line in FIG. Accordingly, the voltage VC1 across the capacitor 51 changes so as to decrease as the temperature increases and to increase as the temperature decreases.

As shown in FIG. 1, the voltage control unit 6 includes, for example, an operational amplifier 60 and resistors 61 and 62. The higher the ambient temperature Ta from the output of the voltage detection circuit 4 and the output of the temperature detection unit 5, the higher the frequency of the induction coil 2. The control voltage Vf is varied so that the voltage Vcoil increases. The operation principle of the voltage control unit 6 will be described. The voltage VC1 across the capacitor 51 in the temperature detection unit 5 is applied to the non-inverting input terminal of the operational amplifier 60, and the output of the voltage detection circuit 4 is connected to the operational amplifier 60 via the resistor 61. Applied to the inverting input terminal . Op amp 60 performs the differential amplification, and outputs a control voltage Vf to the drive circuit 3. At this time, the relationship between the ambient temperature Ta and the control voltage Vf changes substantially linearly with a negative slope as shown in FIG. In addition, the differential amplification operation of the operational amplifier 60 allows the output voltage set value Vset to be constant without being affected by the voltage fluctuation of the DC voltage VDC (see FIG. 1).

Next, the operation of the basic form will be described. FIG. 6 shows an example of the start operation by frequency sweep. When the AC power source Vin is turned on and the DC voltage VDC of the DC power source E rises (t = t1) (see FIG. 6 (e)), the temperature detection unit 5 charges the capacitor 51 via the temperature sensitive resistor 50 and both ends thereof. The voltage VC1 increases (see FIG. 6 (d)). The control voltage Vf of the voltage control unit 6 increases according to the voltage VC1 across the capacitor 51 (see FIG. 6C). When the control voltage Vf increases, the operating frequency finv of the high-frequency voltage Vcoil gradually decreases (see FIGS. 3 and 6B), so the high-frequency voltage Vcoil gradually increases (see FIG. 6A). . Then, at a certain operating frequency fm (t = t2) in the frequency sweep section, the electrodeless discharge lamp L is turned on, and then the high-frequency voltage Vcoil decreases immediately. At this time, since the output of the voltage detection circuit 4 also decreases, the control voltage Vf tends to increase again, and the high-frequency voltage Vcoil tends to increase until the capacitor 51 is fully charged and the both-end voltage VC1 becomes a constant value (FIG. 6 ( a) (Refer to the electrodeless discharge lamp L)).

  On the other hand, in the no-load state where there is no electrodeless discharge lamp L, the set voltage Vset becomes constant by a differential amplification operation of the operational amplifier 60 (see FIG. 6A (no electrodeless discharge lamp L)). Becomes the upper limit value of the high-frequency voltage Vcoil of the induction coil 2. Therefore, even if the Q of the resonance circuit 11 of the inverter circuit 1 is set higher than that of other light sources such as an electrodeless FL lamp as in the electrodeless discharge lamp L, the high-frequency voltage Vcoil Since the rising angle is relaxed and the high-frequency voltage Vcoil can be gradually increased, a voltage larger than necessary is not applied to the induction coil 2, and the high-frequency voltage Vcoil applied to the induction coil 2 is more finely applied. Can be controlled.

  The set voltage Vset of the inverter circuit 1 continuously changes with respect to the ambient temperature Ta as shown in FIG. 7, and when the ambient temperature Ta is lower than the conventional case (dotted line), the output voltage set value Vset is set. And the starting voltage Vign become larger, and when the ambient temperature Ta is high, the difference between the output voltage setting value Vset and the starting voltage Vign becomes smaller.

As described above, according to the basic form , the characteristic with respect to the ambient temperature Ta is linear and has the same tendency as the starting voltage Vign of the electrodeless discharge lamp L, and the high frequency voltage Vcoil of the induction coil 2 when the ambient temperature Ta is low is high. Since it becomes higher, the startability of the electrodeless discharge lamp L can be improved when the ambient temperature Ta is low, and the thermal stress on the circuit element can be reduced when the ambient temperature Ta is high. And since the temperature characteristic of the temperature sensitive resistor 50 is linear, characteristic control with respect to the ambient temperature Ta can be facilitated.

  Further, due to the differential amplification operation of the operational amplifier 60, the output voltage set value Vset becomes constant without being affected by the voltage fluctuation of the DC voltage VDC, and the startability deterioration due to the decrease of the output voltage set value Vset can also be reduced.

As a modification of the basic form , a component such as a thermistor may be used if the temperature sensitive element has a positive temperature coefficient. Even if it is such a structure, the effect similar to a basic form can be acquired.

As another modification of the basic form , the temperature detection unit 5 may be provided outside the voltage control unit 6. Even if it is such a structure, the effect similar to a basic form can be acquired.

