JPH0715967A - Switching power supply - Google Patents

Abstract

PURPOSE:To provide an AC input switching power supply with a high power factor and efficiency with a simple configuration consisting of one set of switching elements and a control circuit in an AC input switching power supply. CONSTITUTION:In this switching power supply where a smoothing capacitor 32 is connected between output terminals of a full-wave rectifier 21 connected to an AC power supply 20, the series circuit of a primary winding 28 of a transformer 27 and a switching element 34 is connected between the terminals of the smoothing capacitor 32, a rectification smoothing circuit 35 is connected to the secondary winding 29 of the transformer 27, and power is supplied to a load 40 connected to the output terminal of the rectification smoothing circuit 35, an inductor 26 and a control winding 31 of the transformer 27 are connected in series between the full-wave rectifier 21 and the smoothing capacitor 32.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a switching type DC stabilized power supply device which receives AC as an input.

[0002]

2. Description of the Related Art FIG. 8 shows a first structure of a conventional AC input switching power supply. The conventional AC input switching power supply has a configuration including a commercial AC power supply 1, a full-wave rectifier 2, diodes 3, 4, 5, and 6, a smoothing capacitor 7, a transformer 8, and a primary winding thereof that compose the commercial AC power supply 1. 9, a secondary winding 10, a switch element 11, a rectifying / smoothing circuit 12, a load 13, and a control circuit 14. The operation of the first configuration of the conventional AC input switching power supply is as follows. The input of the commercial AC power supply 1 is rectified by the full-wave rectifier 2 and smoothed by the smoothing capacitor 7 to a direct current with less ripple, and then the switch element 11 is switched on. By turning on and off at a frequency higher than the input commercial AC frequency, an AC voltage is applied to the primary winding 9 of the transformer 8, and its output is applied from the secondary winding 10 of the transformer 8 to the rectifying and smoothing circuit. Rectified and smoothed, and load 1 as DC output voltage
Give to 3. Here, the control circuit 14 detects the output voltage of the rectifying / smoothing circuit 12 and turns on / off the switch element 11 so that the output voltage becomes a predetermined voltage. As described above, this configuration has a function of exchanging the input of the commercial AC power supply 1 with a stable DC voltage and outputting the DC voltage.

(3) FIG. 9 shows a second configuration of a conventional AC input switching power supply. 8, those parts which are the same as those corresponding parts in FIG. 8 are designated by the same reference numerals, and a description thereof will be omitted. 8 is different from the configuration of FIG.
The booster chopper circuit 15, the inductor 16 of the booster chopper circuit 15, the switch element 17, the diode 18, and the control circuit 19 of the booster chopper circuit 15. The control circuit 19 of the step-up chopper circuit 15 is a control circuit that controls the output voltage of the step-up chopper circuit 15, that is, the voltage of the smoothing capacitor 7, to a constant value. In the operation of the second conventional configuration, the switching element 17 is turned on and off at a frequency higher than the input commercial AC frequency, the current is stored in the inductor 16 at the time of turning on, and the operation of discharging at the time of turning off is repeated. The waveform of Iin (2) is approximated to a sine wave of voltage waveform. Therefore, a power source with a high power factor can be constructed.

[0004]

However, the two conventional configurations have the following problems. FIG. 10 shows operation waveforms of the first configuration of the conventional AC input switching power supply.
Vin (1) in the figure shows the output voltage of the full-wave rectifier 2 with respect to the voltage of the commercial AC power supply 1, and Iin (1) shows the waveform of the input current from the commercial AC power supply 1. As can be seen from the figure, in the first configuration, there is a problem that the input current becomes a surge and the power factor is extremely low. FIG. 11 shows operation waveforms of the second configuration of the conventional AC input switching power supply. In the figure, Vin (2) shows the output voltage of the full-wave rectifier 2 with respect to the voltage of the commercial AC power supply 1, and Iin (2) shows the waveform of the input current from the commercial AC power supply 1. As can be seen from the figure, in the second configuration, the line connecting the peak values of the input current is approximate to the sine wave of the input voltage, so it may be immediately before the full-wave rectifier 2,
Immediately after that, if a low-pass filter for removing high-frequency ripple is used, the input current can be made approximately a sine wave,
A power supply with a high power factor can be realized.

