JP2003031385A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a discharge lamp from being extinct immediately after starting without complicating circuit constitution. SOLUTION: This discharge lamp lighting device is provided with a DC power supply L a DC-DC converting circuit 2 having a switching element 22 and turning the switching element 22 on/off periodically to convert the output of the DC power supply 1 into desired DC voltage and DC current required for lighting the discharge lamp 5; and an output control circuit 7 for controlling the on/off operation of the switching element 22 so that the output of the DC-DC converting circuit 2 becomes a value required for starting and lighting the discharge lamp 5. The output control circuit 7 is provided with a starting assistance period for controlling the output of the DC-DC converting circuit 2 to the level of not causing extinction of the discharge lamp 5 without performing feedback control. Since the output of the DC-DC converting circuit 2 is thus adjusted according to a current command value Ip0, the extinction of the discharge lamp 5 caused by the output lowering of the DC-DC converting circuit 2, immediately after starting can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge lamp lighting device, and more particularly to a discharge lamp lighting device for lighting a high intensity discharge lamp (HID) such as a metal halide lamp.

[0002]

2. Description of the Related Art In order to light a high-intensity discharge lamp such as a metal halide lamp, it is necessary to apply a high starting voltage. After lighting, several hundreds of hours are required to prevent an acoustic resonance phenomenon.
AC lighting is performed at a frequency of about z. A discharge lamp lighting device for lighting such a high-intensity discharge lamp is generally a DC-DC converter circuit for performing power conversion control, and a rectangular wave by inverting the output voltage of the DC-DC converter circuit. It is equipped with an inverter circuit that supplies the alternating current to the discharge lamp and an igniter circuit that generates a high-voltage pulse and applies it to the discharge lamp at the time of starting, and detects the voltage (lamp voltage) and current (lamp current) of the discharge lamp. In many cases, the DC-DC converter circuit is controlled to have constant power so that a predetermined power is supplied to the discharge lamp. However, there is a case where the DC-DC conversion circuit is current-controlled only for a predetermined time (for example, the time from the transition to arc discharge until the polarity inversion is performed twice by the inverter circuit) immediately after the start (JP-A-11-260584). (See Japanese Patent Publication).

Since the lamp voltage drops sharply immediately after starting, the response of the feedback control system of the DC-DC conversion circuit is delayed with respect to such a sudden load change, and an appropriate power is supplied to the discharge lamp. Could not be supplied to the discharge lamp, the light output of the discharge lamp became too small, and in the worst case, it might disappear.

[0004]

In the above-mentioned conventional example in which the constant voltage control and the current control for supplying the predetermined voltage to the discharge lamp by detecting the lamp voltage and the lamp current immediately after the discharge lamp is started, the feedback control system is used. Although the extinction is prevented by increasing the speed to some extent and shortening the response time, there is a problem that the configuration of the control circuit that performs the feedback control becomes complicated and expensive. In addition, in order to perform feedback control, a filter is required to reduce noise and ripple contained in the output, and when trying to make the response faster, the consistency when combined with the discharge lamp deteriorates, and due to oscillation phenomena, etc. The output might be unstable.

The present invention has been made in view of the above problems, and an object thereof is to provide a discharge lamp lighting device capable of preventing extinguishing of a discharge lamp immediately after starting without complicating the circuit configuration. To do.

[0006]

In order to achieve the above-mentioned object, the invention of claim 1 has a direct current power source and a switching element, and has a switching element to periodically turn on / off the switching element. Detects the output of the DC-DC converter circuit that converts the input voltage to the desired DC voltage and the output of the DC-DC converter circuit, and turns on the switching element so that the detected output has the value necessary for starting and lighting the discharge lamp. An output control circuit for controlling the ON / OFF operation, and the output control circuit does not perform feedback control based on the detection output of the DC-DC conversion circuit from the start of discharge of the discharge lamp to the rated lighting. It is characterized by having an auxiliary period.The output control circuit does not perform feedback control during the auxiliary starting period, and the discharge immediately after starting is performed without complicating the circuit configuration. Extinction can be prevented of.

According to a second aspect of the present invention, in the first aspect of the invention, the output control circuit is provided with a discharge start detecting means for detecting the discharge start of the discharge lamp based on the instantaneous value of the output of the DC-DC converter circuit. The discharge start detection that determines the timing of the transition to the start auxiliary period can be performed without delay, and the extinguishing of the discharge lamp immediately after the start can be further reliably prevented.

The invention of claim 3 is characterized in that, in the invention of claim 1, the starting auxiliary period in the output control circuit is set to a time which is not shorter than the response time during feedback control. The disappearance can be more surely prevented.

According to a fourth aspect of the present invention, in the first aspect of the present invention, the output control circuit turns on / off the switching element at a predetermined switching frequency and a predetermined on-duty ratio in the starting assist period. The same operation as that of the first aspect of the invention is achieved.

According to a fifth aspect of the present invention, in the fourth aspect of the invention, the input voltage detecting means for detecting the input voltage from the DC power supply is provided, and the output control circuit switches according to the input voltage detected by the input voltage detecting means. At least one of the switching frequency and the on-duty ratio of the element is variable, and it is possible to suppress the influence of fluctuations in the power supply voltage of the DC power supply and reliably prevent the extinction immediately after starting.

The invention of claim 6 is characterized in that, in the invention of claim 5, the output control circuit lowers the on-duty ratio of the switching element as the input voltage from the DC power source in the auxiliary start period increases, It is possible to prevent excessive electric power from being supplied to the discharge lamp and suppress deterioration of the discharge lamp and the circuit element.

