TWI474599B - Bidirectional dc/dc converter - Google Patents

Description

Bidirectional DC/DC converter

The present invention relates to a DC/DC converter circuit, and more particularly to a bidirectional DC/DC converter.

In a power conversion system, the DC/DC converter is a basic power conversion module, and is also a widely used power conversion module. The isolated DC/DC converter circuit can be implemented by using several basic converter circuits, such as a full bridge converter circuit, a half bridge converter circuit, a push-pull converter circuit, and the like. The basic working principle of the DC/DC isolated conversion circuit is that the energy is transmitted from the input end of the first conversion circuit to the second conversion circuit by using the periodic operation mode of the switching switch on and off of the basic converter circuit. The output terminal; at the same time, the desired output voltage is obtained via the coil turns ratio of the transformer.

The above basic converter circuits have different circuit characteristics and different cost in component use. Therefore, various basic converter circuits are used to design different DC/DC converters, in addition to different loads. Power requirements can also meet different circuit design cost constraints. However, since power is often lost in the process of transmission through the converter, the power conversion efficiency of the conversion circuit, that is, the ratio of the output power to the input power, is generally regarded as a judgment index for the characteristics of the conversion circuit. Power conversion efficiency can vary depending on how the circuit is used. Therefore, the circuit design can be changed to improve power conversion efficiency.

The existing DC/DC isolated conversion circuit is mostly single-directional energy transmission. When energy is required to be transmitted from the first power supply side to the second power supply side and from the second power supply side to the first power supply side, it is often required. Use two sets of circuits, which is expensive Circuit cost.

In view of this, the present invention provides a bidirectional DC/DC converter that controls the circuit design of the first conversion circuit and the second conversion circuit on both sides of the transformer to achieve bidirectional flow of current and reuse of resonance to limit each energy. The current during transmission increases the convenience of operating the bidirectional DC/DC converter.

The present invention provides a bidirectional DC/DC converter coupled between a first power supply side and a second power supply side, including a transformer, a first conversion circuit, a second conversion circuit, and a resonant circuit. The transformer has a primary side winding and a secondary side winding corresponding to the magnetic coupling; the first conversion circuit has a plurality of first switching elements, each of the first switching elements includes a switching switch and a parallel switching switch diode, each of the first switches The component is coupled to the primary winding of the transformer; the second switching circuit has a plurality of second switching components, each of the second switching components includes a switching switch and a diode of a parallel switching switch, and each of the second switching components is coupled to the transformer a secondary winding; and a resonant circuit having a first inductor, at least a first capacitor, and a second inductor, wherein the first inductor is connected in series with the secondary winding of the transformer, and the at least one first capacitor is connected to the second converter circuit The second inductor is coupled between the second power supply side and the second conversion circuit; wherein the current is transmitted from the first power supply side to the second power supply side, and at least one of the first switching elements is turned on to enable the first conversion circuit Discharging, at least one of the second switching elements is turned on to charge the second switching circuit, and the switching period of at least one of the first switching elements is substantially the same a resonance period of the first inductor and the at least one first capacitor; wherein the current is transmitted from the second power source side to the first power source side, and at least one of the first switching elements is turned on to charge the first conversion circuit, and the second At least one of the switching elements is turned on, so that the second turn The circuit is discharged, and the on-period of the at least one of the first switching elements is substantially the same as the period in which the current resonance of the resonant circuit reaches a zero value or a value close to zero.

In an embodiment of the present invention, when the switching switches of at least one of the first switching elements are turned on, the switching switches of the second switching elements are turned off; when the switching switches of the first switching elements are turned off, At least one of the diodes of the first switching element is turned on, and at least one of the switching elements of the second switching element is turned on.

In an embodiment of the present invention, the first inductance is a leakage inductance of the transformer.

In an embodiment of the present invention, the on-period of the switching switch of at least one of the first switching elements is substantially the same as the resonant period of the first inductor and the at least one first capacitor, and the current is limited by the first inductance of the resonant circuit. , reducing power loss.

In an embodiment of the present invention, the first conversion circuit is a full bridge circuit, a half bridge circuit, or a push-pull circuit.

In an embodiment of the present invention, the second conversion circuit is a full bridge circuit, a half bridge circuit, or a push-pull circuit.

The present invention provides a bidirectional DC/DC converter coupled between a first power supply side and a second power supply side, including: a transformer, a first conversion circuit, a second conversion circuit, and a resonant circuit. The transformer has a primary side winding and a secondary side winding corresponding to the magnetic coupling; the first conversion circuit has a plurality of first switching elements, each of the first switching elements includes a switching switch and a parallel switching switch diode, each of the first switches The component is coupled to the primary winding of the transformer; the second switching circuit has a plurality of second switching components, each of the second switching components includes a switching switch and a diode of a parallel switching switch, and each of the second switching components is coupled to the transformer a secondary winding; and the resonant circuit has a The first inductor, the at least one first capacitor and the second capacitor, the first inductor is connected in series with the secondary winding of the transformer, the at least one first capacitor is connected to the second conversion circuit, and the second capacitor is coupled to the first inductor and the second inductor Between the two conversion circuits, wherein the current is transmitted from the first power supply side to the second power supply side, at least one of the first switching elements is turned on, the first conversion circuit is discharged, and at least one of the second switching elements is turned on. Charging the second conversion circuit, the on-period of the at least one of the first switching elements is substantially the same as the resonant period of the first inductance and the at least one first capacitance; wherein the current is transmitted from the second power supply side to the first On the power supply side, at least one of the first switching elements is turned on to charge the first conversion circuit, and at least one of the second switching elements is turned on to discharge the second conversion circuit, and at least one of the first switching elements The conduction period of the polar body is substantially the same as the period in which the current resonance of the resonant circuit reaches a zero value or a value close to zero.