( Reference Example 1 )
Reference Example 1 is the same as the basic configuration in that it includes a DC power supply E, an inverter circuit 1, an induction coil 2, a drive circuit 3, a voltage detection circuit 4, a temperature detection unit 5, and a voltage control unit 6. However, there are features described below that are not in the basic form . As shown in FIG. 8, the temperature detection unit 5 includes a temperature detection circuit 54 that detects the ambient temperature Ta, a temperature-sensitive resistor 50 and a resistor 55 that have different impedance values, and an output of the temperature detection circuit 54. Accordingly, a switch means for switching between the temperature sensitive resistor 50 and the resistor 55 by the switch 56 is provided.

  The switch 56 selects the resistor 55 when the ambient temperature Ta is equal to or higher than a predetermined temperature Tc set in advance, and selects the temperature sensitive resistor 50 when the ambient temperature Ta is lower than the temperature Tc. Here, as shown in FIG. 9, the temperature Tc is set to a temperature at which the resistance characteristic (R1a) of the temperature-sensitive resistor 50 and the resistance characteristic (R1b) of the resistor 55 intersect or in the vicinity thereof.

Next, the difference of the operation of Reference Example 1 from the basic mode will be described. First, the temperature detection circuit 54 shown in FIG. 8 detects the ambient temperature Ta, and when the ambient temperature Ta is equal to or higher than the temperature Tc, the switch 55 selects the resistor 55, and when the ambient temperature Ta is equal to or lower than the temperature Tc, the temperature sensitive resistor 50 is selected. As a result, the control voltage Vf has a substantially constant value above the temperature Tc as shown by the solid line in FIG. 10, but has a negative temperature coefficient below the temperature Tc. As a result, as shown in FIG. 11, the difference between the output voltage set value Vset and the starting voltage Vign is larger when the ambient temperature Ta is lower than in the conventional case (dotted line).

As described above, according to Reference Example 1 , when the ambient temperature Ta is low, the difference between the output voltage set value Vset and the starting voltage Vign becomes large, so that the startability of the electrodeless discharge lamp L can be improved.

  Further, since the output voltage set value Vset with respect to the ambient temperature Ta can be controlled by the resistance characteristics of the temperature-sensitive resistor 50 and the resistor 55, the degree of freedom in design can be increased.

( Reference Example 2 )
Reference Example 2 is the same as the basic configuration in that it includes a DC power supply E, an inverter circuit 1, an induction coil 2, a drive circuit 3, a voltage detection circuit 4, a temperature detection unit 5, and a voltage control unit 6. However, there are features described below that are not in the basic form . As shown in FIG. 12, the temperature detection unit 5 includes a temperature detection circuit 54 that detects the ambient temperature Ta, and resistors 57 a and 57 b that have different impedance values, and according to the output of the temperature detection circuit 54. A switch 59 is provided for switching the resistors 57a and 57b.

  As shown in FIG. 13, the switch 59 selects the resistor 57b by the switch 59 when the ambient temperature Ta is equal to or higher than a predetermined temperature Tc, and selects the resistor 57a when the ambient temperature is higher than the temperature Tc. Here, if the resistance value of the resistor 57a is R2a and the resistance value of the resistor 57b is R2b, there is a relationship of R2a <R2b.

Next, the difference between the operation of this reference example and the basic mode will be described. First, the temperature detection circuit 54 shown in FIG. 12 detects the ambient temperature Ta. When the ambient temperature Ta is equal to or higher than the temperature Tc, the resistor 57b is selected. When the ambient temperature Ta is equal to or lower than the temperature Tc, the resistor 57a is selected. As a result, the control voltage Vf below the temperature Tc is higher than the temperature Tc or higher, as shown in FIG. As a result, the output voltage Vset of the inverter circuit 1 changes stepwise with respect to the ambient temperature Ta as shown in FIG. 15, and when the ambient temperature Ta is low, the difference between the output voltage set value Vset and the starting voltage Vign is more growing.

As described above, according to this reference example , when the ambient temperature Ta is low, the difference between the output voltage set value Vset and the starting voltage Vign becomes large, so that the startability of the electrodeless discharge lamp L can be improved.

  Further, since the output voltage set value Vset with respect to the ambient temperature Ta can be controlled by the resistance values of the resistors 57a and 57b, the degree of freedom in design can be increased.

As a modification of this reference example , the resistance value of the resistor 57b may be further increased. With such a configuration, when the ambient temperature Ta is high, the output voltage Vset of the inverter circuit 1 is further reduced, and the difference between the output voltage setting value Vset and the starting voltage Vign becomes smaller, so that the thermal stress on the circuit elements is reduced. Can be reduced.

