JP2007295745A - Dc converter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a DC converter which can be downsized with high efficiency whose with input voltage is lower than its output voltage. <P>SOLUTION: This DC converter includes a transformer T2 which has a first primary winding P1, a second primary winding P2 reverse in polarity from that of the first primary winding, and a secondary winding S, a series circuit where the first primary winding and a switching element Q1 are connected in series to both ends of a DC power source Vin, a series circuit where the second primary winding and a switching element Q2 are connected to both ends of the DC power source, a voltage resonant capacitor Cv which is connected to both ends of the secondary winding S, a series resonance circuit which is connected to both ends of the secondary winding and in which a reactor L1 and a reactor L2 and a current resonant capacitor Ci are connected in series, and besides, which resonates a current, rectifying-smoothing circuits D3-D6 and C4 which rectify and smooth the voltage across the reactor L2, and a control circuit 10a which switches on or switches off the switching element Q1 and the switching element Q2 alternately, based on the output voltage of the rectifying-smoothing circuits. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a DC converter having high efficiency and low noise.

  FIG. 4 shows a circuit configuration diagram of a conventional DC converter (Patent Document 1). The DC converter shown in FIG. 4 is configured by a half-bridge circuit, and a series circuit of a switching element Q1 made of MOSFET and a switching element Q2 made of MOSFET is connected to both ends of the DC power supply Vin. The drain of the switching element Q2 is connected to the positive electrode of the DC power supply Vin, and the source of the switching element Q1 is connected to the negative electrode of the DC power supply Vin.

  A diode D1 and a voltage resonance capacitor Cv are connected in parallel between the drain and source of the switching element Q1, and a series circuit of the reactor Lr, the primary winding P of the transformer T1, and the current resonance capacitor Ci is connected. Yes. The reactor Lr includes a leakage inductance between the primary and secondary sides of the transformer T1, and an excitation inductance is equivalently connected to the primary winding P as a reactor Lp. A diode D2 is connected in parallel between the drain and source of the switching element Q2.

  The anode of the diode D3 and the cathode of the diode D4 are connected to one end (● side) of the secondary winding S of the transformer T1, and the cathode of the diode D3 is connected to one end of the smoothing capacitor C4. The anode is connected to the other end of the capacitor C4.

  The other end of the secondary winding S of the transformer T1 is connected to the anode of the diode D5 and the cathode of the diode D6. The cathode of the diode D5 is connected to one end of the capacitor C4. Connected to the end. A load RL is connected to both ends of the capacitor C4.

  The control circuit 10 performs PFM control (frequency control) by alternately turning on / off the switching elements Q1 and Q2 based on the output voltage Vo from the capacitor C4 so that the output voltage Vo of the capacitor C4 becomes constant. To control.

  Next, the operation of the conventional DC converter configured as described above will be described in detail with reference to the timing chart shown in FIG.

In FIG. 5, Vds1 is the drain-source voltage of the switching element Q1, Id1 is the drain current of the switching element Q1, _ID1 is the current of the diode D1, Vds2 is the drain-source voltage of the switching element Q2, and Id2 is the switching element Q2. drain _current, current _{I D2} is a diode D2 of, Vcv voltage across the voltage resonant capacitor Cv, Icv the current of the voltage resonant capacitor _Cv, current _{I L1} is a reactor _{L1, I L2} is the current of the reactor L2, Vci current current in the resonant capacitor _Ci, current _{I D3} are diodes _{D3, I D5} is the current of the diode D5.

  Note that it is assumed that both the switching element Q1 and the switching element Q2 have a dead time during which both the switching elements Q1 and Q2 are turned off, and the switching elements Q1 and Q2 are alternately turned on / off.

  First, in the period from time t0 to time t1, the switching element Q1 is turned off from on at time t0. In the state where the switching element Q1 is turned on, current flows through the path of Ci → Lp → Lr → Q1 → Ci on the primary side of the transformer T1, and the path of C4 → RL → C4 flows on the secondary side of the transformer T1. The current is flowing. When the switching element Q1 is turned off, the current flowing to the primary side of the transformer T1 is commutated from the switching element Q1 to the voltage resonance capacitor Cv, and the current flows through a path of Ci → L2 → Lr → Cv → Ci.

