JP2000208284A - Start-up device for discharge lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To supply a large rising current with a small-capacity element in the case that a discharge current from a capacitor is made to flow to a starting high-voltage transformer through a thyristor in a start-up circuit for a discharge lamp. SOLUTION: In this start-up device, a charging circuit 2 charges a capacitor C1, while a discharge current from the capacitor C1 is supplied to a primary winding N1 of a high-voltage transformer T1 through a thyristor Q1 to start-up 5 in a load. A compensation circuit 6 wherein a saturation type choke coil L1 and an unsaturation type choke coil L2 are connected in parallel is connected in series to the thyristor Q1 to delay rapid rising of the current flowing through the thyristor Q1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an HID lamp (High Intensity Discharge).
The present invention relates to a discharge lamp starting device suitable for starting Lamp).

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing the configuration of a conventional discharge lamp starting device of this type. In the figure, 1a,
1b is an input terminal of 400V DC, and 2 is a charging circuit of the capacitor C1, which is composed of a series circuit of resistors R1 and R2 and a diode D1. Reference numeral 3 denotes a discharge circuit of the capacitor C1, which includes a thyristor (SCR) Q1 as a switch element, a trigger circuit 4 for applying a trigger signal to the gate of the thyristor Q1, and a primary winding N1 of the high-voltage transformer T1. The trigger circuit 4 includes a thyristor Q2 as a trigger element and resistors R3 and R4. 5
Is a load bulb (HID lamp) connected to the secondary winding N2 of the high-voltage transformer T1.

In the starting circuit having the above-described configuration, the charging circuit 2
Charges the capacitor C1 through the resistors R1 and R2. The charge stored in the capacitor C1 flows as a discharge current into the primary winding N1 of the high-voltage transformer T1 when the trigger circuit 4 applies a trigger current to the gate of the thyristor Q1 and the thyristor Q1 is turned on. At this time, the primary winding N2 is connected to the secondary winding N2 of the high-voltage transformer T1.
The high voltage generated by the current flowing into 1 is generated,
This high voltage is output to the bulb 5 of the load, and the bulb 5 starts lighting.

[0004]

In the conventional starting device constructed as described above, it is necessary to supply a steep pulse current to the high-voltage transformer. There is a problem that there is an allowable value for the rise of the current flowing through the thyristor, which is a switch element for providing the rise, and a large rise current cannot be obtained.

[0005] Further, in order to obtain a large rising current, an element having a large capacity is required, and there is a problem that the size is large and the cost is high.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and it is an object of the present invention to provide a small and inexpensive starting device for a discharge lamp which can obtain a large rising current with a small-capacity element. The purpose is.

[0007]

A starting apparatus for a discharge lamp according to the present invention is constructed as follows.

(1) A saturable type having a transformer for generating a high voltage for starting a discharge lamp, a switch element for supplying a discharge current of a capacitor to the transformer, and a charging circuit for charging the capacitor. A parallel circuit in which a choke coil and an unsaturated choke coil were connected in parallel was connected in series with the switch element.

(2) In the above configuration (1), the parallel circuit is interposed between the capacitor and the charging circuit.

(3) In the above configuration (1) or (2), the switch circuit is a thyristor.

(4) In any one of the above constitutions (1) to (3), the core material of the saturated choke coil is amorphous, and the core material of the unsaturated choke coil is ferrite.

[0012]

FIG. 1 is a circuit diagram showing the configuration of an embodiment of the present invention. The same reference numerals as in FIG. 3 denote the same components.

The starting circuit of this embodiment is similar to the circuit of FIG.
A charging circuit 2 for charging the capacitor C1 using 400V DC input from the input terminals 1a and 1b, and a capacitor C1 connected to a primary winding N1 of a high-voltage transformer T1 for generating a high voltage for starting a bulb (discharge lamp). A discharge circuit 3 having a thyristor (switch element) Q1 for supplying a discharge current, a trigger circuit 4 for providing a trigger signal to the thyristor Q1, and a saturated choke coil L1 and a non-saturated choke coil L2 are provided. Are connected in parallel to each other by di /
The dt compensation circuit 6 is connected in series with the thyristor Q1 and between the capacitor C1 and the charging circuit 2. Then, when a high-voltage pulse flows through a bulb (HID lamp) 5 connected in series with the secondary winding N2 of the high-voltage transformer T1, the bulb 5 starts lighting.

The charging circuit 2 comprises a series circuit of resistors R1 and R2 and a diode D1, the discharging circuit 3 comprises a trigger circuit 4, a compensating circuit 6 and a primary winding of a high voltage transformer T1, and the trigger circuit 4 comprises a thyristor Q2. And resistors R3 and R
4 and the compensating circuit 6 is composed of the choke coils L1 and L2 and the diode D2.

