JP3309275B2 - Discharge lamp lighting device - Google Patents

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 particularly suitable for vehicles.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a circuit configuration of a conventional discharge lamp lighting device which is mainly used for a vehicle headlamp and which can be turned on instantaneously using a DC power source such as a battery.

In FIG. 4, reference numeral 1 denotes a DC power supply such as a battery, 2 denotes a lighting switch, and 3 denotes a DC-DC (step-up) which boosts a DC voltage (input voltage Vcc) input from the DC power supply 1 via the switch 2. This is a DC boosting circuit composed of a (DC-DC) converter, and has a capacitor C1 at an input portion. Reference numeral 4 denotes a DC-AC (DC-AC) inverter for converting boosted DC to AC and outputting lighting power, and reference numeral 5 denotes starting for outputting a starting high voltage pulse for starting discharge when the discharge lamp 6 is turned on. Circuit.

In FIG. 4, reference numeral 7 denotes a power supply circuit such as a regulator for generating a stabilized power supply voltage Vdd for control from the input voltage Vcc. Control unit for turning on instantaneously, 9
Is a protection circuit unit for performing circuit protection when output is abnormal. The power supply voltage Vdd is supplied from a power supply circuit 7 together with a control unit 8 via a smoothing capacitor C2. A reset circuit 10 outputs a reset signal to the protection circuit section 9 when the power supply voltage Vdd rises, and is constituted by a series circuit of a capacitor C3 and a resistor R1.

In the lighting device configured as described above, lighting and extinguishing are performed by turning on and off the switch 2. At the time of lighting, the lighting control unit in the DC booster circuit 3 controls the operation of the discharge lamp 6 from start to stable. Is controlled according to the lamp voltage.

[0006] Further, such a lighting device generally includes a power supply circuit 7 for reducing the input voltage Vcc to the control power supply voltage Vdd, and stabilizes the drive voltage of the control unit 8. The power supply circuit 7 has a circuit configuration capable of performing step-up / step-down control when the input voltage Vcc decreases and the power supply voltage Vdd becomes higher than the lighting sustaining voltage Vt which is the lowest voltage at which lighting is possible.

The control power supply voltage Vdd is stabilized by, for example, a large input voltage fluctuation due to a battery voltage, and an increase in the input current due to a warm-up operation at a rated current or more at the time of starting the discharge lamp. This is because a voltage drop occurs. In the circuit of FIG. 4, as described above, the input voltage Vcc is input, stabilized at a predetermined voltage Vdd, and used as a control voltage.

It is common for a lighting circuit for a vehicle to incorporate a protection circuit section 9 in case of an input / output abnormality in order to ensure safety. Protection is provided from output short-circuit, output open, etc. As a configuration of the protection circuit unit 9 for performing these protections, a configuration using a logic circuit or a microcomputer is mainstream. When an abnormal state occurs, an abnormal signal (not shown) is input to the protection circuit unit 9 and the circuit is not shown. Protection is provided, and the abnormal state is held.

Further, the power supply of the protection circuit section 9 is stabilized similarly to the control section 8. When the power supply rises, the reset signal from the reset circuit 10 is input as described above, and the circuit is reset to the initial state. Start after being done. The reason why the reset is necessary is that, for example, when a part of the logic circuit includes a memory circuit and the circuit is started without clearing and the previous state remains, a normal operation cannot be performed.

FIGS. 5A and 5B are diagrams showing the operation of the reset circuit 10. FIG. 5A shows the power supply voltage Vdd of the control section when the switch 2 is turned on and off, and FIG. 5B shows the output pulse (reset signal) of the reset circuit 10. , (C) show the on / off state by the lamp light of the discharge lamp 6, and (d) shows the state of the capacitor C1.
Shows voltage .

When the lighting switch 2 is turned on, the input voltage Vcc is supplied to the lighting circuit. At the same time, the output voltage of the power supply circuit 7 rises. Upon receiving the rising voltage, the reset circuit 10 generates a reset signal for a predetermined time. Is output.
While the reset signal is being generated, an output stop signal is output from the protection circuit unit 9 to the control unit 8.
After the reset signal stops, the discharge lamp 6 is turned on.

