JPH09163734A - Power supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To control an L component by which a resonance frequency at the time of the current resonance is determined securely before the manufacture by a method wherein resonance inductors by which the resonance frequency of the current resonance is determined are provided and, further, the inductances of the resonance inductors are predetermined to be larger than the leakage inductance of a transformer. SOLUTION: Resonance inductors 14 and 15 and the self-inductance of the primary side of a transformer 5 form a combined inductance. A voltage resonance is produced by a parallel resonance composed of the combined inductance and voltage resonance capacitors 3 and 4 which are connected in parallel to respective switching devices 1 and 2 and, further, a current resonance is produced by a series resonance composed of the combined inducatance and a current resonance capacitor 6 provided on the secondary side of the transformer 5. At that time, the resonance inductors 14 and 15 by which the influence of the leakage inductance between the primary side and the secondary side of the transformer 5 is eliminated and the resonance frequency of the current resonance is determined are provided on the primary side and, further, the inductances of the resonance inductors 14 and 15 are predetermined to be larger than the leakage inductance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply circuit which is a switching power supply and utilizes voltage resonance and current resonance.

[0002]

2. Description of the Related Art Conventionally, as a switching power supply, generally, switching loss is greatly reduced to improve conversion efficiency, and a current operating waveform in a circuit is approximated to a sine wave to prevent reception interference to an AM tuner or the like. There has been a switching power supply that utilizes voltage resonance and current resonance in order to reduce noise for avoidance.

Among them, there has been a push-pull type resonance type power supply circuit in which two switching elements are used as switching elements and a direct current is obtained by alternately turning them on and off for high output.

A conventional power supply circuit which is a push-pull type resonance type switching power supply will be described below. FIG. 4 is a block diagram showing a conventional resonance type power supply circuit which is a kind of switching power supply. In FIG. 4, 1
And 2 are switching elements which are alternately turned on and off, 3
And 4 are voltage resonance capacitors for determining the resonance frequency of voltage resonance, and 5 is a DC-insulated primary winding 5a and secondary winding 5b. A transformer for transmitting the AC signal generated on the 5a side to the secondary winding 5b side and outputting from the secondary winding 5b side, 6
Is a current resonance capacitor for determining the resonance frequency of the current resonance, 7 and 8 are rectifying diodes that convert an AC signal output from the secondary winding 5b side of the transformer 5 into a DC signal, 9 is a choke coil, and 10 is A smoothing capacitor for smoothing the output signal of the choke coil 9, 11 is a load, and 18 and 19 are leakage inductances existing between the primary winding 5a side and the secondary winding 5b side of the transformer 5. Here, the choke coil 9 and the smoothing capacitor 10 form a smoothing circuit.

The operation of the power supply circuit configured as described above will be described below. First, when the switch elements 1 and 2 are repeatedly turned on and off alternately, the output voltage of the switch elements 1 and 2, that is, the 1 of the transformer 5
The input voltage to the primary side terminal on the side of the secondary winding 5a is an AC voltage having a peak value that is almost twice the voltage of the DC power supply 12, and the current input to the transformer 5 by applying this AC voltage is Rectifier diode 7 transmitted to the secondary side terminal on the secondary winding 5b side of 5 and connected to the secondary side terminal
After being rectified by 8 and 8, they are input to the current resonance capacitor 6 and the choke coil 9.

[0006] Here, the impedance of the choke coil 9 is the primary resonance of the current resonance capacitor 6 and the transformer 5.
Since the impedances of the leakage inductances 18 and 19 between the secondary circuits are sufficiently high, the current input to the current resonance capacitor 6 does not include the inductance of the choke coil 9 and the leakage inductances 18 and 19 of the transformer 5 and the current resonance capacitor 6. Current resonance is performed by series resonance with a combination of only six, and the resulting resonance current is smoothed by the choke coil 9 and the smoothing capacitor 10 and sent to the load 11.

While the switching element 1 is on, the rectifying diode 7 is reverse-biased and turned off when a half wave of the resonance current obtained as described above passes and the direction of the current is reversed. Therefore, series resonance is stopped. That is, the resonance automatically stops when the resonance current ends in half wave and the current returns to zero. After the resonance current becomes zero, nothing happens even if the switch element 1 is turned on continuously, but since it is inefficient because the time for which energy is not transmitted becomes long, it can be turned off with some margin. Good.
Further, since the resonance frequency by the leakage inductance 18 and the current resonance capacitor 6, that is, the resonance time is constant, the ON time of the switch element 1 may be a constant value.

