JP3291864B2 - 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 switching power supply for supplying a stabilized DC voltage to industrial and consumer electronic equipment.

[0002]

2. Description of the Related Art In recent years, switching power supply devices have been strongly required to be thinner and more efficient as electronic devices have become smaller and more sophisticated.

A conventional switching power supply will be described below. FIG. 3 shows a conventional switching power supply device.
This is a so-called full-bridge switching power supply device. In FIG. 3, reference numeral 1 denotes an input DC power supply for smoothing an AC voltage or a battery or the like.
An input voltage is supplied to the input terminals 2a and 2b, a positive voltage is connected to the input terminal 2a, and a negative voltage is connected to the input terminal 2b. Reference numerals 21 and 22 denote first and second switching means for connecting a series circuit of the first switching means 21 and the second switching means 22 to both ends of the input DC power supply 1. Reference numerals 23 and 24 denote third and fourth switching means for connecting a series circuit of the third switching means 23 and the fourth switching means 24 to both ends of the input DC power supply 1. The first switching means 21 and the fourth switching means 24 repeat on / off in synchronization with each other, the second switching means 22 and the third switching means 23 repeat on / off in synchronization with each other, and the first switching means 2
The first and second switching means 22 have a period in which they are simultaneously turned off and are alternately turned on and off, and the third switching means 23 and the fourth switching means 24 also have a period in which they are simultaneously turned off and are turned on and off alternately. .

Reference numeral 10 denotes a transformer, which is a primary winding 10a, 2
The transformer 10 has a primary winding 10b and a secondary winding 10c. One end of the primary winding 10a of the transformer 10 is connected to a connection point between the first switching means 21 and the second switching means 22. Is connected to a connection point between the third switching means 23 and the fourth switching means 24.

Reference numeral 11 denotes a first rectifier diode, and a second rectifier diode
Switching means 22 and third switching means 23
Is turned on, a voltage generated in the secondary winding 10b and the secondary winding 10c of the transformer 10 is applied to one end of the inductance element 13. 12 is a second rectifier diode,
When the first switching means 21 and the fourth switching means 24 are on, the voltage generated in the secondary winding 10b and the secondary winding 10c of the transformer 10 is applied to the inductance element 1
3 to one end.

[0006] The inductance element 13 supplies current to the output terminals 15a and 15b by averaging the voltage generated by the first rectifier diode 11 and the second rectifier diode 12. Reference numeral 14 denotes a smoothing capacitor, and an output terminal 1
It is connected between 5a and 15b and holds the voltage averaged by the inductance element 13. A control circuit 25 detects the voltages of the output terminals 15a and 15b and changes the on / off ratio of the first to fourth switching means 21, 22, 23 and 24 so as to keep the output voltage constant.

The operation of the conventional switching power supply device configured as described above will be described in detail with reference to FIG. 4A to 4F show operation waveforms of respective parts of the conventional switching power supply device of FIG. 3, wherein FIG. 4A shows on / off signals _Vg1 and _Vg4 of the control circuit 16, and FIG. and on-off signal V _g2 and V _g3 of the circuit 16, (c) is a voltage waveform V ₁ and V ₄ is applied to the first switching means 21 to the fourth switching means 24, (d) the second Switching means 22 and third switching means 23
The voltage waveform V ₂ and V ₃ applied to, (e) is a voltage waveform Vs to be applied to one end of the inductance element 13, a (f) is a current waveform Is flowing through the inductance element 13.

[0008] indicates the t ₁ to indicate a temporal change of the operating state t ₅ in FIG. At time t ₁ , when the first switching means 21 and the fourth switching means 24 are turned off and the second switching means 22 and the third switching means 23 are turned on by the on / off signal of the control circuit 25, the primary winding of the transformer 10 is turned on. The input voltage Vin is applied to the line 10a.
Is applied to the secondary winding 10b and the secondary winding 10c of the transformer 10 (where n is the winding ratio of the primary winding to the secondary winding, and the number of primary windings: secondary windings). (Number of lines = n: 1)
And the first rectifier diode 11 is turned on. When the first rectifier diode 11 is turned on, the second rectifier diode 12 is turned off, and at this time, a voltage of Vin / n-Vout is applied to the inductance element 13.