  Therefore, the voltage resonance capacitor Cv is charged to a voltage of Vin, although it is approximately 0 V when the switching element Q1 is on. Accordingly, since the voltage Vcv of the voltage resonant capacitor Cv is equal to the voltage Vds1 of the switching element Q1, the voltage Vds1 of the switching element Q1 rises from 0V to Vin. Further, since the voltage Vds2 of the switching element Q2 is (Vin−Vcv), it decreases from Vin to 0V.

  In the period from time t1 to time t2, when the voltage Vcv of the voltage resonance capacitor Cv rises to Vin at time t1, the diode D2 becomes conductive and follows the path of Ci → Lp (P) → Lr → D2 → Vin → Ci. Current flows. Further, the voltage of the secondary winding S of the transformer T1 reaches the output voltage Vo, and the secondary side of the transformer T1 has a current of a path of C4 → RL → C4 and a current of a path of S → D3 → C4 → D6 → S. Flows. Further, by turning on the gate signal of the switching element Q2 during the period from time t1 to time t2, the switching element Q2 performs a zero voltage switching (ZVS) and a zero current switching (ZCS) operation.

  In the period from time t2 to time t3, since the switching element Q2 is on, a current flows through a route of Vin → Q2 → Lr → Lp (P) → Ci → Vin, and the voltage Vci of the current resonance capacitor Ci increases. To go. On the secondary side of the transformer T1, a current in the path S → D3 → C4 → D6 → S and a current in the path C4 → RL → C4 flow. Since the secondary winding S is clamped by the voltage of the output voltage Vo and the primary winding P is clamped by the voltage of the turn ratio of the output voltage Vo, the primary side of the transformer T1 is the reactor Lr and the current resonance capacitor Ci. Resonant current is flowing.

  In the period from time t3 to time t4, at time t3, the voltage of the secondary winding S becomes equal to or lower than the output voltage Vo, and current flows through the secondary side of the transformer T1 along the path C4 → RL → C4. On the primary side, a current flows through a route of Vin → Q2 → Lr → Lp → Ci → Vin. On the primary side of the transformer T1, the sum of two reactors Lr and Lp (Lr + Lp) and a current resonance capacitor Ci The resonance current due to.

  In the period from time t4 to time t5, when the switching element Q2 is turned off at time t4, the current flowing to the primary side of the transformer T1 is commutated from the switching element Q2 to the voltage resonance capacitor Cv, and Lr → Lp → A current flows through a route of Ci → Cv → Lr.

  Therefore, the voltage resonance capacitor Cv is discharged to 0V although it is approximately Vin when the switching element Q2 is turned on. Accordingly, since the voltage Vcv of the voltage resonance capacitor Cv is equal to the voltage Vds1 of the switching element Q1, the switching element Q1 decreases from Vin to 0V. Further, since the voltage Vds2 of the switching element Q2 is (Vin−Vcv), it rises from 0V to Vin.

  In the period from time t5 to time t6, when the voltage Vcv of the voltage resonance capacitor Cv decreases to 0 V at time t5, the diode D1 becomes conductive, and current flows through the path of Lr → Lp (P) → Ci → D1 → Lr. Flowing. Further, the voltage of the secondary winding S of the transformer T1 reaches the output voltage Vo, and the secondary side of the transformer T1 has a current of a path of C4 → RL → C4 and a current of a path of S → D5 → C4 → D4 → S. Flows. Further, by turning on the gate signal of the switching element Q1 during the period from time t5 to time t6, the switching element Q1 performs zero voltage switching and zero current switching operations.

