JP2001143885A - Igniter circuit for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an igniter circuit for a discharge lamp that supplies an ignition pulse with a voltage enough to ignite the lamp without increasing the size, which is required for enhancing the withstand voltage performance of the circuit, and power consumption. SOLUTION: A capacitor C charged with the voltage of a voltage source 3 has both terminals connected to a serial connection circuit 11 consisting of a constant voltage switching elements S, unsaturated reactor LS, and the primary coil of a pulse transformer 5. The capacitor C being charged, the constant voltage switching element S is turned on to discharge through the unsaturated reactor LS, preliminarily exciting the discharge lamp by the first high voltage pulse. The reactor LS is saturated after a few μ seconds, the discharged current is rapidly increased generating the second high voltage pulse in addition to the first high voltage pulse, so that all the lamps preliminarily excited are lighted by the second high voltage pulse relatively low.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a lighting start circuit (hereinafter, referred to as an igniter circuit) for a discharge lamp used for a headlight of an automobile or the like.

[0002]

2. Description of the Related Art Discharge lamps such as metal halide lamps have been used for headlights of automobiles and the like. In order to start lighting the discharge lamp, with high voltage applied,
It is necessary to apply a particularly high (14 kV or more) pulse voltage to break the insulation between the electrodes of the discharge lamp.

FIG. 7 shows a general block configuration of a lighting circuit of a discharge lamp. In the drawing, 1 is a discharge lamp, 2 is an igniter circuit for generating a high voltage pulse of several tens of kV when the discharge lamp 1 is started, and 4 is an igniter circuit for maintaining a lighting state of the discharge lamp 1.
A booster circuit that applies a high voltage of 0 V, 3 is an inverter circuit that converts the output voltage of the booster circuit 4 into AC, and 50 is a battery. FIG. 8 shows a detailed configuration of the igniter circuit 2 shown in FIG. 7, for example, an igniter circuit similar to that disclosed in Japanese Patent Application Laid-Open No. 7-94289.

In FIG. 8, a series circuit of a resistor R and a capacitor C is connected between input terminals a and b of the igniter circuit 2. Reference numeral 5 denotes a pulse transformer (also referred to as PT in this specification), which has a primary winding of about several turns and a secondary winding of several hundred turns (the primary winding is an intermediate tap of the secondary winding). The secondary winding is connected in series with the discharge lamp 1 and is connected between the terminals a and b. A constant voltage switching element S and a primary winding of PT5 are connected in series, and are connected in parallel to a capacitor C. The constant voltage switching element S is an element that is non-conductive until a predetermined voltage is applied, and is conductive when a predetermined voltage or more is applied.

The operation of the igniter circuit 2 shown in FIG.
The generated high voltage pulse waveform will be described with reference to FIG. As shown in FIG. 9A, a pulse voltage whose polarity is inverted from plus V1 to minus V1 is supplied between the terminals a and b of the igniter circuit 2 from the inverter circuit 3.

When a voltage is applied from the inverter circuit 3 between the terminals a and b, the voltage across the capacitor C becomes
As shown in (b), the voltage varies with the time constant RC (the impedance seen from the primary winding side of the pulse transformer 5 is extremely small, so that the time constant has little effect). Since it also applies to both ends of S,
Eventually, when the capacitor is sufficiently charged, the voltage reaches the breakover voltage of the constant voltage switching element S, and the constant voltage switching element S turns on.

At this time, the voltage across the capacitor C becomes PT
5 (VpT in FIG. 9 (c)) and PT
The stepped-up high voltage pulse is generated in the secondary winding 5, and the high voltage pulse is applied to the discharge lamp 1. P
Since the impedance of the primary winding of T5 is low, the charge of the capacitor C is rapidly lost, and the constant voltage switching element S
The current flowing through the battery also suddenly decreases, and eventually turns off, and charging is started again. Even if the discharge time constant is too large to be turned off, the constant voltage switch element S is turned off at least when the polarity of the pulse voltage of the power supply is inverted, and charging of the opposite polarity is started.

