JPH04184895A - Lighting circuit for vehicle discharge lamp - Google Patents

Abstract

PURPOSE:To prevent going-out of a discharging lamp by expanding an allowable range of D.C. current when the discharge lamp is started, and making an upper limit restriction strict during a fixed time after lighting. CONSTITUTION:Vo necessary for starting is ensured by raising an upper limit value of a duty cycle of a control pulse Ps of a control circuit 21 and relaxing an upper limit restriction of an output Vo of a DC pressure rise circuit 7 with an idle period control part 21 when battery 2 voltage is lower than a fixed value when a lamp is started in a lighting circuit 1. When lighting is made after that, this time, the upper limit of the duty cycle of the control pulse Ps is lowered and the upper limit restriction is made strict, power control below rated power with a supply voltage lowering detection circuit 18 is not performed until a given period elapses after lighting during a lamp unit condition is detected, and width of voltage drop of output in the D.C. pressure rise circuit 7 is restrained. Consequently going-out after once lighting is made can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION The lighting circuit for a vehicular discharge lamp of the present invention will be described in detail according to the following items.

A. Industrial field of application B. Outline of the invention C1. Prior art 6. Problems to be solved by the invention [Fig. 11] E0. Means for solving the problems F. Examples [Figs. 1 to 10] a. Overview of the configuration [Figure 1] a-1. Power supply system a-21 lighting control system a-31 circuit protection system. Circuit configuration of each part ['s2 to Figure 4] b-1. Power supply system [ Figure 2] b-1-a, DC booster circuit b-1-b, high-frequency booster circuit b-1-c, igniter circuit b-21 lighting control system [3rd section b-2-a Output voltage detection section b-2-b, output current detection section b-2-c, timer circuit b-2-d, PWM control section b-2-e supply voltage drop detection circuit b-2-f, lighting/non-lighting detection circuit b -2-g, Shutdown period control unit b-31 circuit protection system C'1i44 diagram] b-3-a, power cutoff relay circuit b-3-b, abnormality determination circuit b-3-c, output current abnormality detection Circuit C1 operation [Figures 5 to 10] c-1 lighting control operation c-1-a, when the input voltage is normal [Figures 5 to 8] c-1-b, when the input voltage drops [ FIG. 9, FIG. 10] c-1-b-1, Operation of idle period control section c-1-b-2
, Operation of supply voltage drop detection circuit C-21 Circuit protection operation [Figure 6] c-2-a, Protection operation by abnormality determination circuit c-2-b
, Operation 61 of Output Current Abnormality Detection Circuit G0 Effects of the Invention (A. Field of Industrial Application) The present invention relates to a novel lighting circuit for a discharge lamp for a vehicle. Specifically, in a lighting circuit for a discharge lamp for a vehicle equipped with a DC booster circuit for boosting the DC input voltage, the discharge lamp can be started even when the DC input voltage drops below a predetermined value, and the discharge lamp can be discharged. To provide a novel lighting circuit for a vehicular discharge lamp in which a lighting state is maintained even after the lamp is once turned on.

(B. Summary of the Invention) A lighting circuit for a vehicular discharge lamp according to the present invention is a lighting circuit for a vehicular discharge lamp that includes a DC boost circuit for boosting a DC input voltage and a control circuit for controlling the boost voltage. The circuit includes a DC input voltage drop detection circuit that detects when the DC input voltage has dropped below a predetermined value, a lighting state detection circuit that detects whether the discharge lamp is in a lighting state, and a DC input voltage detection circuit. Upper limit regulating means is provided for regulating the upper limit value of the output voltage of the DC booster circuit by receiving detection signals from the lighting state detection circuit and sending signals corresponding to these to the control circuit, and when starting the discharge lamp. When the upper limit regulation means is notified of the drop in DC input voltage by a signal from the DC input voltage drop detection circuit, the upper limit regulation means releases the upper limit value regarding the output voltage of the DC booster circuit until the discharge lamp is lit. The upper limit value is set to be larger than the upper limit value in a steady state after the lamp is turned on, thereby making it easier to start the discharge lamp, and after that, the upper limit regulating means is notified of the lighting of the discharge lamp by a signal from the lighting state detection circuit. In some cases, the upper limit regulating means regulates the upper limit value of the output voltage of the DC booster circuit to a value smaller than the upper limit value in the steady state of the discharge lamp until a predetermined period of time has elapsed. This is an attempt to maintain the lighting state by suppressing an abnormal drop in the output voltage of the booster circuit.

(C, Prior Art) Recently, small metal halide lamps have been attracting attention for use in automobiles as a light source to replace incandescent light bulbs, and the basic mechanism of the lighting circuit for these lamps is to light the lamp in a short time. In a steady state after lighting, it is necessary to maintain the power of the lamp at the rated power.

In this case, a DC power source is used as a power source for the lighting circuit, and the lighting circuit has a configuration such that, for example, after boosting the DC input voltage with a booster circuit, a DC-AC converter converts the DC input voltage into a sine wave or square wave AC voltage. It is known that the voltage is applied to the lamp after being converted to .

(D. Problem to be Solved by the Invention) [Figure 11] However, when the vehicle is placed in a low-temperature environment or the DC input voltage of the lighting circuit drops abnormally due to battery exhaustion, the performance of the lighting circuit decreases. There is a problem in that the lamp falls off, making it difficult to start the lamp.

Figure 11 schematically shows this situation.
"Sll" indicates the power on state (ONloFF),
'VoJ is the output voltage of the DC booster circuit, 'Vc J is the terminal voltage of a capacitor in the igniter circuit provided for starting the lamp, and 'IL J is the lamp current.

As can be seen from the figure, after the power is turned on, the output voltage vo rises, and when the inverter circuit for DC-AC conversion starts oscillating at the point indicated by arrow A, the voltage of VC rises.
As shown by arrow B, when VC reaches a threshold value (denoted as "vl"), a trigger pulse is generated to start the lamp.

Therefore, if the battery voltage is low, the output voltage of the inverter circuit will also be low, and the time required for VC to reach Vsl will become longer, causing a delay in the generation of the trigger pulse, or the spark gap element in the igniter circuit will not turn on and the trigger will not be activated. There is a possibility that the worst case scenario will occur where no pulse is generated. Further, since the output voltage of the inverter circuit is low, the arc grows and therefore it becomes difficult to light the lamp.

Furthermore, the arrow C can be
Even if the lamp were to light up at the time shown in
At this point, it is necessary to rapidly supply current to the lamp, so vo drops as shown by the arrow, and the lamp current IL suddenly decreases (see arrow D'), coupled with a drop in the DC input voltage. When the energy supply capacity of the DC booster circuit becomes insufficient, the lamp goes out (discontinuous lighting state). As a result, such temporary lighting and extinguishing are repeated alternately.

(E. Means for Solving the Problems) Therefore, in order to solve the above-mentioned problems, the present invention includes a DC boost circuit for boosting a DC input voltage and a control circuit for controlling the boost. A lighting circuit for a discharge lamp for a vehicle includes a DC input voltage drop detection circuit that detects that the DC input voltage has decreased below a predetermined value, and a lighting state detection circuit that detects whether the discharge lamp is in a lighting state. ,
Upper limit regulating means is provided for regulating the upper limit value of the output voltage of the DC booster circuit by receiving detection signals from the DC input voltage detection circuit and the lighting state detection circuit and sending signals corresponding to these to the control circuit. When the upper limit regulating means is notified of a drop in the DC input voltage by a signal from the DC input voltage drop detection circuit at the time of starting the discharge lamp, the upper limit regulating means controls the output of the DC booster circuit until the discharge lamp is lit. The upper limit value regarding the voltage is set to a value larger than the upper limit value in a steady state after the discharge lamp is lit, and then when the upper limit regulation means is notified of the lighting of the discharge lamp by a signal from the lighting state detection circuit, the voltage is set for a predetermined period of time. The upper limit regulating means regulates the upper limit value of the output voltage of the DC booster circuit to a value smaller than the upper limit value in the steady state of the discharge lamp until the period of time elapses.

Therefore, according to the present invention, when the DC input voltage is low, the upper limit restriction on the output voltage of the DC booster circuit is relaxed by the upper limit restriction means at the time of starting the discharge lamp, and the allowable range of the output voltage is expanded upward. Therefore, the output voltage necessary for starting the discharge lamp and growing the arc can be obtained.In addition, by tightening the upper limit regulation until a certain period of time has passed after the discharge lamp is lit, the output voltage of the DC booster circuit can be reduced. Since the width of the voltage drop is suppressed, it is possible to prevent the discharge lamp from going out once it has been lit.

