JPH0678537A - Switching power supply equipment - Google Patents

Abstract

PURPOSE:To eliminate the generations of spike voltages and spike currents without deteriorating the fundamental characteristic of a Cuk converter, when operating the switches relative to a switching power supply equipment which supplies stabilized DC voltages to industrial and civilian electronic apparatuses. CONSTITUTION:A first switching means is provided, whereby, when it is switched on, an input voltage VIN is applied to a primary winding 3a of a first transformer 3, and concurrently, a difference voltage VC1-VC2, wherein VC1, VC2 are respectively the DC voltages having been held by first and second capacitors 6, 9, is applied to a primary winding 10a of a second transformer 10. Also, a scond switching means repeating ON-OFF operation alternately with the first switching means is provided, whereby, when it is switched on, a difference voltage VC1-VIN, wherein VC1 is the DC voltage having been held by the first capacitor 6 and VIN is the input voltage, is applied to the primary winding 3a of the first transformer 3, and concurrently, the DC voltage VC2 having been held by the second capacitor 9 is applied to the primary winding 10a of the second transformer 10.

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 device 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 smaller in size, more stable in output, and more efficient, as electronic devices have become lower in price, smaller in size, higher in performance, and more energy efficient.

A conventional switching power supply device will be described below. FIG. 15 shows a conventional switching power supply device, which is a so-called Cuk converter. In FIG. 15, reference numeral 1 denotes an input DC power source for smoothing an AC voltage by current, or a battery or the like. An input voltage is supplied to an input terminal 2-2 ′ and a positive voltage is connected to the input terminal 2. , A negative voltage is connected to the input terminal 2 '. An inductance element 22 has one end connected to the input terminal 2 and one end connected to the input terminal 2 ′ via the switching element 4. Reference numeral 4 denotes a switching element, which is turned on / off by an on / off signal of the control circuit 27 and applies or cuts off the input voltage to the inductance element 22. Reference numeral 6 denotes a capacitor, which holds a DC voltage, one end of which is connected to the connection point between the inductance element 22 and the switching element 4 and the other end of which is connected to the anode of the diode 23. Reference numeral 23 denotes a diode, the anode of which is connected to the connection point of the capacitor 6 and the inductance element 24 and the cathode of which is the output terminal 26-2.
It is connected to the positive terminal 26 of 6 '.

Reference numeral 24 is an inductance element, one end of which is an anode of the diode 23 and the other end of which is an output terminal 26-2.
It is connected to the negative terminal 26 'of 6'. The inductance element 22 and the inductance element 24 are coupled so that the ripple current can be concentrated in the inductance element 22 or the inductance element 24. Input terminal 2-
2'negative terminal 2'and output terminals 26-26 'positive terminal 26
Is connected. A smoothing capacitor 25 is connected between the output terminals 26 and 26 'and holds an output voltage.

A control circuit 27 has an output terminal 26-2.
The voltage between 6'is detected, and the on / off ratio of the switching element 4 is changed so as to keep the output voltage constant.

The operation of the switching power supply device configured as described above will be described in detail with reference to FIG.
16 (a) to 16 (g) show operating waveforms of each part of the conventional switching power supply device of FIG. 15, and FIG. 16 (a) is an on / off signal V _G of the control circuit 27 applied to the switching element 4, (B) is the current I _L1 flowing through the inductance element 22, (c) is the current I _L2 flowing through the inductance element 24, (d) is the voltage waveform V _DS applied to the switching element 4, (e) ) Is a current waveform I _Q flowing through the switching element 4, (f) is a voltage V _D applied to the diode 23, and (g) is a current waveform I _D flowing through the diode 23.

In order to show the change over time in the operating state, t ₁ to t ₃
Is shown in the figure. When it is turned on by the on / off signal V _G at time t ₁ , a spike current flows through the switching element 4 along with the voltage fluctuation of V _DS . This is due to the charging / discharging current to the distributed capacitance such as the line capacitance and the interlayer capacitance existing between the windings of the inductance element 22 and the inductance element 24, and the discharge current of the parasitic capacitance related to the switching element 4. This spike current causes an increase in noise, a decrease in reliability, and an increase in loss.

When the switching element 4 is turned on and V _DS becomes sufficiently small, the input voltage V _IN is applied to the inductance element 22 and at the same time, the DC voltage V _C and the output voltage V _OUT held in the capacitor 6 by the inductance element 24.
Difference voltage V _C −V _OUT of Switching element 4
The sum current of the current I _L1 flowing through the inductance element 22 and the current I _L2 flowing through the inductance element 24 flows through the inductor.
When the switching element 4 is turned off at time t ₂ , the diode 23 is turned on by the current flowing in the switching element 4, and the inductance element 22 receives the difference voltage between the input voltage V _IN and the voltage V _C held in the capacitor 6. V _C -V
_IN is applied and the output voltage V is applied to the inductance element 24.
_OUT is applied. When the switching element 4 is turned on at time t ₃ , V _IN is applied to the inductance element 22 and V _C −V _OUT is applied to the inductance element 24.
Repeat this.

Assuming that the ON period of the switching element 4 is T _ON and the OFF period is T _OFF , V _IN × T _ON = (V _C −V _IN ) × T _OFF and the inductance element 24 are reset from the reset condition of the inductance element 22. From the condition, (V _C −V _OUT ) × T _ON = V _OUT × T _{OFF and} V _C = V _IN + V _OUT V _OUT = (T _ON / T _OFF ) × V _IN can be derived.

Therefore, the output voltage V _OUT can be controlled by changing the on / off ratio of the switching element 4. Further, since the voltage V _C applied to the capacitor 5 is the sum of the input voltage and the output voltage, the switching element 4
When is on, the input voltage V _IN is applied to both ends of the inductance element 22 and the inductance element 24. When the switching element 4 is off, the inductance element 22
And the output voltage V
_OUT is applied. Therefore, the inductance element 22 and the inductance element 24 are coupled to each other, and the inductance value of the inductance element 4 is set to L ₁ and the inductance element 24.
Let L _{2 be} the inductance value of L, and let M ₁₂ be the mutual inductance value of them, by setting L ₁ = M ₁₂ , the current of the inductance element 24 can be zero ripple, and by setting L ₂ = M _12. It is possible to make the current of the inductance element 22 have zero ripple. The waveform shown in FIG. 16 is when the current of the inductance element 22 is zero ripple.

However, in such a configuration, the input voltage and the output voltage are inverting non-insulating type.

FIG. 17 shows a so-called insulated Cuk converter which is a conventional switching power supply device. 17, the same components as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted. In FIG. 17, 1 is an input DC power supply,
2'is an input terminal, 22 is an inductance element, 28 is a capacitor for holding a DC voltage, and 29 is a capacitor.
Is a transformer having a primary winding 29a and a secondary winding 29b.

Reference numeral 4 denotes a switching element, which applies an input voltage to the inductance element 22 when it is on, and at the same time, applies a DC voltage held in the capacitor 28 to the transformer 29.
Applied to the primary winding 29a. When turned off, the input DC voltage, the inductance element 22, the capacitor 28, and the primary winding 29a of the transformer 29 are connected so as to form a loop.

