JP2004303512A - Discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To miniaturize a discharge lamp lighting device by reducing parts count constituting the device. <P>SOLUTION: A device for controlling lighting of a discharge lamp has an inverter circuit 30 of full bridge configuration. The polarity of output of the inverter circuit 30 is switched by first and third switching elements SW1, SW3 positioned on the high potential side of the inverter circuit 30. Second and fourth switching elements SW2, SW4 positioned on the low potential side are put in switching operation at higher frequency than the high potential side while performing PWM control. Electric energy supplied to the lamp L can thereby be regulated only by the inverter circuit 30. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device that controls lighting of a high-intensity discharge lamp such as a metal halide lamp, a high-pressure sodium lamp, and a mercury lamp.
[0002]
[Prior art]
High-intensity discharge lamps, such as metal halide lamps, high-pressure sodium lamps, and mercury lamps, do not light up when voltage is applied just like filament lamps, and they take time to reach a stable state. Requires a lighting device to control. This lighting device serves as a starter that creates a discharge path between the electrodes of the lamp and increases the current in the discharge path while maintaining the current in the discharge path to transition to arc discharge. And a role as a ballast for controlling the
[0003]
Generally, for example, as shown in FIG. 8, a lighting device includes a DC power supply 1, a converter 2 for adjusting DC power from DC power supply 1, an inverter 3 for converting the adjusted DC power to AC power, and a lamp. And an igniter 5 for shifting the discharge generated in 4 from glow discharge to arc discharge. The controller 6 is connected to the converter 2 and the inverter 3 to control the converter 2 and the inverter 3 respectively.
[0004]
The controller 6 supplies a gate control signal to the switching element Q1 of the converter 2, performs PWM (pulse width modulation) control on the input of the converter 2, converts the output to AC through the inverter 3, and converts the output to AC. 4 to control the power of the lamp 4.
[0005]
In recent years, there has been a demand in the market for electronic devices using high-intensity discharge lamps, such as projectors, OHPs, and automobile headlights, that are compact, lightweight, and low-cost, and lighting devices that control the lighting of high-intensity discharge lamps. There is a similar demand for One of the simple ways to reduce the size of the lighting device itself is to increase the switching frequency of the switching element Q1 of the converter 2. However, an increase in the switching frequency may cause an acoustic resonance phenomenon inherent to the lamp, so that it is necessary to consider matching with the lamp, and it is difficult to realize the switching frequency by using the converter circuit itself.
[0006]
Therefore, for example, in Japanese Patent Application Laid-Open No. 7-263166, in a full-bridge type inverter circuit, two arms are connected in parallel between a high potential side and a low potential side, and two arms are connected to one arm. One switching element switches the polarity of the output power of the inverter circuit at a low frequency to change the direction of the current, opens and closes the two switching elements connected to the other arm at a high frequency, and performs PWM control to perform output control of the output power. A configuration for adjusting the average value is disclosed. In this configuration, the output power adjustment conventionally performed by the converter can be performed by the inverter, so that the number of components constituting the lighting device can be reduced and the lighting device can be downsized.
[0007]
In addition, the high-intensity discharge lamp requires fine power control according to the instantaneous state of the lamp from the transition period immediately after the start of lighting of the lamp to the ballast. Therefore, normally, the voltage applied to the lamp is detected by inserting a resistor in parallel with the lamp and dividing the voltage, and the current flowing through the lamp is detected by inserting a minute resistor into the circuit of the lighting device. It was detected by conversion.
[0008]
[Patent Document 1] Japanese Patent Application Laid-Open No. 7-263166 (FIGS. 1 and 5)
[Non-Patent Document 1] Ninth Next Generation Energy Electronics Research Group Third Regular Research Group Preliminary Proceedings March 14, 2002 Japan Management Association [0009]
[Problems to be solved by the invention]
Normally, a switching element of an inverter circuit is formed of a semiconductor element such as a MOS-FET, and therefore, it is necessary to apply a predetermined voltage between a source and a gate of the MOS-FET for a switching operation. For example, in the inverter circuit described in Japanese Patent Application Laid-Open No. 7-263166, a switching element that performs PWM control may be located on a higher potential side with respect to a switching element that performs polarity switching depending on the direction of current flowing in the circuit. For the switching operation of the PWM control switching element, it is necessary to increase the potential of the gate signal of the MOS-FET by the input voltage as compared with the case where the gate signal is located on the lower potential side. For this reason, it is necessary to incorporate an insulation type pulse transformer, a high-side driver, and the like into the inverter circuit for the switching element for PWM control, so that the number of parts of the lighting device is increased as a whole, and the lighting device is increased in size.
