JP2002233150A - Resonance-type dc-to-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonance-type DC-to-DC converter which performs reliable commutation for a specified time interval, when it is lightly loaded and a small current flows, and reduces switching loss and noise. SOLUTION: The resonance-type DC-to-DC converter in which a full-bridge inverter is connected to a primary side of a transformer 5 and a rectifying circuit for rectifying the output of the full-bridge inverter is connected to a load resistor 9, is provided with a first auxiliary resonance circuit and a second auxiliary resonance circuit. Charging and discharging currents of capacitors 4a-4d of the full-bridge inverter are made to have specified values, and IGBTs 10a, 10b of the auxiliary resonance circuits are made to perform a soft switching operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resonance type D having a full-bridge inverter connected to the primary side of a transformer and a rectifier circuit for outputting a required DC voltage to a load connected to the secondary side.
The present invention relates to a C-DC converter, and more particularly, to a resonant DC-DC converter capable of suppressing switching loss of a switching element and noise generated by switching.

[0002]

2. Description of the Related Art In recent years, power electronics have increased harmonics in power systems. In an industrial DC power supply device, research and development of a high power factor converter and a PWM converter are being performed to suppress this. Further, in order to suppress electromagnetic induction noise generated from the power supply device, the switching element is switched to zero voltage switching (hereinafter referred to as “ZV”).
S ". ) Or zero current switching (hereinafter "ZC
S ". Research has also been conducted on noise reduction using soft switching technology.

[0003] In the field of resonance type DC-DC converters as well, research into practical application for improving characteristics by applying soft switching technology has been conducted. By the soft switching, not only the noise but also the switching loss of the switching element can be significantly reduced, so that the efficiency of the converter can be improved.

FIG. 9 shows a circuit example of a conventional resonance type DC-DC converter to which such a soft switching technique is applied. This resonant DC-DC converter has a circuit configuration in which a full-bridge inverter is provided on the primary side of a transformer and a rectifier circuit for rectifying the output of the full-bridge inverter is provided on the secondary side of the transformer, to a load resistor.

The full-bridge inverter includes IGBTs 2a to 2d, which are switching elements receiving DC power supply 1, reverse conducting diodes 3a to 3d, and snubber capacitors 4a to 4d.
d, a transformer 5; 5a, a transformer primary winding; and 5b, a transformer secondary winding.

The rectifying circuit includes rectifying diodes 6a to 6a.
6d, reactor 7, capacitor 8, resonance IGBT1
0a to 10b, reverse conducting diodes 11a to 11 for resonance
b, consisting of a resonance reactor 12a, and applying a direct current to the load resistor 9.

Next, as a circuit operation of the resonance type DC-DC converter shown in FIG.
Regarding the commutation to T2b and 2c, the circuit state of each mode will be described with reference to FIGS. The detailed circuit operation is described in “An Improved Full-Bridge Zero-Volta
ge-Transition PWM DC / DC Converter with Zero-Voltag
e / Zero-Current Switching of the Auxiliary Switche
s ”: IEEE IAS Vol36, No.2, March / April 2000, pp558-566
And so on.

In FIG. 9, a switching element I
The GBT includes IGBTs 2a and 2d and IGBTs 2b and 2c.
And always switch in pairs. Of this pair, the arm with the IGBTs 2a and 2b that always switch first is the advance arm, and the arm with the IGBTs 2c and 2d that switch after the switching of the IGBTs 2a and 2b is the delay arm.

In FIGS. 10 to 13, the circuits indicated by solid lines are circuits in which a current path is formed, and the circuits indicated by thin lines are circuits in which no current path is formed.

In FIG. 10, when the IGBTs 2a and 2d are on, a DC power supply voltage is applied to the transformer 5. The voltage generated in the secondary winding 5b of the transformer is rectified by the rectifying diodes 6a and 6d of the secondary rectifier circuit, a current is supplied as a DC voltage to the load resistor 9, and the capacitor 8 is charged through the reactor 7. .

In FIG. 11, the IGBT on the advance arm side
Turn off 2a. IGBT2a is turned off at ZVS,
The snubber capacitor 4a is charged and the snubber capacitor 4b is discharged. The current flows through the reverse conducting diode 3b →
It flows from the transformer primary winding 5a to the IGBT 2d. At this time,
No voltage is applied to the transformer 5, and the secondary side rectifier circuit and the load resistor 9 are in the reflux mode. The DC voltage value of the capacitor 8 is controlled by adjusting the reflux mode period. By turning on the IGBT 2b during this period, the IGBT 2b is turned on by ZVS / ZCS.