Next, when the switch element 1 is turned off, that is, when the two switch elements 1 and 2 are both turned off, the current at the secondary side terminal of the transformer 5 becomes zero and the voltage of the switch element 1 becomes , The self-inductance of the transformer 5 and the voltage resonance capacitor 3 cause parallel resonance to start increasing with a constant time constant, and the voltage value is maintained at twice the voltage value of the DC power supply 12. When the switch element 2 is turned on at this timing, a resonance current in the opposite direction to the above starts to flow to the secondary side of the transformer 5.

By the above operation, the voltage resonance and the current resonance are alternately generated to make the voltage and the current in the circuit have a resonance waveform, thereby reducing the harmonic components contained in the voltage and the current applied to the switch element. It is also possible to reduce the loss when the voltage and current are turned on and off.

[0010]

However, in the conventional power supply circuit as described above, at the time of current resonance, as the L component of the L component and the C component constituting the time constant for determining the resonance frequency, Although the leakage inductances 18 and 19 between the primary and secondary sides of the transformer 5 are used, the values of the leakage inductances 18 and 19 are uncertain factors when designing the transformer and cannot be determined. You will need to manage and sort them later,
There is a problem that the productivity of the transformer is deteriorated, and consequently the cost of the transformer is increased.

Further, variations in the leakage inductances 18 and 19 cause variations in the current resonance frequency.
When the adjustment for frequency correction with respect to the variation of the resonance frequency is performed, it is necessary to change the capacity of the current resonance capacitor 6, and depending on the case, the current resonance capacitor 6 may be changed.
Since it is necessary to increase the capacity of the capacitor, there is also a problem that the cost of the capacitor becomes high as a result.

The present invention solves the above-mentioned conventional problems. It is possible to reliably manage the L component that determines the resonance frequency at the time of current resonance before manufacturing, and to suppress variations in the current resonance frequency. Provided is a power supply circuit capable of eliminating the troublesome adjustment for frequency correction with respect to this variation and, as a result, improving the productivity and reducing the production cost.

[0013]

In order to solve the above problems, the power supply circuit according to claim 1 of the present invention supplies another direct current obtained by a switching method from a direct current power supply which is a power source for a load. In a power supply circuit that uses voltage resonance and current resonance when supplying to a load and obtaining the other direct current, it is galvanically isolated from a switch element that turns on and off a direct current signal from the direct current power source to convert it into an alternating current signal. A leakage inductance is formed between the primary side and the secondary side, an AC signal from the switch element is supplied to the primary side, and the transformer outputs the AC signal from the secondary side; A voltage resonance capacitor, which is connected in parallel to both ends and serves as a determinant of the resonance frequency of voltage resonance, together with the primary winding of the transformer, and a series connection with the primary winding of the transformer and the switch element A resonance inductor connected to the transformer, a rectifying unit for rectifying an AC signal output from the secondary side of the transformer, and a current connected in parallel to the output terminal of the rectifying unit and serving as a determining factor of the resonance frequency of the current resonance. A resonance capacitor; and a smoothing unit having an inductance component and a capacitance component for smoothing the signal rectified by the rectification unit and outputting the other direct current. It is configured to be sufficiently larger than the inductance and sufficiently smaller than the inductance component of the smoothing means.

According to this structure, when determining the resonance frequency of the current resonance, the influence of the leakage inductance of the transformer is eliminated, and the resonance inductor provided on the primary side of the transformer and the current resonance provided on the secondary side of the transformer. The capacitor alone determines the current resonance frequency with certainty.

When the resonance frequency of the voltage resonance is determined, the voltage resonance frequency is calculated by using the combined inductance of the resonance inductor provided on the primary side of the transformer and the self-inductance of the primary side of the transformer as the L component for that purpose. decide.