A diode 31 is connected to a secondary winding 29b of the transformer 29 via a capacitor 30 holding a DC voltage, and the transformer 2 is turned on when the switching element 4 is off.
9 is connected so that it is turned on by the voltage induced in the secondary winding 29b. 24 is an inductance element, one end of which is connected to the connection point of the capacitor 30 and the diode 31,
The other end is connected to the output terminal 26 '. The transformer 29, the inductance element 22, and the inductance element 24 are coupled to each other. 25 is a smoothing capacitor, which is the output terminal 2
Connected between 6-26 'to maintain and smooth the output voltage. 26
Reference numeral -26 'is an output terminal and 27 is a control circuit.

The operation of the switching power supply device configured as described above will be described in detail with reference to FIG.
18 (a) to 18 (i) show the operation waveforms of each part of the conventional switching power supply device of FIG. 17, and (a) show the ON / OFF signal V of the control circuit 27 applied to the switching element 4.
_G , (b) is a current waveform I _L1 flowing through the inductance element 22, (c) is a current waveform I _L2 flowing through the inductance element 24, and (d) is 1 of the transformer 29.
A current waveform I _P flowing through the primary winding 29a, (e) is a current waveform I _S flowing through the secondary winding 29b of the transformer 29, (f) is the voltage waveform V _DS applied to the switching element 4 Yes, (g) is the current waveform I _Q flowing through the switching element 4, (h) is the voltage waveform V _D applied to the diode 31, and (i) is the current waveform I _D flowing through the diode 31.

In order to show the temporal change of the operating state, t ₁ to t ₃
Is shown in the figure. When the switching element 4 is turned on by the on / off signal V _G at time t ₁ , a spike current flows through the switching element 4 in accordance with the voltage fluctuation of V _DS . This is due to the charging / discharging current to the distributed capacitance such as the line capacitance and the interlayer capacitance existing between the windings of the transformer 29, the inductance element 22 and the inductance element 24, and the discharge current of the parasitic capacitance related to the switching element 4. . This spike current causes an increase in noise, a decrease in reliability, and an increase in loss.

When the switching element 4 is turned on and V _DS becomes sufficiently small, the input voltage V _IN is applied to the inductance element 22 and, at the same time, the primary winding 29a of the transformer 29.
The DC voltage V _C1 held in the capacitor 28 is applied to the. At this time, the diode 31 is connected so as to be off.

When the switching element 4 is turned off by the on / off signal V _G at time t ₂ , a spike voltage is generated due to the leakage inductance of the transformer 29. The generation of this spike voltage causes noise and loss.

When the switching element 4 is turned off, the diode 31 is turned on, the output voltage V _OUT is applied to the inductance element 24, and the secondary winding 29 of the transformer 29 is applied.
The DC voltage V _C2 held in the capacitor 30 is applied to b. When the switching element 4 is turned on at time t ₃ , V _IN is applied to the inductance element 22 and V _C2- V _OUT is applied to the inductance element 24. Repeat this.

Transformer 2 when switching element 4 is off
When the voltage induced in the primary winding 29a of the coil 9 is V _OFF and the ON period of the switching element 4 is T _ON and the OFF period is T _OFF , V _IN × T _ON = (V _C1 −V _IN −V _OFF ) × T _{OFF Because} of the reset condition of the transformer 29, V _C1 × T _ON = V _OFF × T _OFF , so that V _C1 becomes V _C2 = V _{OUT in the} same consideration as V _C1 = V _IN . Primary winding 29a and secondary winding 29 of transformer 29
When the turns ratio of b is n: 1, the output voltage becomes V _OUT = n × V _OFF = n × (T _ON / T _OFF ) × V _IN , and the output voltage can be controlled by changing the on / off ratio of the switching element 4. It is possible.

The inductance value of the primary winding 29a of the transformer 29 is L _P , the inductance value of the secondary winding 29b of the transformer 29 is L _S , and the primary winding 29a of the transformer 29 is
When mutual inductance M _PS between the secondary winding 29 b, the mutual inductance M _1P of the primary winding 29a and the inductance element 22 of the transformer 29, mutual inductance between primary winding 29a and the inductance element 24 of the transformer 29 _Is M _2P , the mutual inductance between the secondary winding 29b of the transformer 29 and the inductance element 22 is M _1S , and the mutual inductance between the secondary winding 29b of the transformer 29 and the inductance element 24 is M _2S , then L _P = M By setting _1P L _S = M _2S M _PS = M _1S = M _2P , the ripple current can be concentrated in the primary winding 29a and the secondary winding 29b of the transformer 29, and the input / output current can be reduced. Can be zero ripple.

However, the conventional configuration has a problem that spike voltage and spike current are generated due to switching.

[0023]

However, in the structure of the conventional Cuk converter described above, if the insulation type is used, a spike current at the time of turn-on of the switching element 4 and a spike voltage at the time of turn-off of the switching element 4 are generated, so that the conversion efficiency is lowered and There was a problem that the regulation deteriorated at the time of other output.

It is an object of the present invention to eliminate the above-mentioned conventional drawbacks and to provide a switching power supply device capable of reducing the input current to zero ripple without generating spike current and voltage.

[0025]

To solve this problem, a switching power supply device according to the present invention comprises a first transformer having at least a primary winding and one or more secondary windings, and
A second transformer having a secondary winding and one or more secondary windings, a first capacitor for holding a DC voltage, a second capacitor for holding a DC voltage, and ON / OFF repeatedly turned on The input voltage at the time of 1 of the first transformer
A second voltage applied to the primary winding of the second transformer at the same time as a differential voltage applied to the secondary winding and a DC voltage retained in the first capacitor and a DC voltage retained in the second capacitor; 1 switching means and this first switching means are repeatedly turned on and off alternately, and when turned on, the difference voltage between the direct current voltage and the input voltage held in the first capacitor is changed to the primary winding of the first transformer. To the primary winding of the second transformer, and at the same time to apply the DC voltage held in the second capacitor to the primary winding of the second transformer, the first transformer or the second transformer. Alternatively, the voltage induced in both of the secondary windings is supplied to the output via the rectifying / smoothing means.

[0026]

With this configuration, when the first and second switching means are turned on, the energy stored in the parasitic capacitor of the switching means and the distributed capacitance of the transformer is discharged and then turned on, so that no spike current is generated. When the first and second switching means are turned off, no spike voltage is generated due to the influence of the leakage inductance of the transformer. Another feature is that the input current can be zero ripple.

[0027]

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the configuration of a switching power supply device according to a first embodiment of the present invention. In FIG. 1, the same parts as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 1 is an input DC power supply, 2-2 'is an input terminal, 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b. One end of the wire 3a is connected to the input terminal 2 and the other end is connected to the input terminal 2'through the switching element 4, and the secondary winding 3b is a rectifying diode 11
Is connected to the output terminal 13-13 'through. A switching element 4 is turned on / off by the control circuit 17. Reference numeral 5 denotes a diode, and the switching element 4 and the diode 5 constitute a first switching means.

Reference numeral 6 is a capacitor for holding a DC voltage, 7 is a switching element, which is turned on and off by the control circuit 17 and is turned on when the switching element 4 is off, and the input voltage and the capacitor 6 are applied to the primary winding 3a of the transformer 3. The differential voltage of the DC voltage held by is applied. Reference numeral 8 denotes a diode, and the switching element 7 and the diode 8 constitute second switching means. Reference numeral 9 denotes a capacitor that holds a DC voltage, and is connected to both ends of the switching element 7 via the primary winding 10a of the transformer 10. Reference numeral 10 is a transformer, which includes a primary winding 10a and one or more secondary windings 10b.
And the secondary winding 10b is connected to the second output terminals 16-16 'through the rectifying diode 14.