In FIG. 12, the IGBT on the delay arm side
Turn off 2d. IGBT2d is turned off at ZVS,
The snubber capacitor 4d is charged and the snubber capacitor 4c is discharged. The snubber capacitor 4c discharges,
When the voltage of snubber capacitor 4d becomes higher than the DC power supply voltage, reverse conducting diode 3c conducts. The current is from the negative side of the DC power supply 1 → the reverse conducting diode 3b → the transformer 5
→ reverse conduction diode 3c → flows on the positive side of DC power supply 1.
During this time, by turning on the IGBT 2c, ZVS / ZC
S turns on. Thereby, the commutation is completed.

In FIG. 13, when the current is small in FIG. 12, the resonance IGBT 10a is turned off before the IGBT 2d is turned off.
Turn on. DC power supply 1 positive side → IGBT 10a for resonance →
A resonance current flows through the resonance reactor 12a → the IGBT 2d → the negative side of the DC power supply 1. When the resonance current exceeds a certain value, the IGBT 2d is turned off. IGBT2d is ZV
It turns off at S, and the snubber capacitor 4d is charged and the snubber capacitor 4c is discharged. The charging / discharging time of the snubber capacitor 4c is fixed by the resonance current.

Here, a case where the load current is small, such as when the load is light, will be described. In such a case, the current further decreases particularly on the delay arm side, so that the charging and discharging of the snubber capacitor becomes longer. Therefore, the IGBT may fail in soft switching. To avoid this, a method of delaying the ON time of the IGBT may be considered, but controllability is greatly reduced.

By using the above-described auxiliary resonance circuit as a solution to this, commutation can be reliably performed in a certain time.

However, the conventional resonant DC-D shown in FIG.
In the C converter, the resonance IGBT 10 of the auxiliary resonance circuit is used.
In a and 10b, since the switching element performs hard switching, there is a problem of an increase in switching loss and noise due to the resonant IGBT.

[0017]

SUMMARY OF THE INVENTION It is an object of the present invention to ensure that commutation can be performed for a certain period of time by an auxiliary resonance circuit even at a light load and a low current, and that a switch element constituting the auxiliary resonance circuit is soft. An object of the present invention is to provide a resonance type DC-DC converter capable of switching to reduce switching loss and noise caused by a switching element of an auxiliary resonance circuit.

[0018]

According to a first aspect of the present invention, there is provided a resonance type DC-DC converter comprising: a full-bridge inverter having a DC power supply as an input; a transformer having an output of the full-bridge inverter as an input; A rectifier circuit for converting the output of the DC power supply to a DC power and outputting a DC power to a load; a first resonance switch element and a first resonance inductance connected in series from a neutral point of the DC power supply; A first resonance diode and a first resonance inductance between the neutral point and the output side of the full-bridge inverter, the direction of conduction being between the neutral point and the output side of the full-bridge inverter. A second resonance diode is connected between the output side of the inverter and the conduction direction from the neutral point to the output side of the full-bridge inverter. First auxiliary resonant circuit that is, the second resonance switch element from the neutral point of the DC power supply and a second
Are connected in series, and the third resonance inductance is connected between the second resonance inductance and the output side of the full-bridge inverter from the output side of the full-bridge inverter so that the neutral point direction becomes the conduction direction. A fourth resonance diode in which the neutral point direction is a conduction direction from the output side of the full bridge inverter is connected between the diode and the second resonance inductance and the output side of the full bridge inverter. 2 is a resonance type DC-DC converter, comprising: two auxiliary resonance circuits.

The resonance type DC-D according to the first aspect of the present invention.
In the case of the C converter, the charge and discharge current of the capacitor connected in parallel to the switch element of the full-bridge inverter can be made constant by the auxiliary resonance circuit even at a low current at a light load, so As a result, commutation of the switch element of the full-bridge inverter can be achieved, and controllability is dramatically improved. Further, since the switching element of the auxiliary resonance circuit performs soft switching, switching loss and noise due to switching of the switching element of the auxiliary resonance circuit can be reduced. Since the auxiliary resonance circuit is operated only when the load current is equal to or less than a fixed value and the commutation of the switch element of the full-bridge inverter, the loss due to the auxiliary resonance circuit can be reduced.

