JP2004129387A - Power supply apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply apparatus which can clear harmonics regulations using a simple structure, in a power supply which subjects the power voltage to voltage-doubler-rectification and outputs a high DC voltage. <P>SOLUTION: Switches SW1, SW2 are provided between junctions of each input terminal of a rectifying circuit 2 and voltage doubler rectification capacitors 4, 5. By controlling switches SW1, SW2 so as to be off for a prescribed time when powered up, cost reductions can be realized with the voltage doubler rectifying capacitors of low withstand voltage. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a power supply device for converting a constant AC power supply to a DC having a desired voltage.
[0002]
[Prior art]
A power supply device used for an electric device such as an air conditioner needs to clear the harmonic regulation. One means for clearing the harmonic regulation is as follows.
[0003]
FIG. 4 shows a configuration of a conventional power supply device.
[0004]
In the figure, an AC power supply 1 is connected via a reactor 3 to an input terminal (middle point of each half bridge) of a rectifier circuit 2 composed of two sets of diode half bridges, and is further connected in series with a capacitor for voltage doubler rectification. 4 and a capacitor 5 are connected to the output terminal of the rectifier circuit 2.
[0005]
The switch SW11 is connected between the input terminals of the rectifier circuit 2, and the switch SW12 is connected between one of the input terminals of the rectifier circuit 2 and a connection point between the capacitor 4 and the capacitor 5 for voltage doubling.
[0006]
In this power supply device, full-wave rectification and voltage doubler rectification are switched by turning on / off the switch SW12, and the pulse width (PWM) is controlled by turning on / off the switch SW11, thereby realizing a power factor improvement and boosting function. The variable range of the output voltage is expanded.
[0007]
That is, when the voltage value required by the load is small, the switch SW12 is turned off to operate in the full-wave rectification mode, and when the voltage value required by the load is large, the switch SW12 is turned on to operate in the double voltage rectification mode. Thus, the variable range of the output voltage is expanded (for example, see Patent Document 1).
[0008]
[Patent Document 1]
JP 2000-188867 A
[Problems to be solved by the invention]
However, the conventional power supply device shown in FIG. 4 has the following problem.
[0010]
That is, when the power is turned on while the switch SW12 is on, or when the switch SW12 is turned on immediately after the power is turned on, the AC power supply 1-the reactor 3-the diode constituting the rectifier circuit 2-the capacitor 4 for voltage rectification. -Switch SW12-path of AC power supply 1 (path 1), and AC power supply 1-switch SW12-capacitor for voltage doubler rectification 5-diode constituting rectifier circuit 2-reactor 3-path of AC power supply 1 (path 2). Thus, charging currents of the voltage doubler rectifying capacitor 4 and the voltage doubler rectifying capacitor 5 respectively flow.
[0011]
The current energy accumulated in the reactor 3 by this charging current is supplied to the voltage doubler rectifying capacitor 4 and the voltage doubler rectifying capacitor 5, respectively, and the voltage across each capacitor rises.
[0012]
FIG. 5 shows the waveforms of the power supply voltage, the current flowing through the reactor 3 (input current), the voltage between the terminals of the capacitors 4 and 5, and the output voltage (the voltage across the capacitors 4 and 5) when the power is turned on. The figure shows an example in which the voltage of the AC power supply 1 is 115 V in consideration of a power supply voltage variation of + 15% of a power supply device used for an electric device such as an air conditioner in which the AC power supply is 100 V.
[0013]
As shown in the drawing, when the power supply voltage is positive, the voltage between the terminals of the capacitor 4 increases due to the current flowing to the reactor 3 in the above (path 1), and when the power supply voltage becomes negative after half a cycle, In 2), the current flowing through the reactor 3 causes the voltage between the terminals of the capacitor 5 to rise, the peak voltage of each of them exceeds 200 V, and the peak voltage of the output voltage that becomes the combined voltage exceeds 400 V.
[0014]
As described above, the withstand voltage of the capacitor for voltage doubler rectification is determined by the withstand voltage required at the time of turning on the power, and a withstand voltage higher than that required during normal operation is required, resulting in an increase in cost.
[0015]
An object of the present invention is to solve the above-mentioned problem, and an object of the present invention is to provide a power supply device that satisfies harmonic regulation with a simple configuration at a low cost.
