JPH11260576A - Electric power source and discharge lamp lighting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reliably start lighting of a discharge lamp again by quickly detecting extinction of the discharge lamp due to momentary disconnection and momentary electric power failure. SOLUTION: A d.c.-d.c. conversion circuit 1 converts an input voltage from a d.c. electric power source E to a desired d.c. voltage. A d.c.-a.c. conversion circuit 2 converts the d.c. voltage of the d.c.-d.c. conversion circuit 1 to an a.c. voltage with low frequency and supplies the a.c. voltage to a discharge lamp 4. An igniter circuit 3 applies high voltage to a discharge lamp 4 to start the discharge lamp 4. An input voltage detection part 5a detects the input voltage from the d.c. power source E and a lamp current detection part 5c detects the lamp current flowing in the discharge lamp 4. A reset circuit part 5e sends out an output to a reset signal to the d.c.-d.c. conversion circuit 1 and the d.c.-a.c. conversion circuit 2 when the detection value of the input voltage detection part 5a becomes a first threshold voltage or lower and the detection value of the lamp current detection part 5c becomes a threshold current or lower and shifts the state of the discharge lamp 4 to the normal lighting state at the time when the input voltage is recovered.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device having a discharge lamp as a load and a discharge lamp lighting device.

[0002]

2. Description of the Related Art A power supply circuit and a discharge lamp lighting device of this type include a power supply circuit for converting an input voltage from a DC power supply into an AC voltage and supplying the AC voltage to the discharge lamp, and a starting circuit for starting the discharge lamp. In the case where the discharge lamp goes out due to a drop in the voltage of the DC power supply, the discharge lamp is restarted after the input voltage from the DC power supply recovers (for example, see Japanese Patent Application Laid-Open No. 6-199981). .

In addition, the lighting state of the discharge lamp is detected from the lamp voltage of the discharge lamp, the input voltage from the DC power supply is detected, and the discharge lamp is turned off and the input voltage drops below a predetermined value. Some restarted the discharge lamp.

[0004]

In the former power supply device and discharge lamp lighting device, the control circuit monitors only the voltage value of the input voltage. When the discharge lamp goes out, the input voltage immediately returns to normal, so that an instantaneous power failure or an instantaneous power-off may not be detected, and the discharge lamp may not be restarted.

In the latter, since the lighting state is detected from the lamp voltage of the discharge lamp, it takes time to detect that the discharge lamp has extinguished, and it takes time to restart the discharge lamp. There was a problem of becoming long. Further, since it takes time to detect the extinguishing of the discharge lamp, a circuit for storing the fact that the input voltage has dropped is required, resulting in an increase in cost.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a voltage at which a discharge lamp extinguishes or an input voltage extinguishes due to an instantaneous power failure or instantaneous power cutoff. It is an object of the present invention to provide a power supply device and a discharge lamp lighting device capable of quickly detecting that the level has reached a level, resetting a circuit, and reliably switching the discharge lamp to normal lighting when the input voltage is restored.

[0007]

In order to achieve the above object, according to the first aspect of the present invention, there is provided a DC-DC conversion circuit for converting an input voltage from a DC power supply into a desired DC voltage,
A DC-AC conversion circuit that converts the DC voltage of the DC conversion circuit to a low-frequency AC voltage and supplies the discharge lamp to the discharge lamp, an igniter circuit that applies a high voltage to the discharge lamp to start the discharge lamp, and a DC-DC conversion A control circuit for controlling the output of the circuit,
An input voltage detection unit that detects an input voltage from a DC power supply,
A lighting state detection unit that detects a lighting state of the discharge lamp from a lamp current flowing through the discharge lamp, and a detection value of the input voltage detection unit that becomes equal to or lower than the first threshold voltage due to an instantaneous power failure or an instantaneous power cut-off, and is turned on. When the state detection unit detects that the discharge lamp is turned off, the control circuit includes a reset circuit unit that resets the operation of the DC-DC conversion circuit and the DC-AC conversion circuit and shifts the discharge lamp to normal lighting when the input voltage is restored. Provided,
Since the operation of the DC-DC conversion circuit and the DC-AC conversion circuit is reset only when the input voltage from the DC power supply becomes equal to or lower than the first threshold voltage and the discharge lamp is turned off, both circuits are reset. If the operation is not reset carelessly and the input voltage drops and the discharge lamp goes out, both circuits can be reset reliably.
The discharge lamp can be reliably shifted to normal lighting. Furthermore, the lighting state of the discharge lamp is detected from the lamp current, and when the discharge lamp is turned off, the lamp current does not flow. Circuit operation can be quickly reset even when the error occurs.