[0010]
An object of the present invention is to provide a discharge lamp lighting device in which the number of components is reduced while maintaining the characteristics of a conventional lighting device in view of the above problems.
[0011]
[Means for Solving the Problems]
A discharge lamp lighting device according to claim 1 of the present invention is a discharge lamp lighting device for controlling lighting of a discharge lamp, wherein the high potential terminal connected to a high potential side of a power supply and the low potential side of the power supply are connected. And a control circuit for controlling the inverter circuit by converting DC power input through the low-potential terminal into AC power and outputting the AC power to the discharge lamp through first and second output terminals. And the inverter circuit has a full bridge configuration in which a first arm and a second arm are connected in parallel between the high potential terminal and the low potential terminal, and the first arm Has a first switching element on the high potential side and a second switching element on the low potential side, and the second arm has a third switching element on the high potential side and has a third switching element on the low potential side. Having a fourth switching element The first output terminal is located between the first switching element and the second switching element, and the second output terminal is connected to the third switching element and the fourth switching element. And the control circuit is configured to alternately open and close the first and third switching elements to determine the first frequency of the AC power, and to close the first switching element. Controlling the AC power by opening and closing the fourth switching element at a second frequency higher than the first frequency while maintaining the second and third switching elements open. When the third switching element is closed, the AC power is controlled by opening and closing the second switching element at the second frequency while maintaining the first and fourth switching elements open. And wherein the door.
[0012]
With the above structure, the inverter circuit can increase or decrease the output power by PWM control in addition to switching the polarity of the output voltage. Therefore, the size of the discharge lamp lighting device can be reduced, and the manufacturing cost can be reduced. it can. Further, the PWM control is performed alternately by the second and fourth switching elements, so that the heat of the circuit can be dispersed. Furthermore, in the full bridge configuration, the output polarity is switched at the first frequency by the high-potential side switching element, and the AC power is controlled by the low-potential side switching element, so that the driver required for power control can be simplified. Can be
[0013]
The discharge lamp lighting device according to claim 2 of the present invention is the discharge lamp lighting device according to claim 1, wherein the first voltage detection circuit detects an input voltage applied to the inverter circuit, and the inverter circuit And a second voltage detection circuit for detecting an output voltage output from the inverter circuit, wherein the control circuit detects the detected input voltage and the detected input voltage. An arithmetic circuit for calculating a discharge lamp current flowing through the discharge lamp using the detected current and the detected output voltage, wherein the AC power is controlled according to a value of the discharge lamp current. According to this configuration, the power supplied to the discharge lamp can be controlled with high accuracy by detecting the input / output voltage to the inverter circuit and the current flowing through the inverter circuit.
[0014]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the discharge lamp lighting device according to the present invention. 1, the discharge lamp lighting device 10 includes a power supply device 20, an inverter circuit 30, a low-pass filter circuit 40, a voltage detection circuit 50, a current detection circuit 60, and a controller 70. It is a device that is turned on and controlled. In the present invention, the lamp L refers to a high-intensity discharge lamp such as a metal halide lamp, a high-pressure sodium lamp, and a mercury lamp that emits light by discharging in metal vapor. Further, the discharge lamp lighting device 10 has an igniter and the like in addition to the illustrated members, but is omitted because it is not directly related to the present invention.
[0015]
The DC power supply device 20 includes, for example, a DC power supply, and applies a voltage V ₀ between the lines A and B. Note that the line B is used as a reference potential. Between the lines A and B, the capacitor C1 is connected, and smoothing the variation of the voltage V _0. Note that, as the DC power supply device 20, instead of a DC power supply, a power supply such as a commercial power supply that converts an alternating current into a direct current and outputs the DC smoothly may be used.
[0016]
The inverter circuit 30 is connected between the line A and the line B, converts the input DC voltage into a low-frequency voltage on which a rectangular high-frequency voltage is superimposed, and converts the DC voltage between the line C and the line D. Output. The inverter circuit 30 employs a full bridge configuration in which _two arms 31 ₁ and 312 are connected in parallel between a terminal M on a line A and a terminal N on a line B. The first arm 31 _1, is inserted first switching element SW1 is in the high potential side, the low potential side second switching element SW2 is inserted. The second arm 31 ₂ is inserted the third switching element SW3 is at a high potential side, the low potential side fourth switching element SW4 is inserted. Further, a line C is connected to a terminal O between the first switching element SW1 and the second switching element SW2, and a line D is connected to a terminal P between the third switching element SW3 and the fourth switching element SW4. Are connected, and an output appears between the line C and the line D. In this embodiment, the switching elements SW1 and SW2 are configured by transistors, and the switching elements SW3 and SW4 are configured by MOS-FETs. However, the switching elements SW1, SW2, SW3, and SW4 can be composed of appropriate semiconductor switching elements, and each has a body diode (not shown).
