JPH0746903B2 - Resonant switching power supply circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resonant vibration type switching power supply circuit used for a DC stabilized power supply or the like.

[Conventional technology]

Currently, as a power supply for electronic communication used in electronic computers, communication devices, etc., a PWM type switching regulator having advantages of small size, light weight and high efficiency is often used. However, if the switching frequency is 20 kHz or less, no major problem occurs, but if it is 100 kHz or more, the leakage inductance of the power transmission transformer and the stray capacitance of the switching element affect the switching element on / off switching. The ratio at which the voltage waveform and the current waveform at both ends of the switching element overlap with each other increases, and the portion where these voltage and current waveforms overlap with each other becomes a switching loss, and the loss increases as the oscillation frequency increases. When the switching loss increases, the power conversion efficiency decreases and heat is generated. This requires a large radiator,
This hinders miniaturization of the power supply device.

As a method for solving the above problems, there is a resonance type switching power supply circuit shown in FIG. The DC power supply 1 of this resonance type switching power supply circuit is composed of a series circuit of first and second power supplies 2a and 2b, and is formed in a center tap type having first, second and third terminals 3, 4 and 5. There is. Between the first terminal 3 and the second terminal 4, a series circuit of first and second switching elements Q ₁ and Q _{2 formed} of transistors is connected. By-pass diodes D ₁ and D ₂ are connected in antiparallel to the first and second switching elements Q ₁ and Q ₂ which are alternately turned on and off.

Between the third terminal 5 of the power source 1 and the connection midpoint 6 of the first and second switching elements Q ₁ and Q _2, a resonance capacitor C ₁ , a series resonance inductance element (reactor) L ₁ and a load. A series circuit is connected to the primary winding N ₁ of the transformer T for forming the circuit. That is, one end of the capacitor C ₁ is connected to the third terminal 5, and the other end of the capacitor C ₁ is connected to the switching element via the inductance element L ₁ and the primary winding N _1.
It is connected to the connection midpoint 6 of Q ₁ and Q ₂ .

Transformer T has a secondary winding N _2, N _3, the secondary winding N _2, N ₃ of this Sentatatsupu configuration, diode D _3, D ₄ and output rectifier smoothing consisting smoothing capacitor C ₂ Metropolitan A load 8 is connected via the circuit 7.

A control circuit 9 for ON / OFF controlling the first and second switching elements Q ₁ and Q ₂ includes a voltage detection circuit 10 for detecting the output voltage of the output smoothing rectification circuit 7, and this voltage detection circuit 10
Error amplifier 12 for obtaining an output corresponding to the difference between the detected voltage obtained from the reference voltage and the reference voltage of the reference voltage source 11, and a VC for outputting a frequency signal corresponding to the output voltage of the error amplifier 12.
It comprises an O (voltage controlled oscillator) 13 and a switch control signal forming circuit 14 for alternately turning on and off the switching elements Q ₁ and Q ₂ at the output frequency of the VCO 13. The switch control signal forming circuit 14 forms a control signal for the first switching element Q ₁ on the basis of the output of the VCO, and forms a control for the second switching element Q _{2 by} the inverted signal of each switching element Q ₁ , Q _{2, that} is, to supply to the base of the transistor.

The switching elements Q ₁ and Q ₂ are alternately on / off controlled as shown in FIGS. 12 (A) and 12 (B) at a frequency lower than the resonance frequency of the series resonance circuit. 1st switching element Q ₁
Is on and the second switching element Q ₂ is off (7th
In t ₁ to t ₃ ) of the figure, first, the current I based on series resonance is
Capacitor C ₁ , power supply 2a, first switching element Q ₁ , 1
It flows in the circuit composed of the secondary winding N ₁ and the inductance element L ₁ . The voltage of the capacitor C ₁ is as shown in Fig. 12 (C).
It is almost −E at time t ₁ , but decreases toward zero, and then becomes almost + E. The current I flowing through the capacitor C ₁ and the inductance element L ₁ reaches a maximum positive value when the capacitor voltage V _C becomes zero as shown in FIG. 12 (D), and then decreases. During the discharging period of the capacitor C ₁ indicated by t _{2 to} t ₃ , the capacitor C ₁ and the inductance element
A reverse current flows in the circuit composed of L ₁ , the primary winding N ₁ , the diode D ₁ , and the power supply 2a. An operation similar to that in the t ₁ ~t ₃ periods also occur at t ₃ ~t ₄ period in which the second switching-element Q ₂ is turned on.