According to a second aspect of the present invention, in the first aspect of the present invention, the lighting state detector detects that the discharge lamp has been turned off since the lamp current becomes equal to or less than a predetermined threshold current.
Since the lamp current stops flowing when the discharge lamp is turned off, the lamp current becomes equal to or lower than the threshold current, so that the turn-off of the discharge lamp can be detected in a short time. The circuit can be reliably reset even when the power goes off and the power goes off.

According to a third aspect of the present invention, in the first aspect of the present invention, the reset circuit is configured such that, when the detection value of the input voltage detection section becomes equal to or less than the second threshold voltage, the reset circuit section is irrespective of the lighting state of the discharge lamp. -Since the operations of the DC conversion circuit and the DC-AC conversion circuit are reset, if the input voltage fluctuates due to an instantaneous power failure or instantaneous power cut, the operations of the DC-DC conversion circuit and the DC-AC conversion circuit are reset. be able to.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the reset circuit changes the second threshold voltage according to the lighting time. The second threshold voltage is changed according to the input voltage from the DC power supply, and the second threshold voltage is changed according to the lighting time and the input voltage. Erroneous operation of the reset circuit unit due to the fluctuation of

According to a sixth aspect of the present invention, in the third aspect of the present invention, the reset circuit section is lower than a voltage value at which the discharge lamp can maintain the lighting state even if the input voltage fluctuates due to an instantaneous power failure or an instantaneous power-off, In addition, since the second threshold voltage is set to a value larger than a voltage value at which the discharge lamp extinguishes due to a change in the input voltage due to an instantaneous power failure or an instantaneous power cut, when the input voltage fluctuates, The operation of the DC-DC converter and the DC-AC converter can be reset before the lamp goes out.

According to a seventh aspect of the present invention, in the first aspect of the present invention, the control circuit generates a control signal for controlling the output of the DC-AC conversion circuit, and turns on / off the input voltage from the DC power supply by the switching element. A power supply circuit comprising a chopper circuit for generating an operation voltage of the control circuit; wherein the switching element is turned on / off by a control signal output from the control circuit to a DC-AC conversion circuit; It is not necessary to separately provide a circuit for generating a control signal for turning on and off the circuit, and the circuit configuration can be simplified.

[0013]

Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) FIGS. 1 and 2 show circuit portions of a power supply device and a discharge lamp lighting device of this embodiment, and FIG. 3 shows a waveform diagram for explaining the operation.

The circuit includes a DC power supply E composed of a battery of, for example, a 12 V system or a 24 V system, a DC-DC conversion circuit 1 for converting an input voltage Vin from the DC power supply E into a desired DC voltage, A DC-AC conversion circuit 2 that converts a DC voltage of the conversion circuit 1 into a low-frequency AC voltage and supplies the discharge voltage to a discharge lamp 4 composed of a high-pressure discharge lamp such as a metal halide lamp, and discharges the power at the start of power supply to the discharge lamp 4. An igniter circuit 3 for starting the discharge lamp 4 by applying a high voltage to the electric lamp 4 to cause dielectric breakdown, and an appropriate voltage for the discharge lamp 4 in accordance with the detected values of the output voltage and output current of the DC-DC converter 1 Or a control circuit 5 for controlling the output of the DC-DC conversion circuit 1 so as to supply electric power, and is used, for example, as a lighting device for a vehicle-mounted headlight. Note that, as the DC power supply E, a DC voltage obtained by rectifying an AC power supply may be used. The DC-DC conversion circuit 1 may be a booster circuit, a step-down circuit, or a step-up / step-down circuit as long as the circuit generates a desired DC voltage.