  In the period from time t6 to time t7, since the switching element Q1 is on, a current flows through a route of Ci → Lp (P) → Lr → Q1 → Ci, and the voltage Vci of the current resonance capacitor Ci decreases. . On the secondary side of the transformer T1, a current in a path S → D5 → C4 → D4 → S and a current in a path C4 → RL → C4 flow. Since the secondary winding S is clamped by the voltage of the output voltage Vo and the primary winding P is clamped by the voltage of the turn ratio of the output voltage Vo, the primary side of the transformer T1 is the reactor Lr and the current resonance capacitor. A resonance current due to Ci flows.

In the period from time t7 to time t0, at time t7, the voltage of the secondary winding S becomes equal to or lower than the output voltage Vo, and a current flows on the secondary side of the transformer T1 through a path of C4 → RL → C4. On the primary side, a current flows through a route of Ci → Lp → Lr → Q1 → Ci, and on the primary side of the transformer T1, a resonance current is generated by the sum of two reactors Lr and Lp (Lr + Lp) and a current resonance capacitor Ci. Flows.
JP 2003-319650 A

  As described above, in the conventional DC converter shown in FIG. 4, the reactors L1 and L2 and the current resonance are controlled by controlling the switching frequency of the switching elements Q1 and Q2 using a pulse signal with a constant duty of 50%. The resonant voltage by the capacitor Ci is changed to control the output voltage. For this reason, when the switching frequency is increased, the output voltage is decreased.

  In the conventional DC converter shown in FIG. 4, when the input voltage is low, the resonance current on the primary side of the transformer T1 increases, and the currents in the reactor L1 of the resonance circuit and the current resonance capacitor Ci also increase. For example, when the voltage value of the DC power source Vin is 20 V and 100 V and 1 A are consumed in the load RL, a resonance current of 10 A flows when the switching element Q1 is on, and a resonance of 10 A when the switching element Q2 is on. A current flows, and a resonance current of 10 A in total flows.

  For this reason, when the input voltage is low, the loss of the reactor L1 and the current resonance capacitor Ci increases, leading to a reduction in efficiency, and the components of the reactor L1 and the current resonance capacitor Ci increase, resulting in an increase in the size of the DC converter. Or had a problem of inviting.

  An object of the present invention is to provide a DC converter that has an input voltage lower than an output voltage and can be miniaturized with high efficiency.

  In order to solve the above problems, the present invention employs the following means. A first aspect of the present invention is a transformer having a first primary winding, a second primary winding having a polarity opposite to the polarity of the first primary winding, and a secondary winding, and a DC power source. A first series circuit in which a first primary winding of the transformer and a first switching element are connected in series at both ends of the transformer, and a second primary winding and a second switching of the transformer at both ends of the DC power supply. A second series circuit connected to the element, a voltage resonant capacitor connected to both ends of the secondary winding of the transformer, and a first reactor and a second reactor connected to both ends of the secondary winding of the transformer. And a current resonant capacitor connected in series and resonating current, a rectifying / smoothing circuit for rectifying and smoothing the voltage across the first reactor or the second reactor, and an output voltage of the rectifying / smoothing circuit Based on the first switching element Characterized in that it comprises a control circuit for alternately turning on / off said second switching element.

  According to a second aspect of the present invention, there is provided a series circuit in which a first switching element and a second switching element are connected in series to both ends of a DC power source, and a transformer connected to both ends of the first switching element or the second switching element. A primary winding, a voltage resonant capacitor connected to both ends of the secondary winding of the transformer, a first reactor, a second reactor, and a current resonant capacitor connected to both ends of the secondary winding of the transformer, Are connected in series and resonate current, a rectifying / smoothing circuit for rectifying and smoothing the voltage across the first reactor or the second reactor, and the first voltage based on the output voltage of the rectifying / smoothing circuit. And a control circuit for alternately turning on / off the switching element and the second switching element.

  According to a third aspect of the present invention, in the DC converter according to the first or second aspect, a diode is connected to both ends of each of the first switching element and the second switching element. .