FIG. 10 shows details of the waveform of the high voltage pulse shown in FIG. 9C. Reference numeral 95 in FIG. 10 indicates a high-voltage pulse waveform. The initial low constant voltage is about 400 V, and is a pulse waveform output from the inverter circuit 3. For reliable lighting, the pulse waveform portion 95 must have a pulse time width of 1 ms or more and a peak voltage value of 15 kV or more. In order to obtain such a pulse width and a peak value, it is necessary to increase the withstand voltage performance of the circuit and wiring, and the size of the device is increased due to consideration of insulation and the like. Since the circuit time constant determined by the impedance seen from the primary winding (the winding to which the constant voltage switching element S is connected) needs to be adjusted to the above-mentioned pulse time width, the capacitance of the capacitor C needs to be considerably increased. However, there is a problem that power consumption is increased.

[0009]

As described above, the conventional igniter circuit of a discharge lamp needs to generate a long pulse width (time) and an extremely high peak voltage. There is a problem that the size is increased and power consumption is increased.

The present invention solves the above problems and provides an igniter circuit capable of starting a discharge lamp with a shorter pulse width (time) and a lower peak voltage, and provides an igniter circuit and a discharge lamp. It is an object of the present invention to reduce the power consumption while reducing the size of the insulation resistance of the circuit.

[0011]

An igniter circuit for a discharge lamp according to the present invention has a peak value of 5 to 8 kV and a time width of 1 kV.
A first high-voltage pulse for pre-exciting a discharge lamp of about 2 .mu.S, a peak value of 2 to 5 kV superimposed on the first pulse within the time width of the first high-voltage pulse, and a time width of 0.2 to 0.2 .mu.S. 1
The second high-voltage pulse for lighting the μS discharge lamp is output.

An igniter circuit for applying a high-voltage pulse to a discharge lamp via a pulse transformer connected in series to a discharge lamp connected to a pulse power supply, comprising: a capacitor for storing a voltage of the pulse power supply; It has a switch connected between both terminals, a series connection circuit of a saturable reactor and a primary coil of a pulse transformer, and transfers the electric charge charged in the capacitor via the saturable reactor in a non-saturated state by conduction of the switch. A first high-voltage pulse generated by discharging and a second high-voltage pulse superimposed on the first high-voltage pulse and generated by saturation of the saturable reactor due to a discharge current are output. It is.

Further, the capacitor for storing the voltage of the pulse power supply is connected to the pulse power supply via an impedance element, and the switch is constituted by a constant voltage switching element which conducts at a predetermined voltage.

The peak value of the first high-voltage pulse at the time of occurrence of the second high-voltage pulse is 5 to 8 kV,
The peak value of the high voltage pulse is 2 to 5 kV, the pulse width of the first high voltage pulse is 1 to 2 μS, and the pulse width of the second high voltage pulse is 0.2 to 1.0 μS.

The voltage value of the first high-voltage pulse at the time of generation of the second high-voltage pulse is 5 to 8 kV, and the sum of the first high-voltage pulse and the second high-voltage pulse is 8 to 10 kV.
V, the time width during which the voltage value of the first high-voltage pulse exceeds 5 kV before the generation of the second high-voltage pulse is 1-2 μS,
The pulse width of the second high-voltage pulse is 0.2 to 1.0 μS.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 shows an igniter circuit of a discharge lamp according to the present invention. In the following drawings, the same or corresponding parts as those in the related art are denoted by the same reference numerals, and detailed description thereof will be omitted. In the figure, a capacitor C is connected between input terminals a and b of the igniter circuit via a resistor R (referred to as an impedance element).
The capacitor C stores the voltage of the inverter circuit 3. 5
Is a pulse transformer (also referred to as PT in the present specification), and has a primary winding of about several turns and a secondary winding of several hundred turns (the primary winding may have a middle tap between the secondary windings). is there)
And the secondary winding is connected in series with the discharge lamp 1 and is connected between the terminals a and b. A constant voltage switching element S (referred to as a switch) and saturable reactors LS and P are connected in parallel with the capacitor C from a connection point between the resistor R and the capacitor C.
The series connection circuit 11 with the primary winding of T5 is connected. The constant voltage switching element S is an element that is non-conductive until a predetermined voltage is applied, and is conductive when a predetermined voltage or more is applied.

