JP3463280B2 - Switching power supply - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallel operation type resonant switching power supply in which a plurality of resonant converter circuits are connected in parallel.

[0002]

2. Description of the Related Art Resonant type switching power supplies have been attracting attention as switching power supplies that can achieve high efficiency and low noise. The resonance type switching power supply switches a direct current power supply by a switching circuit, resonates a switching output by the resonance circuit, takes out the resonance output through a winding of a transformer, converts it into a direct current, and outputs it.

In the resonance type switching power supply, a parallel operation system in which a plurality of resonance type DC-DC converter circuits are connected in parallel may be adopted for the purpose of increasing the power to be converted and performing the redundant operation.

Conventionally, as a means for performing parallel operation using a plurality of resonance type switching power supplies, a plurality of switching power supplies are connected in parallel and their output currents are detected so that the output currents of the respective switching power supplies are almost the same. It controlled independently so that it might become equal.

However, such a parallel operation system requires the same number of control circuits as the number of switching power supplies.
This leads to higher prices and larger equipment.

The output stabilization control of the resonance type switching power supply is executed by controlling the switching frequency and changing the impedance of the resonance circuit. However, the circuit constant values of the resonance capacitor and the resonance inductor that form the resonance circuit are usually different between the resonance type switching power supplies, and therefore the switching frequency is different in each resonance type switching power supply. Therefore, when trying to equalize the shared currents of the individual switching power supplies, frequency beat noise occurs, which causes a problem of unstable control.

When one control circuit is shared by a plurality of resonance type switching power supplies, control can be performed synchronously at the same frequency, so that frequency beat noise is generated and control instability can be avoided. However, in this case, zero volt switching (hereinafter referred to as ZVS) becomes difficult. That is, in a plurality of resonant switching power supplies that are operated in parallel, if the impedance of the resonant circuit is different due to variations in the constant values of the circuit elements, etc. Since the energy already stored in the resonant circuit has been discharged, the current may become almost zero, which makes ZVS impossible.

US Pat. No. 4,648,020 discloses a technique for matching the constant value of a resonant circuit in each switching power supply, thereby balancing the load sharing of each resonant switching power supply. There is.
However, in the case of this technology, it is necessary to select the circuit elements that make up the resonance circuit, resulting in a decrease in productivity,
An imbalance in load sharing occurs due to the selection allowable range. A similar problem also occurs due to changes in circuit elements over time.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a parallel operation type resonant switching power supply which can be reduced in price and downsized.

Another object of the present invention is to provide a resonance type switching power supply of a parallel operation system capable of avoiding generation of frequency beat noise and instability of control.

Yet another object of the present invention is to provide a parallel operation type resonant switching power supply capable of ZVS.

Still another object of the present invention is to use a parallel operation system which does not require selection of circuit elements constituting a resonance circuit, reduces productivity, and avoids imbalance in load sharing due to circuit elements. It is to provide a resonant switching power supply.

A further object of the present invention is to provide a parallel operation type resonant switching power supply which is easy to design a converter circuit and mount on a circuit board.

Still another object of the present invention is to provide resonance type switching in which impedances between resonance circuits are balanced, a circulating current caused by impedance imbalance is prevented from flowing, and a failure caused by the circulating current can be avoided. To provide power.

[0015]

In order to solve the above problems, the switching power supply according to the present invention includes a plurality of converter circuits. Each of the plurality of converter circuits includes two switching elements, a transformer, a resonance circuit, and an output rectifying / smoothing circuit.

The two switching elements are connected in series, and both ends of the series circuit are led to a DC power source and driven alternately. The transformer has at least a primary winding,
A secondary winding, and the primary windings of the transformer provided in each of the plurality of converter circuits are connected in parallel with each other.

The resonance circuit is connected in series to the primary winding of the transformer, and both ends of a series circuit formed by the resonance circuit and the primary winding of the transformer are connected to the two switching elements. Connection point and the above 2
It is connected between one end of the series circuit composed of two switching elements.

The resonance circuit includes a resonance capacitor and a resonance inductor. The resonance capacitors are individually provided for the plurality of converter circuits and are connected in parallel with each other. The resonance inductor is
The converter circuits are individually provided for the plurality of converter circuits and are connected in parallel with each other.

