JP2014171310A - Resonant dc/dc converter and resonant dc/dc converter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a resonant DC/DC converter capable of improving output controllability and efficiency while suppressing increase in the number of components.SOLUTION: Primary side coils of a resonant DC/DC converter 20 comprise a first coil L1 and a second coil L1 arranged on a transformer 22. A first auxiliary coil L4 is connected to the first coil L1 in series, and a second auxiliary coil L5 is connected to the second coil L2 in series. A magnetic flux formed by the first coil at a secondary side coil and a magnetic flux formed by the second coil at the secondary side coil are configured to be reverse phases with each other. The first auxiliary coil L4 and the second auxiliary coil L5 are magnetically in-phase coupled. A phase difference of signals supplied to switch elements T1 and T2 is changed between 0 degree to 180 degrees so as to control output.

Description

  The present invention relates to a resonant DC / DC converter.

  A DC / DC converter that converts a DC voltage is used in an electric vehicle such as a hybrid vehicle or an electric vehicle, an industrial robot, a machine tool, and a power machine using an electric motor such as an elevator. The DC / DC converter boosts or steps down a DC voltage from a power supply source to a desired voltage, and drives an electric vehicle or a power machine.

  As the DC / DC converter, there is a resonance type converter using electromagnetic induction and resonance. Patent Document 1 describes a one-stone current resonance type DC / DC converter. The current flowing from the DC input power source to the resonance inductance is switched by the semiconductor switch element, and the resonance circuit composed of the resonance inductance and the resonance capacitor is resonated. A voltage based on the resonance and electromagnetic induction appears on the resonance inductance and the output voltage of the DC input power supply is applied to the primary side of the high-frequency transformer, and a load voltage is output from the secondary side of the high-frequency transformer. .

  Patent Document 2 describes a resonance type LLC converter. FIG. 18 shows a circuit configuration of the LLC converter disclosed in Patent Document 2.

Japanese Patent Laid-Open No. 5-260745 US Pat. No. 6,344,795

  In general, a resonance type DC / DC converter tends to have a complicated and expensive circuit configuration, and thus it is required to improve output controllability while suppressing an increase in the number of components as much as possible.

  In the conventional DC / DC converter shown in FIG. 18, the basic drive method is a half-bridge method, two switch elements and drivers are required, and the driver potential of the upper element varies with the drive frequency. A power supply insulated from the main circuit is required, and the circuit becomes complicated and expensive. In addition, since two switch elements are connected in series, there is a problem that it is difficult to increase the frequency because high-precision timing adjustment is necessary to avoid a short-circuit state due to simultaneous turn-on of these switch elements.

  An object of the present invention is to provide a resonant DC / DC converter that can improve output controllability and achieve high efficiency while suppressing an increase in the number of components.

  The present invention provides a transformer including a primary side coil connected to a DC power source and a secondary side coil connected to an output load, a switch element connected to the primary side coil, and a parallel connection to the switch element. And a rectifier circuit connected to the secondary coil, wherein the primary coil includes a first coil and a second coil connected in parallel to the DC power source. A two-phase coil comprising a coil, both provided in a single transformer, a first auxiliary coil connected in series to the first coil, and a second auxiliary coil connected in series to the second coil, The switch element includes a first switch element connected in series to the first coil and a second switch element connected in series to the second coil, and the capacitor includes the first switch element A first capacitor connected in parallel; a second capacitor connected in parallel to the second switch element; the magnetic flux formed by the first coil on the secondary coil; and the second coil connected to the secondary side The first auxiliary coil and the second auxiliary coil are magnetically forward-coupled so that magnetic fluxes formed in the coils are connected in opposite phases.