In the power supply circuit according to a second aspect of the present invention, when another DC is obtained by a switching method from a DC power source which is a power source for the load and the other DC is obtained, In a power supply circuit using voltage resonance and current resonance, a switching element for turning on / off a DC signal from the DC power supply to convert it into an AC signal, and a leakage inductance between a DC side-insulated primary side and a secondary side. And a transformer for supplying an AC signal from the switching element to the primary side and outputting the AC signal from the secondary side, and a winding on the primary side of the transformer connected in parallel to both ends of the switching element. A voltage resonance capacitor that is a determining factor of the resonance frequency of voltage resonance together with the line, a rectifying unit that rectifies an AC signal output from the secondary side of the transformer, and a winding on the secondary side of the transformer A resonance inductor connected in series to the rectification unit, a current resonance capacitor connected in parallel to the output terminal of the rectification unit and serving as a determining factor of the resonance frequency of the current resonance, and a signal rectified by the rectification unit is smoothed. Then, the resonance inductor is provided with a smoothing means having an inductance component and a capacitance component for outputting the other direct current, and the resonance inductor has a sufficiently larger inductance than the leakage inductance, and is greater than the inductance component of the smoothing means. Configure it to be sufficiently small.

According to this structure, when determining the resonance frequency of the current resonance, the influence of the leakage inductance of the transformer is eliminated, and the current resonance frequency is ensured only by the resonance inductor and the current resonance capacitor provided on the secondary side of the transformer. To decide.

The determination of the current resonance frequency is performed independently of the voltage resonance system on the primary side of the transformer, and the current resonance frequency is adjusted only by changing the inductance of the resonance inductor provided on the secondary side of the transformer. .

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, a power supply circuit showing an embodiment of the present invention will be described with reference to the drawings.

A power supply circuit showing the first embodiment will be described. FIG. 1 is a block diagram of a power supply circuit showing a first embodiment, and FIG. 3 shows operation timings and operation waveforms of respective parts.

In FIG. 1, reference numerals 14 and 15 denote resonance inductors provided as characteristic components in the power supply circuit according to the present embodiment, which form a combined inductance with the self-inductance on the primary side of the transformer 5. By doing so, the combined inductance and the voltage resonance capacitors 3 and 4 connected in parallel to the respective switch elements 1 and 2
And voltage resonance by parallel resonance, and the transformer 5
The current resonance capacitor 6 provided on the secondary side of the current resonance performs current resonance by series resonance. Other configurations are similar to those of the conventional example shown in FIG. 4, and therefore description thereof will be omitted here.

The operation of the power supply circuit configured as above will be described below. First, the switching elements 1 and 2 are respectively V _{g1 in} FIG. 3 (g) and FIG. 3 (h).
When the gate voltage is repeatedly turned on and off at the timing of V _g2, the voltage values applied to the switch element 1 and the switch element 2 are V _{S1 in} FIG. 3A and V in FIG. 3B.
_As indicated by _S2 , the voltage V _i of the DC power supply 12 is almost twice (2V _i ), and when any one of the switch elements 1 and 2 is on, the voltage is sequentially generated from the primary side of the transformer 5. The current is sequentially input to the rectifying diodes 7 and 8 as the rectifying unit via the secondary side of the transformer 5.

The DC currents sequentially output from the rectifying diodes 7 and 8 are sequentially input to the current resonance capacitor 6 and the choke coil 9 as an inductance component forming the smoothing means. At this time, when the load 11 is not connected, that is, when there is no load, the currents i _S1 and i _S2 generated from the primary side of the transformer 5 are as shown by the dotted lines in FIGS. 3C and _3D. Only the excitation current waveform is used. Further, the current input to the choke coil 9 is smoothed by the smoothing capacitor 10.

Here, the switch element 1 is turned on, that is, as shown in FIG.
When V _{g1 of} (g) becomes high, the rectifying diode 7 is forward biased, so that the charge current flows into the smoothing capacitor 10. At this time, the conditions for performing current resonance are the switching element 1 and If the impedance of the rectifier diode 7 is sufficiently small, the choke coil 9
Of the transformer >> and the leakage inductance of the transformer 5 and the inductance of the resonance inductor 14 >> the leakage inductance of the transformer 5,
It is necessary to make the impedance of the choke coil 9 sufficiently high.

