Control Circuit and Method Applicable to Bidirectional DC Converter

Abstract

The present invention provides a control circuit and method applicable to a bidirectional DC converter. The bidirectional DC converter is applied to a vehicle-mounted power supply system, receives an input voltage, and outputs an output voltage and an output current. The control circuit includes an adjustment module, an oscillator, a phase-shift controller, a primary-side drive circuit, and a secondary-side drive circuit. The adjustment module outputs an adjustment signal based on the output voltage, a reference voltage, the output current, and a reference current. The oscillator receives the adjustment signal and outputs a switching frequency and a first control signal. The phase-shift controller receives the switching frequency, obtains a phase-shift angle based on the input voltage and the output voltage, and outputs a second control signal according to the switching frequency and the phase-shift angle. The primary-side drive circuit and the secondary-side drive circuit are respectively connected to the primary-side circuit and the secondary-side circuit, and drive the primary-side circuit and the secondary-side circuit of the bidirectional DC converter according to the control signal.

Description

Technical Field

[0001] The present invention relates to a control circuit and method, and in particular to a control circuit and method suitable for a bidirectional direct current converter. Background Art

[0002] On-board chargers are essential components for electric vehicles, and traditionally have been defined based on a single charging function. With the continuous development of microgrid technology, the diversification of user experience needs, and the continuous increase in on-board battery capacity, chargers with discharge functions have gradually attracted attention. To achieve bidirectional charging and discharging functions, Figure 1 , Figure 2 or Figure 3 The circuit structure shown in Figure 1 is as follows. Figure 1 The circuit structure shown in the figure is based on the original isolated charger, and an additional isolated inverter with discharge function is added. However, it is larger in size and has a higher cost. Figure 2 The circuit structure shown in the figure adopts a non-isolated bidirectional AC / DC converter, which has a simple structure and a small size. However, due to the lack of post-stage isolation measures, it is easy to leak electricity and endanger personal safety. Figure 3 The circuit structure shown adopts a non-isolated bidirectional AC / DC converter and an isolated bidirectional DC / DC converter connected to each other, and uses the bidirectional DC / DC converter to adjust the output voltage and meet the needs of bidirectional energy flow. While achieving bidirectional isolation, the size and cost are relatively ideal.

[0003] It can be seen that bidirectional DC / DC converter is an important part of developing bidirectional on-board charger. Bidirectional DC / DC converters in the prior art mostly use DAB (Dual Active Bridge) circuit or CLLC circuit. The DAB circuit controls the gain of the output voltage by phase shifting the primary and secondary drive signals. However, its soft switching range is limited, and the switching loss is large under most gain conditions, resulting in poor efficiency. The CLLC circuit is designed for the resonant circuit and adopts frequency modulation control. It has good efficiency when controlling the converter for charging. However, when controlling the converter for discharging, the resonant current has more reactive components, and the conduction loss of the switch increases, resulting in lower efficiency.

[0004] Therefore, it is an urgent need to develop a control circuit and method for a bidirectional DC converter that can improve the above-mentioned prior art. Summary of the invention

[0005] The purpose of the present disclosure is to provide a control circuit and method suitable for a bidirectional DC converter, wherein the regulating module generates a regulating signal according to the output voltage, the reference voltage, the output current and the reference current, outputs a control signal through the oscillator, and the phase shift controller generates another control signal according to the corresponding switching frequency and the input and output voltages, so that the driving circuit controls the switch tubes of the primary and secondary circuits of the bidirectional DC converter according to the control signal. Therefore, the control circuit and method of the present disclosure utilize frequency modulation and / or phase shift to control the bidirectional DC converter, which can meet the requirements of a wide range of voltage gain, and because it has a resonant element, it can realize soft switching, effectively reduce switching losses and improve system efficiency.

