JPH07303376A - Sine wave rectifier circuit - Google Patents

Abstract

PURPOSE:To discharge the energy stored in reactors to a load through inverse- parallel circuits by alternately controlling the turn-on/off of two switching elements connected to each other in series at a frequency higher than that of AC power supply. CONSTITUTION:A sine wave rectifier circuit is provided with capacitors 2a, 2b, and 2c and serial circuits of a diode 3a and reactor 4a, diode 3c and reactor 4b, and diode 3e and reactor 4c corresponding to each phase of AC power supply 1. Diodes 3b, 3d, and 3f are respectively connected in series with the diode 3a, 3c, and 3e between output terminals t1 and t2. As a result, an input current having a power factor of '1' and sine-wave waveform is obtained without making any complicated control, because the energy stored in the reactors is discharged to a load through the antiparallel diodes connected in parallel with the switching elements.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sine wave rectifier circuit having an input terminal connected to an AC power supply and obtaining an input current having a good waveform and power factor characteristics.

[0002]

2. Description of the Related Art Capacitor input type rectifier circuits are widely used in home appliances and the like because they have a simple structure and are advantageous in terms of structure cost. However, there is a problem that the output current contains harmonics, the power factor is low, and the power supply system is adversely affected.

Various circuits have been proposed in order to solve the above-mentioned problems of the conventional capacitor input type rectifier circuit. However, the circuit configuration is complicated, and complicated control such as PWM (pulse width modulation) is required. It is necessary and there is a problem in manufacturing cost.

Therefore, the inventors of the present application proposed a sine wave rectifier circuit which has a simple circuit configuration and is easy to control, in a collection of 1993 sine wave converter of the 1993 National Conference of Industrial Applications of the Institute of Electrical Engineers of Japan. There is.

FIG. 5 is a circuit diagram showing the configuration of the proposed sine wave converter. Capacitors 2a and 2b are connected in series between terminals of an AC power supply 1,
A diode 3a and a reactor 4a are connected in series with each other between a connection point of a and the AC power supply 1 and the output terminal t1. Similarly, a diode 3d and a reactor 4b are connected in series with each other between a connection point between the capacitor 2b and the AC power supply 1 and the output terminal t2, and a capacitor 5 and a load RL are connected between the output terminals t1 and t2. , Connected in parallel with each other.

Further, switching elements 6a and 6b are connected in series between the output terminals t1 and t2, and anti-parallel diodes 7a and 7b are connected in parallel to the switching elements 6a and 6b, respectively. The connection points of the switching elements 6a and 6b and the connection points of the capacitors 2a and 2b are connected to each other.

Further, the capacitor 2b and the diode 3
A diode 3c is connected between the connection point of d and the connection point of the diode 3a and the reactor 4a, and the capacitor 2
The diode 3b is connected between the connection point of a and the diode 3a and the connection point of the diode 3d and the reactor 4b.

Next, the operation of the proposed sine wave converter having such a configuration will be described.

FIG. 6 is an explanatory diagram showing the operation of the proposed sine wave converter.

The circuit operation has four modes during a positive half cycle of the power supply voltage, and each mode is repeated in accordance with switching. Mode 1 When the switching element 6a is turned on as shown in FIG. 6 (A), a current flows through the path passing through the capacitor 2a and the reactor 4a, and energy is stored in the reactor 4a. Mode 2 When the switching element 6a is turned off, the energy stored in the reactor 4a is released to the load by the path passing through the antiparallel diode 7b of the switching element 6b, as shown in FIG. 6 (B). Switching element 6
The current flowing between the series connection point of a and 6b and the series connection point of the capacitors 2a and 2b is an algebraic sum of the current due to the energy release of the reactor 4a and the current due to the accumulation of energy in the reactor 4b. -Mode 3 In mode 2, when the energy stored in the reactor 4a has been discharged to the load, the mode moves to mode 3 shown in Fig. 6 (C), and the energy is stored in the reactor 4b. Mode 4 When the switching element 6b is turned off, the energy of the reactor 4b is changed to the switching element 6a as shown in FIG. 6 (D).
Is discharged to the load through the anti-parallel diode 7a. Since the two switching elements 6a and 6b are alternately turned on and off, the energy storage in the reactor 4a starts at the same time as the energy release from the reactor 4b. When the release of the energy of the reactor 4b ends, the mode 1 is returned to, and the above four modes are repeated.

When the power supply voltage becomes a negative half cycle, the diodes 3b and 3c are turned on instead of the diodes 3a and 3d, and the circuit operation repeats the above modes 1 to 4.

In the proposed sine wave converter, the switching frequencies of the switching elements 6a and 6b are selected to be much higher than the frequency of the power supply, so that it can be considered that the power supply voltage in one cycle of switching is constant. Therefore, the current flowing through the reactors 4a and 4b becomes a triangular wave current proportional to the power supply voltage. The current flowing through the two reactors 4a and 4b is a discontinuous current having a phase shifted by a half cycle because energy is alternately accumulated and released.

That is, the current flowing through the reactors 4a and 4b is a discontinuous current whose average value is substantially proportional to the voltage. However, since the phases are shifted from each other by a half cycle, a continuous sinusoidal current is obtained. .

[0014]

The sine wave converter according to the above proposal rectifies the voltage of a single-phase AC power supply.

An object of the present invention is to provide a sine wave rectifier circuit which rectifies the voltage of a multi-phase AC power source by inserting a reactor on the AC side.

