JP2006230135A - Switching regulator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching regulator in which power factor can be improved with small number of components. <P>SOLUTION: A power factor improving circuit (17A) arranged between a full-wave rectifier (12) and an input smoothing capacitor (Ci) improves power factor by superposing a high frequency voltage induced in an auxiliary winding (NB2) coupled magnetically with a transformer (T) on the input power supply voltage of the input smoothing capacitor (Ci). The power factor improving circuit (17A) comprises an inductor (L1) having one end connected with the positive electrode terminal of the full-wave rectifier (12), a diode (D6) connected between the other end of the inductor and the input smoothing capacitor (Ci), and a capacitor (C3) connected between the auxiliary winding (NB2) and the other end of the inductor (L1). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a switching power supply device, and more particularly to a switching power supply device having an improved power factor.

  As is well known in this technical field, switching power supply devices include those using a resonant converter and those using a switching converter. On the other hand, the resonance type converter is classified into a full bridge resonance type converter and a half bridge resonance type converter.

  A switching power supply device using a conventional resonant converter will be described with reference to FIG.

  The AC voltage from the AC power supply 11 is full-wave rectified by a full-wave rectifier 12. The illustrated full-wave rectifier 12 is configured by a diode bridge. The voltage that is full-wave rectified by the full-wave rectifier 12 is smoothed by the input smoothing capacitor Ci, and an input power supply voltage is obtained. That is, the full-wave rectifier 12 and the input smoothing capacitor Ci constitute a DC power source.

  The input power supply voltage is applied to the resonant converter 13. The illustrated resonant converter 13 is a half-bridge resonant converter. The resonant converter 13 includes a series circuit including first and second switches Q1 and Q2 connected between both ends of the smoothing capacitor Ci. Each of the first and second switches Q1 and Q2 includes an N-channel insulated gate field effect transistor (FET). First and second diodes D1 and D2 are connected in reverse direction parallel to the first and second switches Q1 and Q2. The first and second switches Q1, Q2 are collectively referred to as switching means.

  An LC series resonance circuit including a primary winding Np of the transformer T and a resonance capacitor Cr is connected in parallel with the second switch Q2. The LC series resonance circuit is also simply called a resonance circuit. The transformer T has secondary windings NS1 and NS2. One ends of these secondary windings NS1 and NS2 are connected to an output smoothing capacitor Co via first and second output rectifier diodes D3 and D4, respectively. That is, the first and second output rectifying diodes D3 and D4 and the output smoothing capacitor Co constitute an output rectifying and smoothing circuit. The output rectifying / smoothing circuit is also simply called an output circuit. The voltage across the output smoothing capacitor Co is applied to the load 14 as the output power supply voltage.

  A control circuit 15 is connected to the control electrodes (gates) of the first and fourth switches Q1 and Q2. The control circuit 15 is connected to the auxiliary winding NB of the transformer T via a diode D5 and a capacitor C1. That is, the combination of the auxiliary winding NB, the diode D5, and the capacitor C1 serves as an auxiliary power source for supplying power to the control circuit 15. The control circuit 15 controls on / off of the first and second switches Q1, Q2.

  The switching power supply described above has a capacitor input type smoothing circuit Ci. In the switching power supply device having such a configuration, the input current from the AC power supply 11 flows only during the charging period of the input smoothing capacitor Ci, and thus has a pulse shape. Since the pulsed current has a wide frequency band, it includes a harmonic component of the power supply frequency of the AC power supply 11. Therefore, when the AC power supply 11 is a commercial power supply, there is a concern about the influence on other devices and power transmission / distribution equipment connected to the AC power supply 11.

  Therefore, as a method for reducing such harmonic components, a switching power supply having an improved power factor using an active filter circuit is known (see, for example, Patent Document 1).

  FIG. 2 shows a switching power supply with an improved power factor. The illustrated switching power supply has a low-pass filter (LPF) 16 and an active filter 17 inserted between a full-wave rectifier 12 and an input smoothing capacitor Ci. Other configurations are the same as those of the conventional switching power supply shown in FIG. Components having the same functions as those in FIG. 1 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The low-pass filter 16 is composed of only a capacitor C2 connected in parallel between the output terminals of the full-wave rectifier 12.

  The active filter 17 includes an inductor L1, a diode D6, and a switch element SW1. One end of the inductor L1 is connected to the positive output terminal of the full-wave rectifier 12. The diode D6 is inserted between the other end of the inductor L1 and one end (power input terminal) of the input smoothing capacitor Ci. The switch element SW1 is provided between the other end of the inductor L1 and the negative output terminal (ground terminal) of the full-wave rectifier 12. The active filter 17 is also called a boost chopper circuit.