  In the present invention, the primary coil is a two-phase coil, and the first coil, the first auxiliary coil, the first switch element, and the first capacitor constitute one phase (resonance circuit), and the second coil and the second auxiliary coil. The coil, the second switch element, and the second capacitor constitute another phase (resonance circuit). Since the two phases are connected in parallel to each other, it is not necessary to avoid a short-circuit state due to simultaneous ON as in the case where two switch elements are connected in series as in the prior art. In addition, since the first coil and the second coil are connected so that the magnetic flux formed in the secondary coil and the magnetic flux formed in the secondary coil are in opposite phases, the specific harmonic component is canceled and electromagnetic Noise is reduced. Furthermore, in this invention, since the 1st coil and 2nd coil which comprise two phases are both provided in the single transformer, the increase in a number of parts is suppressed. The output of the DC / DC converter can be controlled by changing the phase difference between the two phases. However, when the phase difference is small, the first coil and the second coil on the primary side of the transformer are inversely coupled, so that the inductance Although the value decreases equivalently, the first auxiliary coil connected in series to the first coil and the second auxiliary coil connected in series to the second coil are magnetically forward-coupled, so the inductance value is equivalent. As a result, even if the phase difference is changed, fluctuations in the inductance value of the transformer primary coil and auxiliary coil are suppressed, and high efficiency can be maintained.

  In one embodiment of the present invention, the phase difference between the current generated by turning on and off the first switch element and the current generated by turning on and off the second switch element is changed within a range of 0 degrees to 180 degrees. Phase difference control means is provided.

  Another embodiment of the present invention is characterized by comprising capacitance control means for changing the capacitance of at least one of the first capacitor and the second capacitor in accordance with a change in the phase difference.

  The present invention also provides a transformer having a primary side coil connected to a DC power source and a secondary side coil connected to an output load, an auxiliary coil connected in series to the primary side coil, and the primary Two or more resonant DC / DC converters including a switch element connected in series to the side coil, a capacitor connected in parallel to the switch element, and a rectifier circuit connected to the secondary coil, are connected in parallel. It is characterized in that output control is performed by switching the operation state and the stop state of each resonance type DC / DC converter by switching each switch element of each resonance type DC / DC converter between a drive state and a stop state.

  In one embodiment of the present invention, the two or more resonant DC / DC converters are divided into a first group and a second group, and are applied to each switch element of the resonant DC / DC converter belonging to the first group. The phase difference between the drive signal applied and the drive signal applied to each switch element of the resonance type DC / DC converter belonging to the second group is 180 degrees.

  In another embodiment of the present invention, the number of resonant DC / DC converters belonging to the first group and the number of resonant DC / DC converters belonging to the second group are the same.

  In still another embodiment of the present invention, the primary side coil and the auxiliary coil of each resonance type DC / DC converter are formed on the same printed circuit board.

  According to the present invention, it is possible to improve output controllability and maintain high efficiency while suppressing an increase in the number of parts.

It is a circuit block diagram of a 1 stone resonance type DC / DC converter. It is operation | movement explanatory drawing of the circuit of FIG. It is operation | movement explanatory drawing of the circuit of FIG. It is operation | movement explanatory drawing of the circuit of FIG. It is a circuit block diagram of the resonance type DC / DC converter in embodiment. It is a transformer block diagram of an embodiment. It is a circuit block diagram of the resonance type DC / DC converter in embodiment. It is a current voltage waveform figure (phase difference 180 degrees) which shows the simulation result of an embodiment. It is a current voltage waveform figure (phase difference 90 degrees) which shows the simulation result of an embodiment. It is a current-voltage waveform diagram (phase difference 60 degrees) showing the simulation result of the embodiment. It is a current-voltage waveform diagram (phase difference of 30 degrees) showing the simulation result of the embodiment. It is a graph which shows the relationship between a phase difference, output electric power, and an output voltage. It is a graph which shows the relationship between a phase difference, the largest element voltage, and the largest element current. It is a schematic diagram of a resonance type DC / DC converter. It is a block diagram of other embodiment provided with the some resonance type DC / DC converter. It is a block diagram of other embodiment. It is a block diagram of other embodiment. It is a circuit block diagram of the conventional apparatus.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

<Structure of pre-requisite single-stone resonant DC / DC converter>
First, a one-stone resonance type DC / DC converter which is a premise of the present embodiment will be described. The resonance type DC / DC converter of this embodiment can be positioned as an extension or improvement of such a one-stone resonance type DC / DC converter.

