JP2005192285A - Switching power supply unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply unit which can achieve downsizing, noise reduction, and efficiency elevation by being able to cope with the regulation of higher harmonics with one converter. <P>SOLUTION: This switching power unit has a full wave rectifying circuit B1 which rectifies AC voltage, being connected to an AC power source Vac1; a main switch Q1 which is connected between the output end P2 on the negative electrode side of the full wave rectifying circuit B1 and one end of the primary winding 5a of a transformer T2; a smoothing capacitor C2 which is connected between the output end P2 on the negative electrode side of the full wave rectifying circuit B1 and the other end of the primary winding 5a; a series circuit which is connected between the output end P1 on the positive electrode side of the full wave rectifying circuit B1 and the tap TP of the primary winding 5a and where a reactor L1 and tertiary winding 5c are connected in series; rectifying and smoothing circuits D1 and C1 which rectify and smooth the voltage of the secondary winding 5b; and a control circuit 10 which controls the output voltage of the rectifying and smoothing circuits D1 and C1 into specified voltage by switching on or switching off the main switch Q1. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching power supply with high efficiency and high power factor.

  FIG. 18 shows a circuit configuration diagram of a conventional two-converter switching power supply device including a power factor correction circuit and a converter circuit. The switching power supply device shown in FIG. 18 inputs a full-wave rectification circuit B1 for full-wave rectification of the AC voltage of the AC power supply Vac1 and a full-wave rectification voltage from the full-wave rectification circuit B1 via a reactor (choke coil) L1. Then, the power factor improving circuit 50 which obtains a DC voltage by turning on / off the switch Q2 by the control signal from the control circuit 101 and rectifying and smoothing by the diode D2 and the capacitor C3, and the DC voltage from the power factor improving circuit 50 Is converted to another DC voltage.

  The control circuit 101 in the power factor correction circuit 50 controls the on period of the switch Q2 so that the peak current flowing through the switch Q2 is proportional to the input voltage, and turns on the switch Q2 after the current of the reactor L1 becomes zero. Let Specifically, the control circuit 101 compares the voltage across the resistor r3 that detects the current of the switch Q2 and the voltage obtained by dividing the input voltage (full-wave rectified voltage) by the resistor r1 and the resistor r2 (not shown). And an RS flip-flop (not shown) is operated by the output signal of the comparator to turn off the switch Q2. Thereby, the peak current of the switch Q2 is proportional to the input voltage. Further, the auxiliary winding 103 is added to the reactor L1, and the control circuit 101 detects that the flyback voltage generated in the auxiliary winding 103 becomes zero and turns on the switch Q2. That is, the current flowing through the reactor L1 starts from zero, reaches a peak on the sine wave envelope, and then returns to zero. Thereby, the input current (alternating current) flowing through the AC power supply Vac1 also becomes a sine wave current waveform following the AC voltage of the AC power supply Vac1, and the power factor is greatly improved.

  In addition, since the control circuit 101 performs on / off control of the switch Q2 based on the output voltage of the capacitor C3, the reference voltage, and the full-wave rectified voltage, the output voltage is kept constant.

  On the other hand, in the converter circuit 60, a main switch Q1 made of a MOSFET or the like is connected to the capacitor C3 via the primary winding 5a (number of turns n1) of the transformer T1, and both ends of the main switch Q1 are connected in series. A resistor R2 and a capacitor C2 are connected. The main switch Q1 is turned on / off by PWM control of the control circuit 102.

  Further, the primary winding 5a of the transformer T1 and the secondary winding 5b of the transformer T1 are wound so that opposite phase voltages are generated, and the secondary winding 5b (number of turns n2) of the transformer T1 is wound around the winding. A rectifying / smoothing circuit comprising a diode D1 and a capacitor C1 is connected. This rectifying / smoothing circuit rectifies and smoothes the voltage induced in the secondary winding 5b of the transformer T1 (on / off-controlled pulse voltage) and outputs a DC output to the load RL.

  The control circuit 102 includes an operational amplifier and a photocoupler (not shown). The operational amplifier compares the output voltage of the load RL with a reference voltage, and when the output voltage of the load RL becomes equal to or higher than the reference voltage, the main switch Control is performed so as to narrow the ON width of the pulse applied to Q1. That is, when the output voltage of the load RL becomes equal to or higher than the reference voltage, the output voltage is controlled to a constant voltage by narrowing the ON width of the pulse of the main switch Q1.

  Next, the operation of the converter circuit 60 will be described with reference to the timing chart shown in FIG. In FIG. 19, the voltage Q1v across the main switch Q1, the current Q1i flowing through the main switch Q1, the current n1i flowing through the primary winding 5a (number of turns n1) of the transformer T1, the current D1i flowing through the diode D1, and the main switch A Q1 control signal for ON / OFF control of Q1 is shown.

At time _{t 31,} the main switch Q1 is turned on by Q1 control signal, current Q1i is flowing through the main switch Q1 via the primary winding 5a of the transformer T1 from the capacitors C3. This current will linearly increase with time up to time t _32. Also, we continue to linearly increase with time until time _{t 32} as with current n1i also current Q1i flowing through the primary winding 5a.