[0017]
In the inverter circuit 30, the diode D1 is inserted so that the anode is connected to the terminal O and the cathode is connected to the terminal M, and the diode D2 is connected so that the anode is connected to the terminal P and the cathode is connected to the terminal M. Has been inserted. The diodes D1 and D2 become commutation diodes when the second and fourth switching elements are turned off.
[0018]
Low pass filter circuit 40 includes an inductor L ₁ which is inserted in series with the line C, made from the connected capacitor C ₂ Metropolitan between the lines C and D, the low frequency power inverter circuit 30, which is high-frequency modulated outputs The high frequency modulation component is removed, and an appropriate low frequency rectangular voltage is output to the lamp L.
[0019]
The voltage detection circuit 50 includes a first voltage detection circuit 51 connected between the line A and the line B, and a second voltage detection circuit 52 connected between the line C and the line D. The first voltage detecting circuit 51 is provided on the input side of the inverter circuit 30, it detects an input voltage V _in of the inverter circuit 30. The first voltage detecting circuit 51, a resistor R1, R2 which are connected in series between the lines A and B, and the voltage V _in measured by resistors R1, R2 detected by dividing. On the other hand, the second voltage detection circuit 52 is provided on the output side of the inverter circuit 30 and detects the output voltage _Vout between the output terminals O and P of the inverter circuit 30.
[0020]
The current detection circuit 60 includes a resistor R3 inserted between the DC power supply device 20 and the inverter circuit 30 on the line D, and detects a current I flowing through the inverter circuit 30. The detection of the current I may be performed by the resistor R4 inserted in the line D on the input side of the inverter circuit 30.
[0021]
The controller 70 is mainly composed of a microcomputer, calculates the power supplied to the lamp L based on the outputs from the voltage detection circuit 50 and the current detection circuit 60, and outputs the result to the PWM driver 71.
[0022]
The PWM driver 71 outputs a gate pulse to each of the switching elements SW <b> 1 to SW <b> 4 of the inverter circuit 30, and switches the polarity of the AC power output from the inverter circuit 30 and performs PWM control. That is, the PWM driver 71 outputs the polarity switching pulses A and B for switching the polarity of the AC power output from the inverter circuit 30 to the first and third switching elements SW1 and SW3, and the inverter circuit 30 outputs. PWM gate pulses A and B for performing PWM control of the AC power are generated based on the output from the controller 70 and output to the second and fourth switching elements SW2 and SW4. The discharge lamp lighting device 10 is configured as described above.
[0023]
Next, the operation of the discharge lamp lighting device 10 will be described with reference to FIG. Discharge of the lamp L is started by an igniter circuit (not shown), and AC power is supplied from the inverter circuit 30 to continue lighting.
[0024]
The inverter circuit 30 switches the DC power from the DC power supply device 20 by switching the DC to AC by the switching operation of the first and third switching elements SW1 and SW3 on the high-potential side. The target AC power is supplied to the lamp L by performing PWM control of the output power by the switching operation of the second and fourth switching elements SW2 and SW4 on the potential side.
[0025]
The switching of the polarity of the inverter circuit 30 is performed at a low frequency such as 200 to 300 Hz. Therefore, the inverter circuit 30 so as to turn on the first and third switching elements SW1, SW3 on the high potential side of the full bridge circuit alternately, PWM driver 71, polarity switching pulse A as a period T ₀ , B. The switching frequency (1 / T ₀ ) of the polarity of the inverter circuit 30 is set to be considerably lower than the frequency at which the acoustic resonance phenomenon occurs in the lamp L.
[0026]
The PWM control is performed by changing the duty between the PWM gate pulse A supplied from the PWM driver 71 to the second switching element SW2 and the PWM gate pulse B supplied to the fourth switching element SW4. The cycle T ₁ of the PWM gate pulses A and B is the cycle of the rectangular wave high-frequency voltage superimposed on the low-frequency voltage of the cycle T ₀ output from the inverter circuit 30. Further, PWM gate pulse A, the period _{T 1} of the B is set much shorter than the period _{T 0} of the polarity switching. Further, PWM gate pulse A, in B, the ratio to the period T1 of the period _{T 2} in which the pulse level is high is duty. The duty is variable according to the output power of the inverter circuit 30, and the PWM driver 71 can appropriately change the duty according to the output from the controller 70.
