JP7183919B2 - switching power supply - Google Patents

Description

The present invention relates to a switching power supply device that transmits power bidirectionally.

In recent years, the use of secondary batteries has attracted attention. The use of secondary batteries requires bi-directional DC power control technology and conversion technology for charging and discharging. Small, low-cost, and highly efficient bidirectional DC/DC converters (switching power supply devices) are attracting attention as an important platform for this power conversion (see, for example, Non-Patent Document 1 and Patent Document 1).

IEEE TRANSACTIONS ON POWER ELECTRONICS,VOL.28,NO.4,APRIL 2013

JP 2014-183634 A

By the way, further miniaturization, lower cost, and higher efficiency are required for the above-described switching power supply device.

Therefore, it is desirable to provide a switching power supply capable of achieving further miniaturization, cost reduction and efficiency improvement.

A switching power supply device as one embodiment of the present invention includes a transformer having a plurality of primary coils and one or a plurality of secondary coils, a transformer connected in series with the plurality of primary coils, and a transformer having the plurality of primary coils connected in series. It has one or a plurality of switch elements for controlling connection and disconnection. This switching power supply further includes a plurality of primary side bridge circuits provided for each coil section separated by turning off one or more switch elements in the plurality of primary side coils, and one or more secondary side bridge circuits. Control enabling bidirectional power conversion by controlling switching of a secondary bridge circuit connected to the side coil, one or more switch elements, a plurality of primary bridge circuits, and a secondary bridge circuit circuit.

According to the switching power supply device as one embodiment of the present invention, by providing one or a plurality of switch elements for controlling series connection of a plurality of primary side coils, the primary side bridge circuit (when operating as a rectifier circuit) can be paralleled, and the voltage applied to the primary side bridge circuit and circuits connected to it can be lowered. As a result, further miniaturization, cost reduction and efficiency improvement can be achieved.

1 is a diagram showing a circuit configuration example of a DC-DC converter according to an embodiment of the present invention; FIG. FIG. 2 is a waveform diagram in the charging operation of the DC-DC converter of FIG. 1; 2 is a diagram showing an example of charging operation of the DC-DC converter of FIG. 1; FIG. FIG. 4 is a diagram illustrating an example of an operation following FIG. 3; FIG. 5 is a diagram illustrating an example of the operation following FIG. 4; FIG. 2 is a waveform diagram in the discharge operation of the DC-DC converter of FIG. 1; FIG. 7 is a diagram illustrating an example of the operation following FIG. 6; FIG. 8 is a diagram illustrating an example of the operation following FIG. 7; FIG. 9 is a diagram illustrating an example of the operation following FIG. 8; 2 is a diagram showing a modified example of the circuit configuration of the DC-DC converter of FIG. 1; FIG. 2 is a diagram showing a modified example of the circuit configuration of the DC-DC converter of FIG. 1; FIG. 2 is a diagram showing a modified example of the circuit configuration of the DC-DC converter of FIG. 1; FIG. 2 is a diagram showing a modified example of the circuit configuration of the DC-DC converter of FIG. 1; FIG. 2 is a diagram showing a modified example of the circuit configuration of the DC-DC converter of FIG. 1; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description is a specific example of the present invention, and the present invention is not limited to the following aspects.

<1. Embodiment>
[Constitution]
FIG. 1 shows a circuit diagram of a DC-DC converter 1 according to an embodiment of the invention. The DC-DC converter 1 includes three inductors L1, L2, L3 and two capacitors C9, C10. It is a DC-DC converter of the system. The DC-DC converter 1 includes a transformer 10 and a switch element SW.

The transformer 10 has two primary coils NP1 and NP2, one secondary coil NS, and a magnetic core CR. Two primary coils NP1, NP2 and one secondary coil NS are wound around a magnetic core CR. Each of the primary coils NP1, NP2 and the secondary coil NS may be composed of a single coil, or may be composed of a plurality of coils connected in series. Assuming that the number of turns of the primary coil NP1 is n1, the number of turns of the primary coil NP2 is n2, and the number of turns of the secondary coil NS is n3, the transformer 10 has a turns ratio of (n1+n2):n3. When the switch SW is off, the turns ratio of the transformer 10 is (n1 or n2):n3.