Reference numeral 11 is a rectifying diode, and 12 is a smoothing capacitor. The rectifying diode 11 and the smoothing capacitor 12 constitute a first rectifying and smoothing means, and rectify and smooth the induced voltage of the secondary winding 3b of the transformer 3. Output terminal 13-
Supply voltage to 13 '. 13-13 'is a first output terminal. Reference numeral 14 is a rectifying diode, 15 is a smoothing capacitor, and the rectifying diode 14 and the smoothing capacitor 15 constitute a second rectifying and smoothing means, which rectifies and smoothes the induced voltage of the secondary winding 10b of the transformer 10 and outputs it. Terminal 16
Supply voltage to -16 '. 16-16 'is a second output terminal. Reference numeral 17 is a control circuit, which is an output terminal 16-1.
A voltage between 6'is detected and a control signal for changing the on / off ratio of the switching element 4 and the switching element 7 is generated so that the output voltage becomes constant.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 2, (a) shows the switch of the control circuit 17.
Driving pulse waveform V of the switching element 4 _G1Shows,
(B) is a drive pulse of the switching element 7 of the control circuit 17.
Waveform V_G2(C) is the primary winding of the transformer 3.
Line current I_L1(D) shows the primary of the transformer 10.
Winding current I_L2And (e) is the first switch
Voltage V applied to the_DS1And (f) is
Current I flowing through the first switching means_Q1Shows
Where (g) is the voltage applied to the second switching means.
V_DS2And (h) is the second switching means.
Current I flowing through_Q2(I) is a rectifier
Current I flowing through_D1(J) is a rectifier
Current I flowing through the ion 14_D2Is shown.

In order to show the change of the operating state with time, t ₁ to t ₃
Is shown in the figure. At time t ₁ , when the switching element 4 is turned on by the ON signal of the control circuit 17 and the switching element 7 is turned off at the same time, the input voltage V _IN is applied to the primary winding 3 a of the transformer 3, and at the same time the primary winding of the transformer 10 is applied. 10a, the difference voltage V _C1 − between the DC voltage V _C1 held by the capacitor 6 and the DC voltage V _C2 held by the capacitor 9 −
V _C2 is applied. At this time, the rectifying diode 11 connected to the secondary winding 3b of the transformer 3 and the transformer 2
The rectifier diode 14 connected to the next winding 10b is connected so as to be off. Primary winding 3 of transformer 3
The current I _{L1 of “a”} and the current of the primary winding 10 a of the transformer 10 linearly increase, and the exciting energy is accumulated in the transformer 3 and the transformer 10.

When the switching element 4 is turned off by the off signal of the control circuit 17 at time t ₂ , the current flowing through the switching element 4 turns on the diode 8. At the same time, the switching element 7 is turned on by the ON signal of the control circuit 17, but there is no change in the operation regardless of whether the ON current _IQ2 flows through the diode 8 or the switching element 7. When the diode 8 or the switching element 7 is turned on, the input voltage V _IN and the differential voltage V _C1 −V _{IN of the} DC voltage V _C1 held in the capacitor 6 are applied to the primary winding 3 a of the transformer 3, and at the same time, the transformer 10 The DC voltage V _C2 held in the capacitor 9 is applied to the primary winding 10a.

At this time, the rectifying diode 11 connected to the secondary winding 3b of the transformer 3 is turned on, and the output terminal 13-
Current is supplied to 13 '. Further, the rectifying diode 14 connected to the secondary winding of the transformer 10 is also turned on, and the current is also supplied to the output terminals 16-16 '. At this time, the current I _Q2 flowing through the second switching means decreases the excitation energy of the transformer 3 and the transformer 10 and reduces the transformer 3's 2
As the output current emitted from the secondary winding 3b increases and the output current emitted from the secondary winding 10b of the transformer 10 increases, the output current gradually decreases and becomes a negative value.

When the switching element 7 is turned off by the OFF signal of the control circuit 17 while a negative current is flowing in the switching element 7, this current turns on the diode 5. At the same time, the switching element 4 is turned on by the ON signal of the control circuit 17, but the operation does not change even if the current _IQ1 flowing through the first switching means flows through the switching element 4 or the diode 5. When the switching element 4 is turned on and the switching element 7 is turned off at the same time, the input voltage V _IN is applied to the primary winding 3a of the transformer 3, and at the same time, the DC voltage held by the capacitor 6 is applied to the primary winding 10a of the transformer 10. A differential voltage V _C1 −V _C2 between V _c1 and the DC voltage V _c2 held by the capacitor 9 is applied.
This operation is repeated.

When the ON period of the switching element 4 is T _ON and the OFF period is T _OFF , V _IN × T _ON = (V _C1 −V _IN ) × T _OFF is established depending on the reset condition of the transformer 3, and the reset condition of the transformer 10 is established. Therefore, (V _C1 −V _C2 ) × T _ON = V _C2 × T _OFF . When V _C1 and V _C2 are _calculated from the above, V _C1 = (T _ON + T _OFF ) / T _OFF × V _IN V _C2 = T _ON / T _OFF × V _IN

Primary winding 3a and secondary winding 3b of transformer 3
The output terminal 13 has a turn ratio of n ₁ : 1 and a turn ratio of the primary winding 10 a and the secondary winding 10 b of the transformer 10 n ₂ : 1.
The output voltage V _OUT1 of −13 ′ is V _OUT1 = (V _C1 −V _IN ) / n ₁ = T _ON / T _OFF / n ₁ × V _IN The output voltage V _OUT2 of the output terminal 16-16 ′ is V _OUT2 = − V _C2 / n ₂ = T _ON / T _OFF / n ₂ × V _IN , and V _OUT1 and V _OUT2 are proportional output voltages.
The output voltage can be controlled by the on / off ratio of the switching element 4 and the switching element 7. In this configuration, the switching element 4 caused by the leakage inductance of the transformer
Further, the spike voltage at the time of turning off the switching element 7 is effectively absorbed by the capacitors 6 and 9 as the diodes 5 and 8 are turned on, and the spike voltage is not generated.

Further, since the two outputs are taken out from separate transformers, the exciting current of the transformer is also small, and the inductance value can be made relatively large. This is advantageous in increasing the frequency.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows the configuration of the switching power supply device according to the second embodiment of the present invention. In FIG. 3, the same parts as those in FIG.

Reference numeral 1 is an input DC power source, 2-2 'is an input terminal, and 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b. A switching element 4 is turned on / off by the control circuit 17. Reference numeral 5 denotes a diode, and the switching element 4 and the diode 5 constitute a first switching means.

Reference numeral 6 is a capacitor for holding a DC voltage, 7 is a switching element, 8 is a diode, and the switching element 7 and the diode 8 constitute a second switching means. Reference numeral 9 is a capacitor for holding a DC voltage, 10 is a transformer, which has a primary winding 10a and one or more secondary windings 10b. Reference numeral 11 is a rectifying diode, 12 is a smoothing capacitor, the rectifying diode 11 and the smoothing capacitor 12 constitute a first rectifying and smoothing means, and 13-13 'is a first output terminal. Reference numeral 14 is a rectifying diode, 15 is a smoothing capacitor, the rectifying diode 14 and the smoothing capacitor 15 constitute a second rectifying and smoothing means, and 16-16 'is a second output terminal. A control circuit 17 detects the voltage between the output terminals 16 and 16 'and generates a control signal for changing the on / off ratio of the switching element 4 and the switching element 7 so that the output voltage becomes constant.