In time _{t 32} from the time _{t 31,} the main switch Q1 side is the primary winding 5a - becomes the side, since the reversed phase to the primary winding 5a and the secondary winding 5b, the diode D1 Since the anode side is the-side, the current D1i does not flow through the diode D1.

Then, at time _{t 32,} the main switch Q1, the Q1 control signal, changes from the ON state to the OFF state. At this time, the energy induced in the primary winding 5a of the transformer T1 and the energy of the leakage inductance Lg (inductance not coupled to the secondary winding 5b) are stored in the capacitor C2 via the resistor R2. For this reason, voltage resonance is caused by the leakage inductance Lg of the primary winding 5a of the transformer T1 and the capacitor C2, and the resonance waveform is ringing at the time of turn-off (change from the on state to the off state) as shown in FIG. A waveform RG (damped vibration waveform) is obtained.

If the value of the capacitor C2 and the value of the resistor R2 are adjusted to appropriate values, this ringing waveform can be made very small. Then, the ringing waveform RG is attenuated with the lapse of time by the resistors R2 becomes a constant value, the constant value continues until just before the time t _33. At time _{t 32} ~ time _{t 33,} since the main switch Q1 is off, current Q1i and current n1i becomes zero.

In time _{t 33} from the time _{t 32,} becomes the primary switch Q1 side is the positive side of the primary winding 5a, since the reversed phase with and the primary winding 5a and the secondary winding 5b, diode D1 Since the anode side becomes a positive side, a current D1i flows through the diode D1.

According to such a converter circuit 60, the snubber circuit (C2, R2) is inserted at both ends of the main switch Q1, and the temporal change of the voltage of the main switch Q1 can be moderated, thereby reducing the switching noise. The surge voltage to the main switch Q1 due to the leakage inductance Lg of the transformer T1 can be suppressed.
JP 2001-157450 A (FIGS. 1 and 3)

  However, in this type of conventional switching power supply device, in order to comply with the harmonic regulation, the two-converter system of the power factor correction circuit 50 and the converter circuit 60 is used. For this reason, two control circuits (for power factor correction circuit and converter circuit) are required, and two switching circuits are also required.

  For this reason, the circuit is complicated and there are two switching portions, so noise and loss increase, which hinders miniaturization, low noise, and high efficiency.

  A first object of the present invention is to provide a switching power supply device that can cope with harmonic regulation with a single converter and that achieves miniaturization, low noise, and high efficiency. A second object of the present invention is to provide a switching power supply device that enables zero voltage switching by using an auxiliary switch and a capacitor to achieve low noise and high efficiency.

  The present invention has the following configuration in order to solve the above problems. The invention of claim 1 is a switching power supply device for inputting alternating current, improving power factor and outputting direct current, and connecting the alternating current power source to rectify the alternating voltage, and the negative side of the rectifying circuit A main switch connected between the output end and one end of the primary winding of the transformer, and a primary switch connected between the negative output side of the rectifier circuit and the other end of the primary winding of the transformer A smoothing capacitor, a first series circuit connected between a positive output terminal of the rectifier circuit and a tap of the primary winding of the transformer, and a reactor and a tertiary winding of the transformer connected in series; A rectifying / smoothing circuit for rectifying and smoothing the voltage of the secondary winding of the transformer; and a control circuit for controlling the output voltage of the rectifying / smoothing circuit to a predetermined voltage by turning on / off the main switch. And

  According to a second aspect of the present invention, there is provided the switching power supply device according to the first aspect, wherein a second series circuit is connected to both ends of the primary winding of the transformer and an auxiliary switch and a capacitor are connected in series; The control circuit controls the output voltage of the rectifying and smoothing circuit to a predetermined voltage by alternately turning on and off the main switch and the auxiliary switch. And

  According to a third aspect of the present invention, in the switching power supply device according to the first or second aspect, the secondary winding of the transformer is a voltage of each of the primary winding and the tertiary winding of the transformer. Is wound so as to generate a reverse phase voltage.

  According to a fourth aspect of the present invention, in the switching power supply device according to any one of the first to third aspects, the control circuit operates the main switch in an intermittent mode, and the bottom of the voltage of the main switch The main switch is turned on.

  According to a fifth aspect of the present invention, in the switching power supply device according to any one of the first to fourth aspects, the reactor is a leakage inductance of the transformer.

  According to a sixth aspect of the present invention, in the switching power supply device according to the fifth aspect, the transformer includes a core having a first leg, a second leg, and a third leg on which a magnetic circuit is formed, and the first leg includes the core. A primary winding and the secondary winding are wound, the tertiary winding is wound around the second leg, and a gap is provided on the third leg.

  According to a seventh aspect of the present invention, in the switching power supply device according to any one of the first to sixth aspects, the number of turns of the tertiary winding of the transformer is equal to or greater than the number of turns of the primary winding of the transformer. It is characterized by.

  The invention according to claim 8 is the switching power supply device according to any one of claims 1 to 7, wherein the tap of the primary winding of the transformer is located at the primary smoothing capacitor of the primary winding. It is a connection end.