[0016]
[Means for Solving the Problems]
A power supply device according to the present invention has two input terminals and two output terminals and is connected to an AC power supply via a reactor to convert an AC power supply voltage to a DC voltage. And a plurality of voltage doubler rectifying capacitors connected in series with each other, a capacitor circuit connected between two output terminals of the rectifier circuit, one input terminal of the rectifier circuit, and A first switch means connected between one connection point between the capacitors, and a second switch connected between the other input terminal of the rectifier circuit and the connection point between the capacitors in the capacitor circuit. Switch means, and control means for controlling the opening and closing of the first and second switch means, and switch-on prohibition means for prohibiting the first and second switch means from being turned on for a certain period of time after power-on. It is obtained by the following withstand voltage required for normal voltage doubler rectifier capacitor withstand voltage of the capacitor.
[0017]
With this configuration, the voltage applied to the capacitor can be reduced, and the power supply device can be configured with a capacitor having a low withstand voltage.
[0018]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0019]
(Embodiment)
FIG. 1 is a diagram schematically showing a circuit configuration of a power supply device according to the present invention.
[0020]
As shown in FIG. 1, an AC power supply 1 is connected via a reactor 3 to an input terminal (middle point of each half bridge) of a rectifier circuit 2 composed of two sets of diode half bridges, and is further connected in series. The capacitors 4 and 5 for voltage rectification are connected to the output terminal of the rectifier circuit 2.
[0021]
The switches SW1 and SW2 are connected between the respective input terminals of the rectifier circuit 2 and the connection points between the capacitors 4 and 5, respectively.
[0022]
Reference numeral 6 denotes a control device for controlling the pulse width of the switch SW1 and controlling ON / OFF of the switch SW2. Reference numeral 7 outputs a control signal to the control device 6 so as to inhibit the switches SW1 and SW2 from being turned on for a certain time after the power is turned on. Switch-on prohibition means.
[0023]
The power supply rectifies the voltage from the AC power supply 1 and outputs a DC voltage of a magnitude required by the load 8.
[0024]
The load 8 includes a compressor of an air conditioner, an inverter for driving a DC motor, and the like.
[0025]
The power supply device configured as described above can control the output voltage by controlling ON / OFF of the switches SW1 and SW2 by the control device 6.
[0026]
For example, if the pulse width of the switch SW1 is controlled while the switch SW2 is constantly turned off, the power supply voltage is √2 times when the duty of the switch SW1 is 0%, and the voltage doubler is rectified when the duty is 100%. The output voltage is about 2√2 times the power supply voltage, and an output voltage in the range of √2 times to about 2√2 times the power supply voltage can be obtained by controlling the pulse width of the switch SW1.
[0027]
On the other hand, when the switch SW2 is controlled to be always on, the circuit configuration is based on the voltage doubler rectifier circuit.
[0028]
When the pulse width of the switch SW1 is controlled in this state, when the switch SW1 is on, a short-circuit current flows through the path of the AC power supply 1-reactor 3-switch SW1-switch SW2, and current energy is accumulated in the reactor 3.
[0029]
When the switch SW1 is turned off, the current energy accumulated in the reactor 3 is supplied to the voltage doubler rectifying capacitors 4 and 5, the output voltage increases, and an output voltage of 2√2 or more of the power supply voltage can be obtained. .
[0030]
FIG. 2 is a diagram showing respective waveforms of a power supply voltage, an input current, an output voltage, and a voltage at a connection point of the capacitors 4 and 5 when the switch SW1 is pulse width controlled and the switch SW2 is constantly turned off. In this case, control is performed such that an ON signal is output from the control device 6 to the switch SW1 once every half cycle of the power supply voltage.
[0031]
As shown in the figure, the input current starts flowing when the power supply voltage becomes equal to or higher than the midpoint voltage of the capacitors 4 and 5 by the control pulse of the switch SW1.
[0032]
That is, during the period A, the input current can be made extra conductive, and the power factor can be improved because the current conduction period can be extended in this way.
[0033]
Further, since the waveform of the input current can be made close to the waveform of the power supply voltage, high-frequency regulation can be cleared.
[0034]
Similarly, when the switch SW2 is constantly turned on, the current conduction period can be extended by the control pulse of the switch SW1, and the input current waveform can be made closer to the power supply voltage waveform, so that the power factor is improved and the high-frequency regulation is cleared. Becomes possible.
