JP4211022B2 - Discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a discharge lamp lighting device for lighting a discharge lamp by an inverter circuit.
[0002]
[Prior art]
FIG. 3 is a circuit configuration diagram of a conventional discharge lamp lighting device disclosed in, for example, Japanese Patent Laid-Open No. 9-320882.
In the figure, 21 is an AC power source, 22 is a diode bridge, 23 is an inverter circuit, 24 is a discharge lamp, 25 is a resistor, 26 is a Zener diode, 27 is a capacitor, 28 is an inverter control circuit, 29 is a diode, and 30 is a resistor. is there.
[0003]
Next, the operation will be described with reference to FIG.
When the AC power supply 21 is turned on, a voltage that is full-wave rectified by the diode bridge 22 is applied to the resistor 25. At this time, a current flows through the resistor 25, and the capacitor 27 is charged with a predetermined voltage by the constant voltage element of the Zener diode 26. Then, using the charge stored in the capacitor 27 as energy, the inverter control circuit 28 operates the inverter circuit 23 and the discharge lamp 24 is lit. When the discharge lamp 24 is lit, power necessary for the operation of the inverter control circuit 28 is supplied from a winding (not shown) provided in the inverter circuit 23, and the inverter control circuit 28 continues to operate.
[0004]
FIG. 4 is a circuit configuration diagram of another conventional discharge lamp lighting device disclosed in Japanese Patent Laid-Open No. 9-55296. In FIG. 4, the same or corresponding parts as those in FIG.
31 is a step-up converter, 32 is a step-up inductance, 33 is a capacitor, 34 is a voltage detection resistor, 35 is a step-down converter, 36 is a step-down inductance, 37 is a capacitor, 38 is a switching element, 39 is a polarity switching circuit, 40 Is a high voltage pulse generation circuit.
In the discharge lamp lighting device of FIG. 3, the power supply voltage necessary for the inverter control circuit 28 is generated from the windings in the inverter circuit 23. From the boost converter 31, the step-down converter 35, the bridge circuit 22 and the like of FIG. In the discharge lamp lighting device configured as described above, a control power supply voltage generation winding (not shown) is added to the boosting inductance 32 or the step-down inductance 36 to increase the boosting inductance 32 or the step-down inductance. When a high-frequency current flows through the induction inductor 36, a method of generating a control power supply voltage using a voltage generated in the control power supply voltage generation winding is used.
[0005]
[Problems to be solved by the invention]
In the conventional discharge lamp lighting device shown in FIG. 3, for example, even when the abnormality of the discharge lamp 24 is detected and the inverter circuit 23 is stopped, the inverter control circuit 28 must be operated in order to maintain the stopped state. I must. However, if the inverter circuit 23 stops, the power supply to the inverter control circuit 28 from the winding inside the inverter circuit 23 stops, so the power source of the inverter control circuit 28 must be supplied from the resistor 25. I must.
[0006]
At this time, for example, when the voltage of the AC power supply 21 is 200 V and 10 V and 20 mA are required as the power supply of the inverter control circuit 28, the full-wave rectified voltage of AC 200 V must be dropped to the vicinity of the voltage of the Zener diode 26 by the resistor 25. Don't be. The average voltage of the AC 200V full-wave rectified voltage is approximately 180V, and if this is reduced to the voltage 10V of the Zener diode 26, 180-10 = 170V must be dropped across the resistor 25. Since a current of 20 mA must be passed through the resistor 25, the value of the resistor 25 at this time is 170 V / 20 mA = 8.5 KΩ, and the power consumption is 3.4 W.
[0007]
If the current flowing through the resistor 25 is a short time immediately after the power is turned on, there is no problem even if a resistor having a rated power smaller than 3.4 W is used for the resistor 25, but the inverter circuit 23 is stopped due to protection or the like. When power is supplied from the resistor 25 to the inverter control circuit 28 for a long time, a resistor having a rated power capacity more than double is required in consideration of reliability and the like. That is, there is a problem that a resistor of 7 W has to be used, which increases the size of the resistor and consequently increases the size of the lighting device.
[0008]
Further, in the discharge lamp lighting device of FIG. 4 described above, the abnormality of the discharge lamp 24 is also obtained in the method of generating the control power supply voltage using the high frequency current flowing in the inductance 32 of the step-up converter 31 or the inductance 36 of the step-down converter 35. Is detected and the discharge lamp 24 is turned off, there is a problem that it becomes difficult to generate the control power supply voltage.