According to a seventh aspect of the present invention, in the invention of the fifth aspect, the output control circuit increases the switching frequency of the switching element as the input voltage from the DC power source in the starting auxiliary period increases, and the output lamp is provided in the discharge lamp. It is possible to prevent excessive power supply and suppress deterioration of the discharge lamp and circuit elements.

According to an eighth aspect of the present invention, in the first aspect of the present invention, there is provided a time measuring means for measuring a time from turning off the discharge lamp to restarting the discharge lamp, and the output control circuit is provided with a switching element of a switching element as the time measuring time by the time measuring means becomes longer. Characterized by lowering the on-duty ratio, it is possible to reliably prevent the discharge lamp from extinguishing immediately after restart by suppressing the effect of the time from turning off the discharge lamp to restarting it, that is, the temperature of the discharge lamp.
It is possible to prevent excessive electric power from being supplied to the discharge lamp and suppress deterioration of the discharge lamp and circuit elements.

According to a ninth aspect of the present invention, in the first aspect of the invention, the output control circuit gradually increases the on-duty ratio of the switching element in the auxiliary start period with the passage of time, and responds to an increase in the voltage of the discharge lamp. In addition, it is possible to surely supply appropriate electric power, prevent the extinguishing immediately after the start-up, and prevent excessive electric power from being supplied to the discharge lamp to suppress deterioration of the discharge lamp and the circuit element.

According to a tenth aspect of the invention, in the invention of the ninth aspect, the output control circuit increases the on-duty ratio of the switching element in a stepwise manner, and has the same effect as the invention of the ninth aspect.

According to an eleventh aspect of the invention, in any one of the first to tenth aspects of the invention, a switching current detecting means for detecting a current flowing through the switching element and a switching current for generating a switching current command value for feedback control are provided. The switching element is turned on / off so as to compare the current value detected by the command value generation means and the switching current command value with the switching current command value.
The output control circuit includes drive signal generating means for generating a drive signal to turn off, and the switching current command value generating means sets the switching current command value in the starting auxiliary period to a predetermined value that is relatively larger than that during steady lighting. The same operation as the invention according to any one of claims 1 to 10 is achieved.

According to a twelfth aspect of the present invention, in the invention of the eleventh aspect, the switching current command value generating means gradually reduces the switching current command value over time, and excessive electric power is supplied to the discharge lamp. Can be prevented and deterioration of the discharge lamp and the circuit element can be suppressed.

According to a thirteenth aspect of the present invention, in the eleventh aspect of the present invention, the input voltage detecting means for detecting the input voltage from the DC power supply is provided, and the switching current command value generating means is the input voltage detected by the input voltage detecting means. It is characterized in that the switching current command value is changed in accordance with it, and the influence of fluctuations in the power supply voltage of the DC power supply can be suppressed to reliably prevent the extinction immediately after the start.

According to a fourteenth aspect of the invention, in the thirteenth aspect of the invention, the switching current command value generating means decreases the switching current command value as the input voltage from the DC power supply in the starting auxiliary period increases. It is possible to prevent excessive electric power from being supplied to the electric lamp and suppress deterioration of the discharge lamp and the circuit element.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 shows a circuit diagram of this embodiment, and FIG. 2 shows a waveform diagram for explaining the operation. In this embodiment, a discharge lamp lighting device that lights a high-intensity discharge lamp used for a headlight of an automobile is exemplified,
The invention is not limited to this, and the technical idea of the present invention can be applied to all discharge lamp lighting devices that light a discharge lamp.

The discharge lamp lighting device according to the present embodiment comprises a DC power source 1 composed of an automobile battery and a switching element 22.
And a DC- which converts the output of the DC power supply 1 into a desired DC voltage and DC current necessary for lighting the discharge lamp 5 by periodically turning on / off the switching element 22.
A direct current conversion circuit 2 and an inverter circuit 3 that converts the direct current output of the direct current-direct current conversion circuit 2 into a rectangular wave alternating current output by reversing the polarity and supplies it to a discharge lamp 5 composed of a high intensity discharge lamp such as a metal halide lamp. An igniter circuit 4 for applying a high-voltage pulse to start the discharge lamp 5, a booster circuit 6 for boosting the DC output of the DC-DC converter circuit 2 to supply a high voltage to the igniter circuit 4, and a DC-DC converter The switching element 22 detects the output of the circuit 2 and adjusts the detected output to a value necessary for starting and lighting the discharge lamp 5.
And an output control circuit 7 for controlling the on / off operation of.

The DC-DC converter circuit 2 includes a transformer 21 in which a series circuit of a primary winding and a switching element 22 is connected between both electrodes of a DC power source 1 via a lighting switch SW, and M.
A switching element 22 composed of an OSFET; a smoothing capacitor 23 having one end connected to a connection point between the drain of the switching element 22 and the primary winding and the other end connected to one end of a secondary winding of the transformer 21; The switching element has a well-known structure including an anode connected to the other end of the next winding and a diode 24 having a cathode connected to the source of the switching element 22 (negative electrode of the DC power supply 1). A desired DC voltage is obtained across the smoothing capacitor 23 by periodically turning on / off 22. Then, between the output terminals of the DC-DC conversion circuit 2, that is, the smoothing capacitor 23 and the switching element 2
The inverter circuit 3 is connected to both ends of the two series circuits via a ripple removing filter circuit 25 including an inductor 251 and a capacitor 252. Further, a detection resistor 26 for detecting the output current of the DC-DC conversion circuit 2 is inserted between the connection point of the capacitor 252 and the source of the switching element 22 and the inverter circuit 3. The DC-DC conversion circuit 2 is not limited to that of this embodiment, and may have a step-up / down type circuit configuration such as a buck-boost converter or a flyback converter.

