JP3188530B2 - Inverter device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for converting the output of a chopper circuit into a high-frequency AC voltage and supplying it to a load. This type of inverter device is used for a discharge lamp lighting device and the like.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a conventional inverter device used for a discharge lamp lighting device. Hereinafter, the configuration and operation of the inverter device will be described. In FIG. 4, an AC power supply AC is rectified by a rectifier circuit 1, and this rectified output is boosted by a booster type chopper circuit 2 to obtain a predetermined DC voltage.
Chopper circuit 2 is composed of high-frequency switch Q1, inductor L1,
Diode D1 Consists of capacitor C1 and control IC8.Control IC8 turns high-frequency switch Q1 on and off at high frequency, chops the rectified output,
The energy stored in the choke coil L1 when Q1 is on is released through the diode D1 when the high-frequency switch Q1 is off, and the chopping voltage output via the diode D1 is smoothed by the capacitor C1. .

In this inverter device, an inverter circuit
3.As an automatic half-bridge circuit, the main switching elements Q2 and Q3 composed of transistors are connected in series to the output of the chopper circuit 2.The main switching elements Q2 and Q3 are connected in anti-parallel to the main switching elements Q2 and Q3. Have been. The output of the inverter circuit 3 has an LC resonance circuit including an inductor L2, a smoothing capacitor C2, and a discharge lamp L, which is a load connected in parallel to the smoothing capacitor C2, via a current transformer CT that drives the main switching elements Q2 and Q3. Are connected, and this resonance circuit is connected to the inverter circuit 3
To excite the discharge lamp L. Note that the capacitor C3
Is a DC component cutting capacitor. Startup circuit 5
Is a thyristor Q4, a transistor Q5, as shown in FIG.
Zener diodes ZD2, ZD3, diodes D6, D7, resistors
It is composed of R3, R4 and a capacitor C6. This is because, after the power switch is turned on, the output rectified by the rectifier circuit 1 is charged into the capacitor C6 via the resistor R3, and the potential is applied to the Zener voltage of the Zener diode ZD2 (about 20).
When V exceeds V), the thyristor Q4 is turned on, the transistor Q5 is turned on via the zener diode ZD3 and the resistor R4, and a base current is supplied to the main switching element Q3.

When the main switching element Q3 is turned on, the capacitor C6 is discharged via the diode D6, so that the thyristor Q4 and the transistor Q5 are turned off. When the main switching element Q3 is turned on by the starting circuit 5, a current flows to the primary side of the current transformer CT via the resonance circuit. A voltage whose polarity changes according to the direction of the resonance current is induced on the secondary side of the current transformer CT, and the induced voltage causes the main switching elements Q2 and Q3 to be alternately turned on and off to oscillate the inverter circuit 3. .

The main switching element Q3 is:
Although the bias is supplied from the secondary side of the current transformer CT, it can be set to a predetermined output by forcibly turning it off by the control circuit 6 shown in FIG. The control circuit 6 includes transistors Q6, Q7, Q8, Q9 and diodes D8, D8.
9, capacitors C7, C8, resistors R6, R7, R8, R9, R10, R11, a variable resistor VR1, and a comparator C.

When a resonance current flows in a direction in which the secondary winding of the current transformer CT applies a bias to the switching element Q3, the transistor Q9 is also biased, the transistor Q9 is turned on, the transistor Q8 is turned off, and the resistance of the chopper output is reduced. Start charging capacitor C7 via R8. When the potential of the capacitor C7 exceeds the reference voltage VREF, the output of the comparator C changes from a low voltage to a high voltage. The reference voltage VREF is set so as to be low during preheating and high during lighting.

When the output of the comparator C becomes a high voltage,
A bias is applied to the transistor Q6 from the control power supply voltage VCC via the resistor R7, and the transistor Q6 is turned on and the transistor Q7 is also turned on. This forcibly determines the ON period of the main switching element Q3. Also, the control circuit
6 is connected to the capacitors C4 and C5 shown in FIG.
, Diodes D4 and D5, and a Zener diode ZD1 control power supply voltage VCC as shown in FIG.
4, C5, diodes D4, D5, and a zener diode ZD1 to supply power from a control power supply circuit 4. Capacitor C4 and diodes D4, D at the middle point of main switching elements Q2, Q3
By inserting 5, the capacitor C4 charges and discharges in synchronization with the resonance current, and supplies power to the Zener diode ZD1 and the capacitor C5 via the diode D4.

[0008]

However, in the control power supply circuit 4 in the conventional inverter device, charging and discharging are performed in synchronization with the resonance current. Therefore, when the chopper circuit 2 is not started (during preheating), the circuit is not operated. The voltage is low and the level supplied to the control circuit 6 is also low (FIG. 7a). Therefore chopper circuit
2 There was a risk of running out of control power during non-startup. Also, if the chopper is not activated, the control circuit 6
If the capacity of the capacitor C4 is set to the level to be supplied to the power supply, the supply becomes excessive after the chopper is started, and the zener diode ZD1, which constitutes a part of the control power supply circuit 4, may be overloaded.