[0027]
Next, PWM control and polarity switching in the inverter circuit 30 will be described in detail. As shown in FIG. 2, in the period A from time t ₁ to time t _2, the and polarity switching pulses B polarity switching pulse A is turned on is turned off, a period of between a time t ₄ from the next time t ₃ B Then, the polarity switching pulse A is turned off and the polarity switching pulse B is turned on. In the period T ₀ for one cycle includes the period A and period B, the polarity of the output power of the inverter circuit 30 is switched. Incidentally, for example, the period C between the time t ₂ of the period A and the period B, such as the time t ₃ is an dead time period provided for reliably forming the switch I ing operation of each switch I ing element SW1~SW4 Then, the supply of all the pulses to each of the switching elements SW1 to SW4 is stopped. The period C is a part of the period T _0, the period A, because it is set quite short when compared to the length of B, since no problem in practice almost ignored, following the period C is negligible I will do it.
[0028]
For example, in the period A starting from time _{t 1,} the PWM driver 71, the polarity switching pulse A is supplied to the first switching I ing element SW1, first switch I ing element SW1 is turned on, the fourth switch I ing element SW4 is It is turned on / off at a high frequency by the PWM gate pulse B. That is, the second and third switches I ing elements SW2, SW3 are kept off, the first switch I ing element SW1 switching operation of the fourth switching element SW4, while maintaining the ON state is performed in the period T ₁ ( (See FIGS. 2A to 2D). Therefore, in the period A, the current path shown in FIG. Therefore, current _{I A} from the terminal M, the first switching element SW1, the terminal O, the inductor L1, the lamp L, the terminal P, flows in the order of the fourth switching element SW4.
[0029]
3, when the fourth switch I ing element SW4 is turned on, the same voltage as the voltage V _in applied to the inverter circuit 30 is output from the inverter circuit 30, is applied to the lamp L as a lamp voltage V _L . When the fourth switching element SW4 is turned off from this state, the diode D2 functions as a commutation diode. Accordingly, by changing the output power of the inverter circuit 30 by performing PWM control by the fourth switching element SW4, a lamp current corresponding to the target power can be supplied to the lamp L.
[0030]
Next, in the period B, the polarity switching pulse B is supplied from the PWM driver 71 to the third switching element SW3 to turn on the third switching element SW3, and the PWM gate pulse A is supplied to the second switching element SW2. And turned on and off at a high frequency. That is, the first and fourth switches I ing elements SW1, SW4 while maintaining the off, the third switching element SW3 switching operation of second switching I ing element SW2 turned on is performed in the period T ₁ (FIG. 2 (See (a) to (d)). Therefore, in the period B, the current path shown in FIG. That is, when the third switching element SW3 is turned on, current _{I B} from the terminal M, the third switching element SW3, the terminal P, the lamp L, inductor L1, terminal O, the order of the second switching element SW2 Flows.
[0031]
4, when the third switch I ing element SW3 is turned on, the voltage of the same magnitude as the voltage V _in applied to the inverter circuit 30 is output from the inverter circuit 30, voltages of opposite polarity than the period A It is applied to lamp _L as VL. When the second switching element SW2 is turned off from this state, the diode D1 functions as a commutation diode. Therefore, the lamp current corresponding to the target power can be supplied to the lamp L by changing the output power of the inverter circuit 30 by performing the PWM control by the second switching element SW2.
[0032]
As described above, in the inverter circuit 30, by the period A and the period B appear alternately, the lamp voltage V _L applied to the lamp, as shown in FIG. 2 (e), rectangular wave AC cycle T ₁ Voltage.
[0033]
With the above configuration, both the PWM control and the polarity conversion of the output power can be performed only by the inverter circuit 30, and the number of components constituting the discharge lamp lighting device 10 can be reduced. Further, the discharge lamp lighting device can be constituted by a simple circuit, which contributes to downsizing of the device and cost reduction.
[0034]
Further, by providing the switching elements SW2 and SW4 for performing the PWM control on the low potential side of the inverter circuit 30, the potential of the gate pulse supplied for the switching operation of the switching elements SW2 and SW4 is changed by the switching element. This eliminates the need to increase the potential at the site. Accordingly, the discharge lamp lighting device 10 does not require components conventionally used for increasing the potential of the gate pulse, such as an insulation type pulse transformer and a high-side driver. And the circuit constituting the discharge lamp lighting device 10 can be simplified.