As the values, for example, the inductance of the choke coil 9 is 3 [mH], the self-inductance of the primary side of the transformer 5 is 5 [mH], the leakage inductance is 5 [μH], and the resonance inductors 14 and 15 have the following values. The inductance is set to 50 [μH].

In general, the actual leakage inductance of the transformer has a large variation with respect to the above value,
In particular, it is necessary to make the values of the resonance inductors 14 and 15 sufficiently large.

When the load 11 is connected while the switch element 1 is on under the above conditions, the secondary side current of the transformer 5 is the inductance of the resonance inductor 14 and the current resonance capacitor 6. Of the series resonance current. The resonance current on the secondary side of the transformer 5 when this load is taken out has a waveform as shown by i _L1 in FIG. 3E, and the primary side current i _S1 of the transformer 5 at the same timing is as shown in FIG. The waveform is as shown by the solid line in (c).

The secondary side resonance currents i _L1 and i _L2 are shown in FIG.
As shown in (e) and (f), the rectifier diode 7 is reversely biased and turned off when a half wave has passed and the direction of the current is reversed, so that series resonance cannot be performed and resonance ends.
That is, the resonance automatically stops when the resonance current ends in half wave and the current becomes zero. Therefore, in order to end the resonance at zero current, it is necessary to keep the switch element 1 ON until the resonance current returns to zero.

Next, when the switch element 1 is turned off, the self-inductance of the transformer 5 and the resonance inductor 14
Since the operation is performed by parallel resonance between the combined inductance of and the voltage resonance capacitor 3 connected in parallel with the switch element 1, as shown by V _S1 in FIG. The parallel resonance period is during this inclination. Furthermore, the charge continues and Fig. 3
When the voltage value V _S1 of (a) rises and becomes almost the same value as + 2V _i , the parallel resonance ends.

On the other hand, at the timing when the switch element 1 is turned off, the self-inductance of the transformer 5 and the combined inductance of the resonance inductor 14 and the parallel resonance with the voltage resonance capacitor 3 cause the resonance as shown in FIG.
Since the primary side current i _S1 flows in the positive direction, the switching element 2
The electric charge that has been charged into the switch element 2 is discharged, and the voltage value V _S2 of the switch element 2 drops with a slope as shown in FIG.

The inclination at this time is similar to that at the time of charging,
This corresponds to parallel resonance performed with a time constant determined by the combined inductance of the self-inductance of the transformer 5 and the resonance inductor and the voltage resonance capacitor 3.

When the discharge ends and the parallel resonance also ends, and then the switch element 2 turns on, that is, V _{g2 in} FIG. 3 (h) becomes high, as shown in FIG. 3 (b), the primary current i _{As S2} starts to flow in the forward direction, 2 of transformer 5
The current i _L2 output from the next side is charged into the smoothing capacitor 10 via the choke coil 9 after passing through the rectifying diode 8 and also causes current resonance by the series resonance of the resonance inductor 15 and the current resonance capacitor 6. Therefore, a current waveform as shown by i _L2 in FIG. 3 (f) is obtained.

By repeating the above operation, the switch elements 1 and 2 perform the push-pull operation to drive the transformer 5. Therefore, the secondary current output through the transformer 5 is rectified by the rectifying diodes 7 and 8,
Further, the smoothing capacitor 10 is charged through the choke coil 9.

At this time, the inductance of the choke coil 9 >> the inductance of the resonance inductors 14 and 15 >> is set so that the leakage inductance of the transformer 5 is set. Therefore, the series resonance between the resonance inductors 14 and 15 and the current resonance capacitor 6 is performed. As a result, a resonance current is output from the secondary side of the transformer 5.

As described above, the voltage resonance capacitor connected in parallel with the two switch elements of the push-pull circuit,
Parallel resonance is caused by the self-inductance of the transformer and the combined inductance of the resonance inductor to cause voltage resonance, and series resonance is performed by the current resonance capacitor and the resonance inductor in order to resonate the secondary side current of the transformer.

When the voltage resonance and the current resonance are alternately performed, a resonance inductor that eliminates the influence of the leakage inductance and determines the resonance frequency of the current resonance is provided on the primary side, and the inductance of the resonance inductor is the primary or secondary of the transformer.
Set sufficiently larger than the next leakage inductance.