The saturable reactor LS initially has a predetermined inductance, but saturates when a current of a predetermined amp-hour product flows, and the inductance of the saturable reactor LS decreases rapidly. FIG. 2 shows a pulse voltage waveform (corresponding to Vpt in (c) of FIG. 9) generated on the secondary side of the pulse transformer 5 by the igniter circuit of FIG.
In the figure, reference numeral 95 denotes the conventional high-voltage pulse waveform 95 of FIG. t0 indicates the timing when the constant voltage switching element S is turned on, and t1 indicates the time when the saturable reactor Ls is saturated. Reference numeral 98 denotes a first signal output during a period from time t0 to time t1.
A high-voltage pulse waveform 99 indicates a second high-voltage pulse waveform after time t1. V1 is a constant voltage switching element S
Is turned on, the saturable reactor LS is saturated, that is, the maximum peak value of the pulse voltage output to the secondary side of the PT5 of the first high-voltage pulse waveform 98, and V2 is the saturable reactor LS The second high-voltage pulse waveform 9 output to the secondary side of PT5 after saturation, that is, after time t1
9 shows a value to be added above the maximum peak value V1 of 9.

T1 indicates the time length of the first high-voltage pulse waveform 98 between t0 and t1, and T2 indicates the time width of the second high-voltage pulse waveform 99. By adjusting the circuit constants in FIG. 1, V1 is 5-8 kV, V2 is 2-5 kV, T1 is 1-2 μS, and T2 is 0.2-1 μS. Since it is pre-excited by the voltage V1, even if the value of V1 + V2 is lower than the conventional peak voltage of 14 kV and the pulse width T2 of the waveform 99 is shorter than the conventional 1 mS, an electrode (not shown) inside the discharge lamp 1 is provided. The insulation between them is easily broken, and discharge lighting starts.

The operation of the igniter circuit shown in FIG. 1 will be described. When a pulse voltage of about 350 to 400 V is applied between the terminals a and b from the inverter circuit 3, charges are accumulated in the capacitor C by the RC charging circuit, and the voltage across the capacitor C gradually increases. Eventually, when the breakdown voltage of the constant voltage switching element S is reached (this time corresponds to t0 in FIG. 2), the electric charge of the capacitor C becomes C−
It is discharged by the S-Ls-PT series connection circuit 11.

At the time point t0 when the discharge starts, the saturable reactor LS is not saturated, so its inductance is large, the rising waveform 98 of the pulse voltage between t0 and t1 is relatively gentle, and the pulse transformer 5 also has a low voltage on the primary coil. At time t1, the saturable reactor LS saturates and its inductance suddenly approaches zero, so that the entire voltage of the capacitor C (which has been slightly discharged and reduced by time t1) is reduced by the pulse transformer. In addition to the primary coil No. 5, the waveform 99 is output and the charge of the capacitor C is rapidly lost. At time t1, the second high-voltage pulse waveform 99 having a very short duration is generated so as to be superimposed on the gentle first high-voltage pulse waveform 98.

When the electric charge of the capacitor C is almost completely discharged, the constant voltage switching element S is turned off. The capacitance of the capacitor C and the inductance value of the saturable reactor LS are such that the time length T1 is 1-2 μS and the time length T2 is 0.2-1 μS.
And the voltage V1 of the first high-voltage pulse waveform 98 at time T1 is selected to be 5 to 8 kV, and the height V2 of the second high-voltage pulse waveform 99 is selected to be 2 to 5 kV. . In order to obtain such a voltage and a waveform, the capacity of the capacitor C is generally required to be about 1/2 of that of the related art. Thereby, the electric power required to start the discharge of the discharge tube 1 can be reduced to about half.

The change range of the voltage having the waveform shown in FIG. 2 will be described in more detail with reference to FIG. The horizontal axis in FIG. 3 indicates the voltage (kV) of V1, and the vertical axis indicates the voltage (kV) of V2.
As described above, the value of V1 is 5 to 8 kV, and the value of V2 is 2 to 5 kV.
Since it is V, a square range 97 surrounded by a dotted line corresponds to this. It should be noted that a voltage higher than the above range does not mean that the discharge lamp 1 does not start, but does not mean that it does not meet the purpose of the present invention of lowering the withstand voltage performance required by the device, and does not mean that no reward is given. It is.