In summary, the basic working principle of the bidirectional DC/DC converter of the present invention controls the circuit design of the first conversion circuit and the second conversion circuit on both sides of the transformer to achieve bidirectional flow of current and reuse of resonance. Current per energy transfer. When determining the energy transfer direction, it is also possible to select only the switching element on the transformer side to be controlled, while the other side of the switching element maintains the off state, and only the natural on current of the diode exists.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

The invention is described in detail below with reference to the accompanying drawings,

The technical content, the purpose of the invention and the effects achieved by the present invention are described below with reference to the following figures: 1 is a circuit diagram of a bidirectional DC/DC converter of an embodiment of the present invention. Please refer to Figure 1. A bidirectional DC/DC converter 1 is coupled between a first power supply side P1 and a second power supply side P2, and includes a transformer 10, a first conversion circuit 11, a second conversion circuit 12, and a resonant circuit. . The bidirectional DC/DC converter 1 of the present invention can transmit current bidirectionally, for example, current is transmitted from the first power supply side P1 to the second power supply side P2, or current is transmitted from the second power supply side P2 to the first power supply side P1.

The transformer 10 has a primary side winding N1 and a secondary side winding N2 corresponding to magnetic coupling. In practice, the transformer 10 transmits or converts energy through the magnetically coupled primary side winding N1 and the secondary side winding N2, for example, the number of turns of the primary side winding N1 is larger than the number of turns of the secondary side winding N2, thereby using the transformer 10 voltage drop, for example, to reduce the voltage of 120 volts to a voltage of 12V volts. Of course, the number of turns of the primary side winding N1 may be equal to or less than the number of turns of the secondary side winding N2, whereby the transformer 10 transmits energy or boosts the voltage, and the embodiment does not limit the aspect of the transformer 10, and the rest is the same. , I will not repeat them here.

The first conversion circuit 11 has a plurality of first switching elements 111, 112, 113, 114, and each of the first switching elements 111, 112, 113, 114 includes a switching switch S1, S2, S3, S4 and a reverse connection The diodes D1, D2, D3, and D4 of the switches S1, S2, S3, and S4 are coupled to the primary side windings N1 of the transformer 10, and the first switching elements 111, 112, 113, and 114 are coupled to the primary windings N1 of the transformer 10. In practice, the first switching elements 111, 112, 113, 114 are used to turn the first switching circuit 11 on or off, whereby the first switching circuit 11 can be discharged or charged. The switching switches S1, S2, S3, and S4 of the first switching elements 111, 112, 113, and 114 are connected in parallel with the diodes D1, D2, D3, and D4, thereby switching the switches S1, S2, S3, and S4 to be turned off. The reverse-connected diodes D1, D2, D3, and D4 are turned on, or the switches S1, S2, S3, and S4 are turned on, but are reversed. The connected diodes D1, D2, D3, and D4 are turned off. The switch S1, S2, S3, S4 is used to turn on or off the circuit of the first switching element 111, 112, 113, 114, and the switch S1, S2, S3, S4 can be realized by a power transistor or a field effect transistor. This embodiment does not limit the aspects of the first switching elements 111, 112, 113, 114, the switches S1, S2, S3, S4 and the diodes D1, D2, D3, D4.

The second conversion circuit 12 has a plurality of second switching elements 115, 116, 117, 118, and each of the second switching elements 115, 116, 117, 118 includes a switching switch S5, S6, S7, S8 and a reverse parallel switching The diodes D5, D6, D7, and D8 of the switches S5, S6, S7, and S8, and the second switching elements 115, 116, 117, and 118 are coupled to the secondary side winding N2 of the transformer 10. In practice, the second switching element 115, 116, 117, 118 is used to turn the second switching circuit 12 on or off, whereby the second switching circuit 12 can be discharged or charged. The switching switches S5, S6, S7, and S8 of the second switching elements 115, 116, 117, and 118 are connected in parallel with the diodes D5, D6, D7, and D8, thereby switching the switches S5, S6, S7, and S8 to be turned off. The diodes D5, D6, D7, and D8 that are connected in reverse are turned on; or when the switches S5, S6, S7, and S8 are turned on, and the diodes D5, D6, D7, and D8 that are connected in reverse are turned off. The switch S5, S6, S7, S8 is used to turn on or off the circuit of the second switching element 115, 116, 117, 118, and the switch S5, S6, S7, S8 can be realized by a power transistor or a field effect transistor. This embodiment does not limit the aspects of the second switching elements 115, 116, 117, 118, the switches S5, S6, S7, S8 and the diodes D5, D6, D7, D8.

In detail, when the first conversion circuit 11 is discharged, energy is transferred or converted via the primary side winding N1 of the transformer 10 and the secondary side winding N2, whereby the second conversion circuit 12 is charged. Conversely, when the first conversion circuit 11 is charged, energy is transferred or converted via the primary side winding N1 of the transformer 10 and the secondary side winding N2, whereby the second conversion circuit 12 is discharged. In addition, the first conversion circuit 11 is a full bridge circuit, and the second conversion circuit 12 is a full bridge circuit, thereby forming a bidirectional DC/DC of the full bridge circuit. Converter 1. In other embodiments, the first conversion circuit 11 is a full bridge circuit, a half bridge circuit, or a push-pull circuit, and the second conversion circuit 12 is a full bridge circuit, a half bridge circuit, or a push-pull circuit. This constitutes a bidirectional DC/DC converter 1. This embodiment does not limit the aspect of the first conversion circuit 11 and the second conversion circuit 12 in FIG.

The resonant circuit has a first inductor 13 , at least one first capacitor 14 and a second inductor 15 . The first inductor 13 is connected in series with the secondary winding N2 of the transformer 10 , and the at least one first capacitor 14 is connected to the second converter circuit 12 . The second inductor 15 is coupled between the second power supply side P2 and the second conversion circuit 12 . In practice, the bidirectional DC/DC converter 1 of the present embodiment includes an LCL resonant circuit design having a first inductor 13, a first capacitor 14 and a second inductor 15.