According to a second aspect of the present invention, there is provided a resonant DC-DC converter comprising: a full-bridge inverter having a DC power supply as an input; a transformer having an output of the full-bridge inverter as an input; A rectifier circuit that converts and outputs DC to a load, a resonance bidirectional switch element and a resonance inductance are connected in series from a neutral point of the DC power supply, and the resonance inductance is connected to the output side of the full-bridge inverter. A resonance type DC-DC converter comprising an auxiliary resonance circuit connected and configured.

The resonance type DC-D according to the second aspect of the present invention.
In the C converter, even at a low current at a light load, the charge / discharge current of the capacitor connected in parallel to the switch element on the side of the lag phase arm in the full-bridge inverter is made constant by the auxiliary resonance circuit. Therefore, the commutation of the switch element of the full-bridge inverter on the side of the delay phase arm can be always performed for a fixed time, and controllability is dramatically improved. Further, since the switching element of the auxiliary resonance circuit performs soft switching, switching loss and noise due to switching of the switching element can be reduced. Since the auxiliary resonance circuit operates only when the load current is equal to or less than the fixed value and the main circuit switch element is commutated, the loss due to the auxiliary resonance circuit can also be reduced. Further, since the auxiliary resonance circuit is constituted only by a pair of bidirectional resonance circuits with respect to the lag phase arm, there is an advantage that the number of parts and the size of the auxiliary resonance circuit can be substantially equal to those of the conventional circuit example.

According to a third aspect of the present invention, there is provided a resonant DC-DC converter comprising: a full-bridge inverter having a DC power supply as an input; a transformer having an output of the full-bridge inverter as an input; A rectifier circuit for converting and outputting a direct current to a load; a first bidirectional switch element for resonance and a first inductance for resonance connected in series from a neutral point of the DC power supply; A first auxiliary resonance circuit configured by connecting the resonance inductance to a second bidirectional switch element for resonance and a second resonance inductance in series from a neutral point of the DC power supply; A resonance type DC-DC converter comprising: a second auxiliary resonance circuit configured by connecting the resonance inductance to an output side of the full bridge inverter. Bata is.

A resonance type DC-D according to a third aspect of the present invention.
In the C converter, even at a low current at a light load, the charge / discharge current of the capacitor connected in parallel to the switch element of the full-bridge inverter can be made constant by the auxiliary resonance circuit. The commutation of the switch element of the full-bridge inverter can be performed for a fixed time, and controllability is dramatically improved. Further, since the switching element of the auxiliary resonance circuit performs soft switching, switching loss and noise due to switching of the switching element can be reduced. Since the auxiliary resonance circuit is operated only when the load current is equal to or less than a certain value and the commutation of the switch element of the full-bridge inverter, the loss due to the auxiliary resonance circuit can be reduced.

[0024]

FIG. 1 is a circuit diagram of a resonance type DC-DC converter according to a first embodiment of the present invention.

In FIG. 1, the resonance type DC-
The DC converter has a full-bridge inverter to which the DC power supply 1 is input.

This full-bridge inverter includes an IGBT 2a, which is a main circuit switching element having one terminal connected to the positive terminal of the DC power source 1, and an IGBT 2b having one terminal connected to the negative terminal, at a first connection point, at the other end of each switch. A first inverter arm having terminals connected to each other, and an IGBT 2c having one terminal connected to the positive terminal of the DC power supply 1 and an IGBT 2d having one terminal connected to the negative terminal of the DC power supply 1 are connected at a second connection point to the other terminal of each switch. A second inverter connected to the IGBTs 2a to 2d, reverse conducting diodes 3a to 3d respectively connected in antiparallel to the IGBTs 2a to 2d, and an IGBT 2
snubber capacitors 4a respectively connected in parallel to a to 2d
To 4d.

A transformer 5 connected between the first connection point and the second connection point on the output side of the full-bridge inverter, an output of the transformer 5 being an input, and a DC It has rectifier diodes 6 a to 6 d, a reactor 7, and a capacitor 8 that constitute a rectifier circuit that provides an output.

Further, an IGBT 10a, which is a switching element for resonance, and a reactor 12a for resonance are connected in series from a neutral point of the DC power supply 1, and a first connection point from the neutral point is provided between the resonance reactor 12a and the first connection point. The resonance diode 13a and the resonance diode 13c whose conduction direction is connected from the neutral point to the second connection point are connected between the resonance diode 13a and the resonance reactor 12a whose conduction direction is the conduction direction. The configured first auxiliary resonance circuit, the IGBT 10b for resonance and the reactor 12
b are connected in series, and between the resonance reactor 12b and the first connection point, the resonance diode 13b and the resonance reactor 12 whose conduction direction is the neutral point direction from the first connection point.
and a second auxiliary resonance circuit formed by connecting a resonance diode 13d having a neutral direction from the second connection point to the conduction direction between the second connection point and the second connection point.