(F. Embodiment) [FIGS. 1 to 10] Details of the lighting circuit for the vehicular discharge lamp of the present invention will be described below according to the illustrated embodiment.

(a. Overview of Configuration) [Fig. 1] The lighting circuit 1 will be explained by dividing it into three parts: a power supply system to the lamp, a lighting control system, and a circuit protection system.

(a-1 power supply system) 1 is a lighting circuit.

2 is a battery, which is connected between DC voltage input terminals 3 and 3'.

4.4' is a DC power supply line, and a lighting switch 5 is provided on one of the positive lines 4.

A relay contact 6a is provided on the positive line 4 in series with the lighting switch 5.

Note that this relay contact 6a is opened and closed by a power cutoff relay circuit, which will be described later.

7 is a DC booster circuit, the positive input terminal of which is connected to the output terminal of the relay contact 6a, and the other input terminal (
(ground side) is connected to the DC voltage input terminal 3'. This DC booster circuit 7 is a circuit for boosting the battery voltage, and its boosting is controlled by a control circuit to be described later.

Reference numeral 8 denotes a high frequency booster circuit, which is provided after the DC booster circuit 7 and is a circuit for converting the DC voltage from the DC booster circuit 7 into a sinusoidal AC voltage. As the high frequency boost circuit 8, for example, a push-pull type self-help inverter circuit is used.

Reference numeral 9 denotes an igniter circuit, which is arranged after the high frequency booster circuit 8, and a metal halide lamp 11 having a rated power of 35 W is connected between its AC output terminals 10 and 10'.

(a-2, lighting control system) 12 is a control circuit for controlling the output voltage of the DC booster circuit 7, which is detected by the voltage dividing resistor 13 and 13' provided between the output terminals of the DC booster circuit 7. A voltage detection signal corresponding to the output voltage (hereinafter referred to as 'Vo J) of the DC booster circuit 7 is input. In addition, the current detection resistor 14 is connected to the ground line that connects the DC booster circuit 7 and the high-frequency booster circuit 8, so that it corresponds to the output current of the DC booster circuit 7 (hereinafter referred to as "Io"). The current detection signal is converted into a voltage and sent to the control circuit 1 via the amplifier 15.
2 is now powered by humans.

Then, the control circuit 12 generates a control signal (hereinafter referred to as "Ps") according to these detection signals, sends it to the DC booster circuit 7 via the gate drive circuit 16, and increases the output voltage of the control circuit 12. control.

Also, the control circuit 12 is connected to the D
The output voltage V of the C booster circuit 7. is input, and when a time corresponding to the lamp extinguishing time has elapsed from the time when the lamp starts lighting, the mode shifts to constant power control of the lamp.

18 is a supply voltage drop detection circuit, which detects when the voltage applied to the power supply terminal 19 taken out from the output side terminal of the relay contact 6a via the diode (this is referred to as "+B") becomes below a predetermined value. Send a signal to the control circuit 12 to
Metal halide lamp 1 with control power smaller than rated power
This is for performing lighting control of No. 1.

Reference numeral 20 denotes a lighting/non-lighting detection circuit, which judges whether the metal halide lamp 11 is turned on or not depending on whether the output of the amplifier 15 is above a predetermined level, and outputs a detection signal (this is called "S2o") according to the judgment result. ) is output.

21 is a rest period control section, and the DC voltage input terminal 3.3
It is related to lighting control in a state where the voltage applied to ' has decreased below a predetermined value. That is, when receiving the lamp non-lighting detection signal S2° from the lighting/non-lighting detection circuit 20, it is determined whether the power supply voltage B is below a predetermined value, and if this voltage B is below the predetermined value, DC is controlled by sending a signal (denoted as 'S21J) to the control circuit 12 and regulating the duty cycle of the control pulse Ps.
The upper limit value of the output voltage vo of the booster circuit 7 is varied.

During this period, a signal (hereinafter referred to as "S'2□") for temporarily stopping the operation of the supply voltage drop detection circuit 18 is sent to the supply voltage drop detection circuit 18.

(a-3, Circuit Protection System) 6 is a power cutoff relay circuit, which is provided to cut off the supply of battery voltage to the subsequent circuit in the event of an abnormality in the circuit. That is, when the power cutoff relay circuit 6 receives a signal from an abnormality determination circuit, a low voltage reset circuit, an overvoltage detection circuit, and an output current abnormality detection circuit, which will be described later, the internal relay turns off and opens the relay contact 6a described above. It works like this.

22 is an abnormality determination circuit, and the output voltage V of the DC booster circuit 7. It is possible to judge whether the circuit has fallen into an abnormal state from the magnitude relationship between the judgment reference value of the output current corresponding to the output current and the signal level corresponding to the output current of the DC booster circuit 7 from the amplifier 15, and to determine whether the circuit is in an abnormal state or not. Detection signal 5 from detection circuit 20
20, a control signal is sent to the power cutoff relay circuit 6. Abnormal conditions in the circuit include:
For example, there may be a lighting abnormality of the metal halide lamp 11 (lamp short-circuit or oven condition) or a case where the high frequency booster circuit 8 becomes open at the output stage. and,
When the abnormality determination circuit 22 detects such an abnormal state of the circuit, it sends a signal to the power cutoff relay circuit 6 and shuts down the battery 2.
The supply of power supply voltage to the DC booster circuit 7 is cut off from there.

23 is a low voltage reset circuit, which sends a signal to the power cutoff relay circuit 6 via a delayed recovery circuit (to be described later) when the battery voltage becomes abnormally low and the lamp cannot be kept lit; It is designed to cut off the supply of battery voltage to the Incidentally, such an operation is performed only when it is notified that the lamp is not lit by receiving the detection signal s2° sent from the lighting/non-lighting detection signal 20. . In other words, the low voltage reset circuit 23 does not decide whether or not to supply power to the DC booster circuit 7 based only on the magnitude of the battery voltage, but also constantly monitors the lighting state of the lamp and determines whether the lamp is in the non-lighting state. After knowing this, it is determined whether or not the battery voltage is below a predetermined value, and a decision is made as to whether or not to supply the battery voltage to the power supply system.

24 is an A voltage detection circuit, which detects that the value of the battery voltage exceeds a predetermined value, and at this time, the delay recovery circuit 2
5 to a power cutoff relay circuit 6 to cut off the supply of battery voltage to the power supply system.

When the delayed recovery circuit 25 receives an abnormality detection signal from the low voltage reset circuit 23 or the overvoltage detection circuit 24, it promptly turns off the relay in the power cutoff relay circuit 6 to open its contact 6a, and Thereafter, the relay contact 6a is provided to close the relay contact 6a after a predetermined delay time when the battery voltage returns to a normal range.

26 is an output current abnormality detection circuit, and a high frequency booster circuit 8
This is provided to protect the circuit when a short circuit occurs in the output stage or when a short circuit occurs in another circuit section and the output current ro becomes abnormally large. That is, the output current abnormality detection circuit 26 receives the output current I of the DC booster circuit 7. When the output current I0 of the DC booster circuit 7 exceeds a certain reference value, it is determined that there is an abnormality, and a signal is sent to the power cutoff relay circuit 6 to shut down the DC booster circuit. The battery voltage supply to 7 is cut off.

Note that the output current abnormality detection circuit 26 detects the output voltage ■ of the DC booster circuit 7. Metal halide lamp 1 by constantly monitoring
1 is in the initial lighting state or in a steady state, and based on this, the output current 10 of the DC booster circuit 7
The comparison standard value for

As described above, the power cutoff relay circuit 6 is connected to circuits 22 and 23.
．． It is determined whether or not to supply battery voltage to the power supply system according to the signals from 24 and 26, but there are some permanent In response to an abnormality detection signal based on the cause of the abnormality, this is held and the power supply cutoff state continues unless the lighting switch 5 is turned on again, and the low voltage reset circuit 2
3 or the signal from the overvoltage detection circuit 24, or an increase (or decrease) in the battery voltage, the power supply cutoff state is not maintained in response to an abnormality detection signal due to a temporal cause, and the battery voltage is normal. When the voltage returns to the value, power supply voltage is supplied to the power supply system again.

