JPH11339984A - Discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the charging time of a capacitor for giving the discharging current to a primary side of a starter transformer, and to raise the frequency of the high voltage pulse to be repeatedly generated in a discharge lamp lighting device having the starter transformer for applying the high voltage pulse to the discharge lamp. SOLUTION: Two capacitors C1, C2 are connected in series, and the two capacitors C1, C2 are continuously charged each other by the output in each half-cycle of a DC/AC inverter 5 so as to conclude charging of the two capacitors C1, C2 in one cycle. A switching park gap 8 as a trigger element is electrified by the twice charged voltage of the two capacitors C1, C2, and the discharging current of the capacitors C1, C2 is made to flow to a primary coil of the starter transformer T1, and the high voltage pulse generated in a secondary coil of the transformer T1 is applied to the discharge lamp 1 for lighting.

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 suitable for an automobile.

[0002]

2. Description of the Related Art FIG. 3 is a block diagram showing the schematic structure of a general discharge lamp lighting device for an automobile. In the figure,
1 is a discharge lamp, 2 is a battery, 3 is a DC-DC converter which is a DC boosting circuit for boosting the output voltage of the battery 2,
4 is a rectifier circuit, and 5 is a D for converting the boosted DC to AC.
In the C-AC inverter, the converter 3 and the inverter 5 are controlled by a control circuit 6. Reference numeral 7 denotes a trigger circuit which constitutes a start-up circuit together with the start-up transformer T1. The start-up transformer T1 causes the discharge lamp 1 to generate a high-voltage pulse for starting.

In the above circuit configuration, the power supply voltage of 12 V or 24 V of the battery 2 is boosted to a DC voltage of about 400 V by the DC-DC converter 3, and the DC high voltage is increased to several hundred Hz by the DC-AC inverter 5. The voltage is converted into an AC voltage and supplied to the discharge lamp 1 to keep the discharge lamp 1 lit. The output of the inverter 5 has an AC or DC waveform of several hundred volts when it is not added (when the discharge lamp is turned off).

FIG. 4 is a diagram showing a configuration of the starting circuit in a conventional discharge lamp lighting device. In the figure, 8 is a switching spark gap, 9 is a diode bridge circuit for rectification, 10 is a converter transformer of the DC-DC converter 3, a primary winding 10a is connected to the battery side, and 2
On the secondary side, the secondary winding 10b to the inverter side and the auxiliary winding 1
0c is provided. R1 is a resistor, D1 is a diode, and C1 is a capacitor.

FIG. 4A shows a circuit using the AC output of the DC-DC converter 3 before the rectification, in which half-wave rectification is performed. In this case, the AC output before the rectification is rectified by the resistor R1 and the diode D1 to charge the capacitor C1. Spark gap 8 turns on (conduction)
Then, the discharge current of the capacitor C1 instantaneously flows through the primary winding of the starting transformer T1, and a high voltage corresponding to the turn ratio with the primary winding is generated in the secondary winding. 1
Lights up.

FIG. 4B shows a circuit using the AC output before rectification of the DC-DC converter 3 and performs full-wave rectification similarly to FIG. In this case, the capacitor C1 is charged via the resistor R1 by the output that has been full-wave rectified by the diode bridge circuit 9, and when the charging voltage exceeds the breakdown voltage of the spark gap 8 as described above, the voltage of the starting transformer T1 is increased. Capacitor C1 for the next winding
To generate a high voltage in the secondary winding of the starting transformer.

FIG. 4C shows a circuit in which the converter transformer 10 is provided with a three-wire winding, and shows a case of an auxiliary winding system. In this case, the third side
The auxiliary winding 10c is provided to generate a voltage corresponding to the turn ratio with the primary winding 10a, and the output is rectified by the resistor R1 and the diode D1 to charge the capacitor C1. , (B), the discharge lamp 1 is turned on.

FIG. 5 is a diagram showing the relationship between the output of the DC-DC converter 3 and the charging time of the capacitor C1.
In a single converter, as shown in FIG. 5A, before the converter output is rectified, the peak voltage is generally higher than after the rectification, but the converter itself originally performs duty control. The on-duty also changes depending on the load. Then, when the above-described high-voltage pulse for starting is generated, the on-duty is in a relatively small state, so that charging requires time. Also, as shown in FIG. 5B, the same applies to the case where the on-duty is small in a two-wheel push-pull type converter.

The switching spark gap 8 has a structure in which two metal electrodes each having an electrode activator on the surface are arranged at a predetermined distance in an inert gas and covered with a ceramic insulator or the like. And functions as a breakdown switch element.

[0010]

However, the conventional discharge lamp lighting device as described above has the following problems.

In the circuit shown in FIG. 4A, the circuit configuration is simplified by half-wave rectification, but the charging time for the capacitor becomes longer, and the required repetition frequency of the high-voltage pulse (Equation 1) is obtained.
0 Hz).