Note that 11a and 11b are IGBTs 1 for resonance.
These are reverse conducting diodes for resonance provided in 0a and 10b, and 14a and 14b are DC voltage dividing capacitors.

Next, as the circuit operation of the resonance type DC-DC converter of this embodiment, the IGBTs 2a and 2d
Regarding the commutation to the BTs 2b and 2c, the circuit state of each mode will be described with reference to FIGS.

In FIG. 2 to FIG. 6, the circuits indicated by solid lines are circuits in which a current path is formed, and the circuits indicated by thin lines are circuits in which no current path is formed.

If the current is equal to or more than a predetermined value, the auxiliary resonance circuit is not operated, and the operation is the same as that of the conventional example shown in FIG. Therefore, the case where the current is equal to or less than the fixed value will be described below. The detailed operation of the auxiliary resonance circuit is described in JP-A-8-340676.

In FIG. 2, when the IGBTs 2a and 2d are on, a DC power supply voltage is applied to the transformer 5. The voltage generated in the secondary winding 5b of the transformer is rectified by the rectifier diodes 6a and 6d of the secondary rectifier, a current is supplied to the load resistor 9 as a DC voltage, and the capacitor 8 is charged through the reactor 7.

In FIG. 3, the IGBT 2 on the advance arm side
When a is turned off, the current is equal to or less than a fixed value (Iboost).
Turn on. DC voltage dividing capacitor 14a positive side → IG
A resonance current flows through a path on the BT2a → the resonance diode 13a → the resonance reactor 12a → the resonance IGBT 10a → the DC voltage dividing capacitor 14a. IGBT2a
, A current of a load current + a resonance current flows.

In FIG. 4, the current of IGBT 2a is Ib
When it reaches oost, the IGBT 2a is turned off. IGB
T2a is turned off by ZVS, and the snubber capacitor 4a is charged and the snubber capacitor 4b is discharged. The current flows through the reverse conducting diode 3b → the transformer 5 → the IGBT 2d
Flows in At this time, no voltage is applied to the transformer 5, and the secondary side rectifier circuit and the load resistor 9 are in the reflux mode. The DC voltage value of the capacitor 8 is controlled by adjusting the reflux mode period. Also, during this period IGB
Turning on T2b turns on ZVS / ZCS.
Since the resonance current flows on the negative side of the DC voltage dividing capacitor 14b → the reverse conducting diode 3b → the diode for resonance 13a → the reactor for resonance 12a → the IGBT 10a for resonance → the positive side of the DC voltage dividing capacitor 14b, it rapidly attenuates.

When the resonance current becomes 0, the resonance diode 13a turns off and the resonance circuit turns off. By turning off the resonance IGBT 10a after the resonance circuit is turned off, the IGBT 10a is turned off by the ZCS.

In FIG. 5, the IGBT 2 on the delay arm side
When d is turned off, the resonance IGBT 10b is turned on immediately before the turn-off because the current is equal to or less than Iboost. DC voltage dividing capacitor 14b positive side → IGBT 10b for resonance
→ Resonant reactor 12b → Resonant diode 13d →
Resonant current flows through a path on the negative side of IGBT 2d → DC voltage dividing capacitor 14b. The current of the load current + the resonance current flows through the IGBT 2d.

In FIG. 6, the current of IGBT 2d is Ib
When it reaches oost, the IGBT 2d is turned off. IGB
T2d is turned off by ZVS, and the snubber capacitor 4d is charged and the snubber capacitor 4c is discharged. The current flows from the negative side of the DC power supply 1 → the reverse conducting diode 3b → the transformer 5 → the reverse conducting diode 3c → the positive side of the DC power supply 1.
At this time, a voltage is applied to the transformer 5 in a direction opposite to that in the mode shown in FIG. By turning on the IGBT 2b during this period, the IGBT 2b is turned on by ZVS / ZCS. Thereby, the commutation is completed. Since the resonance current flows on the negative side of the DC voltage dividing capacitor 14a, the IGBT 10b for resonance, the reactor 12b for resonance, the diode 13d for resonance, the reverse conducting diode 3c, and the positive side of the DC voltage dividing capacitor 14a, it attenuates rapidly. When the resonance current becomes 0, the resonance diode 13d turns off and the resonance circuit turns off. By turning off the resonance IGBT 10b after the resonance circuit is turned off, the IGBT 10a is turned off by the ZCS.