The control circuit 5 includes an input voltage detector 5a for detecting an input voltage Vin of the DC power supply E from a voltage obtained by dividing the DC power supply E by a voltage dividing resistor, and a voltage divider for dividing the output voltage of the DC-DC converter circuit 1. It is connected to the output voltage of the DC-DC converter 1 from the voltage divided by the resistor, that is, the lamp voltage detector 5b for detecting the lamp voltage supplied to the discharge lamp 4, and the output line of the DC-DC converter 1. A lamp current detector 5c for detecting an output current of the DC-DC converter 1, that is, a lamp current Ila flowing through the discharge lamp 4 from a voltage generated in the current detection resistor; and a lamp voltage detector 5b and a lamp current detector 5c. An output control unit 5d for controlling the output of the DC-DC conversion circuit 1 according to the detected value, a detected value of the input voltage detecting unit 5a being equal to or lower than the first threshold voltage V1, and a lamp current detecting unit 5c Is detected When the output lamp current Ila becomes equal to or less than the threshold current I1, the operation of the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 is reset, and when the input voltage Vin is restored, the discharge lamp 4 is shifted to normal lighting. And a circuit section 5e. The lamp current detector 5c
Operates as a lighting state detector that detects the lighting state of the discharge lamp 4 from the lamp current Ila flowing through the discharge lamp 4,
Since the lamp current Ila has become equal to or less than the threshold current I1, the turning off of the discharge lamp 4 is detected.

Here, the input voltage Vin from the DC power supply E becomes equal to or lower than the first threshold voltage V1, and the lamp current Ila becomes equal to or lower than the threshold current I1. DC conversion circuit 1 and DC-AC conversion circuit 2
Is reset, the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 resume operation when the input voltage Vin returns, and supply of power to the discharge lamp 4 is started. At the same time, the igniter circuit 3 applies a high pulse voltage to the discharge lamp 4 to start the discharge lamp 4 and shift the discharge lamp 4 to normal lighting.

Next, the reset circuit section 5e will be described with reference to a specific circuit diagram shown in FIG. The detection value Va of the input voltage Vin detected by the input voltage detection unit 5a is equal to the resistance R1,
The voltage Vb divided by R2 and divided by the resistors R1 and R2 is input to the inverting input terminal of the comparator CP1. The reference voltage Vref1 is input to the non-inverting input terminal of the comparator CP1 via the resistor R3, and the non-inverting input terminal and the output terminal are connected via the resistor 4. The output terminal of the comparator CP1 is connected to a voltage V via a resistor R5.
The output of the comparator CP1 is input to one input terminal of the AND circuit AND1. Here, a hysteresis comparator circuit is constituted by the comparator CP1 and the resistors R3 to R5.
Is provided with hysteresis to prevent the output of the comparator CP1 from chattering. The voltage Ve of the non-inverting input terminal of the comparator CP1 is determined by the output voltage of the comparator CP1, the reference voltage Vref1, and the voltage dividing ratio of the resistors R3 and R4.
The voltage is set to a voltage corresponding to the first threshold voltage V1. Here, the input voltage Vin from the DC power supply E becomes equal to or lower than the first threshold voltage V1, and the detection value Va of the input voltage Vin is obtained.
Is lower than the voltage Ve corresponding to the first threshold voltage V1, the output of the comparator CP1 is inverted from low to high.

The detected value Vc of the lamp current Ila detected by the lamp current detector 5c is determined by a comparator CP.
2 inverting input terminals. The reference voltage Vref2 obtained by dividing the voltage Vcc by the resistors R6 and R7 is input to the non-inverting input terminal of the comparator CP2, the lamp current Ila becomes equal to or less than the threshold current I1, and the detection value Vc of the lamp current Ila becomes When the voltage falls below the reference voltage Vref2 corresponding to the threshold current I1, the output of the comparator CP2 goes high. The output terminal of the comparator CP2 is pulled up to the voltage Vcc via the resistor R8. Comparator CP2
Is input to one input terminal of an AND circuit AND2, and is also input to a delay circuit 5f including a resistor R9, a capacitor C1, and a NOT circuit NOT1.
The output of the delay circuit 5f is input to the other input terminal of the AND circuit AND2, and the output of the AND circuit AND2 is input to the other input terminal of the AND circuit AND1. Here, when the lamp current Ila falls below the threshold current I1, the output of the comparator CP2 is inverted from low to high, and the delay time determined by the time constant of the resistor R9 and the capacitor C1 after the output of the comparator CP2 is inverted. After the elapse, the output of the delay circuit 5f is inverted from high to low. Thus, during the period from when the output of the comparator CP2 is inverted from low to high until the delay time elapses, the AND circuit AND2
Output goes high. Therefore, when the input voltage Vin of the DC power supply E falls below the first threshold voltage V1 and the lamp current Ila falls below the threshold current I1, the output of the AND circuit 1, that is, the reset signal RST of the reset circuit 5e, is generated. Becomes high, and the DC-DC conversion circuit 1 and the DC-
The operation of the AC conversion circuit 2 is reset.