In detail, the first inductor 13 is a transformer leakage inductance for limiting current. For example, in the transformer 10, the coupling coefficient of the primary side winding N1 and the secondary side winding N2 is less than 1, and the partial winding of the transformer 10 does not have a transformation effect, and only has a function of suppressing the inductance. The secondary side winding N2 of the transformer 10 is connected in parallel with the first capacitor 14. The first capacitor 14 is, for example, a resonant capacitor, whereby the first inductor 13 and the first capacitor 14 of the secondary winding N2 of the transformer 10 can be charged and discharged. Reciprocating operation. Of course, the second inductor 15 acts as a resonant filter of the first inductor 13 and the first capacitor 14, whereby the LCL resonant circuit can reach a current that limits the transfer of energy.

When the current is transmitted from the first power supply side P1 to the second power supply side P2, at least one of the first switching elements 111, 112, 113, 114 is turned on, the first conversion circuit 11 is discharged, and is transmitted via the transformer 10. At least one of the two switching elements 115, 116, 117, 118 is turned on to charge the second switching circuit 12, and the switching switches S1, S2, S3, S4 of at least one of the first switching elements 111, 112, 113, 114 The on period is substantially the same as the resonance period of the first inductor 13 and the at least one first capacitor 14. The on period of the switches S1, S2, S3, and S4 of at least one of the first switching elements 111, 112, 113, and 114 Roughly the same as the resonant period of the first inductor 13 and the at least one first capacitor 14, the current is limited by the first inductor 13 of the resonant circuit, reducing power loss.

When the current is transmitted from the second power supply side P2 to the first power supply side P1, at least one of the first switching elements 111, 112, 113, and 114 is turned on, the first conversion circuit 11 is charged, and is transmitted via the transformer 10. At least one of the two switching elements 115, 116, 117, and 118 is turned on to discharge the second switching circuit 12, and at least one of the first switching elements 111, 112, 113, and 114 is diodes D1, D2, D3, and D4. The turn-on period is approximately the same as the current resonance of the resonant circuit. The on periods of the diodes D1, D2, D3, and D4 of at least one of the first switching elements 111, 112, 113, and 114 are substantially the same as the period in which the current resonance of the resonant circuit reaches a zero value or a near zero value. Where the current resonates to a zero value or approaches a near zero value, reducing power loss.

It is worth mentioning that when at least one of the first switching elements 111, 112, 113, 114 switches the switches S1, S2, S3, S4, at least one of the second switching elements 115, 116, 117, 118 The switch S5, S6, S7, S8 is turned off; the switch S1, S2, S3, S4 of at least one of the first switching elements 111, 112, 113, 114 is turned off and the diode D1 is connected in reverse When D2, D3, and D4 are turned on, the switches S5, S6, S7, and S8 of at least one of the second switching elements 115, 116, 117, and 118 are turned on. In practice, the present invention operates through the switches S1, S2, S3, S4, S5, S6, S7, S8 of the first and second switching elements 111, 112, 113, 114, 115, 116, 117, 118. The control current is bidirectionally transmitted and the current through the energy transfer is limited by a resonant circuit.

The circuit operation of the bidirectional DC/DC converter 1 of the present invention can be divided into four stages, and the current flow direction of the circuit can be distinguished into two cases, one being "transmission from the first power supply side P1 to the second power supply side P2" , the other is "passing from the second power side P2 To the first power supply side P1".

Next, the circuit operation of the bidirectional DC/DC converter will be further explained. 2A and 2B are schematic diagrams showing the circuit operation of the bidirectional DC/DC converter of the present invention. Please refer to FIG. 2A and FIG. 2B.

In phase one, the first and second switching elements 211, 214, 215, 218 are turned on, and the first and second switching elements 212, 213, 216, 217 are turned off. As shown in FIG. 2A, when the current is transmitted from the first power supply side P1 to the second power supply side P2, the first power supply side P1 is discharged, and the current flows out from the positive terminal of the first power supply side P1, flowing through the first switching element 211. The switch S1 enters the end point of the primary side winding N1 of the transformer 20, flows out from the end point b of the primary side winding N1 of the transformer 20, flows through the changeover switch S4 of the first switching element 214, and flows into the first power supply side P1. Negative terminal. On the second power supply side P2, the current flows from the c-terminal end of the secondary side winding N2 of the transformer 20, and sequentially flows through a first inductor 23, a reverse parallel diode D5 of the second switching element 215, and a first The capacitor 24 and the anti-parallel diode D8 of the second switching element 218 flow into the d-end of the secondary winding N2 of the transformer 20, and at this time, the second power supply side P2 is filtered by a second inductor 25 to achieve charging. .

As shown in FIG. 2B, when the current is transmitted from the second power supply side P2 to the first power supply side P1, the anti-parallel diodes D1 and D4 of the first switching elements 211 and 214 are turned on, and the first power supply side P1 is charged. The negative terminal of the first power supply side P1 flows out, flows through the anti-parallel body D4 of the first switching element 214, enters the b-end of the primary-side winding N1 of the transformer 20, and then ends from the a-side of the primary-side winding N1 of the transformer 20. The point flows out, flows through the reverse parallel diode D1 of the first switching element 211, and flows into the positive terminal of the first power supply side P1; and on the second power supply side P2, the current flows from the c-terminal of the secondary winding N2 of the transformer 20 After flowing in, and then flowing out from the d-end of the secondary winding N2 of the transformer 20, the switching switch S8 of the second switching element 218, the first capacitor 24, and the switching switch S5 of the second switching element 215 are sequentially flowed through. The first inductor 23 flows into the transformer 20 again The c-terminal end of the secondary side winding N2, at this time, the second power supply side P2 is filtered by a second inductor 25 to achieve discharge.

Since the on-times of the switching switches S1 and S4 of the first switching elements 211 and 214 and the resonance period of the first inductor 23 and the first capacitor 24 are the same, when the switching switches S1 and S4 of the first switching elements 211 and 214 are turned on, The current limiting action of the first inductor 23 has a very small current value. Similarly, since the on-times of the diodes D1, D4 of the first switching elements 211, 214 are exactly equal to the resonance period, the switching switches S1, S4 of the first switching elements 211, 214 are turned off and the dipoles D1, D4 are inverted. When turned on, the current resonates to a value of zero or a small current value close to zero, so that the circuit current values of the switching switches S1, S4 of the first switching elements 211, 214 are both turned on and off, whereby the first switching elements 211, 214 The energy loss is also small.