  FIG. 1 shows a circuit configuration diagram of a one-stone resonance type DC / DC converter 10. The transformer includes a primary coil L1 and a secondary coil L3.

  Regarding the primary side of the transformer, one end of the primary side coil L1 is connected to the positive side of the DC power source Vin via the auxiliary resonance coil L2. The other end of the primary coil L1 is connected to one end of the switch element T1. A diode is connected in reverse parallel to the switch element T1, and a resonance capacitor C1 is connected in parallel to the switch element T1. The other end of the primary coil L1 is connected to one end of the switch element T1 and is also connected to one end of the capacitor C1. The other end of the switch element T1 and the other end of the capacitor C1 are both connected to the negative electrode side of the DC power supply Vin. The switch element T1 is a switching transistor, for example, and is controlled by applying a control signal to the gate terminal.

  Regarding the secondary side of the transformer, the secondary coil L3 is connected to a capacitor C3 via a rectifier circuit, and the capacitor C3 is connected to a load RL via a filter coil L6.

FIG. 2 shows an equivalent circuit on the primary side of the circuit shown in FIG. In this circuit, the switch element T1 is replaced with a switch SW, the primary coil of the transformer is replaced with Lr, and the capacitor C1 is replaced with Cr. FIG. 3 shows waveforms of current and voltage at each part. In the figure, the current flowing through the switch SW is denoted by I _SWITCH , the voltage of the switch SW is denoted by V _SWITCH , the current flowing through the diode D1 is denoted by I _DIODE , and the current flowing through the primary coil Lr is denoted by I. When the switch SW is switched from on to off, the Cr potential is zero potential, and the current I flowing through Lr at this time is Ion. It is the state a in FIG. When the switch SW is turned off in this state, the resonance operation starts with Lr and Cr, and the Cr potential, that is, the potential V _{SWITCH of the} switch SW rises. When it is applied, the Lr current I starts to decrease, and when it becomes a negative current, the Cr potential begins to decrease and finally becomes zero. The Lr current at this time is Ico. Thereafter, since the negative current of Lr flows through the diode D1, the potential of Cr remains zero. When the switch SW is turned on, the Lr current increases again, and when the switch SW is turned off when it becomes Ion again, the above operation is repeated.

  Accordingly, in the circuit of FIG. 1, resonance occurs when the gate terminal of the switch element T1 is driven at the same frequency and duty ratio as the above-described resonance occurs, and functions as a DC / DC converter.

  FIG. 4 shows simulation operation waveforms when driven at about 40 kHz. The horizontal axis is time, and the vertical axis is voltage value and current value. In the figure, for convenience of explanation, the current flowing through the primary coil L1 is shifted downward by subtracting a predetermined value.

  When the switch element T1 is turned on, the current flows through the diode D1 because the current is a negative current (minus), and the switch is turned on in a state where the voltage is zero. Therefore, ZVS (Zero Voltage Switching) / ZCS (Zero Current Switching) Turn on. Further, when the switch element T1 is turned off, current is flowing but the voltage is turned off in a zero state. Therefore, ZVS (Zero Voltage Switching) is turned off, both of which are soft switching, and no switching loss is generated in principle. . Therefore, in this circuit system, high frequency switching is possible.

  The AC power generated by the primary coil L1 is converted to DC by the secondary rectifier circuit and consumed by the load RL. Therefore, the inductance of the primary side coil L1 is equivalently reduced by the value of the load RL, and the resonance period is reduced. When the primary side voltage is 400 V, a maximum current of 220 A flows through the switch element T1. In this case, the conversion power is about 8 KW.

<Configuration of 2-parallel resonant DC / DC converter>
Next, the resonance type DC / DC converter in this embodiment will be described.

  FIG. 5 shows a circuit configuration diagram of the resonant DC / DC converter 20 in the present embodiment. The transformer 22 includes a primary coil and a secondary coil, and the primary coil includes a first coil L1 and a second coil L2.