The output rectifying / smoothing circuit is connected to the secondary winding of the transformer, and its output end is commonly connected to the plurality of converter circuits.

In the switching power supply according to the present invention,
Each of the converter circuits provided in plurality switches the input DC power supply by alternately operating two switching elements connected in series, and supplies the switching output to the resonance circuit and the primary winding of the transformer. To do.

In the switching power supply according to the present invention,
Both ends of a series circuit in which a resonance circuit and a primary winding of a transformer are connected in series are connected between a connection point of the two switching elements and one end of a series circuit configured by the two switching elements. Therefore, due to the alternating operation of the two switching elements, a pseudo sine wave current corresponding to the resonance frequency of the resonance circuit flows through the resonance circuit and the primary winding of the transformer. At this time, an induced voltage is generated in the secondary winding coupled to the primary winding. This induced voltage is converted to direct current by the output rectifying and smoothing circuit connected to the secondary winding of the transformer,
Is output.

Since the output terminals of the output rectifying / smoothing circuit are commonly connected to a plurality of converter circuits, a parallel operation type resonant switching power supply for supplying the outputs of the plurality of converter circuits to the load in common is obtained. .

In the parallel operation type resonance type switching power supply as described above, the primary windings of the transformers provided in each of the plurality of converter circuits are connected in parallel to each other, and further, for resonance included in the plurality of converter circuits. Each of the capacitors and each of the resonance inductors are connected to each other. Therefore, when viewed from the switching element side, the impedances of the resonance circuit and the primary winding of the transformer are equal to each other in the plurality of converter circuits. Therefore, it is possible to operate a plurality of converter circuits in synchronization with each other at the same frequency to avoid occurrence of frequency beat noise and instability of control. This means that one control circuit can be used to control a plurality of converter circuits. Therefore, it is possible to realize a parallel operation type resonant switching power supply that can be reduced in price and downsized.

Moreover, since the impedances of the resonance circuit seen from the switching element side are equal to each other in the plurality of converter circuits, a predetermined resonance current can flow and ZVS can be performed.

As a means for matching the resonance characteristics of the resonance circuits included in the plurality of converter circuits, a method of connecting the resonance circuits as a whole in parallel can be considered. However, the resonance circuits included in the plurality of converter circuits usually have different resonance characteristics due to the difference in characteristics of the resonance capacitor and the resonance inductor. When a plurality of resonance circuits having such different resonance characteristics are connected in parallel, a large resonance current (circulation current) flows from the resonance circuit having a high impedance to the resonance circuit having a low impedance. Due to this circulating current, the resonance capacitor and the resonance inductor may generate heat abnormally, and the safety of the circuit may be degraded. Further, a large circulating current may cause the resonance inductor to be magnetically saturated, lose its function, and cause a circuit operation failure of the converter.

On the other hand, in the switching power supply according to the present invention, the impedances of the resonance circuits are completely equal to each other in the plurality of converter circuits when viewed from the switching element side, so that the impedance imbalance between the resonance circuits is unbalanced. There is no circulating current due to. Therefore, the above-mentioned trouble caused by the circulating current does not occur.

Moreover, it is not necessary to select the circuit elements that form the resonance circuit, and it is possible to avoid a decrease in productivity and an imbalance in load sharing due to the circuit elements.

Further, since the resonance capacitor and the resonance inductor are individually provided for each of the plurality of converter circuits, the plurality of converter circuits have substantially the same symmetrical circuit configuration. Therefore, the converter circuit can be easily designed and mounted on the circuit board.

The present invention further discloses specific circuit connections for equalizing the impedance of the resonant circuit in a plurality of converter circuits.

Other objects, structures and advantages of the present invention will be described in more detail with reference to the accompanying drawings. However, the attached drawings merely show examples.

[0031]

FIG. 1 is an electric circuit diagram of a switching power supply according to the present invention. As shown, the switching power supply according to the present invention has a plurality of converter circuits A and B. Reference numeral 9 is a control circuit, and 10 is a DC power supply. In the embodiment, the number of converter circuits A and B is two, but the number may be more. The converter circuits A and B have almost the same circuit configuration.