[0009]
That is, in the discharge lamp lighting device of FIG. 4, when a control power generation winding is added to the boosting inductance 32 of the boost converter 31 and a control power source is to be obtained from this, the discharge lamp 24 is returned to the discharge lamp 24 when an abnormality occurs. When the current is cut off, no current flows from the boost converter 31, so that the voltage of the capacitor 33 rises. When the voltage of capacitor 33 reaches a predetermined voltage, boost converter 31 stops. Thereafter, the voltage of the capacitor 33 is gradually discharged from the voltage detection resistor 34 and decreases. When the voltage drops to a predetermined voltage, the boost converter 31 starts operating again. However, since no current flows to the discharge lamp 24, the capacitor 33 is immediately charged to the predetermined voltage, and the boost converter 31 stops again. To do. Thus, since boost converter 31 operates intermittently, it becomes difficult to generate a control power supply voltage when boost converter 31 is not operating.
[0010]
In addition, when a control power supply voltage generation winding is added to the step-down inductance 36 of the step-down converter 35 in FIG. 4 and the control power supply voltage is to be obtained therefrom, the current to the discharge lamp 24 is interrupted in the event of an abnormality. In this case, current does not flow from the step-down converter 35 to the discharge lamp 24, so the control power supply circuit 28 tries to flow current and opens the switching element 38 to the maximum on-duty. However, when the voltage of the capacitor 37 is charged up to the output voltage of the boost converter 31, even if the switching element 38 is operated at the maximum on-duty, no current flows through the step-down inductance 36, and the control power supply voltage can be generated. Disappear. After that, only when the electric charge is discharged by the self-discharge of the capacitor 37 and the voltage of the capacitor 37 is lower than the output voltage of the boost converter 31, a current flows through the step-down inductance 36 to generate a control power supply voltage. The capacitor 37 is immediately charged and no current flows again. Therefore, the step-down converter 35 operates intermittently in the same manner as in the case of obtaining the control power supply voltage by adding a winding for generating the control power supply voltage to the boosting inductance 32 of the boost converter 31. It becomes difficult to generate the control power supply voltage when the converter 35 is not operating.
[0011]
The present invention was made to solve the above problems, and even when the discharge lamp is detected and power supply to the discharge lamp is stopped, it is not necessary to generate a control power supply voltage from the resistor. An object of the present invention is to obtain a discharge lamp lighting device capable of stably ensuring a control power supply voltage by continuously operating a converter.
[0012]
[Means for Solving the Problems]
A discharge lamp lighting device according to claim 1 of the present invention includes a boost converter that boosts a full-wave rectified voltage by turning on / off a switching element at a high frequency, and a winding for generating a control power supply voltage that is provided along with the inductance of the boost converter. DC voltage detection means provided between the output of the line and the boost converter, discharge lamp voltage detection means provided in the preceding stage of the polarity switching circuit for supplying low-frequency power to the discharge lamp, and discharge lamp current detection In a discharge lamp lighting device having a discharge lamp current detection means, a control power supply voltage generation circuit for generating a predetermined control power supply voltage from a voltage generated in a control power supply voltage generation winding, and a discharge lamp voltage detection means when the discharge lamp voltage or lamp current detecting means by the detected discharge lamp current out of a predetermined range, turns off the discharge lamp, the boost converter scan The on-duty of the switching element, the discharge lamp voltage or lamp current and a control circuit for less than the on-duty time within a predetermined range, the ON / OFF switching elements of the boost converter according to the reduced since the on-duty, The voltage output from the boost converter is discharged by the DC voltage detecting means, and the voltage is generated in the winding for generating the control power supply voltage.
According to a second aspect of the present invention, there is provided a discharge lamp lighting device that includes a boost converter that boosts the full-wave rectified voltage by turning on / off the switching element at a high frequency, and a DC voltage boosted by the boost converter. A step-down converter that limits the current supplied to the discharge lamp by turning it on / off at high frequency, a winding for generating a control power supply voltage provided along with the inductance of the step-down converter, and a discharge lamp voltage provided between the outputs of the step-down converter Control power supply voltage generation circuit for generating a predetermined control power supply voltage from a voltage generated in a control power supply voltage generation winding in a discharge lamp lighting device having a detection means and a discharge lamp current detection means for detecting a discharge lamp current If, detected by the detected discharge lamp voltage or lamp current detecting means by the discharge lamp voltage detecting means discharge lamp current out of a predetermined range If, along with turning off the discharge lamp, on the on-duty of the switching element of the step-down converter, the discharge lamp voltage or lamp current and a control circuit for less than the on-duty time within a predetermined range, which became the small The voltage output from the step-down converter is discharged by the discharge lamp voltage detecting means by turning on / off the switching element of the step-down converter by the duty, and the voltage is generated in the winding for generating the control power supply voltage. .