  One end of the primary side first coil L1 is connected to the positive electrode side of the DC power supply Vin via the auxiliary resonance coil L4. The other end of the first coil L1 is connected to the switch element D1. A diode D1 is connected in antiparallel to the switch element T1, and a resonance capacitor C1 is connected to the first coil L1 in parallel with the switch element T1. The other end of the switch element T1 and the other end of the capacitor C1 are both connected to the negative electrode side of the DC power supply Vin.

  The primary side second coil L2 is connected to the positive side of the DC power source Vin via the auxiliary resonance coil L5, and the first coil L1 and the second coil L2 are connected to the DC power source Vin in parallel with each other. The The other end of the second coil L2 is connected to the switch element T2. A diode D2 is connected in antiparallel to the switch element T2, and a resonance capacitor C2 is connected to the second coil L2 in parallel with the switch element T2. The other end of the switch element T2 and the other end of the capacitor C2 are both connected to the negative electrode side of the DC power supply Vin.

  The secondary side coil L3 includes a portion magnetically coupled to the primary side first coil L1 and a portion magnetically coupled to the primary side second coil L2. Although the secondary side coil L3 is divided into two in the figure, it is not always necessary to be composed of two physical parts, and may be physically composed of a single coil. The first coil L1 on the primary side and the coil L3 on the secondary side are coupled in phase. Further, the second coil L2 on the primary side and the coil L3 on the secondary side are coupled in reverse phase. That is, the magnetic flux formed by the first coil L1 on the secondary coil L3 and the magnetic flux formed by the second coil L2 on the secondary coil L3 are configured to be in opposite phases.

  The portion of the secondary coil L3 described above the first coil L1 is connected to the load RL via a rectifier circuit, a filter inductance L6, and a smoothing capacitor C3. Similarly, the portion of the secondary coil L3 described above the second coil L2 is also connected to the load RL via the rectifier circuit, the filter inductance L6, and the smoothing capacitor C3.

  As described above, the resonant DC / DC converter 20 shown in FIG. 5 has a configuration in which two primary-side circuits are connected in parallel to the DC power source Vin in the resonant DC / DC converter 10 shown in FIG. Yes. In these two parallel primary circuits, the first coil L1 and the second coil L2 together constitute a primary coil of a single transformer 22, and the secondary coil L3 is also the same and a single transformer. 22 secondary coils are configured and integrated to reduce the number of parts.

  In the circuit of FIG. 5, two primary-side circuits of the transformer 22 are connected in parallel, and the two-phase magnetic flux formed on the primary side is coupled by the transformer 22 and transmitted to the secondary side. Therefore, it is possible to change the output from the maximum output to zero by changing the phase of the two phases on the primary side. That is, when the control signal applied to the gate terminals of the switch elements T1 and T2 of each circuit is adjusted and the phase difference between the two circuits is 180 degrees, the maximum output is obtained, and when the phase difference between the two circuits is 0 degrees, the minimum output is obtained. Output (output zero). This is because the first coil L1 has a positive phase coupling, but the second coil L2 has a negative phase coupling.

  However, when the output is controlled by controlling the phase difference between the two circuits, the resonance current increases on the low output side, and the circuit loss on the primary side increases, so the efficiency decreases significantly on the low output side. End up.

  Therefore, in the present embodiment, the transformer structure shown in FIG. 6 is used as the transformer 22 in the circuit configuration of FIG. 5, and the auxiliary resonance coils L4 and L5 are magnetically forward-coupled and installed separately from the transformer of FIG. .