Here, the DC-DC conversion circuit 1 and the DC-DC
FIG. 3 shows a process for resetting the operation of the AC conversion circuit 2.
This will be described with reference to FIG. When an instantaneous power failure or instantaneous power cutoff of the DC power supply E occurs at the time t1, the input voltage Vin becomes equal to or lower than the threshold voltage V1, and the lamp current Ila decreases. When the lamp current Ila falls below the threshold current I1 and the discharge lamp 4 goes out, the output of the comparator CP2 is inverted from low (L) to high (H) as described above. When the output of the comparator CP2 is inverted from low to high, it is triggered by the output of the comparator CP2, a pulse signal whose time width is determined by the time constant of the resistor R9 and the capacitor C1 is output from the AND circuit AND2, and the DC signal is output from the AND circuit AND1. A reset signal RST is output to the DC conversion circuit 1 and the DC-AC conversion circuit 2, and the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 stop operating (that is, are reset). Thereafter, when the input voltage Vin of the DC power supply E returns, the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 start supplying power to the discharge lamp 4, and at the same time, the igniter circuit 3 applies a high-voltage pulse voltage to the discharge lamp 4. Is applied to start the discharge lamp 4 and shift the discharge lamp 4 to normal lighting.

On the other hand, if the lamp current Ila does not drop below the threshold current I1 when the input voltage Vin from the DC power supply E drops, the discharge lamp 4 is in a range where the lighting state can be maintained. The electric lamp 4 does not reach a point, and the reset circuit unit 5e does not output the reset signal RST. Therefore, the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 are inadvertently reset, and the discharge lamp 4 does not turn off. In particular, when the discharge lamp 4 is used for a vehicle headlight, the headlight is careless. The safety is improved without turning off the light.

As described above, the input voltage Vin from the DC power supply E becomes the threshold voltage V
1 and the lamp current Ila drops below the threshold current I1 only, the reset circuit 5e generates the reset signal RST, and the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 Of the discharge lamp 4 is surely detected and the input voltage V
At the return of in, the discharge lamp 4 can be reliably shifted to normal lighting. In addition, the reset circuit unit 5e generates the reset signal RST only when the input voltage Vin and the lamp current Ila become equal to or lower than the first threshold voltage V1 and the threshold current I1, respectively. Can be prevented. Further, since the lighting state of the discharge lamp 4 is detected from the lamp current Ila, the delay time until the disappearance of the discharge lamp 4 is detected is short. The operations of the DC conversion circuit 1 and the DC-AC conversion circuit 2 can be reliably reset, and the discharge lamp 4 can be switched to normal lighting when the input voltage Vin returns.

FIG. 4 is a circuit diagram of a power supply circuit for supplying operating power to the control circuit 5 described above. In the circuit of FIG. 4, the voltage dividing resistor and the current detecting resistor are omitted from the circuit shown in FIG. Further, in this circuit, the control circuit 5 outputs a control signal to each of the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2 to control the output of both circuits.

The power supply circuit 6 includes a step-up type chopper circuit 6a that generates a DC voltage Vdd by turning on and off an input voltage Vin (for example, approximately 8 to 21 V) from a DC power supply E by a switching element Q1 composed of a MOSFET. The output voltage Vdd of the circuit 6a is converted into a desired DC voltage Vcc (for example, approximately 16 V) and supplied to the control circuit 5 by, for example, 3
It comprises a power supply IC 6b composed of a terminal regulator IC, and a chopper control circuit 6c for controlling ON / OFF of the switching element Q1. The chopper circuit 6a includes a series circuit including a choke coil L1 and a switching element Q1 connected between both ends of the DC power supply E, and a series circuit including a diode D1 and a capacitor C2 connected between both ends of the switching element Q1. Is done. When the switching element Q1 is turned on, a current flows through a path from the DC power supply E → the choke coil L1 → the switching element Q1 → the DC power supply E, and energy is accumulated in the choke coil L1. Next, when the switching element Q1 is turned off, the energy stored in the choke coil L1 is released when the switching element Q1 is turned on, and a current flows through a path of the choke coil L1, the diode D1, the capacitor C2, the DC power supply E, and the choke coil L1. The capacitor C1 is charged
A voltage Vdd obtained by boosting the DC voltage E across the capacitor C1.
Occurs.

