JP3125862B2 - Switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type switching power supply capable of improving a power factor.

[0002]

2. Description of the Related Art A typical resonance type switching power supply device includes a circuit for rectifying and smoothing a commercial AC voltage, and a DC-DC conversion circuit connected to the rectifying and smoothing circuit. If the rectifying and smoothing circuit is formed only by the diode bridge circuit and the smoothing capacitor, the charging current of the smoothing capacitor flows only at the peak value of the sine wave AC voltage and the vicinity thereof, and the waveform of the input current of the rectifying circuit becomes And the power factor worsens. This kind of problem can be solved to some extent by configuring a choke input type filter circuit by connecting a reactor (choke coil) between a rectifier circuit and a smoothing capacitor.

[0003]

However, when a choke input type filter circuit is provided, a voltage drop occurs due to the resistance of the reactor according to the magnitude of the load current, and the output voltage of the smoothing capacitor is reduced. This disadvantage can be solved by providing a dedicated input current waveform improving circuit or power factor improving circuit. However, providing a dedicated input current waveform improving circuit inevitably increases the cost of the switching power supply. Therefore, the applicant of the present application has tried to improve the waveform of the input current and the power factor by also using the DC-DC conversion circuit as shown in FIG. Hereinafter, the switching power supply device of FIG. 1 will be described in detail. In the switching power supply of FIG. 1, for example, first, second, third and fourth rectifier diodes Db1, Db2 are connected to first and second AC power supply terminals 12, 13 to which a 50 Hz commercial AC power supply 11 is connected. ,
A bridge rectifier circuit 14 composed of Db3 and Db4 is connected. That is, in order to form a full-wave rectifier circuit, the anode of the first rectifier diode Db1 and the third rectifier diode Db3
(First input terminal) 15 is connected to one AC power supply terminal 12 and the second rectifier diode D
The connection point (second input terminal) 16 between the anode of b2 and the cathode of the fourth rectifier diode Db4 is connected to the other AC power supply terminal 1
3 is connected. First and second rectifier diodes D
The cathodes (first output terminals) of b1 and Db2 are connected to one DC power supply line 17, and the anodes (second output terminals) of the third and fourth rectifier diodes Db3 and Db4 are connected to the other DC power supply line 18 It is connected to the.

[0004] An input smoothing capacitor Ci is connected between the pair of DC power supply lines 17 and 18, ie, between the first and second DC output terminals of the bridge rectifier circuit. This input smoothing capacitor Ci is connected to a current resonance capacitor C described later.
r and the first and second auxiliary capacitors Cf and Cp have larger capacitances. First and second FETs (field effect transistors) Q1 as first and second switches for turning on / off the DC voltage of the input smoothing capacitor Ci.
, Q2 are connected in parallel to the input smoothing capacitor Ci. First and second FETs Q1, Q
Reference numeral 2 denotes an insulated gate field effect transistor having a source connected to the substrate, which has drain-source switches S1 and S2, and switches S1 and S2.
It has built-in diodes D1 and D2 connected in parallel with S2. The built-in diodes D1 and D2 have a direction in which a current flows in a direction opposite to the drain current. First and second F
A voltage resonance capacitor Cq2 is connected in parallel with the second FET Q2 in order to slow the rise of the voltage when the ETQ1 and Q2 are turned off. The capacitance of the voltage resonance capacitor Cq2 is of course smaller than the capacitance of the input smoothing capacitor Ci.

A series circuit of a primary winding N1 having an inductance of a transformer 20 and a current resonance capacitor Cr is provided between a connection point 19 of the first and second FETs Q1 and Q2 and the DC power supply line 18 on the ground side. It is connected. Transformer 20 includes first and second secondary windings electromagnetically coupled to primary winding N1 by magnetic core 21 in addition to primary winding N1.
It has secondary windings N2a and N2b. One end of the first secondary winding N2a is connected to one end of an output smoothing capacitor Co via a first output rectifying diode Do1, and the other end of the first secondary winding N2a is connected to the output smoothing capacitor Co. Connected to the other end. One end of the second secondary winding N2b is connected to one end of an output smoothing capacitor Co via a second output rectifier diode Do2, and the other end of the second secondary winding N2b is connected to an output smoothing capacitor Co. Is connected to the other end. The polarities of the primary winding N1 and the first and second secondary windings N2a and N2b are set as indicated by black circles. Accordingly, when a voltage in the first direction (downward) is applied to the primary winding N1, a voltage is induced in the first secondary winding N2a in a direction for forward-biasing the first output rectifier diode Do1, A voltage is induced in the second secondary winding N2b to reverse bias the second output rectifier diode Do2. A load 24 is connected between a pair of output terminals 22 and 23 connected to the output smoothing capacitor Co.

The control circuit 25 includes first and second FETs Q1
, Q2 are alternately turned on and off, and a pair of output voltage detection lines 26 and 27 are used to control the output terminal 2
2 and 23 and to the gates of the first and second FETs Q1 and Q2 by lines 28 and 29. The control circuit 25 includes an error amplifier 30, a reference voltage source 31, a VCO (voltage controlled oscillator) 32, and a control signal forming circuit 33, as shown in detail in FIG. One input terminal of the error amplifier 30 is connected to the output terminal 22 by a line 26 and the other input terminal is connected to the reference voltage source 3.
1 and this output terminal is connected to the VCO 32. This error amplifier 30 is connected to the output voltage detection line 26,
A voltage corresponding to the difference between the voltage detected at 27 and the reference voltage of the reference voltage source 31 is output. VCO 32 is an error amplifier 3
A frequency signal is output in response to an output voltage of 0. This V
The frequency signal of the CO 32 becomes higher when the detection voltage of the lines 26 and 27 becomes higher than the reference voltage, and becomes lower when the detection voltage becomes lower than the reference voltage. VCO3
The control signal forming circuit 33 connected to the second FE 2 shapes the output waveform of the VCO 32 with a comparator and outputs the first and second FEs.
The first and second control signals Vg1 and Vg2 of square waves for controlling TQ1 and Q2 are formed as shown in FIGS. 6A and 6B. Note that the first and second control signals Vg
1 and Vg2 are in the opposite phase to each other, and alternately enter the ON period with a slight dead time (pause period). The center frequency of the first and second control signals Vg1 and Vg2 is
Has a value (for example, 20 kHz) sufficiently higher than the frequency of the power supply voltage (for example, 50 Hz). The pulse width of the first and second control signals Vg1 and Vg2 during the ON period is equal to the primary winding N.
The length is set to be longer than the half-wave of the resonance waveform between the inductance Lr and the capacitor Cr.

The switching power supply shown in FIG. 1 is obtained by adding first and second auxiliary capacitors Cf and Cp and a diode D3 to a general resonance type switching power supply. The first auxiliary capacitor Cf is connected between a cathode of the third and fourth rectifier diodes Db3 and Db4, that is, a point on the output side of the reactor L of the lower power supply line 18 and the primary winding N1.
And the interconnection point 34 of the resonance capacitor Cr. The second auxiliary capacitor Cp is connected between a point on the output side of the power line 18 with respect to the reactor L and the lower end of the resonance capacitor Cr. Diode D
3 is connected between the lower end of the smoothing capacitor Ci and the reactor L, and is connected in parallel to the second auxiliary capacitor Cp.