The present invention has been made in view of these points, and an object thereof is to provide a conventional control power supply circuit.
In addition to the above, a control power supply circuit is provided in which the supply level is high when the chopper circuit 2 is activated, and the control level is low when the chopper circuit 2 is activated. It is intended to be

[0010]

The technical means of the present invention for solving this technical problem converts a DC power supply obtained by rectifying and smoothing an AC power supply AC into a predetermined voltage value by turning on and off a high-frequency switch Q1. A chopper circuit 2; an inverter circuit 3 for turning on and off a pair of switching elements Q2 and Q3 connected in series with the output of the chopper circuit 2 to convert the output of the chopper circuit 2 to a high frequency; A load L connected in parallel to the resonance capacitor C2 via the inductor L2 from the middle point, and an oscillating current flowing through the load L is fed back to at least one of the control terminals of the switching elements Q2 and Q3 so that the switching elements Q2 and Q3 are connected. And a control circuit for performing on / off control, wherein the control power supply voltage of the control circuit 6 is supplied from a middle point of the switching elements Q2 and Q3. A power supply circuit 4,
A second control power supply circuit 7 for supplying a control power supply voltage from the resonance capacitor C2 is provided.

[0011]

In the first control power supply circuit, when the chopper circuit is not activated, the supply level of the control power supply voltage to the control circuit is low, and after the chopper circuit is activated, the supply level increases. In 7, the supply level is high when the chopper circuit 2 is not activated, and the supply level is reduced after activation. Therefore, a stable control power supply voltage is obtained by combining the control power supply circuits 4 and 7.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiment. In FIG. 1, a control power supply voltage VCC of a control circuit 6 is supplied from a middle point of switching elements Q2 and Q3, in addition to a first control power supply circuit 4. And a second control power supply circuit 7 for supplying the control power supply voltage VCC of the control circuit 6 from the resonance capacitor C2. The first control power supply circuit 4 includes capacitors C4 and C5 and a diode, similarly to the control power supply circuit 4 of FIG.
D4, D5, and a zener diode ZD1. The second control power supply circuit 7 includes a capacitor C9 that charges and discharges in synchronization with the current of the resonance capacitor C2 and supplies a current to the control circuit 6, and a diode D1 that forms a discharge loop.
0, D11. The rectifier circuit 1, chopper circuit 2, inverter circuit 4, and other configurations are the same as in the conventional example (FIG. 4 and the like).

Next, the operation will be described. During the period from power-on to activation of the chopper, the inverter circuit 3 operates using a DC voltage of power supply voltage × √2 V as a power supply. At this time,
Although the supply level from the first control power supply circuit 4 composed of the capacitor C4 and the diodes D4 and D5 becomes low, the shortage is compensated for by the second control power supply circuit 7 composed of the capacitor C9 and the diodes D10 and D11. After about 1 to 2 seconds, when the chopper circuit 2 starts up, the supply level from the first control power supply circuit 4 rises, and almost at the same time, the discharge lamp, which is the load,
L shifts to normal lighting. At that moment, the supply level from the first control power supply circuit 7 constituted by the capacitor C9 and the diodes D10 and D11 decreases. By this series of operations, the current waveform flowing to the capacitor C4 becomes as shown in FIG. 2, and the voltage applied to the capacitor C9 and the current waveform flowing to the capacitor D11 become as shown in FIG. In all steps, the control power supply voltage VCC to the control circuit 6 is supplied stably.

In the above embodiment, the load of the inverter device is constituted by one discharge lamp L. However, the load is not limited to this, and the load may be constituted by connecting a plurality of discharge lamps in series. Alternatively, a load other than the discharge lamp may be used.

[0015]

According to the present invention, a stable control power supply voltage can be obtained in the control circuit 6 when the chopper circuit 2 is not started and in each state after the chopper circuit 2 is started. This is effective for circuits with different voltages.

[Brief description of the drawings]

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

FIG. 2 is a waveform diagram for explaining the operation.

FIG. 3 is a waveform chart for explaining the operation.

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

FIG. 5 is a circuit diagram of a conventional starter circuit.

FIG. 6 is a circuit diagram of a conventional control circuit.

FIG. 7 is a waveform chart for explaining the operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rectifier circuit 2 Chopper circuit 3 Inverter circuit 4 1st control power supply circuit 6 Control circuit 7 2nd control power supply circuit Q1 High frequency switch Q2 Switching element Q3 Switching element

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 7/48 H05B 41/24 H05B 41/282

Claims (1)

(57) [Claims] A chopper circuit (2) for converting a DC power supply obtained by rectifying and smoothing an AC power supply (AC) into a predetermined voltage value by turning on and off a high-frequency switch (Q1), and an output of the chopper circuit (2). An inverter circuit (3) that turns on and off a pair of switching elements (Q2) (Q3) connected in series to convert the output of the chopper circuit (2) to a high frequency, and a midpoint of the switching elements (Q2) (Q3) The load (L) connected in parallel to the resonance capacitor (C2) via the inductor (L2) and the oscillating current flowing through this load (L) are fed back to at least one control terminal of the switching elements (Q2) and (Q3). And a control circuit (6) for controlling the switching elements (Q2) and (Q3) to turn on and off, wherein the control power supply voltage of the control circuit (6) is changed by the switching element (Q
2) A first control power supply circuit (4) supplied from the midpoint of (Q3) and a second control power supply circuit (7) supplying a control power supply voltage from the resonance capacitor (C2) are provided. Inverter device.