According to the first embodiment described in detail above,
Even at a low current at a light load, the IGBT 2 which is a switch element of the full-bridge inverter is provided by the auxiliary resonance circuit.
Since the charging and discharging currents of the capacitors 4a to 4c connected in parallel to the a to 2d can be made constant, the commutation of the IGBTs 2a to 2d of the full-bridge inverter can be achieved in a constant time, and the controllability is dramatically improved. To improve. IGBTs 10a to 10b, which are switch elements of the auxiliary resonance circuit,
Is soft switching, so that the IGBT 10a
The switching loss and noise due to the switching of 10 to 10b can be reduced. Since the auxiliary resonance circuit is operated only when the load current is equal to or less than a fixed value and the IGBTs 2a to 2d of the full-bridge inverter are commutated, the loss due to the auxiliary resonance circuit can be reduced. Further, since the auxiliary resonance circuit is composed of only one pair of bidirectional resonance circuits for two arms in the full-bridge inverter as the main circuit, the number of parts and the size of the auxiliary resonance circuit are almost the same as those of the conventional circuit example. There is an advantage that can be done.

FIG. 7 is a circuit diagram of a resonance type DC-DC converter according to a second embodiment of the present invention. 2a-2d
Is an IGBT receiving the DC power supply 1, 3a to 3d are reverse conducting diodes, 4a to 4d are snubber capacitors, 5 is a transformer, 6a to 6d are rectifier diodes, 7 is a reactor, 8
Is a capacitor connected in parallel with the load resistor 9, 9 is a load resistor, 10a to 10b are IGBTs for resonance, 11a to 11b
A reverse conducting diode for resonance, 12a is a reactor for resonance,
14a to 14b are DC voltage dividing capacitors.

In the second embodiment, even at a low current under a light load, the auxiliary resonance circuit causes
Capacitor 4a connected in parallel to GBTs 2a to 2d
Since the charging / discharging current of ~ 4d can be set to a constant value, the IGBT which is a switching element on the lag phase arm side
Commutation for a certain period of time, and controllability is dramatically improved.
The IGBT 10 which is a switch element of the auxiliary resonance circuit
Since a and 10b are soft switching, IGBT
Switching loss and noise due to switching of 10a and 10b can be reduced. Since the auxiliary resonance circuit is operated only when the load current is equal to or less than a fixed value and the IGBTs 2a to 2d are commutated, the loss due to the auxiliary resonance circuit can also be reduced. Further, since the auxiliary resonance circuit is constituted by only one pair of bidirectional resonance circuits with respect to the delay phase arm of the full-bridge inverter as the main circuit, the number of parts and the size of the auxiliary resonance circuit are the same as those of the conventional circuit example. There is an advantage that only a degree is needed.

FIG. 8 is a circuit diagram of a resonance type DC-DC converter according to a third embodiment of the present invention. 2a-2d
Is an IGBT receiving the DC power supply 1, 3a to 3d are reverse conducting diodes, 4a to 4d are snubber capacitors, 5 is a transformer, 6a to 6d are rectifier diodes, 7 is a reactor, 8
Are capacitors connected in parallel to the load resistor 9;
0d is an IGBT for resonance, 11a to 11d reverse conducting diodes for resonance, 12a to 12b are reactors for resonance, 14a
14b are DC voltage dividing capacitors.

In the third embodiment, even at a low current at a light load, the auxiliary resonance circuit allows the IGBTs 2a to 2g to be the switching elements of the full-bridge inverter as the main circuit.
Since the charging and discharging currents of the capacitors 4a to 4d connected in parallel to the 2d can be made constant, the commutation of the IGBTs 2a to 2d of the full-bridge inverter can always be made for a fixed time, and controllability is dramatically improved. . In addition, the IGBTs 10a to 10d, which are switch elements of the auxiliary resonance circuit, perform soft switching, so that the IGBTs 10a to 10d
The switching loss and noise due to the switching can be reduced. Since the auxiliary resonance circuit is operated only when the load current is equal to or less than a fixed value and the IGBTs 2a to 2d of the full-bridge inverter are commutated, the loss due to the auxiliary resonance circuit can be reduced.

