JPS582551B2 - Inverter no Seigiyosouchi - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverme control device used in an induction heating cooker or the like.

Conventionally, in inverters used in induction heating cookers, etc., the oscillation frequency fo of the thyristor gate circuit is kept constant regardless of the power supply voltage vin, so the envelope of the forward voltage and the envelope of the current of the thyristor are Figure 2b,
As shown by the dotted line in c, it was necessary to use a thyristome with a high forward breakdown voltage.

For this reason, the power loss consumed by silinume was large, making it extremely inefficient.

Therefore, it is possible to keep the oscillation frequency fo constant and lower fo, but if the oscillation frequency is lowered, the commutation energy near the zero point of the power supply voltage will be insufficient, the turn-off time of the circuit will be shortened almost always, and the commutation failure of the thyristor will occur. It was the cause of this.

The present invention eliminates the above-mentioned disadvantages of the conventional art with a simple structure, and one embodiment of the present invention will be described below with reference to the accompanying drawings.

In the figure, 1 is a power supply, 2 is a full-wave rectifier circuit, 3 is a current-limiting inductor, 4 is a thyristor, 5 is a diode connected in anti-parallel with the thyristor 4, 6 is a commutating inductor, 7 is a commutating capacitor, and 8 is a commutating capacitor. Load resonance capacitor, 9 load resonance variable inductor, 10 heating coil, 11 thyristor 4
12 is a transformer that detects a voltage proportional to the power supply voltage, 13 is a full-wave rectifier circuit connected to the secondary side of the transformer 12, and 14 is a gate circuit that receives the signal from the full-wave rectifier circuit 13. A transistor for amplification, 15 a Zener diode constituting a constant voltage circuit, 16 a comparison circuit that compares the signal from the transistor 14 with a reference voltage from the Zener diode 15, and 17 a waveform shaping circuit that shapes the signal from the comparison circuit 16. , 18 is a voltage frequency conversion circuit that varies the oscillation frequency of the gate circuit 11.

Next, the operation will be explained.

First, the power supply 1 is lowered to a predetermined voltage by the transformer 12, and the rectifier circuit 13 performs full-wave rectification.

The voltage is amplified by a transistor 14 and compared by a constant voltage circuit including a Zener diode 15 and a comparison circuit 16.

The waveform is smoothly shaped by the waveform rectifier circuit 17, and in response to the voltage, the oscillation frequency fo is set by the voltage frequency conversion circuit 18.
change.

That is, oscillation is performed at a low oscillation frequency near the peak of the power supply voltage, and the oscillation frequency is increased only after the peak and near the zero point of the power supply.

Therefore, the envelope waveforms of the forward voltage V and the forward voltage ■ applied to the thyristor 4 in the gate circuit 11 are the forward voltage of the thyristor 4 at the peak of the power supply 1, and The forward current becomes low and becomes high only at the zero point, similar to the conventional example.

As is clear from the above description, according to the present invention, the oscillation frequency is low near the peak of the power supply voltage, and the oscillation frequency is increased near the zero point of the power supply voltage, so a thyristor with a low forward breakdown voltage can be used. It is possible to configure an inverter with little power loss and sufficient commutation energy near the zero point of the power supply voltage.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an embodiment of the present invention, Fig. 2 a, b
, c, d are the oscillation frequency and the voltage applied to the thyristor.
It is a waveform diagram of a current. 4... Thyristor, 11... Gate circuit, 16... Comparison circuit, 18... Frequency conversion circuit.

Claims (1)

[Claims] 1 Consists of a comparison circuit that compares a reference voltage with a voltage proportional to the full-wave rectified voltage of the AC power supply voltage, and a frequency conversion circuit that varies the oscillation frequency of the gate circuit by the output of this comparison circuit, and is comprised of a frequency conversion circuit that varies the oscillation frequency of the gate circuit by the output of this comparison circuit, Inverme control device that increases the oscillation frequency.