The chopper control circuit 6c includes a comparator CP3 and an AND circuit AND3. The comparator CP3 calculates a voltage Vd obtained by dividing the output voltage Vdd of the chopper circuit 6a by the resistors R10 and R11 and a reference voltage Vd.
When the voltage Vd is higher than the reference voltage Vref3, the output of the comparator CP3 goes low. When the voltage Vd is lower than the reference voltage Vref3, the output of the comparator CP3 goes high. Comparator C
The output of P3 is input to one input terminal of the AND circuit AND3, and the other input terminal of the AND circuit AND3 is connected to the control circuit 5 for controlling the output of the DC-AC conversion circuit 2.
Is input. The output of the AND circuit AND3 is input to the control electrode of the switching element Q1 via the resistor R12, and the output of the AND circuit 3 turns the switching element Q1 on and off.

Here, when the voltage Vd obtained by dividing the output Vdd of the chopper circuit 6a is lower than the reference voltage Vref3, the output of the comparator CP3 becomes high, and the AND circuit AND
3 outputs a control signal S1 to the switching element Q1.
Is turned on / off by the control signal S1, and the chopper circuit 6
The output Vdd of a is boosted. On the other hand, when the voltage Vd obtained by dividing the output Vdd of the chopper circuit 6a is higher than the reference voltage Vref3, the output of the comparator CP3 becomes low, and no signal is output from the AND circuit AND3. At this time, the switching element Q1 does not operate, and the output of the chopper circuit 6a gradually decreases. However, since the power supply IC 6b converts the output of the chopper circuit 6a to a constant voltage, the power supply IC
6b can supply a stable voltage Vcc to the control circuit 5. Thus, the control signal S1 output from the control circuit 5 to control the output of the DC-AC conversion circuit 2
Is used to turn on and off the switching element Q1 of the chopper circuit 6a, so that there is no need to separately provide a circuit for generating a control signal for turning on and off the switching element Q1, and the circuit configuration of the chopper control circuit 6c is simplified. be able to. In the present embodiment, the control signal S1 output from the control circuit 5 for turning on and off the switching element of the DC-AC conversion circuit 2 is used to turn on and off the switching element Q1, but instead of the control signal S1. Alternatively, the control signal S2 output from the control circuit 5 to the DC-DC conversion circuit 1 to control the output of the DC-DC conversion circuit 1 may be used, and the same effect as described above can be obtained.

In this embodiment, the switching element Q
1 uses a MOSFET, but the switching element Q
For example, a bipolar transistor may be used. Also, 3
Instead of using the power supply IC 6b such as a terminal regulator, a discrete series regulator circuit may be used. (Embodiment 2) In the circuit of the first embodiment,
The input voltage V of the DC power source E due to a drop in battery voltage, etc.
When in falls below the second threshold voltage, the reset circuit unit 5e generates a reset signal RST regardless of the lighting state of the discharge lamp 4, and the DC-DC conversion circuit 1 and the DC-DC
The operation of the AC conversion circuit 2 may be reset. The basic circuit configuration and operation are the same as those in the first embodiment, and a description thereof will not be repeated.

Here, as shown in FIG. 5, the reset circuit section 5e sets the second threshold voltage V2 to the lighting time and the input voltage V2.
It changes according to in. When the power is turned on, the second threshold voltage V2 is set low so that chattering due to the reset operation does not occur.
Is prevented from malfunctioning. On the other hand, when stable, the reset circuit unit 5e sets the second threshold voltage V2 to the input voltage Vin.
Is set to a slightly lower voltage value. Here, the voltage value slightly lower than the input voltage Vin is lower than a voltage value at which the discharge lamp 4 can maintain the lighting state even when the input voltage Vin fluctuates due to an instantaneous power failure or an instantaneous power cut-off. The voltage value is set to a voltage value higher than a voltage value at which the discharge lamp 4 extinguishes due to a change in the input voltage Vin due to the power interruption. For example, when the input voltage Vin of the DC power supply E is approximately 12 V, and if the input voltage Vin fluctuates by 5 V or more due to a momentary interruption or momentary interruption, there is a possibility that the disappearance may occur, the second voltage is reduced to approximately 8 V by 4 V lower than 12 V. Set the threshold voltage V2. When the input voltage Vin is high, the reset circuit unit 5e outputs the second threshold voltage V in accordance with the detected value of the input voltage Vin.
The setting of the second threshold voltage V2 is changed from that of FIG. 5 when the input voltage Vin is low, and the setting of the second threshold voltage V2 is changed from that of FIG. Is prevented from malfunctioning.