First, the converter circuit A has a switching circuit 1, a resonance circuit 3, a transformer 5, and an output rectifying / smoothing circuit 7.

The switching circuit 1 switches the input DC power source Vin. The switching circuit 1 is
It has a first switching element 11 and a second switching element 12. First switching element 11 and second
The switching element 12 is composed of an FET or the like, the main circuits of which are connected in series with each other, and both ends of the switching element 12 of the DC power supply device 1 are connected.
It is connected to 0. The DC power supply device 10 is usually configured as a rectifying / smoothing circuit that converts an AC power supply into a DC. The DC power supply device 10 may be provided as a part of the switching power supply device or may be an external element.

The transformer 5 has at least a primary winding 51.
And a secondary winding 52. The embodiment shows a secondary winding structure suitable when the output rectifying / smoothing circuit 7 is a double wave rectifying circuit system. The secondary winding 52 is the first winding 521.
And the second winding 522, the first winding 521 and the second winding 522 are connected to each other at one end.

The resonance circuit 3 includes a resonance capacitor 31 and
And a resonance inductor 32. Resonance capacitor 3
1 and the resonance inductor 32 are connected in a circuit loop including the switching circuit 1 and the primary winding 51 of the transformer 5. In the embodiment, one end of the resonance capacitor 31 is connected to the connection point of the switching elements 11 and 12, and the resonance inductor 3 is connected to the other end of the resonance capacitor 31.
One end of 2 is connected. The other end of the resonance inductor 32 is connected to one end of the primary winding 51 of the transformer 5. Therefore, the resonance circuit 3 constitutes a series resonance circuit including the resonance capacitor 31 and the resonance inductor 32.

The output rectifying / smoothing circuit 7 is connected to the secondary winding 52 of the transformer 5 and converts the induced voltage generated in the secondary winding 52 into direct current and outputs it. The illustrated output rectifying / smoothing circuit 7 is a choke input type having an output choke coil 70 and an output smoothing capacitor 71, but may be a capacitor input type. The secondary winding 52 of the transformer 5 includes a first winding 521 and a second winding 522, and the first winding 521 and the second winding 522 are connected in series. The rectifier circuit 72 is the first diode 721.
And a second diode 722. The anode of the first diode 721 is connected to the other end of the first winding 521, and the anode of the second diode 722 is connected to the other end of the second winding 522. First diode 72
The cathodes of the first and second diodes 722 are connected to each other and to one end of the choke coil 70. The other end of the choke coil 70 is connected to one end of an output smoothing capacitor 71 and is further led to one of the output terminals.
The other end of the output smoothing capacitor 71 is connected to the connection point of the first winding 521 and the second winding 522, and is further guided to the other of the output terminals.

Next, the converter circuit B has a switching circuit 2, a resonance circuit 4, a transformer 6, and an output rectifying / smoothing circuit 8. The switching circuit 2 switches the input DC power supply Vin. The switching circuit 2 has a first switching element 21 and a second switching element 22. The first switching element 21 and the second switching element 22 are FETs and the like, and their main circuits are connected in series with each other, and both ends thereof are connected to the DC power supply device 10.

The transformer 6 has at least a primary winding 61.
And a secondary winding 62. The embodiment shows a secondary winding structure suitable when the output rectifying / smoothing circuit 8 is a double-wave rectifying circuit system. The secondary winding 62 is a first winding 621.
And two windings of the second winding 622, one end of each of the first winding 621 and the second winding 622 is connected to each other.

The resonance circuit 4 includes a resonance capacitor 41,
And a resonance inductor 42. Resonance capacitor 4
1 and the resonance inductor 42 are connected in a circuit loop including the switching circuit 2 and the primary winding 61 of the transformer 6. In the embodiment, one end of the resonance capacitor 41 is connected to the connection point of the switching elements 21 and 22, and the resonance inductor 4 is connected to the other end of the resonance capacitor 41.
One end of 2 is connected. The other end of the resonance inductor 42 is connected to one end of the primary winding 61 of the transformer 6.