By doing so, the current resonance frequency can be reliably determined, and the voltage resonance frequency is determined by the combined inductance of the resonance inductor provided on the primary side and the self-inductance of the transformer primary side. Therefore, it is possible to reduce the capacitance of the voltage resonance capacitor when the voltage resonance frequency is the same.

A power supply circuit according to the second embodiment will be described. FIG. 2 is a block diagram of a power supply circuit showing a second embodiment, and description will be given here also with reference to FIG.

In FIG. 2, reference numerals 16 and 17 denote resonance inductors provided as characteristic components in the power supply circuit according to the present embodiment, and a current resonance capacitor 6 provided on the secondary side of the transformer 5. Current resonance is performed by series resonance. Other configurations are similar to those of the conventional example shown in FIG. 4, and therefore description thereof will be omitted here.

The operation of the power supply circuit configured as described above will be described below. First, the switching elements 1 and 2 are respectively V _{g1 in} FIG. 3 (g) and FIG. 3 (h).
When the gate voltage is repeatedly turned on and off at the timing of V _g2, the voltage values applied to the switch element 1 and the switch element 2 are V _{S1 in} FIG. 3A and V in FIG. 3B.
_As indicated by _S2 , the voltage V _i of the DC power supply 12 is almost twice (2V _i ), and when any one of the switch elements 1 and 2 is on, the voltage is sequentially generated from the primary side of the transformer 5. The current is sequentially input to the rectifier diodes 7 and 8 via the secondary side of the transformer 5.

The DC current sequentially output from the rectifying diodes 7 and 8 is sequentially input to the current resonance capacitor 6 and the choke coil 9. At this time, when the load 11 is not connected, that is, when there is no load, the currents i _S1 and i _S2 generated from the primary side of the transformer 5 are as shown by the dotted lines in FIGS. 3C and _3D. Only the excitation current waveform is used. Further, the current input to the choke coil 9 is smoothed by the smoothing capacitor 10.

Here, the switch element 1 is turned on, that is, as shown in FIG.
When V _{g1 of} (g) becomes high, the rectifying diode 7 is forward biased, so that the charge current flows into the smoothing capacitor 10. At this time, the conditions for performing current resonance are the switching element 1 and If the impedance of the rectifier diode 7 is sufficiently small, the choke coil 9
Of the transformer >> and the leakage inductance of the transformer 5 and the inductance of the resonance inductor 16 >> the leakage inductance of the transformer 5,
It is necessary to make the impedance of the choke coil 9 sufficiently high.

As the values, for example, the inductance of the choke coil 9 is 3 [mH], the self-inductance of the primary side of the transformer 5 is 5 [mH], the leakage inductance is 5 [μH], and the resonance inductors 16 and 17 have the following values. The inductance is set to 50 [μH].

In general, the actual leakage inductance of the transformer has a large variation with respect to the above value,
In particular, it is necessary to make the values of the resonance inductors 16 and 17 sufficiently large.

When the load 11 is connected while the switch element 1 is on under the above conditions, the current on the secondary side of the transformer 5 is the inductance of the resonance inductor 16 and the current resonance capacitor 6. Of the series resonance current. The resonance current on the secondary side of the transformer 5 when this load is taken out has a waveform as shown by i _L1 in FIG. 3E, and the primary side current i _S1 of the transformer 5 at the same timing is as shown in FIG. The waveform is as shown by the solid line in (c).

The secondary side resonance currents i _L1 and i _L2 are shown in FIG.
As shown in (e) and (f), the rectifier diode 7 is reversely biased and turned off when a half wave has passed and the direction of the current is reversed, so that series resonance cannot be performed and resonance ends.
That is, the resonance automatically stops when the resonance current ends in half wave and the current becomes zero. Therefore, in order to end the resonance at zero current, it is necessary to keep the switch element 1 ON until the resonance current returns to zero.

Next, when the switch element 1 is turned off, the self-inductance of the transformer 5 and the voltage resonance capacitor 3 connected in parallel with the switch element 1 operate in parallel, so that V in FIG. _As shown in _S1 , the voltage waveform has a rising slope, and the period of this slope is the parallel resonance period. Further, when the charging is continued and the voltage value V _{S1 in} FIG. 3A rises and becomes almost the same value as + 2V _i , the parallel resonance ends.