(b. Circuit configuration of each part) [FIGS. 2 to 4] Next, each part constituting the lighting circuit 1 will be described in detail.

(b-t, power supply system) [Fig. An N channel is provided between the positive line 4 and the ground line 4' at the subsequent stage and is switched by the control pulse Ps sent from the control circuit 12 via the gate drive circuit 16. It consists of an FET 28, a rectifying diode 29 whose anode is connected to the drain of the FET 28 on the positive line 4, and a smoothing capacitor 30 provided between the cathode of the diode 29 and the ground line 4'. . Then, the DC booster circuit 7 receives the control pulse P
The inductor 27 stores energy when the FET 28 turns on due to s, releases the stored energy when the FET 28 turns off, and superimposes the corresponding voltage on the input voltage. It is designed to boost the DC voltage.

(b-1-b, High Frequency Boost Circuit) As the high frequency boost circuit 8, an automatic push-pull type inverter circuit is used.

That is, one end of the choke coil 31 is connected to the positive output terminal of the DC booster circuit 7, and the other end is connected to the transformer 32.
It is connected to the center tap of the primary winding 32a.

33 and 33' are N-channel FETs, the sources of which are both connected to one end of the current detection resistor 14, and the FET
The drain of the ET33 is connected to the terminal on the starting end side of the primary winding 32a, and the drain of the FET33'' is connected to the terminal on the terminal side of the primary winding 32a.

34 is a feedback winding provided on the primary side of the transformer 32, and the voltage generated in this is sent to a two-phase gate drive circuit 35, where two drive signals having an antiphase relationship with each other are generated. The signals are sent out to FETs 33 and 33', respectively.

36 and 36' are resistors provided between the gates and sources of FETs 33 and 33', and 37 is a Zener diode inserted between the center tap of the primary winding 32a and the common source of FETs 33 and 33'. .

38 is a capacitor provided on the primary side of the transformer 32;
39 is a capacitor provided on the secondary side.

Therefore, in the high frequency booster circuit 8, the FETs 33 and 33' are switched in a reciprocal manner by a drive signal generated by the gate drive circuit 35 based on the voltage induced in the feedback winding 34, and thereby the two of the transformer 32 are switched. A sinusoidal AC voltage is generated across the secondary winding 32b.

(b-1-c, Igniter Circuit) The igniter circuit 9 includes a trigger transformer 40 and a trigger pulse generator 41.

That is, the secondary winding 40b of the trigger transformer 40 is provided on a line connecting one output terminal of the high-frequency booster circuit 8 and the AC output terminal 10, and the trigger pulse generator 41 is connected to the secondary winding 40a. The output pulse is added.

The trigger pulse generator 41 includes a spark gap element 4
1a, capacitors 41b, 41c, and diode 41
d, and a voltage doubler rectifier circuit consisting of 41d'.

That is, one end of the spark gap element 41a is connected to the starting end side terminal of the primary winding 40a of the trigger transformer 40,
The other end is connected to the AC output terminal 10' via a diode 41d and a capacitor 41b. A capacitor 41c and a resistor are provided in parallel with the primary winding 40a and the spark gap element 41a, and a diode 41d' is provided in parallel with the series circuit of the capacitor 41c and the diode 41d, and in a direction opposite to the diode 41d. ing.

Therefore, when the capacitor 41c is charged when the lamp is started and its terminal voltage (see ■ in FIG. 11) exceeds a predetermined value, a trigger pulse is generated due to conduction of the spark gap element 41a, and this is boosted by the trigger transformer 40. After being superimposed on the AC output of the high frequency booster circuit 8, it is applied to the metal halide lamp 11.

(b-2, lighting control system) [Figure 3] Regarding the lighting control system, the control circuit 12, timer circuit 1
7. The supply voltage drop detection circuit 18, lighting/non-lighting detection circuit 20, and pause period control section 21 will be described in detail.

The control circuit 12 includes an output voltage detection section for detecting the output voltage Vo and output current I0 of the DC booster circuit, an output current detection section, and a PWM (pulse width modulation) control section.

(b-2-a, Output Voltage Detection Section) 42 is an output voltage detection section, which detects the output voltage V of the DC booster circuit 7 via voltage dividing resistors 13 and 13'. is detected, compared with a predetermined reference value, and outputs the difference voltage as an error output.

43 is an error amplifier, in which a non-inverting input terminal of an operational amplifier 44 subjected to negative feedback is connected to the voltage dividing resistor 13 via a resistor.
and 13', and a voltage detection signal (hereinafter referred to as 'Sv J) is input. and,
A predetermined reference voltage (hereinafter referred to as "Vl") defined by a voltage dividing resistor 45.45' is applied to the inverting input terminal. Note that one end of the resistor 45 is supplied with a predetermined voltage (this is referred to as 'VrafJ) by a reference voltage generator (not shown).

), but this V ref is assumed to be a constant value that is not affected by fluctuations in battery voltage.

44a is a feedback resistor of the operational amplifier 44, and 44b is a capacitor provided in parallel with the feedback resistor 44a.

(b-2-b, output current detection section) 46 is an output current detection section, which detects the output current IO of the DC booster circuit 7 as a voltage conversion value via the current detection resistor 14, and converts this into a voltage conversion value based on a predetermined standard. It is provided to compare the voltage and take out the difference voltage as an error output.

As the amplifier 15, an operational amplifier 47 to which negative feedback is applied by a resistor is used. The non-inverting input terminal of the operational amplifier 47 is connected to the output terminal of the current detection resistor 14 via the resistor 48, so that a current detection signal (hereinafter referred to as "SI") is input manually. The inverting input terminal is grounded via a resistor 49.

50 is an operational amplifier serving as an error amplifier, and its non-inverting input terminal is connected to the output terminal of the operational amplifier 47 via a resistor 51. A reference voltage (this is referred to as "■2") generated by the reference voltage generating section 52 is applied to the inverting input terminal.

The reference voltage generating section 52 includes a resistor 53.5 connected in series.
3', and a voltage buffer 54 which extracts a voltage from between the resistors 53 and 53', and the output of the voltage buffer 54 is applied to the inverting input terminal of the operational amplifier 50 via the resistor. Note that a voltage Vr is applied to one end of the resistor 53.
@g is added.

(b-2-c, timer circuit) The timer circuit 17 is a circuit provided to shift to constant power control after a predetermined time period corresponding to the lamp extinguishing time has elapsed from the start of lighting, and is an active circuit. It consists of a switch element and a time constant circuit.

55 is an NPN transistor whose collector is DC
It is connected to the positive side pressure terminal of the booster circuit 7, and its emitter is connected to the non-inverting input terminal of the operational amplifier 50 via the resistor 56.

The base of the transistor 55 is connected to the anode of a diode 57, and the cathode of the diode 57 is connected to a capacitor 58 (its capacitance is represented by 'CsaJ).
is grounded through.

59 is a resistor provided between the base and collector of the transistor 55 (its resistance value is RseJ), and 60 is a resistor provided between the cathode of the diode 57 and the collector of the transistor 55 (its resistance value is assumed to be RseJ). 'Ra.'
shall be. ).

(b-2-d, PWM control unit) 61 is a PWM control unit, whose comparator 62 compares the input voltage with the triangular wave from the oscillator 63, and generates a control pulse P having a duty cycle according to the input voltage. It is something that generates.

That is, the negative input terminal of the comparator 62 is connected to each output terminal of the operational amplifiers 44 and 50, and the positive input terminal thereof is connected to the output terminal of the oscillator 63.

64 is a comparator for adjusting the rest period, which controls the rest period of the control pulse PS, and as a result, the DC
Output voltage V of booster circuit 7. (This is written as "vl". However, the value of V is not a fixed value but is variable by the pause period control unit 21.). A signal from the oscillator 63 is input to the positive input terminal, and as the voltage applied to the other negative input terminal is increased, the rest period of the pulse output from the comparator 64 becomes longer.

65 is an AND circuit, which performs an AND operation on each output pulse from the comparators 62 and 64, and outputs the result via a buffer 66 to obtain the final control pulse ps. .

Therefore, the AND circuit 65 selects the one with the smaller duty cycle among the output pulses of the comparators 62 and 64.