[0008]

[Outline of operation] In the switching power supply of FIG.
When the first and second FETs Q1 and Q2 are turned on and off,
The DC voltage Vci of the input smoothing capacitor Ci is interrupted. The primary winding N1 of the transformer 20 has a leakage inductance Lr inserted in series with the primary winding N1 and an exciting inductance Lp inserted in parallel with the primary winding N1, as shown equivalently in FIG. The first and second F are applied to the series resonance circuit including the leakage inductance Lr and the resonance capacitor Cr.
When a voltage interrupted by ETQ1 and Q2 is applied, a resonance current flows. In the resonant switching power supply, zero voltage switching (ZVS) and zero voltage switching (ZCS) are achieved when the first and second FETs Q1 and Q2 are turned on, and zero voltage switching (ZVS) is achieved when the first and second FETs Q1 and Q2 are turned off. Loss is reduced. By the way, since the switching power supply of FIG. 1 has the reactor L, the rush current of the input smoothing capacitor Ci is prevented, and the waveform of the input current and the power factor are improved. As described above, when the reactor L is provided, the voltage drop due to the resistance of the reactor L increases as the load current increases, and the output voltage of the input smoothing capacitor Ci decreases. Rectifier circuit 1
4 also causes a voltage drop. In order to solve this disadvantage, the circuit of FIG.
The voltage of r is divided by the first and second auxiliary capacitors Cf and Cp, and the voltage of the second auxiliary capacitor Cp is added to the output voltage of the rectifier circuit 14 as a bias voltage. Since the voltage of the resonance capacitor Cr increases as the load current increases, the voltage of the second auxiliary capacitor Cp, that is, the bias voltage also increases, and the reactor L and the rectifier circuit 1
4 can be compensated for. Also, the bias voltage added by the second auxiliary capacitor Cp is
Since it has a frequency sufficiently higher than the frequency of the AC voltage of the power supply 11, it works to increase the period during which the current flows through the input smoothing capacitor Ci, and the input current waveform and the power factor are improved. FIG. 3 shows in principle the effect of the voltage Vd3 on the diode D3, ie the voltage on the second auxiliary capacitor Cp. The voltage Va obtained from the rectifier circuit 14 is shown in FIG. 3 (A), and when the voltage Vd3 of the diode D3 is added thereto, it becomes FIG. 3 (B).

[0009]

Next, referring to FIG. 5, the first and second Fs during the positive half cycle of the voltage Vin of the AC power supply 11 will be described.
The operation of one cycle of ON / OFF of ETQ1 and Q2 will be described. In FIG. 5, Vg1 and Vg2 are first and second FETs.
Q1 and Q2 control signals, ie, gate-source voltage, VQ
1, VQ2 is the drain-source voltage of the first and second FETs Q1, Q2, and IQ1, IQ2 are the first and second FETs Q1, Q2.
1, Q2 switch sections S1, S2 and diodes D1, D2
, In1 is the current of the primary winding N1, Ido1
, Ido2 are the currents of the output rectifier diodes Do1, Do2, Vc
r is the voltage of the resonance capacitor Cr, Iin is the AC input current, Id3 is the current of the diode D3, and Vd3 is the diode D3.
The voltage of 3 is shown. In FIG. 5, t0 to t11 are one cycle of ON / OFF of the first and second FETs Q1, Q2,
T1 to t6 when Vg1 becomes high level is the ON period of the first FET Q1, and t7 to t11 when Vg2 becomes high level is the second F2.
During the ON period of ETQ2, t0 to t1 and t6 to t7 at which both Vg1 and Vg2 are at low level are dead times. t
The operation of one cycle from 1 to t11 is roughly divided into the first operation from t0 to t1.
, A second period from t1 to t2, a third period from t2 to t3, a fourth period from t3 to t4, a fifth period from t4 to t5, and a sixth period from t5 to t6. And t6 to t7
A seventh period, an eighth period from t7 to t8, and a period from t8 to t8.
9, a ninth period, a tenth period from t9 to t10, and t10
The description will be made separately for the eleventh period from t11. In the following, in order to simplify the description of the current path, the current path is indicated only by the reference numerals of the circuit elements.

[0010]

[Period from t0 to t1] Immediately before t0, the first control signal V
g1 is at a low level, and the second control signal Vg2 is at a high level.
When the second control signal Vg2 changes from a high level to a low level at time t0, the second FET Q2 changes from on to off. For this reason, the current that has been flowing through the second FET Q2 until now is changed by the capacitor C connected in parallel with the second FET Q2.
The current In1 flows through the circuit of N1-Cq2-Cr due to the commutation to q2 and the continuous release of the energy stored in the primary winding N1. Since the voltage of the capacitor Cq2 gradually increases, the voltage VQ2 of the second FET Q2 also gradually increases, and substantially zero volt switching (ZVS) is achieved. Therefore,
The storage of minority carriers causes the second FET Q
Even if the current of 2 flows until after t0, the second FET Q
The power loss (switching loss) at 2 is small. The voltage VQ1 of the first FET Q1 is equal to the voltage VQ of the smoothing capacitor Ci.
ci, the voltage of the voltage resonance capacitor Cq2, that is, the second FE
Since the value is obtained by subtracting the voltage VQ2 of TQ2, t0 to t
In the period 1, the voltage gradually decreases and the voltage resonance capacitor Cq2 becomes equal to the voltage Vci of the input smoothing capacitor Ci.
It becomes zero at that point. Note that there is a parasitic capacitance (stray capacitance) between the drain and source of the first FET Q1, and when this is charged to the voltage Vci of the smoothing capacitor Ci immediately before the time point t0, this charge is released from t0 to t1, This does not result in switching loss of the first FET Q1. By the way, the first and second auxiliary capacitors Cf
, Cp operate in the same manner as the resonance capacitor Cr because they are connected in parallel with the resonance capacitor Cr. That is, during the period from t0 to t1, the discharge of the resonance capacitor Cr, that is, the reverse charging occurs, and the first auxiliary capacitor Cf
Reverse charging occurs in a closed circuit of N1-Cq2-D3-Cf. As a result, the current Id3 shown in FIG. 5H flows through the diode D3. During the period from t0 to t4 when the diode D3 is on, this voltage Vd3, that is, the voltage of the second auxiliary capacitor Cp is substantially zero as shown in FIG. 5 (I), and a substantial bias effect occurs. Absent.

[0011]

[Period from t1 to t2] At time t1, capacitor C for voltage resonance
When the voltage of p2 reaches the voltage Vci of the input smoothing capacitor Ci and the discharge of the energy stored in the primary winding N1 is further continued, the diode D1 of the first FET Q1 is turned on, and N1 -D1 -Ci -Cr1 closed circuit and N1 -D1
A current flows through the closed circuit of -Ci -D3 -Cf. Since a high-level control signal is supplied to the first FET Q1 during the period from t1 to t6 and the first FET Q1 has no directionality, the negative component of the current IQ1 of the first FET Q1 is a diode. It flows through both D1 and switch section S1. The switch section S1 of the first FET Q1 from time t1
Even if current starts to flow through the first FET at time t1,
Since the voltage VQ1 of Q1 is substantially zero, ZV
S is achieved, and the power loss at this time is small. This t1
The period t2 ends when the voltage of the secondary winding N2a becomes equal to the voltage of the output smoothing capacitor Co.