The inverter circuit 3 turns on / off each of the switching elements 32 to 35 in accordance with a bridge circuit of four switching elements 32 to 35 formed of MOSFETs and a drive signal given from the output control circuit 7 as described later. A conventional well-known driver circuit 31 and two switching elements 32 at diagonal positions.
And 35 and 33 and 34 are alternately turned on / off in synchronism with each other to invert the polarity of the DC output of the DC-DC conversion circuit 2 and convert it into a rectangular wave AC output. However, although MOSFETs are illustrated as the switching elements 32 to 35, bipolar transistors or IGBTs may be used.

The booster circuit 6 comprises a conventionally well-known Cockcroft circuit in which a plurality of capacitors and diodes are combined, and boosts the output voltage of the DC-DC converter circuit 2 and supplies it to the igniter circuit 4. However, the configuration of the booster circuit 6 is not limited to the Cockcroft circuit, and may be one using a transformer or another configuration.

The igniter circuit 4 includes a discharge gap 41,
It is composed of a pulse transformer 42 and capacitors 43 and 44. One end on the primary side of the pulse transformer 42 is connected to the output end of the booster circuit 6 and the other end is connected to the discharge gap 4
1 is connected to one end of the discharge lamp 5, one end of the pulse transformer 42 on the secondary side is connected to the other end of the discharge lamp 5, and the other end of the secondary side is connected to the output end of the inverter circuit 3. To be done. The capacitor 43 is the pulse transformer 4
The primary side of 2 and the discharge gap 41 are connected in parallel, and the capacitor 44 is connected between the output terminals of the inverter circuit 3. Thus, the output of the booster circuit 6 causes the capacitor 43
When the voltage across both ends of the voltage rises to the discharge start voltage of the discharge gap 41, the discharge gap 41 becomes conductive and the charge stored in the capacitor 43 is discharged, and a high voltage pulse corresponding to the winding ratio is output to the secondary side of the pulse transformer 42. The high-voltage pulse is generated, and the discharge lamp 5 causes dielectric breakdown to start discharge.

The output control circuit 7 includes a control processing unit 8 including a microcomputer, a voltage detecting circuit 701 including an amplifier for detecting the output voltage of the DC-DC converting circuit 2,
A current detection circuit 7 which also includes an amplifier and detects the output current of the DC-DC conversion circuit 2 from the voltage drop of the detection resistor 26.
02 and the detection voltage of the voltage detection circuit 701 as the threshold voltage Vr1.
(Compared with a voltage higher than the lamp voltage during steady lighting and lower than the no-load voltage), the discharge start of the discharge lamp 5 is detected by detecting the discharge start of the discharge lamp 5 when the detected voltage exceeds the threshold voltage Vr1. A discharge start detection circuit 704 that outputs the signal LGT to the control processing unit 8 and a drive signal for driving the switching element 22 of the DC-DC conversion circuit 2 based on a PWM signal given from the control processing unit 8 as described later. To a primary winding of the transformer 21 of the DC-DC conversion circuit 2; a drive signal generation circuit 703 that generates a drive signal; a driver circuit 714 that receives a drive signal from the drive signal generation circuit 703 to turn on / off the switching element 22; Control from the first power supply circuit 712 that creates the operating voltage Vcc of the driver circuit 714 and the like by the voltage extracted from the provided intermediate tap, and the operating voltage Vcc The second power supply circuit 713, timer means serving extinguishing time detection circuit 7 which counts the time until the restart extinction of the discharge lamp 5 to create the operating voltage VDD of the processing section 8
09, a switching current detection circuit 708 that detects a current flowing in the switching element 22 (hereinafter referred to as a switching current), and a current command value that is output from the control processing unit 8 and determines a target value of the switching current as described later. A command value generation circuit 707 for converting a digital signal into an analog signal, and an analog current command value output from the command value generation circuit 707 are compared with a detection value of the switching current detected by the switching current detection circuit 708 to compare results. Comparator 7 for outputting the signal to the drive signal generation circuit 703
06, and an overvoltage detection circuit 705 that detects an overvoltage state of the output voltage by comparing the detection voltage of the voltage detection circuit 701 (voltage corresponding to the lamp voltage of the discharge lamp 5) with a predetermined threshold voltage Vth.