Of course, when the switching switches S1, S4 of the first switching elements 211, 214 are turned on, the switching switches S5, S8 of the second switching elements 215, 218 are turned off, whereby the first switching circuit 21 is charged, and the second switching circuit 22 is discharged. Similarly, when the changeover switches S1, S4 of the first switching elements 211, 214 are turned off, the switching switches S5, S8 of the second switching elements 215, 218 are turned on, whereby the first switching circuit 21 is discharged, and the second switching circuit 22 is charged. Therefore, the present invention realizes bidirectional current transmission by controlling the first conversion circuit 21 and the second conversion circuit 22 on both sides of the transformer 20.

In phase two, all of the switches S1, S2, S3, S4, S5, S6, S7, S8 of the first and second switching elements 211, 212, 213, 214, 215, 216, 217, 218 are all turned off. There is no energy transfer on either side of the transformer 20. If the transformer 20 is regarded as an ideal transformer, no current flows on both sides of the transformer 20.

3A and 3B are schematic diagrams showing the circuit operation of the bidirectional DC/DC converter of the present invention. Please refer to FIG. 3A and FIG. 3B.

In phase three, the first and second switching elements 312, 313, 316, 317 are turned on, and the first and second switching elements 311, 314, 315, 318 are turned off. As shown in Figure 3A, When the current is transmitted from the first power source side P1 to the second power source side P2, the first power source side P1 is discharged, the current flows out from the positive terminal of the first power source side P1, flows through the switch S3 of the first switching element 313, and enters the transformer. The end point b of the primary side winding N1 of 30 flows out from the end point a of the primary side winding N1 of the transformer 30, flows through the changeover switch S2 of the first switching element 312, and flows into the negative terminal of the first power supply side P1; The second power supply side P2, the current flows from the d end of the secondary side winding N2 of the transformer 30, and sequentially flows through the reverse parallel diode D7 of the second switching element 317, a first capacitor 34, and a second switching element 316. The anti-parallel diode D6 and a first inductor 33 are further flowed into the c-terminal end of the secondary side winding N2 of the transformer 30. At this time, the second power supply side P2 is filtered by a second inductor 35 to achieve charging.

As shown in FIG. 3B, when the current flow is transmitted from the second power supply side P2 to the first power supply side P1, the first power supply side P1 is charged, and the current flows out from the negative terminal of the first power supply side P1, flowing through the first switching element. The anti-parallel diode D2 of 312 enters the a terminal end of the primary side winding N1 of the transformer 30, and then flows out from the end point b of the primary side winding N1 of the transformer 30, and flows through the anti-parallel body of the first switching element 313. D3, flowing into the positive terminal of the first power supply side P1; and on the second power supply side P2, current flows from the d end of the secondary winding N2 of the transformer 30, and then the c-terminal of the secondary winding N2 of the transformer 30 After flowing out, it flows through a first inductor 33, a switch S6 of the second switching element 316, a first capacitor 34, a switch S7 of the second switching element 317, and then flows into the secondary winding N1 of the transformer 30. The d end point, at this time, the second power supply side P2 is filtered by a second inductor 35 to achieve discharge.

Similarly to the phase, since the on-time of the switching switches S3, S2 of the first switching elements 313, 312 and the first inductor 33 are the same as the resonance period of the first capacitor 34, the switching switches S3 of the first switching elements 313, 312, When S2 is turned on, the current value is extremely small due to the current limiting action of the first inductor 33. Similarly, since the on-times of the diodes D3, D2 of the first switching elements 313, 312 are exactly equal to the resonance period, at the first opening When the switching switches S3, S2 of the closing elements 313, 312 are turned off and the anti-parallel diodes D3, D2 are turned on, the current resonates to a value of zero or a small value close to zero, so that the switching switch S3 of the first switching elements 313, 312 The circuit current values are small when S2 is turned on and off, whereby the energy loss of the first switching elements 313 and 312 is also small.

Of course, when the switching switches S3, S2 of the first switching elements 313, 312 are turned on, the switching switches S6, S7 of the second switching elements 316, 317 are turned off, whereby the first switching circuit 31 is charged, and the second switching circuit 32 is discharged. Similarly, when the changeover switches S3, S2 of the first switching elements 313, 312 are turned off, the changeover switches S6, S7 of the second switching elements 316, 317 are turned on, whereby the first conversion circuit 31 is discharged, and the second conversion circuit 32 is charged. Therefore, the present invention realizes bidirectional current transmission by controlling the first conversion circuit 31 and the second conversion circuit 32 on both sides of the transformer 30.

Phase 4 works in the same way as Phase 2, and after Phase 4, the circuit operation will loop back to Phase 1, and so on.

In summary, referring to FIG. 1, the bidirectional DC/DC converter 1 is based on the voltage relationship between the first power supply side P1 and the second power supply side P2 to automatically realize energy transfer. It is assumed that the number of turns of the a-end to the b-end of the primary winding N1 of the transformer 10 is W1, and the number of turns of the c-end to the d-end of the secondary winding N2 is W2, and the voltage of the first power supply side P1 When Vdc1, the voltage of the second power supply side P2 is Vdc2, when Vdc1/W1>Vdc2/W2, energy is transferred from the first power supply side P1 to the second power supply side P2, and when Vdc1/W1<Vdc2/W2 The energy is transmitted from the second power source side P2 to the first power source side P1.

The basic working principle of the bidirectional DC/DC converter 1 is to control the circuit design on both sides of the transformer 10 to achieve bidirectional flow of current, and to re-use the resonance to limit the current during each energy transfer. When the energy transfer direction is determined, it is also possible to select only the switching element on the transformer 10 side to be controlled, while the other side of the switching element maintains the off state, and only the natural on current of the diode exists. For example, if you determine that energy is from The first power supply side P1 is transmitted to the second power supply side P2, and based on the above working principle, only the first switching elements 111, 112, 113, 114 need to be controlled, and the second switching elements 115, 116, 117, 118 are The changeover switches S5, S6, S7, and S8 may be maintained in an off state.