[0012]

[Period from t2 to t3] After the time point t2, the voltage of the secondary winding N2a becomes higher than the voltage of the output smoothing capacitor Co, and the diode Do1 conducts to form a circuit of N2a-Do1-Co. As shown in (E), the current Ido1 of the diode Do1 starts to flow. The operation in the period from t2 to t3 is the same as that in the period from t1 to t2 except that the current Ido1 flows through the diode Do1.

[0013]

[Period from t3 to t4] When the release of the stored energy of the primary winding N1 is completed at the time t3, the current I of the first FET Q1 is reduced.
Q1 also becomes zero, and then the forward current becomes Ci-Q1-N1.
-It flows to the circuit of Cr. As a result, the current Ido1 of the output rectifier diode Do1 also flows following the previous period t2 to t3. During the period from t3 to t4, Ci-Q1-N1-Cf
The current also flows through the circuit of -Cp, and the second auxiliary capacitor C
The voltage of p gradually increases. The period from t3 to t4 ends when the diode D3 is reverse-biased by the voltage of the second auxiliary capacitor Cp and the current Id3 becomes zero.

[0014]

[Period from t4 to t5] After the diode D3 becomes non-conductive at the time t4, current flows to the main circuit of Ci-Q1-N1-Cr and also to the auxiliary circuit of Ci-Q1-N1-Cf-Cp. 5F, the voltage Vcr of the resonance capacitor Cr increases as shown in FIG.
As shown in the figure, the voltage Vcp of the second auxiliary capacitor Cp, that is, the diode voltage Vd3 also increases. The period from t4 to t5 ends when the series resonance of the inductance Lr and the capacitor Cr ends and the output rectifier diode Do1 becomes non-conductive.

[0015]

[Period from t5 to t6] When the half-wave period of the current due to LrCr resonance ends at time t5, the current Ido1 passing through the output rectifier diode Do1 becomes zero, and the output rectifier diode Do
Both 1, Do2 are turned off. However, since the primary winding N1 of the transformer 20 has the exciting inductance Lp,
A low-frequency resonance operation consisting of LpCr occurs, and a current based on this operation flows in a closed circuit of Ci-Q1-N1 (Lp) -Cr. Thus, the voltage Vcr of the resonance capacitor Cr continues to increase even after t5. In addition, t5 to t6
During the period, Ci -Q1 -N1-as in the period from t4 to t5.
A current flows through a closed circuit of Cf-Cp.

[0016]

[Period from t6 to t7] At time t6, the control signal Vg1 of the first FET Q1 changes to a low level, and when the first FET Q1 is turned off, the current Iq1 passing therethrough becomes zero. The first F
The voltage of the difference between the voltage Vci of the input smoothing capacitor Ci and the voltage VQ2 of the voltage resonance capacitor Cq2 is applied to ETQ1. Therefore, the voltage VQ1 of the first FET Q1 does not immediately rise to Vci at t6, but rises with a slope. For this reason, at time t6, the Z
VS is achieved. When the first FET Q1 is turned off at time t6, the current flowing through the exciting inductance Lp of the primary winding N1 is commutated to the voltage resonance capacitor Cq2,
A current flows through the closed circuit of 1 (Lp) -Cr1-Cq2, and the voltage of the capacitor Cq2, that is, the voltage VQ2 of the second FET Q2 gradually decreases, and becomes substantially zero at time t7. This t6
In the period t7, a closed circuit consisting of N1-Cf-Cp-Cq2 is also formed.

[0017]

[Period from t7 to t8] At time t7, capacitor C for voltage resonance
When the voltage of q2 becomes zero and the reverse bias of the diode D2 is released, the current flowing based on the exciting inductance Lp flows through the diode D2. That is, N
A current In1 flows by a closed circuit of 1-Cr1-D2. In the period from t7 to t8, N1 -Cf -Cp -D2
Current also flows through the circuit. At time t7, the second FE
Since the control signal Vg2 of TQ2 goes high, the second F
ETQ2 turns on. Therefore, the negative component (the positive current component of In1) passing through the second FET Q2 is the diode D
2 and the switch section S2. At time t7, the voltage VQ2 of the second FET Q2 is substantially zero, so that the turn-on ZVS is achieved. This t7 ~
The period t8 ends when the voltage of the secondary winding N2b reaches the voltage of the output smoothing capacitor Co.

[0018]

[T8 to t9 period] During the period from t8 to t9, the second FET Q
Although the current flows in the negative direction through the second diode D2, the current Ido2 of the output rectifier diode Do2 flows as shown in FIG. 5 (E). Therefore, t8
The current of each part on the primary side of the transformer 20 during the period from t9 to t9 flows in the same manner as during the period from t7 to t8. This t8 to t
The period 9 ends when the current IQ2 of the second FET Q2 becomes zero.

[0019]

[T9-t10 period] The current In1 passing through the primary winding N1 is t9
When the current becomes zero and the voltage of the current resonance capacitor Cr1 reaches a peak, the discharge of the resonance capacitor Cr1 starts. That is, a closed circuit of Cr1-N1-Q2 is formed, and a negative current of the current In1 flows based on resonance. Also, Cp
A current also flows through the circuit of -Cf -N1 -Q2.

[0020]

[T10-t11 period] When the negative half-wave period of the Lr Cr1 resonance current ends at the time point t10, the transmission of energy via the transformer 20 stops, and the second output rectifier diode D
O2 is turned off, and this current Ido2 becomes zero. However, the current of the low frequency resonance circuit of Lp Cr1 based on the excitation inductance Lp flows in the closed circuit of Cr1-N1 (Lp) -Q2, and the discharge of the resonance capacitor Cr1 continues. Further, a current also flows through the circuit of Cp-Cf-N1-Q2. After the time point t11, the same operation as in the case of t0 to t11 occurs again.

The input smoothing capacitor Ci is also charged during the period from t0 to t11. This input smoothing capacitor Ci is charged by a diode D3 shown in FIG.
Occurs when the sum of the voltage Vd3 of the second auxiliary capacitor Cp and the output voltage of the rectifier circuit 14 becomes higher than the voltage of the input smoothing capacitor Ci. During the period from t0 to t4 when the diode D3 is on during the positive half-wave period, a charging current flows in the circuit of 11-Db1-Ci-D3-L-Db4, and during the period when the diode D3 is off. 11
The charging current flows in the circuit of -Db1-Ci-Cp-L-Db4.

