JPH09232089A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a feeling at lighting time, and lengthen the sevice life of a discharge lamp by reliably starting it at starting time of the discharge lamp such as a metal halide lamp. SOLUTION: When a discharge lamp is started, tube voltage is detected by a voltage detecting circuit 3, and the operation is performed on preset values of a control current at stable time and starting time from its detecting voltage by operation circuits 5 and 6. A tube electric current detected by an electric current detecting circuit 4 and these preset values are compared with each other, and inverter output voltages at stable time and starting time are controlled by an inverter output voltage control circuit 9. Control is performed by an output control circuit 10 so that output voltage to the discharge lamp is not reduced until a sufficient tube electric current flows to the discharge lamp just after discharge is started by comparing the tube electric current detected at starting time with a preset electric current.

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 having improved control of starting a discharge lamp such as a metal halide lamp.

[0002]

2. Description of the Related Art When a discharge lamp is used as a headlamp of an automobile, the discharge lamp has to be instantly turned on and restarted. In the case of instant lighting, a high voltage pulse of, for example, 15 KV or more is applied at the time of starting the discharge. Immediately after starting, it is necessary to immediately flow 6 times the rated current to start up rapidly.
In the case of restart, the discharge cannot be started unless a high voltage of 25 KV (max) is applied. When restarting, the temperature of the tube is still high and the pressure in the tube is high, so the discharge start voltage is high as described above, but the starting current for instantaneous light emission is that the tube temperature has not yet dropped. It requires less than when it is cold.

FIG. 3 is a block diagram showing the configuration of a control system of a conventional discharge lamp lighting device for instantaneously lighting the discharge lamp as described above. This control system detects the tube voltage and the tube current at the time of starting the discharge lamp by the voltage detection circuit 3 and the current detection circuit 4 using the sensors 1 and 2 and performs correction control at the start of lighting. From the tube voltage of the discharge lamp detected at times, the stable output calculation circuit 5 and the startup output calculation circuit 6 calculate the set values of the control current when the discharge lamp is stable and the control current when the discharge lamp is started. At this time, the rising correction timer circuit 7 intentionally delays the control immediately after the start.

The PWM control circuit 8 compares the control signal (set value) from the arithmetic circuits 5 and 6 with the detection current (tube current) detected at the time of starting and outputs a PWM signal to control the inverter output voltage. The circuit 9 controls the inverter output voltage to the discharge lamp according to the PWM signal. As a result, the discharge lamp can shift to a stable state from the start of lighting.

Here, regarding the circuit operation at the time of starting the discharge lamp, since the detection tube voltage is maximum and the detection tube current is zero before the start of discharge, the inverter output voltage maintains the maximum voltage until the discharge starts, After lighting, control is performed so that a predetermined current value is obtained according to the tube voltage.

Further, when the discharge lamp is momentarily turned on, an undershoot or the like occurs in the light emission output. Therefore, a rise correction timer circuit 7 is provided to suppress the undershoot.

[0007]

However, in the conventional discharge lamp lighting device as described above, an appropriate phase delay control is required in the current control circuit when feedback control of the discharge lamp is performed. And if this phase delay is too small, it may cause the circuit to oscillate or malfunction due to the influence of noise, etc.If the phase is too slow, it cannot respond to changes in the discharge lamp even during stable lighting, and the lamp goes out on the way. It was a cause of

Further, if the phase is optimized when it is stable, the control becomes too early this time when a sufficiently high applied voltage is required when the discharge lamp is restarted, and discharge is started by a high-voltage pulse. Since the inverter output voltage drops before it stabilizes, the discharge is likely to extinguish in the middle, and the high-voltage start pulse is 20 to 3 until normal lighting starts.
There were cases where 0 or more pulses were applied. This is because the discharge is unstable until a full-scale arc discharge is made, and a high applied voltage is required due to a large delay phase.

That is, as shown in the inverter output voltage waveform diagram at the time of restart of FIG. 4, several tens of high-voltage start-up pulses are generated in some cases, and discharge-disappearance blinking is repeated. There is a problem that the feeling is bad and the life of the discharge lamp is shortened due to the stress on the electrodes of the discharge lamp due to the high voltage pulse.

The present invention has been made by paying attention to the above-mentioned problems, and it is possible to surely start the discharge lamp at the time of starting and restarting the discharge lamp, and to improve the feeling at the time of starting. It is an object of the present invention to provide a discharge lamp lighting device capable of extending the life of the discharge lamp.