Amorphous material is suitable for the core of the saturated choke coil L1 of the compensation circuit 6, and ferrite is suitable for the core of the unsaturated choke coil L2. Therefore, in the present embodiment, these core materials are used.

The HID lamp used as the load bulb 5 in the above-described circuit applies a high voltage between the electrodes at the time of startup, shifts the enclosed gas to an excited state, and emits light by the subsequent arc discharge. . A circuit for applying an initial high voltage at that time is called a normal start-up circuit.
An electronic device that maintains the proper operation of the ID valve is called a ballast. And FIG.
Is configured as a start-up circuit that performs an initial high-voltage output in the ballast.

The spark gap method and the thyristor method are mainly used as the high voltage generation method at the time of starting the HID ballast. In either method, it is necessary to supply a pulse current having a steep rise to a transformer for generating a high voltage. is there. In the case of the thyristor system, unlike the spark gap system, the rise of the current flowing through the thyristor, that is, di / dt cannot be an excessive value due to a request from the element side, but is constant after the energization is started. After a lapse of time, it can withstand a considerably large di / dt.

This is because the allowable value of di / dt depends on the effective area of the thyristor chip in which current can flow, and the spread of the effective area is a characteristic of the thyristor known as the gate spreading time. The present embodiment is a circuit taking this point into consideration, and the di / dt compensation circuit 6
Function as a rise delay circuit.

That is, one of the choke coils L1 of the compensating circuit 6 is a saturated type choke coil in which an amorphous core having an excellent squareness ratio is formed in a closed magnetic circuit and is wound on an amorphous core. It has a high inductance value until the core is magnetically saturated. However, if the voltage application time exceeds a predetermined amount (the product of the voltage and the time), the action as a choke coil is lost, and the voltage changes to a mere conductor.

The other choke coil L2 is
Since this is a non-saturated choke coil in which a rod-shaped ferrite core is wound, it has a smaller inductance value than the above-mentioned amorphous choke coil, but has the property of being less likely to be magnetically saturated.

The choke coils L1 and L
As shown in FIG. 2, the value of the current i passing through the compensating circuit 6 connected in parallel has a different tendency at a certain time τ as a boundary. That is, before the time τ, the inductance value of the choke coil L2 is smaller than that of the choke coil L1, so that the value of the current passing through the compensation circuit 6 is governed only by the characteristics of the choke coil L2. However, after time τ, the choke coil L1 is magnetically saturated, and the passing current behaves as a circuit operation in a state where the compensation circuit 6 is short-circuited.

As described above, when the choke coil L1 is magnetically saturated, the operation of the starting circuit according to the present embodiment includes the capacity of the capacitor C1, the inductance of the primary winding N1 of the transformer T1, and the resistance of the thyristor Q1. And transformer T
This is the operation itself of the LCR series resonance circuit with the resistance component including the resistance of one primary circuit.

Due to the presence of the compensation circuit 6, the waveform of the current flowing through the thyristor Q1 is delayed backward in the time zone of sharp rise as compared with the case without the circuit 6, and the thyristor Q1 has a sufficient di / dt withstand capability. When a sufficient allowance is secured, a portion with a sharp rise can be passed.

Therefore, the thyristor Q1 having a small capacity
Thus, a large starting current can be obtained, and a small and inexpensive starting device for an HID lamp suitable for in-vehicle use can be obtained.

Further, by arranging the charging circuit 2 at a stage subsequent to the compensating circuit 6 as in the present embodiment, a circuit current in a direction opposite to that at the time of discharging can flow. Reverse excitation of L1 and L2 is ensured, and the operation of the compensation circuit 6 is assured.

[0026]

As described above, according to the present invention, a large starting current can be obtained with an element having a small capacity, and a small and inexpensive starting device for a discharge lamp can be realized.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a current flowing through a compensation circuit.

FIG. 3 is a circuit diagram showing a conventional example.

[Explanation of symbols]

 2 charging circuit 3 discharge circuit 4 trigger circuit 5 bulb (discharge lamp) 6 compensation circuit (parallel circuit) C1 capacitor L1 choke coil L2 choke coil T1 high-voltage transformer Q1 thyristor (switch element)

Claims (4)

[Claims] 1. A saturation type choke comprising a transformer for generating a high voltage for starting a discharge lamp, a switch element for supplying a discharge current of a capacitor to the transformer, and a charging circuit for charging the capacitor. A starting device for a discharge lamp, wherein a parallel circuit in which a coil and an unsaturated choke coil are connected in parallel is connected in series with the switch element. 2. The discharge lamp starting device according to claim 1, wherein the parallel circuit is interposed between the capacitor and the charging circuit. 3. The starting device for a discharge lamp according to claim 1, wherein the switch circuit is a thyristor. 4. The starting device for a discharge lamp according to claim 1, wherein the core material of the saturated choke coil is amorphous, and the core material of the unsaturated choke coil is ferrite.