JP2008125310A - Switching power supply - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the size and the cost of an input filter in a high power factor switching power supply (PFC), and to reduce a total loss of the power supply caused by a current. <P>SOLUTION: The switching power supply controls high frequency components of an AC current on the output side of a high band blocking filter to flow with timing shifted by adding another pair of two series switch elements and a current detection element and a boosting choke to the output of a DC output smoothing capacitor and the high band blocking filter. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an improvement of a high power factor type switching power supply (hereinafter referred to as PFC) using an AC power supply as an input.

As a conventional PFC, there are circuit systems as shown in FIGS.
FIG. 2 shows two switch elements connected in series vertically (hereinafter referred to as an arm), and FIG. 3 shows two switch elements arranged horizontally.

  In the circuit of FIG. 2, the lower switch element Q2 performs a switching operation when the input voltage is positive, and the upper switch element Q1 performs a switching operation when the input voltage is negative. In the circuit of FIG. 3, the two switch elements Q1 and Q2 perform the switching operation at the same timing.

  The operation principle of the circuits of FIGS. 2 and 3 is almost the same, but the control circuit can be simplified in the circuit system of FIG. 3 compared to the circuit system of FIG. 2 requires a power supply insulated from the ground for the drive circuit of the switch element on the upper side of the arm, but the circuit system of FIG. 3 can share one side of the two switch elements with the ground. Therefore, the drive circuit can be simplified. For this reason, the circuit system shown in FIG. 3 that can reduce the cost is often employed.

  In the circuit systems of FIGS. 2 and 3, in order to reduce the size of the high-frequency blocking filter, it is necessary to increase the switching frequency or increase the size of the boost choke in order to reduce the high frequency component of the input current. When the switching frequency is increased, there is a problem that efficiency is lowered due to switching loss, and an increase in the size of the boosting choke has a problem that the apparatus is increased in size and cost.

  Further, in the circuit system shown in FIG. 3 in which many examples are adopted, there is a problem that it is difficult to control the high frequency component of the current so that it flows at a shifted timing (hereinafter referred to as a linterleave system).

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a switch power supply apparatus in which the circuit system shown in FIG.

  In order to achieve the above-described object, the present invention is a converter that takes an AC power supply as an input and outputs a DC voltage. A current detection element and a boost choke are connected in series to the AC power supply via a high-frequency blocking filter, and A smoothing capacitor is connected to the positive and negative electrodes of the voltage output, two series switch elements are connected in parallel to the smoothing capacitor, two series diodes are connected in parallel to the smoothing capacitor, and the high-frequency blocking filter is connected to the smoothing capacitor. An AC power source, a current detection element, and a boost choke connected in series are connected between the two series switch elements and between the two series diodes, and the AC power source via the high-frequency blocking filter. In the switching power supply apparatus in which the two switch elements are controlled so that the current waveform of the DC current is sinusoidal, the DC output smoothing capacitor and the high-frequency blocking By adding another pair of two series switch elements, a current detection element, and a boost choke to the output of the filter, control is performed so that the high-frequency component of the AC current on the output side of the high-frequency blocking filter flows at a time offset. It is characterized by doing.

  According to the present invention, it is possible to reduce the size and cost of the high-frequency blocking filter, and to reduce the loss caused by the current flowing through the switch element and the boost choke.

FIG. 1 shows a circuit diagram for carrying out the present invention.
The AC power source 1 is connected to two pairs of current detection elements 3 and a boost choke 4 through a high-frequency blocking filter 2. The step-up choke 4 is connected to an intermediate point between two pairs of arms, and the two pairs of arms are connected in parallel to a smoothing capacitor 7 connected to a DC output.

  The other end of the high-pass blocking filter 2 is connected to the midpoint of two rectifier diodes 6 connected in series. Two rectifier diodes 6 connected in series are connected in parallel to the smoothing capacitor 7. An electrical load 8 is connected to the smoothing capacitor 7 connected to the DC output.

  The DC output voltage is amplified and integrated by the error amplifier 9 with respect to the voltage error from the reference voltage Vref18, and the multiplier 10 multiplies the input voltage by the full-wave rectified signal to output a current reference signal Iref. The current reference signal Iref is a signal common to the two arms, and the currents of the two boost chokes 4 are controlled so as to follow the Iref.

  Therefore, in the subsequent control, the full-wave rectified signal of the input currents Iin1 and Iin2 detected by the current detection element 3 and the current reference signal Iref are amplified and integrated by the error amplifier 9 for each arm. The signal of the error amplifier 9 of two currents is made. The signal of the two current error amplifiers 9 is PWM-modulated by the comparator 12 by the sawtooth wave oscillator 14 and the sawtooth wave oscillator 15 whose phase is shifted by 180 °.

  When the input voltage is positive, the switching element 5 on the lower side of the arm is switched, and when the input voltage is negative, the switching element 5 on the upper side of the arm is switched.

  In addition, even if the waveform shape of the sawtooth wave oscillator is a triangular wave, it operates without any problem.

  FIG. 4 shows a circuit diagram when the rectifier diode 6 is replaced with the switch element 5 in the present invention. When the input voltage is positive, the switch element 5 on the lower side of the arm is turned on, and when the input voltage is negative, the switch element 5 on the upper side of the arm is turned on. Since a total of six switch elements 5 have the same configuration as the connection of a three-phase full bridge, there is an advantage that a three-phase bridge module can be used as it is.

It is a circuit diagram which shows the switching power supply device which concerns on embodiment of this invention. FIG. 6 is a circuit diagram of a conventional switching power supply device, which is a PFC in which two switch elements are connected in series vertically. FIG. 6 is a circuit diagram of a conventional switching power supply device and a PFC in which two switch elements are arranged horizontally. FIG. 5 is a circuit diagram of a switching power supply device according to another embodiment of the present invention, in which the rectifier diode 6 of FIG. FIG. 2 is a diagram showing a ripple current waveform of a boost choke when the switching frequency is lowered in the circuit system of FIG. 1. It is a figure which shows the current waveform of the pressure | voltage rise choke in the conventional circuit system of FIG.2 and FIG.3.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 AC power supply 2 High frequency block filter 3 Current detection element 4 Boost choke 5 Switch element 6 Rectifier diode 7 Smoothing capacitor 8 Electrical load 9 Error amplifier 10 Multiplication circuit 11 Absolute value calculation circuit 12 Comparator 13 NOT logic circuit 14 Saw wave oscillator 15 sawtooth wave oscillator 16 with phase shifted by 180 ° from sawtooth wave oscillator 14 AND logic circuit 17 differential amplifier 18 reference voltage Vref

Claims (1)

This converter uses an AC power supply as an input and outputs a DC voltage. A current detection element and a boost choke are connected in series to the AC power supply via a high-frequency blocking filter, and a smoothing capacitor is connected to the positive and negative electrodes of the DC voltage output. Two series switch elements are connected in parallel to the smoothing capacitor, two series diodes are connected in parallel to the smoothing capacitor, and an AC power source, a current detection element, and a boost choke are connected via the high-frequency blocking filter. Those connected in series are connected between the two series switch elements and between the two series diodes, and the current waveform of the AC power source is made sinusoidal via the high-frequency blocking filter. In a switching power supply in which two switch elements are controlled,
By adding another pair of two series switch elements, a current detection element, and a boosting choke to the output of the DC output smoothing capacitor and the high-frequency blocking filter, an AC current on the output side of the high-frequency blocking filter is obtained. The switching power supply device is characterized in that the high frequency component of the current is controlled so as to flow out of timing.

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