JPH03253436A - Headlamp lighting device for vehicle - Google Patents

Abstract

PURPOSE:To perform proper hot restart by controlling currents flowing to the electric discharge lamp-bulb with the integral values of an integrating means for integrating currents of primary winding of a transformer to discharge the currents at a specified time constant. CONSTITUTION:When a switch 2 is turned ON when an electric discharge lamp 5 is at a low temperature after a long time has elapsed after lights-out, a capacitor 12 has been discharged, and input voltage of a control circuit 6 is zero. At this time, a control circuit 6 sets an oscillating circuit 7 into oscillation at a low frequency to turn a transistor 8 ON/OFF at a low frequency. The secondary winding side of a transformer 3 has a low impedance with respect to a low frequency, so that a high current flows to heat up the electric discharge lamp in a short time, and lighting is stabilized. An integration constant determined by resistances 9, 10 and the condenser 12 is taken to be equal to the temperature time constant of the electric discharge lamp 5. When the lamp is lighted immediately after lights-out, the oscillating circuit 7 is oscillated at a high frequency by residual charge of the capacitor 12, and a high current does not flow to the electric discharge lamp 5. Proper hot start can thus be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a lighting device for a vehicle headlamp using a discharge lamp.

[Prior art]

For example, discharge lamps filled with metal vapor, such as mercury lamps and sodium lamps, are more advantageous than current filament-type bulbs in terms of size, weight, and high efficiency when used as vehicle headlights. There are many points.

In the above-mentioned lighting process of a discharge lamp, if a large current is passed immediately after the insulation breaks down, the gas temperature can be rapidly raised, making instant lighting possible. If this is set, the current that flows when the discharge reaches a stable state will be too large, resulting in an overspecified light amount and shortening the life of the discharge lamp. On the other hand, if the initial current is set to a relatively low value, there is a problem that it takes a long time from the time of starting until the stable light amount is reached.

For this reason, conventional discharge lamp lighting devices include a system that detects the bulb voltage and controls the current immediately after lighting, as described in JP-A-56-7392, for example, or JP-A-63-174,300. A method has been proposed in which the operation is switched at a certain time after lighting using a timer as described in the official gazette.

[Problem to be solved by the invention]

However, the former method requires a transformer for detecting the bulb voltage, resulting in increased size, weight, and cost, making it difficult to apply to vehicle headlights.

In addition, in the latter method, an excessive current flows even when the light is turned on after being turned off for a short period of time, such as when the light is stopped due to a traffic signal, or during a hot restart. There are problems with performance and durability, and unnecessary power consumption, so it is difficult to apply it to vehicle headlights.

The present invention has been made to solve the problems of the prior art as described above, and provides a small, lightweight, and low-cost vehicle headlight that can perform appropriate control even during a hot restart. The purpose is to provide a lighting device suitable for.

[Means to solve the problem]

In order to achieve the above object, the present invention is configured as described in the claims.

That is, in the present invention, a direct current/
It is equipped with an integrating means that integrates the current flowing through the primary winding of the transformer of the AC inverter and discharges it at a predetermined time constant, and is configured to control the current flowing through the discharge lamp bulb based on the integrated value. be.

The above integral value is approximately equal to the cumulative power consumption of the discharge lamp bulb, and the cumulative power consumption after the start of lighting operation is approximately equal to the temperature of the discharge lamp bulb, and since the integrating means discharges at a predetermined time constant, The integral value that remains when the lights are turned off again is different between after a long time has elapsed and after a short time (at the time of hot restart). Therefore, in the present invention, it is possible to flow a current corresponding to the temperature of the discharge lamp bulb at the start of lighting operation, and it is also possible to flow an appropriate current even at a hot restart.

[Embodiments of the invention]

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

In FIG. 1, DC power from a battery power supply 1 is supplied to one end of a primary winding of a transformer 3 via a switch 2, and then to a power supply system of a control circuit 6 and an oscillation circuit 7. The other end of the transformer 3 is grounded via a transistor 8 and a resistor 9. The transistor 8 is controlled on/off by the output of the oscillation circuit 7, and is controlled by the output of the oscillation circuit 7.
An intermittent current flows through the next winding in accordance with the output frequency of the oscillation circuit 7.

A discharge lamp bulb 5 is connected to the secondary winding of the transformer 3 via a current limiting capacitor 4.

A resistor 9 connected to the emitter terminal of the transistor 8
is a resistor for current detection, and this terminal voltage is the resistor 11
and a capacitor 12.