[0035]
Further, since the PWM control of the output power is performed alternately by the first and third switching elements SW1 and SW3 in the inverter circuit 30, the power generated by the PWM control performed by the conventional one switching element is used. Since the loss is shared by the two switching elements, the load on one switching element can be reduced. Therefore, the heat loss of the power loss can be efficiently performed.
[0036]
Further, with the above-described circuit configuration, the conventional configuration has been divided into two parts: a reference potential of a control unit that performs PWM control of the converter, and a reference potential of a power control unit provided on the inverter circuit side. Instead of the two-power-supply system of the electric light lighting device, a one-power-supply system with one reference potential can be adopted. Therefore, in the discharge lamp lighting device of the dual power supply type, the photocoupler which is necessary for transferring signals between the two control units can be eliminated. Thus, by setting the reference potential of the discharge lamp lighting device 10 at one place, the discharge lamp lighting device 10 can be easily configured.
[0037]
Next, the power control of the lamp L will be described in detail. In order to control the power of the lamp L to emit light at a desired luminance, the lamp voltage applied to the lamp L and the lamp current flowing through the lamp L are accurately detected, and the power of the lamp L is adjusted to the target power. Needs to be increased or decreased. Therefore, as shown in FIG. 5, in step S1, it detects the voltage V _in that is input by the voltage detecting circuit 51 to the inverter circuit, detects the current I _in which is input by the current detection circuit 60 to the inverter circuit 30 (See FIG. 2F). In step S2, calculating the input power _{P in} input to the inverter circuit 30 using the voltage _{V in} and the current _{I in} which is the detected (see FIG. 2 (g)). On the other hand, in step S3, the output voltage _Vout of the inverter circuit 30 is detected as a ramp L voltage by the voltage detection circuit 52 (see FIG. 2E). In the next step S4, by dividing the input power _{P in} the output voltage _{V out} to calculate the output current _{I out} of the inverter circuit 30.
[0038]
Next, in step S5, the output current I _out is compared with a target current value flowing through the lamp L. Then, in step S6, the duty of the PWM control is changed and the output power of the inverter circuit 30 is controlled in order to increase or decrease the lamp current according to the comparison result in step S5. As described above, while the lamp L is turned on, steps S1 to S6 are repeated until the lamp L is turned off (step S7) to control the power supplied to the lamp and adjust the lamp L to a desired brightness. And stabilize. Incidentally, when calculating the input power P _in, by taking into account the loss caused by the switching elements SW1~SW4 constituting the inverter circuit 30 in advance, it is possible to improve the accuracy of the power control.
[0039]
In the above operation, since the voltage detection circuit 52 can directly monitor the voltage applied to the lamp, the voltage detection circuit 52 can accurately detect an increase in the voltage of the lamp occurring at the end of the life of the lamp L. In this case, the power calculator 71 may be provided with a comparison circuit for comparing the detected lamp voltage with a predetermined voltage indicating the end of the lamp life, thereby outputting an alarm signal for notifying the user of the end of the lamp life. . Further, since the lamp voltage is directly monitored, the operation of the protection function such as the overvoltage protection function by the circuit in the discharge lamp lighting device 10 is also possible.
[0040]
In addition, since the output current I _out from the inverter circuit 30 to the lamp L is monitored while being calculated, a fine-grained power control from a transitional period when the lamp L is turned on to a stable period can be performed, Circuit failure caused by current can be prevented beforehand.
[0041]
Next, a second embodiment of the discharge lamp lighting device according to the present invention is shown in FIG. In this configuration, in the low-pass filter circuit 40, the inductors L ₁ and L ₂ are inserted into both the lines C and D. The configuration other than the low-pass filter circuit 40 is the same as that shown in FIG. 1, and the same reference numerals are given and the description thereof will be omitted. In the configuration shown in FIG. 6, since the inductor is divided into two parts, the entire lighting device can be reduced in size.
[0042]
Next, a third embodiment of the discharge lamp lighting device according to the present invention is shown in FIG. In this configuration, the low-pass filter circuit 40, by inserting the inductor L _1, L ₂ to the line C and D, in which further the inductor L _1, L ₂ are integrated by the magnetic path made of a magnetic material. The configuration other than the low-pass filter circuit 40 is the same as that shown in FIG. 1, and the same reference numerals are given and the description thereof will be omitted. In the configuration shown in FIG. 7, since the inductor is divided into two parts, the entire lighting device can be reduced in size.