In the circuit of FIG. 4B, the charging time for the capacitor is shortened by full-wave rectification, but the circuit configuration becomes complicated due to the addition of a diode bridge circuit and the like. In addition, since the charging time can be reduced only by half at most as compared with the half-wave rectification, the repetition frequency of the high-voltage pulse cannot be increased twice or more.

In the circuit of FIG. 4C, an auxiliary winding is separately added to the converter transformer, and the converter transformer becomes large. In addition, the rectification method is the same as that shown in FIGS. 5A and 5B, and the same problem as described above occurs.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is possible to shorten the charging time of the capacitor of the starting circuit and increase the repetition frequency of the high voltage pulse for starting. It is an object of the present invention to provide a discharge lamp lighting device that can be used.

It is another object of the present invention to provide a discharge lamp lighting device capable of preventing the discharge lamp from disappearing after the start of lighting.

[0016]

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

(1) A discharge lamp lighting device having a starting transformer for applying a starting high voltage pulse to a discharge lamp, wherein two charging capacitors connected in series and a charging voltage of each capacitor are matched. And a trigger element that conducts when the doubled voltage reaches a predetermined voltage. The two capacitors are alternately and continuously charged by alternate half-cycle outputs of the DC-AC inverter, respectively, so that the two capacitors are charged in one cycle. The two capacitors are charged, and the high-voltage pulse is generated in the secondary winding of the starting transformer by discharging the charge of the capacitor to the primary winding of the starting transformer through the trigger element.

(2) In the configuration of (1) above,
A high voltage pulse for starting is generated after the AC inverter output is inverted once and the capacitor is completely charged, and the inverter output is not inverted until a predetermined time elapses after the discharge lamp starts to light.

(3) In the above configuration (1) or (2), the trigger element is a switching spark gap.

(4) In any one of the constitutions (1) to (3), a DC booster circuit for supplying a DC high voltage to the DC-AC inverter is provided.

[0021]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of the present invention, and shows a configuration of a starting circuit of a discharge lamp 1 including a trigger circuit 7 of FIG. Other configurations are the same as those in FIG.

In FIG. 1, reference numeral 1 denotes a discharge lamp, and 5 denotes a DC-AC inverter to which a high DC voltage is input from a DC-DC converter (not shown) which is a DC boosting circuit. H-bridge transistor inverters are used. 8 is a switching spark gap described above as a trigger element, C1 and C2 are two charging capacitors connected in series, and when the doubled voltage obtained by adding the charging voltages of the respective capacitors C1 and C2 reaches a predetermined voltage. Then, the spark gap 8 conducts, and through this, the charged charges of the capacitors C1 and C2 are discharged to the primary winding of the starting transformer T1, and the starting transformer T
A high-voltage pulse is generated in the secondary winding of No. 1 and the discharge lamp 1 is turned on. R1, R2 and D1, D2 are rectifying resistors and diodes.

In the above circuit, two capacitors C each are output by the output of the inverter 5 in alternate half cycles.
1 and C2 are alternately and continuously charged, and the two capacitors C1 and C2 are charged in one cycle. Also, after the inverter output is inverted once and the capacitors C1 and C2 are completely charged, a high-voltage pulse for starting is generated, and the inverter output is not inverted until a predetermined time elapses after the discharge lamp 1 starts lighting. ing.

That is, the output of the inverter 5 (400 to
(Approximately 500 V), the capacitor C1 is charged for a predetermined time by turning on one side, and then the output of the inverter is inverted to charge the capacitor C2 in the same manner, and the charging voltage is increased to an arbitrary voltage value. At this time, a spark gap 8 having a breakdown voltage of about 400 to 1 kV is used as a trigger element, and capacitors C1 and C2 are used.
When the charging voltage exceeds the breakdown voltage, the space gap 8 is turned on (conducting), and the starting transformer T1 is turned on.
Instantaneously, a large current flows through the primary winding. Then, a high voltage corresponding to the turns ratio with respect to the primary winding is generated in the secondary winding of the starting transformer T1, and the high voltage pulse is applied to the discharge lamp 1, and the discharge lamp 1 starts lighting.

When the discharge lamp 1 is turned on, the output of the inverter 5 drops to the lighting voltage (tube voltage) of the discharge lamp 1, and the capacitors C1 and C1 are turned on until the spark gap 8 is turned on.
2 is not charged. As a result, the trigger voltage can be set higher than that of the trigger circuit using the semiconductor switch, and the voltage applied to the primary winding of the starting transformer T1 also increases. Therefore, the starting transformer T1 can be reduced in size, and the circuit configuration can be simplified.

Also, since the semiconductor method has a junction temperature (about 150 ° C.), it is required to take into account self-heating.
Although it is difficult to use at 0 ° C or higher, spark gap 8
Can operate at about 125 ° C. Therefore, it is possible to use the type in which the discharge lamp socket, the trigger circuit, and the starting transformer are integrated into a discharge lamp of a headlamp of an automobile in a bad environment.

Further, at least three or more connections between the trigger circuit and the converter and the inverter 5 are required. However, this circuit requires only two wires as in the semiconductor system. It is also easy to realize the above type.