A reference voltage ■ is applied to the negative input terminal of the comparator 64 for adjusting the rest period. Normally, a voltage obtained by dividing f by voltage dividing resistors 67.68 (respective resistance values are written as 'R67J and 'RaaJ) is applied, but the rest period control unit 21 generates a voltage depending on the operating status of the circuit. Different values of voltages are applied according to the signal SZ+ from the DC booster circuit 7, thereby increasing the output voltage of the DC booster circuit 7. (i.e., the upper limit V,
) is now variable.

To summarize the above explanation, the duty cycle of the control pulse Ps obtained by the PWM control section 61 is the output voltage detection section 42, the output '! ? The upper limit value of the duty cycle of the control signal Pg is determined by the voltage level applied to the negative input terminal of the comparator 64 for adjusting the idle period. Then, the control pulse PS is fed back to the FET 28 of the DC booster circuit via the gate drive circuit 16, and the output voltage V is increased. is controlled.

(b-2-e, supply voltage drop detection circuit) The supply voltage drop detection circuit 18 applies the voltage to the metal halide lamp 11 by varying the reference voltage (2) in the output current detection section 46 according to the drop in the power supply voltage B. This suppresses the power below the rated power value.

69 is a Zener diode whose cathode is connected to the power supply terminal 19, and whose anode is connected to the resistors 70 and 70.
' is grounded through.

71 is a voltage buffer for taking out the voltage between the resistors 70 and 70'', and its output terminal is connected to the cathode of the diode 72, and the anode of the diode 72 is connected to the reference voltage generator 52 through the resistor 73. Resistors 53 and 53'
is connected between.

(b-2-f, lighting/non-lighting detection circuit) 74 is a comparator whose negative input terminal is connected to the pressure terminal of the amplifier 15 via a resistor 75, and the output of the amplifier 15 (this is "S+sJ A predetermined reference voltage (hereinafter referred to as "V") is applied to the positive input terminal.

That is, the comparator 74 outputs the output voltage S15 of the amplifier 15.
and the reference voltage ■3, and as a result of the comparison, the signal S
2°, and when the lamp is on, the SIS level is higher than v3, so the signal S
20, an L (low) signal is output, and since the level of srs is less than V8 when the lamp is not lit, an H (high) signal is output as a signal S2°.

76 is a capacitor inserted between the negative input terminal of the comparator 74 and the ground line.

77 is an NPN) transistor whose emitter is grounded, and the output voltage of the comparator 74 is connected to the base of the resistor 7.
A voltage divided by 8.78' is applied. The collector thereof is connected to the non-inverting input terminal of the operational amplifier 50 of the output current detection section 46. Therefore, comparator 7
When the output signal of No. 4 becomes H level, the transistor 77 is turned on, and the potential of the non-inverting input terminal of the operational amplifier 50 is forcibly reduced to near zero.

(b-2-g, idle period control unit) 79 is a comparator, to which a signal S2° from the lighting/non-lighting detection circuit 20 is inputted via a resistor 80 to its plus input terminal, and to its minus input terminal. A reference voltage (hereinafter referred to as "v4") applied to is compared.

Reference numeral 81 designates a comparator, to which a voltage obtained by dividing the power supply voltage B by a voltage dividing resistor 82.82' is applied to its negative input terminal, and a voltage obtained by dividing the power supply voltage B by a voltage dividing resistor 83.83' is applied to its positive input terminal. The divided voltage is applied via resistor 84. The output terminal of the comparator 79 is connected between voltage dividing resistors 83 and 83' that determine the reference voltage of the comparator 81.

That is, the comparator 81 determines whether the value of the power supply voltage B is greater than or equal to the reference value;
It changes according to the output of 9.

85 is an NPN transistor with a common emitter, the collector of which is a resistor 86 (its resistance value is written as 'RaaJ').

) is connected between the voltage dividing resistors 67 and 68, and its base is IM connected to the output terminal of the comparator 81 via the resistor 87.

88 is a common emitter NPN transistor provided in parallel with the transistor 85, and its base is connected to the resistor 89.
It is connected to the output terminal of the comparator 81 via.

90 is a resistor, one end of which is applied a predetermined voltage ■cc (stabilized voltage obtained from the DC booster circuit 7) from a power supply circuit (not shown), and the other end of which is connected to a capacitor 9.
1 and is connected to the collector of the above-mentioned transistor 88 via a resistor 92.

A comparator 93 has a negative input terminal connected between a resistor 90 and a capacitor 91, and a reference voltage (hereinafter referred to as "V") is applied to a positive input terminal. The configuration of the circuit that generates this reference voltage v5 and the change in v5 after the power is turned on will be described later.

94 is a common emitter NPN transistor which is switched according to the output of the comparator 93, and a predetermined voltage V ra is connected to the collector of the transistor via a resistor 95.95'.
f is added.

96 is a PNP transistor with a common emitter, the base of which is connected between resistors 95 and 95', and the collector of which is connected to the voltage dividing resistor 67 via a resistor 97 (the resistance value is written as rR, J). and 68.

The signal sent from the transistor 85.96 to the comparator 64 for adjusting the idle period via the voltage dividing resistor 67.68 is 3.
It corresponds to 21.

Further, the output of the comparator 93 is input to the voltage buffer 71 of the supply voltage drop detection circuit 18 via a diode, and this signal is sent to S'2. is equivalent to

Therefore, when the idle period control unit 21 receives the H signal from the lighting/non-lighting pressure detection circuit 20, the comparator 81 determines whether the power supply voltage B is below a predetermined value, and the output of the comparator 81 is determined by the comparator 81. The H i= signal turns on the transistor 85.88, and the H signal output from the comparator 93 turns on the transistor 94.96.
turns on. Then, when the signal SaO becomes L level, the output of comparator 81 becomes L level, transistors 85 and 88 are immediately turned off, but capacitor 91
Since charging takes time, a predetermined delay time is required until the output of the comparator 93 becomes an L signal and the transistors 94 and 96 are turned off.

(b-3, circuit protection system) [Figure 4 (b-3-a, power cutoff relay circuit) 98 is a power supply terminal, which is connected to the output side terminal of the lighting switch 5 via a reverse voltage prevention diode. It is connected. The voltage applied to this power supply terminal 98 is written as r4-9'J.

Reference numeral 99 is a relay, and one end of the coil 99a is connected to the electric wire 98, and the other end is connected to the collector of the NPN transistor 100. Relay contact 6a is opened and closed depending on whether or not coil 99a is energized.

101 is a signal holding circuit, and the input terminal 101a receives signals from the abnormality determination circuit 22 and the output current abnormality detection circuit 26;
When a becomes H level, this state is maintained and the transistor 100 is turned off.

As a result, the relay 99 is turned off, and the supply of power supply voltage to the DC booster circuit 7 is cut off. This state continues until the lighting switch 5 is turned off and then turned on again.

Further, a low voltage reset circuit 2 is connected to the base of the transistor 100 when an abnormality related to the battery voltage is detected.
3 and the overvoltage detection circuit 24 are sent to the delayed recovery circuit 2.
This turns off the transistor 100 and turns off the relay 99.

When the battery voltage returns to the normal range, an H signal from the delay recovery circuit 25 causes the transistor 10 to
0 is turned on, the contact 6a is closed by the operation of the relay 99, and the lighting operation is restarted.

(b-3-b, abnormality determination circuit) 102 is a comparator, the output SIS of the amplifier 15 is applied to its positive input terminal via a resistor 103, and the output SIS of the DC booster circuit 7 is applied to its negative input terminal. A voltage obtained by dividing the output voltage v0 by voltage dividing resistors 104 and 104' is sent via a resistor 105.

106 is an NPN transistor whose emitter is grounded, and its base is connected to the comparator 10 via a resistor 107.
It is connected to the second output terminal.

108 is a resistor, one end of which is connected to the power supply terminal 19, the other end of which is grounded via a capacitor 109 and connected to the collector of the transistor 106 via a resistor 110.

A diode 111 is provided in parallel with the resistor 108 , its cathode is connected to the power supply terminal 19 , and its anode is connected between the resistor 108 and the capacitor 109 .

112 is an NPN transistor with a common emitter, and a switching operation is performed by applying a voltage obtained by dividing the level of the signal S2° from the lighting/non-lighting detection circuit 20 by voltage dividing resistors 113 and 113' to its base. It looks like this. And that collector is comparator 10
2 and is also connected to the power supply terminal 19 via a resistor 114.