  In the switching power supply device having such a configuration, the switch element SW1 is turned on / off at a frequency higher than the power supply frequency of the AC power supply 11, current is stored in the inductor L1 when the switch element SW1 is turned on, and the inductor L1 is turned on when the switch element SW1 is turned off. The waveform of the input current is approximated to the sine wave of the voltage waveform by repeating the operation of releasing the current stored in the current waveform. Thereby, the power factor can be improved to nearly 1.

  Also known is a switching power supply device that improves the power factor by generating a DC voltage source using a switching power supply circuit to compensate for the voltage drop portion of the pulsating voltage obtained by rectifying the AC power supply (for example, Patent Document 2).

Japanese Patent Laid-Open No. 7-15967 (FIG. 9) JP-A-2-254947

  However, the conventional switching power supply device with improved power factor shown in FIG. 2 requires a dedicated switch element SW1 and a drive circuit for driving the switch element SW1. As a result, there is a problem that the number of parts increases and the cost becomes high. Note that the prior art disclosed in Patent Document 2 merely discloses a method of deforming an input current waveform, unlike a method of superimposing a high frequency.

  Therefore, the subject of this invention is providing the switching power supply device which can improve a power factor with few components.

  According to the present invention, the rectifying means (12) that outputs a voltage obtained by rectifying and rectifying the AC voltage from the AC power supply (11), and the input smoothing capacitor that outputs the input power supply voltage by smoothing the rectified voltage. Ci) and a converter to which the input power supply voltage is applied, the switching power supply comprising the converter (13, 13A) including switching means (Q1, Q2; 21) and a transformer (T) The high frequency voltage induced between the rectifying means and the input smoothing capacitor and induced in the auxiliary winding (NB; NB2) magnetically coupled to the transformer is used as the input power supply voltage of the input smoothing capacitor. A switching power supply device characterized by including a power factor correction circuit (17A; 17B) that superimposes and improves the power factor is obtained.

  In the switching power supply device, the power factor correction circuit (17A; 17B) includes, for example, an inductor (L1) having one end connected to a positive terminal of the rectifier, and the other end of the inductor and the input smoothing capacitor. It may be composed of a diode (D6) connected in between and a capacitor (C3) connected between the auxiliary winding and the other end of the inductor. Moreover, it is preferable that the said switching power supply device further has a low pass filter (16) provided between the said rectification means and the said power factor improvement circuit. The low-pass filter (16) may be composed of, for example, a capacitor (C2) connected in parallel between the output terminals of the rectifying means. The auxiliary winding may be an auxiliary winding (NB) for supplying power to a control circuit (15; 15A) that controls on / off of the switching means. The converter may be a resonant converter (13) or a switching converter (13A).

  In addition, the code | symbol in the said parenthesis is attached | subjected in order to make an understanding of this invention easy, and it is only an example, and of course is not limited to these.

  In the present invention, the power factor correction circuit disposed between the rectifying means and the input smoothing capacitor superimposes the high frequency voltage induced in the auxiliary winding magnetically coupled to the transformer on the input power supply voltage of the input smoothing capacitor. In addition, since the power factor is improved, a dedicated switch element and a drive circuit for driving the power switch which are necessary in the past are unnecessary, and the power factor improving circuit can be configured with a small number of components. .

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  With reference to FIG. 3, the switching power supply device according to the first embodiment of the present invention will be described. The illustrated switching power supply device operates with the same configuration as the switching power supply device shown in FIG. 2 except that a power factor correction circuit 17A is provided instead of the active filter 17. Accordingly, components having the same functions as those shown in FIG. 2 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The power factor correction circuit 17A is also called a PFC (power factor correction) circuit. The power factor correction circuit 17A is shown in FIG. 2 except that instead of the switch element SW1, a combination of the second auxiliary winding NB2 magnetically coupled to the transformer T and the capacitor C3 is used. The active filter circuit 17 has the same configuration.

  That is, the second auxiliary winding NB2 is connected to the connection point between the inductor L1 and the diode D6 via the capacitor C3.

  In the switching power supply having such a configuration, a high frequency voltage induced in the second auxiliary winding NB2 is applied to the inductor L1 via the capacitor C3. As a result, a high frequency potential difference can be superimposed on the inductor L1, and a high frequency can be superimposed on the input power supply voltage of the input smoothing capacitor Ci. As a result, the conduction angle of the pulsed input current can be expanded, and the power factor of the present switching power supply device can be improved. The superposed high frequency component is removed by the low pass filter 16.

  The active filter circuit 17 used in the switching power supply device shown in FIG. 2 requires a dedicated switch element SW1 and its drive circuit, but the power factor correction circuit 17A used in the switching power supply device is as described above. Since no circuit components are required, it can be configured with a small number of components.