Reference numeral 18 denotes a capacitor, which is connected to both ends of the switching element 4 and suppresses a sharp change in the voltage applied to the switching element 4 and the switching element 7. The switching element 4 and the switching element 7
The ON / OFF signal of the control circuit 17 is set so as to have an OFF period at the same time.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 4, (a) shows the switch of the control circuit 17.
Driving pulse waveform V of the switching element 4 _G1Shows,
(B) is a drive pulse of the switching element 7 of the control circuit 17.
Waveform V_G2(C) is the primary winding of the transformer 3.
Line current I_L1(D) shows the primary of the transformer 10.
Winding current I_L2And (e) is the first switch
Voltage V applied to the_DS1And (f) is
Current I flowing through the first switching means_Q1Shows
Where (g) is the voltage applied to the second switching means.
V_DS2And (h) is the second switching means.
Current I flowing through_Q2(I) is a rectifier
Current I flowing through_D1(J) is a rectifier
Current I flowing through the ion 14_D2Is shown.

The basic operation is the same as the circuit configuration of the first embodiment, but the switching element 4 and the switching element 7 have an off period at the same time, and the switching element 4 and the switching element 7 are applied during that period. Voltage is set to change. Since the capacitors 18 are connected to both ends of the switching element 4, turn-off of the switching element 4 and sharp rise and fall of the voltage waveform at the time of turn-off are alleviated, and the capacitor 1
Since the switching element 4 can be turned on after the charge stored in 8 is regenerated to the input DC power source 1, there is no turn-off loss of the switching element 4. The switching element 7 has a similar effect.

The operation other than the transition is the same as that of the embodiment described with reference to FIG. Further, when these capacitors 18 are added, the output impedance of each winding of the transformer 3 changes at the time of transition, and especially the initial current value of each winding current when the switching element 4 is turned off changes, but this has an effect on the control operation itself. Since the voltage waveforms applied to the switching elements 4 and 7 are not steep, the generation of noise is suppressed and the switching loss of the switching elements 4 and 7 is also suppressed. Further, in this configuration, the spike voltage at the time of turning off the switching elements 4 and 7 due to the leakage inductance of the transformer is effectively absorbed by the capacitors 6 and 9 by turning on the diodes 5 and 8, and the spike voltage There is no occurrence.

Further, since the two outputs are taken out from different transformers, the exciting current of the transformer is also reduced and the inductance value can be relatively increased. This is advantageous in increasing the frequency.

(Embodiment 3) A third embodiment of the present invention will be described below with reference to the drawings. FIG. 5 shows the configuration of a switching current device according to the third embodiment of the present invention. 5, the same components as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 1 is an input DC power supply, 2-2 'is an input terminal, and 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b. A switching element 4 is turned on / off by the control circuit 17. Reference numeral 5 denotes a diode, and the switching element 4 and the diode 5 constitute a first switching means.

Reference numeral 6 is a capacitor for holding a DC voltage, 7 is a switching element, 8 is a diode, and the switching element 7 and the diode 8 constitute the second switching means. Reference numeral 9 is a capacitor for holding a DC voltage, 10 is a transformer, which has a primary winding 10a and one or more secondary windings 10b. Reference numeral 11 is a rectifying diode, 12 is a smoothing capacitor, the rectifying diode 11 and the smoothing capacitor 12 constitute a first rectifying and smoothing means, and 13-13 'is a first output terminal. Reference numeral 14 is a rectifying diode, 15 is a smoothing capacitor, the rectifying diode 14 and the smoothing capacitor 15 constitute a second rectifying and smoothing means, and 16-16 'is a second output terminal. A control circuit 17 detects the voltage between the output terminals 16 and 16 'and generates a control signal for changing the on / off ratio of the switching element 4 and the switching element 7 so that the output voltage becomes constant.

Reference numeral 19 is a leakage inductance or an inductance element, which is connected in series to the primary winding 3a of the transformer 3 and is connected to the capacitor 6 during the ON period of the switching element 7.
The output current that resonates with and is transmitted to the secondary winding 3b of the transformer 3 is used as a resonance current. Reference numeral 20 denotes a leakage inductance or an inductance element, which is connected in series to the primary winding 10a of the transformer 10 and resonates with the capacitor 9 during the ON period of the switching element 7, and the secondary winding 10 of the transformer 10.
The output current transmitted to b is the resonance current.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 6, (a) shows the switch of the control circuit 17.
Driving pulse waveform V of the switching element 4 _G1Shows,
(B) is a drive pulse of the switching element 7 of the control circuit 17.
Waveform V_G2(C) is the primary winding of the transformer 3.
Line current I_L1(D) shows the primary of the transformer 10.
Winding current I_L2And (e) is the first switch
Voltage V applied to the_DS1And (f) is
Current I flowing through the first switching means_Q1Shows
Where (g) is the voltage applied to the second switching means.
V_DS2And (h) is the second switching means.
Current I flowing through_Q2(I) is a rectifier
Current I flowing through_D1(J) is a rectifier
Current I flowing through the ion 14_D2Is shown. Operating condition
T to show the change over time₁~ T₆Is shown in the figure.

The basic operation is the same as the circuit configuration of the first embodiment.
The same, but the switching element 7 turns on and the output
When supplying current, the capacitor 6 and the leakage inductor
Or the inductance element 19 resonates and the resonance frequency
Is set to be sufficiently small that the secondary winding of transformer 3
Line current I_D1Becomes sinusoidal and rises from zero, t _Four
It becomes zero again. Therefore, the rectifier diode 11 is zero
It becomes current switching and recovery does not occur. Similarly,
Capacitor 9 and leakage inductance or inductor
Element 20 resonates, and the resonance frequency is set to be sufficiently small.
Therefore, the secondary winding current I of the transformer 10_D2Is a sine wave
And rise from zero, t₂It becomes zero again.
Therefore, the rectifier diode 14 does not perform zero current switching.
Recovery does not occur. The input current should be continuous.
It is possible with and.

Since the operation other than the transient operation is the same as that of the embodiment described with reference to FIG. 1, the description thereof will be omitted.

Further, there is an effect that the turn-off currents of the switching elements 4 and 7 can be reduced and the switching loss can be reduced.

Although the DC voltage V _C is actually the sum of the DC voltage and the fluctuation which is the resonance voltage, the fluctuation due to the resonance voltage can be set to be sufficiently small, so that the conversion ratio of the input voltage and the output voltage is the same as that of the first embodiment. It is almost the same as the case of.

Further, in this configuration, the spike voltage at the turn-off of the switching element 4 and the switching element 7 due to the leakage inductance of the transformer is the diode 5.
Also, when the diode 8 is turned on, it is effectively absorbed by the capacitors 6 and 9, and no spike voltage is generated.

Further, since the two outputs are taken out from separate transformers, the exciting current of the transformer is also small, and the inductance value can be made relatively large. This is advantageous in increasing the frequency.

(Embodiment 4) A fourth embodiment of the present invention will be described below with reference to the drawings. FIG. 7 shows the configuration of a switching power supply device according to the third embodiment of the present invention. 7, the same components as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 1 is an input DC power supply, 2-2 'is an input terminal, and 3 is a first transformer having a primary winding 3a and one or more secondary windings 3b. A switching element 4 is turned on / off by the control circuit 17. Reference numeral 5 denotes a diode, and the switching element 4 and the diode 5 constitute a first switching means.