The output rectifying / smoothing circuit 8 is connected to the secondary winding 62 of the transformer 6 and converts the induced voltage generated in the secondary winding 62 into direct current and outputs it. The illustrated output rectifying / smoothing circuit 8 is a choke input type having an output choke coil 80 and an output smoothing capacitor 81, but may be a capacitor input type. The secondary winding 62 of the transformer 6 includes a first winding 621 and a second winding 622, and the first winding 621 and the second winding 622 are connected in series. The rectifier circuit 82 includes a first diode 821.
And a second diode 822. The anode of the first diode 821 is connected to the other end of the first winding 621, and the anode of the second diode 822 is connected to the other end of the second winding 622. First diode 82
The cathodes of the first and second diodes 822 are connected to each other and to one end of the choke coil 80. The other end of the choke coil 80 is connected to one end of an output smoothing capacitor 81 and further led to one of the output terminals.
The other end of the output smoothing capacitor 81 is connected to the connection point of the first winding 621 and the second winding 622, and is further guided to the other of the output terminals.

The output rectifying / smoothing circuit 7 provided in the converter circuit A and the output rectifying circuit 8 provided in the converter circuit B have their output terminals connected in common, and apply a DC output voltage Vo to a load (not shown). Supply.

Further, as an important feature of the present invention, the transformers 5 and 6 provided in the converter circuits A and B, respectively.
The primary windings 51 and 61 are connected in parallel with each other.
In addition, the resonance circuits 3 and 4 included in the converter circuits A and B
Are connected to each other. By that connection,
The capacitance values of the capacitors 31 and 41 and the inductance values of the inductors 32 and 42 are averaged. Further, the exciting inductances of the primary windings 51 and 61 of the transformers 5 and 6 and the inductance values of the output choke coils 70 and 80 converted to the primary side via the transformers 5 and 6 are also averaged. In the embodiment, the resonance circuit 3 of the converter circuit A and the resonance circuit 4 of the converter circuit B are used.
In, the capacitor 31 and the capacitor 41 are connected in parallel with each other, and the inductor 32 and the inductor 42 are connected in parallel with each other. As described above, one end of the resonance capacitor 31 is connected to the connection point of the switching elements 11 and 12, and the switching elements 21 and 22 are connected.
One end of the resonance capacitor 41 is connected to the connection point of.

The control circuit 9 controls the switching circuits 1 and 2 so that the output voltage Vo output from the output rectifying / smoothing circuits 7 and 8 becomes constant. The control circuit 9 also gives a control signal to the switching elements (11, 12), (21, 22), and the switching elements (11, 12), (21,
22) is operated in a frequency range higher than the resonance frequency of the resonance circuits 3 and 4. The control circuit 6 is composed of, for example, a voltage controlled oscillator (VCO) whose frequency is controlled by voltage.

In the switching power supply described above, in the converter circuit A, the switching elements 11 and 12 connected in series are alternately operated to switch the input DC power supply Vin, and the switching output thereof is used as the resonance circuit 3 and. It is supplied to the primary winding 51 of the transformer 5.

A connection point between the switching elements 11 and 12, and
Since both ends of a series circuit in which the resonance circuit 3 and the primary winding 51 of the transformer 5 are connected in series are connected between one end of the series circuit formed by the switching elements 11 and 12, both ends of the series circuit are connected. By the alternating operation of 11 and 12, a pseudo sine wave current corresponding to the resonance frequency of the resonance circuit 3 flows in the primary winding 51 of the resonance circuit 3 and the transformer 5. At this time, an induced voltage is generated in the secondary winding 52 coupled to the primary winding 51. This induced voltage is converted into DC by the output rectifying / smoothing circuit 7 connected to the secondary winding 52 of the transformer 5, and is output.

The same circuit operation is performed in converter circuit B as well. That is, the switching elements 2 connected in series
By alternately operating 1 and 22, the input DC power source Vin is switched, and the switching output is supplied to the primary winding 51 of the resonance circuit 4 and the transformer 5.

