JPS6074963A - Chopper circuit - Google Patents

Abstract

PURPOSE:To obtain a small-sized inexpensive chopper circuit by circulating part of energy stored in an inductance of an AC power source, and absorbing it by a capacitor, thereby reducing the electrostatic capacity of the capacitor. CONSTITUTION:When a switch 52 is turned OFF, energy stored in an inductance of an AC power source for producing the lower voltage of U-phase and W-phase voltages is supplied through a route of I2 to a load circuit 6. Accordingly, when the switch 52 is turned OFF, the energy to be absorbed by a capacitor 32 is becomes that subtracted by the inductance of a low voltage power source of W phase from the power source inductance of W phase. Thus, the electrostatic capacities of the capacitors 31, 32 can be reduced. The inductance of a smoothing reactor 61 may be the value subtracted by the power source inductance, thereby reducing the size.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention rectifies alternating current voltage to convert it into direct current voltage, and controls on/off of this direct current voltage using a semiconductor switch such as a thyristor or a transistor. [Prior art and its problems] FIG. 1 is a circuit diagram showing a general chopper circuit.

The AC input is insulated and converted to the necessary voltage by the transformer 1, and becomes the input to the rectifier 2.

The output of the off switch (also simply referred to as a switch) 5 is connected to a load circuit 6 composed of a smoothing reactor 61, a smoothing capacitor 62, and a load 63. In addition, a capacitor 3 is provided between the positive terminal (P) and negative terminal (N) of the output of the rectifier 2 for the purpose of absorbing the energy accumulated in the inductance on the E source side. Freewheeling diodes 7 for circulating the energy stored in the inductances are connected in parallel.

In such a circuit configuration, when the switch 5 is on, the secondary side line voltage of the transformer 1 is applied to the load circuit 6, and when the switch 5 is off, the freewheeling diode 7 is applied to the load circuit 6.
becomes conductive and becomes 0. At this time, assuming that the rectifier diodes 21 and 26 are conductive and the U phase and W phase are supplying power, when the switch 5 is on, the arrow 1 in the figure
1. In the OFF state, current flows through the R path of arrow wire 2. In this way, since the current is cut off quickly by the switch 5, there is a means for absorbing the energy accumulated in the inductance between the lines on the AC input power supply side of the rectifier 2 when the switch is in the on state, when the switch 5 is turned off. is necessary. Therefore, capacitor 3 is connected to rectifier 2.
DC output P.

8, but in this case: 1. The operating voltage is high (operating voltage - line voltage + jump voltage when switched off).

2. Large capacitance (to absorb the energy accumulated in the inductance between the lines).

For these reasons, large and expensive capacitors are required. Furthermore, as the on/off switch 5, a semiconductor such as a silica or a transistor is used, but like a capacitor, this also requires something that can withstand the line voltage plus the voltage that bounces up when the switch is turned off, making it expensive. becomes. Furthermore, the voltage ripple applied to the load circuit 6 is large, and the load 63
If it is necessary to suppress the voltage ripple of the smoothing reactor 61 and the smoothing capacitor 62 to a small value, there are disadvantages such as the need for large and expensive smoothing reactor 61 and smoothing capacitor 62.

[Purpose of the invention]

This invention reduces the energy accumulated in the inductance of the AC power supply connected to the rectifier, the capacitance of the capacitor to absorb it when the switch turns off, and the voltage applied to the switch. (The applied voltage is lower than the DC output voltage.) Furthermore, the present invention aims to provide a small and low-cost chopper device by reducing the inductance of the smoothing reactor.

[Key points of the invention]

This invention consists of an AC input quadrature having a neutral point and an intermediate terminal, which extracts each phase voltage of input AC and divided phase voltages obtained by dividing these voltages, and which rectifies the line voltage of the higher voltage. A high-voltage rectifier circuit that rectifies the line voltage with a lower voltage, and a low-voltage rectifier circuit that rectifies the line voltage with a lower voltage are provided.
An on/off switch is used to connect the terminals (positive pole) and N (negative pole), a load containing a smoothing reactor is connected to the low voltage rectifier circuit side, and the voltage applied to this load circuit is controlled by a switch. When the switch is off, a portion of the energy stored in the inductance of the AC power source is allowed to flow through the low-voltage rectifier circuit and the load, and only the remaining amount is transferred to the rectifier circuit's P.
, 8, the capacitance of the capacitor is reduced, and the inductance of the smoothing reactor is also reduced.

[Embodiments of the invention]

Figure 2 is a circuit diagram showing an embodiment of the present invention, and Figure 3 is a waveform diagram showing waveforms of various parts. Transformer 11 has neutral point 1-T
Since it has an intermediate terminal on its secondary side, the input AC U and V.

At the same time as the nominal phase voltage of W is extracted, the divided phase voltages obtained by dividing these voltages are also extracted.

Each phase voltage, that is, a phase voltage with a high voltage, is applied to a rectifier 2, and each divided phase voltage, that is, a phase voltage with a low voltage is applied to a rectifier 8. The positive and negative sides of the rectifiers 2 and 8 are connected to each other via switches 51 and 52, respectively, and the output side of the rectifier 8 is equipped with a smoothing reactor 61, a smoothing capacitor 62, and a load 63 as in Figure 1. A load circuit 6 consisting of the following is connected. Further, capacitors 31 and 32 are connected between the P side of the rectifier 2 and the neutral point H of the AC power supply, and between the N side and the neutral point H, respectively.