At time t ₂ , when the first switching means 21 and the fourth switching means 24 are turned off and the second switching means 22 and the third switching means 23 are turned off by the on / off signal of the control circuit 25, the inductance element 13 is turned off. Since the first and second rectifier diodes are turned on so that the current flowing through the transformer 10 is continuous, the voltage of each winding of the transformer 10 becomes 0, and the voltage of −Vout is applied to the inductance element 13.

At time t ₃ , when the second switching means 22 and the third switching means 23 are turned off and the first switching means 21 and the fourth switching means 24 are turned on by the on / off signal of the control circuit 25, the transformer 1 is turned on.
0 is applied to the primary winding 10a, and -Vin / n is applied to the secondary winding 10b and the secondary winding 10c of the transformer 10.
And the second rectifier diode 12 is turned on. When the second rectifier diode 12 is turned on, the first rectifier diode 11 is turned off. At that time, a voltage of Vin / n-Vout is applied to the inductance element 13.

At time t ₄ , when the second switching means 22 and the third switching means 23 are turned off and the first switching means 21 and the fourth switching means 24 are turned off by the on / off signal of the control circuit 25, the inductance element 13 is turned off. Since the first rectifier diode 11 and the second rectifier diode 12 are turned on so that the current flowing through the transformer becomes continuous, each winding voltage of the transformer becomes 0,
A voltage of −Vout is applied to the inductance element 13.

[0012] time t by off signal ₅ in the control circuit 25 first switching means 21 and the fourth switching means 24 is turned off, the second switching means 22 and the third switching means 23 is turned on, transformer 1
The input voltage Vin is applied to the 0 primary winding 10a.
Repeat this.

From the reset condition for preventing the inductance element 13 from magnetic saturation, the first switching means 21
And the simultaneous on-period of the fourth switching means 24 and the simultaneous on-period of the second switching means 22 and the third switching means 23 are equal, and the period is Ton, and the primary winding voltage of the transformer 10 is zero. Is Toff,
The output voltage Vout is as follows: Vout = (Vin / n × Ton) / (Ton + Toff) The output voltage can be controlled by changing the on / off ratio.

[0014]

However, in the above-mentioned conventional configuration, the input voltage Vin is applied when each of the switching means is off, so that a large and high withstand voltage switching means must be selected. In addition, each of the switching means has a problem in that energy loss occurs due to short-circuiting of a parasitic capacitance existing in the switching means at the time of turn-on, and the efficiency is reduced accordingly.

The present invention solves the above-mentioned conventional problems. By reducing the voltage applied when each switching means is turned off to approximately half of the input voltage, it is possible to use a small-sized and low withstand voltage switching means. Another object of the present invention is to provide a highly efficient switching power supply by performing zero voltage switching on all switching means.

[0016]

In order to achieve this object, a switching power supply according to the present invention comprises a first circuit in which at least a series circuit of first and second capacitors is connected to an input voltage, and the first and second capacitors alternately turn on and off alternately. A series circuit of a first capacitor and a second switching means is connected to both ends of the first capacitor;
A series circuit of third switching means and fourth switching means, which alternately turns on and off, is connected to both ends of the second capacitor, and a connection point between the first and second switching means is connected to the third switching means. Connecting a series circuit of a primary winding of a transformer having a primary winding and one or more secondary windings, and a third capacitor between the first winding and a connection point of the fourth switching means; A voltage induced in the secondary winding of the transformer is supplied to an output through a rectifying / smoothing means.

[0017]

With this configuration, when the first and fourth switching means are turned on, one ends of the second and third switching means are clamped to the voltage of Vin / 2 by the first and second capacitors. The voltage applied to the second and third switching means can be Vin / 2, and conversely, when the second and third switching means are on, the voltage applied to the first and fourth switching means is Vin / 2 It can be set to Vin / 2 by the first and second capacitors. Also, even when no voltage is applied to the primary winding of the transformer, the simultaneous ON period of the first switching means and the third switching means or the simultaneous ON period of the second switching means and the fourth switching means is set. With this arrangement, the continuity of the current in the primary winding of the transformer is maintained, a reverse current can flow when all the switching means are turned on, and even when parasitic capacitance exists in all the switching means, the charge is discharged. By turning on after that, zero voltage switching can be performed, and there is no energy loss at the time of turn-on, and the efficiency can be improved.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A switching power supply according to one embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes an input DC power supply for smoothing an AC voltage or comprising a battery or the like. The input voltage is supplied to input terminals 2a and 2b, and a positive voltage is applied to input terminal 2a. And the negative voltage is connected to the input terminal 2b. Reference numerals 3 and 4 denote a first capacitor and a second capacitor, which connect a series circuit of the first capacitor 3 and the second capacitor 4 to both ends of the input terminals 2a and 2b.