  According to a ninth aspect of the present invention, in the switching power supply device according to any one of the first to seventh aspects, the position of the tap of the primary winding of the transformer is the main switch connection end of the primary winding. It is characterized by being.

  A tenth aspect of the present invention is the switching power supply device according to any one of the first to ninth aspects, wherein a connection point between the primary smoothing capacitor and the primary winding of the transformer and an AC input of the rectifier circuit. A diode is connected between at least one AC input end and the end.

  The invention of claim 11 is the switching power supply device according to any one of claims 1 to 10, characterized in that a DC power supply having an impedance in series is connected to the positive output side of the rectifier circuit. .

  According to the present invention, it is possible to cope with harmonic regulation with a single converter. In the continuous mode, zero voltage switching can be achieved by adding an active clamp circuit including an auxiliary switch and a capacitor, and noise and efficiency can be reduced.

  Further, in the intermittent mode, by turning on the main switch at the bottom of the main switch voltage, a quasi-resonant operation can be performed, and switching loss can be reduced and noise can be reduced.

  In addition, since the third leg provided with the gap acts as a path core, the reactor and the transformer can be integrated by using the transformer provided with the path core, and the magnetic path of the core can be shared, so that the transformer can be reduced in size.

  In addition, the size of the reactor and the harmonic current can be optimized by adjusting the tap position of the primary winding to the primary smoothing capacitor connecting end of the primary winding or the main switch connecting end of the primary winding. .

  Embodiments of a switching power supply apparatus according to the present invention will be described below in detail with reference to the drawings.

  The switching power supply device according to the first embodiment is a switching power supply device that inputs alternating current and outputs direct current. One converter can cope with harmonic regulation, and a transformer and a reactor are integrated to share a magnetic path. Thus, the transformer is miniaturized.

  FIG. 1 is a circuit configuration diagram of the switching power supply device according to the first embodiment. In the switching power supply shown in FIG. 1, a full-wave rectifier circuit B1 is connected to both ends of the AC power supply Vac1, and the negative-side output terminal P2 of the full-wave rectifier circuit B1 and the primary winding 5a (the number of turns n1) of the transformer T2 A main switch Q1 made of FET is connected between one end. A smoothing capacitor (corresponding to the primary smoothing capacitor) C2 is connected between the negative output terminal P2 of the full-wave rectifier circuit B1 and the other end of the primary winding 5a of the transformer T2.

  Between the positive output terminal P1 of the full-wave rectifier circuit B1 and the tap TP between one end and the other end of the primary winding 5a of the transformer T2, the reactor L1 and the tertiary winding 5c of the transformer T2 ( A series circuit with the number of turns n3) is connected. A diode D3 is connected to both ends of the main switch Q1. The diode D3 may be a parasitic diode of the main switch Q1. Reactor L1 may be a leakage inductance between primary winding 5a and tertiary winding 5c of transformer T2.

  A series circuit of a diode D1 and a smoothing capacitor C1 (secondary smoothing capacitor) is connected to the secondary winding 5b (number of turns n2) of the transformer T2. A load RL is connected in parallel to the smoothing capacitor C1. The voltage across the smoothing capacitor C1 is taken out as an output voltage, and the control circuit 10 performs on / off control of the main switch Q1 so that the output voltage of the smoothing capacitor C1 becomes a predetermined voltage.

  The secondary winding 5b of the transformer T2 is wound so that a reverse phase voltage is generated with respect to the voltages of the primary winding 5a and the tertiary winding 5c of the transformer T2. Further, the number of turns of the tertiary winding 5c of the transformer T2 is equal to or greater than the number of turns of the primary winding 5a of the transformer T2.

  Next, the operation of the switching power supply apparatus according to the first embodiment configured as described above will be described with reference to FIGS. FIG. 2 is a timing chart of signals in each part of the switching power supply device according to the first embodiment. FIG. 3 is a timing chart showing details of signals in each part of A part shown in FIG. FIG. 4 is a timing chart showing details of signals in each part of part B shown in FIG.

  2 to 4 show the input voltage Vi (AC voltage) of the AC power supply Vac1, the input current Ii (AC current) flowing through the AC power supply Vac1, the voltage Q1v of the main switch Q1, and the current Q1i flowing through the main switch Q1. ing.

At time _{t 1,} when the main switch Q1 turns on, current flows in the path of the C2 → 5a → Q1 → C2. For this reason, the energy stored in the smoothing capacitor C2 is discharged through the primary winding 5a of the transformer T2, and the energy is stored in the exciting inductance of the transformer T2.

At the same time, the AC voltage of the AC power supply Vacl is rectified by the full-wave rectifier circuit B1, and further, current flows through the path B1->L1->5c-> 5a TP->Q1-> B1, and energy is supplied to the reactor L1. Stored. At time _t 1 ~t _2, as shown in FIGS. 3 and 4, current Q1i of the main switch Q1 is gradually increased linearly.