The output of this integrating circuit, that is, resistor 11 and capacitor 1
The voltage at the connection point with 2 is applied to the control circuit 6.

The control circuit 6 sends different control voltages (described in detail later) to the oscillation circuit 7 in accordance with the above-mentioned integrated voltage, and the oscillation circuit 7 turns on/off the transistor 8 with a signal having a frequency corresponding to the control voltage. That is, the oscillation circuit 7 operates as a voltage controlled oscillator.

Also, resistance 9. The integration time constant determined by the resistor 11 and the capacitor 12 is made approximately equal to the temperature time constant of the discharge lamp bulb 5.

Next, the effect will be explained.

First, when turning on the switch 2 to turn on the lamp after half a long time has elapsed since the lamp was turned off, that is, when the temperature of the discharge lamp bulb 5 is low, the electric charge of the capacitor 12 of the integrating circuit is
It is completely discharged through the resistor 11 and the resistor 9, and the input voltage to the control circuit 6 is zero. In this state, the control circuit 6 controls the oscillation circuit 7 to operate at a low oscillation frequency f□ (for example, 3k).
outputs a control voltage that oscillates at a frequency of around Hz). Therefore, the transistor 8 is turned on and off at a low frequency f1, and a high valve deactivation voltage is generated on the secondary side of the transformer 3 at a frequency f□ in accordance with the turns ratio.

Since the current limiting capacitor 4 has a low impedance with respect to the low frequency f□, the secondary load impedance of the transformer 3 is low, and as a result, a large transient current flows through the discharge lamp bulb 5.

Therefore, the temperature of the discharge lamp bulb 5 rises rapidly, and therefore a stable lighting state can be reached in a short time.

After lighting, the power consumed by the discharge lamp bulb 5 can be monitored by a resistor 9 for detecting the primary winding current of the transformer 3. This is due to constant voltage drive and the proportional relationship between the primary and secondary currents.
The voltage drop caused by the resistor 9 is proportional to the power consumption on the secondary side.

This secondary side power consumption is the sum of the power consumption of the current limiting capacitor 4 and the power consumption of the discharge lamp bulb 5. Normally, from the viewpoint of power utilization efficiency, the power consumption of the current limiting capacitor 4 is the sum of the power consumption of the discharge lamp bulb 5. Since it is set sufficiently small compared to the power consumption,
It can be said that the power consumption on the secondary side is approximately equal to the power consumption of the discharge lamp bulb 5.

Therefore, by integrating the voltage drop across resistor 9,
The cumulative power consumption of the discharge lamp bulb 5 can be known. The temperature of the discharge lamp bulb 5 during the lighting operation approximately corresponds to the above-mentioned integrated power consumption.

Further, since the integral time constant determined by the resistor 9, the resistor 11, and the capacitor 12 is made to almost match the temperature time constant of the discharge lamp bulb 5, the temperature of the discharge lamp bulb 5 during lighting operation is determined by the above-mentioned integral. It will roughly correspond to the value.

Therefore, as time passes after the switch 2 is turned on, the capacitor 12 is charged with an electric charge proportional to the temperature of the discharge lamp bulb 5.

Control times! I&6 is when the above-mentioned charged charge is above a certain amount, that is, when the terminal voltage is above a certain value.

The oscillation circuit 7 is set to a frequency fz higher than the frequency fz (for example, 10
It outputs a control voltage that causes oscillation at a frequency of kHz (kHz).

Therefore, a voltage with a high frequency f2 is generated on the secondary side of the transformer 3, which increases the impedance of the current limiting capacitor 4, so that a current smaller than that in the above case flows through the discharge lamp bulb 5 in a steady operating state. .

Then, in the case of a hot restart, where the discharge lamp is turned off and then turned on again within a short period of time, capacitor 12
Since the oscillation circuit 7 outputs a control signal of the output frequency f2, an unnecessary large current does not flow through the discharge lamp bulb 5.

In the above embodiment, the case where the output frequency of the oscillation circuit 7 is switched to two stages, a low value f and a high value f2, was illustrated, but it can be changed in multiple stages or continuously depending on the terminal voltage of the capacitor 12. You can also change the frequency.

Next, FIG. 2 is a circuit diagram of a second embodiment of the present invention.

In this embodiment, in order to cope with the fact that the temperature time constant of the discharge lamp bulb 5 differs greatly between when the temperature rises and when heat is dissipated, the time constant during charging and the time constant during discharging in the integrating circuit are set to different values. This is what I did.

Note that, in general, the temperature time constant during heat radiation has a larger value.