On the other hand, the control processing unit 8 calculates a command value (power command value) of the power supplied to the discharge lamp 5 according to each condition from start to lighting based on the data given in advance. A calculation unit 801, a current command value calculation unit 802 that calculates a current command value corresponding to the power command value from the power command value given from the power command value calculation unit 801, and the detected voltage detected by the voltage detection circuit 701; Current command value calculator 8
02 and a current command value for PI control of ON / OFF operation of the switching element 22 so as to reduce the error between the current command value and the detected current detected by the current detection circuit 702. The error amplification calculation unit 803 for outputting and the switching frequency setting unit 806 for setting the switching frequency of the switching element 22.
And a PWM signal generator 808 that generates a PWM signal for turning on the switching element 22 at the switching frequency set by the switching frequency setting unit 806,
The PWM signal generation unit 808 is configured so that the ON time of the switching element 22 does not become longer than necessary and an excessive current does not flow.
A maximum on-duty setting unit 807 that sets a maximum on-duty, a start auxiliary period interrupt processing unit 804 that executes interrupt processing of a start auxiliary period described later, and an interrupt process by the start auxiliary period interrupt processing unit 804. Accordingly, the current command value setting unit 805 that sets the current command value Ip2 output from the error amplification calculation unit 803 to the current command value Ip0 for the auxiliary start period, and the turn-off time detection circuit 70 as described later.
9, a timer on / off unit 811 for outputting a timer on signal and a timer off signal, and a capacitor (not shown) included in the extinction time detection circuit 709 as described later.
Extinction time calculation unit 81 that calculates extinction time from the voltage across both ends of
0, an input voltage detection unit 809 that detects the input voltage Vin from the DC power supply 1, a polarity inversion time generation unit 813 that generates the polarity inversion time of the inverter circuit 3, and a polarity generated by the polarity inversion time generation unit 813. A drive signal generation unit 8 that generates a drive signal for turning on / off the switching elements 32 to 35 according to the inversion time and outputs the drive signal to the drive circuit 31.
14 and. The functions of the above-mentioned units are realized by executing a given program by a microcomputer. However, instead of using the microcomputer, each unit of the control processing unit 8 may be configured by hardware with circuit components.

Next, the operation of this embodiment will be described with reference to FIG. 2A is an input voltage Vin from the DC power source 1, FIG. 2B is a lamp voltage Vla applied to the discharge lamp 5, and FIG. 2C is a lamp current Ila flowing in the discharge lamp 5.
, And the respective detection values are input to the control processing unit 8.

First, the constant power control (steady mode described later) during steady lighting will be described. Power command value given from power command value calculation unit 801 and voltage detection circuit 70
The current command value corresponding to the power command value is calculated by the current command value calculation unit 802 based on the detected voltage detected in step 1, and the error amplification calculation unit 803 detects the current command value and the current detected by the current command value calculation unit 802. An error amplification calculation of the detected current detected by the circuit 702 is performed, and a current command value for PI control of the ON / OFF operation of the switching element 22 is output so as to reduce the error between them. This current command value is converted from a digital signal to an analog signal in the command value generation circuit 707 and input to the + terminal of the comparator 706. The detection value of the switching current detected by the switching current detection circuit 708 is input to the-terminal of the comparator 706, and when the detection value exceeds the current command value, the output of the comparator 706 changes from the H level to the L level.

The drive signal generation circuit 703 generates a drive signal for turning on the switching element 22 in synchronization with the rising edge of the PWM signal output from the PWM signal generation unit 808 and outputs the drive signal to the driver circuit 714, and this drive is performed. The switching element 22 is turned on by the driver circuit 714 that receives the signal. The output of the comparator 706 is given to the drive signal generation circuit 703. When the output of the comparator 706 changes from the H level to the L level, the drive signal generation circuit 703 generates a drive signal for turning off the switching element 22. Output to the driver circuit 714, and the switching element 22 is turned off by the driver circuit 714 which receives the drive signal. That is, the output control circuit 7 feedback-controls the on-duty ratio of the switching element 22 so that the switching current flowing through the switching element 22 matches the current command value, and DC-DC so that constant power is supplied to the discharge lamp 5. The output of the conversion circuit 2 is adjusted. The drive signal generation circuit 703 is supplied with the output of the overvoltage detection circuit 705, and the detection voltage of the voltage detection circuit 701 is a predetermined threshold voltage V.
When the output of the overvoltage detection circuit 705 changes from the H level to the L level by exceeding th, the drive signal generation circuit 703 does not generate the drive signal for turning on the switching element 22, and when the discharge lamp 5 is turned off. The output voltage of the DC-DC converter circuit 2 is prevented from being excessively boosted when there is no load.

Next, the operation of starting the extinguished discharge lamp 5 to the rated lighting will be described. When the lighting switch SW is turned on and power is supplied from the DC power supply 1, the first power supply circuit 712 operates to generate the operating voltage Vcc, and the second power supply circuit 713 further changes the operating voltage Vcc to the operating voltage VDD. The control processing unit 8 is activated by creating it and supplying it to the control processing unit 8. Here, the control processing unit 8 controls the DC-DC conversion circuit 2 in the following four operation modes from the start of the discharge lamp 5 to the rated lighting.

1. Starting mode: a period T1 from the start of discharge of the discharge lamp 5 to lighting (arc discharge) (Equation 10)
Operation of 0 microseconds) 2. Initial lighting mode: operation of reversing the polarity of the lamp voltage twice after lighting (period T2 = 15 to 75 msec) 3. 3. Light output rising mode: operation of raising the light output of the discharge lamp 5 (period T3 = within about 60 seconds) 4. Steady mode: constant power control operation for supplying rated power to the discharge lamp 5 (period T4) In the start mode, the discharge lamp 5 is in the off state, so no load operation is performed, and the output control circuit 7 is the DC-DC conversion circuit 2 Output voltage is controlled to be a predetermined no-load voltage, the booster circuit 6 and the igniter circuit 4 operate, and a high voltage pulse is applied to the discharge lamp 5. By applying this high voltage pulse, the lamp voltage Vla rises to about 380 V (see FIG. 2B), and the discharge lamp 5 causes dielectric breakdown and starts discharge (glow discharge). When the discharge lamp 5 starts discharging, the output voltage of the DC-DC conversion circuit 2 sharply drops and the output current sharply increases. However, as described in the conventional example, the output adjustment of the DC-DC converter circuit 2 cannot follow the rapid load change due to the response delay of the feedback control by the output control circuit 7, and thus the discharge lamp 5 is suitable. Power may not be supplied.