Next, when the switch 2 is turned off, the above-mentioned lighting sustaining voltage Vt, which is the lowest voltage at which the circuit output can be turned on,
The charge stored in the capacitor C1 of the DC booster circuit 3 is discharged until the lighting is performed, and the lighting is stopped. When the lighting output becomes equal to or lower than the lighting sustaining voltage Vt, the protection circuit 9 operates to stop the lighting or stop the extinction. Becomes The power supply voltage Vdd at that time is in a state of a rated voltage or lower.

Thereafter, when the switch 2 is kept off,
Capacitor C1 charged by input voltage Vcc
Voltage continues to decrease due to the discharge, and the power supply voltage Vdd for control also decreases accordingly. And the capacitor C
When the switch 2 is turned on again in a state where the voltage charged to 1 and the power supply voltage Vdd are completely reduced or close to them, the discharge lamp 6 is restarted in the same manner as described above.

[0014]

However, in the conventional discharge lamp lighting device as described above, the input voltage Vc
The potential of the capacitor C1 at the input of the DC booster circuit 3 required for the DC-DC converter to which c is supplied, and the potential of the capacitor C2 at the output of the power supply circuit 7 for controlling power supply voltage Vdd noise and ripple absorption are reduced. If switch 2 is turned on again after an instantaneous interruption while it cannot be turned off, the condition as shown in FIG.
The voltage charged in the sensor C1 is released from the input voltage Vcc.
The voltage drops below the lighting maintenance voltage Vt due to the power supply, the discharge lamp 6 turns off or goes out, the protection circuit unit 9 stops output, and the control unit 8 and the protection circuit unit 9 operate only when the power supply voltage Vdd is slightly reduced. The switch 2 is turned on again while the operation is continued.

Therefore, the reset signal from reset circuit 10 is generated at the rising edge of the voltage waveform of power supply voltage Vdd. Therefore, the level of the reset signal is insufficient, and the stopped state of discharge lamp 6 cannot be released. To
There is a problem that the unlit state may be maintained.

The present invention has been made in view of the above-mentioned problems. Even when the lighting switch is momentarily interrupted, the protection circuit can be reliably reset and the non-lighting state can be prevented from being held. It is an object of the present invention to provide a discharge lamp lighting device capable of always lighting instantly and re-lighting.

[0017]

The discharge lamp lighting device according to the present invention is configured as follows.

(1) A control unit for controlling a lighting current higher than the rated value at the time of starting the discharge lamp, a protection circuit unit having a protection function against an abnormal output of the lighting circuit, and a lighting circuit for the protection circuit unit. And a reset circuit for resetting the capacitor to a predetermined state when the voltage of the capacitor charged with the input voltage from the DC power source rises from the minimum voltage at which the discharge lamp can be turned on and maintained to a startable voltage or more.

(2) In the configuration of (1), the reset circuit detects the voltage of the capacitor charged with the input voltage from the DC power supply of the lighting circuit, and generates a reset signal in accordance with the detected voltage. Then, the reset signal is input to the protection circuit section.

(3) In the configuration of the above (1) or (2), a DC boosting circuit comprising a DC-DC converter for boosting an input voltage from a DC power supply, and a discharge lamp which converts boosted DC to AC and converts the DC to AC. A lighting circuit is composed of a DC-AC inverter that supplies lighting power to the lighting circuit.
From the input voltage from the
The lamp is turned off and the discharge lamp is turned on when the voltage is higher than the starting voltage .

[0021]

FIG. 1 is a block diagram showing a circuit configuration of a discharge lamp lighting device according to an embodiment of the present invention. The same reference numerals as in FIG. 4 denote the same components.

In FIG. 1, 1 to 9 are the same as those shown in FIG. Reference numeral 11 denotes a reset circuit corresponding to the reset circuit 10 in FIG. 4, which uses a control power supply voltage Vdd output from the power supply circuit 7 as a drive voltage,
Having a hysteresis characteristic composed of
And a pulse generation circuit section 13 that receives the output of the comparator 12 and generates a pulse-shaped reset signal. The reset signal is input to the protection circuit section 9.