4 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention. Please refer to Figure 4. The bidirectional DC/DC converter 4 is designed based on an LCC resonant circuit including a first inductor 43, a second capacitor 44 and a first capacitor 45, wherein the first inductor 43 is connected in series with the second capacitor 44. The bidirectional DC/DC converter 4 further includes a two full bridge circuit composed of first and second switching elements 411, 412, 413, 414, 415, 416, 417, 418 and a transformer 40.

Referring to FIG. 4, the primary side winding N1 and the secondary side winding N2 of the bidirectional DC/DC converter 4 are respectively connected to a first conversion circuit 41 and a second conversion circuit 42, wherein the first conversion circuit 41 is coupled to a first The power supply side P1 and the second conversion circuit 42 are coupled to a second power supply side P2. The first power supply side P1 is coupled to a full bridge circuit composed of the first switching elements 411, 412, 413, and 414, and the full bridge circuit is coupled to the primary side winding N1 of the transformer 40; the second power supply side P2 is coupled to a full bridge circuit composed of second switching elements 415, 416, 417, and 418 through a first capacitor 45, and the full bridge circuit is coupled to the transformer 40 through a first inductor 43 and a second capacitor 44. The secondary side winding N2.

As described above, the circuit operation of the bidirectional DC/DC converter of the present invention can be divided into four stages, and the current flow direction of the circuit can be distinguished into two cases, "transmission from the first power supply side to the second power supply side" and " Passed from the second power source side to the first power source side.

Similarly, in the operation principle of the bidirectional DC/DC converter 1 shown in FIG. 1, in the first phase, the first and second switching elements 411, 414, 415, 418 are turned on, the first and second switching elements 412, 413, 416, 417 deadline. When the current flow is transmitted from the first power supply side P1 to the second power supply side P2, the energy is transmitted from the first power supply side P1 to the first The power source side P2, on the other hand, when the current flow is transmitted from the second power source side P2 to the first power source side P1, the energy is transmitted from the second power source side P2 to the first power source side P1.

Since the on-times of the switching switches S1 and S4 of the first switching elements 411 and 414 and the resonance period of the first inductor 43 and the first capacitor 44 are the same, when the switching switches S1 and S4 of the first switching elements 411 and 414 are turned on, The current limiting action of the first inductor 43 has a very small current value. Similarly, since the on-times of the diodes D1, D4 of the first switching elements 411, 414 are exactly equal to the resonance period, the switching switches S1, S4 of the first switching elements 411, 414 are turned off and the dipoles D1, D4 are inverted. When turned on, the current resonates to a value of zero or a small current value close to zero, so that the circuit current values of the switching switches S1, S4 of the first switching elements 411, 414 are both turned on and off, whereby the first switching elements 411, 414 The energy loss is also small.

Of course, when the switching switches S1, S4 of the first switching elements 411, 414 are turned on, the switching switches S5, S8 of the second switching elements 415, 418 are turned off, whereby the first switching circuit 41 is charged, and the second switching circuit 42 is discharged. Similarly, when the switching switches S1, S4 of the first switching elements 411, 414 are turned off, the switching switches S5, S8 of the second switching elements 415, 418 are turned on, whereby the first switching circuit 41 is discharged, and the second switching circuit 42 is charged. Therefore, the present invention realizes bidirectional current transmission by controlling the first conversion circuit 41 and the second conversion circuit 42 on both sides of the transformer 40.

In phase two, all of the first and second switching elements 411, 412, 413, 414, 415, 416, 417, 418 are turned off. There is no energy transfer on either side of the transformer 40. If the transformer 40 is considered to be an ideal transformer, no current flows through the transformer 40.

In phase three, the first and second switching elements 412, 413, 416, 417 are turned on, and the first and second switching elements 411, 414, 415, 418 are turned off. When the current flow is transmitted from the first power supply side P1 to the second power supply side P2, the energy is transmitted from the first power supply side P1 to the second power supply side P2, and conversely, when the current flow is transmitted from the second power supply side P2 to the first On a power supply side P1, energy is transferred from the second power supply side P2 to the first power supply Side P1.

Similarly to the phase, since the on-time of the switching switches S3, S2 of the first switching elements 413, 412 and the resonance period of the first inductor 43 and the first capacitor 44 are the same, the switching switch S3 of the first switching elements 413, 412, When S2 is turned on, the current value is extremely small due to the current limiting action of the first inductor 43. Similarly, since the on-times of the diodes D3, D2 of the first switching elements 413, 412 are exactly equal to the resonance period, the switching switches S3, S2 of the first switching elements 413, 412 are turned off and the diodes D3, D2 are inverted. When conducting, the current resonates to a value of zero or a small current value close to zero, so that the circuit current values of the switching switches S3, S2 of the first switching elements 413, 412 are both turned on and off, whereby the first switching elements 413, 412 The energy loss is also small.

Of course, when the switching switches S3, S2 of the first switching elements 413, 412 are turned on, the switching switches S6, S7 of the second switching elements 416, 417 are turned off, whereby the first switching circuit 41 is charged, and the second switching circuit 42 is discharged. Similarly, when the changeover switches S3 and S2 of the first switching elements 413 and 412 are turned off, the changeover switches S6 and S7 of the second switching elements 416 and 417 are turned on, whereby the first conversion circuit 41 is discharged, and the second conversion circuit 42 is charged. Therefore, the present invention realizes bidirectional current transmission by controlling the first conversion circuit 41 and the second conversion circuit 42 on both sides of the transformer 40.

Phase 4 works in the same way as Phase 2, and after Phase 4 ends, the circuit work will loop back to Phase 1, and so on.