In such a configuration, when switches 51 and 52 are both on, diode 2 in the upper arm of rectifier 2
1 to 23 and a predetermined one of the diodes 24 to 26 of the lower arm are conductive, and the load circuit 6 receives the line component of the phase voltage (
line voltage) is applied. Note that at this time, the diodes 81 to 86 of the rectifier 8 are the same as the diodes 21 to 2 of the rectifier 2.
It is blocked by 6 and does not conduct. On the other hand, if one of the switches 51, 52 is on and the other is off, each predetermined one of the diodes of the rectifier 2.8 conducts, and the load circuit 6 receives a positive (negative) phase voltage. A differential voltage with the negative (positive) partial voltage phase voltage is applied.

When both switches 51 and 52 are off, predetermined one each of diodes 81 to 83 on the upper arm of the rectifier 8 and diodes 84 to 86 on the lower arm are conductive, and the load circuit 6 is supplied with a divided voltage. A line component (line voltage) of the phase voltage is applied. At this time, the diodes 81 to 86 of the rectifier 8 also serve as freewheeling diodes. Therefore, by controlling the on/off states (there are four types of states) of the switches 51 and 52, the output voltage or current of the chopper can be controlled. If you line up,
Switch 51 off, 52 off → switch 51, 52 off → switch 51 off, 52 on.

When the OFF state is repeated, the output of the chopper circuit, that is, the voltage waveform applied to the load circuit 6 becomes as shown in FIG. 3(A). Note that FIG. 3←) shows the voltage waveform applied between the neutral point H of the power supply and the switch output terminal P1 or N1.

Next, in FIG. 2, the operation when the switches 51 and 52 are both turned off from the state where the switch 51 is off and the switch 52 is on will be described. At this time,
For example, assuming that the diode 26 of the rectifier 2 and the diode 81 of the rectifier 8 are conductive, the difference voltage between the lower voltage of the U-phase voltage (divided phase voltage) and the W-phase voltage (higher voltage) Power is supplied to the load circuit 6, and as a result, the power is supplied through the path of ■1. AL is playing. Next, when the switch 52 is turned off, the diode 86 becomes conductive, and current flows through the path (2). At this time, the energy stored in the inductance of the AC power supply that takes the lower voltage of each of the U-phase and W-phase is supplied to the load circuit V'66 through the path (2), so the switch 52 is turned off. As a result, the energy to be absorbed by the capacitor 32 is the energy stored in the inductance obtained by subtracting the inductance of the W-phase low-voltage power supply from the W-phase power supply inductance. It can be made smaller than . In addition, since the energy accumulated in the inductance of the AC power supply that takes out the lower voltage of the U phase and W phase is passed through the load circuit 6, the inductance of the smoothing reactor 61 is also the value obtained by subtracting the above power supply inductance. Therefore, the smoothing reactor can also be small and inexpensive. In other words, as shown in the third [J(clI), the voltage ■s applied to the output terminal of the on/off switch is the difference voltage between the input phase voltage and the divided phase voltage, and therefore, as shown in FIG.
It is clear that it is lower than the conventional one as shown in c).

〔Effect of the invention〕

According to this invention, there is an AC input cadence that can take out the neutral point and two types of phase voltages, high and low, and a rectifier that rectifies the line voltage of the higher voltage. A low-voltage rectifier that rectifies the line voltage of the lower voltage line is provided, and the P and N of the DC power of each 6f5 rectifier are connected via a switch to connect the lower voltage line voltage.
Smoothing reactor on the IT voltage side, flat? By connecting a load circuit consisting of a single capacitor and a load, the voltage applied to the on/off switch becomes the difference between the two high and low phase voltages with respect to the neutral point of the input quadrature.

■ Out of the energy stored in the inductance of the AC input power supply, the energy of the inductance of the power supply from which the lower AC voltage is taken out flows back to the load circuit 6, so when the on/off switch is turned on, the energy in the inductance of the power supply is transferred to the capacitor 31.
32 only needs to absorb a small amount of energy.

It turns out. As a result, the following effects can be obtained.

1. The voltage applied to the on/off switch is lower, resulting in lower cost.

2. The capacitance of capacitors 31 and 32 is small,
Small size and low price.

3. The inductance of the smoothing reactor can be reduced, resulting in smaller size and lower cost.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a conventional example of a chopper circuit, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Fig. 3 is a waveform diagram showing waveforms of each part. ...Transformer, 2,8...Rectifier 1'rl, 3 g31.32...Capacitor, 5,51,52...Switch, 6...
・Load circuit, 61...Smoothing reactor, 62・
... Smoothing capacitor, 63 ... Load, 7
...Freewheeling diode, 21-26.81-86
・・・・・・Diode agent Patent attorney Akio Namiki Agent Patent attorney Akira Matsuzaki

Claims (1)

[Claims] A transformer that has a neutral point and an intermediate terminal and extracts each phase voltage from input AC and a divided phase voltage obtained by dividing these voltages, and a first rectifier that rectifies the line component of each phase voltage. a second rectifier that advects the line component of each of the divided phase voltages, and connecting the positive pole sides and the negative pole sides of the DC outputs of the first and second rectifiers through switching means, respectively; Inserting capacitors between the neutral point of the transformer and the positive and negative electrode sides of the first flow device, turning on one or both of the switches,
By controlling off, the output voltage or electric current b[δ
A chopper circuit characterized by controlling.