Thus, even if the input voltage Vin drops due to an instantaneous power failure or an instantaneous power-off, if the input voltage Vin does not fall below the second threshold voltage V2 as shown in FIG. The reset circuit section 5e does not generate the reset signal RST. On the other hand, the input voltage Vin decreases due to an instantaneous power failure or an instantaneous power-off, and as shown in FIG.
When in becomes equal to or lower than the second threshold voltage V2, the reset circuit unit 5e generates a reset signal RST to reset the operations of the DC-DC conversion circuit 1 and the DC-AC conversion circuit 2, and the input voltage Vin becomes At the time of recovery, the discharge lamp 4 is shifted to normal lighting. In general, the second threshold voltage V
2 is set to a voltage higher than the first threshold voltage V1.

As described above, when the input voltage Vin drops below the second threshold voltage V2 due to an instantaneous power failure or an instantaneous power cut, the reset circuit unit 5e is reset before the discharge lamp 4 goes out. Since the signal RST is generated and the operations of the DC-DC converter 1 and the DC-AC converter 2 are reset, the discharge lamp 4 can be reliably switched to normal lighting when the input voltage Vin returns.

[0030]

As described above, the first aspect of the present invention relates to a DC-DC converter for converting an input voltage from a DC power supply into a desired DC voltage.
A DC conversion circuit, a DC-AC conversion circuit that converts the DC voltage of the DC-DC conversion circuit to a low-frequency AC voltage and supplies the AC voltage to the discharge lamp, and an igniter that applies a high voltage to the discharge lamp and starts the discharge lamp. Circuit, a control circuit for controlling the output of the DC-DC conversion circuit, an input voltage detection unit for detecting an input voltage from a DC power supply, and lighting for detecting a lighting state of the discharge lamp from a lamp current flowing through the discharge lamp. When the detection value of the input voltage detection unit becomes equal to or lower than the first threshold voltage due to the instantaneous power failure or instantaneous power cutoff and the lighting state detection unit detects that the discharge lamp is turned off, the DC-DC conversion is performed. Circuit and DC
A reset circuit for resetting the operation of the AC conversion circuit and shifting the discharge lamp to normal operation when the input voltage is restored, provided in the control circuit, so that the input voltage from the DC power supply falls below the first threshold voltage. The operation of the DC-DC conversion circuit and the DC-AC conversion circuit is reset only when the discharge lamp is turned off, so that the operations of both circuits are not inadvertently reset, and the input voltage is reduced. When the discharge lamp goes out due to the decrease, both circuits can be surely reset, and there is an effect that the discharge lamp can be surely shifted to normal lighting. Furthermore, the lighting state of the discharge lamp is detected from the lamp current, and when the discharge lamp is turned off, the lamp current does not flow. Thus, there is an effect that the operation of the circuit can be quickly reset even when the occurrence of the error occurs.

According to a second aspect of the present invention, the lighting state detecting section detects that the discharge lamp is turned off because the lamp current becomes equal to or less than a predetermined threshold current. When the discharge lamp is turned off, the lamp current stops flowing. Since the lamp current becomes equal to or less than the threshold current, it is possible to detect the turn-off of the discharge lamp in a short time. There is an effect that the circuit can be reset.

According to a third aspect of the present invention, when the detected value of the input voltage detecting section becomes equal to or lower than the second threshold voltage, the reset circuit section includes a DC-DC conversion circuit and a DC-DC converter regardless of the lighting state of the discharge lamp. Since the operation of the AC conversion circuit is reset, the operation of the DC-DC conversion circuit and the DC-AC conversion circuit can be reset when the input voltage fluctuates due to an instantaneous power failure or an instantaneous power cutoff. .

According to a fourth aspect of the present invention, in the reset circuit section, the second threshold voltage is changed according to a lighting time, and in the reset circuit section, the second threshold voltage is changed. Is changed in accordance with the input voltage from the DC power supply, and the second threshold voltage is changed in accordance with the lighting time and the input voltage. There is an effect that malfunction can be prevented.