[0006] To achieve the above-mentioned purpose, the present disclosure provides a control circuit suitable for a bidirectional DC converter. The bidirectional DC converter is applied to an on-board power supply system and can switchably operate in a charging mode or a discharging mode. The bidirectional DC converter receives an input voltage and outputs an output voltage and an output current. The bidirectional DC converter includes a primary side, a primary circuit, a resonant cavity, a secondary circuit and a secondary side. The resonant cavity includes a transformer. The primary circuit is electrically connected between the primary side and the primary side of the resonant cavity, and the secondary circuit is electrically connected between the secondary side and the secondary side of the resonant cavity. The control circuit includes a regulating module, an oscillator, a phase shift controller, a primary side drive circuit and a secondary side drive circuit. The regulating module outputs a regulating signal according to the output voltage, the reference voltage, the output current and the reference current. The oscillator is connected to the regulating module to receive and output a switching frequency according to the regulating signal, and outputs a first control signal according to the switching frequency. The phase shift controller is connected to the oscillator to receive the switching frequency, obtain a phase shift angle according to the input voltage and the output voltage, and output a second control signal according to the switching frequency and the phase shift angle. The primary side driving circuit is connected to the primary side circuit, wherein when the bidirectional DC converter works in the charging mode, the primary side driving circuit receives and outputs the primary side driving signal to the primary side circuit according to the first control signal output by the oscillator, and when the bidirectional DC converter works in the discharging mode, the primary side driving circuit receives and outputs the primary side driving signal to the primary side circuit according to the second control signal output by the phase shift controller, so as to drive the operation of the primary side circuit. The secondary side driving circuit is connected to the secondary side circuit, wherein when the bidirectional DC converter works in the charging mode, the secondary side driving circuit receives and outputs the secondary side driving signal to the secondary side circuit according to the second control signal output by the phase shift controller, and when the bidirectional DC converter works in the discharging mode, the secondary side driving circuit receives and outputs the secondary side driving signal to the secondary side circuit according to the first control signal output by the oscillator, so as to drive the operation of the secondary side circuit.

[0007] To achieve the above-mentioned purpose, the present disclosure also provides a control method applicable to a bidirectional DC converter. The bidirectional DC converter is applied to an on-board power supply system and can switchably operate in a charging mode or a discharging mode. The bidirectional DC converter receives an input voltage and outputs an output voltage and an output current. The bidirectional DC converter includes a primary end, a primary circuit, a resonant cavity, a secondary circuit and a secondary end. The resonant cavity includes a transformer. The primary circuit is electrically connected between the primary end and the primary side of the resonant cavity, and the secondary circuit is electrically connected between the secondary end and the secondary side of the resonant cavity. The control method comprises the following steps: (a) using a regulating module to generate a regulating signal according to an output voltage, a reference voltage, an output current and a reference current; (b) using an oscillator to receive and generate a switching frequency according to the regulating signal, and to generate a first control signal according to the switching frequency; (c) using a phase shift controller to receive the switching frequency, and to obtain a phase shift angle according to an input voltage and an output voltage, and to generate a second control signal according to the switching frequency and the phase shift angle; (d) when the bidirectional DC converter operates in a charging mode, using a primary drive circuit to receive and generate a primary drive signal according to the first control signal, and when the bidirectional DC converter operates in a discharging mode, using a primary drive circuit to receive and generate a primary drive signal according to the second control signal to drive the operation of the primary circuit; and (e) when the bidirectional DC converter operates in a charging mode, using a secondary drive circuit to receive and generate a secondary drive signal according to the second control signal, and when the bidirectional DC converter operates in a discharging mode, using a secondary drive circuit to receive and generate a secondary drive signal according to the first control signal to drive the operation of the secondary circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] Figure 1 , Figure 2 and Figure 3 The schematic diagram of the circuit structure of the existing charger is shown in FIG.

[0009] Figure 4 and Figure 5 Schematic diagram of the circuit structure of a bidirectional DC converter and a control circuit according to a preferred embodiment of the present disclosure, wherein Figure 4 The bidirectional DC converter works in charging mode. Figure 5 The bidirectional DC converter works in discharge mode.