The switch element SW is connected in series with the two primary coils NP1 and NP2, and controls serial connection and separation of the two primary coils NP1 and NP2. The switch element SW is inserted between the primary side coil NP1 and the primary side coil NP2.

The DC-DC converter 1 further comprises two primary side bridge circuits 20,30. The two primary side bridge circuits 20 and 30 are provided for each coil section (here, the primary side coils NP1 and NP2) separated by turning off the switch element SW in the two primary side coils NP1 and NP2. there is

Each of the primary side bridge circuit 20 and the primary side bridge circuit 30 is a full bridge circuit including four switch elements. The primary side bridge circuit 20 includes two switch elements Q1 and Q2 corresponding to two switch elements (first switch elements) out of the four switch elements, and the switch elements Q1 and Q2 out of the four switch elements. It has two diodes D1 and D2 corresponding to two different switch elements (second switch elements). The primary side bridge circuit 30 includes two switch elements Q3 and Q4 corresponding to two switch elements (first switch elements) out of the four switch elements, and the switch elements Q3 and Q4 out of the four switch elements. It has two diodes D3 and D4 corresponding to two different switch elements (second switch elements).

The switch elements Q1, Q2, Q3, and Q4 are composed of switch elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switch elements Q1, Q2, Q3 and Q4 are configured including body diodes connected in parallel so as to be reverse biased with respect to a terminal I01, which will be described later. The primary side bridge circuit 20 and the primary side bridge circuit 30 are connected in parallel to the capacitors C1, C2, C3 and C4 connected in parallel to the switch elements Q1, Q2, Q3 and Q4, and the diodes D, D2, D3 and D4. and capacitors C5, C6, C7 and C8.

The two switch elements Q1 and Q2 are connected in series with each other, and the connection point P1 between the switch elements Q1 and Q2 is connected to one end of the primary side coil NP1 via a capacitor C9 and an inductor L1. It is That is, the capacitor C9 and the inductor L1 are provided between the connection point P1 between the switch element Q1 and the switch element Q2 and one end of the primary coil NP1. The two diodes D1 and D2 are connected in series with each other, and a connection point P2 between the diodes D1 and D2 is connected to the other end of the primary coil NP1.

The two switch elements Q3 and Q4 are connected in series with each other, and a connection point P3 between the switch elements Q3 and Q4 and one end of the primary side coil NP2 are connected via a capacitor C10 and an inductor L2. It is That is, the capacitor C10 and the inductor L2 are provided between the connection point P3 between the switch element Q3 and the switch element Q4 and one end of the primary side coil NP2. The two diodes D3 and D4 are connected in series with each other, and a connection point P4 between the diodes D3 and D4 is connected to the other end of the primary coil NP2. A switch element SW is provided between the other end of the primary coil NP1 and the other end of the primary coil NP2.

The DC-DC converter 1 further comprises a terminal IO1 and a ground terminal GND on the primary side. The DC-DC converter 1 further includes a capacitor C11 between the terminal IO1 and the ground terminal GND.

The DC-DC converter 1 further includes a secondary side bridge circuit 40 . The secondary bridge circuit 40 is a full bridge circuit including four rectifying elements. The secondary bridge circuit 40 has four switching elements Q5, Q6, Q7, Q8 corresponding to four rectifying elements.

The switch elements Q5, Q6, Q7 and Q8 are composed of switch elements such as MOSFETs. The switching elements Q5, Q6, Q7 and Q8 are configured including body diodes connected in parallel so as to be reverse biased with respect to a terminal I02 which will be described later. The secondary bridge circuit 40 has capacitors C13, C14, C15 and C16 connected in parallel to the switch elements Q5, Q6, Q7 and Q8.

The two switch elements Q5 and Q6 are connected in series with each other, and a connection point P5 between the switch element Q5 and the switch element Q6 and one end of the secondary side coil NS are connected via a capacitor C12 and an inductor L3. It is connected. That is, the capacitor C12 and the inductor L3 are provided between the connection point P5 between the switch element Q5 and the switch element Q6 and one end of the secondary coil NS. The two switch elements Q7 and Q8 are connected in series with each other, and a connection point P6 between the switch element Q7 and the switch element Q8 is connected to the other end of the secondary coil NS.