According to a sixth aspect of the present invention, the reset circuit portion is lower than a voltage value at which the discharge lamp can maintain the lighting state even if the input voltage fluctuates due to an instantaneous power failure or an instantaneous power cut, and the instantaneous power failure or the instantaneous power supply is stopped. Since the second threshold voltage is set to a value larger than the voltage value at which the discharge lamp extinguishes due to the change of the input voltage due to the interruption, if the input voltage fluctuates, before the discharge lamp extinguishes This has the effect that the operations of the DC-DC converter and the DC-AC converter can be reset.

According to a seventh aspect of the present invention, the control circuit generates a control signal for controlling the output of the DC / AC conversion circuit, and turns on / off the input voltage from the DC power supply by a switching element, thereby controlling the operating voltage of the control circuit. A power supply circuit comprising a chopper circuit is provided.
It is turned on and off by a control signal output from the control circuit to the DC-AC conversion circuit.There is no need to separately provide a circuit for generating a control signal for turning on and off the switching element of the chopper circuit. There is an effect that it can be easily performed.

[Brief description of the drawings]

FIG. 1 is a circuit diagram illustrating a power supply device and a discharge lamp lighting device according to a first embodiment.

FIG. 2 is a main part circuit diagram of the same.

FIG. 3 is a waveform chart illustrating an operation of the above.

FIG. 4 is a main part circuit diagram of a power supply circuit used in the power supply circuit;

FIG. 5 is a diagram illustrating a relationship between a lighting time of a power supply device and a discharge lamp lighting device according to a second embodiment and a second threshold voltage.

FIGS. 6A and 6B are diagrams illustrating the operation of the above.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC-DC converter circuit 2 DC-AC converter circuit 3 Igniter circuit 4 Discharge lamp 5a Input voltage detection part 5c Lamp current detection part 5e Reset circuit part E DC power supply

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Akihiro Kishimoto 1048 Oaza Kadoma, Kadoma City, Osaka Inside Matsushita Electric Works, Ltd.

Claims (7)

[Claims] A DC-DC converter for converting an input voltage from a DC power supply into a desired DC voltage; and a DC for converting a DC voltage of the DC-DC converter into a low-frequency AC voltage and supplying the AC voltage to a discharge lamp. An input for detecting an input voltage from a DC power supply, including an AC conversion circuit, an igniter circuit for applying a high voltage to the discharge lamp to start the discharge lamp, and a control circuit for controlling an output of the DC-DC conversion circuit; A voltage detection unit, a lighting state detection unit that detects a lighting state of the discharge lamp from a lamp current flowing through the discharge lamp, and a detection value of the input voltage detection unit that falls below the first threshold voltage due to an instantaneous power failure or an instantaneous power cutoff. And a reset circuit for resetting the operation of the DC-DC converter and the DC-AC converter when the lighting state detector detects that the discharge lamp is turned off, and shifting the discharge lamp to normal lighting when the input voltage is restored. And control Power supply and a discharge lamp lighting apparatus, characterized in that provided on the road. 2. The power supply device and the discharge lamp lighting device according to claim 1, wherein the lighting state detection unit detects that the discharge lamp is turned off when the lamp current falls below a predetermined threshold current. And a reset circuit for controlling the operation of the DC-DC converter and the DC-AC converter when the detected value of the input voltage detector is equal to or lower than the second threshold voltage, regardless of the lighting state of the discharge lamp. The power supply device and the discharge lamp lighting device according to claim 1, wherein 4. The reset circuit according to claim 3, wherein the second threshold voltage is changed according to the lighting time.
The power supply device and the discharge lamp lighting device according to the above. 5. The power supply device and discharge lamp lighting device according to claim 3, wherein the reset circuit changes the second threshold voltage according to an input voltage from a DC power supply. 6. The reset circuit section has a voltage value which is lower than a voltage value at which the discharge lamp can maintain the lighting state even if the input voltage fluctuates due to an instantaneous power failure or an instantaneous power cut, and an input voltage of the input lamp due to an instantaneous power failure or an instant power loss. The power supply device and the discharge lamp lighting device according to claim 3, wherein the second threshold voltage is set to a value larger than a voltage value at which the discharge lamp extinguishes due to the fluctuation. 7. A control circuit generates a control signal for controlling an output of a DC-AC conversion circuit, and a chopper circuit for generating an operating voltage of the control circuit by turning on and off an input voltage from a DC power supply by a switching element. The switching element is provided with a DC-
The power supply device and the discharge lamp lighting device according to claim 1, wherein the power supply device and the discharge lamp lighting device are turned on / off by a control signal output to an AC conversion circuit.