[0010] Figure 6 for Figure 4 A circuit structure diagram of another implementation of a bidirectional DC converter and a control circuit.

[0011] Figure 7 To display Figure 4 and Figure 5 A schematic diagram of the relationship between the phase shift angle, switching frequency and output voltage in a bidirectional DC converter and a control circuit.

[0012] Figure 8 for Figure 4 Switching timing diagram of the bidirectional DC converter when the output voltage gain is less than one.

[0013] Fig. 9A , Fig. 9B and Fig. 9C for Figure 4 Switching timing diagram of the bidirectional DC converter when the output voltage gain is greater than or equal to one.

[0014] Fig.10 for Figure 5 Switching timing diagram of the bidirectional DC converter when the output voltage gain is greater than or equal to one.

[0015] Fig.11A , Fig. 11B , Fig. 11C , Fig.11D , Fig.11E , Fig.11F , Fig.11G and Fig.11H for Figure 4 Schematic diagram of circuit structures of various implementations of the resonant cavity.

[0016] Fig.12 for Figure 4 Schematic diagram of the equivalent circuit structure of the resonant cavity.

[0017] Fig.13 The figure is a flow chart of a control method according to a preferred embodiment of the present disclosure.

[0018] Fig.14 for Fig.13 Flowchart of the sub-steps of the control method shown.

[0019] Fig.15 for Fig.13 A flow chart of another embodiment of the substeps of the control method is shown.

[0020] Explanation of symbols

[0021] 1: Bidirectional DC converter

[0022] 11: Original edge

[0023] 12: Primary circuit

[0024] 13: Resonant cavity

[0025] 13': Equivalent resonant cavity

[0026] 131: Transformer

[0027] Np: Number of turns on the primary side of the transformer

[0028] Ns: Number of turns on the secondary side of the transformer

[0029] 14: Secondary circuit

[0030] 15: Secondary side

[0031] 2: Control circuit

[0032] 21, 21': Adjustment module

[0033] 211, 211': First operator

[0034] 212, 212': Voltage loop regulator

[0035] 213, 213': Comparator

[0036] 214, 214': Second operator

[0037] 215, 215': Current loop regulator

[0038] 22: Oscillator

[0039] 23: Phase shift controller

[0040] 24: Primary side drive circuit

[0041] 25: Secondary side drive circuit

[0042] 26: Node voltage detection unit

[0043] 27: Resonant cavity detection unit

[0044] 281: Input voltage detection unit

[0045] 282: Output voltage detection unit

[0046] 283: Output current detection unit

[0047] 3: First terminal

[0048] 4: Second terminal

[0049] Vin: input voltage

[0050] Vo: output voltage

[0051] Vref: reference voltage

[0052] Io: output current

[0053] Iref: reference current

[0054] fs: switching frequency

[0055] Ip: primary side current

[0056] Is: secondary side current

[0057] Lrp: primary side inductance

[0058] Lrs: Secondary side inductance

[0059] Lr: resonant inductance

[0060] Crp: primary side capacitance

[0061] Crs: Secondary side capacitance

[0062] Cr: resonant capacitor

[0063] fr: resonant frequency

[0064] S1: The first switch

[0065] S2: The second switch

[0066] S3: The third switch

[0067] S4: The fourth switch

[0068] S5: The fifth switch

[0069] S6: The sixth switch

[0070] S7: The seventh switch

[0071] S8: The eighth switch

[0072] A: First Node

[0073] VA: voltage of the first node

[0074] B: Second node

[0075] VB: voltage of the second node

[0076] C, C': the third node

[0077] VC: voltage of the third node

[0078] D, D': the fourth node

[0079] VD: voltage of the fourth node

[0080] VC_D, VC'_D': voltage between the third node and the fourth node

[0081] S10, S20, S30, S40, S50, S11, S12, S13, S14, S15, S13', S14', S15': steps of the control method DETAILED DESCRIPTION

[0082] Some typical embodiments that embody the features and advantages of the present disclosure will be described in detail in the following description. It should be understood that the present disclosure can have various changes in different implementations without departing from the scope of the present disclosure, and the descriptions and illustrations therein are essentially used for illustrative purposes rather than for limiting the present disclosure.