( Embodiment )
This embodiment is the same as the basic embodiment in that it includes a DC power supply E, an inverter circuit 1, an induction coil 2, a drive circuit 3, a voltage detection circuit 4, a temperature detection unit 5, and a voltage control unit 6. However, there are features described below that are not in the basic form . As shown in FIG. 16, the voltage control unit 6 converts the temperature-sensitive resistor 50 into a resistor 58, which is a normal resistor, and the drive circuit 3 includes a drive unit 30 and an oscillation unit 31 that drive the switching elements 10a and 10b. Is done. The voltage control unit 6 varies the current of the charge / discharge circuit (hereinafter referred to as “charge / discharge current”) in accordance with the impedance change due to the temperature characteristics of the semiconductor element, thereby changing the control voltage Vf.

  The oscillating unit 31 is, for example, an RC oscillating circuit (charging / discharging circuit) composed of a semiconductor element such as an operational amplifier 310, a reference voltage Vref, a resistor 311, a capacitor 312, and a FET that constitutes a mirror circuit as the temperature detecting unit 5. The control voltage Vf of the voltage control unit 6 is connected to the input terminal of the oscillation unit 31.

Oscillator 31 performs oscillation by repeating charge and discharge operation by the capacitor 312. As a result, as shown in FIG. 17, a triangular wave voltage having a certain period T is generated at the non-inverting input terminal of the operational amplifier 310, and a rectangular wave voltage is generated at the output terminal and input to the drive unit 30. As shown in FIG. 16, the magnitude of the charge / discharge current of the oscillating unit 31 is determined by the sum of the current Ir flowing through the resistor 311 and the current Isw flowing from the oscillating unit 31 to the voltage control unit 6, and the oscillation period T and thus the operation Affects frequency.

Since the FET of the oscillating unit 31 is a semiconductor element, the conduction resistance Ron between the drain and the source has temperature characteristics, and the conduction resistance Ron decreases as the temperature increases. That is, even if the control voltage Vf of the voltage control unit 6 is constant, the magnitude of the charging / discharging current of the oscillation unit 31 varies depending on the ambient temperature Ta. That is, as shown in FIG. 18, the charging / discharging current increases and the oscillation period T decreases as the ambient temperature Ta increases, and conversely, the charging / discharging current decreases and the oscillation period T increases as the ambient temperature Ta decreases. Therefore, the FET of the oscillation unit 31 works as the temperature detection unit 5. The switching elements 10a and 10b are driven by the oscillation period T. When the oscillation period T is increased, the operating frequency finv of the high-frequency voltage Vcoil is increased, and when the oscillation period T is decreased, the operating frequency finv is also decreased. When actually measuring the relationship between the output voltage Vset of ambient temperature Ta and the inverter circuit 1 when the output voltage Vset is negative temperature coefficient (α ≒ -2000ppm / ℃) next as shown in FIG. 19, the same tendency as the basic form And has a substantially parallel relationship with the starting voltage Vign characteristic of the electrodeless discharge lamp L.

As described above, according to the present embodiment , the drive signal can be varied from the temperature characteristics of the semiconductor element, and the high frequency voltage Vcoil of the induction coil 2 when the ambient temperature Ta is low is higher than that at the high temperature. The startability of the electrodeless discharge lamp L can be improved at low temperatures, and the thermal stress on the circuit elements can be reduced at high temperatures.

  In addition, by forming a mirror circuit in the oscillating unit 31, the operating frequency of the oscillating unit 31 can be easily controlled by the current Isw from the oscillating unit 31 to the voltage control unit 6.

As a modification of the present embodiment , the oscillating unit 31 has a semiconductor element (FET, transistor, diode, etc.) in the charging / discharging current path in the oscillating operation, and the operating frequency increases as the ambient temperature Ta increases. Other configurations are possible. Even with such a configuration, the same effect as in the present embodiment can be obtained.

As another modification of the present embodiment , the oscillating unit 31 or the drive circuit 3 may be manufactured on an integrated circuit (IC). The oscillation unit 31 or the drive circuit 3 is a circuit that performs a low power operation, and the FET of the oscillation unit 31 that is also the temperature detection unit 5 can be simultaneously and easily fabricated on the integrated circuit. And cost reduction can be realized.

(Reference Example 3 )
Reference Example 3 is the same as the basic configuration in that it includes a DC power source E, an inverter circuit 1, an induction coil 2, a drive circuit 3, a voltage detection circuit 4, a temperature detection unit 5, and a voltage control unit 6. However, there are features described below that are not in the basic form . As shown in FIG. 20, the control voltage Vf of the voltage control unit 6 is applied to the control circuit 74 (see FIG. 1) of the DC power supply E, and the differential power supply operation of the operational amplifier 60 causes the DC power supply E (see FIG. 1). For example, the output voltage VDC (see FIG. 1) is controlled so that the output voltage VDC increases as the control voltage Vf decreases. The higher the output voltage VDC, the higher the high frequency voltage Vcoil converted by the inverter circuit 1.