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Embodiment 1 FIG.
1 is a block diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention.
In FIG. 1, 1 is a commercial AC power supply, 2 is a diode bridge for full-wave rectification of the commercial AC power supply 1, and 3 is a boost converter for boosting a voltage that has been full-wave rectified by the diode bridge 2. The primary winding n1 and the secondary winding n2 are composed of an inductance 3a, a diode 3b, a switching element 3c, and a capacitor 3d. 4 is a step-down converter for controlling the current flowing to the discharge lamp 7, 5 is a polarity switching circuit for changing the polarity of the current flowing to the discharge lamp 7, 6 is a current detection resistor for detecting the current flowing to the discharge lamp 7, and 8 is a high-voltage pulse. A high-voltage pulse generation circuit 9 for generating and starting the discharge lamp 7 is a control power supply voltage generation circuit, which comprises a resistor 9a, a Zener diode 9b, diodes 9c and 9d, capacitors 9e and 9g, and a constant voltage IC 9f. 10 is a DC voltage detection circuit that detects a DC voltage boosted by the boost converter 3, 11 is a control circuit, 12 is a discharge lamp voltage detection circuit that detects a discharge lamp voltage, 13 and 14 are differential amplifiers, and 15 is the above-described differential amplifier. 3 is an on-duty limiting circuit for the switching element 3c of the boost converter 3.
[0014]
Next, the operation will be described with reference to FIG.
When the commercial AC power supply 1 is turned on, the voltage that has been full-wave rectified by the diode bridge 2 is applied to the resistor 9a of the control power supply voltage generation circuit 9, and a current flows through the resistor 9a. The element charges the capacitor 9g with a predetermined DC voltage. Then, the control circuit 11 starts to operate with the charging energy charged in the capacitor 9g.
[0015]
The control circuit 11 first starts the operation of the step-up converter 3 to step up the voltage that has been full-wave rectified by the diode bridge 2, and the stepped-up DC voltage is converted into a polarity via the step-down converter 4. It is converted into alternating current by the switching circuit 5 and applied to the discharge lamp 7. In this state, the control circuit 11 drives the high-pressure pulse generating circuit 8 to apply a high-pressure pulse for starting the discharge lamp 7 to light the discharge lamp 7.
[0016]
After the discharge lamp 7 is turned on, the control circuit 11 reads the discharge lamp voltage from the discharge lamp voltage detection circuit 12 and calculates a discharge lamp current value from which the electric power of the discharge lamp 7 becomes a predetermined power. The calculated current value is output to the differential amplifier 13 as a target current value. In the differential amplifier 13, the discharge lamp current detected by the current detection resistor 6 is compared with the target current value from the control circuit 11, and the step-down converter 4 is operated so that they coincide with each other. To control the current flowing through.
[0017]
Here, the operation of boost converter 3 will be described in detail.
The differential amplifier 14 switches the switching element 3c of the boost converter 3 so that the voltage of the capacitor 3d detected by the DC voltage detection circuit 10 becomes a target voltage value given from the control circuit 11 and the input has a high power factor. The switching operation is performed. When the switching element 3c is turned on, a current flows through the inductance 3a and energy is stored in the primary winding n1 of the inductance 3a. When the switching element 3c is turned off, the energy stored in the primary winding n1 of the inductance 3a is charged to the capacitor 3d via the diode 3b.
[0018]
The control circuit 11 outputs a target voltage value such that the output voltage of the boost converter 3 becomes a predetermined voltage to the differential amplifier 14. The differential amplifier 14 compares the target voltage value from the control circuit 11 with the output voltage of the boost converter 3 detected by the DC voltage detection circuit 10 so that the output voltage of the boost converter 3 becomes the target voltage value. The on-duty of the switching element 3c is determined. In the on-duty limiting circuit 15, the on-duty of the switching element 3c determined by the differential amplifier 14 is a predetermined value given from the control circuit 11 in order to prevent an excessive current from flowing through the switching element 3c. Limit so that it does not become more.