Embodiment 2 FIG. The range of the voltage peak value of the pulse waveform described in the first embodiment indicates each peak value and each pulse width of the first and second high-voltage pulse waveforms. However, to express more strictly as a condition for pre-excitation by the first high-voltage pulse, the time during which the voltage of the first high-voltage pulse exceeds 5 kV may be 1-2 μS. In addition, in order to cause a dielectric breakdown between the electrodes inside the discharge lamp by the second high-voltage pulse and start the discharge, a voltage in which the first high-voltage pulse and the second high-voltage pulse are superimposed is required. 8-10k
It is sufficient that the time of V is 0.2 to 1.0 μS. Such a voltage range is shown in FIG. V1 + V2 is 8 to 10
The range of kV is the range of 96 hatched.

Embodiment 3 FIG. Since the series connection circuit 11 of the circuit of FIG. 1 according to the first embodiment is a series connection of the constant voltage switching element S, the saturable reactor LS, and the primary winding of the pulse transformer 5, the connection order is as follows. May be changed. For example, FIG. 4 shows an igniter circuit according to the third embodiment of the present invention.
Are switched in the opposite direction. Even if such an arrangement is changed, there is no change in the form in which the series connection circuit 11 is connected between both terminals of the capacitor C, and the operation principle is exactly the same.

Embodiment 4 One end of the capacitor C need not necessarily be directly connected to the power supply line. For example, the circuit of FIG. 5 shows an igniter circuit according to the fourth embodiment of the present invention, in which the positions of the capacitor C and the constant voltage switching element S in the circuit of FIG. The current flowing through the saturable reactor LS includes a current for charging the capacitor C and a current for discharging. Therefore, the supersaturated reactor LS is easily reset, and has a feature that the operation is stabilized.

FIG. 6 shows the circuit of FIG. 5 in which the position of the saturable reactor LS is changed to a position in series with the constant voltage switching element S, but the operation is the same as that of FIG.

In the above description of the first to fourth embodiments,
Although the switch S has been described as a constant voltage switching element, any other element may be used as long as the element performs a switching operation in principle. For example, a trigger circuit that outputs a trigger signal when the absolute value of the voltage at both ends exceeds a predetermined value, and a transistor or a thyristor element that can be turned on / off by this signal can be used in combination. The pulse transformer 5 is primary-2
Although illustrated as having a next coil, a single-turn pulse transformer may be used. The resistance R can be an inductance.

[0028]

The igniter circuit according to the present invention has the following features.
A second high voltage pulse of 2 to 5 kV with a time width of 0.2 to 1 μS is superimposed on a first high voltage pulse of 5 to 8 kV with a time length of 2 μS, and the second high voltage pulse is output by the first high voltage pulse. Since the discharge is started by the second high-voltage pulse after the discharge lamp is pre-excited, the discharge is started even if the combined voltage value of the first high-voltage pulse and the second high-voltage pulse is lower than the conventional voltage. The required withstand voltage performance of the discharge lamp device can be reduced.

Since the switch, the saturable reactor, and the primary coil of the pulse transformer are connected in series between the two terminals of the capacitor charged by the pulse power source, the first saturable reactor is generated in an unsaturated state. In the middle of the waveform of the high-voltage pulse, the saturable reactor is saturated and the second high-voltage pulse is superimposed and generated. Therefore, the second high-voltage pulse superimposed on the first high-voltage pulse is formed with a very simple circuit configuration. A voltage pulse can be generated.

The capacitor for accumulating the voltage of the pulse power supply is connected to the pulse power supply via an impedance element, and the switch is constituted by a constant voltage switching element which conducts at a predetermined voltage. The effect of extremely simple configuration is obtained

The time from the rise of the first high-voltage pulse to the generation of the second high-voltage pulse is 1 to 2 μm.
S, since the time width of the second high-voltage pulse can be 0.2 to 1 μS, the power consumption of the discharge lamp starting pulse is
The effect of requiring less than in the past can be obtained.

Since the sum of the first high-voltage pulse and the second high-voltage pulse is 10 kV or less, a discharge lamp device having a low withstand voltage characteristic can be used.