The DC-DC converter 1 further includes a terminal IO2 and a ground terminal GND on the secondary side. The DC-DC converter 1 further includes a capacitor C17 between the terminal IO2 and the ground terminal GND.

The DC-DC converter 1 further comprises a control circuit 50. FIG. The control circuit 50 is configured using a DSP (Digital Signal Processor), and controls the switching of the switch element SW, the two primary side bridge circuits 20 and 30, and the one secondary side bridge circuit 40 to perform bidirectional switching. Allows for power conversion. When the power conversion is performed from the primary side to the secondary side, the control circuit 50 provides a dead time between the switch elements Q1 to Q4 constituting the legs of the primary side bridge circuits 20 and 30. , to generate and output a signal of variable frequency and constant duty ratio. The driving frequency is a frequency obtained by feeding back the output voltage and performing digital calculation. In order to diagonally operate the primary side bridge circuits 20 and 30, the control circuit 50 inputs the same signal to the switch elements Q1 and Q4 and the same signal to the switch elements Q2 and Q3. The control circuit 50 synchronously rectifies the switch elements Q5 to Q8 forming the legs of the secondary bridge circuit 40 using signals slightly delayed in phase with respect to the switch elements Q1 to Q4. The control circuit 50 further provides a dead time between the switch elements Q5 to Q8 constituting the legs of the secondary bridge circuit 40 when performing power conversion from the secondary side to the primary side. generates and outputs a signal with variable frequency and constant duty ratio. The driving frequency is a frequency obtained by feeding back the output voltage and performing digital calculation. The control circuit 50 inputs the same signal to the switching elements Q5 and Q8 and inputs the same signal to the switching elements Q6 and Q7 in order to diagonally operate the secondary bridge circuit 40 . At this time, the control circuit 50 performs synchronous rectification for the switch elements Q1 to Q4 using a signal whose phase is slightly delayed with respect to the switch elements Q5 to Q8.

[motion]
Next, charging operation and discharging operation of the DC-DC converter 1 will be described. The DC-DC converter 1 converts power from a terminal IO1 and a ground terminal GND provided on the primary side to a terminal IO2 and a ground terminal GND provided on the secondary side, or converts power to a terminal IO2 and a ground terminal GND provided on the secondary side. Power can be converted from the terminal IO2 and the ground terminal GND in the direction of the terminal IO1 and the ground terminal GND provided on the primary side. That is, the DC-DC converter 1 has bidirectionality. For example, the DC-DC converter 1 converts power from the terminal IO1 and the ground terminal GND provided on the primary side to the terminal IO2 and the ground terminal GND provided on the secondary side, thereby converting the terminal IO2 and the ground terminal. It charges the battery connected to the terminal GND. For example, the DC-DC converter 1 converts power from a terminal IO2 and a ground terminal GND provided on the secondary side to a terminal IO1 and a ground terminal GND provided on the primary side, thereby converting the terminal IO2 and the ground terminal. Discharge the battery connected to the terminal GND.

Next, the charging operation and discharging operation of the battery in the DC-DC converter 1 will be described. The DC-DC converter 1 always operates the CLLC resonance circuit in the boost mode during charging and discharging. Therefore, the current flowing through the rectifier circuit is always discontinuous (ZCS (Zero Current Switching)). First, the battery charging operation in the DC-DC converter 1 will be described in detail, and then the battery discharging operation in the DC-DC converter 1 will be described in detail.

(charging operation)
First, the charging operation of the battery in the DC-DC converter 1 will be described. FIG. 2 is a waveform diagram in the charging operation of the DC-DC converter 1. FIG. 3, 4, and 5 show an example of the charging operation of the DC-DC converter 1. FIG. The control circuit 50 controls the switch element SW so as to always keep the ON state during the charging operation. DC-DC converter 1 turns on switch elements Q1 and Q4 by control circuit 50 at time t1 to transmit power, as shown in FIG. At this time, the DC-DC converter 1 performs rectification with the body diodes of the switch elements Q5 and Q8.