[Problems to be Solved by the Invention]

By the way, the control of the output voltage or power of the resonance type switching power supply circuit is performed by a frequency control method. That is, the first
Also, the voltage of the load 8 is changed by changing the frequency of on / off control of the second switching elements Q ₁ and Q ₂ . Therefore, the circuit constant must be determined at the lowest frequency, which makes it difficult to significantly reduce the loss. In a state where the diode D ₁ is turned on at t ₂ ~t _3, when the second switching-element Q ₂ is turned on, a recovery current based on the accumulated carrier diode D ₁ (short-circuit current) is switching-element Q ₂ Flow into. This recovery current (short-circuit current) flows during the period in which the collector-emitter voltage of the second switching element Q ₂ changes from E volt to zero volt, resulting in loss and reduced efficiency. Diode D ₁ , D ₂
By omitting, the loss due to the recovery current (short circuit current) does not occur, but the capacitor C ₁ becomes higher than E. That is,
At power-on the first and second switching-element Q _1, unbalanced voltage Yotsute capacitor C ₁ of the resonant current flowing in Q ₂ is higher than the E sudden change in load or the like, switching-element Q _1, Q ₂ and the diodes D ₁ and D ₂ must have high withstand voltage. If high-voltage switching elements Q ₁ and Q ₂ and diodes D ₁ and D ₂ are used, the resistance (voltage drop) at the time of ON becomes large and the loss also increases, so the loss reduction effect based on the resonance type cannot be expected. .

Therefore, an object of the present invention is to provide an efficient resonant switching power supply circuit.

[Means for Solving the Problems]

The present invention for achieving the above object includes a first terminal and a second terminal.
A DC power supply circuit having a first terminal and a third terminal for applying a midpoint potential of the first and second terminals, and the first and second terminals in series with each other. A connected first and second switching element, a control circuit for alternately turning on and off the first and second switching elements at a constant cycle, and one end connected to the third terminal A resonance capacitor, a resonance inductance element connected between the other end of the resonance capacitor and a connection midpoint of the first and second switching elements, and connected in series to the inductance element. Or in a resonant switching power supply circuit consisting of a load circuit electromagnetically coupled to the inductance element,
A capacitor short-circuiting switching element connected in parallel with the capacitor, and the capacitor short-circuiting switching element is turned on in an intermediate region of an on period of at least one of the first and second switching elements, and The present invention relates to a resonance type switching power supply circuit, comprising: a control circuit of a switching element for short-circuiting a capacitor formed so as to control a time width of an ON state when controlling a voltage of a load circuit.

It is desirable to connect a clamping diode as described in claim 2.

The technical idea of claim 1 can be applied to the case where the first to fourth switching elements are connected in a bridge type as shown in claim 3.

As described in claim 4, it is desirable to add a clamping diode to the circuit of claim 3.

The technical idea of claim 1 can be applied to a modified half-bridge type circuit in which a capacitor is connected in parallel to one diode as shown in claim 5.

The technical idea of claim 1 can be applied to a circuit in which a capacitor is connected in parallel to two diodes as shown in claim 6.

The technical idea of claim 1 can be applied to the parallel type switching circuit as shown in claim 7.

[Work]

In the invention according to each claim, the amount of electric power supplied from the power supply to the resonance circuit during one cycle is controlled by controlling the on-time width of the switching element for short-circuiting the capacitor. As a result, it becomes possible to perform the control with the output power or the voltage or current controlled switching frequency fixed.

In the invention according to the second, fourth, fifth and sixth aspects, an increase in the voltage of the capacitor can be suppressed by the diode.

[First Embodiment] Next, referring to FIG. 1 and FIG. 2, a resonance type switching power supply circuit according to a first embodiment of the present invention, that is, a resonance type DC-
The DC converter will be described. However, in FIG. 1, parts that are substantially the same as those in FIG. 11 are assigned the same reference numerals and explanations thereof are omitted.