The reset circuit 11 has an input voltage Vcc
Is compared by a comparator 12 with a voltage obtained by dividing the reference voltage Vref by resistors R4 and R5, and a reset signal is output from a pulse generation circuit unit 13 based on the comparison result. Is output. That is, the comparator 12 of the reset circuit 11 determines whether the capacitor C charged with the input voltage Vcc is
1 has a hysteresis characteristic in which the output level changes so that the discharge lamp 6 is turned off when the voltage of the discharge lamp 6 is equal to or lower than the above-mentioned lighting maintenance voltage and the output level changes so that the discharge lamp 6 is turned on when the voltage is higher than the starting voltage. The pulse generating circuit 13 is a reset signal (reset pulse) corresponding to the output level.
Occurs. In this reset circuit, R6 and R7 are resistors.

In the lighting device configured as described above, when the discharge lamp 6 is started, the control unit 8 controls the discharge lamp 6 so that a lighting current higher than the rated value is applied to instantaneously light the lamp. The DC booster circuit 3 and the DC-AC The protection function of the protection circuit section 9 operates against an abnormal output of the lighting circuit including the inverter 4. The reset circuit 11 also activates the protection circuit section 9 when the voltage of the capacitor C1 charged with the input voltage Vcc by the DC current of the lighting circuit rises from the minimum voltage at which the discharge lamp 6 can be maintained to be lit to the startable voltage or more.
Is reset to return to a predetermined state.

FIG. 2 is a diagram showing the operation of the comparator 12 of the reset circuit 11. Input voltage Vcc is charged
When the voltage of the obtained capacitor C1 decreases from the rated voltage Vr and decreases to the lighting maintenance voltage Vt, the output (voltage) of the comparator 12 changes from the level Va to the level Vb. The level Vb is maintained even if the voltage further decreases. But,
Since the power supply of the comparator 12 is obtained from the input voltage Vcc, the voltage starts decreasing from a certain voltage.

Conversely, a capacitor charged with the input voltage Vcc
When the voltage of the sensor C1 increases, the level does not reverse even when the lighting maintaining voltage Vt is reached, and the level is reversed when the voltage further increases to the starting voltage Vs. That is, the output of the comparator 12 changes from the level Vb to the level Va. Thus, the comparator 12 has a hysteresis characteristic. Note that the comparator section is a generally known circuit, and thus the description is omitted.

The pulse generation circuit section 13 which operates in response to the output of the comparator 12 includes the comparator 1
A pulse is generated to reset the protection circuit section 9 when the output of the second circuit changes from the level Vb to the level Va.

Basically, the basic operation is such that a reset pulse is generated to reset the protection circuit section 9 when the power supply voltage Vdd changes from the lighting sustaining voltage of the lighting circuit to the starting voltage or more. I do.

That is, although the protection circuit section 9 could not be reset because the level was low in the related art, the reset can be surely performed by using the comparator 12 in the present embodiment.

Further, in the conventional method, there was a case where the reset was applied even between the lighting maintaining voltage and the starting voltage. However, originally, the protection circuit section 9 generates an abnormality, holds the abnormality, and resets the input voltage again. Should be reset when turned on. In this embodiment, the capacitor charged with the input voltage is
The protection circuit section 9 is reset when the voltage of C1 rises from the lighting sustaining voltage, that is, the voltage at which the discharge lamp 6 is always turned off, to the starting voltage, that is, the voltage at which the discharge lamp 6 is always turned on. Can be reset reliably.

FIG. 3 is a diagram showing the operation of the reset circuit 11 of this embodiment. FIG. 7A shows a control power supply voltage Vd.
d and (b) show the reset signal, (c) shows the on and off states of the lamp, respectively, and (d) shows the state of the capacitor C1.
The voltage indicates the rated voltage Vr, the starting voltage Vs, and the lighting maintenance voltage Vt as the point levels.

