JPH082180B2 - AC-DC converter - Google Patents

Description

Description: TECHNICAL FIELD OF THE INVENTION The present invention relates to an AC / DC converter for converting an AC input into a DC.

[Technical background]

In recent years, due to the development of semiconductor elements such as gate turn-off thyristors that can turn on / off current at high speed, a high frequency modulation system has come to be used not only in DC / AC converters (inverters) but also in AC / DC converters.

Fig. 1 shows the main circuit configuration of a single-phase AC-DC converter that can control the input AC current waveform by this high-frequency modulation. D1 to D4 are diodes, GT1 to GT4 are gate turn-off thyristors (hereinafter referred to as GTO). It is called) and constitutes the bridge circuit. An AC power supply S is connected to the input side of this bridge circuit via a reactor L, and a load M to which a capacitor C is connected in parallel is connected to the output side.

This circuit turns on and off the GTO at a frequency considerably higher than the power supply frequency to improve the input power factor by making the fundamental wave phase of the input current waveform in phase with the voltage, and at the same time makes the input current waveform close to a sine wave. In this way, harmonic components are removed.

FIG. 2 shows waveforms at various parts during operation of the circuit of FIG. In this waveform diagram, since the ignition signal is applied to GT2 and GT4 in the period T ₁ , the power source S causes the reactor L,
The current flowing through GT2 and D4 increases. Next, in the period T2, the ignition signal is given to GT1 and GT4, but in reality, the current is going to flow in the same direction as the period T1 while the current is attenuated by the energy accumulated in the reactor L.
Diode D4, power supply S, reactor L, diode D1,
Current flows through the capacitor C. In the period T3, the ignition signal is applied to the GTO similar to the period T1 again, so that the current increases again, and similarly, the current decreases in the period T4. By repeating this process, the current can be increased and decreased at high frequencies to control the instantaneous waveform and thus the phase and waveform.
In the example of FIG. 2, for the sake of explanation, the modulation frequency is not selected so high as to the power supply frequency, so that the current waveform has a relatively irregular waveform, but if the modulation frequency is increased, a smoother waveform is obtained. can do.

[Problems of background technology]

This circuit has the following problems. That is, the relationship between the input voltage and the output voltage requires that the capacitor voltage ec on the DC side is always higher than the absolute value e1 of the input AC voltage e1, as shown in FIG. Therefore, it cannot be applied to a DC load that requires continuous control from zero voltage, for example, when the DC motor is gradually increased in voltage to control the rotation speed. In such a case, a circuit capable of changing the voltage must be added to the DC output side.

[Object of the Invention]

The present invention has been made in consideration of the above points, and in a state where a direct current voltage is continuously controlled and a large load is applied, the phase and waveform of the alternating current are controlled at a high frequency to reduce the influence on the outside. The purpose is to provide a circuit.

[Outline of Invention]

In order to achieve the above-mentioned object, the present invention provides a circuit in which a self-extinguishing semiconductor element and a thyristor are connected in antiparallel.
Connect in series and connect the middle point to one terminal of the AC power supply. Also, connect two sets of circuits in which the self-extinguishing semiconductor element and the diode or thyristor are connected in anti-parallel, and connect the middle point to the AC power supply. Connected to the other terminal of the, and the other ends of the circuits connected in anti-parallel are connected to each other between the anodes and the cathodes to form a bridge circuit, and the DC output voltage is extracted from the connection point between the anodes and the connection point between the cathodes, The phase and the waveform of the alternating current flowing through the alternating current power supply by operating the self-extinguishing semiconductor element when the direct current output voltage is increased by controlling the firing phase control angle of the thyristor and the direct current output voltage becomes maximum. It is intended to provide an AC / DC converter for controlling.

〔Example〕

Hereinafter, the present invention will be described with reference to FIGS. 4 to 6.

FIG. 4 shows an embodiment of the present invention. This circuit has the diodes D1 and D2 in the circuit of FIG.
It is replaced with H1 and TH2, and the same symbols as in FIG. 1 indicate the same elements.

In the circuit of FIG. 4, GTO thyristors GT1 to GT4
If no signal is applied to the gates of thyristors TH1 and TH2
The diodes D3 and D4 operate merely as a mixed bridge circuit, and continuous DC output voltage control can be performed by applying a phase control pulse to the thyristors TH1 and TH2.

Fig. 5 shows this state. Thyristors TH1, TH
The DC output voltage is continuously controlled by gradually approaching the gate signal given to 2 (ie, the phase control angle α) from 180 ° to 0 °.