Reference numeral 6 is a capacitor for holding a DC voltage, 7 is a switching element, 8 is a diode, and the switching element 7 and the diode 8 constitute a second switching means. Reference numeral 9 is a capacitor for holding a DC voltage, 10 is a transformer, which has a primary winding 10a and one or more secondary windings 10b. Reference numeral 11 is a rectifying diode, 12 is a smoothing capacitor, the rectifying diode 11 and the smoothing capacitor 12 constitute a first rectifying and smoothing means, and 13-13 'is a first output terminal. Reference numeral 14 is a rectifying diode, 15 is a smoothing capacitor, the rectifying diode 14 and the smoothing capacitor 15 constitute a second rectifying and smoothing means, and 16-16 'is a second output terminal. A control circuit 17 detects the voltage between the output terminals 16 and 16 'and generates a control signal for changing the on / off ratio of the switching element 4 and the switching element 7 so that the output voltage becomes constant.

Reference numeral 19 is a leakage inductance or an inductance element, which is connected in series to the primary winding 3a of the transformer 3 and is connected to the capacitor 6 during the ON period of the switching element 7.
The output current that resonates with and is transmitted to the secondary winding 3b of the transformer 3 is used as a resonance current. Reference numeral 20 denotes a leakage inductance or an inductance element, which is connected in series to the primary winding 10a of the transformer 10 and resonates with the capacitor 9 during the ON period of the switching element 7, and the secondary winding 10 of the transformer 10.
The output current transmitted to b is the resonance current.

Reference numeral 18 denotes a capacitor, which is connected to both ends of the switching element 4 and suppresses a sharp change in the voltage applied to the switching element 4 and the switching element 7. The switching element 4 and the switching element 7
The ON / OFF signal of the control circuit 17 is set so as to have an OFF period at the same time.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 8, (a) shows the switch of the control circuit 17.
Driving pulse waveform V of the switching element 4 _G1Shows,
(B) is a drive pulse of the switching element 7 of the control circuit 17.
Waveform V_G2(C) is the primary winding of the transformer 3.
Line current I_L1(D) shows the primary of the transformer 10.
Winding current I_L2And (e) is the first switch
Voltage V applied to the_DS1And (f) is
Current I flowing through the first switching means_Q1Shows
Where (g) is the voltage applied to the second switching means.
V_DS2And (h) is the second switching means.
Current I flowing through_Q2(I) is a rectifier
Current I flowing through_D1(J) is a rectifier
Current I flowing through the ion 14_D2Is shown.

The basic operation is the same as the circuit configuration of the third embodiment, but the switching element 4 and the switching element 7 have an off period at the same time, and the switching element 4 and the switching element 7 are applied during that period. Voltage is set to change. Since the capacitors 18 are connected to both ends of the switching element 4, turn-off of the switching element 4 and sharp rise and fall of the voltage waveform at the time of turn-off are alleviated, and the capacitor 1
Since the switching element 4 can be turned on after the charge stored in 8 is regenerated to the input DC power source 1, there is no turn-on loss of the switching element 4. The switching element 7 has a similar effect. Also, the input power supply can be continuous.

The operations other than the transition are similar to those of the embodiment described with reference to FIG. Further, when these capacitors 18 are added, the output impedance of each winding of the transformer 3 changes at the time of transition, and especially the initial current value of each winding current when the switching element 4 is turned off changes, but this has an effect on the control operation itself. In addition to the effect of making the secondary winding current waveform a resonance current, the voltage waveforms applied to the switching element 4 and the switching element 7 are not steep, so that the generation of noise is suppressed and the switching element 4 and the switching element 7 are switched. There is an effect that the occurrence of switching loss of the element 7 can be suppressed. Further, in this configuration, the switching element 4 caused by the leakage inductance of the transformer
Further, the spike voltage at the time of turning off the switching element 7 is effectively absorbed by the capacitors 6 and 9 as the diodes 5 and 8 are turned on, and the spike voltage is not generated.

Further, since the two outputs are taken out from separate transformers, the exciting current of the transformer is also small, and the inductance value can be relatively large. This is advantageous in increasing the frequency.

(Fifth Embodiment) A fifth embodiment of the present invention will be described below with reference to the drawings. FIG. 9 shows the configuration of the switching power supply device according to the fifth embodiment of the present invention. 9, the same components as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 1 is an input DC power source, 2-2 'is an input terminal, 21 is a transformer, a first primary winding 21a, a second primary winding 21b, and one or more secondary windings. A wire 21c, one end of the first primary winding 21a is connected to the input terminal 2 and the other end is connected to the input terminal 2'through the switching element 4, and the second primary winding 21b is Is connected to the input terminal 2'and the other end is connected to the first via the capacitor 6 and the capacitor 9.
The secondary winding 3c is connected to the connection point between the primary winding 21a and the switching element 4, and the secondary winding 3c is connected to the output terminals 13-13 'through the rectifying diode 11. A switching element 4 is turned on / off by the control circuit 17. Reference numeral 5 denotes a diode, and the switching element 4 and the diode 5 constitute a first switching means.

Reference numeral 6 is a capacitor for holding a DC voltage, 7 is a switching element, which is turned on and off by the control circuit 17 and turned on when the switching element 4 is off, and the input voltage is applied to the first primary winding 21a of the transformer 21. And a differential voltage of the DC voltage held by the capacitor 6 is applied. Reference numeral 8 denotes a diode, and the switching element 7 and the diode 8 constitute second switching means. Reference numeral 9 denotes a capacitor that holds a DC voltage, and is connected to both ends of the switching element 7 via the second primary winding 21b of the transformer 21. Reference numeral 11 is a rectifying diode, 12 is a smoothing capacitor, and the rectifying diode 11 and the smoothing capacitor 12 constitute a rectifying / smoothing means.
The induced voltage of c is rectified and smoothed, and the voltage is supplied to the output terminals 13-13 '. 13-13 'are output terminals. A control circuit 17 detects the voltage between the output terminals 13 and 13 'and generates a control signal for changing the on / off ratio of the switching element 4 and the switching element 7 so that the output voltage becomes constant.

The second primary winding 21b of the transformer 21
The inductance L _2, the mutual inductance element M ₁₂ between the first primary winding 21a and the second primary winding 21b, first
L ₂ = M ₁₂ M _1S , where M _{1S is} the mutual inductance between the primary winding 21a and the secondary winding 21c and M _2S is the mutual inductance between the second primary winding 21b and the secondary winding 21c. = M _1S holds.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 10, (a) shows the drive pulse waveform V _G1 of the switching element 4 of the control circuit 17,
(B) shows the drive pulse waveform V _G2 of the switching element 7 of the control circuit 17, and (c) shows the first pulse of the transformer 21.
The primary winding current I _L1 of the transformer 2 is shown.
1 shows the second primary winding current I _L2 , (e) shows the voltage V _DS1 applied to the first switching means, and (f) shows the current flowing through the first switching means. I
_Q1 is shown, (g) shows the voltage V _DS2 applied to the second switching means, (h) shows the current I _Q2 flowing through the second switching means, and (i) shows The current I _D flowing through the rectifying diode 11 is shown.