Then, at time t _2, the the main switch Q1 is turned off, the exciting inductance and the energy stored in the reactor L1 of the transformer T2 through the tertiary winding 5c and the primary winding 5a of the transformer T2, a smoothing capacitor As C2 is charged, the voltage of the primary winding 5a increases, and the voltage of the secondary winding 5b also increases in proportion to the number of turns. Further, the voltage Q1v of the main switch Q1 also rises as shown in FIGS.

  When the voltage of the secondary winding 5b becomes equal to the voltage of the smoothing capacitor C1, the diode D1 conducts, current flows through 5b → D1 → C1 → 5b, and power is supplied to the load RL. .

  The current flowing through the reactor L1 (corresponding to the input current Ii) flows in proportion to the input voltage Vi, but becomes continuous near the top of the input voltage Vi, and the current flowing through the reactor L1 increases. Therefore, the input current Ii has a current waveform having a hump-like peak near the top of the input voltage Vi as shown in FIG. Further, the peak of the input current Ii is suppressed by the impedance of the reactor L1, and the harmonics of the input current Ii are reduced. Therefore, it is possible to cope with harmonic regulations with one converter.

  FIG. 3 shows details of the operation waveform near the peak of the input current Ii. As can be seen from FIG. 3, the input current Ii is continuous, the harmonic ripple is small, and a noise filter (not shown) disposed between the AC power supply Vac1 and the full-wave rectifier circuit B1 can be reduced in size. .

  FIG. 4 shows details of an operation waveform when the input voltage Vi is near zero voltage. It can be seen that the current Q1i flowing through the main switch Q1 has a waveform substantially equivalent to that near the top. This is because most of the excitation inductance of the transformer T2 and the energy stored in the reactor L1 is released to the output via the secondary winding 5b of the transformer T2, so that when the output power is constant, the excitation inductance of the transformer T2 This is because the sum of the energy with the reactor L1 is substantially constant. For this reason, even near the top of the input voltage Vi, the current Q1i flowing through the main switch Q1 does not increase and the loss does not increase.

  Further, the voltage of the reactor Ll becomes a value obtained by subtracting the voltage of the tap TP of the primary winding 5a of the transformer T2 from the sum of the peak value of the input voltage Vi and the voltage of the tertiary winding 5c. The voltage applied to the reactor L1 can be adjusted by the position of the tap TP of 5a. When the voltage applied to the reactor L1 is increased by moving the tap TP to the main switch Q1, the harmonics are reduced, but the capacity of the reactor L1 increases and the reactor L1 becomes larger.

  Therefore, by adjusting the position of the tap TP of the primary winding 5a within the range from the connection end of the smoothing capacitor C2 of the primary winding 5a to the connection end of the main switch Q1 of the primary winding 5a, the reactor The magnitude of L1 and the harmonic current can be optimized.

  The switching power supply device according to the second embodiment enables a quasi-resonant operation by operating the main switch in the intermittent mode and turning on the main switch at the bottom of the main switch voltage, thereby reducing the loss and noise of the main switch. It is characterized by aiming. In the intermittent mode, the magnetic energy of the transformer accumulated by the current supplied to the primary winding of the transformer is completely discharged as current from the secondary winding of the transformer, and then again the primary winding of the transformer. This is an operation mode for supplying current to the line.

  FIG. 5 is a circuit configuration diagram showing the switching power supply device of the second embodiment. The switching power supply device shown in FIG. 5 differs from the switching power supply device shown in FIG. 1 in that the transformer T3 is provided with an auxiliary winding 5d (number of turns n4) and only the configuration of the control circuit 10a is different. Only the components will be described.

  The auxiliary winding 5d is electromagnetically coupled to the primary winding 5a. One end of the auxiliary winding 5d is connected to the control circuit 10a, and the other end of the auxiliary winding 5d is grounded. The control circuit 10 a includes an output voltage detection circuit 21, an on / off control circuit 22, a delay circuit 23, a counter circuit 24, and an input voltage detection circuit 25.

  The output voltage detection circuit 21 detects the output voltage of the smoothing capacitor C 1, obtains an error voltage between this output voltage and the reference voltage, and outputs this error voltage to the on / off control circuit 22.

  The on / off control circuit 22 controls the output voltage to a constant voltage by performing on / off control of the main switch Q1 based on the error voltage from the output voltage detection circuit 21.

  The delay circuit 23 is composed of an integrating circuit (not shown) of a resistor and a capacitor, and delays the voltage generated in the auxiliary winding 5d, whereby the bottom (bottommost) of the voltage applied across the main switch Q1. Point) and the voltage falling time of the auxiliary winding 5d substantially coincide with each other.

  The counter circuit 24 counts the number of falling times of the voltage of the auxiliary winding 5d delayed by the delay circuit 23. The input voltage detection circuit 25 detects the full-wave rectified voltage of the full-wave rectifier circuit B1 that is directly proportional to the input voltage, and outputs it to the on / off control circuit 22.

  The on / off control circuit 22 is detected when the input voltage detection circuit 25 detects a voltage near the top and the counter circuit 24 counts the second or later falling of the voltage of the auxiliary winding 5d or when the input voltage detection circuit 25 When the voltage near zero is detected and the counter circuit 24 counts the first falling of the voltage of the auxiliary winding 5d, the main switch Q1 is turned on at the bottom of the main switch Q1.