The resonance type switching power supply circuit of this embodiment shown in FIG. ₁ has first and second switching elements S ₁ and S ₂ for controlling a capacitor which are connected in parallel to the capacitor C ₁ , and further the right end of the capacitor C ₁ . First and second clamping diodes 16, which are connected between 15 and the first terminal 3 of the power source 1 and between the right end 15 of the capacitor C ₁ and the second terminal 4 of the power source 1, respectively.
Have 17. First and second switching elements of FIG.
Q ₁ and Q ₂ are alternately turned on / off at a constant frequency regardless of changes in the output voltage.

18 shall apply with sawtooth (triangular wave) generator, in this embodiment generates a sawtooth wave having twice the frequency of the first and second switching-element Q _1, Q ₂ on and off repetition frequency. Reference numeral 19 denotes a switch control signal forming circuit (switch control circuit), which is a square-wave control signal having a fixed frequency shown in FIGS. 2A and 2B, which is synchronized with the sawtooth wave supplied from the sawtooth wave generating circuit 18. Are formed and supplied to the first and second switching elements Q ₁ and Q ₂ . Incidentally, FIG. 2 (A)
The frequency of the control signal of (B) is lower than the resonance frequency of the C ₁ L ₁ resonance circuit. In this embodiment, the output voltage is controlled by the first and second control.
This is not performed by controlling the on / off repetition frequency of the switching elements Q ₁ and Q ₂ , but is performed by controlling the charging / discharging of the resonant capacitor C ₁ .

The output rectifying / smoothing circuit 7 has four diodes 20, 21, 22, 23.
And a smoothing capacitor 24, and is connected between the secondary winding N ₂ of the transformer T and the load 8. The output voltage of the output rectifying / smoothing circuit 7 is detected by the detection circuit 10, and the error amplifier
It becomes 12 inputs and is compared with the reference voltage of the reference voltage source 11. The PWM (pulse width modulation) pulse forming circuit 25 is connected to the sawtooth wave generating circuit 18 and the error amplifier 12, and includes a voltage comparator that compares the sawtooth wave and the error output and outputs a PWM pulse. The PWM pulse shown in Fig. 2 (C) and (D) is generated. The sawtooth wave is shown in FIG.
Since it has a frequency twice as high as the pulse repetition frequency shown in (D), two PWMs with a 180-degree phase difference shown in (C) and (D) of FIG. 2 are obtained by alternately distributing the outputs of the comparators. Get the pulse train. The output line of the PWM pulse forming circuit 25 is the first
And the second capacitor control switching elements S ₁ and S ₂ . The frequency of the sawtooth wave generation circuit 18 is the first
It is also possible to configure it so that it has the same switching frequency as that of the second switching elements Q ₁ and Q ₂ .