[0083] Figure 4 and Figure 5 Schematic diagram of the circuit structure of a bidirectional DC converter and a control circuit according to a preferred embodiment of the present disclosure, wherein Figure 4 The bidirectional DC converter works in charging mode. Figure 5 The bidirectional DC converter works in the discharge mode. Figure 4 and Figure 5 As shown, the bidirectional DC converter 1 is mainly used in the vehicle power supply system, and can switchably operate in the charging mode or the discharging mode. The bidirectional DC converter 1 receives the input voltage Vin, and outputs the output voltage Vo and the output current Io, and includes a primary terminal 11, a primary circuit 12, a resonant cavity 13, a secondary circuit 14 and a secondary terminal 15. The resonant cavity 13 includes a transformer 131, the primary circuit 12 is electrically connected between the primary terminal 11 and the primary side of the resonant cavity 13, and the secondary circuit 14 is electrically connected between the secondary terminal 15 and the secondary side of the resonant cavity 13. The primary terminal 11 is connected to the first terminal 3, and the secondary terminal 15 is connected to the second terminal 4. When the bidirectional DC converter 1 operates in the charging mode, the first terminal 3 provides the input voltage Vin, and the second terminal 4 receives the output voltage Vo and the output current Io output by the bidirectional DC converter 1. When the bidirectional DC converter 1 operates in the discharging mode, the first terminal 3 receives the output voltage Vo and the output current Io output by the bidirectional DC converter 1, and the second terminal 4 provides the input voltage Vin. In some embodiments, the second terminal 4 is a vehicle-mounted battery, but is not limited thereto.

[0084] The control circuit 2 of the present disclosure is configured to control the bidirectional DC converter 1, and the control circuit 2 includes a regulating module 21, an oscillator 22, a phase shift controller 23, a primary drive circuit 24, and a secondary drive circuit 25. In some embodiments, the regulating module 21, the oscillator 22, and the phase shift controller 23 constitute a central controller.

[0085] The regulating module 21 outputs a regulating signal according to the output voltage Vo, the reference voltage Vref, the output current Io and the reference current Iref.

[0086] The oscillator 22 is connected to the regulating module 21 to receive and output a switching frequency fs according to the regulating signal, and output a first control signal according to the switching frequency fs. The oscillator 22 is preferably, but not limited to, a voltage-controlled oscillator.

[0087] The phase shift controller 23 is connected to the oscillator 22 to receive the switching frequency fs, and obtain a phase shift angle according to the input voltage Vin and the output voltage Vo, and output a second control signal according to the switching frequency fs and the phase shift angle, wherein the phase of the first control signal differs from the phase of the second control signal by the phase shift angle.

[0088] The primary drive circuit 24 is connected to the primary circuit 12 and is used to drive the operation of the primary circuit 12. The secondary drive circuit 25 is connected to the secondary circuit 14 and is used to drive the operation of the secondary circuit 14. When the bidirectional DC converter 1 operates in the charging mode, Figure 4 As shown, the primary drive circuit 24 is connected to the oscillator 22 to receive and output a primary drive signal to the primary circuit 12 according to a first control signal output by the oscillator 22. The secondary drive circuit 25 is connected to the phase shift controller 23 to receive and output a secondary drive signal to the secondary circuit 14 according to a second control signal output by the phase shift controller 23. When the bidirectional DC converter 1 operates in the discharge mode, as shown in FIG. Figure 5 As shown, the primary drive circuit 24 is connected to the phase shift controller 23 to receive and output the primary drive signal to the primary circuit 12 according to the second control signal output by the phase shift controller 23, and the secondary drive circuit 25 is connected to the oscillator 22 to receive and output the secondary drive signal to the secondary circuit 14 according to the first control signal output by the oscillator 22.