A connection point between the switching elements 21 and 22, and
Since both ends of a series circuit in which the resonance circuit 4 and the primary winding 61 of the transformer 6 are connected in series are connected between one end of the series circuit constituted by the switching elements 21 and 22, both ends of the series circuit are connected. Due to the alternating operation of 21 and 22, a pseudo sine wave current corresponding to the resonance frequency of the resonance circuit 4 flows in the primary winding 61 of the resonance circuit 4 and the transformer 6. At this time, an induced voltage is generated in the secondary winding 62 coupled to the primary winding 61. This induced voltage is converted into direct current by the output rectifying / smoothing circuit 8 connected to the secondary winding 62 of the transformer 6, and the direct current output voltage Vo is supplied to a load (not shown).

Here, since the output terminals of the output rectifying / smoothing circuits 7 and 8 are commonly connected to the converter circuits A and B, the parallel operation system in which the outputs of the converter circuits A and B are commonly supplied to the loads. The resonance type switching power supply can be obtained.

In the parallel operation type resonance type switching power source as described above, the primary windings 51 and 52 of the transformers 5 and 6 respectively provided in the converter circuits A and B are connected in parallel with each other. In addition, the converter circuit A
In the resonance circuit 3 and the resonance circuit 4 of the converter circuit B, the capacitor 31 and the capacitor 41 are connected in parallel with each other, and the inductor 32 and the inductor 42 are connected in parallel with each other. Therefore, the switching element (1
1, 12), the resonance circuit 3, 4 viewed from the (21, 22) side
The capacitance value and the inductance value of are averaged. The exciting inductances of the primary windings 51 and 61 and the inductance values of the output choke coils 70 and 80 equivalently converted to the primary side are also averaged. That is, as shown in FIG. 2, it has a single resonance characteristic L0 of the resonance frequency f0. In FIG. 2, the horizontal axis represents frequency and the vertical axis represents impedance Z. A characteristic L1 is a characteristic of the resonance circuit 3 and has a resonance frequency f01. The characteristic L2 is the characteristic of the co-resonance circuit 4 and has the resonance frequency f02.

Therefore, when the converter circuits A and B are synchronously operated at the same frequency, generation of frequency beat noise and instability of control can be avoided. This means that by using one control circuit 9, the converter circuit A,
It means that B can be controlled. Therefore, it is possible to realize a parallel operation type resonant switching power supply that can be reduced in price and downsized.

Moreover, the switching elements (11, 1)
2), the impedances seen from the (21, 22) side are averaged in the converter circuits A and B,
The operation timings of the converter circuits A and B are matched. Therefore, in both the converter circuits A and B, the resonance current IR1 sufficient to achieve ZVS,
While IR2 is flowing, the switching element (11,
12) and (21, 22) can be turned off.

As a means for matching the resonance characteristics of the resonance circuits 3 and 4 included in the converter circuits A and B, a method of connecting all the resonance circuits 3 and 4 in parallel can be considered. However, the resonance circuits 3 and 4 included in the converter circuits A and B respectively have resonance frequencies f01 and f02 as shown in FIG. 2 due to the difference in the characteristics of the resonance capacitors 31 and 41 and the resonance inductors 32 and 42. It is common to have different resonance characteristics L1 and L2. When two resonance circuits 3 and 4 having such different resonance characteristics L1 and L2 are connected in parallel, the resonance circuit having a high impedance, for example, the resonance circuit 3 to the resonance circuit 4 having a low impedance.
A large resonance current (circulation current) flows to the. This circulating current may cause the resonance capacitors 31 and 41 and the resonance inductors 32 and 42 to generate heat abnormally, thus lowering the safety of the circuit. Further, the resonance inductors 32 and 42 may be magnetically saturated due to the flow of a large circulating current, losing their functions, and causing a circuit operation failure of the converter.

On the other hand, in the switching power supply according to the present invention, the switching elements (11, 12), (21,
22), the impedances of the converter circuits A and B are equal to each other and have a single resonance characteristic L0 as shown in FIG. 2, so that the resonance circuit 3 and the resonance circuit 4 have the same impedance. Circulating current due to impedance imbalance does not flow. Therefore, the above-mentioned trouble caused by the circulating current does not occur.

Further, since the resonance capacitors 31 and 41 and the resonance inductors 32 and 42 are individually provided for the converter circuits A and B, the converter circuits A and B have substantially the same symmetrical circuit configuration. . Therefore, it becomes easy to design the converter circuits A and B and to mount them on the circuit board.