Since the on-duty limit circuit 15 is a protection circuit that prevents an excessive current from flowing through the switching element 3c, the on-duty limit circuit 15 is sufficiently larger than the on-duty value determined by the differential amplifier 14 when the normal discharge lamp 7 is stably lit. The on-duty determined by the differential amplifier 14 is not limited by the on-duty limiting circuit 15.
[0019]
On the other hand, the inductance 3a is provided with a secondary winding n2 for control power, and a transformer is constituted by the primary winding n1 and the secondary winding n2 of the inductance 3a. When current flows, a voltage is generated in the secondary winding n2. This voltage is smoothed by the diode 9d and the capacitor 9e of the control power supply voltage generation circuit 9, and a predetermined control power supply voltage is generated by the constant voltage IC9f. Since the control power supply voltage generated by the constant voltage IC 9f is slightly higher than the control power supply voltage generated by the resistor 9a, when the control power supply voltage is supplied from the constant voltage IC 9f, No current flows through the resistor 9a.
[0020]
That is, when the boost converter 3 is not operating when the power is turned on, the control power supply voltage of the control circuit 11 is supplied via the resistor 9a. However, when the boost converter 3 starts operating, the secondary winding is supplied. It is supplied from the line n2.
[0021]
When the discharge lamp voltage detected from the discharge lamp voltage detection circuit 12 or the discharge lamp current detected from the current detection resistor 6 is out of a predetermined range, the control circuit 11 causes the discharge lamp 7 to It is determined that there is an abnormality, the operation of the polarity switching circuit 5 is stopped, the supply of power to the discharge lamp 7 is stopped, and the discharge lamp 7 is turned off. At this time, the control circuit 11 sets the limit value given to the on-duty limit circuit 15 from the discharge lamp voltage detected from the discharge lamp voltage detection circuit 12 during normal discharge lamp lighting or from the current detection resistor 6. The detected discharge lamp current is set to a value smaller than the value when it is within a predetermined range.
[0022]
Thereby, when the abnormality of the discharge lamp is detected and the discharge lamp is turned off, the on-duty determined by the differential amplifier 14 is limited by the limit value given from the control circuit 11 by the on-duty limiting circuit 15. Therefore, the on-duty of the switching element 3c becomes small. As a result, the energy that the switching element 3c charges the capacitor 3d with a single switching is reduced, and in order to charge the target voltage value from the control circuit 11, a large number of times of switching is required. Since the voltage charged in the capacitor 3d is gradually discharged through the resistance of the DC voltage detection circuit 10, the energy stored in the primary winding n1 of the inductance 3a is reduced by limiting the on-duty to the capacitor 3d. The speed at which the capacitor 3d is charged is smaller than the speed at which the charged energy of the capacitor 3d is discharged through the resistance of the DC voltage detection circuit 10, and the boost converter 3 operates continuously. As a result, since a high-frequency current continuously flows through the inductance 3a, a high-frequency voltage is continuously generated also in the secondary winding n2, and the control power supply voltage is secured by the operation of the control power supply voltage generation circuit 9 described above. The
[0023]
Embodiment 2. FIG.
2 is a block diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention. In FIG. 2, the same or corresponding parts as those in the first embodiment are designated by the same reference numerals and description thereof is omitted.
In FIG. 2, 3 ′ is a step-up converter that steps up the voltage that has been full-wave rectified by the diode bridge 2, and 4 ′ is a step-down converter that controls the current that flows through the discharge lamp 7. It is composed of an inductance 4a composed of n1 and secondary winding n2, a diode 4b, a switching element 4c, and a capacitor 4d. Reference numeral 15 'denotes an on-duty limiting circuit for the switching element 4c of the step-down converter 4'.
In the first embodiment, the secondary winding n2 for generating the control power supply voltage is provided in the inductance 3a of the boost converter 3. However, in the present embodiment, the control power supply voltage is generated in the inductance 4a of the step-down converter 4 ′. Secondary winding n2 is provided.
[0024]
Since the basic operation is the same as that of the first embodiment, the description thereof will be omitted, and the operation of the step-down converter 4 ′ will be mainly described.