[Brief description of the drawings]

FIG. 1 is an igniter circuit diagram of a discharge lamp according to the present invention.

FIG. 2 is a detailed explanatory diagram of a pulse generated by the circuit of FIG. 1;

FIG. 3 is an explanatory diagram showing an operating voltage range of the circuit of FIG. 1;

FIG. 4 is an igniter circuit diagram of a discharge lamp according to a third embodiment.

FIG. 5 is an igniter circuit diagram of a discharge lamp according to a fourth embodiment.

6 is a modified circuit diagram of the igniter circuit of FIG.

FIG. 7 is a circuit configuration diagram of a conventional discharge lamp lighting device.

FIG. 8 is a circuit diagram of the igniter of the configuration diagram of FIG. 7;

FIG. 9 is a waveform chart for explaining the operation of the igniter circuit shown in FIG. 8;

FIG. 10 is a detailed explanatory diagram of the waveform in FIG. 9;

[Explanation of symbols]

1 discharge lamp, 2 igniter circuit, 3 inverter circuit, 4 booster circuit, 5 pulse transformer, 11
Series connection circuit, 50 batteries, 95 conventional high voltage pulse waveform, 98 first high voltage pulse waveform, 9
9 Second high voltage pulse waveform, R resistance, C capacitor, S constant voltage switching element.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Yoshio Saito, Inventor 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsui Electric Co., Ltd. (72) Inventor Akihiko Iwata 2-3-2 Marunouchi, Chiyoda-ku, Tokyo F term in Ryo Denki Co., Ltd. (reference) 3K039 AA03 MC04 MC07 MC10 3K083 AA06 AA09 AA67 BA05 BB06 BC34 BC42 BC47 BE13 CA33

Claims (5)

[Claims] 1. An igniter circuit for a discharge lamp for applying a high-voltage pulse to a discharge lamp to start the discharge lamp, wherein a peak value for pre-excitation of the discharge lamp is 5 to 8 kV and a time width is 1 to 1.
A first high-voltage pulse of 2 μS and a peak value for superimposing the first pulse within the time width of the first high-voltage pulse to turn on the discharge lamp and a time width of 0.2 to 5 kV;
An igniter circuit for a discharge lamp, which outputs a second high-voltage pulse of about 1 μS. 2. An igniter circuit for applying a high-voltage pulse to the discharge lamp via a pulse transformer connected in series to a discharge lamp connected to a pulse power supply, wherein the capacitor stores a voltage of the pulse power supply; A switch connected between both terminals of the capacitor, a series connection circuit of a saturable reactor and a primary coil of the pulse transformer, wherein the electric charge charged in the capacitor is turned into an unsaturated state by conduction of the switch. A first high-voltage pulse generated by discharging through the saturable reactor;
An igniter circuit for a discharge lamp, wherein a second high-voltage pulse generated by saturating the saturable reactor by the discharge current is output superimposed on the first high-voltage pulse. 3. A capacitor for storing a voltage of a pulse power supply, comprising a capacitor connected to the pulse power supply via an impedance element, and a switch comprising a constant voltage switching element which conducts at a predetermined voltage. The igniter circuit for a discharge lamp according to claim 2, wherein 4. The voltage value of the first high-voltage pulse at the time of occurrence of the second high-voltage pulse is 5 to 8 kV, the voltage peak value of the second high-voltage pulse is 2 to 5 kV, and the first high voltage 4. The igniter circuit for a discharge lamp according to claim 2, wherein the pulse width of the pulse is 1 to 2 [mu] S, and the pulse width of the second high voltage pulse is 0.2 to 1.0 [mu] S. 5. The voltage value of the first high-voltage pulse at the point of time when the second high-voltage pulse is generated is 5 to 8 kV, and the first high-voltage pulse has a waveform in which the second high-voltage pulse is superimposed on the first high-voltage pulse. The peak value is 8 to 10 kV, the time width during which the voltage value of the first high voltage pulse exceeds 5 kV before the generation of the second high voltage pulse is 1-2 μS, and the pulse width of the second high voltage pulse is 0 4. The igniter circuit for a discharge lamp according to claim 2, wherein the igniter circuit is set to 0.2 to 1.0 [mu] S.