Next, at time t2, the DC-DC converter 1 turns on the switch elements Q5 and Q8 by the control circuit 50 to perform synchronous rectification, as shown in FIG. Next, at time t3, the DC-DC converter 1 turns off the switch elements Q1, Q4, Q5 and Q8 by the control circuit 50 to end the power transfer, as shown in FIG. At this time, the energy stored in the inductors L1 and L2 and the excitation inductor of the transformer 10 is used to charge the drain-source capacitance (capacitors C1 and C4) of the switching elements Q1 and Q4, and to charge the drains of the switching elements Q2 and Q3. Discharge the source-to-source capacitance (capacitors C2, C3).

When the drain-source capacitance (capacitors C2, C3) of the switch elements Q2, Q3 finishes discharging, the drain-source voltage of the switch elements Q2, Q3 becomes zero. By turning on the switch elements Q2 and Q3 at this timing, the DC-DC converter 1 can turn on the switch elements Q2 and Q3 by ZVS (zero volt switching). Also, regarding the switch elements Q1 and Q4, after the switch elements Q1 and Q4 are turned off, the current commutates to the capacitors C1 and C4. The period during which the current and voltage overlap during the transition is shortened. Therefore, the DC-DC converter 1 turns off the switch elements Q1 and Q4 at time t3, thereby turning off the switch elements Q1 and Q4 by ZVS (zero volt switching).

(discharge operation)
Next, the battery discharging operation in the DC-DC converter 1 will be described. FIG. 6 is a waveform diagram of the discharge operation of the DC-DC converter 1. FIG. The control circuit 50 controls the switch element SW so that it is always kept in the OFF state during the discharge operation. 7, 8, and 9 show an example of the discharge operation of the DC-DC converter 1. FIG. DC-DC converter 1 turns on switch elements Q5 and Q8 by control circuit 50 at time t1 to transmit power, as shown in FIG. At this time, the DC-DC converter 1 performs rectification with the body diode of the switch element Q1, the diode D2 and the primary coil NP1, and performs rectification with the body diode of the switch element Q4, the diode D3 and the primary coil NP2.

Next, at time t2, as shown in FIG. 8, the DC-DC converter 1 turns on the switching elements Q1 and Q4 by the control circuit 50, and rectification is performed by the switching element Q1, the diode D2, and the primary side coil NP1. At the same time, rectification is performed by the switch element Q4, the diode D3 and the primary side coil NP2.

Next, at time t3, the DC-DC converter 1 turns off the switch elements Q1, Q4, Q5 and Q8 by the control circuit 50 to end the power transfer, as shown in FIG. At this time, the energy stored in the inductor L3 and the exciting inductor of the transformer 10 is used to charge the drain-source capacitance of the switching elements Q5 and Q8 and discharge the drain-source capacitance of the switching elements Q6 and Q7.

At this time, when the drain-source capacitance of the switch elements Q6 and Q7 is discharged, the drain-source voltage of the switch elements Q6 and Q7 becomes zero. By turning on the switch elements Q6 and Q7 at this timing, the DC-DC converter 1 can turn on the switch elements Q6 and Q7 by ZVS (zero volt switching). Also, regarding the switch elements Q5 and Q8, after the switch elements Q5 and Q8 are turned off, the current commutates to the capacitors C13 and C16. and the voltage overlap period becomes shorter. Therefore, the DC-DC converter 1 turns off the switch elements Q5 and Q8 at time t3, thereby turning off the switch elements Q5 and Q8 by ZVS (zero volt switching).

[effect]
Next, the effects of the DC-DC converter 1 according to this embodiment will be described.