  Next, the operation of the switching power supply apparatus according to the second embodiment configured as described above will be described with reference to FIGS. FIG. 6 is a timing chart showing details of signals in each part of the A part shown in FIG. FIG. 7 is a timing chart showing details of signals in each part of part B shown in FIG.

6 and 7, the input voltage Vi (AC voltage) of the AC power supply Vac1, the input current Ii (AC current) flowing through the AC power supply Vac1, the voltage Q1v of the main switch Q1, the current Q1i flowing through the main switch Q1, and the delay The delay output V _DL of the circuit 23 and the counter output V _CK of the counter circuit 24 are shown.

First, at time _{t 0,} the main switch Q1 is turned off, the voltage Q1v of the main switch Q1 is increased. In discontinuous mode operation, the input voltage is near the top, as shown in FIG. 6, at time t _{01 ~} time t _1, the voltage Q1v of the main switch Q1 will vary sinusoidally by quasi-resonant operation. In this example, from time t ₀ to time t ₁ , the voltage Q1v of the main switch Q1 has two falling edges.

Further, occurs voltage auxiliary winding 5d proportional to the voltage Q1v of the main switch Q1, the delay circuit 23 at time t ₁ by delaying the voltage generated in the auxiliary winding 5d, the voltage of the main switch Q1 Q1v The delay output V _DL is output to the counter circuit 24 by substantially matching the bottom of the auxiliary winding 5d with the falling edge of the voltage of the auxiliary winding 5d.

The counter circuit 24 is H level when the delayed output V _DL is more than the threshold value V _TH, when the delay output V _DL is less than the threshold V _TH generates a pulse signal which becomes L level, the falling of the pulse signal Count the number of downloads. As shown in FIG. 6, the number of falling times is 2 near the top of the input voltage.

The on / off control circuit 22 detects when the input voltage detection circuit 25 detects a voltage near the top of the input voltage and the counter circuit 24 counts the second fall of the voltage of the auxiliary winding 5d (FIG. 6). of time _{t 01} and time _t 1), to turn on the main switch Q1 at the bottom (time _{t 1)} of the main switch Q1.

On the other hand, the input voltage is near zero, as shown in FIG. 7, at time t _{0 ~} time t _1, the voltage Q1v of the main switch Q1 is reduced to a sine wave by quasi-resonant operation. In this example, from the time t ₀ to the time t ₁ , the voltage Q ₁ v of the main switch Q 1 has one falling. For this reason, the number of falling times is 1.

At this time, the on / off control circuit 22 detects when the input voltage detection circuit 25 detects a voltage near the zero voltage of the input voltage and the counter circuit 24 counts the first falling of the voltage of the auxiliary winding 5d (see FIG. 7 at time t ₁ ), the main switch Q 1 is turned on at the bottom of the main switch Q ₁ (time t ₁ ).

  As described above, according to the switching power supply device of the second embodiment, the main switch Q1 is operated in the intermittent mode, and the main switch Q1 is turned on at the bottom of the voltage Q1v of the main switch Q1, thereby enabling a quasi-resonant operation. It is possible to reduce the loss and noise of the switch Q1.

  The switching power supply device according to the third embodiment operates in a continuous mode, and is characterized in that zero voltage switching can be performed by adding an active clamp circuit including an auxiliary switch and a capacitor, thereby reducing noise and increasing efficiency. Continuous mode refers to the transformer primary side again before all of the transformer magnetic energy accumulated by the current supplied to the transformer primary winding is released as current from the transformer secondary winding. This is an operation mode for supplying current to the winding.

  FIG. 8 is a circuit configuration diagram showing a switching power supply device according to the third embodiment. A third embodiment shown in FIG. 8 is obtained by adding an active clamp circuit including an auxiliary switch and a capacitor to the configuration of the first embodiment shown in FIG.

  In FIG. 8, both ends of the primary winding 5a of the transformer T2 are connected to a series circuit of an auxiliary switch Q2 made of an FET and a capacitor C3. A diode D4 and a capacitor C5 are connected in parallel to both ends of the auxiliary switch Q2. A capacitor C4 is connected in parallel to both ends of the main switch Q1.

  The diode D3 and the capacitor C4 may be a parasitic diode and a parasitic capacitance of the main switch Q1, and the diode D4 and the capacitor C5 may be a parasitic diode and a parasitic capacitance of the auxiliary switch Q2.

  The control circuit 10a controls the output voltage to a predetermined voltage by alternately turning on / off the main switch Q1 and the auxiliary switch Q2.

  Next, a detailed operation will be described with reference to timing charts shown in FIGS. FIG. 9 is a timing chart of signals in each part of the switching power supply device according to the third embodiment. FIG. 10 is a timing chart showing details of signals at various parts when the main switch of the switching power supply device according to the third embodiment is turned on. FIG. 11 is a timing chart showing details of signals at various parts when the main switch of the switching power supply device according to the third embodiment is turned off. The waveform in FIG. 10 is the detail of part C in FIG. 9, and the waveform in FIG. 11 is the detail in part D in FIG.