Therefore, in this embodiment, the discharge start detection circuit 704 inputs the discharge start detection signal LGT to the control processing unit 8 and the discharge lamp 5 is lit (arc discharge). The period is referred to as a start auxiliary period, and the output control circuit 7 does not perform the feedback control during the start auxiliary period, and the switching element 22 is turned on / off at a predetermined switching frequency and on-duty ratio to output the DC-DC converter circuit 2. Is controlled to a level at which the discharge lamp 5 does not go out. That is, when the discharge start detection signal LGT is input, the auxiliary start period interrupt processing unit 804 executes the interrupt process of the auxiliary start period, controls the current command value setting unit 805, and outputs the current to the command value generation circuit 707. The command value is converted to the error amplification calculation unit 803.
The current command value Ip2 output from the current command value Ip0 for the auxiliary start period is changed, and the switching frequency setting unit 806 and the maximum on-duty setting unit 807 are controlled to start the frequency of the PWM signal and the maximum on-duty ratio. Set to a predetermined value for the supplementary period. At this time, the current command value Ip0 is set to a relatively large value within the allowable range.

Thus, during execution of the interrupt process by the auxiliary start period interrupt processing unit 804, the feedback control corresponding to the current command value Ip2 calculated by the error amplification calculation unit 803 is not performed, and the current command value Ip0 is set. Since the output of the DC-DC conversion circuit 2 is adjusted accordingly, the DC-
It is possible to prevent the discharge lamp 5 from extinguishing due to a decrease in the output of the DC conversion circuit 2. Moreover, there is an advantage that the circuit configuration does not become complicated because it is only necessary to provide the starting assist period in which the feedback control is not performed. It should be noted that it is desirable that the starting assistance period is at least not shorter than the response time in the feedback control.

Then, by a lighting discrimination circuit (not shown),
If it is determined that the discharge lamp 5 has changed from glow discharge to arc discharge (lighting of the discharge lamp 5) based on the comparison result of the average value of the detected voltage of the voltage detection circuit 701 and the predetermined value, the start auxiliary period interrupt When the processing unit 804 finishes the interrupt process, it controls the current command value setting unit 805 to control the command value generation circuit 707.
The current command value to be output to the current command value I for the auxiliary start period
The current command value Ip2 output from the error amplification calculation unit 803 is changed from p0, and feedback control is performed according to the current command value Ip2 calculated by the error amplification calculation unit 803.

Further, in this embodiment, the discharge start detection circuit 704 detects the discharge start of the discharge lamp 5 based on the instantaneous value of the output of the DC-DC conversion circuit 2 without depending on the lighting determination circuit, and the start auxiliary period. Since the interrupt processing of the interrupt processing unit 804 is executed, the discharge start detection for determining the timing of the transition to the start auxiliary period can be performed without delay,
It is possible to more reliably prevent the discharge lamp 5 from going out immediately after the start. The threshold voltage Vr1 is set to a voltage higher than the lamp voltage during steady lighting and lower than the no-load voltage.

By the way, at the time of restarting when the discharge lamp 5 that has been turned on is once turned off and then turned on again, the temperature of the discharge lamp 5 is high, so that at the time of initial starting (to the extent that the starting characteristics of the discharge lamp 5 are not affected. It is necessary to supply a larger amount of electric power than when the discharge lamp 5 is started from a state in which the discharge lamp 5 is sufficiently adapted to the ambient temperature, and normally the set value of the maximum on-duty at the time of restart is increased. However, when the set value of the maximum on-duty is simply increased, an unnecessarily large current may flow depending on the temperature of the discharge lamp 5 and excessive stress may be applied to the discharge lamp 5 and circuit components to deteriorate the discharge lamp 5. .

Therefore, in this embodiment, the extinguishing time is measured as a substitute for the temperature of the discharge lamp 5, and the set value of the maximum on-duty is lowered as the extinguishing time is longer (that is, the temperature of the discharge lamp 5 is lower). There is.

The extinguishing time detection circuit 709 described above is
It has a circuit configuration for charging / discharging a capacitor by an input voltage from the DC power source 1, and when the timer ON / OFF unit 811 of the control processing unit 8 receives a timer ON signal after the discharge lamp 5 is lit, the capacitor is charged and a lighting switch is lit. When the SW is turned off, the timer on / off unit 811 receives the timer off signal to discharge the capacitor. Then, when the lighting switch SW is turned on again, the turn-off time calculation unit 810 of the control processing unit 8 calculates the turn-off time from the voltage across the capacitor of the turn-off time detection circuit 709, and the turn-off time Tk obtained by the calculation is used as the start assistance. It is input to the period interrupt processing unit 804. The auxiliary start period interrupt processing unit 804 controls the maximum on-duty setting unit 807 to adjust the set value of the maximum on-duty according to the turn-off time Tk. For example, when the set value at the time of initial start is D2 and the set value in the situation where the turn-off time is almost zero is D1, the set value is set in the range of D1 to D2 according to the turn-off time Tk as shown in FIG. Decrease monotonically. Thus, in the present embodiment, the time from the extinguishing of the discharge lamp 5 to the restart (extinguishing time), that is, the discharge lamp 5
It is possible to prevent the discharge lamp 5 from extinguishing immediately after restarting by suppressing the influence of the temperature, and prevent the discharge lamp 5 and circuit elements from deteriorating by preventing an excessive current from flowing.