Reference numerals 6a and 7a denote first and second switching elements which are turned on and off by the control circuit 16.
And 18 are first and second parasitic diodes,
The first switching means 6 is constituted by the switching element 6a and the first parasitic diode 17, and the second switching means 7 is constituted by the second switching element 7a and the second parasitic diode 18. A series circuit of the first switching means 6 and the second switching means 7 is connected to both ends of the first capacitor 3. 8a and 9a are third and fourth switching elements which are turned on and off by the control circuit 16, 19 and 20 are third and fourth parasitic diodes, and the third switching element 8a and third parasitic diode 19 And constitute the third switching means 8,
Fourth switching element 9a and fourth parasitic diode 2
0 constitutes the fourth switching means 9. The series circuit of the third switching means 8 and the fourth switching means 9 is connected to both ends of the second capacitor 4, and the connection point of the first switching means 6 and the second switching means 7 A primary winding 10a of a transformer 10 is provided between the switching means 8 and a connection point of the fourth switching means 9.
And a third capacitor 5 in series.

Reference numeral 10 denotes a transformer, which is a primary winding 10a, 2
The transformer 10 has a primary winding 10b and a secondary winding 10c. One end of the primary winding 10a of the transformer 10 is connected to a connection point between the first switching means 6 and the second switching means 7, and the other end. Is connected to a connection point between the third switching means 8 and the fourth switching means 9.

Reference numeral 11 denotes a first rectifier diode,
When the switching means 6 and the fourth switching means 9 are turned on, the voltage generated in the secondary winding 10b and the secondary winding 10c of the transformer 10 is applied to one end of the inductance element 13. Reference numeral 12 denotes a second rectifier diode.
When the switching means 7 and the third switching means 8 are turned on, the voltage generated in the secondary winding 10b and the secondary winding 10c of the transformer 10 is applied to one end of the inductance element 13.

The inductance element 13 supplies current to the output terminals 15a and 15b by averaging the voltage generated by the first rectifier diode 11 and the second rectifier diode 12. Reference numeral 14 denotes a smoothing capacitor, and an output terminal 1
It is connected between 5a and 15b and holds a voltage averaged by the inductance element 13. A control circuit 16 alternately turns on and off the first switching element 6a and the second switching element 7a, and similarly turns on and off the third switching element 8a and the fourth switching element 9a. , 15b are detected,
The on / off timing of the first to fourth switching elements 6a, 7a, 8a, and 9a is changed so as to keep the output voltage constant.

The operation of the switching power supply of the present invention configured as described above will be described in detail with reference to FIG. 2A to 2H show operation waveforms of the switching power supply according to the embodiment of the present invention.
(A) is an on / off signal V _g1 to the first switching means 6 of the control circuit 16, and (b) is a second signal of the control circuit 16.
On / off signal V _g2 to the switching means 7 of
(C) is an on / off signal V _g3 to the third switching means 8 of the control circuit 16, and (d) is a fourth signal of the control circuit 16.
The on / off signal V _g4 to the switching means 9 of
(E) shows a current waveform I flowing through the first switching means 6.
_Qf , (f) is a current waveform _IQ2 flowing through the second switching means 7, (g) is current waveform _IQ3 flowing through the third switching means 8, and (h) is a fourth switching current. A current waveform _IQ4 flowing through the means 9 is shown.