115 is a comparator, the negative input terminal of which is connected between the resistor 108 and the capacitor 109 via a resistor, and the positive input terminal to which a predetermined reference voltage (indicated by constant voltage source E1) is applied. There is.

116 is an NPN transistor with a common emitter, the base of which is connected to the pressure terminal of the comparator 115 through a resistor 117, the collector of which is connected to the power supply terminal 19 through a resistor, and the signal is connected through a diode 118. It is connected to the input terminal 101a of the holding circuit 101.

Therefore, in this abnormality determination circuit 22, when the voltage obtained by dividing the output voltage vo of the DC booster circuit 7 is larger than the output voltage of the amplifier 15, the output of the comparator 102 becomes low.
becomes a signal, turns off the transistor 106, and turns off the resistor 108.
The capacitor 109 connected to the power supply terminal 19 through the capacitor 109 is gradually charged, and after a predetermined time, the output of the comparator 115 becomes an L signal, so that the transistor 116 is turned off.

Further, the signal S20 from the lighting/non-lighting detection circuit 20 is H.
In the case of a signal (that is, a non-lighting detection signal), transistor 1
12 is turned on, thereby forcing the transistor 106 to turn off. Therefore, the signal output from the comparator 115 turns the transistor 116 off.

(b-3-c, output current abnormality detection circuit) 147 is a Zener diode whose cathode is connected to the positive output terminal of the DC booster circuit 7, and whose anode is connected to the series resistor 14.
8.148' to ground.

149 is a common emitter NPN transistor whose base is connected between resistors 148 and 148', and whose collector is applied with voltage VCC via the resistor.

Reference numeral 150 denotes a common emitter NPN transistor provided next to the transistor 1490, and its base is connected to the collector of the transistor 149 via a resistor 151.

152 is a comparator, and the output SIs of the amplifier 15 is inputted to the positive input terminal of the comparator via a resistor 153. And a resistor 154.1 is connected to the negative input terminal.
A voltage V ref is applied through 55 and a resistor 1
54 and 155 are connected to the collector of transistor 150 via resistor 156. Further, the output terminal of the comparator 152 is connected to the input terminal 101a of the signal holding circuit 101 via a diode 157.

However, in this output current abnormality detection circuit 26, D
When the output current of the C booster circuit 7 becomes larger than a certain reference value, the output of the comparator 152 becomes an H signal, but the reference voltage value at the negative input terminal of the comparator 152 is DC.
It is defined depending on the output voltage value of the booster circuit 7. That is, in the early stage of lighting of the metal halide lamp 11, the output voltage of the DC booster circuit 7 is large, so the Zener diode 14
7 turns on, transistor 149 turns on and transistor 150 turns off, so the value of the reference voltage is large. Also, during steady lighting, transistor 149 is off and transistor 150 is on, so the reference voltage is small. value.

(c, Operation) [Figs. 5 to 10] Next, the operation of the lighting circuit 1 will be explained using the metal halide lamp 11.
The lighting control operation and circuit protection operation will be explained separately.

Incidentally, FIG. 5 shows the output voltage vo (V) of the DC booster circuit 7.
, output current I0 (A), lamp current IL (A),
It schematically shows the time course of the lamp voltage VL (■) and the luminous flux L (Ilm) of the metal halide lamp 11, and the origin of the time axis t is immediately after the lighting switch 5 is turned on. In addition, in Figure 6, the horizontal axis represents the output voltage ■. It is a graph diagram showing the relationship between the two, with output current Io plotted on the vertical axis.

(c-1, lighting control operation) The lighting control operation of circuit 1 is performed when the voltage applied between the DC voltage input terminals 3 and 3' is within a normal range (hereinafter referred to as "normal input terminal"). This will be explained in detail separately for cases where the input terminal is low (hereinafter referred to as "when the input terminal is low").

(c-1-a When the input terminal is normal) [Figures 5 to 8
[Figure] First, the situation when the lamp starts to turn on from a cold state (hereinafter referred to as "cold start") will be explained.

In this case, immediately after the lighting switch 5 is turned on, the capacitor 58 of the timer circuit 17 is empty, and the emitter potential of the transistor 55 is low. Therefore, only the output of the amplifier 15 is applied to the non-inverting input terminal of the operational amplifier 50 in the output current detection section 46.

Immediately after lighting, the lamp voltage (2) is low and the pressure current I0 of the DC booster circuit 7 is relatively small, as can be seen from the graph curve shown by the solid line in FIG.

In other words, the output SI5 of the amplifier 15 is the reference voltage generator 52.
The reference voltage v2 is smaller than the reference voltage v2.

Furthermore, while the lamp is not lit, the level of S15 is lower than V, so the output signal of the lighting/non-lighting detection circuit 20 is an H signal, and the transistor 77 is in the on state, so the input terminal of the operational amplifier 50 is forced to L level.

Then, from the time when the lighting switch 5 is turned on until the lighting of the lamp is detected, the duty cycle of the control pulse PS is determined by the input voltage of the comparator 64 for adjusting the rest period, that is, the voltage V ref is controlled by the resistors 67 and 68. It is defined by the divided voltage value, and this value defines the upper limit of the output voltage V0 of the DC booster circuit 7. This situation is schematically shown in FIG. 7, where "B" indicates the power supply voltage, and the level of 'BLJ shown by the broken line indicates the lower limit value regarding the power supply voltage B. indicates the level (H/L) of the output signal of the comparator 81, and rcMp (93)
-INJ indicates the level of the human input signal of the comparator 93, where the solid line represents the potential of the negative input terminal, and the broken line represents the potential of the positive input terminal. And r
CMP(93)J indicates the level (H/L) of the output signal of the comparator 93, and 'VlN64J indicates the potential of the minus input terminal of the comparator 64 for adjusting the idle period.

As shown in the figure, the power supply voltage B is B > B L,
The output of the comparator 81 becomes an L signal regardless of the level of the detection signal S20, and the output of the transistor 85.
is off.

The negative human potential of the comparator 93 is the capacitor 91
As the voltage increases as shown by the solid line, it saturates to a certain value. Further, the positive human input potential of the comparator 93 rises and becomes saturated at a level lower than the negative input potential, as shown by the broken line. This is because the circuit that generates the negative human potential ■5 has a time constant circuit configuration as shown in Figure 8, and depending on the time constant setting, V5 is generated after the power is turned on.
This is because the voltage rises slowly while remaining below the negative human power potential. That is, as shown in the figure, the voltage V ref is applied to one end of the resistor 119, and the other end is grounded via the resistor 120. A capacitor 121 is provided in parallel with the resistor 120, and a diode 122 or the resistor 119 is connected to the capacitor 121. are provided in antiparallel to.

Since the negative input terminal of the comparator 93 exceeds 5, the comparator 93 eventually outputs an L signal. Therefore, since the outputs of the comparators 81 and 93 are both at the L level, the transistors 85, 94, and 96 are in the OFF state, and the negative human potential VIN64 of the comparator 64 for adjusting the idle period rises sharply after the power is turned on, and immediately attenuates. After that (due to the action of the capacitor 44b), the voltage settles to the divided voltage value of the reference voltage Vref by the resistor 67.68.

Thereafter, when lighting of the lamp is detected, the duty cycle of the control pulse Ps is determined by the output voltage of the error amplifier 43 of the output voltage detection section 42, and this control pulse Ps is sent from the PWM control section 61 to drive the gate. The signal is sent to the FET 28 of the DC booster circuit 7 via the circuit 16.

Point a in FIG. 6 shows the state immediately after the start of lighting, and from this point a, the control region Av increases until the output voltage vo is approximately constant and the output current 1o reaches the output voltage detector 4.
This is an area under the control of 2.

After that, the capacitor 58 is gradually charged (if the time constant at this time is "τ1", τ1= (R8Q//
R1!10) ・Css. However, "//" represents parallel combination of resistance values. ), the emitter potential of the transistor 55 increases accordingly, and the potential of the non-inverting input terminal of the operational amplifier 50 increases.

When this reaches a level corresponding to the reference voltage v2, the duty cycle of the control pulse ps is determined by the output voltage of the operational amplifier 50.

That is, as the output voltage of the operational amplifier 50 increases, the duty cycle of the control pulse Ps decreases.
The output voltage V had maintained its highest value until then. Or it will gradually decrease.