As described above, in this circuit, the DC booster circuit (DC-DC converter) is provided with the H-bridge transistor inverter composed of four transformers. A charging voltage equal to or higher than the circuit output voltage can be obtained, whereby a high-voltage pulse can be easily generated in a short time. This is because the oscillation frequency can be easily varied by the above-described transistor inverter, and the present circuit is configured by paying attention to this point.

Operationally, one of the series-connected charging capacitors is continuously turned on until charging is completed during one cycle of the inverter AC output, and then the inverter output is inverted and the other charging capacitor is turned on. By continuously turning on the capacitor for charging until the charging is completed, the connected charging of the capacitor is performed. By this operation, the time until the generation of the high-voltage pulse for starting is minimized, and the charging voltage twice the output voltage of the inverter can be easily obtained as described above.

Further, by using the discharge gap such as the spark gap 8 having a high breakdown voltage by the above-described operation, a predetermined high voltage pulse can be easily generated in the shortest time after the power is turned on.

Further, in this circuit, after the charging of the capacitors C1 and C2 is completed, the inverter output is not inverted until a predetermined time elapses after the lighting of the discharge lamp 1 is started by applying a high-voltage pulse. It is possible to prevent the discharge lamp 1 from going out immediately after startup.

FIGS. 2A and 2B are diagrams showing the waveforms of various parts of the circuit of FIG. 1. FIG. 2A shows the output waveform of the inverter 5, and FIG. 2B shows the charging voltage waveform of the capacitors C1 and C2. As shown, the charging phase of the second capacitor and the DC after lighting
Since the phases are the same, the above-mentioned extinguishing that is likely to occur when the tube current is reversed is less likely to occur in an unstable state immediately after startup.

Here, for the conventional circuit shown in FIG. 4A, the charging time can be shortened as compared with the half-wave rectification method, and as a result, the repetition frequency of the high-voltage pulse can be increased. If the repetition frequency of the high-voltage pulse is low, the time until the next pulse comes when the discharge lamp 1 does not light at the first pulse becomes longer, and flickering at the time of lighting becomes noticeable.

The charging time of the circuit of FIG. 4B is shorter than that of the circuit of FIG. 4B because of the full-wave rectification method, but a diode bridge circuit is required, and the circuit configuration becomes complicated. Therefore, the cost increases and the size increases.

In the circuit shown in FIG. 4C, since the auxiliary winding method is used, a winding is added to the converter transformer, which increases the size of the transformer and increases the cost.
In addition, the number of connection lines from the auxiliary winding to the trigger circuit increases, and the number of relay lines of a lighting device or the like obtained by dividing the starting circuit increases, which causes a cost increase.

In this circuit, the two capacitors C1 and C2 of the starting circuit are continuously charged.
As described above, the time until the start of lighting is shortened, and the charging voltage of the capacitors C1 and C2 is reduced to 2 times the inverter output voltage.
The high-voltage pulse can be easily generated. Further, it is possible to make it hard to cause the disappearance after the start of lighting.

[0037]

As described above, according to the present invention, the charging time of the capacitor of the starting circuit can be shortened, and the repetition frequency of the high voltage pulse for starting can be increased.

Further, it is possible to prevent the discharge lamp from going out after the start of lighting.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing an output waveform of each part of the circuit of the embodiment.

FIG. 3 is a block diagram showing a schematic configuration of a general discharge lamp lighting device.

FIG. 4 is a circuit diagram showing a conventional example.

FIG. 5 is an explanatory diagram showing a relationship between a converter output and a capacitor charging time.

[Explanation of symbols]

 Reference Signs List 1 discharge lamp 2 battery 3 DC-DC converter 4 rectifier circuit 5 DC-AC inverter 6 control circuit 7 trigger circuit 8 switching spark gap (trigger element) C1 capacitor C2 capacitor T1 start-up transformer

Claims (4)

[Claims] 1. A discharge lamp lighting device having a starting transformer for applying a starting high voltage pulse to a discharge lamp, wherein two charging capacitors connected in series and a charging voltage of each capacitor are matched. A trigger element that conducts when the doubled voltage reaches a predetermined voltage, and alternately and continuously charges the two capacitors by alternate half-cycle output of the DC-AC inverter, respectively. Lighting a discharge lamp, charging a capacitor and discharging a charge of the capacitor to a primary winding of a starting transformer through the trigger element to generate a high-voltage pulse in a secondary winding of the starting transformer. apparatus. 2. A high-voltage pulse for starting is generated after the output of the DC-AC inverter is inverted once and the charging of the capacitor is completed, and until a predetermined time elapses after the lighting of the discharge lamp is started.
2. The discharge lamp lighting device according to claim 1, wherein the inverter output is not inverted. 3. The discharge lamp lighting device according to claim 1, wherein the trigger element is a switching spark gap. 4. The discharge lamp lighting device according to claim 1, further comprising a DC booster circuit for supplying a DC high voltage to the DC-AC inverter.