[0043]
As described above, the described embodiment controls the power supplied to the lamp L with high accuracy by using the input voltage and the input current to the inverter circuit 30 and the output voltage from the inverter circuit 30. is there. In addition to the above embodiment, the power supplied to the lamp L can be controlled only by the input voltage and the input current to the inverter circuit 30. Also, the power supplied to the lamp L can be controlled only by the input current and the output voltage to the inverter circuit 30.
[0044]
It should be noted that the above-described embodiment only exemplifies a part of the preferred embodiment of the present invention, and the present invention is not limited to the above-described configuration.
[0045]
【The invention's effect】
According to the discharge lamp lighting device according to the first aspect of the present invention, the inverter circuit switches the polarity of the output voltage and performs the PWM control of the output power. Can be reduced in size, and the manufacturing cost can be reduced. Further, the PWM control is alternately performed by the two switching elements, so that the heat of the circuit can be dispersed. Further, in the full bridge configuration, the polarity of the AC output is switched by the switching element on the high potential side, and the AC power output by the switching element on the low potential side is controlled, so that the switching operation of the switching element on the low potential side is performed. Necessary drivers can be easily configured.
[0046]
According to the discharge lamp lighting device of the second aspect of the present invention, the discharge lamp current flowing through the discharge lamp can be obtained by detecting the input / output voltage to the inverter circuit and the current flowing through the inverter circuit. In addition, the power supplied to the discharge lamp can be accurately controlled.
[Brief description of the drawings]
FIG. 1 is a configuration diagram showing one embodiment of a discharge lamp lighting device according to the present invention.
FIG. 2 is a time chart showing the operation of the discharge lamp lighting device shown in FIG.
FIG. 3 is a diagram of a current path formed in the inverter circuit 30 during a period A in which a first switching element SW1 is turned on.
FIG. 4 is a diagram of a current path formed in the inverter circuit 30 during a period B during which a third switching element SW3 is turned on.
FIG. 5 is a flowchart showing power control.
FIG. 6 is a configuration diagram showing a second embodiment of the discharge lamp lighting device according to the present invention.
FIG. 7 is a configuration diagram showing a third embodiment of the discharge lamp lighting device according to the present invention.
FIG. 8 is a configuration diagram showing a conventional discharge lamp lighting device.
[Explanation of symbols]
L Discharge lamp M High potential terminal N Low potential terminal O, P Output terminal SW1, SW3 High potential side switching element SW2, SW4 Low potential side switching element 10 Discharge lamp lighting device 30 Inverter circuit 31 ₁ First arm 31 ₂ Second Arm 50 voltage detection circuit 60 current detection circuit 70 control circuit

Claims (2)

A discharge lamp lighting device for controlling lighting of a discharge lamp,
DC power input through a high-potential terminal connected to the high-potential side of the power supply and a low-potential terminal connected to the low-potential side of the power supply is converted into AC power, and the first and second powers are supplied to the discharge lamp. An inverter circuit for outputting through an output terminal of the second circuit;
A control circuit for controlling the inverter circuit,
The inverter circuit has a full bridge configuration in which a first arm and a second arm are connected in parallel between the high potential terminal and the low potential terminal, and the first arm is connected to a high potential side. And a second switching element on a low potential side, and the second arm has a third switching element on a high potential side and a fourth switching element on a low potential side. Wherein the first output terminal is located between the first switching element and the second switching element, and the second output terminal is connected to the third switching element and the fourth switching element. Between the switching elements of
The control circuit includes:
Opening and closing the first and third switching elements alternately to determine a first frequency of the AC power,
When closing the first switching element, opening and closing the fourth switching element at a second frequency higher than the first frequency while maintaining the second and third switching elements open. Go to control the AC power,
When the third switching element is closed, the AC power is controlled by opening and closing the second switching element at the second frequency while maintaining the first and fourth switching elements open. A discharge lamp lighting device. A first voltage detection circuit that detects an input voltage applied to the inverter circuit;
A current detection circuit for detecting a current input to the inverter circuit;
A second voltage detection circuit that detects an output voltage output from the inverter circuit,
The control circuit includes an arithmetic circuit that calculates a discharge lamp current flowing through the discharge lamp using the detected input voltage, the detected current, and the detected output voltage, and according to a value of the discharge lamp current. The discharge lamp lighting device according to claim 1, wherein the AC power is controlled.

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