  A switching power supply device according to a second embodiment of the present invention will be described with reference to FIG. The illustrated switching power supply device operates with the same configuration as the switching power supply device shown in FIG. 3 except that the power factor correction circuit is changed as described later. Accordingly, the reference numeral 17B is assigned to the power factor correction circuit. Also, components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The power factor improvement circuit 17B shown in the figure is the power factor improvement circuit shown in FIG. 3 except that the auxiliary winding NB used for supplying power to the control circuit 15 is shared as an auxiliary winding. It has the same configuration as 17A.

  In the switching power supply having such a configuration, since the auxiliary winding NB is shared by the power factor correction circuit 17B and the control circuit 15, the number of parts can be reduced as compared with that of FIG.

  In the switching power supply according to the first and second embodiments of the present invention, the resonant converter 13 is used as a converter. However, the converter is not limited to the resonant converter 13, and a transformer T is used. It can also be applied to converters.

  With reference to FIG. 5, a switching power supply device according to a third embodiment of the present invention will be described. The illustrated switching power supply device operates with the same configuration as the switching power supply device shown in FIG. 3 except that a switching converter 13A is used instead of the resonant converter 13 as a converter. Components having the same functions as those shown in FIG. 3 are denoted by the same reference numerals, and description thereof is omitted for the sake of simplicity.

  The illustrated switching converter 13A includes a switching circuit 21 in place of the first and second switches Q1, Q2, the first and second diodes D1, D2, and the resonance capacitor Cr, and includes the first and second switches Except for the point that the rectifier circuit 22 is provided instead of the output rectifier diodes D3 and D4, it has the same configuration as the resonant converter 13 shown in FIG.

  The switching power supply device having such a configuration also has an effect that the power factor correction circuit 17A can be configured with a small number of components, similarly to the switching power supply device shown in FIG.

  The switching power supply device shown in FIG. 5 is also configured so that the auxiliary winding is shared by the power factor improvement circuit and the control circuit, similarly to the power factor improvement circuit 17B of the switching power supply device shown in FIG. Of course, it may be.

  Although the present invention has been described above with reference to preferred embodiments, it is needless to say that the present invention is not limited to the above-described embodiments. For example, in the above-described embodiment, the low-pass filter 16 is composed of only the capacitor C2, but it goes without saying that various configurations of low-pass filters combining capacitors and inductors may be used. . In the above-described embodiment, the full-wave rectifier 12 is used as the rectifier on the input side, but rectification means other than the full-wave rectifier may be used. The resonant converter is not limited to a half-bulge resonant converter, and may be a full bridge resonant converter. The present invention can also be applied to a converter including a transformer as the converter.

It is a block diagram which shows the structure of the conventional switching power supply apparatus. It is a block diagram which shows the structure of the conventional switching power supply device which improved the power factor. It is a block diagram which shows the structure of the switching power supply device which concerns on the 1st Embodiment of this invention. It is a block diagram which shows the structure of the switching power supply device which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the structure of the switching power supply device which concerns on the 3rd Embodiment of this invention.

Explanation of symbols

11 AC power supply 12 Full wave rectifier (diode bridge)
DESCRIPTION OF SYMBOLS 13 Resonant type converter 13A Switching converter 14 Load 15 Control circuit 16 Low pass filter (LPF)
17A, 17B Power factor correction circuit (PFC circuit)
Ci input smoothing capacitor L1 inductor D6 diode C2, C3 capacitor NB auxiliary winding NB2 second auxiliary winding

Claims (7)

Rectifying means for rectifying an AC voltage from an AC power supply and outputting a rectified voltage, an input smoothing capacitor for smoothing the rectified voltage and outputting an input power supply voltage, and a converter to which the input power supply voltage is applied. In the switching power supply device comprising the converter including the switching means and the transformer,
A power factor is superimposed between the input power supply voltage of the input smoothing capacitor by superimposing a high-frequency voltage induced between the rectifying means and the input smoothing capacitor and induced in an auxiliary winding magnetically coupled to the transformer. A switching power supply comprising a power factor correction circuit for improving the power.   The power factor correction circuit includes an inductor having one end connected to the positive terminal of the rectifier, a diode connected between the other end of the inductor and the input smoothing capacitor, the auxiliary winding, and the inductor. The switching power supply device according to claim 1, further comprising a capacitor connected between the other end.   The switching power supply device according to claim 1, further comprising a low-pass filter provided between the rectifier and the power factor correction circuit.   4. The switching power supply device according to claim 3, wherein the low-pass filter includes a capacitor connected in parallel between output terminals of the rectifying means.   The switching power supply according to claim 1, wherein the auxiliary winding is an auxiliary winding for supplying power to a control circuit that controls on / off of the switching means.   The switching power supply device according to any one of claims 1 to 5, wherein the converter is a resonant converter. The switching power supply device according to any one of claims 1 to 5, wherein the converter is a switching converter.

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