  According to a fourth aspect of the present invention, in the DC converter according to any one of the first to third aspects, the control circuit sets a duty ratio of the first switching element and the second switching element to 50%. The output voltage is controlled by controlling the switching frequency.

  According to the present invention, since the series resonant circuit having the first reactor, the second reactor, and the current resonant capacitor is configured on the secondary side of the transformer, the secondary side output voltage of the transformer is the primary side input of the transformer. When the voltage is higher than the voltage, the current flowing through the series resonant circuit can be reduced as compared with the conventional circuit.

  Specifically, the current flowing through the two reactors and the current resonance capacitor is reduced to the voltage Vin / (2 × output voltage Vo) of the DC power supply. In addition, the current flowing through the first switching element and the second switching element is also ½ that of the conventional circuit, and in a DC converter with a low input voltage, these losses are reduced, and high efficiency and downsizing can be achieved.

  Hereinafter, some embodiments of the DC converter of the present invention will be described in detail with reference to the drawings.

  The DC converter according to the first embodiment is characterized in that the primary side of the transformer has a center tap configuration, and a resonance circuit is configured on the secondary side of the transformer.

  FIG. 1 is a circuit configuration diagram of a DC converter according to Embodiment 1 of the present invention. In the DC converter shown in FIG. 1, the transformer T2 includes a first primary winding P1 and a second primary winding P2 having a polarity opposite to that of the first primary winding P1 and a secondary winding. Line S. A series circuit of a first primary winding P1 of the transformer T2 and a switching element Q1 composed of a MOSFET is connected to both ends of the DC power supply Vin. A series circuit of a second primary winding P2 of the transformer T2 and a switching element Q2 made of a MOSFET is connected to both ends of the DC power supply Vin.

  The source of the switching element Q1 and the source of the switching element Q2 are connected to the negative electrode of the DC power supply Vin. A diode D1 is connected in parallel between the drain and source of the switching element Q1, and a diode D2 is connected in parallel between the drain and source of the switching element Q2.

  A voltage resonant capacitor Cv is connected to both ends of the secondary winding S of the transformer T2. Further, a series circuit of a reactor L1, a reactor L2, and a current resonance capacitor Ci is connected to both ends of the secondary winding S of the transformer T2, thereby constituting a resonance circuit that resonates current. Reactor L2 is a value sufficiently larger than reactor L1. The current resonance capacitor Ci is a value sufficiently larger than the voltage resonance capacitor Cv.

  The anode of the diode D3 and the cathode of the diode D4 are connected to both ends of the reactor L2, the cathode of the diode D3 is connected to one end of the smoothing capacitor C4, and the anode of the diode D4 is connected to the other end of the capacitor C4. ing.

  The other end of the secondary winding S of the transformer T2 is connected to the anode of the diode D5 and the cathode of the diode D6. The cathode of the diode D5 is connected to one end of the capacitor C4. Connected to the end. A load RL is connected to both ends of the capacitor C4.

  The control circuit 10a performs PFM control by alternately turning on / off the switching elements Q1 and Q2 based on the output voltage Vo from the capacitor C4, and controls the output voltage Vo of the capacitor C4 to be constant. The control circuit 10a controls the output voltage Vo by setting the duty of the switching elements Q1 and Q2 to 50% and controlling the switching frequency. That is, when the switching frequency is increased, the output voltage Vo is decreased.

  Next, the operation of the conventional DC converter configured as described above will be described in detail with reference to the timing chart shown in FIG. The names of the parts shown in FIG. 2 are the same as the names of the parts shown in FIG.

  It is assumed that both switching element Q1 and switching element Q2 have a dead time during which both switching elements Q1 and OFF are turned off, and switching elements Q1 and Q2 are alternately turned on / off.

  First, in the period from time t0 to time t1, the switching element Q1 is turned off from on at time t0. In the state where the switching element Q1 is on, current flows through the path of Vin → P1 → Q1 → Vin on the primary side of the transformer T2, and the voltage of Vin is applied to the first primary winding P1. ing. Accordingly, the voltage of the secondary winding S of the transformer T2 is a voltage multiplied by the turns ratio. When the turns ratio is P1: P2: S = 1: 1: N, the secondary winding S has a voltage of N · Vin. Will occur.