When the switching element 4c of the step-down converter 4 'is turned on / off at a high frequency, a current flows from the step-up converter 3' to the switching element 4c while the switching element 4c is on. The current flowing to the switching element 4 c is smoothed by the diode 4 b, the primary winding n 1 of the inductance 4 a and the capacitor 4 d and supplied to the discharge lamp 7. Increasing the on-duty of the switching element 4c increases the current supplied to the discharge lamp 7, and decreasing the on-duty decreases the current supplied to the discharge lamp 7.
[0025]
The control circuit 11 reads the discharge lamp voltage from the discharge lamp voltage detection circuit 12, and calculates a discharge lamp current value from which the power of the discharge lamp 7 becomes a predetermined power. The calculated current value is output to the differential amplifier 13 as a target current value. The differential amplifier 13 compares the target current value from the control circuit 11 with the discharge lamp current detected by the current detection resistor 6 so that the discharge lamp current becomes the target current. Determine the on-duty.
[0026]
In the on-duty limiting circuit 15 ′, the on-duty of the switching element 4 c determined by the differential amplifier 13 is given by the control circuit 11 in order to prevent an excessive current from flowing through the switching element 4 c. Limit to not exceeding the value.
Since the on-duty limiting circuit 15 ′ is a protection circuit that prevents an excessive current from flowing through the switching element 4c, the on-duty limiting circuit 15 ′ is larger than the on-duty value determined by the differential amplifier 13 when the normal discharge lamp 7 is stably lit. The on-duty determined by the differential amplifier 13 is not limited by the on-duty limiting circuit 15 '.
[0027]
On the other hand, the inductance 4a of the step-down converter 4 'is provided with a secondary winding n2 for generating a control power supply voltage, and a transformer is constituted by the primary winding n1 and the secondary winding n2 of the inductance 4a. Therefore, when a current flows through the primary winding n1, a voltage is generated at the secondary winding n2. This voltage is smoothed by the diode 9d and the capacitor 9e of the control power supply voltage generation circuit 9, and a predetermined control power supply voltage is generated by the constant voltage IC9f. Since the control power supply voltage generated by the constant voltage IC 9f is slightly higher than the control power supply voltage generated by the resistor 9a as in the first embodiment, the control power is supplied from the constant voltage IC 9f. As a result, no current flows through the resistor 9a.
[0028]
That is, when the power is turned on, the control power supply voltage of the control circuit 11 is supplied through the resistor 9a, but when the step-down converter 4 'starts operation, the secondary winding n2 is turned on as in the first embodiment. Supplied.
[0029]
When the discharge lamp voltage detected from the discharge lamp voltage detection circuit 12 or the discharge lamp current detected from the current detection resistor 6 is out of a predetermined range, the control circuit 11 indicates that the discharge lamp 7 is abnormal. Therefore, the operation of the polarity switching circuit 5 is stopped, the supply of power to the discharge lamp 7 is stopped, and the discharge lamp 7 is turned off.
At this time, the control circuit 11 sets the limit value given to the on-duty limit circuit 15 ′ from the discharge lamp voltage detected from the discharge lamp voltage detection circuit 12 during normal discharge lamp lighting, or from the current detection resistor 6. The detected discharge lamp current is set to a value smaller than the value when it is within a predetermined range.
[0030]
Thereby, when an abnormality of the discharge lamp is detected and the discharge lamp is turned off, the on-duty determined by the differential amplifier 13 is limited by the limit value given from the control circuit 11 by the on-duty limiting circuit 15 ′. Therefore, the on-duty of the switching element 4c becomes small. Thereby, the energy which switching element 4c outputs by one switching becomes small. That is, the speed at which the capacitor 4d is charged through the switching element 4c and the primary winding n1 of the inductance 4a is slower than the speed at which the charged charge of the capacitor 4d is discharged through the resistance of the discharge lamp voltage detection circuit 12. Thus, the voltage of the capacitor 4d is always lower than the output voltage of the step-up converter 3 ', and the step-down converter 4' operates continuously. As a result, since a high-frequency current continuously flows through the inductance 4a, a high-frequency voltage is continuously generated also in the secondary winding n2, and the operation of the control power supply voltage generation circuit 9 described above causes the same as in the first embodiment. A control power supply voltage is secured.
[0031]
【The invention's effect】
According to the discharge lamp lighting device of the present invention , when the discharge lamp voltage or the discharge lamp current is out of the predetermined range, the discharge lamp is turned off and the on-duty of the switching element of the boost converter is released. The voltage output from the boost converter is discharged by the DC voltage detection means and controlled by turning on / off the switching element by the on-duty when the lamp voltage or the discharge lamp current is smaller than the predetermined range. Since the voltage is generated in the winding for generating the power supply voltage, it is possible to obtain a discharge lamp lighting device capable of stably securing the control power supply voltage even when there is no load when the discharge lamp is turned off. In addition, it is not necessary to generate a control power source from a resistor as in the conventional case, the capacity of the resistor can be made relatively small, and the apparatus can be made compact.