  9 to 11, the input voltage Vi, the input current Ii, the voltage Q1v across the main switch Q1, the current Q1i flowing through the main switch Q1, the voltage Q2v across the auxiliary switch Q2, and the auxiliary switch Q2 flow. A current Q2i, a Q1 control signal Q1g for controlling on / off of the main switch Q1, and a Q2 control signal Q2g for controlling on / off of the auxiliary switch Q2 are shown.

At time _{t 1} (corresponding to time _t 11 _{~t 14),} when the main switch Q1 is turned on, a current flows Q1i in the path of the C2 → 5a → Q1 → C2. For this reason, the energy stored in the smoothing capacitor C2 is discharged through the primary winding 5a of the transformer T2, and the energy is stored in the exciting inductance of the transformer T2.

At the same time, the AC voltage of the AC power supply Vacl is rectified by the full-wave rectifier circuit B1, and further increases as the input current Ii flows along the path B1 → L1 → 5c → 5a TP → Q1 → B1. At the same time, energy is stored in the reactor L1. At time _t 1 ~t _2, as shown in FIG. 9, the current Q1i of the main switch Q1 is gradually increased linearly.

Then, at time _{t 2} (corresponding to time _t 21 _{~t 22),} when the main switch Q1 is turned off, the exciting inductance and the energy stored in the reactor L1 of the transformer T2, the tertiary winding 5c and the primary of the transformer As the smoothing capacitor C2 is charged through the winding 5a, the voltage of the primary winding 5a rises, and the voltage of the secondary winding 5b rises in proportion to the number of turns. Also, the voltage Q1v of the main switch Q1 increases.

  When the voltage of the secondary winding 5b becomes equal to the voltage of the smoothing capacitor C1, the diode D1 conducts, current flows through 5b → D1 → C1 → 5b, and power is supplied to the load RL. .

Further, the energy stored in the primary winding 5a of the transformer T2, at time _{t 22, 5a → C5 → C3} → 5a and current flows, as well as charges the capacitor C4, thereby discharging the capacitor C5. After the discharge of the capacitor C5 is completed (the voltage Q2v of the auxiliary switch Q2 becomes zero voltage), the capacitor C3 is charged through the diode D4. At time t ₂₂ the diode D4 is in conduction and turn on the auxiliary switch Q2, it is possible to achieve zero-voltage switching of the auxiliary switch Q2.

  After the charging of the capacitor C3 is completed, the electric charge charged in the capacitor C3 is discharged to the output through the auxiliary switch Q2 and the primary winding 5a. At this time, a current Q2i flows through the auxiliary switch Q2, a current flows through the primary winding 5a, and a current flows through the secondary winding 5b.

Next, when the auxiliary switch Q2 is turned off, a current flows through 5a → C2 → C4 → 5a, so that the capacitor C4 is discharged and the capacitor C5 is charged. After the discharge of the capacitor C4 is completed (the voltage Q1v of the main switch Q1 becomes zero voltage), the diode D3 becomes conductive. When the duration of the diode D3 is conducting (e.g. time t ₁₃ shown in FIG. ₁₀₎ to turn on the main switch Q1, it can achieve zero voltage switching of the main switch Q1.

  Thus, according to the switching power supply device of Example 3, as shown in FIG. 9, even when operated in the continuous mode, zero voltage switching can be achieved, and high efficiency and low noise can be achieved. Along with the decrease in the peak of the switch voltage, it can cope with high power.

(Structure of the transformer of the example)
FIG. 12 is a structural diagram of a transformer provided in the switching power supply device of each embodiment. The transformer shown in FIG. 12 has a Japanese-shaped core 30, and a primary winding 5a and a primary winding 5a are tightly coupled to the central leg 30a of the core 30 on the primary winding 5a. The secondary winding 5b is wound. That is, the primary winding 5a and the secondary winding 5b are wound on the same leg to obtain a small leakage inductance.

  Further, the tertiary winding 5c is wound around the side leg 30b, and a gap 31c is formed in the side leg 30c as a pass core. A large leakage inductance is provided in the tertiary winding 5c and the primary winding 5a by the gap 31c, and this leakage inductance is used as a substitute for the reactor L1.

  By using the leakage inductance for the reactor L1, the transformer and the reactor L1 can be integrated into a single transformer T2, and the transformer T2 can be downsized.

  A gap 31a is also formed in the central leg 30a of the core of the transformer T2. The gaps 31a and 31c are provided so that the electric charge stored in the smoothing capacitor C2 is stored in the inductance of the primary winding 5a in order to uniformly supply power to the load RL even in the valley of the AC input voltage. This is because the energy stored in the inductance (reactor L1) of both the primary winding 5a and the tertiary winding 5c is supplied to the load at the peak portion of the AC input voltage that is discharged. With this configuration, power can be supplied to the load RL even at the valley portion of the AC input voltage.

