JPH0993939A - Rectifying/smoothing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rectifying/smoothing circuit which can suppress a harmonic current with an economical and simple construction. SOLUTION: When the output AC voltage of an AC power supply 1 is a positive side voltage, the voltage of a charged capacitor 3 is superposed on the output AC voltage of an AC power supply 1 and the resultant voltage is applied to a load 5 and, further, the voltage is also applied to a capacitor 2 to charge it. When the output AC voltage of an AC power supply 1 is a negative side voltage, the voltage of the charged capacitor 2 is superposed on the output AC voltage of an AC power supply 1 and the resultant voltage is applied to the load 5 and, further, the voltage is also applied to the capacitor 3 to charge it.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectifying / smoothing circuit, and more particularly to a capacitor input type rectifying / smoothing circuit.

[0002]

2. Description of the Related Art Generally, a capacitor input type rectifying / smoothing circuit is composed of a diode bridge 12 and a smoothing capacitor 13, as shown in the circuit diagram of FIG. One pair of opposing terminals of the diode bridge 12 are connected to both terminals of the AC voltage source 11, and the other pair of opposing terminals are connected to both terminals of the smoothing capacitor 13 and the load 14, respectively.

In this conventional rectifying / smoothing circuit, the AC power source 1
The AC voltage from 1 is full-wave rectified by the diode bridge 12, and then smoothed by the smoothing capacitor 13, and the DC voltage obtained is applied to the load 14.

[0004]

However, in the conventional capacitor input type rectifying / smoothing circuit described above, an AC voltage equal to or lower than the charging voltage value of the smoothing capacitor 13 is blocked by the diode of the diode bridge 12, so that a current flows. There is no time, resulting in a pulsed current waveform,
Harmonic current is generated. This harmonic current causes distortion in the output AC voltage waveform of the AC power supply, which adversely affects other devices connected to the AC power supply.

Therefore, in order to suppress the generation of higher harmonics, a series circuit of a resistor and a transistor is connected in parallel with a smoothing capacitor, and a capacitor charging voltage and a capacitor input voltage are compared by a comparator to determine the capacitor charging voltage. A rectifying and smoothing circuit has been proposed in which a transistor is turned on when the input voltage is higher than the capacitor input voltage so that the input current from the power source flows through the resistor (Japanese Patent Laid-Open No. Hei 5).
No. 38145).

However, this conventional circuit requires a circuit element such as a series circuit of a resistor and a transistor connected in parallel with a smoothing capacitor and a comparator, which causes a problem that the circuit is complicated and expensive.

[0007] The present invention has been made in view of the above points,
An object of the present invention is to provide a rectifying / smoothing circuit that can suppress the generation of harmonic current at a low cost with a simple configuration.

[0008]

In order to achieve the above-mentioned object, the present invention has one pair of terminals facing each other connected to the first and second terminals of an AC power source, and the other pair of terminals facing each other. A rectifier circuit connected to the positive side terminal and a negative side terminal of the load, and a first capacitor connected between a connection point between the first terminal of the AC power supply and the rectifier circuit and the negative side terminal of the load, The configuration has a connection point between the second terminal of the AC power supply and the rectifier circuit and a second capacitor connected between the negative side terminal of the load. Here, the rectifier circuit is, for example, a diode bridge in which diodes are arranged on each of four sides.

In the present invention, the first capacitor is charged with an alternating voltage from the alternating voltage for a positive half cycle period,
The charging voltage is superimposed on the AC voltage in the negative half cycle period of the AC voltage and input to the rectifier circuit, and the second capacitor is charged by the AC voltage in the negative half cycle period from the AC voltage, and the charging is performed. The voltage is superimposed on the AC voltage during the positive half cycle of the AC voltage and input to the rectifier circuit.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a circuit diagram of an embodiment of a rectifying / smoothing circuit according to the present invention. In this embodiment,
As shown in FIG. 1, it comprises a diode bridge 4 and capacitors 2 and 3. One pair of opposing terminals of the diode bridge 4 is connected to the first and second terminals of the AC power source 1, and the other pair of opposing terminals is connected to the positive side terminal and the negative side terminal of the load 5, respectively. There is.