By the way, if the switching frequency and the on-duty ratio of the switching element 22 are constant, the output of the DC-DC converter circuit 2 varies according to the input voltage from the DC power supply 1, and the input voltage is relatively high. Under conditions where good starting performance is obtained, the input voltage may drop and cause extinction.On the contrary, under conditions where good starting performance is obtained when the input voltage is relatively low, it may be necessary due to an increase in input voltage. There is a possibility that excessive electric power is supplied to the discharge lamp 5 and the circuit elements, causing stress.

Therefore, in the present embodiment, an input voltage detection unit 809 for detecting the input voltage Vin from the DC power supply 1 is provided in the control processing unit 8, and the auxiliary start period interrupt processing unit 804 causes the switching frequency setting unit 806 and maximum ON. By controlling the duty setting unit 807 and adjusting at least one of the switching frequency and the maximum on-duty according to the input voltage Vin, the influence of fluctuations in the power supply voltage of the DC power supply 1 is suppressed. For example, the maximum on-duty setting value when the input voltage Vin is the lower limit value Vin1 of the use range is D
1. The input voltage Vin is the upper limit value Vin2 (> Vin1) of the usage range
When the set value at this time is D2, the set value may be linearly reduced in the range of D1 to D2 as the input voltage Vin increases as shown in FIG. Alternatively, when the setting value of the switching frequency when the input voltage Vin is the lower limit value Vin1 is F2 and the setting value when the input voltage Vin is the upper limit value Vin2 is F1, the input voltage Vin becomes high as shown in FIG. Accordingly, the set value may be exponentially increased in the range of F2 to F1.

Thus, in this embodiment, since the setting value of at least one of the switching frequency and the maximum on-duty is adjusted according to the input voltage Vin from the DC power supply 1, the fluctuation of the power supply voltage of the DC power supply 1 It is possible to reliably prevent the extinguishing immediately after the start by suppressing the influence of 1), and to prevent the discharge lamp 5 and the circuit element from deteriorating by preventing excessive electric power from being supplied to the discharge lamp 5.

(Embodiment 2) Since the circuit configuration of this embodiment is the same as that of Embodiment 1, illustration and description thereof will be omitted.
The present embodiment is characterized in that the output control circuit 7 gradually increases the set value of the maximum on-duty of the switching element 22 with the passage of time during the starting assist period.

That is, as shown in FIG. 6, in the starting assist period from the discharge start time t1 to the time t2 when the arc discharge is started and the constant power control is started, the lamp voltage Vla is reached.
Therefore, when the set value of the maximum on-duty is fixed, there is a possibility that the electric power and the current cannot be properly supplied to the discharge lamp 5. Therefore, in the present embodiment, the start assist period interrupt processing unit 804
Controls the maximum on-duty setting unit 807 to gradually increase the set value D of the maximum on-duty with the lapse of the start auxiliary period, thereby ensuring that the discharge lamp 5 is provided with appropriate power and current according to the rise of the lamp voltage Vla. Can be reliably supplied to the discharge lamp 5, and the discharge lamp 5 can be prevented from being extinguished immediately after the start, and the discharge lamp 5 and the circuit element can be prevented from being deteriorated by preventing excessive electric power from being supplied to the discharge lamp 5. . When the set value of the maximum on-duty is gradually increased, it may be increased stepwise in the range from the minimum value D2 to the maximum value D1 as shown in FIG. 7, or from the minimum value D2 to the maximum value as shown in FIG. The value D1 may be linearly and continuously increased.

(Third Embodiment) Since the circuit configuration of this embodiment is the same as that of the first embodiment, illustration and description thereof will be omitted.

By the way, in the first embodiment, the current command value Ip0 in the starting auxiliary period is fixed to a relatively large value within the allowable range, and the switching current is limited when an abnormality occurs in the discharge lamp 5 or the circuit, and the direct current is reduced. -DC converter circuit 2
Play a role in protecting However, as shown in FIG. 9, the lamp current Ila sharply increases immediately after starting, then largely decreases, and then gradually increases. Therefore, immediately after starting, the current command value Ip0 is set to a relatively large value. However, it is desirable to reduce the current command value Ip0 according to the level of the lamp current Ila immediately after the start even during the auxiliary start-up period from the viewpoint of protection in case of the above-mentioned abnormality.

Therefore, in the present embodiment, the current command value in the starting auxiliary period is gradually decreased with the passage of time, and an appropriate current command value is set according to the level of the lamp current Ila, so that an excessive current flows. This prevents deterioration of the discharge lamp 5 and circuit elements.

That is, in the no-load period (the period until the time t1 when the start of discharge is detected), the current command value setting unit 805.
Is set to the maximum value Ip0 of the current command value for the auxiliary start period, the start of discharge is detected, and the auxiliary start period ends from the time t1 when the interrupt process by the auxiliary start period interrupt processing unit 804 is executed. Until time t2, as shown in FIG. 9, the auxiliary start period interrupt processing unit 804 controls the current command value setting unit 805 to control the maximum value Ip0 to the minimum value Ip1 (=
It is monotonically decreased within the range of Ip2).

If the switching frequency and the on-duty ratio of the switching element 22 are constant as described in the first embodiment, the output of the DC-DC conversion circuit 2 changes according to the input voltage from the DC power supply 1. However, under conditions where good starting performance can be obtained with a relatively high input voltage, there is a possibility that it will disappear due to a drop in the input voltage. Conversely, good starting performance can be obtained with a relatively low input voltage. Under the condition, there is a possibility that excessive power is supplied more than necessary due to the increase of the input voltage and stress is applied to the discharge lamp 5 and the circuit elements. Therefore, also in the present embodiment, the start auxiliary period interrupt processing unit 804 causes the current command to be interrupted. The value calculator 802 is controlled to decrease the current command value as the input voltage Vin increases. For example, the current command value when the input voltage Vin is the lower limit value Vin1 of the use range is Ip
11, the input voltage Vin is the upper limit value Vin2 (> Vin1) of the use range
When the current command value at this time is Ip12 (<Ip11), the current command value is linearly reduced in the range from Ip11 to Ip12 as the input voltage Vin increases as shown in FIG.