The times t ₁ to t ₅ are shown in the figure to show the temporal change of the operating state. First switching means 6 is turned on by the on-off signal of the control circuit 16 at time t _1, the second
When the switching means 7 is turned off and the fourth switching means 9 is turned off, the primary winding 10a of the transformer 10
The continuity of the third switching means 8 causes the third parasitic diode 19 of the third switching means 8 to conduct, causing a current to flow in the opposite direction. At that time, the third switching means 8 is turned on. At this time, even if the current flowing through the third switching means 8 flows through the third switching element 8a, the third parasitic diode 1
The operation does not change even if it flows through 9. The primary winding 10a of the transformer 10 has the holding voltage V _C1 of the first capacitor 3 and the third voltage.
The voltage difference between the holding voltage V _C3 of the capacitor 5 and the voltage V _C1 is equal to the voltage V _C2 , as described later, and the primary winding 10a is affected by the leakage inductance of the primary winding 10a of the transformer 10. Is maintained.

When the first switching means 6 is turned off by the on / off signal of the control circuit 16 at time t ₂ ,
Transformer 1 is affected by the leakage inductance of transformer 10.
The current in the zero primary winding 10a is continuous, turning on the second parasitic diode 18 and then turning on the second switching means 7. At this time, the current flowing through the second switching means 7 is changed to the second switching element 7a.
The operation does not change whether the current flows through the second parasitic diode 18 or the second parasitic diode 18. The holding voltage V _C3 of the third capacitor 5 is applied to the primary winding of the transformer 10, the second rectifier diode 12 is turned on, and the current of the primary winding 10a of the transformer increases in the secondary winding 10c. Decrease by minutes. Transformer 10
Excitation energy decreases and takes a negative value. A secondary winding 10c of the transformer 10 is connected to one end of the inductance element 13.
Of the induced voltage V _C3 / n is applied.

At time t ₃ , when the second switching means 7 is turned off, the first parasitic diode 17 of the first switching means 6 conducts and a current flows in the opposite direction. Turn on. At this time, the operation does not change whether the current flowing through the first switching means 6 flows through the first switching element 6a or the first parasitic diode 17. The primary winding 10a of the transformer 10, as is the difference between the voltage of the holding voltage V _C3 of the holding voltage V _C2 of the second capacitor 4 third capacitor 5 is applied will be described later, the voltage V _C2 The voltage V _C3 becomes equal, and the current of the primary winding 10a maintains a constant value due to the influence of the leakage inductance of the primary winding 10a of the transformer 10.

At time t ₄ , when the third switching means 8 is turned off by the on / off signal of the control circuit 16,
Transformer 1 is affected by the leakage inductance of transformer 10.
The current in the primary winding 10a of 0 becomes continuous, turning on the fourth parasitic diode 20, and then turning on the fourth switching means 9. At this time, the operation is the same whether the current _IQ4 flowing through the fourth switching means 9 flows through the fourth switching element 9a or the fourth parasitic diode 20. The difference voltage between the input voltage Vin and the holding voltage V _C3 of the third capacitor is applied to the primary winding of the transformer 10, the first rectifier diode 11 is turned on, and the current of the primary winding 10a of the transformer is 2 It increases by the increment of the next winding 10b. The excitation energy of the transformer 10 increases and takes a negative value. The induced voltage V _C3 / n of the secondary winding 10c of the transformer 10 is applied to one end of the inductance element 13.

[0029] The on-off signal of the control circuit 16 at time t _5, when the fourth switching means 9 is turned off,
Third parasitic diode 19 of third switching means 8
Conducts, causing a reverse current to flow, at which time the third switching means 8 is turned on. Repeat this.

[0030] the duration of the period of the period from t ₁ to t ₂ the period from T _off1, t ₂ to t ₃ from T _on2, t ₃ to t ₄ from T _off2, t ₄ to t ₅ T _on1 Then, from the reset condition for preventing the transformer 10 from magnetic saturation, (Vin−V _C3 ) × T _on1 −V _C3 × T _on2 = 0, so that when T _on1 = T _on2 = Ton, V _C3 = Vin / 2. Becomes

The output voltage Vout is equal to the inductance element 1
From the reset condition to prevent magnetic saturation of
= T _off1 = When _{T off2 Vout = Ton × Vin /} (Ton + Toff) it is possible to control the output voltage by changing the next-off ratio.