On the other hand, at the timing when the switch element 1 is turned off, the primary side current i _S1 is in the positive direction as shown in FIG. 3C due to the parallel resonance of the self-inductance of the transformer 5 and the voltage resonance capacitor 3. Flow into the switch element 2, the charge charged in the switch element 2 is discharged, and the voltage value V _S2 of the switch element 2 drops with a slope as shown in FIG. 3B. The slope at this time corresponds to the parallel resonance performed with the time constant determined by the self-inductance of the transformer 5 and the voltage resonance capacitor 3, as in the case of charging.

When the discharge ends and the parallel resonance also ends, and then the switch element 2 turns on, that is, when V _{g2 in} FIG. 3 (h) becomes high, as shown in FIG. 3 (b), the primary current i _{As S2} starts to flow in the forward direction, 2 of transformer 5
The current i _L2 output from the next side is charged into the smoothing capacitor 10 via the choke coil 9 after passing through the rectifying diode 8 and also causes current resonance by the series resonance of the resonance inductor 17 and the current resonance capacitor 6. Therefore, a current waveform as shown by i _L2 in FIG. 3 (f) is obtained.

By repeating the above operation, the switch elements 1 and 2 perform the push-pull operation to drive the transformer 5. Therefore, the secondary current output through the transformer 5 is rectified by the rectifying diodes 7 and 8,
Further, the smoothing capacitor 10 is charged through the choke coil 9.

At this time, since the inductance of the choke coil 9 >> the inductance of the resonance inductors 16 and 17 >> the leakage inductance of the transformer 5, the series resonance between the resonance inductors 16 and 17 and the current resonance capacitor 6 is performed. As a result, a resonance current is output from the secondary side of the transformer 5.

As described above, the voltage resonance capacitor connected in parallel with the two switch elements of the push-pull circuit,
Parallel resonance is caused by the self-inductance of the transformer to perform voltage resonance, and series resonance is performed by the current resonance capacitor and the resonance inductor in order to resonate the secondary side current of the transformer.

When the voltage resonance and the current resonance are alternately performed, a resonance inductor that determines the resonance frequency of the current resonance by eliminating the influence of the leakage inductance is provided on the secondary side, and the inductance of the resonance inductor is the primary or secondary of the transformer.
Set sufficiently larger than the next leakage inductance.

By doing so, the current resonance frequency can be reliably determined, the voltage resonance frequency can be adjusted only by the voltage resonance capacitor and the self-inductance of the transformer primary side, and the current resonance frequency can be adjusted. The frequency can be adjusted only by the current resonance capacitor and the resonance inductor provided on the secondary side of the transformer. That is, the current resonance frequency can be individually adjusted without changing the voltage resonance frequency, only by changing the inductance of the resonance inductor provided on the secondary side of the transformer, without increasing the capacitance of the capacitor. Therefore, the productivity can be improved, and the production cost can be reduced.

In each of the above-mentioned embodiments, it is preferable to use the MOS-FETs as the switch elements 1 and 2 since the loss of the elements themselves is small and they are easy to drive.

[0056]

As described above, according to the present invention, when determining the resonance frequency of the current resonance, the influence of the leakage inductance of the transformer is eliminated and the resonance inductor and the transformer provided on the primary side of the transformer are eliminated. The current resonance frequency can be reliably determined only by the current resonance capacitor provided on the secondary side, and when determining the resonance frequency of the voltage resonance, it is provided on the primary side of the transformer as an L component for that purpose. The voltage resonance frequency can be determined using the combined inductance of the resonance inductor and the primary side self-inductance of the transformer.

Further, when determining the resonance frequency of the current resonance, the influence of the leakage inductance of the transformer is eliminated and the current resonance frequency is reliably determined only by the resonance inductor and the current resonance capacitor provided on the secondary side of the transformer. In addition, the current resonance frequency can be determined independently of the voltage resonance system on the primary side of the transformer, and only by changing the inductance of the resonance inductor provided on the secondary side of the transformer. The current resonance frequency can be adjusted.

Therefore, the L component that determines the resonance frequency at the time of current resonance can be reliably managed before manufacturing, and the variation of the current resonance frequency can be suppressed to eliminate the troublesome adjustment for frequency correction for this variation. As a result, the productivity can be improved and the production cost can be reduced.