In this embodiment, a switch element SW is provided for controlling series connection and separation of the two primary coils NP1 and NP2. Since the winding ratio of the transformer 10 can be changed by turning on/off the switch element SW, the winding ratio of the transformer 10 is changed to a small value when performing power conversion from the secondary side to the primary side, for example. As a result, the voltage generated on the primary side can be kept low. As a result, the withstand voltage of the components used in the primary side bridge circuits 20 and 30 can be reduced compared to the case where a transformer with a large winding ratio is provided. Further, since there is no need to provide a high-voltage, high-power chopper circuit after the secondary bridge circuit 40, the number of parts can be reduced compared to the case where such a chopper circuit is provided. Efficiency can be increased in both charging and discharging.

Further, in the present embodiment, the primary side bridge circuit 20 is a full bridge circuit including two switch elements Q1, Q2 and two diodes D1, D2. Further, the primary side bridge circuit 30 is a full bridge circuit including two switch elements Q3, Q4 and two diodes D3, D4. As a result, the voltage applied to the elements forming the bridge can be lowered. Moreover, since the current flowing through the primary side rectifier circuit during discharge can be reduced, the conduction loss can be reduced. In addition, since the currents flowing through the diodes D1 to D4 are discontinuous, it is possible to employ low-cost diodes.

Further, in the present embodiment, in the primary bridge circuit 20, two of the four rectifying elements are composed of FETs, and the remaining two are composed of diodes. Furthermore, also in the primary side bridge circuit 30, two of the four rectifying elements are composed of FETs, and the remaining two are composed of diodes. Thereby, the control by the control circuit 50 can be simplified and the cost can be reduced as compared with the case where all the four rectifying elements are composed of FETs.

Further, in the present embodiment, two primary coils NP1 and NP2 and one secondary coil NS are wound around a common magnetic core CR. As a result, the transformer 10 can be made smaller than when the primary coil NP1 and the primary coil NP2 are wound on separate magnetic cores.

Further, in the present embodiment, an inductor L1 and a capacitor C9 are provided between the connection point P1 and the primary coil NP1, and an inductor L2 and a capacitor C10 are provided between the connection point P3 and the primary coil NP2. An inductor L3 and a capacitor C12 are provided between the secondary coil NS and the secondary bridge circuit 40 . As a result, in the bidirectional power conversion operation, it is possible to prevent biased magnetization of the transformer caused by variations in the switch elements and the drive circuit without special control or addition of parts. In addition, since all the elements on the primary side and the secondary side can be soft-switched, thermal design is facilitated. Furthermore, since the current flowing through the circuit is sinusoidal, the noise generated is also small.

Further, in the present embodiment, ZVS (zero volt switching) is performed on the switch elements (four switch elements Q1 to Q4) on the primary side when performing power conversion from the primary side to the secondary side. Furthermore, ZVS (zero voltage switching) and ZCS (zero current switching) are performed for the switch elements (four switch elements Q5 to Q8) on the secondary side. This can improve efficiency.

Further, in this embodiment, the secondary side bridge circuit 40 is a full bridge circuit including four switch elements Q5 to Q8. As a result, the device withstand voltage can be kept low. Further, by synchronously rectifying the elements of the full bridge circuit, conduction loss can be reduced and high efficiency can be obtained.

In addition, in the present embodiment, when performing power conversion from the secondary side to the primary side, ZVS (zero voltage switching) and ZCS (zero current switching) is performed. This can improve efficiency.

<2. Variation>
Next, a modification of the DC-DC converter 1 according to the above embodiment will be described.

[Modification A]
In the above embodiment, two primary coils NP1, NP2 and one secondary coil NS are wound around a common magnetic core CR. However, in the above-described embodiment, the transformer 10, for example, as shown in FIG. It may also have two separate cores CR1, CR2, one for each NP2).

In this case, the transformer 10 has two secondary coils NS1 and NS2 connected in series instead of the secondary coil NS. A secondary coil NS1 is wound, and a primary coil NP2 and a secondary coil NS2 are wound around a magnetic core CR2. In this case, compared to the case where two primary coils NP1, NP2 and one secondary coil NS are wound around the magnetic core CR, the amount of winding wound around each magnetic core CR1, CR2 is reduced to can be reduced. As a result, the heat dissipation of the transformer 10 can be enhanced.