  FIG. 6 shows the configuration of the transformer 22. This is a configuration in which a coil for two primary phases is provided at the center of the tripod, and a secondary coil is provided outside the tripod. In the drawing, the first auxiliary coil L4 and the second auxiliary coil L5 on the primary side are omitted for convenience of explanation. Since the primary side two-phase coils L1 and L2 are provided so that the magnetic fluxes formed when currents flow in the same direction on the circuit cancel each other, they are magnetically reversely coupled. For this reason, when the phase difference is 0 degree, the same current flows in two phases due to symmetry. The magnetic fluxes formed by the two-phase currents in the transformer 22 cancel each other and no magnetic flux is formed, so that it does not function as an inductance. For this reason, when the phase difference is 0 degree, the inductance value of the transformer primary side coil is equivalently zero, and the resonance L value is only the auxiliary resonance coil, so that a large element current flows. The auxiliary resonance coils L4 and L5 are forward-coupled so that the resonance L component becomes large when current flows in the same direction on the circuit on the primary side. Specifically, L3 is omitted in FIG. 6, and L1 and L2 are L4 and L5.

  FIG. 7 shows a circuit configuration diagram when the auxiliary resonance coils L4 and L5 are magnetically forward-coupled. The difference from FIG. 5 is that the auxiliary resonance coils L4 and L5 are magnetically forward-coupled and the auxiliary coils L7 and L8 are connected to the secondary side.

  In the configuration of FIG. 7, when the phase difference between the two circuits is reduced, the primary coils L1 and L2 of the transformer 22 are reversely coupled and the L value is reduced equivalently, but the auxiliary resonant coils L4 and L5 are forward coupled. For this reason, the L value increases equivalently when the phase difference is small. Therefore, even if the phase difference is changed, the inductance value obtained by connecting the primary side coil of the transformer 22 and the auxiliary resonance coil in series does not vary much equivalently. As a result, even if the phase difference control is performed, the switch element can maintain the soft switching state, and the element current can also be approximately the same as in the case of the phase difference of 180 degrees. Further, by installing L7 and L8 on the secondary side, the energy stored in the inductor increases, so that the value of Ico in FIG. 3 in the resonance state can be easily made negative, so a soft switching state is ensured. easy.

In FIG. 7, each element is specifically exemplified as follows. In addition, the following is an illustration and it cannot be overemphasized that it is not limited to these numerical values.
L value:
L1 = L2 = 2.58 μH
L3 = 0.035μH × 2 pieces L4 = L5 = 1.0μH
L6 = 2μH
L7 = L8 = 0.01 μH
Binding rate:
k (L1 / L2) = − 0.9
K (L1 / L3) = 0.95
k (L2 / L3) = − 0.95
K (L4 / L5) = 0.6
C value:
C1 = 3.0nF
C2 = 3.0nF
C3 = 2.0μF

  Moreover, the simulation result using a computer is shown in FIGS. 8 shows a case where the phase difference is 180 degrees, FIG. 9 shows a case where the phase difference is 90 degrees, FIG. 10 shows a case where the phase difference is 60 degrees, and FIG. 11 shows a case where the phase difference is 30 degrees. In the figure, the drive frequency is 1.38 MHz with an input of 200 V and an output of 15 V.

  8 to 11, since the resonance voltage waveform is a complete resonance waveform, no switching occurs during this period, and switching is performed only when the element voltage is zero, so that all are soft switching. The maximum output is 2.19 KW when the phase difference is 180 degrees shown in FIG.

  FIG. 12 shows the results of FIGS. 8 to 11 collectively. The horizontal axis indicates the phase difference, and the vertical axis indicates the output power and output voltage. It can be seen that the output voltage is adjusted to 15 V, and the output power can be controlled with respect to the load by phase difference control.

  FIG. 13 shows the results of FIGS. 8 to 11 separately. The horizontal axis indicates the phase difference, and the vertical axis indicates the maximum device voltage and the maximum device current. The maximum device voltage and the maximum device current are maximized when the phase difference is around 120 degrees. However, when the phase difference is 120 degrees to 30 degrees, the element current decreases due to the effect of the auxiliary resonance coils L4 and L5 that are forward-coupled. Yes. Therefore, it can be seen from this result that a switch element having a withstand voltage of 1200 V and about 30 A may be used.