  On the secondary side of the transformer T2, a current flows through a path of S → L1 → L2 → Ci → S, and a current is supplied to the load RL through a path of C4 → RL → C4. When the switching element Q1 is turned off, the current that has flowed to the primary side of the transformer T2 disappears, and the current of the secondary winding S of the transformer T2 also disappears. Accordingly, the current flowing through the reactor L1 and the reactor L2 flows in the order L1-> L2-> Ci-> Cv-> L1, and the voltage resonance capacitor Cv is discharged. The voltage Vcv of the voltage resonance capacitor Cv decreases from the voltage N · Vin to the voltage −N · Vin. Since the voltage Vcv is equal to the voltage of the secondary winding S of the transformer T2, the voltages of the first primary winding P1 and the second primary winding P2 decrease to −Vin. Therefore, the voltage Vds2 of the switching element Q2 reaches 0V, and the voltage Vds1 of the switching element Q1 rises to 2 · Vin.

Next, in the period from time t1 to time t2, when the voltage Vcv of the voltage resonance capacitor Cv decreases to −N · Vin at time t1, the first primary winding P1 and the second primary winding P2 are changed. Since the voltage decreases to −Vin, the diode D2 becomes conductive, and the current I _D2 flows through the path P2 → Vin → D2 → P2 on the primary side of the transformer T2. Further, the voltage V _{L2 of the} reactor L2 reaches the output voltage Vo which is the voltage across the capacitor C4, and on the secondary side of the transformer T2, a current in the path C4 → RL → C4 flows, and S → L1 → L2 → Ci. The current in the path of S and the current in the path of L2, D5, C4, D4, and L2 flow. Further, by turning on the gate signal of the switching element Q2 at time t2, the switching element Q2 performs a zero voltage switching (ZVS) and a zero current switching (ZCS) operation.

  Next, in the period from time t2 to time t3, since the switching element Q2 is on, a current flows through the path of Vin → P2 → Q2 → Vin on the primary side. On the secondary side of the transformer T2, a current flows through a path of S → Ci → L2 → L1 → S, and the voltage Vci of the current resonance capacitor Ci decreases. In addition, a current in the path L2-> D5-> C4-> D4-> L2 and a current in the path C4-> RL-> C4 flow. Since the voltage of the reactor L2 is clamped by the voltage of the output voltage Vo, the secondary winding S has a resonance current flowing through the reactor L1 and the current resonance capacitor Ci. In addition, a current that is 1 / N times the current flowing through the secondary winding S flows through the second primary winding P2 of the transformer T2.

  Next, in the period from time t3 to time t4, the voltage of the reactor L2 becomes equal to or lower than the output voltage Vo at the time t3, and the current flows on the secondary side of the transformer T2 through the path of S → Ci → L2 → L1 → S. . On the primary side, a current that is 1 / N times the current flowing through the secondary winding S flows through a path of Vin → P2 → Q2 → Vin, and a current flows through the load RL through a path of C4 → RL → C4.

  In the period from time t4 to time t5, the switching element Q2 is turned off from on at time t4. In the state where the switching element Q2 is turned on, the current flows through the path of Vin → P2 → Q2 → Vin on the primary side of the transformer T2, and the voltage of Vin is applied to the second primary winding P2. ing. Therefore, the voltage of the secondary winding S of the transformer T2 is a voltage that is twice the turn ratio, and a voltage of −N · Vin is generated in the secondary winding S. On the secondary side of the transformer T2, a current flows through a path of S → Ci → L2 → L1 → S, and a current is supplied to the load RL through a path of C4 → RL → C4.