  In the transformer T2, when the main switch Q1 is turned on, as shown in FIG. 13, the magnetic flux φ1 generated in the primary winding 5a and the magnetic flux φ2 generated in the tertiary winding 5c all pass through the side legs 30c. . Therefore, when the output power is constant, the magnetic flux (φ1 + φ2) of the side leg 30c is substantially constant. For this reason, if the number of turns n1 of the primary winding 5a and the number of turns n2 of the secondary winding 5b are the same, the cross-sectional area of the core 30 of the transformer T2 is The area of 30a is 1, and the area of the side leg 30b is 0.5.

  In the vicinity of the top of the input voltage, the voltage of the smoothing capacitor C2 and the input voltage are substantially equal, so that the respective magnetic fluxes are equal and 1/2 of the side leg 30c, and in the valley of the input voltage, the magnetic flux of the side leg 30b is Nearly zero. Therefore, the magnetic flux of the center leg 30a and the magnetic flux of the side leg 30c are equal. For this reason, since the side leg 30c portion can be shared, the transformer T2 can be reduced in size.

  Further, since the magnetic flux generated in the side leg 30b is inversely proportional to the number of turns, the number of turns becomes small if the number of turns is increased. However, the number of turns of the tertiary winding 5c is made the same as the number of turns of the primary winding 5a. When the number of turns of the winding 5a is about 1.5 times, the magnetic flux of the central leg 30a is about 0.5, which is suitable considering the shape of the core 30.

  FIG. 14 is a circuit configuration diagram illustrating a switching power supply device according to a fourth embodiment. The switching power supply device shown in FIG. 14 differs from the switching power supply device shown in FIG. 1 in that diodes D5 and D6 are provided. The anode of the diode D5 is connected to one end of the AC power supply Vac1 (one end of the AC input end of the full-wave rectifier circuit B1), and the cathode of the diode D5 is a connection point between the smoothing capacitor C2 and the primary winding 5a of the transformer T2. It is connected to the. The anode of the diode D6 is connected to the other end of the AC power supply Vac1 (the other end of the AC input end of the full-wave rectifier circuit B1), and the cathode of the diode D6 is connected to the smoothing capacitor C2 and the primary winding 5a of the transformer T2. Connected to the connection point.

  According to the above configuration, when the AC power supply Vac1 is turned on, the rush current flows to the smoothing capacitor C2 via the diodes D5 and D6. For this reason, the rush current does not flow through the windings 5a to 5c of the transformer T2. As a result, the winding of the transformer T2 can be easily selected.

  In the fourth embodiment, both the diodes D5 and D6 are provided. However, for example, only one of the diodes D5 and D6 may be provided.

  FIG. 15 is a circuit configuration diagram illustrating a switching power supply device according to a fifth embodiment. The switching power supply device according to the fifth embodiment is characterized in that the power factor is further improved by reducing the peak current of the input current.

In FIG. 15, a DC power supply Vdc1 having impedance is connected between the positive output terminal P1 of the full-wave rectifier circuit B1 and the reactor L1. The DC power supply Vdc1 consists impedance unit 40 and the power supply unit _{E 1} Tokyo.

  Since such a DC power supply Vdc1 is connected in series with the positive-side output terminal P1 of the full-wave rectifier circuit B1, when the input current Ii increases rapidly, the DC voltage decreases due to the impedance of the impedance unit 40, and the input The peak current of the current Ii can be suppressed.

  FIG. 16 is a specific circuit configuration diagram of the switching power supply device according to the fifth embodiment. FIG. 17 is a timing chart of signals in each part of the switching power supply device according to the fifth embodiment.

  In FIG. 16, the tertiary winding 5c of the transformer T2 is provided with a tap TPx, and a capacitor Cx is connected between the tap TPx and the positive output terminal P1 of the full-wave rectifier circuit B1. A diode Dx is connected between one end of the tertiary winding 5c of the transformer T2 and the positive output terminal P1 of the full-wave rectifier circuit B1. A reactor L1 is connected between the other end of the tertiary winding 5c of the transformer T2 and the tap TP of the primary winding 5a.

  According to the above configuration, the voltage of the tap TPx of the tertiary winding 5c is rectified by the diode Dx and stored in the capacitor Cx. In this case, the value of the capacitor Cx is set so as to be low impedance with respect to the switching frequency of the main switch Q1 and high impedance with respect to the commercial frequency. In this way, as shown in FIG. 17, the peak current is suppressed almost in inverse proportion to the input current Ii, and the input current waveform can be approximated to a sine wave. For this reason, it can respond to a harmonic regulation further.

  In addition, this invention is not limited to the switching power supply device of Example 1 thru | or Example 5. For example, the diodes D5 and D6 of the switching power supply device shown in FIG. 14 may be added to the same location of the switching power supply device shown in FIG. Further, for example, the DC power supply Vdc1 of the switching power supply device shown in FIG. 15 may be added to the same location of the switching power supply device shown in FIG.

  The switching power supply device of the present invention can be applied to an AC-DC conversion type power supply circuit.