[0022]

[Constant voltage control operation] The amplitude of the voltage of the primary winding N1 of the output transformer 20 is determined by the ON / OFF of the first and second FETs Q1 and Q2.
It changes depending on the off frequency f. FIG. 6 is a circuit diagram of the transformer 20 using the resonance circuit of the leakage inductance Lr and the resonance capacitor Cr1 when the on / off frequency f is changed.
The change of the electric power P supplied to the next side is shown. At a frequency higher than the inherent series resonance frequency f0 determined by Lr and Cr1, F
When the ETs Q1 and Q2 are turned on and off, the supply power P decreases. FIG. 7 explains this. When f shown in the first half of FIG. 7 is low, the voltage Vn1 of the primary winding N1 is reduced.
Is large, but when f shown in the second half is high, the amplitude of the voltage Vn1 decreases. As a result, the control circuit 25 of FIG.
By controlling the on / off frequency f in the range of fa to fb in FIG. 6, voltage control and power control are achieved, and the output voltage can be kept constant.

The voltage Vcr of the resonance capacitor Cr and the second
The voltage Vcp of the auxiliary capacitor Cp changes in the same manner as the voltage Vn1 of the primary winding N1. That is, Vcr and Vcp are low when the load is light and high when the load is heavy. Therefore, when the rectified output voltage is biased by the voltage Vcp of the second auxiliary capacitor Cp, an action of compensating for the voltage drop of the reactor L and the voltage drop of the rectifier circuit 14 is generated. However, in the circuit of FIG. 1, since the bias by the voltage Vcp of the second auxiliary capacitor Cp is not controlled, it is impossible to always supply an appropriate bias voltage. For example, when the load is light, the input smoothing capacitor Ci is not applied. May be too high. Further, the input current waveform and the power factor could not be sufficiently improved.

Therefore, a first object of the present invention is to provide a resonance type switching power supply capable of achieving an input current waveform and a power factor improvement with a simple circuit and narrowing the fluctuation of the voltage of an input smoothing capacitor. It is to provide a device. A second object of the present invention is to provide a resonance type switching power supply device capable of satisfactorily improving an input current waveform and a power factor with a simple circuit.

[0025]

According to the present invention, there is provided an AC power supply having first and second power supply terminals for supplying at least one-phase AC voltage; A rectifier circuit having first and second input terminals connected to two power supply terminals;
And an input smoothing capacitor connected between the output terminals of the first and second input smoothing capacitors.
And a series circuit of a second switch, a capacitor or a parasitic capacitance connected in parallel to the second switch, and a primary winding of a transformer having a resonance inductance connected in parallel to the second switch. A series circuit of a line and a resonance capacitor or a series circuit of a resonance reactor and a primary winding of a transformer and a resonance capacitor; a secondary winding of a transformer electromagnetically coupled to the primary winding; An output rectifying / smoothing circuit connected to the next winding; and a first switch control circuit for alternately turning on and off the first and second switches at an on / off frequency higher than the frequency of the AC voltage. A diode having one end connected to a connection point between the input smoothing capacitor and the second switch, and the other end connected to the second output terminal of the rectifier circuit; A first auxiliary capacitor connected in parallel via the diode with respect capacitors, a second auxiliary capacitor connected in parallel to said diode,
A third switch connected in parallel with the diode;
The third switch is controlled to be turned on at least during a part of a period in which a current flows through the first switch, and is formed so that an on-time width of the third switch can be adjusted. And a second switch control circuit. In addition, it is desirable to provide a reactor as described in claim 2. Further, as shown in claim 3, a diode can be connected instead of the reactor of claim 2. Also, a reactor can be connected in series to the first auxiliary capacitor. Further, a third auxiliary capacitor can be connected in series with the third switch as described in claims 5, 7 and 10. Also, a second auxiliary capacitor can be connected in parallel with the diode of the rectifier circuit as described in claims 6, 8 and 9. It is desirable to control the ON time width of the third switch so that the input current waveform approximates a sine wave. It is desirable to control the on-time width of the third switch so that the voltage of the input smoothing capacitor is made substantially constant. Further, a diode connected in parallel to the second auxiliary capacitor can be omitted. Further, the resonance capacitor can be omitted, and the resonance circuit can be formed only by the first and second auxiliary capacitors.

[0026]

According to the present invention, the voltage obtained by dividing the voltage of the resonance capacitor by the first and second auxiliary capacitors is used as the bias voltage of the rectified output voltage, and the input current is reduced. To improve the waveform and power factor of
A circuit for improving the input current waveform and the power factor can be easily configured. Further, since the third switch is provided to control the ON period, it is possible to control the input current waveform and / or to make the voltage of the input smoothing capacitor constant. According to the second and fourth aspects, the input current waveform and the power factor can be improved satisfactorily. Further, according to the fifth, seventh, and tenth aspects, the control of the third switch is facilitated. According to the fourteenth aspect of the present invention, the first and second auxiliary capacitors function as the main resonance capacitor and also function as the bias voltage supply capacitor, so that the waveform and power factor can be improved with an extremely simple circuit. .

[0027]

First Embodiment Next, a resonance type switching power supply according to a first embodiment will be described with reference to FIGS. However, in FIGS. 8 and 9, substantially the same parts as those in FIGS. 1 and 5 are denoted by the same reference numerals, and description thereof will be omitted.

The switching power supply device shown in FIG.
A third FET Q3 as a switch, a second switch control circuit 34, a current detector 35, and a signal line 3
The configuration is the same as that of FIG. 1 except that 6, 37, 38, 39, and 40 are added. The third FET Q3 comprises the first and second FETs.
Like the FETs Q1 and Q2, a diode D3 is incorporated in addition to the switch S3. This third FET Q3
The built-in diode D3 has the same function as the diode D3 in FIG. 1, and can be replaced with an individual diode. The third FET Q3 is connected in parallel to the second auxiliary capacitor Cp. The direction of the diode D3 in FIG. 8 is the same as that in FIG. 1, and is a direction in which the charging current of the input smoothing capacitor Ci can flow.

The second switch control circuit 34 is connected to the line 4
0 is connected to the gate of the third FET Q3. Since the second switch control circuit 34 applies a voltage between the gate and the source of the third FET Q3, it also has a connection to the source as is well known.
FETs Q1 and Q2 and this connection are omitted. Third
The current detector 35 is connected to the input line of the rectifier circuit 14 and the output line 36 is connected to the second switch control circuit 34 in order to control the FET Q3 to make the input current waveform approximate to a sine wave. . Further, a voltage detection line 37 is connected between the power supply 11 and the second switch control circuit 34 in order to use the voltage of the power supply 11 as a reference sine wave. One end of the input smoothing capacitor Ci is connected to the second switch control circuit 34 by a line 38 in order to control the third FET Q3 so that the voltage of the input smoothing capacitor Ci is constant. Also,
The third FE is synchronized with the first and second FETs Q1 and Q2.
The first and second switch control circuits 25, 34 are interconnected by a line 39 to drive TQ3 on.