[Modification B]
In the above-described embodiment and modification A, two of the four rectifying elements in the primary bridge circuit 20 are FETs, and the remaining two are diodes. Furthermore, in the primary side bridge circuit 30 as well, two of the four rectifying elements are composed of FETs, and the remaining two are composed of diodes. However, in the above embodiment and modification A, for example, as shown in FIGS. 11 and 12, in the primary side bridge circuits 20 and 30, all four rectifying elements may be FETs. In this case, the conduction loss can be reduced by synchronous rectification, so efficiency can be improved.

[Modification C]
In the above-described embodiment and modifications A and B, only one switch element SW for switching the primary coil is provided. However, in the embodiment and modifications A and B described above, for example, as shown in FIGS. 13 and 14, two or more switch elements SW for switching the primary coil may be provided. In this case, the winding ratio of the transformer 10 during charging and the winding ratio of the transformer 10 during discharging can be greatly changed.

Reference Signs List 1 DC-DC converter 10 transformer 20, 30 primary bridge circuit 40 secondary bridge circuit 50 control circuit C1, C2, C3, C4, C5, C6, C7, C8, C9 , C10, C11, C12, C13, C14, C15, C16, C17, C18... Capacitors CR, CR1, CR2, CR3... Magnetic cores D1, D2, D3, D4... Diodes L1, L2, L3, L4... Inductors , NP, NP1, NP2, NP3... primary side coils, NS, NS1, NS2, NS3... secondary side coils, P1, P2, P3, P4, P5, P6... connection points, Q1, Q2, Q3, Q4, Q5 , Q6, Q7, Q8, SW, SW1, SW2 . . . switch elements.

Claims (10)

a transformer having a plurality of primary coils and one or more secondary coils;
one or more switch elements connected in series to the plurality of primary coils and controlling serial connection and isolation of the plurality of primary coils;
a plurality of primary side bridge circuits provided for each coil portion separated by turning off the one or more switch elements in the plurality of primary side coils;
a secondary bridge circuit connected to the one or more secondary coils;
A switching power supply device comprising: a control circuit that enables bidirectional power conversion by controlling switching of the one or more switch elements, the plurality of primary side bridge circuits, and the secondary side bridge circuit. each said primary side bridge circuit includes four switch elements,
A first connection point between two first switch elements among the four switch elements is connected to one end of the corresponding coil portion, and a first connection point between two second switch elements among the four switch elements is connected to one end of the corresponding coil portion. 2. The switching power supply device according to claim 1, wherein two connection points are connected to the other ends of the corresponding coil portions. 3. The switching power supply device according to claim 2, wherein in each of the primary side bridge circuits, each of the first switch elements and each of the second switch elements is composed of FETs. 3. The switching power supply device according to claim 2, wherein in each of said primary side bridge circuits, each of said first switch elements is composed of an FET, and each of said second switch elements is composed of a diode. The switching power supply device according to any one of claims 1 to 4, wherein the transformer further has a magnetic core around which the plurality of primary coils and the one or more secondary coils are wound. The switching power supply device according to any one of claims 1 to 4, wherein the transformer further includes a plurality of magnetic cores provided separately for each of the coil portions. a first inductor and a first capacitor provided between the first connection point and the coil;
The switching power supply device according to any one of claims 2 to 4, further comprising a second inductor and a second capacitor provided between the secondary coil and the secondary bridge circuit. The secondary bridge circuit includes four rectifying elements,
A first connection point between two first rectifying elements among the four rectifying elements is connected to one end of one of the secondary coils or a plurality of the secondary coils connected in series with each other, and the four A second connection point between two second rectifying elements among the two rectifying elements is connected to the other end of one of the secondary coils or a plurality of the secondary coils connected in series with each other. 2. The switching power supply device according to 1. The control circuit performs zero-volt switching on the four switch elements when performing power conversion from the primary side to the secondary side, and further performs zero-volt switching and zero-current switching on the four rectifying elements. The switching power supply device according to claim 8. The control circuit performs zero-volt switching on the four rectifying elements when performing power conversion from the secondary side to the primary side, and further performs zero-volt switching and zero-current switching on the four switching elements. The switching power supply device according to claim 8.

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