JPS6155342B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a self-excited inverter device, and particularly to an inverter device that facilitates control of load power.

Conventionally, in power control of an LC resonant thyristor inverter device, (1) Q is changed by changing the ratio of the thyristor trigger frequency to the LC resonant frequency. (2) Change the power supply voltage of the inverter device. (3)
Change the oscillation and stop times of the inverter device. Such methods were used.

However, in (1), the variable range of power is narrow. (2) requires a power supply circuit to change the power supply voltage separately from the inverter device, which makes the circuit complicated, and because it is a variable voltage type power control, a constant peak voltage is required for arc welding machines, etc. It is not suitable as a power source for (3) is that the inverter device requires a trigger circuit, oscillation, and stop time control circuit and is complex, and if the frequency of operation and stop is low, the operation is intermittent, so the AC power supply voltage There are problems such as fluctuations in the fluorescent light causing flickering.

An object of the present invention is to provide an inverter device that solves these problems in conventional power control.

Next, the present invention will be explained in detail with reference to the drawings. FIG. 1 shows a phase control inverter device according to the present invention. In FIG. 1, 1 is an AC power source, 2 is a rectifier circuit block, 3 is a self-excited inverter block, and 4 is a synchronous trigger circuit block. 5 to 8 in circuit block 2 are rectifier diodes, 9 in inverter block 3 is a filter capacitor for lowering impedance at high frequencies, 1
0 to 13 are feedback diodes, 14 to 17 are thyristors, 18 and 19 are resonant inductances and capacitors, respectively, 20, 21, and 22 and 23 are differential resistors and capacitors, respectively, 24 and 25 are pulse transformers, and 26 to 33 are pulse Among the output terminals of the transformer, 26' to 33' are connection terminals of the corresponding thyristors 14 to 17, and 34 and 35 are rectifier diodes. Furthermore, 36 and 37 in the trigger circuit block 4 are rectifier diodes for giving a full-wave rectified waveform to the trigger circuit, 38 is a resistor, 39 is a constant voltage diode for making the full-wave rectified waveform into a trapezoidal wave, and 40 , 41 are variable resistors and capacitors, 42 and 4 are respectively used to change the oscillation start phase.
3 and 44 are resistors, 45 is a PUT, and 46 is a diode for preventing unnecessary trigger pulses from being generated during operation of the inverter circuit.

Next, block 3 of the self-excited inverter will be explained. When a trigger pulse is applied to the terminal 30 of the pulse transformer 25 by the trigger circuit block 4, the thyristors 14 and 17 are brought into conduction. Due to the conduction between the thyristors 14 and 17, a differential pulse is further applied to the pulse transformer 25 through the differential resistor and the capacitors 20 to 23, and the secondary terminals 30 to 33 of the pulse transformer 25 are connected to the thyristors 14 and 17.
A pulse trigger voltage is generated to further trigger the signal. The operation of the thyristors 14 and 17 after the trigger is such that after the positive cycle of the resonant current of the resonant inductance 18 and the capacitor 19 flows through the thyristors 14 and 17, the negative cycle flows through the feedback diode 10,
13, and the electric charge that was charged in the differential capacitor 22 at the moment when this negative current stops flowing and the current becomes zero is transferred to the circuit consisting of the primary winding resonant inductance 18 of the pulse transformer 24, the capacitor 19, and the differential resistor 20. A trigger pulse is generated at the secondary terminals 26 to 29 of the flow pulse transformer 24, and the thyristors 15 and 16 are triggered. Similarly, at the moment when the currents in the feedback diodes 11 and 12 stop flowing, a trigger pulse is generated in the secondary windings 30 to 33 of the pulse transformer 25, and the thyristors 14 and 17 are triggered again. In this way, the inverter circuit continues its self-excited operation.

This self-excited operation is performed by the pulse transformer 2.
The trigger pulses of the secondary windings 4 and 25 continue as long as the voltage necessary to trigger the thyristors 14 to 17 is supplied, but if the power supply voltage drops to a certain voltage, the thyristors 14 to 17 cannot be triggered and operate. stops.