[0035]
Next, the operation when the power is turned on will be described.
[0036]
In FIG. 1, the switch SW1 and the switch SW2 are controlled by the control device 6 and the switch-on prohibiting means 7 so as not to be turned on for a certain period of time after power-on.
[0037]
When the power is turned on, the AC power supply 1-the reactor 3-the diode constituting the rectifier circuit 2-the capacitor for voltage doubler rectification 4-the capacitor for voltage doubler rectification 5-another diode constituting the rectifier circuit 2-the AC power supply 1 The charging current of the capacitors 4 and 5 connected in series through the path flows.
[0038]
The current energy accumulated in the reactor 3 due to the charging current is supplied to a series circuit of the capacitors 4 and 5, and the output voltage, which is the voltage between both ends, increases.
[0039]
FIG. 3 shows the waveforms of the power supply voltage, the current flowing through the reactor 3 (input current), the voltage between the terminals of the capacitors 4 and 5, and the output voltage (the voltage across the capacitors 4 and 5) when the power is turned on. FIG. 3 is an example in the case where the voltage of the AC power supply 1 is 115V.
[0040]
As shown in the figure, immediately after the power is turned on, the output voltage increases due to the current flowing to the reactor 3, and its peak voltage is about 260V.
[0041]
At this time, the voltage between the terminals of the capacitor 4 and the capacitor 5 is about 1/2 of the output voltage, and the peak voltage is about 130V.
[0042]
Therefore, the withstand voltage of the capacitor 4 and the capacitor 5 only needs to be 130 V or more. However, as described in the conventional example, the pulse width of the switch SW1 is controlled in the voltage doubler rectification mode in which the switch SW2 is always turned on. When the output voltage is increased, the withstand voltage of each capacitor is required to be about 180 V, so that the withstand voltage of the capacitor is about 180 V.
[0043]
On the other hand, when the switches SW1 and SW2 are not driven only for a certain period of time after the power is turned on and the switches SW1 and SW2 are turned on after that, the charging current does not flow because the capacitors 4 and 5 are charged, The output voltage is not boosted.
[0044]
As described above, when the power is turned on, the control device 6 and the switch-on prohibiting means 7 control the switches SW1 and SW2 to be turned off for a certain period of time, so that the voltage applied to the capacitor when the power is turned on can be reduced. In the conventional example, a withstand voltage of about 200 V or more was required, but a withstand voltage of 180 V can be used.
[0045]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the power supply device of this invention, while realizing a power factor improvement and a boosting function, and having a wide range of output voltage, a capacitor for voltage doubler rectification requires a withstand voltage of a capacitor for normal voltage doubler rectification. It can be constituted by one having a withstand voltage or less, and the cost can be reduced.
[Brief description of the drawings]
FIG. 1 is a circuit configuration diagram of a power supply device of the present invention. FIG. 2 is a diagram showing a switch operation and various waveforms (waveforms of a power supply voltage, an output voltage, an input current, etc.) during a normal operation of the power supply device of the present invention. Switch operation and various waveforms (waveforms of power supply voltage, output voltage, input current, etc.) at power-on of the power supply device of the present invention. FIG. 4 is a circuit configuration diagram of a conventional power supply device. FIG. Various waveforms at power-on (waveforms of power supply voltage, output voltage, input current, etc.)
REFERENCE SIGNS LIST 1 AC power supply 2 Rectifier circuit 3 Reactor 4, 5 Capacitor 6 Controller 7 Switch-on prohibiting means 8 Load SW1, SW2 Switch

Claims (1)

A rectifier circuit having two input terminals and two output terminals, connected to an AC power supply via a reactor to convert an AC power supply voltage to a DC voltage, and a plurality of voltage doubler rectifying capacitors connected in series to each other A rectifier circuit connected between two output terminals of the rectifier circuit, one input terminal of the rectifier circuit, and a second terminal connected between one connection point between capacitors in the capacitor circuit. A first switch means, a second switch means connected between the other input terminal of the rectifier circuit and the connection point between the capacitors in the capacitor circuit, and a first switch means and a second switch means. Control means for controlling the opening and closing; switch-on prohibition means for prohibiting the first and second switch means from being turned on for a certain period of time after power is turned on; Power supply being characterized in that not more than the withstand voltage that is required capacitor.

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