The operation of the circuit of FIG. 1 will be described with reference to FIG. 2. When the first switching element Q ₁ is turned on at time t ₀ as shown in FIG. 2 (A), it is the same as the conventional circuit. A current I due to resonance starts to flow as shown in FIG. As a result, the voltage of the capacitor C ₁ changes from −E / 2 toward 0 as shown in FIG. 2 (F). The capacitor C ₁
The change range of the charging voltage of the clamp diodes 16 and 17 is
Works from -E / 2 to + E / 2. At time t ₀ , the first capacitor control switching element S ₁ is on-controlled by the pulse shown in FIG. 2 (C), but since the left end of the capacitor C ₁ is charged to be positive, The switching element S ₁ for controlling the capacitor of _{No. 1} is in the reverse bias state, and t ₀
It is kept off for ~ t ₁ period. When the reverse charging of the capacitor C ₁ progresses in the circuit of the first terminal 3, the first switching element Q ₁ , the transformer T, the inductance element L ₁ , and the capacitor C ₁ of the power supply circuit 1, and the charging voltage becomes zero at time t1. , The reverse bias of the first capacitor controlling switching element S ₁ is released, and this turns on. As a result, ignoring the voltage drop across the switching elements Q ₁ , Q ₂ , S ₁ , and S ₂ , the charging voltage of the capacitor C ₁ will be zero until time t ₂ when the pulse in FIG. 2 (C) ends. To be kept. During the period of t _{1 to} t _2, the current limited to the inductance element L ₁ continues to flow as shown in FIG. 2 (E). When the first capacitor control switching element S ₁ is turned off at time t ₂ , a current based on the C ₁ L ₁ resonance circuit starts to flow, and the voltage of the capacitor C ₁ is shown in FIG. 2 (F).
As shown in, the current rises in the positive direction and the current I gradually decreases. When the voltage of the capacitor C ₁ becomes slightly higher than E / 2 at time t ₃ , the clamping diode 16 is turned on, and the voltage of the capacitor C ₁ is clamped at approximately E / 2. In the period from t _{3 to} t ₄ , a current flows due to the energy released from the inductance element L ₁ , but it gradually decreases as shown in FIG. 2 (E) and becomes zero at t ₄ . In FIG. 1, the first and second switching elements are shown.
No diodes are connected in parallel in Q ₁ and Q ₂ , but
Even if the diodes D ₁ and D ₂ are connected as shown in the figure or the diode is built in for the FET, the voltage of the capacitor C ₁ is clamped to E / 2 in Fig. 1. Therefore, the diodes in parallel with the first and second switching elements Q ₁ and Q ₂ are not turned on during the period of t ₃ to t ₅ . Therefore, when switching the first and second switching elements Q ₁ and Q ₂ at time t _{5 in} FIG. 2, an excessive current due to the accumulated carrier of the diode does not flow.

The t ₅ ~t ₆ period of the second view a second switching-element Q ₂ is on-controlled, t ₀ ~t ₅ periods of time similar to the operation occurs. Of course, the directions of the current I and the voltage V _{C in} this period are opposite to those in the period of t ₀ to t ₅ .

When the output voltage changes, the output of the error amplifier 12 changes,
The trailing edge of the pulse in FIGS. 2 (C) and (D) changes,
The period from t _{1 to} t ₂ also changes. As a result, the energy supply time and amount from the power supply circuit 1 within the fixed ON period t _{0 to} t _{5 of} the first switching element Q ₁ changes, and the amount of power supplied to the output rectifying and smoothing circuit 7 also changes. , The output voltage changes.

As described above, since this system is a constant frequency control system, the transformer T and the like can be optimally designed, and a highly efficient resonant switching power supply circuit can be provided.

In addition, the voltage of the capacitor C ₁ is limited to −E / 2 to + E / 2 by the functions of the clamping diodes 16 and 17, so that the first
Also, it becomes possible to reduce the withstand voltage of the second switching elements Q ₁ and Q ₂ , and the power loss reduction effect based on this can also be obtained. Further, even if the diodes are not connected in antiparallel to the first and second switching elements Q ₁ and Q ₂ , the voltage rise of the capacitor C ₁ can be suppressed, and the excessive current due to the storage carrier of the diode can be suppressed. The problem is also resolved as described above.

Second Embodiment Next, a resonance type switching power supply circuit according to a second embodiment of the present invention will be described with reference to FIGS. 3 and 4. However, in FIG. 3, the substantially same parts as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted. In this embodiment the first to fourth switching-circuit in switching-element Q ₁ to Q ₄ of is configured Furuburitsuji type. Third and fourth switching-element Q _3, Q ₄ is connected to a position of the first view of the capacitor 2a, 2b. First to fourth switching elements
Q _{1 to} Q ₄ are controlled as shown in FIGS. 4 (A) to (D),
A switching element S ₁ for controlling the first and second capacitors,
S ₂ is controlled as shown in FIGS. 4 (E) and 4 (F).

The current I of the resonant circuit during the period t ₀ to t _{1 in} FIG.
The current I of the resonant circuit during the period of t _{1 to} t ₂ flows from Q ₃ , C ₁ , L ₁ , N ₁ , and Q _{2 in the} circuit consisting of Q ₁ , N ₁ , L ₁ , C ₁ , and Q _4. Flowing in the circuit. The principle of changes in the current I and the voltage V _C due to resonance is the same as in FIG. The principle of the output voltage adjusting method is also the same as that in FIG. 1, and the first and second capacitor controlling switching elements shown in FIGS.
By changing the on-time width of S ₁ and S _2, the capacitor C ₁
The time width when the voltage of 0 becomes zero changes, and the output voltage changes. Therefore, according to this embodiment, it is possible to obtain the same effect as that of the first embodiment.

