JPS6245794B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacitor smoothing rectifier circuit, and particularly to power factor improvement of a voltage doubler rectifier circuit.

A conventional voltage doubler rectifier circuit will be explained with reference to FIG.
1 is a rectifier diode, 2 is a smoothing capacitor, 3 is a smoothing reactor, 4 is a load, and 5 is a power supply. FIG. 1 shows the basic configuration of a commonly used voltage doubler circuit. To briefly explain the operation of this circuit, during the half-wave period of the power supply voltage, one of the rectifying diodes 1 works to generate a signal through the smoothing reactor 3.
One smoothing capacitor 2 is charged, and in the next half-wave period, the other smoothing capacitor 2 is charged via the smoothing reactor 3 by the action of the other diode 1. Since the two smoothing capacitors are connected in series with each other, a DC voltage twice as high as the peak of the power supply voltage charged in one smoothing capacitor is applied to the load 4. The decisive problem with this circuit is that since the smoothing capacitor 2 is not completely discharged, a so-called oxidation voltage remains for the DC voltage, and the charging current is limited to the period when the power supply voltage is higher than this residual voltage, that is, at the peak part of the power supply voltage. This means that it only lasts for a short period of time. Therefore, a large third harmonic component is generated in the input current, causing a decrease in the power factor.

The present invention has been made to improve the above defects. That is, during a period when the charging current of the capacitor 2 does not flow, in other words, during a period when the power supply voltage is low, current is caused to flow by short-circuiting the power supply via the smoothing reactor 3, and the third harmonic component of the input current is reduced. That's what I'm trying to do. Moreover, a semiconductor switch is provided in the short circuit, and the waveform of the input current is compared with a sinusoidal reference voltage to control the semiconductor switch so that the input current approaches a sinusoidal wave.

The present invention will be explained below with reference to an embodiment shown in FIGS. 2 and 3. FIG. 2 shows the basic configuration of the implemented circuit, and FIG. 3 shows the relationship between power supply voltage and input current. 6 is a diode for preventing discharge of the capacitor 2, 7 is a transistor, 8 is a current detector, 9 is a comparison circuit with hysteresis, and 10 is a driver for the transistor 7. In addition, a is a sine wave-like reference voltage upper limit voltage (reference voltage +
hysteresis voltage), b is a sinusoidal reference voltage lower limit value (reference voltage - hysteresis voltage) as shown in the figure, c is an input current, d is a power supply voltage, and e is a drive signal for the transistor 7. Next, the operation of this circuit will be explained. The rectification method is exactly the same as the conventional voltage doubler rectification (see FIG. 1), so a description thereof will be omitted. The power supply short circuit consists of smoothing reactor 3, diode 1,
It is composed of a transistor 7 and a current detector 8. Two transistors 7, smoothing reactors 3, rectifying diodes 1, discharge prevention diodes 6, and two smoothing capacitors 2 are provided.Hereinafter, the ones located on the upper side of the circuit diagram are referred to as ~, and the ones located on the lower side are referred to as ``side''. I will call it ~. In Fig. 3, in the period of electrical angle 0 to π, the side short circuit is
During the period of electrical angle π to 2π, the side short circuit is working. Waveform e is a drive signal for transistor 7, and the driver for the side transistor,
Since the drivers of the side transistors are configured relative to each other, a single signal controls the two transistors 7. That is, the drive signal e
The period on the side is the ON signal for the side transistor, and the period on the side is the ON signal for the side transistor. Also, this signal
This is exactly the same as the output signal of the comparison circuit 9. 0~π
Since a forward voltage is applied to the side transistor during the period , the side transistor 7 is turned on from the electrical angle of 0°. When the input current c reaches the reference voltage upper limit value, the output of the comparator circuit 9 drops to -Vss, and the side transistor is turned off. When the input current c decays to the reference voltage lower limit, the side transistor is turned on again. In this way, the on and off cycles are repeated, but as the charging current of the side transistor approaches π/2, the charging current of the side transistor increases rapidly, so the off period of the side transistor is greatly extended. When the point of π/2 is exceeded, the charging current of the side capacitor is attenuated and the side transistor starts on-off oscillation again. During the period from 0 to π, an on signal is also applied to the side transistor, but since no forward voltage is applied to the side transistor at this time, it will not turn on.