However, as shown in FIG. 9, in order to increase the power factor, the boost chopper circuit 15 is used. In contrast to the conventional first structure, the inductor 16, diode (4) 18 The switching element 17 and the control circuit 19 are required, and the control circuit has two systems, and the number of parts is considerably increased and becomes complicated, so that there is a problem that the size cannot be reduced. Further, since the step-up chopper circuit 15 is used, the output voltage of the step-up chopper circuit 15, that is, the voltage of the smoothing capacitor 7, becomes higher than the commercial AC input voltage V, and the switch element 11 having a high withstand voltage is used. Since the high withstand voltage switch element has a large on-resistance, the voltage generated between the terminals of the switch element 11 when the switch element 11 is turned on is large, and the power consumed there is increased to increase the switching power supply. There is a problem of reducing the efficiency of.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to provide an AC input switching power supply having a high power factor and a high efficiency with a simple structure including a pair of switch elements and a control circuit. And

[0007]

A smoothing capacitor 32 is connected between the output terminals of a full-wave rectifier 21 connected to an AC power source 20, and a primary winding of a transformer 27 is connected between the terminals of the smoothing capacitor 32. 28 and a switch element 34 are connected in series, a secondary winding 29 of the transformer 27 is connected to a rectifying / smoothing circuit 35, and power is supplied to a load 40 connected to an output terminal of the rectifying / smoothing circuit 35. In the switching power supply, the inductor 26 and the control winding 31 of the transformer are connected in series between the full-wave rectifier 21 and the smoothing capacitor 32.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of the present invention. The configuration of this embodiment includes a commercial AC power source 1, a full-wave rectifier 21, a first diode 22, a second diode 23, a third diode 24, which constitute the full-wave rectifier 21, Fourth Dio
25, inductor (5) inductor 26, transformer 27 and its primary winding 28, secondary winding 29, tertiary winding 30, control winding 31, smoothing capacitor 3
2, a fifth diode 33, a switch element 34, a rectifying / smoothing circuit 35, and a sixth diode 3 constituting the same.
6, a seventh diode 37, an inductor 38, a capacitor 39, a load 40, and a control circuit 41.

This operation is as follows. Transformer 27
The number of turns of each winding is N1 for the primary winding 28, N2 for the secondary winding 29, N3 for the tertiary winding 30, and N for the control winding 31.
4, and the potentials at points a, b, and c in the diagram of FIG. 1 are Va, Vb, and Vc, respectively. If N1 = N4 is set here,
When the switch element 34 is on, the voltage of the smoothing capacitor 32, that is, Vb is applied to the primary winding 28 of the transformer 27. At this time, V is applied to the fourth winding 31 of the transformer 27.
A voltage of b.times.N4 / N1 is generated, but since it has been set that N1 = N4, this becomes almost equal to Vb. Therefore, a
The voltage Va at the point becomes zero volts when the voltage Vb generated by the control winding 31 of the transformer 27 is subtracted from the voltage Vb of the smoothing capacitor 32. That is, when the switch element 34 is on,
The potential at the point will always be zero volts. Further, the flow of current in the circuit when the switch element 34 is ON is as follows: first, from the smoothing capacitor 32 to the primary winding 28 of the transformer 27, the secondary winding 29, and the rectifying / smoothing circuit 35. Load 40
Via the switch, it returns to the primary winding 28 of the transformer and flows through the switch element 34, thereby transmitting the energy of the smoothing capacitor 32 to the load 40. When the switch element 34 is on, the voltage Va at the point a is always 0 volt, so the input voltage Vin (3) is applied to the inductor 26, the inductance of the inductor 26 is L26, and the current flowing through the inductor 26 is IL. (on), when the time after turning on the switch element 34 is t

[Equation 1] The current determined by is flowing through the inductor 26. This current first flows through the control winding 31 of the transformer (6) 27, and as a result, flows through the primary winding 28 of the transformer 27 and then through the switch element 34. With such a current flow, the commercial AC power supply 2
Zero energy is stored in the inductor 26.

Next, when the switch element 34 is off, the tertiary winding 30 of the transformer 27 is reset to reset the transformer.
A counter electromotive force is generated in the smoothing capacitor 32 and a current flows into the smoothing capacitor 32 via the diode 33. At this time, the voltage Vb of the smoothing capacitor 32 is applied between the terminals of the tertiary winding 30 of the transformer 27.
Therefore, the voltage VN4 (off) generated in the control winding 31 of the transformer 27 is

[Equation 2] Becomes Therefore, the voltage Va (off) at point a is

[Equation 3] And this result → input voltage Vin to inductor 26
Voltage difference from (3)