[Third Embodiment] Next, a resonance type switching power supply circuit according to a third embodiment of the present invention will be described with reference to FIGS. 5 and 6. However, in FIG. 5, parts that are substantially the same as those in FIGS. 1 and 3 are given the same reference numerals, and descriptions thereof will be omitted.

In this embodiment, the first and second switching elements Q ₁ , Q ₂
The transformer T and the inductance element L ₁ are connected between the connection middle point 6 of the second diode 17 and the connection middle point 15 of the first and second diodes 16 and 17, and the capacitor C ₁ and the capacitor C ₁ are connected in parallel to the second diode 17. The control switching element S ₁ is connected.

The first and second switching elements Q ₁ and Q ₂ are shown in FIG. 6 (A).
As shown in (B), the circuit is alternately turned on / off at a constant frequency as in the circuit shown in FIG. The capacitor controlling switching element S ₁ is controlled by the PWM pulse shown in FIG. 6 (C). If the at t ₀ at 6 illustrations that are _{I = 0, V C = 0} , Q 1 is t ₀ ~t ₁ period, Q ₃ is turned on, because Q ₂ is off, the current I from zero Rise on a straight line. This current I flows through the circuit of Q ₁ , N ₁ , L ₁ and S ₁ .

During the period t ₁ -t ₂ , Q ₁ is on, Q ₂ , Q ₃ are off, and Q ₁ ,
A current I flows in the circuit of N ₁ , L ₁ and C ₁ .

During the period from t _{2 to} t ₃ , since the charging voltage V _C of the capacitor C ₁ is slightly higher than the power supply voltage E, the first diode 16 is turned on and the voltage V _{C of the} capacitor C ₁ is almost It is clamped to the power supply voltage E. Release of the stored energy the inductance element L ₁ is terminated prior to the t ₃ time, the current I is zero at t _3. Therefore, the second switching element Q ₂ turns on in the state of zero current.

The t ₃ ~t ₄ period, the Q ₂ is turned on, Q _1, Q ₃ is off,
A closed circuit of C ₁ , L ₁ , N ₁ and Q ₂ is formed, and discharge of the capacitor C ₁ occurs. t ₄ connexion voltage of the capacitor C ₁ such a point becomes zero, when it is subsequently charged in the reverse direction diode 17 is turned on, the voltage V _C of the capacitor C ₁ becomes substantially zero. When the trailing edge of the pulse of FIG. 6 (C) for driving the capacitor controlling switching element S ₁ is controlled, one cycle (t ₀ ~
During t ₅ ), the amount of electric power supplied from the power supply circuit 1 changes and the output voltage also changes. Therefore, the same effects as those of the first and second embodiments can be obtained.

Fourth Embodiment Next, a resonance type switching power supply circuit of a fourth embodiment will be described with reference to FIGS. 7 and 8. However, in FIG. 7, parts that are substantially the same as those in FIG. 1, FIG. 3, and FIG. The circuit of FIG. 7 has a capacitor C _{2 in} parallel with the diode 16 of FIG.
It is the same as the circuit in which the switching element S ₂ for controlling the capacitor is connected.

The operation in the period t ₀ to t _{3 in} FIG. 8 is the same as that in the period t ₀ to t ₃ in FIG. t ₃ ~t ₆ period is an operation opposite to the polarity of t ₀ ~t ₃ period, Q ₁ at t ₃ ~t _4, S ₁ is turned off, Q ₂ and S ₂ are turned on,
During the period from t _{4 to} t ₆ , Q ₁ , S ₁ and S ₂ are turned off, Q ₂ is turned on, the current I changes symmetrically as shown in FIG. 8 (E), and the voltage of the capacitor C ₁ changes. It changes as shown in FIG. Switching elements S ₁ and S ₂ for controlling the first and second capacitors
Is controlled by the PWM pulse of Fig. 8 (C) (D),
The output voltage is controlled in the same manner as in the first, second and third embodiments, and the same effects can be obtained.