Regarding the reference voltage v2, if the battery voltage is higher than a predetermined value, for example, IOV, the Zener diode 6
9 is conductive, the output voltage of the voltage buffer 71 is higher than the input terminal of the voltage buffer 54 of the reference voltage generating section 52 (the diode 72 is off).
The reference voltage (2) is determined by the value obtained by dividing Vrsf by a resistor 53.53'.

In FIG. 6, the control region A from point A to point d passes through the peak point C of the output current IO! is the area under the control of the output current detection section 46.

When the capacitor 58 is fully charged, the transistor 55 turns on and its emitter potential changes to DC.
Output voltage of booster circuit 7■. becomes almost equal to , and from this point onwards, the control shifts to constant power control.

In other words, the output voltage V. Since control is performed so that the sum of the voltage divided by the resistor 51.56 and the amplified output S15 corresponding to the output current I0 becomes a constant value corresponding to v2, it is said that vo ・■ o11 = constant. Constant power control is realized in the form of linear approximation.

A region A from point d to point e in FIG. 6 is a constant power region, and the rated power is supplied to the metal halide lamp 11 in this region.

As can be seen from the curve shown by the solid line, the lamp luminous flux shows a steep rise immediately after the lamp is turned on, and then goes through an overshoot and transitions to a steady state.

Next, the relighting operation after the metal halide lamp 11 is turned off will be explained.

While the lamp is off, the electric charge stored in the capacitor 58 of the timer circuit 17 has a time constant τ2 (=R
a.・C88) is gradually discharged.

This time constant τ2 is determined to be a value that corresponds to the degree of temperature drop of the lamp after it is turned off, so the lighting switch 5
When the capacitor 58 is turned on again, a lighting operation is started from the control region according to the terminal voltage of the capacitor 58.

That is, appropriate lighting control is performed according to the elapsed time required from the time of turning off the light to the time of re-lighting.

For example, when the lamp is turned on again several tens of seconds after it has been turned off, lighting starts from the operating point within the control area Al and shifts to constant power control, as shown by the dashed line in Fig. 5. The output voltage v0 and output current I0 form a curve that gradually decreases immediately after the lighting starts, and the lamp luminous flux rises sharply at first, goes through an overshoot, and then becomes stable.

Also, if the light is turned on again several seconds after it has been turned off,
The glass bulb of the metal halide lamp 11 is still hot, and as shown by the two-dot chain line in Fig. 5, the lamp voltage V immediately after restarting is high and the output current 1o is large, so it immediately shifts to constant power control and the luminous flux decreases. stabilizes at the rated power.

Note that the reason for providing the timer circuit 17 is to shorten the starting time.

That is, without providing the timer circuit 17, the output voltage (2) of the DC booster circuit 7 is applied via the resistor 56. If it is applied directly to the non-inverting input terminal of the operational amplifier 50, constant power control will be performed from the start of lighting regardless of the physical state of the lamp. This is because light emission is not promoted and the rise of the luminous flux is delayed.

(c-1-b, when the input terminal drops) [FIGS. 9 and 10] Each operation of the suspension period control section 21 and the supply voltage drop detection circuit 18 will be explained. Incidentally, the causes of the decrease in the input voltage include not only a decrease in the battery voltage itself but also a voltage drop caused by the resistance of the connection line connecting one terminal of the battery and the DC voltage input terminal 3, 3'.

(c-1-b-1, Operation of the idle period control section) The lighting control operation by the idle period control section 21 when the DC input voltage is low will be described at the time of cold start. In addition, diagram N9 is a time chart diagram showing this situation, and in the diagram rB",
'BL J, rCMP (81) J, rCMP (93)
-INJ, rcMP(93)J, and the meanings of "v'N64" are as already explained in FIG.
Tr(85)" and "Tr(88)" are the switching states F! of transistors 85 and 88, respectively. ! (ONloF
F), and these transistors 85 and 88 are in the same operating state as the comparator 81 in response to the signal S2°, so they are shown together in a chart. Also, r7r (94)J, 'Tr (96)
” is the switching state of transistors 941.96 (O
These transistors 94 and 96 operate in conjunction with each other with respect to the signal s20, so they are shown together in a chart. 'O
3+aJ turns off the operation of the supply voltage drop detection circuit 18
(non-operation),""ON(operation)," and rREL (-next release).

The pause period control section 21 is designed not to have any effect on other circuits unless it receives the non-lighting detection signal S2゜(-"HJ) from the lighting/non-lighting detection circuit 20. In this case, there is no effect on the normal operation described above.

First, during the period from when the power is turned on until the signal S2° rises (this period is referred to as 'ToJ'), the level of the signal S2° is less than 74, and the output of the comparator 79 is low.
level (however, the lamp is not yet lit), the output of the comparator 81 is at the L level regardless of the value of the power supply voltage B, and the transistors 85 and 88 are turned off. Then, the human power potential of the comparator 93 increases together, but in this case, the positive input potential (see broken line)
is below the negative input potential (see solid line), so
The L signal output from the comparator 93 turns off the transistors 94 and 96.

Therefore, the input voltage v of the rest period adjustment comparator 64
Once IN64 rises and attenuates, the voltage V raf
is divided by the resistor 67.68 (see Figure 10 (A)).
)reference). Therefore, the upper limit value Vm of the output voltage V0 of the DC booster circuit 7 becomes a value corresponding to this V(0) (this is written as "V'.i").

In addition, since the power supply voltage B is below the lower limit value BL of the normal range, the supply voltage drop detection circuit 18 is activated (the specific operation will be described later), and the lighting is performed with power according to the power supply voltage B. Control takes place.

The period from when the signal 520 becomes H level until the lamp lights up and becomes L level (this period is written as 'THJ').

), the operation of the idle period control unit 21 is started, and it is determined whether the power supply voltage B is within a normal range.

That is, the output of the comparator 79 (X"r becomes H level, and the comparator 81 determines that the power supply voltage B is below the lower limit value BL. state.

Therefore, the negative human potential of the comparator 93 suddenly drops and becomes smaller than the positive human potential, so the output signal of the comparator 93 becomes H level, and the output signal of the transistor 94.
Since 96 is in the on state, ylN64 is in the state shown in Fig. 10 (B).
As shown in , the reference voltage V ref is expressed as a parallel composite resistance value (R
67//R97) and (Raa//Raa).

= (7) V (H' is the resistance value R67, R1111,
R86, R9vf) y '81 < y f by selection
Since it is set in advance to be o+, the input terminal level of the comparator 64 for adjusting the idle period decreases.

Therefore, the upper limit value of the output voltage VO of the DC booster circuit 7 corresponding to this yfH+ (this is written as "y").

) is VLMゝ> v3011, so the output voltage vo
In this case, a higher voltage value is allowed than during the period T0,
It becomes a state.

Furthermore, the operation of the supply voltage drop detection circuit 18 is forcibly and temporarily canceled (stopped) by the H signal sent from the comparator 93 via the diode, so that power regulation for the lamp does not work.

Next, a predetermined period of time (this is
It is written as TLJ. ), transistors 85 and 88 are immediately turned off by the signal output from comparator 81, but even if transistor 88 is turned off, comparator 9
The output of capacitor 91 does not immediately go to L level, but remains at H level during the period TL until the terminal voltage of capacitor 91 reaches a predetermined value. In other words, during this time the comparator 93
The negative human power potential at is lower than the positive input potential.

Therefore, since the transistors 94 and 96 are in the on state during this period TL, the value of ylN64 is as shown in FIG.
As shown in C), the resistance value R68 and the parallel combined resistance value R+!
7//R97 is the value obtained by dividing the pressure.

The value of this VfL' is the resistance value R68, R67,
Since it is set in advance so that y3Ll > Vto+ by selecting R97, the upper limit value of the output voltage v0 corresponding to y(Ll (this is written as "■(L-)").

) is y ILI, < y +01+,, roar.

That is, in the period TH, the upper limit of ■o was set higher than y[o□, but this time the upper limit is set to ■N)1. The regulations will become stricter.

Note that during this period TL, the operation of the supply voltage drop detection circuit 18 remains stopped due to the H signal output from the comparator 93.

After the period TL has elapsed (the period after this is written as "T'").

), since the terminal voltage of the capacitor 91 exceeds the positive potential of the comparator 93, the output signal of the comparator 93 turns off the transistors 94 and 96.