  When the switching element Q2 is turned off, the current flowing on the primary side of the transformer T2 disappears and the current of the secondary winding S of the transformer T2 disappears. Therefore, the current flowing through the reactor L1 and the reactor L2 flows in the order L2-> L1-> Cv-> Ci-> L2, and the voltage resonance capacitor Cv is charged. The voltage Vcv of the voltage resonance capacitor Cv increases from the voltage of −N · Vin to the voltage of N · Vin. Since the voltage Vcv is equal to the voltage of the secondary winding S of the transformer T2, the voltages of the first primary winding P1 and the second primary winding P2 rise to Vin. Accordingly, the voltage Vds1 of the switching element Q1 reaches 0 V, and the voltage Vds2 of the switching element Q2 increases to 2 · Vin.

In the period from time t5 to time t6, when the voltage Vcv of the voltage resonance capacitor Cv rises to N · Vin at time t5, the first primary winding P1 and the second primary winding P2 rise to Vin. Therefore, the diode D1 becomes conductive, and the current I _D1 flows through the path of P1 → Vin → D1 → P1 on the primary side of the transformer T2. Further, the voltage of the reactor L2 reaches the output voltage Vo, and the current on the secondary side of the transformer T2 flows along the path C4 → RL → C4, and the current on the path S → Ci → L2 → L1 → S , The current in the path of L2->D3->C4->D6-> L2 flows. Further, by turning on the gate signal of the switching element Q1 at time t5, the switching element Q1 performs zero voltage switching and zero current switching operation.

  In the period from time t6 to time t7, since the switching element Q1 is on, a current flows through the path of Vin → P1 → Q1 → Vin on the primary side. On the secondary side of the transformer T2, a current flows through a path of S → L1 → L2 → Ci → S, and the voltage Vc1 of the current resonance capacitor Ci increases. In addition, a current in a path L2-> D3-> C4-> D6-> L2 and a current in a path C4-> RL-> C4 flow. Since the voltage of the reactor L2 is clamped by the voltage of the output voltage Vo, the secondary winding S has a resonance current flowing through the reactor L1 and the current resonance capacitor Ci. In addition, a current that is 1 / N times the current flowing through the secondary winding S flows through the first primary winding P1 of the transformer T2.

  In the period from time t7 to time t0, at time t7, the voltage of the reactor L2 becomes equal to or lower than the output voltage Vo, and current flows through the secondary side of the transformer T2 through the path S → L1 → L2 → Ci → S. On the primary side, a current that is 1 / N times the current flowing through the secondary winding S flows through the path of Vin → P1 → Q1 → Vin. In addition, a current flows through the load RL through a path of C4 → RL → C4.

  As described above, according to the direct-current converter of the first embodiment, the series resonant circuit including the reactor L1, the reactor L2, and the current resonant capacitor Ci is configured on the secondary side of the transformer T2. When the output voltage is higher than the primary side input voltage of the transformer T2, the current flowing through the series resonant circuit can be reduced as compared with the conventional circuit.

  Specifically, the current flowing through the two reactors L1 and L2 and the current resonance capacitor Ci is reduced to Vin / (2 × Vo).

  In the conventional DC converter shown in FIG. 4, when the voltage value of the DC power source Vin is 20 V and 100 V and 1 A are consumed in the load RL, a resonance current of 10 A flows when the switching element Q1 is turned on, When the switching element Q2 is turned on, a resonance current of 10A flows, and a total resonance current of 10A flows.

  On the other hand, in the DC converter of the first embodiment, when the voltage value of the DC power source Vin is 20V and 100V, 1A is consumed in the load RL, the series resonance circuit is connected to the secondary side of the transformer T2. Therefore, when the switching element Q1 is turned on, a resonance current of 1A flows. When the switching element Q2 is turned on, a resonance current of 1A flows, and a total resonance current of 1A flows. For this reason, the resonance current of Example 1 becomes 1/10 of the conventional resonance current. This is obtained from Vin / (2 × Vo) = 20 / (2 × 100) = 1/10.