[Equation 4] Is applied, the current flowing through the inductor 26 decreases. The current flow in the circuit when the switch element 34 is off is as follows. First, the current for resetting the transformer 27 is transferred from the tertiary winding 30 of the transformer 27 through the diode 33. , The current flowing through the inductor 26 flows into the smoothing capacitor 32 via the control winding 31 of the transformer 27 while the switch element 34 is off, and at the same time, the control winding of the transformer 27 increases. As a result of flowing through the line 31, a current corresponding thereto flows from the tertiary winding 30 of the transformer 27 into the smoothing capacitor 32 via the diode 33. That is, due to such a current flow, the exciting energy of the transformer 27 is sent to the smoothing capacitor 32 for resetting the transformer 27 while the switch element 34 is off, and at the same time,
The energy stored in the inductor 26 is sent to the smoothing capacitor 32. Simultaneously with the above operation, the control circuit 41 controls by changing the ON / OFF period of the switch element 34 so that the output voltage of the rectifying / smoothing circuit 35 becomes a predetermined voltage. (7)

FIG. 7 is an operation waveform diagram of each part of the embodiment of the present invention (FIG. 1). As described above, the input voltage Vin (3) is applied between the terminals of the inductor 26 while the switch element 34 is ON. Is applied and the switch element 34 is off,

[Equation 5] Is applied, the current of the inductor 26 when the switch element 34 is turned on is as described above.

It is expressed by Where Vin (3) is the commercial input voltage, L26 is the inductance of the inductor 26,
t is the time after the switch element 34 is turned on, and the current of the inductor 26 is set to zero ampere immediately before the switch element 34 is turned on. Therefore,
When the switching power supply of the circuit of the present invention is in a steady operation, the ON width ton of the switch element 34 is considered to be substantially constant in the commercial AC cycle.
Let IL (peak1) be the peak value of the current in the inductor 26 during one cycle in which is turned on and off at a high frequency.

[Equation 6] Becomes Therefore, it can be seen from the above equation that Vin (3) is a sine wave, and the line connecting the peak value IL (peak) of the current of the inductor 26 is also a sine wave. Next, when the switch element 34 is turned off, the inductor 26

[Equation 7] Becomes Here, Vin (3) is the commercial input voltage, Vb is the voltage of the smoothing capacitor 32, N3 is the tertiary winding 30 of the transformer 27.
, N4 is the number of turns of the four control lines 31 of the transformer 27. Therefore, the time toff-1 from when the switch element 34 is turned off until the current of the inductor 26 becomes zero amperes
Is expressed by the following equation.

[Equation 8] (8) Therefore, the sum of ton and toff-1 is

[Equation 9] The current waveform at this time is as shown in FIG. Therefore,
If the current of the inductor 26 is set so as to always be reset to zero amperes in the cycle of high frequency switching, the inductor 2 in one cycle of high frequency switching will be described.
The average value IL (ave) of the current of 6 is given by the following equation, where to is the cycle of high frequency switching.

[Equation 10] Here, Vin (3) is a commercial input voltage and is a sine wave, so
If Vb is increased from 1.5 (2) times or more to Vin (3), IL (ave) in the commercial cycle is approximately a sine wave. That is, with respect to the current of the inductor 26 that increases and decreases at high frequencies, immediately before the full-wave rectifier 21, or
Immediately after that, by using a low-pass filter for removing high-frequency ripple, the commercial input current waveform can be approximately a sine wave, and the power factor can be increased.

In the above embodiment, the power factor is improved by adding the control winding of the inductor 26 and the transformer 27 to the conventional AC input switching power supply. Further, the voltage applied to the inductor 26 while the switch element is off is as follows:
While it is the difference voltage between the smoothing capacitor and the input voltage,
In the embodiment, since the input voltage is subtracted from the sum of the voltage of the smoothing capacitor and the voltage generated in the control winding of the transformer, the voltage of the smoothing capacitor necessary to reset the current of the inductor 26 is In this case, the voltage generated in the control winding of the transformer can be lowered as compared with the conventional AC input switching power supply. That is, as the switch element, one having a low breakdown voltage and a small on-resistance can be used, and the efficiency of the switching power supply can be improved.

(9) FIG. 2 shows another embodiment of the present invention. In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. The difference from the configuration of FIG. 1 is that the transformer 27 in FIG.
While the third winding 30 of FIG. 2 is connected between the terminals of the smoothing capacitor 32 via the diode 33, the third winding 30 of the transformer 27 is connected via the diode 33 in FIG. That is, it is connected between the terminals of the rectifying and smoothing capacitor 35.