As shown in FIGS. 9 to 11, when the phase difference is smaller than 180 degrees, the symmetry between the two phases is lost, and the maximum value of the element voltage differs between the two phases. In order to reduce this difference, the value of the resonant capacitor in FIGS. 9 to 11 may be changed from the case where the phase difference is 180 degrees. Specifically, when the phase difference is 180 degrees C1 = C2 = 3.0 nF
However, when the phase difference is 90 degrees, 60 degrees, and 30 degrees,
C1 = 3.5nF
C2 = 3.0nF
Change to In an actual circuit configuration, a 3.0 nF capacitor is directly attached and the remaining 0.5 nF is connected in series with a parallel connection of an IGBT element and a diode, and 0.5 nF is connected by turning on / off the IGBT element. / Just switch the disconnected state. Thereby, the capacity of the resonant capacitor can be easily changed according to the phase difference. Of course, this is only an example, and any circuit configuration that can increase or decrease the capacitance of at least one of C1 and C2 can be used.

  When the output control is performed by changing the phase difference between the two phases, as shown in FIG. 13, the same resonance current flows in the primary side switching element even when the output is small. For this reason, the conversion efficiency is reduced on the low output side.

  Therefore, the maximum power is supplied by paralleling n circuits (n phase: where n is 2 or more) shown in FIG. 1 in parallel with the circuit shown in FIG. Further, fine adjustment can be made to the circuit of FIG. Of course, there is no problem with only the configuration of FIG.

  14 and 15 show a circuit configuration of a resonance type DC / DC converter device in a case where n pieces are arranged in parallel. FIG. 14A shows one circuit configuration, and FIG. 14B schematically shows the circuit configuration shown in FIG. FIG. 15 shows n circuits arranged in parallel, and is expressed using the schematic circuit shown in FIG. At the time of parallelization, the secondary diodes and the subsequent diodes are connected in parallel and connected to a smoothing capacitor and connected to a load via a filter coil L6. Output control is performed by changing the number of operating elements (number of phases).

  A specific gate driving method is performed using a gate signal 1 and a gate signal 2 having a phase difference of 180 degrees with respect to the gate signal 1, as shown in FIG. Each single-phase resonance circuit is divided into two groups, one group is driven by the gate signal 1 and the other group is driven by the gate signal 2. A gate signal is supplied to the group to be driven by turning on the switch, and the gate signal is kept off for the group to be stopped.

  When switching between operation and stop, control is performed so that the number operating in the group of gate signals 1 and the number operating in the group of gate signals 2 are as equal as possible. In the preferred embodiment, the number of the two groups is the same, and when the same number is operating, the fundamental wave which is the odd-numbered current component of the primary side and the odd-numbered harmonics after the third harmonic are included. One group and the other group cancel each other, and the primary side current component is obtained by adding a DC component to an even-numbered harmonic mainly including a second harmonic, thereby greatly reducing the high-frequency current component of the primary side circuit. it can. This is effective in reducing the size of the primary filter and reducing EMI. Even if the number of the two groups is not the same, if the difference between the numbers is about one, it can be regarded as substantially the same. This embodiment does not exclude the case where the difference in the number of two groups is one.

  Furthermore, regarding the configuration of inductors and transformers in parallel, arranging the single units in parallel may be disadvantageous in terms of physique and cost.

  Therefore, in this case, it is preferable to perform integral molding as shown in FIGS. Since the resonant circuit shown in FIG. 1 has a relatively simple configuration, it can be easily driven at MHz. In this frequency band, a small inductance value may be used. Specifically, the inductance value is several μH or less. With this value, the coil can be formed on the printed circuit board. That is, as shown in FIG. 16, the primary coil L1 and the auxiliary resonance coil L2 of the transformer of FIG. 14 are collectively formed on the printed circuit board 50, and a plurality of integrated ferrite cores 60 are formed on the printed circuit board 50. By adopting a structure that fits from above and below, a parallel resonance circuit can be formed simply by fitting the ferrite core 60 to the printed circuit board 50 on which wiring and coils are formed. Further, as shown in FIG. 17, the secondary circuit of the transformer of FIG. 14 is formed on a separate substrate, or a copper coil is integrally formed on an insulating substrate, and the ferrite core is overlaid on the primary coil. 14 can be collectively formed. In FIG. 17, a transistor switch 70 is a switch for supplying the gate signals 1 and 2 in FIG. 15 to the gates (A in FIG. 15) of the switch elements of each single-phase circuit. The side capacitor 74 is formed on a substrate different from the primary side.