FIG. 9 shows the second switch control circuit 34 of FIG.
FIG. The second switch control circuit 34 includes a current detection circuit 41, a voltage detection circuit 42, an error amplifier 43, a reference voltage source 44, a multiplier 45, a first comparator 46, a low-pass filter 47, a triangular wave generation circuit 48,
And a second comparator 49. One input terminal of the error amplifier 43 is connected to the voltage detection line 38 of the input smoothing capacitor Ci, and the other input terminal is connected to the reference voltage source 44. Therefore, the error amplifier 43 generates a signal corresponding to the difference between the voltage Vci of the input smoothing capacitor Ci and the voltage of the reference voltage source 44. The multiplier 45 is connected to the error amplifier 43 and the voltage detection circuit 42,
The output of the error amplifier 43 is multiplied by the rectified output waveform of the sine-wave power supply voltage detected in step 2, ie, the reference wave 50. Thereby, the amplitude of the reference wave changes according to the error output, and the reference wave including the voltage control information is obtained. The first comparator 46 generates a comparison output between the output of the multiplier 45 and the rectified waveform 51 of the input current waveform obtained from the current detection circuit 41. That is, the first comparator 46 generates an output including information on a difference between the input current waveform and the reference sine wave and voltage information on the input smoothing capacitor Ci. The low-pass filter 47 smoothes the output of the first comparator 46 and supplies it to one input terminal of the second comparator 46. The triangular wave generating circuit 48 connected to the other input terminal of the second comparator 46 has a first FET on a line 39 derived from the first switch control circuit 25.
A signal indicating the rise of the ON period of Q1 (time t1 in FIG. 10) or the end of the ON period of the second FET Q2 (t1 in FIG. 10).
A triangular wave 52 is generated in response to a signal indicating (at time 10).
Note that the triangular wave 52 has the same cycle as the ON / OFF cycle of the first and second FETs Q1, Q2. Second comparator 4
Numeral 9 compares the triangular wave 52 with the output of the low-pass filter 47 and sends a square wave pulse 53 for controlling the gate of the third FET Q3 to the line 40. The third FET Q3 turns on and off in response to the square wave pulse 53 on line 40.

Next, the operation of the switching power supply of FIG. 8 will be described with reference to the waveform diagram of FIG. However, most of the operation of the switching power supply device of FIG. 8 is the same as the operation of the switching power supply device of FIG. 1, and thus the description of the same operation will be omitted. The operations in the periods t0 to t1, t1 to t2, t2 to t3, t3 to t4, t5 to t6, t6 to t7, t7 to t8, and t8 to t9 in FIG. The operation is the same as that of the period indicated by the reference numeral. The operations during the periods ta to t5 and tb to t10 in FIG. 10 are the same as the operations during the periods t4 to t5 and t9 to t10 in FIG. The period from t4 to ta, t9 to t in FIG.
The period b is a new operation period generated based on the third FET Q3. Further, the period from tb to t10 and t10 to t10 in FIG.
The period t11 substantially corresponds to the periods t9 to t10 and t10 to t11 in FIG.

In FIG. 10, (A) to (G) and (I)
5 show the same portions as the waveforms of FIGS. 5A to 5G and 5I. FIG. 10H shows the current Iq3 of the third FET Q3. Since the third FET Q3 comprises a diode D3 and a switch S3, IQ3 is the sum of the current Id3 of the diode D3 and the current IS3 of the switch S3. To clarify the correspondence with FIG. 5, t0 to t in FIG.
Although the current for the four periods is shown as the current Id3 of the diode D3, in this embodiment, the third FET Q3 has t1 to ta.
Since the ON control pulse is given during the period, a current also flows through the switch S3 of the third FET Q3 during the period from t1 to t4. It is preferable that the ON start time of the third FET Q3 be at or near t4 in FIG. In this case, the time t at which the current Id3 of the diode D3 becomes zero is obtained.
4 to generate an on-control pulse for the third FET Q3, or the leading edge (t) of the control signal Vg1 shown in FIG.
1) or the trailing edge (t0) of the control signal Vg2 in FIG.
At time point), the mono multivibrator is triggered to generate a pulse until time point t4, and the third FE is generated at the trailing edge of the pulse.
A gate control pulse is applied to TQ3.

The circuit shown in FIG. 8 has a third FET Q3, and is turned on at least during a period from t4 to ta. Therefore, t4
Even after the conduction of the diode D3 is completed, the second auxiliary capacitor Cp is short-circuited by the switch S3 of the third FET Q3, and the voltage Vcp of the second auxiliary capacitor Cp, that is, the voltage Vd3 of the diode D3 and the voltage of the third FET Q3. Is maintained at substantially zero volt, and no bias voltage is generated with respect to the output voltage Va of the rectifier circuit 14. FIG. 5 (I) and FIG.
As is clear from the comparison of (I), the period of application of the bias voltage by the second auxiliary capacitor Cp is limited. Second
When the end time ta of the ON period of the third FET Q3 is controlled before and after by the switch control circuit 34, the time width of the interruption of the bias voltage changes. When the supply period of the bias voltage is short, the voltage Vci of the input smoothing capacitor Ci decreases, and when the supply period is long, the voltage Vci increases,
Voltage control of the input smoothing capacitor Ci is achieved, and this voltage Vci can be prevented from becoming abnormally high. For example, in the circuit of FIG. 1, the voltage of the input smoothing capacitor Ci reaches a maximum of about 200 V, but in FIG.
About V. Further, when the time width of the supply of the bias voltage changes, the current supplied to the input smoothing capacitor Ci through the rectifier circuit 14 flows, that is, the period and value of the input current Iin of the rectifier circuit 14 change, and the input current waveform changes. Improvement is achieved. For example, in the circuit of FIG.
Although it was about 97%, it becomes about 99.9% in FIG.

The interval between t9 and t11 in FIG. 10 and the interval between t9 and t in FIG.
Compared to 11 sections, IQ3 in FIG. 10 (H) and FIG.
Vd3 of (I) is different from Id3 of FIG. 5 (H) and Vd3 of FIG. 5 (I). 10 are replaced with t9 to t11 in FIG.
Although the circuit constant of the resonance circuit can be set so as to operate in the same manner as described above, in this embodiment, the capacity of the second auxiliary capacitor Cp is set to be much smaller than the capacity of the first auxiliary capacitor Cf. I have. Therefore, from t9 in FIG.
In the period tb, the same as in the periods t9 to t10 in FIG.
A current flows through the resonance circuit of Q2 and Cp-Cf-N1.
A current also flows through the auxiliary resonance circuit of -Q2, the second auxiliary capacitor Cp completes discharging relatively quickly, and at time tb, the reverse bias of the diode D3 is released, and Cf -N1 -Q2
Resonant current flows in the circuit of -D3. Also in the period from t10 to t11 in FIG. 10, which corresponds to the period from t10 to t11 in FIG. In FIG. 10, the voltage Vd3 for conducting the diode D3 during the period from tb to t11, that is, the voltage Vcp of the second auxiliary capacitor Cp becomes zero.

As is apparent from the above description, according to this embodiment, the input current waveform and the power factor can be improved satisfactorily by also using a part of the DC-DC conversion circuit. The rise of the voltage Vci can be suppressed.