In contrast to FIG. 1, the operation of FIG. 2 differs from that of FIG.
The current of 6 flows into the smoothing capacitor 32 through the control winding of the transformer 27 and, at the same time, flows through the control winding of the transformer 27. As a result, a current corresponding to it flows from the tertiary winding 30 of the transformer 27 to the diode. The energy stored in the inductor 26 flows into the capacitor 39 of the rectifying / smoothing circuit 35 via 33, that is, while the switch element 34 is off due to such a current flow, the energy stored in the inductor 26 and the smoothing capacitor 32 are It is sent to the capacitor 39 of the rectifying / smoothing circuit 35. Other operations are the same as those in FIG. 1, and the same effects are obtained.

FIG. 3 is a circuit diagram of another embodiment of the present invention in which the tertiary winding 30 and the diode 33 of the transformer 27 are omitted. The smoothing capacitor 32 of the smoothing capacitor 32 is turned on while the switch element 34 is on. Energy is stored in the transformer 27, and while the switch element is off, the energy stored in the transformer 27 is sent to the load via the rectifying / smoothing circuit 45, and at the same time, the current of the inductor 26 changes. As a result of flowing into the smoothing capacitor 32 via the control winding 31 of the transformer 27 and, at the same time, flowing through the control winding 31 of the transformer 27, a current corresponding thereto flows from the secondary winding 29 of the transformer 27 to the capacitor of the rectifying / smoothing circuit 45. It flows into 47. That is, while the switch element 34 is off, the energy stored in the inductor 26 is sent to the smoothing capacitor 32 and the capacitor 47 of the rectifying / smoothing circuit 45. Other operations are the same as those in FIG. 1, and the same effects are obtained. (10)

FIG. 4 is a circuit diagram of another embodiment of the present invention. This embodiment is different from FIG. 3 in that the capacitor 50 is connected between the terminals of the switch element 34. This operation is performed before the switch element 34 is turned on after the exciting inductance of the transformer 27 and the capacitor 50 resonate after the exciting current of the transformer 27 is reset to zero ampere while the switch element 34 is off. Since the voltage across the terminals of 34 is lowered to around zero volt, it is possible to reduce the switching loss when the switch element is turned on.

FIG. 5 is a circuit diagram of another embodiment of the present invention, showing an example in which a capacitor 48 is connected in series with the control winding 31 of the transformer 27, and a diode 49 is connected in parallel with this series circuit. When the switch element 34 is turned on at, the current of the inductor 26 flows through the capacitor 48 to the transformer 27.
When the capacitor 48 starts to have a voltage as it flows through the control winding and the primary winding 28 and the switch element 34, and the voltage becomes higher than the voltage of the smoothing capacitor 32, the current of the inductor 26 becomes -Through the contact 49 and into the smoothing capacitor 32. That is, although the switch element 34 is turned on, the inductor 26
The boosting time becomes shorter as the input voltage Vin (4) becomes higher. Further, while the switch element 34 is off, the current of the inductor 26 is the diode 4
9 through the smoothing capacitor 32, and at the same time, the exciting current from the control winding of the transformer 27 flows through the capacitor 48 and the diode 49. Is charged in the opposite direction and the voltage drops. That is, in this embodiment, since the boosting time of the inductor 26 becomes shorter as the input voltage Vin (4) becomes higher, the current of the inductor 26 becomes smaller than that of the switch element 3.
Even when the mode is a continuous mode in which 4 does not return to zero amperes during the off period, the input current waveform Iin (4) becomes a waveform substantially corresponding to a sine wave and the power factor is high.

(11) FIG. 6 is a circuit example of another embodiment of the present invention. In this example,
A series circuit of the first switch element 51, the primary winding 28 of the transformer 27, and the second switch element 52 from the positive side of the smoothing capacitor 32 is connected between the terminals of the smoothing capacitor. The connection point between the switch element 51 and the primary winding 28 of the transformer 27, and the smoothing capacitor 3
The first diode 54 is connected to the negative side of 2, and between the connection point between the primary winding 28 of the transformer 27 and the second switch element 52 and the positive side of the smoothing capacitor 32. This is the point where the second diode 53 is connected. In this circuit example, the first switch element 51 and the second switch 52 are always turned on or off at the same time, so that the smoothing capacitor 3 is turned on while the two switches are on.
The voltage of 2 is applied to the primary winding of the transformer 27, and the energy of the smoothing capacitor 32 is sent from the primary winding 28 of the transformer 27 to the load 40 via the secondary winding 29 and the rectifying / smoothing circuit 35. . At the same time, the current of the inductor 26 flows from the quaternary winding 31 of the transformer 27 through the first switch element 51, the primary winding 28 of the transformer 27, and the second switch element 52. On the other hand, when the switching elements 51 and 52 are off, the excitation energy of the transformer
Is sent to the smoothing capacitor 32 from both terminals of the primary winding 28 of the transformer 27 via the first diode 54 and the second diode 53, between the terminals of the smoothing capacitor 32. To be The current of the inductor 26 is
Smoothing capacitor 3 via control winding 31 of transformer 27
2 and at the same time, a current flows through the control winding 31 of the transformer 27.
It flows from the primary winding 28 of No. 7 to the smoothing capacitor 32 through the first diode 54 and the second diode 53.