In order to show the change in the operating state with time, t ₁ to t ₃
Is shown in the figure. At time t ₁ , when the switching element 4 is turned on by the ON signal of the control circuit 17 and the switching element 7 is turned off at the same time, the input voltage V _IN is applied to the first primary winding 21a of the transformer 21, and at the same time, the second primary voltage is applied. The difference voltage V _C1 between the DC voltage V _C1 held by the capacitor 6 and the DC voltage V _C2 held by the capacitor 9 in the next winding 21b
-V _C2 is applied. At this time, the secondary winding 2 of the transformer 21
The rectifier diode 11 connected to 1c is connected so as to be off. First primary winding 2 of transformer 21
1a current I _L1 and second primary winding 2 of transformer 21
The sum current of the current I _L2 of 1b increases linearly and the transformer 2
Excitation energy is stored in 1.

When the switching element 4 is turned off by the off signal of the control circuit 17 at time t ₂ , the current flowing in the switching element 4 turns on the diode 8. At the same time, the switching element 7 is turned on by the ON signal of the control circuit 17, but there is no change in the operation regardless of whether the ON current _IQ2 flows through the diode 8 or the switching element 7. When the diode 8 or the switching element 7 is turned on, the transformer 21
Of the input voltage V _IN and the capacitor 6 to the first primary winding 21a of
The differential voltage V _C1 −V _{IN of the} DC voltage V _C1 held by the capacitor 9 is applied, and at the same time, the DC voltage V _C2 held by the capacitor 9 is applied to the second primary winding 21 b of the transformer 21.

At this time, the rectifying diode 11 connected to the secondary winding 21c of the transformer 21 is turned on, and the output terminal 1
Current is supplied to 3-13 '. At this time, the current _IQ2 flowing through the second switching means gradually decreases to a negative value as the excitation energy of the transformer 21 decreases and the output current emitted from the secondary winding 21c of the transformer 21 increases. When the switching element 7 is turned off by the OFF signal of the control circuit 17 while a negative current is flowing through the switching element 7, the diode 5 is turned on by this current. At the same time, the switching element 4 is turned on by the ON signal of the control circuit 17, but even if the current _IQ1 flowing through the first switching means flows through the switching element 4, the diode 5
There is no change in operation even when flowing through. Switching element 4
When the switching element 7 is turned on and the switching element 7 is turned off at the same time, the input voltage V _IN is applied to the first primary winding 21a of the transformer 21, and at the same time, the capacitor 6 is held in the second primary winding 21b of the transformer 21. DC voltage V _C1 and capacitor 9
The differential voltage V _C1 −V _{C2 of the} DC voltage V _C2 held by is applied. This operation is repeated.

When the ON period of the switching element 4 is T _ON and the OFF period is T _OFF , V _IN × T _ON = (V _C1 −V _IN ) × depending on the reset condition of the first primary winding 21a of the transformer 21. From the reset condition of the second primary winding 21b of the transformer 21, T _OFF holds and (V _C1 −V _C2 ) × T _ON = V _C2 × T _OFF . When V _C1 and V _C2 are obtained from the above, V _C1 = (T _ON + T _OFF ) / T _OFF × V _IN V _C2 = T _ON / T _OFF × V _IN When the winding ratio of the first primary winding 21a and the secondary winding 21c of the transformer 21 is n: 1, the output terminal 13-1
Since the output voltage V _OUT of 3 ′ is V _OUT = (V _C1 −V _IN ) / n = T _ON / T _OFF / n ₁ × V _IN , the output voltage depends on the _ON / OFF ratio of the switching element 4 and the switching element 7. You can control. In this configuration, the spike voltage at the turn-off of the switching element 4 and the switching element 7 due to the leakage inductance of the transformer 21 is generated by the diode 5 and the diode 8.
Is effectively absorbed by the capacitors 6 and 9 when turned on, and no strike voltage is generated.

Further, when the capacitance values of the capacitors 6 and 9 are sufficiently large and the fluctuation of the DC voltage being held can be ignored, the current waveform of the first primary winding 21a of the transformer 21 can be zero ripple. There are also original characteristics of the converter.

(Embodiment 6) A sixth embodiment of the present invention will be described below with reference to the drawings. FIG. 11 shows the configuration of the switching power supply device according to the sixth embodiment of the present invention. 11, the same components as those in FIG. 15 are designated by the same reference numerals and the description thereof will be omitted.

Reference numeral 1 is an input DC power source, 2-2 'is an input terminal, 21 is a transformer, a first primary winding 21a, a second primary winding 21b, and one or more secondary windings. A wire 21c, one end of the first primary winding 21a is connected to the input terminal 2 and the other end is connected to the input terminal 2'through the switching element 4, and the second primary winding 21b is Is connected to the input terminal 2'and the other end is connected to the first via the capacitor 6 and the capacitor 9.
The secondary winding 3c is connected to the connection point between the primary winding 21a and the switching element 4, and the secondary winding 3c is connected to the output terminals 13-13 'through the rectifying diode 11. A switching element 4 is turned on / off by the control circuit 17. Reference numeral 5 denotes a diode, and the switching element 4 and the diode 5 constitute a first switching means.

Reference numeral 6 is a capacitor for holding a DC voltage, 7 is a switching element, which is turned on and off by the control circuit 17 and turned on when the switching element 4 is off, and the input voltage is input to the first primary winding 21a of the transformer 21. And a differential voltage of the DC voltage held by the capacitor 6 is applied. Reference numeral 8 denotes a diode, and the switching element 7 and the diode 8 constitute second switching means. Reference numeral 9 denotes a capacitor that holds a DC voltage, and is connected to both ends of the switching element 7 via the second primary winding 21b of the transformer 21. Reference numeral 11 is a rectifying diode, 12 is a smoothing capacitor, and the rectifying diode 11 and the smoothing capacitor 12 constitute a rectifying and smoothing means, and the secondary winding 3 c of the transformer 21.
The induced voltage is rectified and smoothed, and the voltage is supplied to the output terminals 13-13 '. 13-13 'are output terminals. A control circuit 17 detects the voltage between the output terminals 13 and 13 'and generates a control signal for changing the on / off ratio of the switching element 4 and the switching element 7 so that the output voltage becomes constant.

Reference numeral 18 denotes a capacitor, which is connected to both ends of the switching element 4 and suppresses a sharp change in the voltage applied to the switching element 4 and the switching element 7. The switching element 4 and the switching element 7
The ON / OFF signal of the control circuit 17 is set so as to have an OFF period at the same time. The second one of the transformer 21
Inductance L _{2 of} secondary winding 21b, first primary winding 2
Mutual inductance M between 1a and the second primary winding 21b
₁₂ , the mutual inductance between the first primary winding 21a and the secondary winding 21c is M _1S , the mutual inductance between the second primary winding 21b and the secondary winding 21c is M _2S , and L ₂ = It is configured such that M ₁₂ M _1S = M _1S .

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 12, (a) shows the drive pulse waveform V _G1 of the switching element 4 of the control circuit 17,
(B) shows the drive pulse waveform V _G2 of the switching element 7 of the control circuit 17, and (c) shows the first pulse of the transformer 21.
The primary winding current I _L1 of the transformer 2 is shown.
1 shows the second primary winding current I _L2 , (e) shows the voltage V _DS1 applied to the switching element 4, and (f) shows the current I _Q1 flowing through the switching means 1. (G) shows the voltage V _DS2 applied to the switching means 1, (h) shows the current I _Q2 flowing through the switching means 2, and (i) shows the current I flowing through the rectifying diode 11. _{Shows D.}

The basic operation is the same as the circuit configuration of the fifth embodiment, but the switching element 4 and the switching element 7 have an off period at the same time, and are applied to the switching element 4 and the switching element 7 during that period. Voltage is set to change. Since the capacitors 18 are connected to both ends of the switching element 4, turn-off of the switching element 4 and sharp rise and fall of the voltage waveform at the time of turn-off are alleviated, and the capacitor 1
Since the switching element 4 can be turned on after the charge stored in 8 is regenerated to the input DC power source 1, there is no turn-on loss of the switching element 4. The switching element 7 has a similar effect.