Fig. 6 shows thyristors TH1 and TH when performing high frequency modulation operation.
2 shows the gate signal given to 2. This gate signal is the maximum DC voltage GTO thyristor GT1
~ GT4 in cooperation with each other, the circuit of Fig. 4 has the same function as the circuit of Fig. 1, so that high frequency modulation operation can be performed from this point.

When such an operation is performed, GTO thyristor GT1 ~ GT
In the period when 4 is not operated, the input current is naturally the same as that of the conventional normal rectifier, so the input power factor is relatively good, and the generation of harmonics due to waveform distortion is not improved at all compared to the conventional rectifier. However, in this region, the input power itself is low, so the reactive power generated is low, and the absolute value of the current is low, so the harmonics are low. When the DC output voltage becomes large and the power consumption becomes large, the original function by high frequency modulation is exerted.

FIG. 7 is a circuit diagram showing another embodiment of the present invention, in which the diodes D3 and D4 in FIG.
It is the same as the embodiment of FIG. 4 except that it is replaced with TH4.

The control of the thyristors TH1 to TH4 in this circuit is the fourth
Similar to the circuit shown in the figure, when the DC load voltage is small, it operates as a normal phase control rectifier, and in the region where the DC load voltage is large, it operates as a high frequency modulation AC / DC converter.

FIG. 8 shows an example of the gate signal given to each thyristor when the input power is small in the embodiment of FIG. 7, and by sequentially controlling the phase control angle α as in the case of FIG. The average value of the DC voltage can be controlled from a small value to a large value.

Fig. 9 shows thyristor TH after the DC voltage becomes maximum.
The gate pulses to be given to 1-TH4 and GTO thyristors GT1-GT4 are shown, and the circuit of FIG. 7 is made to perform high frequency modulation operation like the one shown in FIG.

(Modification)

Although a single-phase AC / DC converter has been described in the above embodiment, the present invention can also be applied to a polyphase converter.

〔The invention's effect〕

As described above, the present invention forms a bridge circuit by two sets of anti-parallel circuits including a self-extinguishing semiconductor device such as GTO and a thyristor and two sets of anti-parallel circuits including a self-extinguishing device such as GTO and a diode or thyristor. Configure this bridge circuit as a phase control rectifier when the input power is low,
Further, since the high-frequency modulation rectifier is operated when the input power becomes large, it is possible to continuously increase the output voltage from zero without requiring a special voltage regulator. Moreover, when the input current is large and the load power is large, the input current phase is controlled to be equal to the input voltage phase to improve the input power factor, reduce voltage drop and unnecessary heat generation, and reduce the Not only can the effects on other devices be reduced, but the input current waveform can be controlled to be close to a sine wave to reduce the generation of harmonic currents.

[Brief description of drawings]

FIG. 1 is a diagram showing a main circuit of a conventional high-frequency modulation AC / DC converter, FIG. 2 is an operation explanatory diagram of the circuit of FIG. 1, and FIG.
FIG. 4 is an explanatory diagram of input / output voltage relations of the circuit of FIG. 4, FIG. 4 is a circuit diagram of an embodiment of the present invention, FIG. 5 is a diagram showing waveforms of respective parts when the circuit of FIG. FIG. 7 is a diagram showing waveforms at various parts when the circuit of FIG. 4 is subjected to high frequency modulation operation, FIG.
FIG. 8 is a circuit diagram of another embodiment of the present invention, FIG. 8 is a diagram showing waveforms at various parts when the circuit of FIG. 7 is operated in phase control, and FIG.
The figure is a diagram showing waveforms at various parts when the circuit of FIG. 7 is subjected to high frequency modulation operation. GT ... GTO, D ... Diode, TH ... Thyristor.

Claims (1)

[Claims] 1. A self-extinguishing semiconductor device and a thyristor are connected in antiparallel and two sets of circuits are connected in series, the middle point of which is connected to one terminal of an AC power source. Alternatively, two sets of circuits connected in anti-parallel with a thyristor are connected in series, the middle point is connected to the other terminal of the AC power supply, and the other ends of the circuits connected in anti-parallel are connected to each other between anodes and cathodes. A bridge circuit is configured, and a DC output voltage is taken out from the connection point between the anodes and the connection point between the cathodes, and the firing phase control angle of the thyristor is controlled to increase the DC output voltage, thereby maximizing the DC output voltage. An AC / DC converter that controls the phase and waveform of the AC current flowing through the AC power supply by operating the self-extinguishing semiconductor element when it becomes low.