In summary, referring to FIG. 4, the bidirectional DC/DC converter 4 is based on the voltage relationship between the first power supply side P1 and the second power supply side P2 to automatically realize energy transfer. Assume that the number of turns of the end point to the end point of the transformer 40 is W1, the number of turns of the c end point to the d end point is W2, the voltage of the first power supply side P1 is Vdc1, and the voltage of the second power supply side P2 is Vdc2, Then, when Vdc1/W1>Vdc2/W2, energy is transferred from the first power supply side P1 to the second power supply side P2, and when Vdc1/W1<Vdc2/W2, energy is transferred from the second power supply side P2 to the first power supply. Side P1.

The basic operating principle of the bidirectional DC/DC converter 4 is to control the circuit design on both sides of the transformer 40 to achieve bidirectional flow of current, and to re-use the resonance to limit the current during each energy transfer. When determining the direction of energy transfer, it is also possible to select only the switching element on the side of the transformer 40 to be controlled, while the switching element on the other side maintains the off state, and only the natural on-current of the diode exists. For example, if it is determined that energy is transmitted from the second power source side P2 to the first power source side P1, based on the above operation principle, only the second switching elements 415, 416, 417, 418 need to be controlled, and the first switching element 411 is to be controlled. The switches S1, S2, S3, and S4 of 412, 413, and 414 may be maintained in an off state.

In summary, the bidirectional DC/DC converter of the present invention is designed based on an LCL resonant circuit or an LCC resonant circuit, and is designed to realize a bidirectional transmission of energy through a circuit design that controls both sides of the transformer.

Figure 5 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention. Please refer to Figure 5. The bidirectional DC/DC converter 5 is based on an LCL resonant circuit design including a first inductor 53, a second inductor 55 and a first capacitor 54. The bidirectional DC/DC converter 5 further includes a half bridge circuit composed of the first switching elements 513, 514 and the capacitors 511, 512 and a push-pull circuit composed of the second switching elements 515, 516 and a transformer 50. .

Referring to FIG. 5, the primary side winding N1 and the secondary side winding N2 of the bidirectional DC/DC converter 5 are respectively connected to a first conversion circuit 51 and a second conversion circuit 52, wherein the first conversion circuit 51 is coupled to a first The power supply side P1 and the second conversion circuit 52 are coupled to a second power supply side P2. The first conversion circuit 51 is a half bridge circuit composed of first switching elements 513, 514 and capacitors 511, 512, and the half bridge circuit is coupled to the primary side winding N1 of the transformer 50; the second power supply side P2 A push-pull circuit composed of second switching elements 515 and 516 is coupled to the first capacitor 54 via the first inductor 53 and the second inductor 55, and the push-pull circuit is coupled to the other side of the transformer 50. .

In detail, the first inductor 53 is coupled between the e-terminal end of the secondary winding N2 of the transformer 50 and the second inductor 55, and the second switching element 515 is coupled to the c-end of the secondary winding N2 of the transformer 50. Between the first capacitors 54, the second switching element 516 is coupled between the d-end of the secondary winding N2 of the transformer 50 and the first capacitor 54. In the first stage of operation of the bidirectional DC/DC converter 5, the capacitor 512 and the first switching element 513 are in an on state, and the first switching element 514 of the capacitor 511 is in an off state, and in the third stage, the capacitor 511 and the first switching element 514. In the on state, the capacitor 512 and the first switching element 513 are in an off state, and the rest are the same, and will not be described herein.

Figure 6 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention. Please refer to Figure 6. The bidirectional DC/DC converter 6 is based on an LCL resonant circuit design including a first inductor 63, a second capacitor 64, 65 and a second inductor 66. The bidirectional DC/DC converter 6 further includes a push-pull circuit composed of the first switching elements 611, 612 and a half bridge circuit composed of the second switching elements 613, 614 and a transformer 60.

Referring to FIG. 6, the primary side winding N1 and the secondary side winding N2 of the bidirectional DC/DC converter 6 are respectively connected to the first conversion circuit 61 and the second conversion circuit 62, wherein the first conversion circuit 61 is coupled to a first power supply side. P1, and the second conversion circuit 62 is coupled to a second power supply side P2. The positive terminal of the first power supply side P1 is coupled to the e-terminal end of the primary winding N1 of the transformer 60. The first switching element 611 is coupled to the c-terminal end of the primary winding N1 of the transformer 60 and the negative terminal of the first power supply side P1. The first switching element 612 is coupled between the end point of the primary side winding N1 of the transformer 60 and the negative terminal of the first power supply side P1, thereby forming a push-pull circuit; the positive terminal of the second power supply side P2 is transmitted through The second inductor 66 is coupled to the second switching circuit 62, the second switching element 613, 614 and the capacitor 64, 65, and the half bridge circuit is coupled to the transformer 60 through the first inductor 63. The secondary side winding N2. Bidirectional DC Phase 1 of the DC/DC converter 6 is active, the first and second switching elements 611, 614 are in an on state, the first and second switching elements 612, 613 are in an off state, and in phase three, the first and second switching elements 612 and 613 are in an on state, and the first and second switching elements 611 and 614 are in an off state, and the rest are the same, and will not be described herein.

Figure 7 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention. Please refer to Figure 7. The bidirectional DC/DC converter 7 is designed based on an LCC resonant circuit including a first inductor 73, first capacitors 75, 76 and a second capacitor 74. The bidirectional DC/DC converter 7 further includes a push-pull circuit composed of the first switching elements 711, 712 and a half bridge circuit composed of the second switching elements 713, 714 and the capacitors 75, 76 and a transformer 70. .

Referring to FIG. 7, the primary side winding N1 and the secondary side winding N2 of the bidirectional DC/DC converter 7 are respectively connected to a first conversion circuit 71 and a second conversion circuit 72, wherein the first conversion circuit 71 is coupled to a first The power supply side P1 and the second conversion circuit 72 are coupled to a second power supply side P2. The positive terminal of the first power supply side P1 is coupled to the e-terminal end of the primary side winding N1 of the transformer 70, and the first switching element 711 is coupled to the c-terminal end of the primary side winding N1 of the transformer 70 and the negative terminal of the first power supply side P1. The first switching element 712 is coupled between the end point of the primary side winding N1 of the transformer 70 and the negative terminal of the first power supply side P1, thereby forming a push-pull circuit; the positive terminal of the second power supply side P2 is transmitted through The capacitors 75 and 76 are coupled to the second switching circuit 72, the second switching elements 713, 714 and the half bridge circuit composed of the capacitors 75 and 76, and the half bridge circuit transmits the first inductor 73 and the second capacitor 74. It is coupled to the secondary side winding N2 of the transformer 70. In the first phase of operation of the bidirectional DC/DC converter 7, the first and second switching elements 711, 714 are in an on state, and the first and second switching elements 712, 713 are in an off state, and in phase three, first and The two switching elements 712 and 713 are in an on state, and the first and second switching elements 711 and 714 are in an off state.