By gradually decreasing the current command value as the input voltage Vin from the DC power source 1 rises, the influence of fluctuations in the power source voltage of the DC power source 1 is suppressed and the extinction immediately after the start is reliably prevented. At the same time, it is possible to prevent excessive electric power from being supplied to the discharge lamp 5 and suppress deterioration of the discharge lamp 5 and the circuit elements.

[0051]

According to the invention of claim 1, it has a DC power supply and a switching element, and the switching element is periodically turned on / off.
A DC-DC conversion circuit that converts the input voltage from the DC power supply to a desired DC voltage by turning it off, and the output of the DC-DC conversion circuit is detected and the detected output is the value necessary for starting and lighting the discharge lamp. Output control circuit for controlling the on / off operation of the switching element so that the output control circuit detects the output of the DC-DC conversion circuit from the start of discharge of the discharge lamp to the rated lighting. Since the output control circuit does not perform the feedback control during the auxiliary start period because it has the auxiliary start period that does not perform the feedback control based on the above, the extinction of the discharge lamp immediately after the start can be prevented without complicating the circuit configuration. effective.

According to the invention of claim 2, in the invention of claim 1, the output control circuit is provided with a discharge start detecting means for detecting the discharge start of the discharge lamp based on the instantaneous value of the output of the DC-DC converter circuit. The discharge start detection that determines the timing of the transition to the start auxiliary period can be performed without delay, and the extinguishing of the discharge lamp immediately after the start can be further reliably prevented.

According to the invention of claim 3, in the invention of claim 1, the starting auxiliary period in the output control circuit is set to a time not shorter than the response time at the time of feedback control, so that the discharge lamp immediately after starting is extinguished. There is an effect that it can be surely prevented.

According to a fourth aspect of the present invention, in the first aspect of the invention, the output control circuit turns on / off the switching element at a predetermined switching frequency and a predetermined on-duty ratio in the starting assist period. Has the same effect as.

According to a fifth aspect of the present invention, in the fourth aspect of the present invention, the input voltage detecting means for detecting the input voltage from the DC power source is provided, and the output control circuit switches according to the input voltage detected by the input voltage detecting means. Since at least one of the switching frequency and the on-duty ratio of the element is changed, there is an effect that the influence of the fluctuation of the power supply voltage of the DC power supply can be suppressed and the extinction immediately after the start can be surely prevented.

According to a sixth aspect of the present invention, in the fifth aspect of the invention, the output control circuit lowers the on-duty ratio of the switching element as the input voltage from the DC power source in the auxiliary start period increases, so that the discharge lamp is excessive. There is an effect that the supply of electric power can be prevented and the deterioration of the discharge lamp and the circuit element can be suppressed.

According to a seventh aspect of the invention, in the fifth aspect of the invention, the output control circuit increases the switching frequency of the switching element as the input voltage from the DC power source in the start-up assist period increases, so that excessive power is supplied to the discharge lamp. There is an effect that it is possible to suppress the deterioration of the discharge lamp and the circuit element by being prevented from being supplied.

According to an eighth aspect of the present invention, in the first aspect of the present invention, there is provided a time measuring means for measuring a time from turning off the discharge lamp to restarting the discharge lamp, and the output control circuit is provided with a switching element of a switching element as the time measuring means makes the time measuring longer. Since the on-duty ratio is reduced, it is possible to prevent the discharge lamp from extinguishing immediately after restart by suppressing the influence of the discharge lamp's time from the extinguishing of the discharge lamp, that is, the influence of the temperature of the discharge lamp. There is an effect that the supply of electric power can be prevented and the deterioration of the discharge lamp and the circuit element can be suppressed.

According to a ninth aspect of the present invention, in the first aspect of the invention, the output control circuit gradually increases the on-duty ratio of the switching element in the auxiliary start period with the passage of time. There is an effect that electric power can be surely supplied, extinguishing immediately after starting can be surely prevented, and excessive electric power is prevented from being supplied to the discharge lamp to suppress deterioration of the discharge lamp and the circuit element.

According to a tenth aspect of the invention, in the ninth aspect of the invention, the output control circuit increases the on-duty ratio of the switching element stepwise, and therefore, the same effect as that of the ninth aspect of the invention is exhibited.

According to an eleventh aspect of the present invention, in any one of the first to tenth aspects, a switching current detecting means for detecting a current flowing through the switching element and a switching current for generating a switching current command value for feedback control are provided. The switching element is turned on / off so as to compare the current value detected by the command value generation means and the switching current command value with the switching current command value.
The output control circuit is provided with a drive signal generating means for generating a drive signal to be turned off, and the switching current command value generating means sets the switching current command value in the starting auxiliary period to a predetermined value which is relatively larger than that during steady lighting. Items 1 to 1
The same effect as any of the inventions of 0 is exhibited.

According to a twelfth aspect of the present invention, in the invention of the eleventh aspect, the switching current command value generating means gradually reduces the switching current command value with the lapse of time, so that it is possible to prevent excessive electric power from being supplied to the discharge lamp. Therefore, there is an effect that the deterioration of the discharge lamp and the circuit element can be suppressed.