The input voltage is divided by the holding voltages V _C1 and V _C2 of the first capacitor 3 and the second capacitor 4,
_{When C2} is high, the current waveform of each part becomes a waveform as shown by a dotted line in FIG.
V _C2 decreases because the current flowing out becomes larger than the current flowing into the connection point. Conversely, when V _C1 is low, it operates so that V _C1 increases. In the stable state, the current flowing into the connection point between the first capacitor 3 and the second capacitor 4 and the current flowing out must be equal, and V _C1 is Vin / 2
Must.

In this embodiment, when the first switching means 6 and the fourth switching means 9 are turned on, one ends of the second switching means 7 and the third switching means 8 are connected to the first capacitor 3 and the second switching means 8, respectively. Since the voltage is clamped to the voltage of Vin / 2 by the capacitor 4, the voltage applied to the second switching means 7 and the third switching means 8 is V
in / 2, and conversely, the second switching means 7 and the third
When the switching means 8 is turned on, the voltage applied to the first switching means 6 and the fourth switching means 9 is Vin by the first capacitor 3 and the second capacitor 4.
/ 2. In addition, all the switching elements are turned on when the parasitic diode is conducting and a current is flowing, so that zero-voltage switching is performed.

As described above, according to the present embodiment, the series circuit of the first and second capacitors is connected to the input voltage, and the series circuit of the first and second switching means that alternately turns on and off is connected to the first circuit. A series circuit of a fourth switching means connected to both ends of the first capacitor and repeating on and off in synchronization with the second switching means and a third switching means repeating on and off alternately with the fourth switching means. A primary winding and one or more primary windings are connected to both ends of the second capacitor and connected to a connection point between the first and second switching means and a connection point between the third and fourth switching means. A primary winding of a transformer having a secondary winding;
By providing a configuration in which a series circuit of a third capacitor is connected and supplying a voltage induced in the secondary winding of the transformer to an output through a rectifying and smoothing means, each switching means is applied. Voltage becomes half of the input voltage, and all the switching means perform zero voltage switching, so that there is no energy loss at the time of turn-on and the efficiency can be improved.

[0035]

As described above, according to the present invention, at least the series circuit of the first and second capacitors is connected to the input voltage, and the series circuit of the first and second switching means that alternately turns on and off alternately. A series circuit of third and fourth switching means connected to both ends of the first capacitor and alternately turned on and off is connected to both ends of the second capacitor, and the first and second switching means are connected to each other. , A primary winding of a transformer having a primary winding and one or more secondary windings between a connection point of the third and fourth switching means, and a third capacitor. And a configuration for supplying a voltage induced in the secondary winding of the transformer to an output through a rectifying / smoothing means. Of input voltage Min can turn, and all the switching means can realize efficient switching power supply device without energy loss at turn for doing the zero voltage switching.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a switching power supply device according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing the same operation.

FIG. 3 is a block diagram of a conventional switching power supply device.

FIG. 4 is a waveform chart showing the same operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Input DC power supply 2a, 2b Input terminal 3 1st capacitor 4 2nd capacitor 5 3rd capacitor 6 1st switching means 6a 1st switching element 7 2nd switching means 7a 2nd switching element 8th 3 switching means 8a third switching element 9 fourth switching means 9a fourth switching element 10 transformer 11 first diode 12 second diode 13 inductance element 14 smoothing capacitor 15a, 15b output terminal 16 control circuit 17th 1 parasitic diode 18 second parasitic diode 19 third parasitic diode 20 fourth parasitic diode 21 first switching means 22 second switching means 23 third switching means 24 fourth switching means 25 control circuit

Continuation of the front page (56) References JP-A-5-56638 (JP, A) JP-A-5-83940 (JP, A) JP-A-2-151266 (JP, A) JP-A-5-191972 (JP) , A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H02M 3/00-3/44

Claims (1)

(57) [Claims] 1. A series circuit of first and second switching means for connecting at least a series circuit of first and second capacitors to an input voltage and alternately turning on and off is connected to both ends of the first capacitor. A series circuit of a third switching means and a fourth switching means which alternately turns on and off is connected to both ends of the second capacitor, and a connection point of the first and second switching means, Between the third and the connection point of the fourth switching means,
A primary winding of a transformer having a secondary winding and one or more secondary windings, and a series circuit of a third capacitor, wherein a voltage induced in the secondary winding of the transformer is connected. A switching power supply for supplying an output via a rectifying / smoothing means.