In the discharge lamp lighting device according to claim 2 of the present invention, when the discharge lamp voltage or the discharge lamp current is out of the predetermined range, the discharge lamp is turned off and the on-duty of the switching element of the step-down converter is set. The discharge lamp voltage or discharge lamp current is made smaller than the on-duty when it is within a predetermined range, and the voltage output from the step-down converter is discharged by the discharge lamp voltage detecting means by turning on / off the switching element by the on-duty. At the same time, since the voltage is generated in the winding for generating the control power supply voltage, it is possible to obtain a discharge lamp lighting device that can stably secure the control power supply voltage even when there is no load when the discharge lamp is turned off. it can. In addition, it is not necessary to generate a control power source from a resistor as in the conventional case, the capacity of the resistor can be made relatively small, and the apparatus can be made compact.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a discharge lamp lighting device according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram showing a configuration of a discharge lamp lighting device according to Embodiment 2 of the present invention.
FIG. 3 is a block diagram showing a configuration of a conventional discharge lamp lighting device.
FIG. 4 is a block diagram showing a configuration of another conventional discharge lamp lighting device.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Commercial AC power supply, 2 Diode bridge, 3, 3 'step-up converter, 4, 4' step-down converter, 5 Polarity switching circuit, 6 Current detection resistor, 7 Discharge lamp, 8 High voltage pulse generation circuit, 9 Control power supply voltage generation circuit, DESCRIPTION OF SYMBOLS 10 DC voltage detection circuit, 11 Control circuit, 12 Discharge lamp voltage detection circuit, 13, 14 Differential amplifier, 15, 15 'On-duty limitation circuit.

Claims (2)

A boost converter that boosts the full-wave rectified voltage by turning on / off the switching element at a high frequency, a control power supply voltage generation winding provided along with an inductance of the boost converter, and an output of the boost converter A discharge lamp lighting device comprising DC voltage detection means, discharge lamp voltage detection means provided in a preceding stage of a polarity switching circuit for supplying low frequency power to the discharge lamp, and discharge lamp current detection means for detecting the discharge lamp current In
A control power supply voltage generation circuit for generating a predetermined control power supply voltage from the voltage generated in the control power supply voltage generation winding;
When the discharge lamp voltage detected by the discharge lamp voltage detection means or the discharge lamp current detected by the discharge lamp current detection means is out of a predetermined range, the discharge lamp is turned off, and the switching element of the boost converter A control circuit for making an on-duty smaller than an on-duty when the discharge lamp voltage or the discharge lamp current is within a predetermined range;
When the switching element of the boost converter is turned on / off by the reduced on-duty, the voltage output from the boost converter is discharged by the DC voltage detecting means, and a voltage is applied to the winding for generating the control power supply voltage. A discharge lamp lighting device characterized by being generated. A boost converter that boosts the full-wave rectified voltage by turning on / off the switching element at a high frequency, and a current that is supplied with a DC voltage boosted by the boost converter and that is supplied to the discharge lamp by turning on / off the switching element at a high frequency A step-down converter for limiting the voltage, a winding for generating a control power supply voltage provided along with the inductance of the step-down converter, a discharge lamp voltage detecting means provided between the outputs of the step-down converter, and a discharge lamp for detecting a discharge lamp current. In a discharge lamp lighting device having a lamp current detection means,
A control power supply voltage generation circuit for generating a predetermined control power supply voltage from the voltage generated in the control power supply voltage generation winding;
When the discharge lamp voltage detected by the discharge lamp voltage detection means or the discharge lamp current detected by the discharge lamp current detection means is out of a predetermined range, the discharge lamp is turned off, and the switching element of the step-down converter A control circuit for making an on-duty smaller than an on-duty when the discharge lamp voltage or the discharge lamp current is within a predetermined range;
By on / off of switching elements of the buck converter according to the reduced since the on-duty, with discharging by the discharge lamp voltage detecting means the voltage output from the step-down converter, the voltage to the windings of the control power supply voltage generation The discharge lamp lighting device characterized by generating.

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