1 is a circuit configuration diagram illustrating a switching power supply device according to a first embodiment. 3 is a timing chart of signals in each part of the switching power supply device according to the first embodiment. It is a timing chart which shows the detail of the signal in each part of the A section shown in FIG. It is a timing chart which shows the detail of the signal in each part of the B section shown in FIG. FIG. 6 is a circuit configuration diagram illustrating a switching power supply device according to a second embodiment. It is a timing chart which shows the detail of the signal in each part of the A section shown in FIG. It is a timing chart which shows the detail of the signal in each part of the B section shown in FIG. FIG. 6 is a circuit configuration diagram illustrating a switching power supply device according to a third embodiment. 10 is a timing chart of signals in each part of the switching power supply device according to the third embodiment. It is a timing chart which shows the detail of the signal in each part at the time of the turn-on of the main switch of the switching power supply device of Example 3. It is a timing chart which shows the detail of the signal in each part at the time of the turn-off of the main switch of the switching power supply device of Example 3. It is a structural diagram of a transformer provided in the switching power supply device of each embodiment. It is a figure which shows distribution of the magnetic flux of the transformer shown in FIG. FIG. 6 is a circuit configuration diagram illustrating a switching power supply device according to a fourth embodiment. FIG. 10 is a circuit configuration diagram illustrating a switching power supply device according to a fifth embodiment. It is a concrete circuit block diagram of the switching power supply device of Example 5. 10 is a timing chart of signals in each part of the switching power supply device according to the fifth embodiment. It is a circuit block diagram of the switching power supply device of the 2 converter system of the conventional power factor improvement circuit and converter circuit. It is a timing chart of the signal in each part of the converter circuit in the conventional switching power supply device. It is a timing chart which shows the ringing waveform at the time of the turn-off of the main switch in the converter circuit in the conventional switching power supply device.

Explanation of symbols

Vac1 AC power supply B1 Full-wave rectifier circuit 10, 10a, 10b, 101, 102 Control circuit Q1 Main switch Q2 Auxiliary switch RL Load
C1 smoothing capacitor (secondary smoothing capacitor)
C2 smoothing capacitor (primary smoothing capacitor)
C3 to C5, Cx Capacitors D1 to D6, Dx Diode L1 Reactor T1, T2, T3 Transformer 5a Primary winding (n1)
5b Secondary winding (n2)
5c Tertiary winding (n3)
5d Auxiliary winding (n4)
TP tap 21 output voltage detection circuit 22 on / off control circuit 23 delay circuit 24 counter circuit 25 input voltage detection circuit 30 core

Claims (11)

A switching power supply that inputs alternating current, improves power factor and outputs direct current,
A rectifier circuit that rectifies the AC voltage by connecting to an AC power source;
A main switch connected between the negative output side of the rectifier circuit and one end of the primary winding of the transformer;
A primary smoothing capacitor connected between the negative output side of the rectifier circuit and the other end of the primary winding of the transformer;
A first series circuit connected between a positive output terminal of the rectifier circuit and a tap of the primary winding of the transformer, and a reactor and a tertiary winding of the transformer connected in series;
A rectifying / smoothing circuit for rectifying and smoothing the voltage of the secondary winding of the transformer;
A control circuit for controlling the output voltage of the rectifying and smoothing circuit to a predetermined voltage by turning on and off the main switch;
A switching power supply device comprising: A second series circuit connected to both ends of the primary winding of the transformer and having an auxiliary switch and a capacitor connected in series;
A diode connected in parallel to the auxiliary switch;
The switching power supply device according to claim 1, wherein the control circuit controls the output voltage of the rectifying and smoothing circuit to a predetermined voltage by alternately turning on and off the main switch and the auxiliary switch.   The secondary winding of the transformer is wound so that a negative phase voltage is generated with respect to the voltages of the primary winding and the tertiary winding of the transformer. The switching power supply device according to claim 1 or 2.   4. The switching power supply according to claim 1, wherein the control circuit operates the main switch in an intermittent mode and turns on the main switch at a bottom of a voltage of the main switch. 5. apparatus.   The switching power supply device according to any one of claims 1 to 4, wherein the reactor is a leakage inductance of the transformer.   The transformer includes a core having a first leg, a second leg, and a third leg on which a magnetic circuit is formed, the primary winding and the secondary winding are wound around the first leg, and the first leg 6. The switching power supply device according to claim 5, wherein the tertiary winding is wound around two legs, and a gap is provided on the third leg.   7. The switching power supply device according to claim 1, wherein the number of turns of the tertiary winding of the transformer is equal to or greater than the number of turns of the primary winding of the transformer.   8. The switching power supply device according to claim 1, wherein a position of a tap of the primary winding of the transformer is a connection end of the primary smoothing capacitor of the primary winding. 9. .   8. The switching power supply device according to claim 1, wherein the position of the tap of the primary winding of the transformer is the main switch connection end of the primary winding. 9.   2. A diode is connected between a connection point between the primary smoothing capacitor and the primary winding of the transformer and at least one AC input terminal of the AC input terminal of the rectifier circuit. The switching power supply device according to claim 9. 11. The switching power supply device according to claim 1, wherein a DC power supply having an impedance in series is connected to a positive output side of the rectifier circuit.

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