[0044]

As described above, according to the present invention, the charging / discharging current of the capacitor connected in parallel to the switch element of the full-bridge inverter is kept constant by the auxiliary resonance circuit even at a low current at a light load. Because you can
The commutation of the main circuit switch element can always be achieved in a certain time,
Controllability is dramatically improved. Further, since the switching element of the auxiliary resonance circuit performs soft switching, switching loss and noise due to switching of the switching element can be reduced. Since the auxiliary resonance circuit is operated only when the load current is equal to or less than a certain value and the commutation of the switch element of the full-bridge inverter, the loss due to the auxiliary resonance circuit can be reduced.

Therefore, according to the present invention, commutation can be reliably performed for a certain period of time by the auxiliary resonance circuit even when the load is low and the current is low. An object of the present invention is to provide a resonance type DC-DC converter capable of reducing switching loss and noise due to a switching element of a resonance circuit.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a circuit operation according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a circuit operation according to the first embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a circuit operation according to the first embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a circuit operation according to the first embodiment of the present invention.

FIG. 6 is an explanatory diagram showing a circuit operation according to the first embodiment of the present invention.

FIG. 7 is a circuit configuration diagram showing a second embodiment of the present invention.

FIG. 8 is a circuit configuration diagram showing a third embodiment of the present invention.

FIG. 9 is a circuit diagram showing a conventional resonance type DC-DC converter.

FIG. 10 is an explanatory diagram showing a circuit operation of a conventional resonance type DC-DC converter.

FIG. 11 is an explanatory diagram showing a circuit operation of a conventional resonance DC-DC converter.

FIG. 12 is an explanatory diagram showing a circuit operation of a conventional resonance type DC-DC converter.

FIG. 13 is an explanatory diagram showing a circuit operation of a conventional resonance DC-DC converter.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC power supply, 2a-2d ... IGBT, 3a-3d ... Reverse conducting diode, 4a-4d ... Snubber capacitor, 5 ...
Transformer, 5a: Transformer primary winding, 5b: Transformer secondary winding, 6a to 6d: Rectifier diode, 7: Reactor, 8
... Capacitor, 9 ... Resistance, 10a-10d ... Resonance IG
BT, 11a to 11d: reverse conducting diode for resonance, 12
a to 12d: resonance reactors, 13a to 13a: resonance diodes, 14a to 14b: DC voltage dividing capacitors.

Claims (3)

[Claims] 1. A full-bridge inverter having a DC power supply as an input, a transformer having an input of the full-bridge inverter as an input, and a rectifier circuit for converting an output of the transformer into a DC and outputting a DC to a load. A first resonance switch element and a first resonance inductance are connected in series from a neutral point of the DC power supply;
A first resonance diode and a first resonance inductance between the neutral point and the output side of the full-bridge inverter, the direction of conduction being between the neutral point and the output side of the full-bridge inverter. A first auxiliary resonance circuit formed by connecting a second resonance diode having a conduction direction from the neutral point to the output side of the full-bridge inverter between the output sides of the inverter; From the point, the second resonance switch element and the second resonance inductance are connected in series, and the second resonance switch element and the second resonance inductance are connected in series.
A third resonance diode and a second resonance inductance between the resonance inductance of the full-bridge inverter and the output side of the full-bridge inverter from the output side of the full-bridge inverter to the neutral point direction. A second auxiliary resonance circuit formed between the output side of the bridge inverter and a fourth resonance diode having the neutral point in the conduction direction connected from the output side of the full bridge inverter. Resonant DC-DC
converter. 2. A full-bridge inverter having a DC power supply as an input, a transformer having an output of the full-bridge inverter as an input, and a rectifier circuit for converting an output of the transformer into a DC and outputting a DC to a load. An auxiliary resonance circuit configured by connecting a resonance bidirectional switch element and a resonance inductance in series from a neutral point of the DC power supply, and connecting the resonance inductance to an output side of the full-bridge inverter. A resonance type DC-DC converter characterized in that: 3. A full-bridge inverter having a DC power supply as an input, a transformer having an output of the full-bridge inverter as an input, and a rectifier circuit for converting an output of the transformer into a DC and outputting a DC to a load. A first resonance bidirectional switch element and a first resonance inductance are connected in series from a neutral point of the DC power supply, and the resonance inductance is connected to an output side of the full-bridge inverter. A first auxiliary resonance circuit, a second resonance bidirectional switch element and a second resonance inductance connected in series from a neutral point of the DC power supply, and the resonance inductance is connected to an output side of the full-bridge inverter. And a second auxiliary resonance circuit configured by connecting the DC-DC converter to a DC-DC converter.