As described above, the circuit on both sides of the transformer in the bidirectional DC/DC converter of the present invention can be applied to a full bridge circuit, a half bridge circuit or a push-pull circuit, and the applicable combinations thereof are as follows:

It can be seen that the bidirectional DC/DC converter of the present invention automatically realizes energy transfer according to the voltage relationship of the power source connected at both ends of the circuit. Assume that the number of turns of the transformer on one side of the transformer is W1, and the power supply voltage of the side is Vdc1, the number of turns of the other side is W2, and the power supply voltage of the side is Vdc2, then when Vdc1/W1>Vdc2/W2 When the energy is transmitted from the power supply side of the power supply voltage Vdc1 When the power supply voltage is Vdc2 on the power supply side, and when Vdc1/W1 <Vdc2/W2, the energy is transmitted from the power supply side where the power supply voltage is Vdc2 to the power supply side where the power supply voltage is Vdc1.

In summary, the present invention is based on an LCL resonant circuit or an LCC resonant circuit designed to control the two-way transmission of energy by controlling the first and second switching circuits on both sides of the transformer, while enabling the first and second conversions. The on-time of the switching switch of each switching element in the circuit and the first inductance of the resonant circuit are coincident with the resonant period of the first capacitor, so that when the switching switch is turned on, the current value is due to the current limiting action of the first inductor in the resonant circuit. Very small, similarly, when the switch is turned off, the current resonates to a value of zero or a small value close to zero. As a result, the circuit current value is small when the switch is turned on and off, and the energy loss of the switch is small. Improve circuit efficiency.

In addition, although the basic working principle of the bidirectional DC/DC converter of the present invention is to control the circuit design on both sides of the transformer to realize bidirectional flow of current and reuse resonance to limit the current during each energy transfer. However, when determining the direction of energy transfer, it is also possible to choose to apply control only to the switching elements on the side of the transformer, while the switching elements on the other side remain in the off state, and only the natural on-current of the diode exists.

1, 2, 3, 4, 5, 6, 7‧‧‧ bidirectional DC/DC converters

10, 20, 30, 40, 50, 60, 70‧‧‧ transformers

11, 21, 31, 41, 51, 61, 71‧‧‧ first conversion circuit

12, 22, 32, 42, 52, 62, 72‧‧‧ second conversion circuit

13, 23, 33, 43, 53, 63, 73‧‧‧ first inductance

15, 25, 35, 55, 66‧‧‧ second inductance

14, 24, 34, 45, 54, 64, 65, 75, 76‧‧‧ first capacitor

44, 74‧‧‧ second capacitor

111, 112, 113, 114, 211, 212, 213, 214, 311, 312, 313, 314, 411, 412, 413, 414, 513, 514, 611, 612 ‧ ‧ first switching element

115,116,117,118,215,216,217,218,315,316,317,318,415,416,417,418,515,516,613,614,711,712,713, 714‧‧ Second switching element

511, 512‧‧‧ capacitor

a, b, c, d, e‧‧‧ endpoints

P1‧‧‧ first power side

P2‧‧‧second power side

N1‧‧‧ primary winding

N2‧‧‧ secondary winding

S1, S2, S3, S4, S5, S6, S7, S8‧‧‧ switch

D1, D2, D3, D4, D5, D6, D7, D8‧‧‧ diodes

1 is a circuit diagram of a bidirectional DC/DC converter according to an embodiment of the present invention; FIG. 2A is a schematic diagram of operation of the bidirectional DC/DC converter of the present invention; and FIG. 2B is a description of operation of the bidirectional DC/DC converter of the present invention. 3A is a schematic diagram showing the operation of the bidirectional DC/DC converter of the present invention; and FIG. 3B is a schematic diagram of the operation of the bidirectional DC/DC converter of the present invention. Figure 4 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention; Figure 5 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention; and Figure 6 is a bidirectional diagram of another embodiment of the present invention; Circuit diagram of a DC/DC converter; Fig. 7 is a circuit diagram of a bidirectional DC/DC converter according to another embodiment of the present invention.

1‧‧‧Bidirectional DC/DC converter

10‧‧‧Transformers

11‧‧‧First conversion circuit

12‧‧‧Second conversion circuit

13‧‧‧First inductance

14‧‧‧first capacitor

15‧‧‧second inductance

111, 112, 113, 114‧‧‧ first switching element

115, 116, 117, 118‧‧‧ second switching element

a, b, c, d‧‧‧ endpoints

P1‧‧‧ first power side

P2‧‧‧second power side

N1‧‧‧ primary winding

N2‧‧‧ secondary winding

S1, S2, S3, S4, S5, S6, S7, S8‧‧‧ switch

D1, D2, D3, D4, D5, D6, D7, D8‧‧‧ diodes

Claims (14)