FIG. 3 is a current waveform diagram of the switching power supply according to the present invention shown in FIG. In FIG. 3, IDS1
Is the waveform of the current flowing between the drain and source of the switching element 11, IR1 is the waveform of the resonant current flowing through the resonant circuit 3, IDS2 is the waveform of the current flowing between the drain and source of the switching element 21, and IR2 is flowing through the resonant circuit 4. It is a waveform of a resonance current.

In the case of the switching power supply according to the present invention shown in FIG. 1, the switching elements (11, 12), (21,
22) The impedance of the resonance circuits 3 and 4 seen from the side is
Since the converter circuits A and B are equal to each other, the operation timings of the converter circuits A and B coincide with each other as shown in FIG. Therefore, in both converter circuits A and B, resonance currents IR1 and I
With R2 flowing, switching elements (11, 1,
2) The ZVS can be performed by turning off (21, 22).

Further, the resonance capacitor 31 and the resonance inductor 32 that form the resonance circuit 3, and the resonance capacitor 41 and the resonance inductor 42 that form the resonance circuit 4.
Even if the circuit constant value of the converter circuit is different between the converter circuits A and B, the resonance capacitor 31 and the resonance capacitor 4
1 is connected in parallel, and the resonance inductor 32 and the resonance inductor 42 are connected in parallel, so that the impedances of the resonance circuits 3 and 4 match, so that the resonance capacitors 31 and 41 and the resonance inductor 32, It is not necessary to select 42, and it is possible to avoid a decrease in productivity and an imbalance in load sharing due to circuit elements.

There are various modes of connecting the resonance circuits 3 and 4. An example thereof will be described with reference to FIGS.
In the figure, the same components as those in FIG. 1 are designated by the same reference numerals, and the description thereof will be omitted.

First, in the embodiment of FIG. 4, the resonance inductors 32 and 42 are connected to the switching elements (11 and 12),
The resonance capacitors 31, 41 are connected between the connection point of (21, 22) and one ends of the primary windings 51, 61, and the resonance capacitors 31, 41 are connected between the sources of the switching elements 12, 22 and the other ends of the primary windings 51, 61. In the circuit configuration connected between, the resonance capacitor 31 and the resonance capacitor 41 are connected in parallel, and the resonance inductor 32 and the resonance inductor 42 are connected in parallel.

Next, in the embodiment of FIG. 5, the transformers 5 and 6 are
One end of each of the primary windings 51 and 61 of the switching element (1
1, 12), (21, 22), and one end of the resonance capacitors 31, 41 is connected to the switching element 12,
In the circuit configuration in which the resonance inductors 32 and 42 are connected between the other ends of the resonance capacitors 31 and 41 and the other ends of the primary windings 51 and 61, the resonance capacitor 31 and the resonance capacitor 31 are connected to each other. The capacitor 41 is connected in parallel, and the resonance inductor 32 and the resonance inductor 42 are connected in parallel.

In the embodiment shown in FIG. 6, the resonance capacitor 3 is used.
1, 41 to the switching elements (11, 12), (2
1, 22) and one end of the primary windings 51 and 61, and the resonance inductors 32 and 42 are connected to the sources of the switching elements 12 and 22 and the other ends of the primary windings 51 and 61. In the circuit configuration connected between, the resonance capacitor 31 and the resonance capacitor 41 are connected in parallel, and the resonance inductor 32 and the resonance inductor 42 are connected in parallel.

In any of the embodiments, it is possible to obtain the same effects as those of the embodiment shown in FIG.

As described above, in the present invention, converter circuits A and B are synchronously driven at the same frequency.
In the embodiment shown in FIGS. 1 to 6, this is realized by including one control circuit 9, whereby
As described above, the cost and size of the switching power supply can be reduced, the generation of frequency beat noise and the instability of control can be avoided, and further the generation of circulating current can be eliminated.

FIG. 7 is an electric circuit diagram showing another embodiment. In this embodiment, a control circuit 91 for the converter circuit A and a control circuit 92 for the converter circuit B are provided. The control circuits 91 and 92 monitor the operation of each other while switching elements (11, 12), (21,
22) are synchronously driven at the same frequency.