The operations other than the transient time are the same as those of the embodiment described with reference to FIG. When these capacitors 18 are added, the output impedance of each winding of the transformer 21 changes at the time of transition, and especially the initial current value of each winding current when the switching element 4 is turned off changes, but this has an effect on the control operation itself. Since the voltage waveforms applied to the switching elements 4 and 7 are not steep, the generation of noise is suppressed and the switching loss of the switching elements 4 and 7 is also suppressed.

Further, in this configuration, the spike voltage generated when the switching element 4 and the switching element 7 are turned off due to the leakage inductance of the transformer 21 is effectively absorbed by the capacitors 6 and 9 as the diodes 5 and 8 are turned on. ,
There is also an effect that no spike voltage is generated.

Further, when the capacitance values of the capacitors 6 and 9 are sufficiently large and the fluctuation of the DC voltage being held can be ignored, the current waveform of the first primary winding 21a of the transformer 21 can be zero ripple. There are also original characteristics of the converter.

(Embodiment 7) Hereinafter, a seventh embodiment of the present invention will be described with reference to the drawings. The circuit configuration is shown in Fig. 9.
However, the effective leakage inductance of the secondary winding 21c of the transformer 21 resonates with the smoothing capacitor 12 during the ON period of the switching element 7, and the secondary winding of the transformer 21 It is set so that the output current transmitted to 21c is a resonance current.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 13, (a) shows the drive pulse waveform V _G1 of the switching element 4 of the control circuit 17,
(B) shows the drive pulse waveform V _G2 of the switching element 7 of the control circuit 17, and (c) shows the first pulse of the transformer 21.
The primary winding current I _L1 of the transformer 2 is shown.
1 shows the second primary winding current I _L2 , (e) shows the voltage V _DS1 applied to the first switching means, and (f) shows the current flowing through the first switching means. I
_Q1 is shown, (g) shows the voltage V _DS2 applied to the second switching means, (h) shows the current I _Q2 flowing through the second switching means, and (i) shows The current I _D flowing through the rectifying diode 11 is shown. In order to show the change over time in the operating state, t ₁ to t ₆ are shown in the figure.

The basic operation is the same as the circuit configuration of the fifth embodiment, but when the switching element 7 is turned on and current is supplied to the output, the smoothing capacitor 12 and the transformer 2 are
Effective leakage inductance of the secondary winding 21c resonates, since it is set sufficiently small resonance frequency, the secondary winding current I _D of the transformer 21 rises from zero a sine wave, again at t ₄ It becomes zero. Therefore, the rectifying diode 11 becomes zero current switching, and recovery does not occur.

The operations other than the transient time are the same as those in the embodiment described with reference to FIG.

In this structure, the secondary side rectifying diode is switched to zero current, and the occurrence of recovery can be eliminated. Further, there is an effect that the turn-off current of the switching element 7 can be reduced and the switching loss can be reduced.

Although the DC voltage V _C is actually the sum of the DC voltage component and the fluctuation component which is the resonance voltage, the fluctuation component due to the resonance voltage can be set to be sufficiently small, so that the conversion ratio of the input voltage and the output voltage is the same as that of the first embodiment. It is almost the same as the case of.

Further, in this configuration, the spike voltage generated when the switching element 4 and the switching element 7 are turned off due to the leakage inductance of the transformer 21 is effectively absorbed by the capacitors 6 and 9 as the diodes 5 and 8 are turned on. ,
There is also an effect that no spike voltage is generated.

When the capacitance values of the capacitors 6 and 9 are sufficiently large and the variation of the DC voltage being held can be ignored, the current waveform of the first primary winding 21a of the transformer 21 can be zero ripple. There are also original characteristics of the converter.

(Embodiment 8) An eighth embodiment of the present invention will be described below with reference to the drawings. The circuit configuration is shown in Fig. 9.
However, the effective leakage inductance of the secondary winding 21c of the transformer 21 resonates with the smoothing capacitor 12 during the ON period of the switching element 7, and the secondary winding of the transformer 21 It is set so that the output current transmitted to 21c is a resonance current.

The operation of the switching power supply device configured as described above will be described below with reference to the operation waveforms of the respective parts of FIG.

In FIG. 14, (a) shows the drive pulse waveform V _G1 of the switching element 4 of the control circuit 17,
(B) shows the drive pulse waveform V _G2 of the switching element 7 of the control circuit 17, and (c) shows the first pulse of the transformer 21.
The primary winding current I _L1 of the transformer 2 is shown.
1 shows the primary winding current I _L2 , (e) shows the voltage V _DS1 applied to the first switching means,
(F) shows the current I _Q2 flowing through the first switching means, (g) shows the voltage V _DS2 applied to the second switching means, and (h) shows the second switching means. The flowing current I _Q2 is shown, and (i) shows the current I _D flowing through the rectifying diode 11.

The basic operation is the same as the circuit configuration of the seventh embodiment, but the switching element 4 and the switching element 7 have an OFF period at the same time, and the switching element 4 and the switching element 7 are applied during that period. Voltage is set to change. Since the capacitors 18 are connected to both ends of the switching element 4, turn-off of the switching element 4 and sharp rise and fall of the voltage waveform at the time of turn-off are alleviated, and the capacitor 1
Since the switching element 4 can be turned on after the charge stored in 8 is regenerated to the input DC power source 1, there is no turn-on loss of the switching element 4. The switching element 7 has a similar effect.

Operations other than these transients are shown in FIG.
Since it is the same as the embodiment described above, the description thereof will be omitted. When these capacitors 18 are added, the output impedance of each winding of the transformer 21 changes at the time of transition, and especially the initial current value of each winding current when the switching element 4 is turned off changes, but this has an effect on the control operation itself. Less 2
In addition to the effect of using the next winding current waveform as the resonance current, the voltage waveforms applied to the switching element 4 and the switching element 7 are not steep, so that the generation of noise is suppressed and the switching elements 4 and 7 are switched. It also has the effect of suppressing the occurrence of loss.

Further, in this configuration, the spike voltage generated when the switching element 4 and the switching element 7 are turned off due to the leakage inductance of the transformer 21 is effectively absorbed by the capacitors 6 and 9 as the diodes 5 and 8 are turned on. ,
There is also an effect that no spike voltage is generated.

Further, when the capacitance values of the capacitors 6 and 9 are sufficiently large and the fluctuation of the DC voltage being held can be ignored, the current waveform of the first primary winding 21a of the transformer 21 can be zero ripple. There are also original characteristics of the converter.

[0108]

With the above-described structure, when the first and second switching means are turned on, the parasitic capacitor of the switching means and the distributed capacitance of the transformer discharge the stored energy before turning on the spike current. When the first and second switching means are turned off, no spike voltage is generated due to the influence of the leakage inductance of the transformer. Another feature is that the input current can be zero ripple.

Therefore, the present invention realizes a small size, high efficiency, and low noise switching power supply device.

[Brief description of drawings]

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

FIG. 2 is an explanatory diagram showing operation waveforms of the circuit diagram of FIG. 1 of the present invention.