A capacitor 2 is connected between the connection point between the first terminal of the AC power supply 1 and the diode bridge 4, and the connection point between the negative side terminal of the load 5 and the diode bridge 4. Further, a capacitor 3 is connected between the connection point between the second terminal of the AC power supply 1 and the diode bridge 4, and the connection point between the negative side terminal of the load 5 and the diode bridge 4.
The respective capacitance values of the capacitors 2 and 3 are set to be equal.

Next, the operation of the embodiment of the present invention will be described with reference to the operation explanation signal waveform diagram of FIG. First, when the output AC voltage of the AC power supply 1 is in the positive half cycle, it is converted into a DC voltage via the capacitor 2 and the diode bridge 4 and applied to the load 5. At this time, the capacitor 2 is charged with the voltage during the positive half cycle of the AC voltage.

When the output AC voltage of the next AC power supply 1 is a negative half cycle, the AC voltage is converted into a DC voltage via the capacitor 3 and the diode bridge 4 and applied to the load 5. At this time, during the negative half cycle of the AC voltage, the capacitor 3 is charged with the voltage.

After that, when the output AC voltage of the AC power supply 1 is a positive voltage, the voltage charged in the capacitor 3 is applied to the load 5 in a form of being superimposed on the output AC voltage of the AC power supply 1. Moreover, the capacitor 2 is also charged with the voltage. Further, when the output AC voltage of the AC power supply 1 is a negative voltage, the voltage charged in the capacitor 2 is applied to the load 5 in the form of being superimposed on the output AC voltage of the AC power supply 1,
In addition, the capacitor 3 is charged with the voltage. Less than,
The same operation as described above is repeated.

Therefore, in this embodiment, the AC power source 1
Even when the output AC voltage of is lower than the voltage value at the end of the load 5, the charging voltage of the capacitors 2 and 3 can be applied to the load 5 without being blocked by the diode bridge 4. As shown in FIG. 2, the pulse-shaped current waveform portion is not generated, and the harmonic current can be suppressed.

The present invention can be applied not only to the diode bridge but also to other rectifying / smoothing circuits using a diode such as a capacitor input type half wave rectifying circuit or a center tap type full wave rectifying circuit. It is a thing.

[0017]

As described above, according to the present invention,
The first capacitor is charged with an alternating voltage of a positive half cycle period from the alternating voltage, and the charging voltage is superimposed on the alternating voltage of the negative half cycle period of the alternating voltage and input to the rectifier circuit. Is charged by the AC voltage in the negative half-cycle period from the AC voltage, and the charging voltage is superimposed on the AC voltage in the positive half-cycle period of the AC voltage and input to the rectifier circuit. Even if the AC voltage is lower than the voltage value at the load end, it can be applied to the load without being blocked by the rectifier circuit (especially the diode bridge). Can be suppressed. Further, as compared with the conventional circuit, the only additional component is the capacitor, so that the harmonic current can be suppressed with a simple and inexpensive structure.

[Brief description of drawings]

FIG. 1 is a circuit diagram of one embodiment of the present invention.

FIG. 2 is a signal waveform diagram for explaining the operation of FIG.

FIG. 3 is a circuit diagram of a conventional example.

[Explanation of symbols]

 1 AC power supply 2 First capacitor 3 Second capacitor 4 Diode bridge 5 Load

Claims (2)

[Claims] 1. A rectifier in which one pair of terminals facing each other is connected to first and second terminals of an AC power source, and the other pair of terminals facing each other is respectively connected to a positive side terminal and a negative side terminal of a load. A circuit, a first capacitor connected between a connection point between the first terminal of the AC power supply and the rectifier circuit and a negative terminal of the load, a second terminal of the AC power supply and the rectifier circuit And a second capacitor connected between the negative side terminal of the load and the negative side terminal of the load. 2. The rectifying / smoothing circuit according to claim 1, wherein the rectifying circuit is a diode bridge in which a diode is arranged on each of four sides.