Although the contents of the present invention have been specifically described with reference to the embodiments, those skilled in the art can make various modifications based on the basic technical idea and teaching of the invention. Is self-evident.

[0066]

As described above, according to the present invention, the following effects can be obtained. (A) It is possible to provide a parallel operation type resonance type switching power supply that can be reduced in price and downsized. (B) It is possible to provide a resonance type switching power supply of a parallel operation system capable of avoiding generation of frequency beat noise and instability of control. (C) It is possible to provide a resonant switching power supply of a parallel operation system capable of ZVS. (D) It is not necessary to select the circuit elements that form the resonance circuit, and it is possible to provide a parallel operation type resonance type switching power supply that can avoid a decrease in productivity and an imbalance in load sharing due to the circuit elements. . (E) It is possible to provide a parallel operation type resonant switching power supply that is easy to design a converter circuit and mount on a circuit board. (F) It is possible to provide a resonant switching power supply that can balance impedances between resonance circuits, prevent a circulating current due to impedance imbalance from flowing, and avoid obstacles due to the circulating current.

[Brief description of drawings]

FIG. 1 is an electric circuit diagram of a parallel operation type resonant switching power supply according to the present invention.

FIG. 2 is a waveform diagram illustrating operating characteristics of a resonant switching power supply.

FIG. 3 is a current waveform diagram of the parallel operation type resonance type switching power supply according to the present invention shown in FIG.

FIG. 4 is an electric circuit diagram showing another embodiment of the parallel operation type resonance type switching power supply according to the present invention.

FIG. 5 is an electric circuit diagram showing still another embodiment of the parallel operation type resonance switching power source according to the present invention.

FIG. 6 is an electric circuit diagram showing still another embodiment of the parallel operation type resonance type switching power supply according to the present invention.

FIG. 7 is an electric circuit diagram showing still another embodiment of the parallel operation type resonance type switching power supply according to the present invention.

[Explanation of symbols]

11, 12 Switching element 21, 22 Switching element 3, 4 resonance circuit 31, 41 Resonance capacitors 32, 42 Resonance inductor 5, 6 transformers 51, 61 Primary winding 52, 62 Secondary winding 7, 8 output rectification smoothing circuit 9, 91, 92 control circuit

Claims (6)

(57) [Claims] 1. A switching power supply including a plurality of converter circuits, wherein each of the plurality of converter circuits includes two switching elements, a transformer, a resonance circuit, and an output rectifying and smoothing circuit, The two switching elements are connected in series, both ends of the series circuit are led to a DC power source, and are alternately driven, and the transformer includes at least a primary winding and a secondary winding, and The primary windings of the transformer provided in each of the converter circuits are connected in parallel with each other, the resonant circuit is connected in series with the primary winding of the transformer, the resonant circuit and the Both ends of the series circuit formed by the primary winding of the transformer are connected to the connection point of the two switching elements and the two switching elements. The resonance circuit includes a resonance capacitor and a resonance inductor, and the resonance capacitor is individually provided for each of the plurality of converter circuits. Is provided for each converter circuit individually
The resonance capacitors are connected in parallel to each other, and the resonance inductors are individually provided for each of the plurality of converter circuits and individually for each of the plurality of converter circuits.
The resonance inductor provided in is connected in parallel with each other, said output rectifying and smoothing circuit is connected to the transformer of the secondary winding is connected to the common output terminal in the plurality of converter circuits Switching power supply. 2. The switching power supply according to claim 1, wherein each of the resonance circuits provided in each of the plurality of converter circuits is connected to each other at a connection point of the two switching elements. Switching power supply. 3. The switching power supply according to claim 2, wherein in each of the resonance circuits provided in each of the plurality of converter circuits, one end of the resonance capacitor connects the two switching elements. Switching power supply connected to the point. 4. The switching power supply according to claim 3, wherein one end of the resonance inductor is connected to the other end of the resonance capacitor. 5. The switching power supply according to claim 1, 2, 3, or 4, wherein the plurality of converter circuits are synchronously driven at the same frequency. 6. The switching power supply according to claim 5, wherein the switching power supply includes one control circuit, and the control circuit is shared by the plurality of converter circuits.