When the resonance inductor is provided on the primary side, when the output of the transformer is stepped down, the primary side current handles a smaller current value than the secondary side current, and the current capacity of the resonance inductor is small. Since it can be made smaller, the cost can be reduced.

Further, when the resonance inductor is provided on the secondary side, when the output of the transformer is boosted, the secondary side current handles a smaller current value than the primary side current, and the current capacity of the resonance inductor is small. Since the voltage can be reduced, the cost can be reduced, and when the output of the transformer is stepped down, the voltage value applied to the resonant inductor is reduced, so that the mounting density of components can be increased and space saving can be achieved. You can enable it.

[Brief description of the drawings]

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

FIG. 2 is a block diagram of a power supply circuit according to a second embodiment of the present invention.

FIG. 3 is an operation waveform diagram in the power supply circuit according to the first and second embodiments of the present invention.

FIG. 4 is a block diagram showing a configuration of a conventional power supply circuit.

[Explanation of symbols]

 1, 2 switch elements 3, 4 voltage resonance capacitor 5 transformer 6 current resonance capacitor 7, 8 rectifying diode 9 choke coil 10 smoothing capacitor 14, 15, 16, 17 resonance inductor

Claims (5)

[Claims] 1. A power supply circuit using voltage resonance and current resonance when supplying another DC obtained by a switching method from a DC power source, which is a power source for a load, to obtain the other DC, A leakage inductance is formed between a switching element that turns on and off a direct current signal from the direct current power source and converts it into an alternating current signal, and a primary side and a secondary side that are galvanically isolated, and the switching element is provided on the primary side. From the secondary side of the transformer, which is supplied with the AC signal from the secondary side, and the primary side winding of the transformer, which is connected in parallel to both ends of the switch element, and a determining element of the resonance frequency of the voltage resonance. A voltage resonance capacitor, a resonance inductor serially connected to the primary winding of the transformer and a switch element, and an AC signal output from the secondary side of the transformer. A rectifying unit that flows, a current resonant capacitor that is connected in parallel to the output terminal of the rectifying unit and serves as a determining factor of the resonant frequency of the current resonance, and a signal rectified by the rectifying unit is smoothed to generate another direct current. A power supply comprising a smoothing means having an inductance component and a capacitance component for outputting, and the resonance inductor having a inductance sufficiently larger than the leakage inductance and sufficiently smaller than the inductance component of the smoothing means. circuit. 2. A power supply circuit that uses voltage resonance and current resonance when supplying another direct current obtained by a switching method from a direct current power source, which is a power source for a load, to the load to obtain the different direct current, A leakage inductance is formed between a switching element that turns on and off a direct current signal from the direct current power source and converts it into an alternating current signal, and a primary side and a secondary side that are galvanically isolated, and the switching element is provided on the primary side. From the secondary side of the transformer, which is supplied with the AC signal from the secondary side, and the primary side winding of the transformer, which is connected in parallel to both ends of the switch element, and a determining element of the resonance frequency of the voltage resonance. Voltage resonating capacitor, a rectifying unit that rectifies an AC signal output from the secondary side of the transformer, and a resonance input connected in series to the secondary winding and the rectifying unit of the transformer. A ductor, a current resonance capacitor connected in parallel to the output terminal of the rectification unit and serving as a determining factor of the resonance frequency of the current resonance, and a signal rectified by the rectification unit for smoothing and outputting the other direct current. And a smoothing means having an inductance component and a capacitance component, and the resonance inductor is configured so that its inductance is sufficiently larger than the leakage inductance and sufficiently smaller than the inductance component of the smoothing means. 3. The power supply circuit according to claim 1, wherein the voltage resonance capacitor is configured such that its capacitance is sufficiently larger than the stray capacitance of the switch element. 4. The power supply circuit according to claim 1, wherein the current resonance capacitor is configured so that its capacitance is sufficiently smaller than the capacitance component in the smoothing means. 5. The power supply circuit according to any one of claims 1 to 4, wherein each of the switch elements, the transformer, the voltage resonance capacitor, the resonance inductor, and the rectifying unit is used in a push-pull configuration.