As shown in FIG. 3, when the lighting switch 2 is turned on, the input voltage Vcc is supplied, and at the same time, the power supply voltage Vdd for control rises. 11 outputs a reset signal. While the reset signal is being output, the protection circuit unit 9 outputs a signal to stop the output of the lighting circuit to the control unit 8, so that the discharge lamp 6 is turned on after the output of the reset signal is stopped.

Next, when the switch 2 is turned off, the lamp is lit by the electric charge stored in the capacitor C1 until the output of the lighting circuit reaches a lighting sustaining voltage which is the lowest voltage at which the lighting can be performed. Leads to. At this time, the power supply voltage Vdd is a rated voltage or a state lower than the rated voltage. Thereafter, when the OFF state of the switch 2 continues, the input voltage Vcc of the capacitor C1 charged
The voltage continues to decrease due to the discharge of the capacitor C1, and the power supply voltage Vdd also decreases accordingly. Then, when the switch 2 is turned on again in a state where the voltage of the capacitor C1 charged with the input voltage Vcc and the power supply voltage Vdd are completely reduced or close to them, the discharge lamp 6 is restarted in the same manner as described above. .

Here, as described above, while the potentials of the capacitors C1 and C2 are not completely lowered, the switch 2
In this embodiment, a sufficient reset signal can be output by the reset circuit 11 even if is turned on again after an instantaneous interruption. That is, the capacitor C1 is charged as described above.
The detected voltage is detected, and when the voltage changes from below the lighting maintaining voltage of the lighting circuit to above the starting voltage, the protection circuit section 9 can be reliably reset.

As described above, the reset pulse is generated by the potential difference that has risen from the lighting stop voltage to the starting voltage for any on / off operation of the switch 2, so that when the switch 2 is momentarily interrupted, Also, the protection circuit section 9 can be reliably reset, the non-lighting state of the discharge lamp 6 can be prevented from being held, and instantaneous lighting and relighting can be always performed.

[0036]

As described above, according to the present invention, the protection circuit can be reliably reset even if the lighting switch for turning on and off the lighting input voltage is momentarily interrupted, and the non-lighting state is maintained. Can be prevented, and there is an effect that instantaneous lighting and re-lighting can always be performed.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of an embodiment of the present invention.

FIG. 2 is an explanatory diagram illustrating an operation of a comparator of the reset circuit according to the embodiment.

FIG. 3 is an explanatory diagram showing the operation of the reset circuit according to the embodiment;

FIG. 4 is a block diagram showing a circuit configuration of a conventional example.

FIG. 5 is an explanatory diagram showing the operation of a conventional reset circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DC power supply 2 Switch 3 DC booster circuit 4 DC-AC inverter 5 Starter circuit 6 Discharge lamp 7 Power supply circuit 8 Control part 9 Protection circuit part 11 Reset circuit 12 Comparator 13 Pulse generation circuit part

Claims (3)

(57) [Claims] 1. A control unit for controlling a lighting current higher than a rated value at the time of starting a discharge lamp, a protection circuit unit having a protection function against an abnormal output of the lighting circuit, and a protection circuit for the lighting circuit. A reset circuit for resetting the capacitor to a predetermined state when the voltage of the capacitor charged with the input voltage from the DC power source rises from the minimum voltage at which the discharge lamp can be turned on and maintained to a startable voltage or more. Lighting device. 2. The reset circuit is connected to a DC power supply of a lighting circuit.
2. The method according to claim 1, wherein a voltage of the capacitor charged with the input voltage is detected, a reset signal is generated in accordance with the detected voltage, and the reset signal is input to the protection circuit unit. The discharge lamp lighting device as described in the above. 3. A lighting circuit comprising a DC boosting circuit comprising a DC-DC converter for boosting an input voltage from a DC power supply, and a lighting circuit comprising a DC-AC inverter for converting boosted DC into AC and supplying lighting power to a discharge lamp. And the lighting circuit is
Detects the input voltage from the DC power supply and keeps it below the lighting maintenance voltage.
To turn off the discharge lamp, and turn on the discharge lamp above the starting voltage.
The discharge lamp lighting device according to claim 1 or 2, wherein the that.