Here, the rectifier circuit block 2 serving as a power source for the self-excited inverter circuit will be explained. When the voltage of the rectifier circuit block 2 has a small capacity of the filter capacitor 9, ripple current becomes large. If the voltage at the trough of the pulsating voltage is low enough to stop the operation of the self-excited inverter, the operation will stop at the trough of the pulsating voltage. Therefore, if a trigger pulse is applied from the synchronous trigger circuit 4 in synchronization with the pulsating voltage at the peak of the pulsating voltage, the self-excited inverter circuit will operate at the peak and stop at the trough. It can operate and stop within the voltage period. By changing the phase angle of the trigger pulse with respect to the pulsating voltage, it is possible to arbitrarily change the operating and stopping time ratio of the self-excited inverter, that is, the output power.

Next, the operation of the synchronous trigger circuit block 4 for varying the phase angle of the trigger pulse with respect to the pulsating voltage will be explained with reference to the waveform diagram of FIG. A full-wave rectified waveform 51 shown in FIG. 2a is obtained at the cathodes of the diodes 36 and 37, and a trapezoidal waveform 52 shown in FIG. 2b is obtained between the terminals of the constant voltage diode 39. The PUT 45 is turned off at the trough of the trapezoidal wave 52, and the voltage of the capacitor 41 connected to the anode of the PUT 45 for each cycle starting from the trough is changed between the variable resistor 40 and the capacitor 41.
When the gate voltage of the PUT 45, which is charged as 54 in FIG. 2c and biased by the resistor 43 and shown as 53 in FIG. 2b, is reached with a time constant of Trigger pulses such as 55 in FIG. 2d are generated at both ends. The phase angle α at the time of generation of the trigger pulse 55 is adjusted by changing the charging speed of the capacitor 41 by changing the resistance value of the variable resistor 40.

FIG. 2e shows the power supply voltage waveform of the inverter circuit 4. Due to this voltage 56, oscillation is started by the trigger pulse 55 at the phase point α, and the oscillation is stopped near the valley of the power supply voltage 56. As a result, a high frequency voltage having an envelope of voltage 56 as shown in FIG. 2f is obtained across the resonant coil 18 or the resonant capacitor 19.

As described above, the self-excited inverter device of the present invention has
The trigger circuit is simple, and the operation and stop are synchronized with the power supply frequency, so there is little disturbance in the AC power supply voltage, and there is no flickering effect on fluorescent lights, TVs, etc. In addition, if the phase angle at the start of oscillation is operated between 0° and 90°, the peak value of the output voltage of the self-excited inverter device will always be constant, and the welding current can be varied, especially in arc welding machines. However, it has advantages such as good arc stability.

The output of this inverter device can be obtained by using the resonant inductance 18 as a working coil and performing induction heating, or by providing a secondary winding around the resonant inductance 18 to take the load, or by taking the load from both terminals. There is a method of taking the load from both terminals of the capacitor 19 via a transformer, or a method of taking the load between the anodes of the thyristors 15 and 17 via a transformer.

Furthermore, although a thyristor is used as the switching element in the above description, the same operation can be performed not only in a thyristor but also in a self-excited transistor inverter.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a phase control inverter device according to the present invention, and FIG. 2 is a waveform diagram for explaining the operation of the circuit shown in FIG. 1... AC power supply, 2... Rectifier circuit block, 3
... Inverter circuit block, 4 ... Trigger circuit block, 14, 15, 16, 17 ... Thyristor, 18 ... Resonance coil, 19 ... Resonance capacitor.

Claims (1)

[Claims] 1. A DC power source that outputs a DC voltage with pulsating current obtained by rectifying an AC power source, and using the DC power source as a power source,
A self-excited inverter circuit that stops self-excited oscillation at the trough of the pulsating voltage of the DC power source, and a power source synchronizer that generates a trigger pulse synchronized with the AC power cycle to trigger the self-excited inverter circuit. A phase control inverter device consisting of a trigger circuit.