  In the case of an automobile, the element specification is conversion from DC 200V to 400V, and the element voltage is 400Vpeak to 1200Vpeak. Therefore, the device breakdown voltage is about 1 kV to 1.7 kV. There is a SiC-FET as an element capable of high-speed switching with this withstand voltage, but it is of course not limited to this, and a GaN-FET can also be used. Si MOSFETs can be used when the input voltage is low, and IGBT elements can be used if the drive frequency is about several tens of kHz or less.

  In the present embodiment, the secondary side is rectified by a diode, but the MOSFET body diode is used in place of the secondary diode, and the conduction loss on the secondary side is made by turning the MOSFET conductive when energized. A so-called synchronous rectifier circuit configuration may be employed.

  20 Resonant DC / DC converter, 22 transformer, L1, L2 primary coil, L3 secondary coil, L4, L5 auxiliary resonant coil, T1, T2 switch element.

Claims (7)

A transformer comprising a primary coil connected to a DC power source and a secondary coil connected to an output load;
A switch element connected to the primary coil;
A capacitor connected in parallel to the switch element;
A rectifier circuit connected to the secondary coil;
A resonant DC / DC converter comprising:
The primary side coil is a two-phase coil including a first coil and a second coil connected in parallel to the DC power source, both provided in a single transformer,
A first auxiliary coil is connected in series to the first coil, and a second auxiliary coil is connected in series to the second coil,
The switch element includes a first switch element connected in series to the first coil and a second switch element connected in series to the second coil,
The capacitor includes a first capacitor connected in parallel to the first switch element and a second capacitor connected in parallel to the second switch element,
The magnetic flux formed by the first coil on the secondary coil and the magnetic flux formed by the second coil on the secondary coil are connected so as to be in opposite phases,
The resonance type DC / DC converter, wherein the first auxiliary coil and the second auxiliary coil are magnetically forward-coupled. The resonant DC / DC converter according to claim 1, wherein
Phase difference control means for changing a phase difference between a current generated by turning on and off the first switch element and a current generated by turning on and off the second switch element in a range of 0 degrees to 180 degrees. Resonance type DC / DC converter. The resonant DC / DC converter according to claim 2,
A resonance type DC / DC converter comprising: capacity control means for changing a capacity of at least one of the first capacitor and the second capacitor in accordance with a change in the phase difference. A transformer comprising a primary coil connected to a DC power source and a secondary coil connected to an output load;
An auxiliary coil connected in series to the primary coil;
A switch element connected in series to the primary coil;
A capacitor connected in parallel to the switch element;
A rectifier circuit connected to the secondary coil;
Two or more resonance type DC / DC converters comprising:
Resonance type DC / DC characterized in that output control is performed by switching each operation state and stop state of each resonance type DC / DC converter by switching each switch element of each resonance type DC / DC converter between a drive state and a stop state. Converter device. The resonant DC / DC converter device according to claim 4,
The two or more resonant DC / DC converters are divided into a first group and a second group,
The phase difference between the drive signal applied to each switch element of the resonant DC / DC converter belonging to the first group and the drive signal applied to each switch element of the resonant DC / DC converter belonging to the second group is A resonance type DC / DC converter device characterized by being 180 degrees. The resonance type DC / DC converter device according to claim 5,
The number of resonant DC / DC converters belonging to the first group and the number of resonant DC / DC converters belonging to the second group are the same. The resonance type DC / DC converter device according to any one of claims 4 to 6,
The resonance type DC / DC converter apparatus, wherein the primary side coil and the auxiliary coil of each resonance type DC / DC converter are formed on the same printed circuit board.

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