[Modifications] The present invention is not limited to the above-described embodiments, and the following modifications are possible, for example.

(1) As shown in FIG. 9, a center tap is provided on the primary winding of the transformer T, and a resonance circuit of an inductance element L ₁ and a capacitor C ₁ is connected between this center tap and the third terminal 5, A first terminal is provided between the first terminal 3 and the center tap.
The half N _1a of the primary winding is connected through the switching element Q _{1 of the above,} and the other half N _1a of the primary winding is connected between the second terminal 4 and the center tap through the _second switching element Q _{2. 1b} may be connected to control the first and second switching elements Q ₁ and Q ₂ and the first and second capacitor controlling switching elements S ₁ and S ₂ in the same manner as in FIG.

(2) The switching elements S ₁ and S ₂ for controlling the capacitor C ₁ may be composed of two FETs 31 and 32 and two diodes 33 and 34 as shown in FIG.

(3) may be used as FET first to fourth switching-element Q ₁ to Q _4.

(4) A diode may be connected in antiparallel to the first and second switching elements Q ₁ and Q ₂ shown in FIGS. 1 and 3.

(5) The power supply circuit 1 shown in FIG. 1 can be configured with two E / 2 power supplies.

(6) S _1, may be a PWM pulse for controlling the S ₂ example, those having a pulse width corresponding to t ₁ ~t ₂ period of the second view.

(7) When the transformer T has a large inductance, this may also be used as a resonance inductance and the inductance element L ₁ may be omitted.

(8) It is also applicable to the case where the load 8 is directly connected to the position of the transformer T and AC is supplied to the load 8.

〔The invention's effect〕

As described above, according to the invention of any of the claims, it becomes possible to adjust the power, the voltage or the current while the switching frequency is fixed. In addition, claims 2, 4, 5, 6
According to this, it is possible to suppress an increase in the voltage of the capacitor and to reduce the power loss when the switching element is switched on and off.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a resonance type switching power supply circuit of a first embodiment of the present invention, FIG. 2 is a waveform diagram showing the state of each part of FIG. 1 in principle, and FIG. 3 is a second embodiment. FIG. 4 is a circuit diagram showing an example of a resonance type switching power supply circuit, FIG. 4 is a waveform diagram showing the state of each part of FIG. 3 in principle, and FIG. 5 is a circuit showing a resonance type switching power supply circuit of the embodiment of FIG. FIG. 6 is a waveform diagram showing the state of each part of FIG. 5 in principle, FIG. 7 is a waveform diagram showing the resonance type switching power supply circuit of the fourth embodiment, and FIG. 8 is each part of FIG. FIG. 9 is a waveform diagram showing the state of principle, FIG. 9 is a circuit diagram showing a modified resonant switching power supply circuit, FIG. 10 is a circuit diagram showing a modified capacitor control switch circuit, and FIG. 11 is a conventional circuit diagram. Circuit diagram showing the resonance type switching power supply circuit. Fig. 12 is a waveform showing the state of each part in Fig. 11 in principle. It is a figure. 1 ...... DC power supply circuit, 3 ...... first terminal, 4 ...... second terminals, Q ₁ ...... first switching-element, Q ₂ ...... second switching-element, C ₁ ...... resonance capacitor , L ₁ ... series resonance inductance element, S ₁ , S ₂ ... switching element for capacitor control.

Claims (7)