[0011]

DISCLOSURE OF THE INVENTION A discharge lamp lighting device according to the present invention compares a tube current of the discharge lamp with a preset set current at the time of starting the discharge lamp, and a tube sufficient for the discharge lamp immediately after the start of discharge. It is provided with an output control circuit for controlling so that the output voltage to the discharge lamp is not lowered until a current flows.

In the above lighting device, an output voltage control circuit for controlling the output voltage at the time of starting based on the control current determined by the tube voltage of the discharge lamp and the tube current of the discharge lamp is provided. Is.

[0013]

1 is a block diagram showing the configuration of a control system according to an embodiment of the present invention, and the same reference numerals as those in FIG. 3 denote the same components. In the figure, reference numeral 10 indicates that the tube current of the discharge lamp is compared with a preset current at the time of starting the discharge lamp (when restarting) until a sufficient tube current flows in the discharge lamp immediately after the start of discharge. It is a start-time output control circuit that controls so as not to reduce the output voltage to the discharge lamp.

Others have the same circuit configuration as that of FIG. 3, and the inverter output voltage control circuit 9 is based on the set value of the control current determined by the detection tube voltage of the discharge lamp and the detection tube current of the discharge lamp. It is configured to control the inverter output voltage at startup.

The basic operation of the control system of the discharge lamp lighting device configured as described above is the same as that of the control system of FIG. 3 and therefore will be omitted, but at the start of lighting of the discharge lamp, the output control circuit 10 causes The detection tube current is compared with the set current, and the inverter output voltage is controlled so as not to decrease until the discharge lamp that has started discharging reaches a stable state in which sufficient tube current flows.

As a result, it is possible to prevent the output voltage from dropping immediately after the discharge is started and the discharge which is still unstable is extinguished as in the conventional case. Further, since the phase of the control system is not extremely delayed, the lamp does not extinguish even during steady lighting, and the lighting can be continued stably.

Here, as the set current at the time of starting,
For example, 35W type metal halide lamp (rated 85
V, 410 mA) was set to about 100 mA to 200 mA, and good results were obtained. As a starting characteristic, the cold start from the cold state of the discharge lamp was started by a single high-voltage drive pulse. Furthermore,
Even in the hot restart from a state where the tube temperature of the discharge lamp, which is difficult to start, is still high, the lighting could be stably started with a few high-voltage start pulses of about 1 to 3.

FIG. 2 is a diagram showing a restart lighting waveform according to the above-mentioned embodiment, and shows an inverter output voltage waveform.
As shown in the figure, the unstable extinction of the discharge just after the start-up has disappeared.

As described above, in this embodiment, a simple circuit is added, and the inverter output voltage is optimally controlled so as not to drop until the tube current of the discharge lamp sufficiently flows to reach a stable state (normal lighting). Therefore, it is possible to ensure the start-up of the discharge lamp and the start-up of the discharge lamp.

Further, since it is possible to start the discharge with 1 to 3 high-voltage start-up pulses, which are significantly smaller than those of the prior art at the time of start-up, the lighting feeling at start-up is greatly improved, and the discharge lamp electrode Stress is also reduced and the life of the discharge lamp can be extended.

[0021]

As described above, according to the present invention, when the discharge lamp is started, the output voltage is prevented from decreasing until the tube current sufficiently flows and becomes stable. Therefore, at the time of starting and restarting. The effect that the startup can be ensured is obtained.

Further, there is an effect that lighting can be started with a few high-voltage starting pulses, the lighting feeling at the time of starting can be improved, and the life of the discharge lamp can be extended.

[Brief description of drawings]

FIG. 1 is a block diagram showing the configuration of a control system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a restart lighting waveform according to an embodiment.

FIG. 3 is a block diagram showing the configuration of a conventional control system.

FIG. 4 is a diagram showing a restart lighting waveform of a conventional example.

[Explanation of symbols]

 3 Voltage Detection Circuit 4 Current Detection Circuit 5 Stable Output Calculation Circuit 6 Start Output Calculation Circuit 7 Rise Correction Timer Circuit 8 PWM Control Circuit 9 Inverter Output Voltage Control Circuit 10 Start Output Control Circuit

Claims (2)

[Claims] 1. When the discharge lamp is started, the tube current of the discharge lamp is compared with a preset set current so that the output voltage to the discharge lamp is not lowered until a sufficient tube current flows in the discharge lamp immediately after the start of discharge. A discharge lamp lighting device comprising an output control circuit for controlling the discharge lamp. 2. An output voltage control circuit for controlling the output voltage at the time of starting based on the control current determined by the tube voltage of the discharge lamp and the tube current of the discharge lamp. The discharge lamp lighting device according to 1.