As described above, according to this reference example , the high frequency voltage Vcoil of the induction coil 2 when the ambient temperature Ta is low is higher than that when the ambient temperature Ta is low. Therefore, the startability of the electrodeless discharge lamp L is improved when the ambient temperature Ta is low. In addition, the thermal stress on the circuit element can be reduced at high temperatures. Further, since the operating frequency finv of the high-frequency voltage Vcoil is constant, noise countermeasures can be facilitated.

It is a circuit diagram of the electrodeless discharge lamp lighting device of a basic form . It is a figure which shows the relationship between the operating frequency finv same as the above, and the high frequency voltage Vcoil. It is a figure which shows the relationship between the control voltage Vf same as the above, and the operating frequency finv. It is a figure which shows the relationship between ambient temperature Ta same as the above, and resistance value of the temperature sensitive resistance R1. It is a figure which shows the relationship between ambient temperature Ta same as the above, and control voltage Vf. It is a figure which shows a mode at the time of starting same as the above. It is a figure which shows the relationship between ambient temperature Ta same as the above, and the high frequency voltage Vcoil. It is a circuit diagram of the temperature detection part in the electrodeless discharge lamp lighting device of the reference example 1 , and a voltage control part. It is a figure which shows the relationship between ambient temperature Ta same as the above, and temperature-sensitive resistance or the resistance value of resistance. It is a figure which shows the relationship between ambient temperature Ta same as the above, and control voltage Vf. It is a figure which shows the relationship between ambient temperature Ta same as the above, and the high frequency voltage Vcoil. It is a circuit diagram of the temperature detection part in the electrodeless discharge lamp lighting device of the reference example 2 , and a voltage control part. It is a figure which shows the relationship between ambient temperature Ta same as the above, and the resistance value of resistance. It is a figure which shows the relationship between ambient temperature Ta same as the above, and control voltage Vf. It is a figure which shows the relationship between ambient temperature same as the above, and the high frequency voltage Vcoil. It is a circuit diagram of the electrodeless discharge lamp lighting device of an embodiment by the present invention. It is a figure which shows the input waveform of the non-inverting input terminal of an operational amplifier. It is a figure which shows the relationship between ambient temperature Ta same as the above, and the oscillation period T. FIG. It is a figure which shows the relationship between ambient temperature Ta same as the above, and the high frequency voltage Vcoil. It is a circuit diagram of the temperature detection part in the electrodeless discharge lamp lighting device of the reference example 3 , and a voltage control part. It is a circuit diagram of a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Inverter circuit 10a, 10b Switching element 3 Drive circuit 4 Voltage detection circuit 5 Temperature detection part 6 Voltage control part

Claims (1)

An induction coil that generates a high-frequency magnetic field for an electrodeless discharge lamp;
A power conversion circuit including a switching element and a resonance circuit for converting DC power into high-frequency power and supplying the high-frequency power to the induction coil;
A drive circuit that generates a drive signal for varying the on / off frequency of the switching element according to the magnitude of the control voltage and outputs the drive signal to the switching element;
A temperature detector whose output varies depending on the ambient temperature;
When the electrodeless discharge lamp is started, the magnitude of the control voltage is varied to control the drive circuit to vary the on / off frequency of the switching element, thereby varying the frequency of the high-frequency voltage, and thereby the magnitude of the high-frequency voltage. And a voltage control unit for varying
The drive circuit has a capacitor and oscillates by repeatedly performing a charge / discharge operation by the capacitor, and varies the frequency of the drive signal in accordance with the frequency of the output voltage from the oscillator. A drive unit that outputs to the switching element,
The oscillating unit includes an operational amplifier that compares a triangular wave voltage that is a charging voltage of the capacitor and is obtained by the charge / discharge operation with a reference voltage and outputs a rectangular wave voltage to the driving unit, and the temperature detection unit. And
The temperature detection unit is a mirror circuit composed of a semiconductor element whose conduction resistance changes with respect to a temperature change, and the temperature detection unit according to a magnitude of a control voltage of the voltage control unit and a change in conduction resistance of the semiconductor element. The temperature of the electrodeless discharge lamp is started by varying the charge / discharge current to the capacitor, changing the charge / discharge frequency of the capacitor by switching the charge / discharge of the capacitor according to the output of the operational amplifier. wherein Ru is varied the frequency of the high-frequency voltage by varying the frequency of the drive signal so as to increase the high-frequency voltage from the high temperature than at low temperature ambient temperature using an output of the detecting unit
An electrodeless discharge lamp lighting device comprising a call.

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