[0016]

In order to achieve the above object, the present invention is a sine wave rectifier circuit in which an input terminal is connected to an AC power source to make an input current sinusoidal, and each phase terminal of the AC power source. A plurality of capacitors each having one end connected to each other and the other ends commonly connected, and a diode and a reactor respectively connected between the connection point of these capacitors and the AC power source and one end of the output terminal of the sine wave rectifying plate circuit. Connected between the other end of the output terminal and the series connection point of the diode and the reactor, and the diode connected to the output terminal, and the mutual connection point of the plurality of capacitors. A series connection circuit of two switching elements connected to a common connection point, an anti-parallel diode connected in parallel to each of the switching elements, and La switching element, is characterized in that a control means for alternately on-off control at a frequency higher than the frequency of the AC power source.

[0017]

According to the present invention, the two switching elements connected in series are connected between the output terminals of the sine wave rectifier circuit, and the mutual connection points are connected to the common connection point of the plurality of capacitors. Alternately turns on and off at a frequency higher than the frequency of the AC power supply.

By this control, current flows through the series connection circuit of the diode and the reactor which are respectively connected between the connection point of the capacitor and the AC power supply and the output terminal, and energy is stored in the reactor. Then, via an anti-parallel diode connected in parallel to the switching element,
Energy is released into the load and a sinusoidal input current is obtained.

[0019]

【Example】

First Embodiment A first embodiment of the present invention will be described with reference to FIGS.

FIG. 1 is a circuit diagram showing the configuration of this embodiment, and FIG.
Is a line voltage and line current waveform diagram of this embodiment, and FIG. 3 is a frequency spectrum diagram of this embodiment.

The structure of this embodiment is basically based on the single-phase sine wave rectifier circuit described above, and capacitors 2a, 2b and 2c are provided for each phase of the three-phase AC power supply 1. Further, a series connection circuit of a diode and a reactor is provided corresponding to each phase. These series connection circuits are a series connection circuit of the diode 3a and the reactor 4a, a series connection circuit of the diode 3c and the reactor 4b, and a series connection circuit of the diode 3e and the reactor 4c.

Then, between the output terminals t1 and t2,
A diode 3b is connected in series with the diode 3a, a diode 3d is connected in series with the diode 3c, and a diode 3f is connected in series with the diode 3e. The configuration of the other parts of this embodiment is the same as that of the sine wave converter according to the proposal already described, corresponding to each phase.

FIG. 2 shows the line current waveform corresponding to the line voltage waveform when the present embodiment is operated under the same operating conditions as the proposed sine wave converter. Since the line voltage waveform of FIG. 2 leads the line current by 30 ° in phase, it is clear that the power factor is 1. Further, the waveform of the line current is a sine wave, and it can be seen from FIG. 3 that the frequency spectrum shows that the harmonics are decreasing, and particularly that the third harmonic is significantly decreasing. Second Embodiment Next, a second embodiment of the present invention will be described with reference to FIG.

FIG. 4 is a circuit diagram showing the configuration of this embodiment.

In this embodiment, the N-phase power supply voltage is rectified, and the same circuit configuration as that of the first embodiment is applied to each phase.

In this embodiment, generally, the same operation as in the first embodiment is performed with respect to the multi-phase power supply voltage, and the input current is sinusoidal with a simple sequence in which two switching elements are alternately turned on and off. Can be improved.

As described above, according to each of the embodiments, a chopper circuit provided for each phase causes a current proportional to the power supply voltage to flow and to superimpose them, without requiring complicated control with a simple configuration. It is possible to obtain a sinusoidal output current having a power factor of 1 with little ripple and excellent waveform characteristics.

[0028]

According to the present invention, each switching element of a series connection circuit of two switching elements connected between output terminals and connected to each other at a common connection point of a plurality of capacitors is provided. , If the on / off control is performed alternately at a frequency higher than the frequency of the AC power supply, current will flow in the series connection circuit of the diode and the reactor connected between the connection point of the capacitor and the AC power supply and the output terminal, respectively. Since the energy stored in is discharged through the anti-parallel diode connected in parallel with the switching element, a sinusoidal input current with excellent power characteristics and a power factor of 1 can be obtained without complicated control. be able to.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a line voltage and line current waveform diagram of the same example.

FIG. 3 is a frequency spectrum diagram of the same example.

FIG. 4 is a circuit diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 5 is a circuit diagram showing a configuration of a conventional sine wave converter.

FIG. 6 is a diagram showing the operation of a conventional sine wave converter,
(A)-(D) is explanatory drawing which shows four operation modes.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2a-2c Capacitors 3a-3f Diodes 4a-4c Reactor 5 Capacitors 6a, 6b Switching elements 7a, 7b Anti-parallel diode

Claims (1)

[Claims] 1. A sine wave rectifier circuit having an input terminal connected to an AC power supply and making an input current sinusoidal, wherein a plurality of terminals each having one end connected to each phase terminal of the AC power supply and having the other end connected in common. A capacitor, a series connection circuit of a diode and a reactor respectively connected between the connection point of these capacitors and the AC power supply and the output terminal of the sine wave rectifier circuit, and a series connection of the other end of the output terminal and the diode and the reactor. A diode connected between the connection points, and a series connection circuit of two switching elements connected between the output terminals and having mutual connection points connected to a common connection point of the plurality of capacitors; An anti-parallel diode connected in parallel to each switching element and these switching elements are higher than the frequency of the AC power supply. A sine wave rectifier circuit, comprising: a control unit that alternately turns on and off at a frequency.