FIG. 3 is a circuit diagram showing a switching power supply device according to a second embodiment of the present invention.

FIG. 4 is an explanatory diagram showing operation waveforms of the circuit diagram of FIG. 3 of the present invention.

FIG. 5 is a circuit diagram showing a switching power supply device according to a third embodiment of the present invention.

FIG. 6 is an explanatory diagram showing operation waveforms of the circuit diagram of FIG. 5 of the present invention.

FIG. 7 is a circuit diagram showing a switching power supply device according to a fourth embodiment of the present invention.

8 is an explanatory diagram showing operation waveforms of the circuit diagram of FIG. 7 of the present invention.

FIG. 9 is a circuit diagram showing a switching power supply device according to a fifth embodiment of the present invention.

FIG. 10 is an explanatory diagram showing operation waveforms of the circuit diagram of FIG. 9 of the present invention.

FIG. 11 is a circuit diagram showing a switching power supply device according to a sixth embodiment of the present invention.

12 is an explanatory diagram showing operation waveforms of the circuit diagram of FIG. 11 of the present invention.

FIG. 13 is an explanatory diagram showing operation waveforms in the seventh embodiment of the present invention.

FIG. 14 is an explanatory diagram showing operation waveforms in the eighth embodiment of the present invention.

FIG. 15 is a circuit diagram of a switching power supply device in a first conventional example.

16 is an explanatory diagram showing operation waveforms of the conventional circuit diagram of FIG.

FIG. 17 is a circuit diagram of a switching power supply device according to a second conventional example.

18 is an explanatory diagram showing operation waveforms of the conventional circuit diagram of FIG.

[Explanation of symbols]

 1 Input DC power supply 2-2 'Input terminal 3 Transformer 4 Switching element 5 Diode 6 Capacitor 7 Switching element 8 Diode 9 Capacitor 10 Transformer 11 Rectifying diode 12 Smoothing capacitor 13-13' Output terminal 14 Rectifying diode 15 Smoothing capacitor 16-16 ' Output terminal 17 Control circuit 18 Capacitor 19 Leakage inductance or inductance element 20 Leakage inductance or inductance element 21 Transformer

Claims (8)

[Claims] 1. A first transformer having at least a primary winding and one or more secondary windings, a second transformer having a primary winding and one or more secondary windings, and a DC voltage. For holding the DC voltage, a second capacitor for holding a DC voltage, and an input voltage is applied to the primary winding of the first transformer at the same time as the first winding is repeatedly turned on and off. The DC voltage held in the capacitor of the
And a first switching means for applying the difference voltage of the DC voltage held in the capacitor of the first transformer to the primary winding of the second transformer, and the first switching means is repeatedly turned on and off alternately. The difference voltage between the DC voltage held by the first capacitor and the input voltage is applied to the primary winding of the first transformer, and at the same time the DC voltage held by the second capacitor is applied to the second transformer. A first transformer, a second transformer, or both of the first transformer and the second switching means for applying to the primary winding;
A switching power supply device that supplies the voltage induced in the secondary winding to the output through rectifying and smoothing means. 2. Both ends of the first switching means or the second
2. The switching according to claim 1, wherein a capacitor is connected to both ends of the switching means of FIG. 2 or both of the switching means, and both the first switching means and the second switching means have a period in which they are turned off, and on and off are alternately repeated. Power supply. 3. A first transformer having at least a primary winding and one or more secondary windings, a second transformer having a primary winding and one or more secondary windings, and a DC voltage. For holding the DC voltage, a second capacitor for holding a DC voltage, and an input voltage is applied to the primary winding of the first transformer at the same time as the first winding is repeatedly turned on and off. The DC voltage held in the capacitor of the
And a first switching means for applying the difference voltage of the DC voltage held in the capacitor of the first transformer to the primary winding of the second transformer, and the first switching means is repeatedly turned on and off alternately. The difference voltage between the DC voltage held by the first capacitor and the input voltage is applied to the primary winding of the first transformer, and at the same time the DC voltage held by the second capacitor is applied by the second transformer. A first transformer, a second transformer, or both of the first transformer and the second switching means for applying to the primary winding;
The input power supply which supplies a voltage induced in a secondary winding to an output through a rectifying / smoothing means and is coupled via a primary winding and a secondary winding of the first transformer or the second transformer,
In the loop including the first and second capacitors, the rectifying / smoothing means, the first and second switching means, the capacitor, the input power source, the rectifying / smoothing means, or a combination thereof and the first and second transformers are connected. A switching power supply device characterized by resonating with a leakage inductance or an externally attached inductance, and using a secondary winding current of the first or second transformer as a resonance current. 4. Both ends of the first switching means or the second
4. A switching device according to claim 3, wherein a capacitor is connected to both ends or both of the switching device of 1), and both the first switching device and the second switching device have a period in which they are turned off so that they are alternately turned on and off. Power supply. 5. A transformer having at least a first primary winding, a second primary winding, and one or more secondary windings, a first capacitor for holding a DC voltage, and a DC voltage. A second capacitor for holding the input voltage applied to the first primary winding of the transformer by repeatedly turning on and off, and at the same time the direct current voltage held by the first capacitor and the second voltage. A first differential voltage applied to the second primary winding of the transformer, the differential voltage being held by the capacitor
The switching means and the first switching means are repeatedly turned on and off alternately, and the difference voltage between the DC voltage and the input voltage held in the first capacitor is turned on to the first primary winding of the transformer when turned on. It has a second switching means for applying a direct current voltage, which is simultaneously held in the second capacitor, to the second primary winding of the transformer, and applies a voltage induced in the secondary winding of the transformer. A switching power supply device that supplies the output through rectifying and smoothing means. 6. Both ends of the first switching means or the second
6. The switching according to claim 5, wherein a capacitor is connected to both ends of the switching means of FIG. 2 or both of them, and both the first switching means and the second switching means have a period in which they are turned off, and are turned on and off alternately. Power supply. 7. A transformer having at least a first primary winding, a second primary winding, and one or more secondary windings, a first capacitor for holding a DC voltage, and a DC voltage. A second capacitor for holding the input voltage applied to the first primary winding of the transformer by repeatedly turning on and off, and at the same time the direct current voltage held by the first capacitor and the second voltage. A first differential voltage applied to the second primary winding of the transformer, the differential voltage being held by the capacitor
The switching means and the first switching means are repeatedly turned on and off alternately, and the difference voltage between the DC voltage and the input voltage held in the first capacitor is turned on to the first primary winding of the transformer when turned on. It has a second switching means for applying a direct current voltage, which is simultaneously held in the second capacitor, to the second primary winding of the transformer, and applies a voltage induced in the secondary winding of the transformer. The input power supply, the first and second capacitors, which are supplied to the output through rectifying and smoothing means and are coupled via the primary winding and the secondary winding of the first transformer or the second transformer. ,
In the loop including the rectifying / smoothing means and the first and second switching means, the capacitor, the input power source, the rectifying / smoothing means, or a combination thereof, and the leakage inductance of the first and second transformers or the external inductance are used. A switching power supply device which resonates and uses the secondary winding current of the first or second transformer as a resonance current. 8. Both ends of the first switching means or the second switching means.
8. The switching according to claim 7, wherein a capacitor is connected to both ends or both of the switching means, and both the first switching means and the second switching means have a period in which they are turned off, and the on / off operations are repeated alternately. Power supply.