Therefore, the value of ylN,4 is again equal to yfoゝ, and the output voltage ■. The upper limit value of is 30]a.

Further, unless the power supply voltage B returns to the normal range, the supply voltage drop detection circuit 18 is activated by the signal output from the comparator 93, and power regulation is applied again.

To summarize the above operation, when the voltage B falls below a predetermined value, the upper limit regulation on the output voltage Vo of the DC booster circuit 7 is first relaxed, and then when lighting of the lamp is detected, the upper limit regulation is tightened. During this period (that is, periods TH and TL), the regulation of power supply to the lamp by the supply voltage drop detection circuit 18 is temporarily removed, thereby reducing the side effects associated with prompting the lamp to emit light during period TH.

That is, ■ after the period TH. If the value of is simply returned to ■30', the lighting state immediately after the lamp is turned on will become unstable, and the lamp may turn off. The upper limit of VO is lowered to stabilize the lighting operation.

(c-1-b-2, Operation of supply voltage drop detection circuit) When the power supply voltage B becomes less than a predetermined value (for example, 10V), the output voltage of the voltage buffer 71 becomes lower than the voltage generated by the reference voltage generation section 52, and the diode 72 is turned on, the reference voltage V2 becomes low.

Therefore, as the power supply voltage B decreases, the metal halide lamp 11 receives less power than the rated power (for example, 50 to 75%).
degree) will be supplied.

Note that such low power control is temporarily canceled when the idle period control section 21 is controlling the idle period as described above.

That is, during periods T and TL, H (No.
is off, and therefore the value of the reference voltage v2 is the same as that of the reference voltage generator 5.
2, the operation is the same as when the input voltage is normal.

Then, when the power supply voltage B further decreases and the capacity of the battery 2 becomes insufficient to maintain the lighting, the low voltage reset circuit 23 shifts to operation.

(c-2, Circuit Protection Operation) [Figure 6] Next, the protection operation when an abnormal state of the lighting circuit 1 is detected will be described.

(c-2-a, Protective Operation by Abnormality Determination Circuit) First, the criteria used to determine whether the circuit is in a normal state or an abnormal state will be explained.

V in Figure 6. -I. In the characteristic diagram, a straight line k (Io = −VO
It can be expressed as ) indicates a normal/abnormal condition determination line, and this determination line k divides the area into two.

That is, V o -I. Any point P(V
o, Io) represents the operating state of the circuit, and regions are divided depending on whether this point is above or below the determination line.

In other words, the above-mentioned control curve belongs to the upper region of the judgment line (that is, the region represented by This region can be regarded as a normal operating region in the sense that it is located on this control curve.

In addition, the area below the judgment line 1 (that is, Io
This is the area represented by Vo, and is written as "BA".

), the power loss caused by the trigger transformer 40 and the power consumption by the trigger pulse generator 41 increase relative to the power supplied to the lamp, resulting in a situation in which regular power is not supplied to the lamp and it is not possible to maintain lighting. It is thought that the

That is, examples of such a situation include the following situations.

i) When the lamp is short-circuited ii) When the lamp is in the oven 1ii) When the high-frequency booster circuit 8 is open In such a case, the power supplied from the DC booster circuit 7 is reduced. - Most of the power consumption of the trigger pulse generator 41 (this is 'A4
It is written as 1J. ) and power loss due to the tricar transformer 40 (denoted as "rPL4゜"), so Vo-I o = A41 + PL40
−, (1) can be set. (However, this is ignored because it does not involve the power loss judgment operation by the transformer 32 of the high-frequency booster circuit 8.) Next, set the AC output voltage of the high-frequency booster circuit 8 to "Vo", the output current to "10", and trigger Letting the current flowing in the secondary winding 40b of the transformer 40 be "i4o", we move on to the task of finding the above-mentioned A41 and PL40.

First, the power loss PL4o is calculated by ignoring the iron loss and considering only the copper loss.If the conductor resistance of the winding is r, then PL40"F
It can be written as j 24o' r.

In the igniter circuit 9, the current limiting impedance element of the lamp is composed of the secondary winding 40b of the trigger transformer 4o and the capacitors 41b and 41c in the trigger pulse generator 41, but this combined impedance is due to rust conductivity. Therefore, i4° when the lamp is short-circuited is
The impedance (L) of the secondary winding 40b and the angular frequency (ω
) and the conductive reactance (xL=j
・ω・L) is approximately equal to the value obtained by dividing the output voltage Vo by the magnitude of ω・L).

In other words, 140 is proportional to Vo, and roughly speaking, vo is the output voltage of the DC booster circuit 7 depending on the turns ratio (n) of the transformer 32.
. Since there is a proportional relationship with

On the other hand, the power consumption A4 of the trigger pulse generator 41. teeth,
Since the power factor is close to 1, it is approximately equal to the product of vo and i4o,
In addition, i4o can be considered to be a value close to the charging current of the capacitor 41b in the trigger pulse generating section 41 by an approximation that ignores the transient state, and the value of i4o is determined by using the capacitor (C) of the capacitor 41b. It is approximately equal to the value obtained by dividing vo by the magnitude of the capacitive reactance (Xc = (j.omega..C)-') expressed as

In other words, i4o is ■. and V(, is proportional to VO (vo = n − Vo), so 140 ends up being (
It is proportional to VO)2 and is expressed as.

Substitute equations (2) and (3) into the right-hand side of equation (1), and convert both sides to ■. By dividing by , the following equation is easily obtained, which represents the decision line k.

As described above, the judgment line ρ is a straight line with a slope k that separates the normal operation area BN and the abnormal operation area BA, or the occurrence of an abnormality related to ii) and 1ii) described above is determined by l0 = constant ( This is written as ``work'').The upper region (C)l > and the lower region (C
L > In which region is the operating point P (Vo, Io)
It can be judged based on whether it belongs to.

That is, ■. In the case of <l'', it is determined that ii), fit) has occurred, and in the case of Io>bi, further work is performed.<k
-Vo, it is determined that the abnormality i) has occurred.

Expressing the above using the symbol (n) in set theory, if the operating point p (v6, 10) belongs to the region cL (PεCL), it is determined that the abnormal state of if), 1ii) has occurred, and the operating point P(VQ,lo)EBAnCH
In this case, it is determined that the abnormal condition i) has occurred.

The operating point P (Vo, Io) during normal operation is PεBNnc
It is clear from the above discussion that it belongs to m.

Therefore, the determination operation by the abnormality determination circuit 22 is performed as follows.

First, the output voltage V of the DC booster circuit 7. The voltage dividing resistor 104
．． By dividing the voltage by 104', the current value corresponding to VO at the judgment line, that is, the output current ■. The level of the output S15 of the amplifier 15 and the determination reference value are compared in the comparator 102.

Then, on the VO-10 characteristic diagram, the operating point P (Vo,
When Io) is below the determination line λ and belongs to the area BA, the output signal of the comparator 102 becomes L level and the transistor 106 is turned off.

Further, the transistor 112 is connected to the lighting/non-lighting detection circuit 20.
Since the transistor 106 is turned on upon receiving the non-lighting detection signal (S2o=“H”) from the transistor 106, the transistor 106 is turned off regardless of the output signal from the comparator 102.

In this way, when the transistor 106 is turned off, the capacitor 109 is charged, and when the potential of the negative input terminal of the comparator 115 exceeds the reference voltage E1, the output signal of the comparator 115 becomes L level. Therefore, the transistor 116 is turned off and an H signal is sent to the holding circuit 101, so that the transistor 100 is also turned off.

Therefore, relay 99 is turned off and its contact 6a is opened, so that the supply of battery voltage to DC booster circuit 7 is cut off.

In other words, the comparator 102 determines the area B, % BA
The lighting/non-lighting detection circuit 20 and the transistor 112 make judgments regarding the regions CM and CL.

(c-2-b, operation of output current abnormality detection circuit) Finally,
A protective operation by the output current abnormality detection circuit 26 when the high frequency booster circuit 8 is short-circuited at the output stage will be described.

The comparator 152 of the circuit 26 receives the output 5 of the amplifier 15.
The value of the comparison reference voltage is varied according to the magnitude of the output voltage vO of the DC booster circuit 7.