[0036]

Second Embodiment Next, a switching power supply according to a second embodiment will be described with reference to FIG. However, in FIG. 11 and the drawings showing each embodiment which will be described later, the same parts as those in FIG. 8 are denoted by the same reference numerals, and description thereof will be omitted.
The switching power supply of FIG. 11 has a configuration similar to that of FIG. 8 except that a diode D4 is connected in place of the reactor L of FIG. 8 to increase the voltage of the resonance capacitor Cr. That is, since the reactor L in FIG. 8 is for smoothing, it does not have the function of increasing the voltage, but the diode D4 functions as one of the diodes forming the half-wave voltage rectifier circuit, and Capacitor Ci and resonance capacitor Cr
Increase the voltage. Note that the relationship between FIG. 11 and the half-wave voltage rectifier can be considered as follows. AC power supply is 1
The secondary winding N1, the capacitor at the input stage of the half-wave voltage rectifier circuit is a first auxiliary capacitor Cf, and the first diode connected to the AC power supply via the input stage capacitor is a built-in FET Q3. A second diode connected in series to the first diode is a diode D3.
The output stage capacitor connected in parallel to the series circuit of the first and second diodes is a smoothing capacitor Ci. Therefore, according to the second embodiment, the same operation and effect as those of the first embodiment can be obtained in addition to the operation and effect of the diode D4.

[0037]

Third Embodiment A switching power supply according to a third embodiment shown in FIG. 12 has the same configuration as that of FIG. 8 except that a reactor Lf is added to the circuit of FIG. The added reactor Lf is connected in series to the first auxiliary capacitor Cf, and functions as a resonance inductance instead of or together with the leakage inductance Lr of the transformer 20. Since the circuit of FIG. 12 is essentially the same as the circuit of FIG. 8, it has the same functions and effects as the first embodiment.

[0038]

Fourth Embodiment A switching power supply according to a fourth embodiment shown in FIG. 13 includes a third auxiliary capacitor C in the circuit shown in FIG.
The configuration is the same as that of FIG. 8 except that q3 is added and a diode D3 is provided separately from the built-in diode of the third FET Q3. The third auxiliary capacitor Cq3 is connected in series to the third FET Q3, and the diode D3 is connected in parallel to the series circuit of the third FET Q3 and the third auxiliary capacitor Cq3. Therefore, in the circuit of FIG. 13, the third auxiliary capacitor Cq3 is selectively connected in parallel to the second auxiliary capacitor Cp by the third FET Q3,
Operates in the same manner as the auxiliary capacitor Cp. That is, the third auxiliary capacitor Cq3 operates in the same manner as the second auxiliary capacitor Cp only during the ON period of the third FET Q3, and when a current flows through the second auxiliary capacitor Cp, the third auxiliary capacitor Cq3 is also applied to the third auxiliary capacitor Cq3. A current flows in the same path as the second auxiliary capacitor Cp. The voltage for biasing the output voltage of the rectifier circuit 14 includes second and third auxiliary capacitors Cp and C
Given by the composition of q3. Third auxiliary capacitor C
When the connection time width of q3 is adjusted by the third FET Q3, the amount of bias changes, and the voltage value of the input smoothing capacitor Ci,
The power factor and the input current waveform can be changed.

FIG. 14 shows the waveforms at various points in FIG. 13 as in FIG. In FIG. 14, the waveforms of (A) to (I) are substantially the same as the waveforms of (A) to (I) of FIG. 10, and the waveform of FIG. 14 (J) shows the waveform of the added third auxiliary capacitor Cq3. 7 shows a waveform of the voltage Vcq3. FIG.
The current IQ3 of the third FET Q3 of (H) indicates the sum of the current of S3 in the switch section and the current of the built-in diode, the positive current flows through the built-in diode, and the negative current flows through the switch. It flows through section S3. The voltage Vcp of the second auxiliary capacitor Cp of FIG. 13 is equal to the voltage of the third FET of FIG.
This is the sum of the voltage VQ3 of Q3 and the voltage Vcq3 of the third auxiliary capacitor Cq3 in FIG. T0 to t in FIG.
The operations during the four periods and the periods ta to t11 are shown in FIG.
The operation is substantially the same as the operation during the four periods and the periods ta to t11. In FIG. 14, the end point t5 of the resonance due to the leakage inductance Lr is earlier than the end point ta of the on-period of the third FET Q3.
Same as 0.

The switching power supply device of FIG. 13 has the same operation and effect as the first embodiment, and is controlled to selectively connect the third auxiliary capacitor Cq3. The feature is that there is little restriction on timing.

[0041]

Fifth Embodiment A switching power supply according to a fifth embodiment shown in FIG. 15 is formed in the same manner as in FIG. 13 except that the reactor L in FIG. 13 is replaced with a diode D4 as a current limiting impedance element. It is. Therefore, the fifth
According to this embodiment, the same operation and effect as those of the fourth embodiment can be obtained.

[0042]

Sixth Embodiment A switching power supply according to a sixth embodiment shown in FIG. 16 has a second switch control circuit 34 shown in FIG.
1 except that the second switch control circuit 34 is
3 is formed identically. The second switch control circuit 34a in FIG. 16 includes voltage detecting resistors R1 and R2 connected in parallel to an input smoothing capacitor Ci, a reference voltage source Vr, and an error amplifier EA. One input terminal of the error amplifier EA is connected to the voltage dividing point of the voltage detecting resistors R1 and R2, the other input terminal is connected to the reference voltage source Vr, and the output terminal is connected to the gate of the third FET Q3. I have. The error amplifier EA controls the third FET Q3 by forming a voltage corresponding to the difference between the detection voltage and the reference voltage. The third FET Q3 functions as a variable impedance element, and the resistance value (impedance value) changes according to the output of the error amplifier EA. As a result, the third auxiliary capacitor Cq3 and the third FET are connected to the second auxiliary capacitor Cp.
A series circuit with a variable impedance element comprising Q3 is connected in parallel, and the bias voltage value is determined by this parallel circuit. The bias voltage value is the third FET
Since the impedance is changed by the change in the impedance of Q3, control for keeping the voltage of the input smoothing capacitor Ci constant can be performed. Therefore, the third FET Q3 does not substantially contribute to the improvement of the input current waveform and the power factor, but contributes to the voltage control of the input smoothing capacitor Ci.

[0043]

Seventh Embodiment In a switching power supply according to a seventh embodiment of FIG. 17, the power supply 11 and the rectifier circuit 14 of FIG. 8 are modified into a three-phase AC power supply 11a and a three-phase rectifier circuit 14a. Three first auxiliary capacitors Cf1, Cf2, and Cf3 are connected between the first, second, and third input terminals 15, 16, and 60 and the upper end of the resonance capacitor Cr. Diodes D31, D32, D33, D34, D35,
With respect to D36, the second auxiliary capacitors Cp1, Cp2, Cp3,
FETS as Cp4, Cp5, Cp6 and third switch
8, except that reactors L1, L2, and L3 are connected in series to a three-phase AC line, respectively, and that S31, S32, S33, S34, S35, and S36 are connected in parallel.