In exactly the same manner as described above, the side transistor operates during the period from π to 2π. The energizing current approaches a sine wave like the input current C waveform, and the power factor with the power supply voltage d waveform is also significantly improved. According to actual measurements, the third harmonic is 35% and the fifth harmonic is 40%.
%, and the overall power factor was significantly improved from 76% with the conventional circuit system to 92%. It was also found that ripples in the DC voltage generated across the smoothing capacitor 2 can be suppressed.

Other embodiments and application examples will be described with reference to FIGS. 4 and 5. In Fig. 4, 11 is a phase direction chopper, 1
2 is a current detection resistor, 13 is a variable resistor, and 14 is a reference voltage input terminal. In FIG. 2, a phase directional chopper 11 is used instead of the discharge prevention diode 6 and the transistor 7. Current detection was carried out by detecting a voltage drop due to minute resistance. Also, as the reference voltage, according to the above embodiment,
Although the power supply voltage itself is input, in this example, it can be adjusted depending on the size of the load 4. In other words, as the load increases, the charging current increases, resulting in a deviation from the sine wave current. Therefore, the reference voltage level is raised, and the short-circuit current is also increased in proportion to the charging current, resulting in a sinusoidal current.

In FIG. 5, the number of smoothing reactors 3 is one, and the discharge prevention diode 6 and the smoothing reactor 3 are arranged so that the capacitor charging current does not flow therethrough. The operating principle of this circuit system is almost the same as that shown in FIG. 4, so a description thereof will be omitted. The greatest advantage obtained by arranging the components as shown in FIG. 5 is that the diode loss and smoothing reactor loss in the charging circuit loop can be reduced, and the efficiency of the power supply circuit can be increased. The degree of efficiency improvement depends on the reactor used, the capacity of the diode, etc., but in experiments, an efficiency improvement of 25% was achieved.

The present invention provides a voltage doubler rectifier circuit that uses a single-phase power source as an input power source, by providing a circuit that short-circuits the power supply terminals via an inductive element and a semiconductor switch, and during periods other than the capacitor charging period. Since the semiconductor switch is configured to be turned on and off according to the timing, harmonics of the input current, especially the third and fifth harmonics, can be greatly reduced, and the power factor can be improved. Furthermore, since the energy of the inductive element accompanying the on/off of the semiconductor switch is supplied to the smoothing capacitor via the diode, ripples in the DC voltage can be reduced. Furthermore, the waveform of the input current deviates from the sine wave current by comparing the input current with a sinusoidal reference voltage whose level is adjusted according to the size of the load and outputting the on/off timing signal for the semiconductor switch. The power factor with the power supply voltage waveform can be improved by creating a sinusoidal waveform.

[Brief explanation of the drawing]

Fig. 1 is a diagram of a conventional voltage doubler rectifier circuit, Fig. 2 is a basic configuration diagram of one implemented circuit, Fig. 3 is a diagram showing the relationship between power supply voltage and input current of the embodiment shown in Fig. 2, and Fig. 4 is a diagram showing the relationship between power supply voltage and input current of the embodiment shown in Fig. The figure is a circuit diagram showing another embodiment, and FIG. 5 is a circuit diagram showing an applied example. 1... Rectifier diode, 2... Smoothing capacitor, 3... Smoothing reactor, 4... Load, 5...
Power supply, 6... Diode for preventing discharge of capacitor 2, 7... Transistor, 8... Current detector,
9... Comparison circuit with hysteresis, 10... Driver of transistor 7, 11... Phase directional chopper, 12... Current detection resistor, 13... Variable resistor, 14... Reference voltage input terminal, a... See Voltage upper limit value, b...Reference voltage lower limit value, c...Input current, d...Power supply voltage, e...Drive signal for transistor 7, +Vcc...+Control power supply, -Vss...-
Control power supply.

Claims (1)

[Claims] 1. In a power supply circuit connected to a voltage doubler rectifier using a single-phase power source as an input power source, an inductive element provided on the input side, a semiconductor switch that shorts between power supply terminals via the inductive element, and the above-mentioned inductive current detection means for detecting an input current consisting of a short circuit current flowing through the element and the semiconductor switch and a charging current flowing into a capacitor provided in the voltage doubler rectifier circuit;
An adjusting means for adjusting the level of the sinusoidal reference voltage according to the magnitude of the load, and comparing the detected input current and the adjusted reference voltage to output an on/off timing signal for the semiconductor switch. A power supply device comprising a comparison means and a driver inputting the output of the comparison means, the driver outputting a drive signal for turning on and off the semiconductor switch.