In other words, even if the lighting circuit 1 is operating normally, the output current ■0 is large at the beginning of lamp lighting, so if the comparison reference voltage of the comparator 152 is fixed, this state may be mistakenly interpreted as abnormal. This creates the inconvenience of making a judgment.

Therefore, the large output current I0 at the initial stage of lighting under normal conditions
and a large output current Io in the steady state of the lamp.
(This is due to the occurrence of a circuit abnormality.) In order to clearly distinguish between , Vo is set to a small value when Vo is small.

That is, when the output voltage vo of the DC booster circuit 7 is larger than a predetermined value, the Zener diode 147 becomes conductive, turning on the transistor 149 and turning off the transistor 150. When it is smaller than the predetermined value, transistor 149 is turned off and transistor 150 is turned on, so it is clear that the comparison reference value is smaller than in the previous case.

In either case, when the H signal output from the comparator 152 is sent to the holding circuit 101 via the diode 157, the transistor 100 is turned off, and the relay 99 is also turned off, so its contact 6a is opened and the signal is sent to the DC booster circuit 7. The supply of battery voltage will be cut off.

(d. Effect) Therefore, in the lighting circuit 1 described above, when the battery voltage is lower than a predetermined value at the time of starting the lamp, the inactivity period control section 21 applies the vIN, 4, to the inactivity period adjustment comparator 64. value, thereby reducing the control pulse P,
The upper limit of the duty cycle of the DC booster circuit 7 is raised, and the upper limit regulation on the output voltage v0 of the DC booster circuit 7 is relaxed, so that the output voltage necessary for starting the lamp is increased. Examine to ensure the value of.

After that, when the lamp lights up, the value of VIN64 is lowered below the normal value yH)l and the upper limit of the duty cycle of the control pulse Ps is lowered, thereby tightening the upper limit regulation of the output voltage Vo (in other words, lowering the upper limit). ), and during the period TH during which the unlit state of the lamp is detected and until the predetermined period TL has elapsed after the lamp is turned on, the supply voltage drop detection circuit 18 does not control the power below the rated power. Even after the lamp is turned on, it remains lit.

The reason for this is that the upper limit of the duty cycle of the control pulse PS is increased in response to a situation where the output voltage of the DC booster circuit 7 drops due to a sudden increase in load current when the lamp is lit. This is because, rather than this, if the DC boost operation is suppressed by lowering the upper limit, fluctuations in the output voltage Vo will be smaller.

In other words, when the load current increases rapidly due to lighting of the lamp, the DC
Even when the energy supply capacity of the booster circuit 7 is insufficient and the duty cycle of the control pulse PS is at its maximum, the output voltage V remains low. will be dropped.

In this state, the DC booster circuit 7 is forced to operate beyond its energy supply capacity, resulting in a large amount of loss.If the upper limit of the duty cycle of the control pulse PS is simply raised, the loss will only increase, leading to an increase in the load current. causes a voltage drop due to resistance loss in the power line, so the output voltage ■. On the contrary, it will decline.

Therefore, in such a situation, the control pulse PS would rather
By lowering the upper limit of the duty cycle of
If the upper limit regulation is made stricter and the DC booster circuit 7 operates within its capability, the loss will be smaller and the degree of drop in the output voltage V0 will be smaller.

(G. Effects of the Invention) As is clear from the above description, the lighting circuit for the vehicle discharge lamp of the present invention includes a DC boost circuit for boosting the DC input voltage and a control circuit for controlling the boost. In a lighting circuit for a vehicle discharge lamp, the circuit includes a DC input voltage drop detection circuit that detects that the DC input voltage has decreased to a predetermined value or less, and a lighting state that detects whether the discharge lamp is in a lighting state. Upper limit regulation for regulating the upper limit of the output voltage of the DC booster circuit by receiving detection signals from the detection circuit, DC input voltage detection circuit, and lighting state detection circuit and sending signals corresponding to these to the control circuit. means is provided, and when the upper limit regulating means is notified of a drop in the DC input voltage by a signal from the DC input voltage drop detection circuit at the time of starting the discharge lamp, the upper limit regulating means controls the DC input voltage until the discharge lamp is lit. The upper limit value regarding the output voltage of the booster circuit is set to a value larger than the upper limit value in a steady state after the discharge lamp is lit, and when the upper limit regulating means is notified of the lighting of the discharge lamp by a signal from the lighting state detection circuit, The present invention is characterized in that the upper limit regulating means regulates the upper limit value of the output voltage of the DC booster circuit to a value smaller than the upper limit value in a steady state of the discharge lamp until a predetermined time period elapses.

Therefore, according to the present invention, when the DC input voltage is low, the upper limit restriction on the output voltage of the DC booster circuit is relaxed by the upper limit restriction means at the time of starting the discharge lamp, and the permissible range of the output voltage is expanded upward. The output voltage required for starting the lamp and growing the arc can be obtained, and the voltage of the output voltage of the DC booster circuit can be increased by tightening the upper limit regulation until a certain period of time has passed after the discharge lamp is lit. Since the width of the descent is suppressed, it is possible to prevent the discharge lamp from going out once it has been lit.

[Brief explanation of the drawing]

1 to 10 show an example of the implementation of a lighting circuit for a discharge lamp for a vehicle according to the present invention. FIG. 1 is a circuit block diagram showing the overall circuit configuration, and FIG. 2 is a circuit showing a power supply system. figure,
Fig. 3 is a circuit diagram mainly showing the lighting control system, Fig. 4 is a circuit diagram mainly showing the abnormality determination circuit and the output current abnormality circuit, and Fig. 5 shows the current flow of each part of the circuit to explain the control operation. A graph diagram schematically showing temporal changes in voltage value and lamp luminous flux,
FIG. 6 is a graph showing the relationship between the output voltage and output current of the DC booster circuit and the determination line, and FIG. 7 is a schematic time chart for explaining the operation of the rest period control section when the input terminal is normal. 8 is a circuit diagram showing the configuration of a circuit that generates the reference voltage V, and FIG. 9 is a schematic time chart diagram for explaining the operation of the rest period control section when the input terminal drops. Figure 10 (A) to (C)
11 is a diagram for explaining the input voltage of the comparator for adjusting the idle period, and FIG. 11 is a schematic diagram for explaining the conventional problems. Explanation of symbols 1...Lighting circuit for vehicle discharge lamp, 7...DC booster circuit, 11...Discharge lamp, 12.
...Control circuit, 18.19...Low power control means, 20...Lighting state detection circuit, 21...Upper limit regulating means, 19.81.82.82', 83.83', 84...・
For DC input voltage drop detection circuit Applicant Koito Manufacturing Co., Ltd.← →--Graph diagram (Relationship between output voltage and output current of DC booster circuit) Figure 6 Figure 10 Figure 91. Continuation of IM

Claims (2)

[Claims] (1) A DC booster circuit for boosting DC input voltage;
A lighting circuit for a discharge lamp for a vehicle, which includes a control circuit for boosting the voltage, includes a DC input voltage drop detection circuit for detecting that a DC input voltage has decreased to a predetermined value or less, and a discharge lamp in a lighting state. The output voltage of the DC booster circuit is determined by receiving detection signals from the lighting state detection circuit and the DC input voltage detection circuit and the lighting state detection circuit and sending corresponding signals to the control circuit. Upper limit regulating means for regulating the upper limit value is provided, and when the upper limit regulating means is notified of a drop in the DC input voltage by a signal from the DC input voltage drop detection circuit at the time of starting the discharge lamp, the discharge lamp is turned on. Until then, the upper limit regulation means sets the upper limit value of the output voltage of the DC booster circuit to a value larger than the upper limit value in the steady state after lighting the discharge lamp, and then the lighting state detection circuit sets the lighting state of the discharge lamp to the upper limit value. When the regulating means is notified, the upper limit regulating means regulates the upper limit value of the output voltage of the DC booster circuit to a value smaller than the upper limit value in a steady state of the discharge lamp until a predetermined time has elapsed. A lighting circuit for a vehicle discharge lamp characterized by (2) Provide a low power control means that detects the DC input voltage and sends a signal to the control circuit to control the power of the discharge lamp below its rated power in response to a decrease in the DC input voltage, and also lights the discharge lamp. A claim characterized in that when the low power control means receives a signal from the upper limit regulation means when the DC input voltage is initially below a predetermined value, the power control below the rated power is temporarily stopped. The lighting circuit for the vehicle discharge lamp described in 1.