To explain only the first phase, the first and second auxiliary capacitors Cf1 and Vp2 are connected to the resonance capacitor Cf1.
r, and the first and second auxiliary capacitors Cf1, Cp1 are connected in parallel with the resonance capacitor Cr via the input smoothing capacitor Ci. Therefore, the auxiliary capacitors Cf1, Cp1, and Cp2 contribute to the resonance operation similarly to the resonance capacitor Cr. In the circuit of FIG. 17, the diode D3 of FIG. 8 is shared by the rectifier diodes D31 and D32. Since the second auxiliary capacitors Cp1 and Cp2 are connected between the power supply 11a and the input smoothing capacitor Ci, they function as a bias voltage supply source. In this embodiment, since the third FETs S31 and S32 are connected in parallel with the second auxiliary capacitors Cp1 and Cp2 and the diodes D31 and D32, the second auxiliary capacitors Cp1 and Cp2 are connected in parallel.
The voltage of p2, that is, the bias voltage, can be controlled by the third FETs S31 and S32. Now, the operation of the first phase has been described. The same operation is performed in the remaining second and third phases. By controlling the bias voltage of each phase, the input current waveform of each phase is approximated to a sine wave. It becomes possible.

In the circuit of FIG. 17, one ends of the first and second auxiliary capacitors Cf1, Cf2, Cf3 and Cp1 to Cp6 are connected to the AC input terminals 15, 16, 60 of the rectifier circuit 14a. The current passing therethrough also flows to the power supply 11a, contributing to power factor improvement and waveform improvement. In other words, the AC power source 1 within the current flowing through the auxiliary capacitors Cf1, Cf2, Cf3
The component flowing to 1a changes according to the change in the amplitude of the voltage of the AC power supply 11a, and as a result, the waveform of the input current is improved. Now, an operation during a positive half cycle in which the upper diode D31 of the first phase and the lower diode D34 of the second phase conduct will be described as an example.
To t1, and the voltage Vin of the power supply 11a
Is at least the voltage Vcr of the resonance capacitor Cr.
When the voltage is higher than 1/2, a charging current flows through the resonance capacitor Cr in a closed circuit composed of 11a-Cf1-Cr-D34. Further, the voltage of the capacitor Cf2 is
Even when r is higher than the voltage Vcr, a current flows through the closed circuit of Cf2-Cr-D34. Among the currents of the rectifier diode D34, the current component of the closed circuit of 11a-Cf1-Cr-D34 passing through the power supply 11a is the input current Iin. The current of the closed circuit has a value proportional to the amplitude of the voltage Vin of the power supply 11a. In the period corresponding to t1 to t3 in FIG. 10, the current component passing through the power supply 11a is included in the auxiliary capacitor Cf1 as in the previous period. Also, when the voltage Vcr of the resonance capacitor Cr becomes higher than the voltage of the capacitor Cf1 during, for example, a period from t5 to t9 in FIG. A closed circuit of Cf2-11a-D31-Ci is formed, and a current flows through these closed circuits. The component passing through the power supply 11a out of the current passing through the rectifier diode D31 is the input current Iin, which changes according to the amplitude of the power supply voltage Vin. When the voltage Vcr of the resonance capacitor Cr becomes lower than the sum of the voltage Vin of the power supply 11a and the voltage of the capacitor Cf1 during a period corresponding to, for example, t10 to t11 in FIG. 10, the rectifier diode D34 is forward-biased and turned on. , 11a-
A closed circuit of Cf1-Cr-D34 and a closed circuit of Cf2-Cr-D34 are formed, and a current flows through the rectifier diode D34. The same operation as described above occurs in another phase.

[0046]

Eighth Embodiment A switching power supply according to an eighth embodiment shown in FIG. 18 has the third FETs S1, S2, S3, S4, S4 for the same purpose as the third auxiliary capacitor Cq3 in FIG.
5, third auxiliary capacitors Cs1, Cs2, Cs in series with S6.
The configuration is the same as that of FIG. 17 except that 3, Cs4, Cs5, and Cs6 are connected. Therefore, the same function and effect as those of FIGS. 17 and 13 can be obtained.

[0047]

Ninth Embodiment A switching power supply shown in FIG. 19 is different from the circuit of FIG.
The configuration is the same as that of FIG. 17 except that 1, Cp3 and Cp5 and the third FETs S31, S33 and S35 are omitted. Even with this configuration, the lower capacitors Cp2, Cp4, Cp6 and F
The ETSs 32, S34, and S36 operate in the same manner as in FIG. 17, and can obtain similar functions and effects. In the circuit of FIG. 19, the third FETs S32, S34,
A third auxiliary capacitor Cs2, Cs4, Cs6 can be connected in series with S36.

[0048]

[Modifications] The present invention is not limited to the above-described embodiment, and for example, the following modifications are possible. (1) In all the embodiments, the resonance capacitor Cr can be omitted. In this case, the auxiliary capacitor Cf,
Resonant operation by Cp, Cf1, Cf2, Cf3, Cp1 to Cp6 occurs. (2) In all embodiments, another resonance capacitor can be connected in parallel with the series circuit of the first FET Q1 and the primary winding N1. (3) The power supply 11a in FIGS. 17, 18, and 19 can be a single-phase power supply, and the rectifier circuit 14a can be a single-phase bridge circuit. In short, the three-phase circuits of FIGS. 17 to 19 can be replaced with single-phase circuits. (4) The second switch control circuits 34, 3 of the switching power supply of FIGS. 11, 12, 15, 17 to 19
Although 4b has the same or substantially the same configuration as that of FIG. 9, these can be modified as in the control circuit 34a of FIG. (5) In the embodiment having no third auxiliary capacitor Cq3, the diode D3 can be an independent diode instead of the diode built in the third FET Q3. (6) FIG. 8, FIG. 11, FIG. 12, FIG. 13, FIG.
At 6, the diode D3 can be omitted, and instead the third FET Q3 can be turned on while the diode D3 is conducting. (7) In all the embodiments, a voltage resonance capacitor similar to the capacitor Cq2 can be connected in parallel with the first FET Q1. In short, the voltage resonance capacitor can be provided in one or both of the first and second FETs Q1 and Q2. Note that the voltage resonance capacitor may be a stray capacitance. (8) In each embodiment, the first, second, and third FEs
TQ1, Q2, and Q3 can be replaced by first and second switches each comprising a bipolar transistor and a diode connected in anti-parallel thereto, or another similar semiconductor switch. (9) A resonance reactor can be connected in series with the primary winding N1. (10) A series circuit of the primary winding N1 and the current resonance capacitor Cr can be connected in parallel with the first FET Q1. In short, the first switch in each claim corresponds to the second FET Q2, and the second switch corresponds to the first FQ.
It can correspond to ETQ1.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a switching power supply device having a conventional power factor correction circuit.

FIG. 2 is a block diagram showing a control circuit of FIG. 1;

FIG. 3 is a waveform diagram showing a rectified voltage and a biased voltage in FIG. 1 in principle.

FIG. 4 is a diagram showing an equivalent circuit of a primary winding of the transformer of FIG.

FIG. 5 is a waveform chart showing a state of each unit in FIG. 1;

FIG. 6 is a diagram showing a relationship between on / off frequencies of first and second FETs Q1, Q2 in FIG. 1 and power supply to a secondary side of a transformer.