According to a thirteenth aspect of the present invention, in the eleventh aspect of the present invention, the input voltage detecting means for detecting the input voltage from the DC power source is provided, and the switching current command value generating means is the input voltage detected by the input voltage detecting means. Since the switching current command value is varied accordingly, the effect of fluctuations in the power supply voltage of the DC power supply can be suppressed, and there is an effect that it is possible to reliably prevent the extinction immediately after the start.

According to a fourteenth aspect of the present invention, in the thirteenth aspect of the present invention, the switching current command value generating means decreases the switching current command value as the input voltage from the DC power source in the starting auxiliary period becomes higher, so that the discharge lamp is excessive. There is an effect that it is possible to prevent the electric power from being supplied and to suppress the deterioration of the discharge lamp and the circuit element.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment.

FIG. 2 is a waveform diagram for explaining the above operation.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is an operation explanatory diagram of the above.

FIG. 5 is an operation explanatory diagram of the above.

FIG. 6 is a waveform diagram for explaining the operation of the second embodiment.

FIG. 7 is an operation explanatory diagram of the above.

FIG. 8 is an operation explanatory diagram of the above.

FIG. 9 is a waveform diagram for explaining the operation of the third embodiment.

FIG. 10 is an operation explanatory diagram of the above.

[Explanation of symbols]

1 DC power supply 2 DC-DC conversion circuit 3 inverter circuit 5 discharge lamp 7 Output control circuit 701 Voltage detection circuit 704 Discharge start detection circuit 8 Control processing unit 804 Start assistance period interrupt processing unit 805 Current command value setting unit

Continued front page    (72) Inventor Miki Otani             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company (72) Inventor Toshifumi Tanaka             1048, Kadoma, Kadoma-shi, Osaka Matsushita Electric Works Co., Ltd.             Inside the company F term (reference) 3K072 AA13 BA03 BB01 DA00 DD06                       DD10 DE02 DE04 DE06 EA06                       EA07 EB01 EB05 EB07 EB10                       FA05 GA03 GB18 GC04 GC05                       HA09 HA10 HB03                 5H730 AA15 AS11 BB43 BB57 DD04                       EE06 EE08 EE59 EE65 FD01                       FD11 FD31 FG05 FG07 FG23                       XC07

Claims (14)

[Claims] 1. A direct current power supply, a direct current-direct current conversion circuit for converting an input voltage from the direct current power supply into a desired direct current voltage by having a switching element and periodically turning on / off the switching element. The output control circuit includes an output control circuit that detects the output of the DC conversion circuit and controls the on / off operation of the switching element so that the detected output has a value necessary for starting and lighting the discharge lamp. A discharge lamp lighting device having a starting auxiliary period during which feedback control based on a detection output of a DC-DC conversion circuit is not performed from the start of discharge of a light to the rated lighting. 2. The discharge lamp lighting according to claim 1, wherein the output control circuit is provided with discharge start detection means for detecting the discharge start of the discharge lamp based on the instantaneous value of the output of the DC-DC conversion circuit. apparatus. 3. The discharge lamp lighting device according to claim 1, wherein the starting auxiliary period in the output control circuit is set to a time not shorter than a response time during feedback control. 4. The discharge lamp lighting device according to claim 1, wherein the output control circuit turns on / off the switching element at a predetermined switching frequency and a predetermined on-duty ratio in the starting auxiliary period. 5. An input voltage detection means for detecting an input voltage from a DC power supply is provided, and the output control circuit has at least one of a switching frequency and an on-duty ratio of a switching element according to the input voltage detected by the input voltage detection means. The discharge lamp lighting device according to claim 4, wherein one of the two is variable. 6. The discharge lamp lighting device according to claim 5, wherein the output control circuit lowers the on-duty ratio of the switching element as the input voltage from the DC power supply during the auxiliary start period increases. 7. The discharge lamp lighting device according to claim 5, wherein the output control circuit raises the switching frequency of the switching element as the input voltage from the DC power source increases during the auxiliary start period. 8. The time control means for measuring the time from the extinguishing of the discharge lamp to the restart thereof, wherein the output control circuit lowers the on-duty ratio of the switching element as the time measurement means lengthens. Item 1. The discharge lamp lighting device according to item 1. 9. The discharge lamp lighting device according to claim 1, wherein the output control circuit gradually increases the on-duty ratio of the switching element with the passage of time during the auxiliary start period. 10. The discharge lamp lighting device according to claim 9, wherein the output control circuit gradually increases the on-duty ratio of the switching element. 11. A switching current detecting means for detecting a current flowing through a switching element, a switching current command value generating means for generating a switching current command value for feedback control, and a current value detected by the switching current detecting means. The output control circuit is provided with drive signal generating means for generating a drive signal for turning on / off the switching elements so as to compare the switching current command values and make the two coincide with each other, and the switching current command value generating means performs switching in the starting auxiliary period. The discharge lamp lighting device according to claim 1, wherein the current command value is set to a predetermined value that is relatively larger than that during steady lighting. 12. The discharge lamp lighting device according to claim 11, wherein the switching current command value generating means gradually reduces the switching current command value with the passage of time. 13. An input voltage detecting means for detecting an input voltage from a DC power source is provided, and the switching current command value generating means varies the switching current command value according to the input voltage detected by the input voltage detecting means. The discharge lamp lighting device according to claim 11. 14. The discharge lamp lighting device according to claim 13, wherein the switching current command value generating means decreases the switching current command value as the input voltage from the DC power source in the auxiliary start period increases.