  Further, in the conventional DC converter shown in FIG. 4, 10A flows through the switching element Q1 when turned on, and 10A flows through the switching element Q2 when turned on. In the DC converter according to the first embodiment, the switching element Q1 flows through the switching element Q1. 5A flows when turned on, and 5A flows through the switching element Q2 when turned on. That is, the current flowing through the switching element Q1 and the switching element Q2 is also ½ that of the conventional circuit. Therefore, in the DC converter having a low voltage Vin of the DC power supply, those losses are reduced, and the size can be reduced with high efficiency.

  In addition, since the primary side of the transformer T2 has a center tap configuration and the source of the switching element Q1 and the source of the switching element Q2 are connected in common to the ground, the breakdown voltage of the switching element Q1 and the switching element Q2 can be reduced, and the high side No driver is required.

  FIG. 3 is a circuit configuration diagram of a DC converter according to Embodiment 2 of the present invention. In the DC converter of Embodiment 2 shown in FIG. 3, the primary side circuit of the transformer T3 is a half-bridge circuit, and the secondary side circuit of the transformer T3 is a reactor L1, a reactor L2, and a current resonance capacitor as shown in FIG. It is characterized by comprising a resonance circuit composed of Ci.

  Since the operation of the DC converter of the second embodiment is substantially the same as the operation of the DC converter of the first embodiment shown in FIG. According to the DC converter of the second embodiment, the same effect as that of the DC converter of the first embodiment can be obtained.

  The present invention can be applied to a DC-DC conversion type power supply circuit and an AC-DC conversion type power supply circuit.

It is a circuit block diagram of the direct-current converter of Example 1 of the present invention. It is a timing chart of the signal of each part of the direct-current converter of Example 1 of the present invention. It is a circuit block diagram of the DC converter of Example 2 of this invention. It is a circuit block diagram of the conventional DC converter. It is a timing chart of the signal of each part of the conventional DC converter shown in FIG.

Explanation of symbols

Vin DC power supply Lr, Lp, L1, L2 Reactor RL Load Q1, Q2 Switching elements T1, T2, T3 Transformer P Primary winding P1 First primary winding P2 Second primary winding S Secondary winding 10, 10a, 10b Control circuit D1, D2, D3, D4, D5, D6 Diode Ci Current resonance capacitor Cv Voltage resonance capacitor C4 Capacitor

Claims (4)

A transformer having a first primary winding and a second primary winding and a secondary winding having opposite polarities to the polarity of the first primary winding;
A first series circuit in which a first primary winding of the transformer and a first switching element are connected in series to both ends of a DC power source;
A second series circuit in which a second primary winding and a second switching element of the transformer are connected to both ends of the DC power supply;
A voltage resonant capacitor connected across the secondary winding of the transformer;
A series resonant circuit connected to both ends of the secondary winding of the transformer, a first reactor, a second reactor, and a current resonant capacitor connected in series and resonating current;
A rectifying / smoothing circuit that rectifies and smoothes the voltage across the first reactor or the second reactor;
A control circuit that alternately turns on and off the first switching element and the second switching element based on an output voltage of the rectifying and smoothing circuit;
A direct current conversion device comprising: A series circuit in which a first switching element and a second switching element are connected in series to both ends of a DC power supply;
A primary winding of a transformer connected to both ends of the first switching element or the second switching element;
A voltage resonant capacitor connected across the secondary winding of the transformer;
A series resonant circuit connected to both ends of the secondary winding of the transformer, a first reactor, a second reactor, and a current resonant capacitor connected in series and resonating current;
A rectifying / smoothing circuit that rectifies and smoothes the voltage across the first reactor or the second reactor;
A control circuit that alternately turns on and off the first switching element and the second switching element based on an output voltage of the rectifying and smoothing circuit;
A direct current conversion device comprising:   3. The DC converter according to claim 1, wherein a diode is connected to both ends of each of the first switching element and the second switching element.   2. The control circuit according to claim 1, wherein the control circuit controls the output voltage by setting a duty ratio of the first switching element and the second switching element to 50% and controlling a switching frequency. 4. The DC converter according to any one of items 3.

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