[0019]

As described above, according to the present invention, the switching element 34 is used in comparison with the conventional AC input switching power supply.
In addition, the control circuit 41 can easily increase the power factor as it is, and further, the voltage of the smoothing capacitor 32 can be set lower than that of the second configuration of the conventional AC input switching power supply. Since it is possible to use a switching element having a low withstand voltage and a small on-resistance, it is possible to improve the efficiency of the switching power supply.

[Brief description of drawings]

 FIG. 1 Circuit diagram of one embodiment of the present invention FIG. 2 Circuit diagram of another embodiment of the present invention FIG. 3 Circuit diagram of another embodiment of the present invention FIG. 4 Circuit diagram of another embodiment of the present invention Circuit diagram of the embodiment FIG. 6 Circuit diagram of another embodiment of the present invention FIG. 7 Operation waveform diagram of each part of the embodiment of the present invention (FIG. 1) FIG. 8 Conventional circuit diagram FIG. 9 Conventional circuit diagram FIG. Operation waveform diagram Fig. 11 Operation waveform diagram of each part of the conventional circuit (Fig. 9)

[Explanation of symbols]

 2, 21 Full-wave rectifier 16, 26, 38 Inductor 8, 27 Transformer 28 Primary winding 29 Secondary winding 30 Third winding 31 Control winding 32 Smoothing capacitor 11, 17, 34 Switch element 35 Rectifying and smoothing circuit 40 load

Claims (6)

[Claims] 1. A smoothing capacitor is connected between the output terminals of a full-wave rectifier connected to an AC power source, and a primary winding of a transformer and a series circuit of a switching element are connected between the terminals of the smoothing capacitor. The secondary winding of the rectifying and smoothing circuit is connected to supply electric power to the load connected between the output terminals of the rectifying and smoothing circuit, and at the same time, the output voltage of the rectifying and smoothing circuit is detected to become a predetermined voltage. As described above, in a switching power supply including a control circuit for controlling the switch element, an inductor and a control winding of the transformer are connected in series between the full-wave rectifier and the smoothing capacitor. . 2. The switching power supply according to claim 1, wherein a capacitor is connected between the terminals of the switch element. 3. The switching power supply according to claim 1, wherein a capacitor is provided in series with the control winding, and a diode is connected in parallel to the series circuit of the control winding and the capacitor. 4. A series circuit of a first switching element, a primary winding and a second switching element is connected between terminals of a smoothing capacitor, and a connection point between the first switching element and the primary winding is connected. A first diode is connected between the minus side of the smoothing capacitor, and a second diode is provided between the connection point between the primary winding and the second switch element and the plus side of the smoothing capacitor. The switching power supply according to claim 1, wherein a diode is connected. 5. A smoothing capacitor is connected between the output terminals of a full-wave rectifier connected to an AC power source, and a primary circuit of a transformer and a series circuit of a switching element are connected between the terminals of the smoothing capacitor, and the transformer is connected. The secondary winding of the rectifying and smoothing circuit is connected to supply electric power to the load connected between the output terminals of the rectifying and smoothing circuit, and at the same time, the output voltage of the rectifying and smoothing circuit is detected to become a predetermined voltage. As described above, in the switching power supply equipped with the control circuit for controlling the switch element, the 3 (2) secondary winding of the transformer is connected between the terminals of the smoothing capacitor via the diode, and the full-wave rectifier and the smoother are connected. A switching power supply characterized in that an inductor and a control winding of the transformer are connected in series between a capacitor. 6. The switching power supply according to claim 5, wherein a series circuit of a tertiary winding of the transformer and a diode is connected between the output terminals of the rectifying and smoothing circuit.