FIG. 7 is a waveform diagram showing the voltage amplitude of the primary winding when the on / off frequency of the first and second FETs Q1 and Q2 in FIG. 1 is low and high.

FIG. 8 is a circuit diagram illustrating the switching power supply device according to the first embodiment.

FIG. 9 is a circuit diagram showing a second switch control circuit of FIG. 8;

FIG. 10 is a waveform diagram showing a state of each unit in FIG.

FIG. 11 is a circuit diagram showing a switching power supply device according to a second embodiment.

FIG. 12 is a circuit diagram illustrating a switching power supply device according to a third embodiment.

FIG. 13 is a circuit diagram illustrating a switching power supply device according to a fourth embodiment.

14 is a waveform chart showing a state of each unit in FIG.

FIG. 15 is a circuit diagram illustrating a switching power supply device according to a fifth embodiment.

FIG. 16 is a circuit diagram illustrating a switching power supply device according to a sixth embodiment.

FIG. 17 is a circuit diagram illustrating a switching power supply device according to a seventh embodiment.

FIG. 18 is a circuit diagram illustrating a switching power supply device according to an eighth embodiment.

FIG. 19 is a circuit diagram showing the switching power supply device of the embodiment in FIG. 9;

[Explanation of symbols]

 Q1, Q2, Q3 FET Cr Resonance capacitor Ci Input smoothing capacitor Cf, Cp Auxiliary capacitor

Claims (14)

(57) [Claims] 1. An AC power supply having first and second power supply terminals for supplying at least one phase AC voltage, and first and second power supplies connected to the first and second power supply terminals.
A rectifier circuit having the following input terminals: an input smoothing capacitor connected between first and second output terminals of the rectifier circuit; and a first and second capacitor connected in parallel to the input smoothing capacitor. And a capacitor or a parasitic capacitance connected in parallel to the second switch, and a primary winding of a transformer having a resonance inductance connected in parallel to the second switch. A series circuit with a capacitor for resonance or a series circuit of a resonance reactor, a primary winding of a transformer and a resonance capacitor, a secondary winding of a transformer electromagnetically coupled to the primary winding, and the secondary winding And a first switch control circuit for alternately turning on and off the first and second switches at an on / off frequency higher than the frequency of the AC voltage. A diode having one end connected to a connection point between the input smoothing capacitor and the second switch, and the other end connected to the second output terminal of the rectifier circuit; A first auxiliary capacitor connected in parallel via the diode, a second auxiliary capacitor connected in parallel to the diode, a third switch connected in parallel to the diode, at least the first The third switch is turned on during a part of the period in which a current is flowing through the second switch, and the second switch is formed so that the on-time width of the third switch can be adjusted. A switching power supply device comprising a switch control circuit. 2. The switching power supply device according to claim 1, further comprising a reactor connected in series to an AC or DC line on a power supply side of the input smoothing capacitor. 3. The switching power supply according to claim 1, further comprising another diode connected in series between the third switch and the second output terminal of the rectifier circuit. apparatus. 4. The switching power supply device according to claim 2, further comprising another reactor connected in series to said first auxiliary capacitor. 5. The switching power supply device according to claim 1, further comprising a third auxiliary capacitor connected in series to said third switch. 6. An AC power supply having first and second power supply terminals for supplying at least one-phase AC voltage, and first and second power supplies connected to the first and second power supply terminals.
A full-wave rectifier circuit having the following input terminals: an input smoothing capacitor connected between first and second output terminals of the rectifier circuit; first and second capacitors connected in parallel to the input smoothing capacitor. A primary circuit of a transformer having a series circuit of a second switch; a capacitor or a parasitic capacitance connected in parallel to the second switch; and a resonance inductance connected in parallel to the second switch. And a series circuit of a resonance reactor and a primary winding of a transformer and a resonance capacitor; a secondary winding of a transformer electromagnetically coupled to the primary winding; An output rectifying / smoothing circuit connected to a winding; and a first switch control circuit for alternately turning on and off the first and second switches at an on / off frequency higher than the frequency of the AC voltage. A first auxiliary capacitor connected between the first input terminal of the rectifier circuit and a primary winding side terminal of the resonance capacitor; a second output terminal of the rectifier circuit; A second auxiliary capacitor connected in parallel with the rectifier diode connected between the first input terminal, a third switch connected in parallel with the rectifier diode, and at least the first switch For turning on the third switch during a part of the period when current is flowing through the third switch, wherein the third switch is formed so that the ON time width of the third switch can be adjusted. A switching power supply device comprising: a first switch control circuit and a second switch control circuit. 7. A third switch connected in series with the third switch.
7. The switching power supply according to claim 6, wherein the auxiliary capacitor is connected. 8. A three-phase AC power supply having first, second, and third power supply terminals; and a first, second, and third power supply terminals connected to the first, second, and third power supply terminals.
A rectifier circuit having six diodes connected in a three-phase bridge with second and third input terminals; an input smoothing capacitor connected between first and second output terminals of the rectifier circuit; A series circuit of first and second switches connected in parallel to the input smoothing capacitor; a capacitor or a parasitic capacitance connected in parallel to the second switch; A series circuit of a primary winding of a transformer having a resonance inductance and a resonance capacitor connected in parallel with each other or a series circuit of a reactor for resonance and a primary winding of a transformer and a resonance capacitor; A secondary winding of a transformer electromagnetically coupled to a line; an output rectifying and smoothing circuit connected to the secondary winding; and turning on and off the first and second switches higher than the frequency of the AC voltage. A first switch control circuit for alternately turning on and off at a frequency; and a first switch control circuit connected between the first, second, and third input terminals and a primary winding side terminal of the resonance capacitor. Three first auxiliary capacitors, and six parallel-connected to each of the six diodes.
And a second auxiliary capacitor connected in parallel with each of the six diodes.
At least one of the six third switches for turning on at least a part of a period during which a current flows through the first switch, wherein A second switch control circuit formed so as to be able to adjust the ON time width of the third switch. 9. Instead of providing six second auxiliary capacitors according to claim 8, each of three diodes between said second output terminal and said first, second and third input terminals. And a third switch connected in parallel to each of the three diodes instead of connecting a second auxiliary capacitor in parallel with the third diode and further providing six third switches. 10. The switching power supply device according to claim 8, further comprising a third auxiliary capacitor connected in series to the third switch. 11. The second switch control circuit is a circuit that controls an on-time width of the third switch so as to approximate an input current waveform of the rectifier circuit to a sine wave. Item 11. The switching power supply device according to any one of Items 1 to 10. 12. The control circuit according to claim 1, wherein the second switch control circuit controls an on-time width of the third switch so that a voltage of the input smoothing capacitor is substantially constant. The switching power supply device according to any one of the above. 13. The method of claim 1, or 2, or 3, or 6,
Or 8, or 9, or 11, or 12, the diode connected in parallel to the second auxiliary capacitor is omitted, and the current flowing through the diode is reduced to the third
A switching power supply device formed so as to pass through the switch. 14. The switching power supply device according to claim 1, wherein the resonance capacitor is omitted.