A bidirectional DC/DC converter coupled between a first power supply side and a second power supply side, comprising: a transformer having a primary side winding and a secondary side winding corresponding to magnetic coupling; and a first conversion circuit, a plurality of first switching elements, each of the first switching elements includes a switching switch and a diode connected in parallel with the switching switch, each of the first switching elements being coupled to the primary winding of the transformer; and a second switching circuit a plurality of second switching elements, each of the second switching elements including a switching switch and a diode connected in parallel with the switching switch, each of the second switching elements being coupled to a secondary winding of the transformer; and a resonance The circuit has a first inductor, at least a first capacitor and a second inductor, the first inductor is connected in series with the secondary winding of the transformer, and the at least one first capacitor is connected to the second converter circuit, the second An inductive coupling is coupled between the second power supply side and the second conversion circuit; wherein a current is transmitted from the first power supply side to the second power supply side, and at least one of the first switching elements is switched Passing, the first switching circuit is discharged, and the diodes of at least one of the second switching elements are turned on to charge the second switching circuit, and at least one of the first switching elements is switched The conduction period is substantially the same as the resonance period of the first inductor and the at least one first capacitor; wherein current is transmitted from the second power source side to the first power source side, and at least one of the first switching elements Turning on the body, charging the first conversion circuit, transmitting through the transformer, switching switches of at least one of the second switching elements are turned on, discharging the second conversion circuit, and at least one of the first switching elements The conduction period of the body is substantially the same as the period in which the current resonance of the resonant circuit reaches a zero value or a value close to zero; When determining an energy transfer direction, selecting a switching switch application control for at least one of the first switching elements on one side of the transformer, and switching switches of at least one of the second switching elements on the other side maintaining an off state There is a natural conduction current of some of the diodes, or a switching switch control of at least one of the second switching elements on one side of the transformer is selected, and at least one of the first switching elements on the other side is selected. The switch of the person maintains an off state and there is a natural on current of some of the diodes. The bidirectional DC/DC converter of claim 1, wherein at least one of the second switching elements is turned on, and at least one of the second switching elements is turned off; When at least one of the switching elements of the first switching element is turned off and the parallel diode is turned on, at least one of the switching elements of the second switching elements is turned on. The bidirectional DC/DC converter of claim 1, wherein the first inductance is a leakage inductance of the transformer. The bidirectional DC/DC converter of claim 1, wherein the switching period of at least one of the first switching elements is substantially the same as the resonant period of the first inductor and the at least one first capacitor The current is limited by the first inductance of the resonant circuit to reduce power loss. The bidirectional DC/DC converter according to claim 1, wherein the number of turns of the primary winding of the transformer is W1, and the number of turns of the secondary winding of the transformer is W2, the first power side The voltage is Vdc1, the voltage on the second power supply side is Vdc2, and when Vdc1/W1>Vdc2/W2, energy is transmitted from the first power supply side to the second power supply side, and when Vdc1/W1<Vdc2/W2 Energy is transferred from the second power source side to the first power source side to automatically achieve energy transfer. The bidirectional DC/DC converter as described in claim 1 of the patent scope, The first conversion circuit is a full bridge circuit, a half bridge circuit or a push pull circuit. The bidirectional DC/DC converter of claim 1 or 6, wherein the second conversion circuit is a full bridge circuit, a half bridge circuit or a push-pull circuit. A bidirectional DC/DC converter coupled between a first power supply side and a second power supply side, comprising: a transformer having a primary side winding and a secondary side winding corresponding to magnetic coupling; and a first conversion circuit, a plurality of first switching elements, each of the first switching elements includes a switching switch and a diode connected in parallel with the switching switch, each of the first switching elements being coupled to the primary winding of the transformer; and a second switching circuit a plurality of second switching elements, each of the second switching elements including a switching switch and a diode connected in parallel with the switching switch, each of the second switching elements being coupled to a secondary winding of the transformer; and a resonance The circuit has a first inductor, at least one first capacitor and a second capacitor, the first inductor is connected in series with the secondary winding of the transformer, and the at least one first capacitor is connected to the second converter circuit, the second a capacitor is coupled between the first inductor and the second converter circuit; wherein a current is transmitted from the first power source side to the second power source side, and at least one of the first switching elements is turned on Discharging the first conversion circuit, transmitting through the transformer, at least one of the second switching elements is turned on, charging the second conversion circuit, and at least one of the first switching elements is switched The conduction period is substantially the same as the resonance period of the first inductor and the at least one first capacitor; wherein the current is transmitted from the second power source side to the first power source side, and at least one of the first switching elements is diode Turn on to make the first conversion circuit Charging, transmitting through the transformer, switching switches of at least one of the second switching elements are turned on to discharge the second switching circuit, and a conducting period of at least one of the first switching elements is substantially the same as the resonant period The current resonance of the circuit reaches a zero value or a period close to zero; when determining the energy transfer direction, the switching switch of at least one of the first switching elements on one side of the transformer is selected to be applied, and the other side is At least one of the switching elements of the second switching elements maintains an off state and has a natural conduction current of some of the diodes, or selects switching of at least one of the second switching elements on one side of the transformer The switch applies control, and the switching switch of at least one of the first switching elements on the other side maintains an off state and there is a natural conduction current of some of the diodes. The bidirectional DC/DC converter of claim 8, wherein at least one of the second switching elements is turned on, and at least one of the second switching elements is turned off; When at least one of the switching elements of the first switching element is turned off and the parallel diode is turned on, at least one of the switching elements of the second switching elements is turned on. The bidirectional DC/DC converter of claim 8, wherein the first inductance is a leakage inductance of the transformer. The bidirectional DC/DC converter of claim 8, wherein the switching period of at least one of the first switching elements is substantially the same as the resonant period of the first inductor and the at least one first capacitor The current is limited by the first inductance of the resonant circuit to reduce power loss. The bidirectional DC/DC converter according to claim 8, wherein the number of turns of the primary winding of the transformer is W1, and the number of turns of the secondary winding of the transformer is W2, the first power side The voltage is Vdc1, and the voltage on the second power supply side is Vdc2, when Vdc1/W1>Vdc2/W2 The energy is transmitted from the first power source side to the second power source side, and when Vdc1/W1 < Vdc2/W2, energy is transmitted from the second power source side to the first power source side to automatically realize energy transfer. The bidirectional DC/DC converter of claim 8, wherein the first conversion circuit is a full bridge circuit, a half bridge circuit or a push-pull circuit. The bidirectional DC/DC converter of claim 8 or 13, wherein the second conversion circuit is a full bridge circuit, a half bridge circuit or a push-pull circuit.