In FIG. 2, the terminal voltage of resistor 9 is
is applied to the integrator circuit via. In addition, capacitor 12
The output terminal of is grounded through a discharge resistor 13.

In the above configuration, the resistance value of the resistor 11 is R2, and the resistance value of the resistor 1 is R2.
If the resistance value R1 of 3, the capacitance of capacitor 12 is 02, and the resistance of diode 1o is ignored, the integration time constant tuP when charging the integrating circuit, that is, when the temperature rises, is tup=Rz"Xcz/(Rz+Ra) - = (1
), and the time constant t1゜wn during discharge, that is, heat radiation, is t sown = Rz X Cz ・”
(2) becomes.

As mentioned above, the time constants during charging and discharging can be changed, so by appropriately setting the values of R2, R1, and c2, the temperature time constant during temperature rise and the temperature time constant during heat dissipation can be changed. The charging and discharging time constants can be set to match.

Next, FIG. 3 is a diagram of a third embodiment of the present invention.

This embodiment shows another circuit for obtaining the same effect as the embodiment of FIG.

In Fig. 3, if the resistance value of the resistor 1 is R2, the resistance value of the resistor 15 is R4, and the capacitance of the capacitor 12 is 02, and the resistance of the diode 14 is ignored, then the integration when the integrating circuit is charged, that is, when the temperature rises, is The time constant tuP is tuF=R2XC2-(3), and the time constant t do during discharge, that is, heat radiation.
wn is t down=R2・R4(R2+R4) X C2
-(4).

Therefore, in this case as well, by appropriately setting the values of R2, R, and Cz, it is possible to set the charging and discharging time constants to match the temperature time constants during temperature rise and temperature time constants during heat dissipation. I can do it.

Next, FIG. 4 is a circuit diagram of a fourth embodiment of the present invention.

This embodiment eliminates the influence of ambient temperature.

In FIG. 4, the voltage at the output terminal of the capacitor 12 is
It is input to the positive phase input terminal of the differential amplifier 16.

Further, the series circuit of the temperature sensitive resistors 17 and 18 is connected to the reference power supply 19.
The voltage at the connection point of both temperature-sensitive resistors is connected to differential amplifier 1.
It is input to the negative phase input terminal of No.6.

The resistance value of the temperature-sensitive resistor 17 increases linearly as the ambient temperature increases, and the resistance value of the temperature-sensitive resistor 18 decreases linearly. By making the absolute values of these proportional coefficients equal, the voltage division ratio can be changed depending on the temperature while keeping the series combined resistance of the two temperature sensitive resistors 17 and 18 constant.

Therefore, the voltage at the negative phase input terminal of the differential amplifier 16 decreases linearly with respect to ambient temperature changes. Therefore, the output of the differential amplifier 16 is the sum of the temperature rise after the discharge lamp bulb 5 is turned on and the ambient temperature, so the control circuit 6 detects the absolute temperature of the discharge lamp bulb 5 without depending on the ambient temperature. be able to.

〔Effect of the invention〕

As explained above, according to this invention.

By configuring the current control of the discharge lamp bulb based on the cumulative power consumption after the start of lighting operation, appropriate control can be performed even in the event of a hot restart, resulting in longer life and higher reliability. In addition, since a special transformer or the like is not required, effects such as miniaturization, weight reduction, and cost reduction of the device can be obtained.

Furthermore, in the second and third embodiments, in addition to the above-mentioned effects, it is possible to perform control that is suitable for the difference in temperature time constant between when the temperature of the discharge lamp bulb increases and when it dissipates heat. 4
In this embodiment, it is possible to achieve control that is not affected by the ambient temperature.

[Brief explanation of drawings]

1 to 4 are circuit diagrams of embodiments of the present invention, respectively. <Explanation of symbols> l... Battery power source 2... Switch 3... Transformer 4... Capacitor 5... Discharge lamp bulb 6... Control circuit 7... Oscillation circuit 8... Transistor 9... Resistor 0.14... Diode 1.13.15... Resistor 2... Capacitor 6... Differential amplifier 7.18... Temperature sensitive resistor 9... Reference power supply

Claims (1)

[Scope of Claims] A device for lighting a discharge lamp with AC power generated in the secondary winding of the transformer by intermittent DC current applied to the primary winding of the transformer at a predetermined frequency, comprising: 1 of the transformer; A vehicle front comprising: an integrating means for integrating the current flowing through the next winding and discharging it at a predetermined time constant; and a frequency controlling means for controlling the frequency based on the output of the integrating means. Light lighting device.