[Claims] 1. A direct current power supply circuit having a first terminal, a second terminal, and a third terminal for providing a midpoint potential of the first and second terminals, the first terminal and the second terminal. A first and a second switching element connected in series with each other, and a control circuit for alternately turning on and off the first and the second switching element at a constant cycle. A resonance capacitor having one end connected to the third terminal, and a resonance inductance connected between the other end of the resonance capacitor and a connection midpoint of the first and second switching elements. In a resonance type switching power supply circuit comprising an element and a load circuit connected in series to the inductance element or electromagnetically coupled to the inductance element, a capacitor connected in parallel to the capacitor. A capacitor short-circuit switching element and a capacitor short-circuit switching element in an ON state in an intermediate region of the ON period of at least one of the first and second switching elements and controlling the voltage or current of the load circuit. And a control circuit for a switching element for short-circuiting a capacitor formed so as to control the time width of the ON state when the resonance type switching power supply circuit. 2. A clamping element for clamping the voltage of the capacitor is connected between the other end of the capacitor and the first and second terminals of the power supply circuit, respectively. Item 1. A resonance type switching power supply circuit according to item 1. 3. A DC power supply circuit having first and second terminals, first and second switching elements connected in series between the first and second terminals, and Third and fourth switching elements connected in series between the first and second terminals, the first and fourth switching elements, and the second and third switching elements A control circuit for performing on / off control alternately at a constant cycle, a resonance capacitor having one end connected to a connection midpoint of the third and fourth switching elements, the other end of the resonance capacitor and the A resonance inductance element connected between the connection middle point of the first and second switching elements, and a resonance inductance element connected in series or electromagnetically coupled to the inductance element. In a resonant switching power supply circuit including a load circuit, a capacitor short-circuit switching element connected in parallel to the capacitor, an ON period of the first and fourth switching elements, and a second and third switching element While turning on the capacitor short-circuit switching element in an intermediate region of at least one of the on-periods and the on-period, the time width of the on-state is controlled when controlling the voltage or current of the load circuit. And a control circuit for the formed switching element for short-circuiting the capacitor. 4. A clamping element for clamping the voltage of the capacitor is connected between the other end of the capacitor and the first and second terminals of the power supply circuit, respectively. Item 3. A resonance type switching power supply circuit according to item 3. 5. A DC power supply circuit having first and second terminals, and first and second switching elements connected in series with each other between the first and second terminals, A control circuit for alternately turning on and off the first and second switching elements at a constant cycle, and a first and a second circuit connected between the first and second terminals in series with each other. A second diode; a resonance capacitor connected in parallel to the second diode; a connection midpoint between the first and second switching elements and a connection midpoint between the first and second diodes. A resonance type switching power supply circuit comprising a resonance inductance element connected in between, and a load circuit connected in series to the inductance element or electromagnetically coupled to the inductance element, A capacitor short-circuiting switching element connected in parallel to the capacitor, and a capacitor short-circuiting switching element in an ON state in the first region of the ON period of the first switching element, and a voltage or current of the load circuit A resonance type switching power supply circuit, comprising: a control circuit for a switching element for short-circuiting a capacitor formed so as to control a time width of an ON state when controlling. 6. A DC power supply circuit having first and second terminals, first and second switching elements connected in series between the first and second terminals, and First and second diodes connected in series between the first and second terminals, and the first switching element and the second switching element are alternately turned on at a constant cycle. A control circuit for off control, first and second capacitors connected in parallel to the first and second diodes, a connection midpoint of the first and second switching elements, and the first and second switching elements. A resonance inductance element connected between the connection point of the first diode and the second diode; and a load circuit connected in series with the inductance element or electromagnetically coupled to the inductance element, A first capacitor connected in parallel to the first and second capacitors
And a second capacitor short-circuit switching element, the second and first capacitor short-circuit switching elements are turned on in the first region of the on period of the first and second switching elements, and the load circuit And a control circuit of a switching element for short-circuiting a capacitor formed so as to control the time width of the ON state when controlling the voltage or current of the resonance type switching power supply circuit. 7. A DC power supply circuit having a first terminal, a second terminal, and a third terminal for applying a midpoint potential of the first and second terminals, and a primary winding having a center tap. A transformer provided therein; a series resonant circuit including an inductance element and a capacitor connected between the third terminal of the power supply circuit and the center tap of the primary winding; the first terminal; A first switching element connected between one end of the primary winding and a second switching element connected between the second terminal and the other end of the primary winding; A control circuit for alternately turning on and off the first and second switching elements at a constant cycle; a capacitor short-circuiting switching element connected in parallel with the capacitor; and a first and a second switching element. At least one of Switching element for capacitor short-circuit formed to control the time width of the on-state when controlling the voltage or current of the load circuit while turning on the switching element for short-circuiting the capacitor in an intermediate region of the on-state of And a control circuit for the resonant switching power supply circuit.