[0089] In this embodiment, the control circuit 2 adopts a nested control method of a voltage outer loop and a current inner loop. Figure 4 and Figure 5As shown, the regulating module 21 includes a first operator 211, a voltage loop regulator 212, a comparator 213, a second operator 214 and a current loop regulator 215, wherein the first operator 211 is connected to the voltage loop regulator 212, the comparator 213 is connected to the voltage loop regulator 212 and the second operator 214, and the current loop regulator 215 is connected to the second operator 214 and the oscillator 22. The first operator 211 outputs the difference between the output voltage Vo and the reference voltage Vref to the voltage loop regulator 212. The voltage loop regulator 212 adjusts the difference between the output voltage Vo and the reference voltage Vref, and outputs a voltage loop regulating signal to the comparator 213. The comparator 213 compares the voltage loop regulating signal with the reference current Iref, and outputs a signal to the second operator 214 according to the comparison result. In some embodiments, the signal output by the comparator 213 is a voltage loop adjustment signal or a reference current Iref, and the signal output by the comparator 213 may be, for example but not limited to, the smaller of the voltage loop adjustment signal and the reference current Iref. In the charging mode, the second operator 214 outputs the difference between the signal output by the comparator 213 and the output current Io to the current loop regulator 215. In the discharging mode, the second operator 214 outputs the difference between the signal output by the comparator 213 and the secondary side current Is to the current loop regulator 215. After the current loop regulator 215 adjusts the difference between the signal output by the comparator 213 and the output current Io, it outputs the adjustment signal to the oscillator 22, and the oscillator 22 converts the adjustment signal into frequency information for subsequent control actions.

[0090] Furthermore, in some other embodiments, the control circuit is changed to adopt a control method in which a voltage loop and a current loop are connected in parallel. Figure 6 for Figure 4 A circuit structure diagram of another embodiment of a bidirectional DC converter and a control circuit, wherein the bidirectional DC converter operates in a charging mode. Figure 4 Similar structures and components in the present invention are denoted by the same reference numerals, and thus will not be described in detail herein. Figure 6As shown, the regulating module 21' comprises a first operator 211', a voltage loop regulator 212', a second operator 214', a current loop regulator 215' and a comparator 213', wherein the first operator 211' is connected to the voltage loop regulator 212', the second operator 214' is connected to the current loop regulator 215', and the comparator 213' is connected to the current loop regulator 215', the voltage loop regulator 212' and the oscillator 22. The first operator 211' outputs the difference between the output voltage Vo and the reference voltage Vref to the voltage loop regulator 212'. The voltage loop regulator 212' adjusts the difference between the output voltage Vo and the reference voltage Vref, and outputs a voltage loop regulating signal to the comparator 213'. The second operator 214' outputs the difference between the output current Io and the reference current Iref to the current loop regulator 215'. After adjusting the difference between the output current Io and the reference current Iref, the current loop regulator 215' outputs a current loop regulation signal to the comparator 213'. The comparator 213' compares the voltage loop regulation signal and the current loop regulation signal, and outputs the regulation signal to the oscillator 22 according to the comparison result, so that the oscillator 22 converts the regulation signal into frequency information for subsequent control actions. In some embodiments, the regulation signal output by the comparator 213' is a voltage loop regulation signal or a current loop regulation signal, and the regulation signal output by the comparator 213' may be, for example but not limited to, the smaller of the voltage loop regulation signal and the current loop regulation signal.

[0091] In some embodiments, the primary circuit 12 of the bidirectional DC converter 1 includes a first bridge arm and a second bridge arm connected in parallel, wherein the first bridge arm includes a first switch tube S1 and a second switch tube S2 connected in series, and the second bridge arm includes a third switch tube S3 and a fourth switch tube S4 connected in series. A first node A is provided between the first switch tube S1 and the second switch tube S2, and the first node A is electrically connected to one end of the primary side of the resonant cavity 13. A second node B is provided between the third switch tube S3 and the fourth switch tube S4, and the second node B is electrically connected to the other end of the primary side of the resonant cavity 13. The secondary circuit 14 of the bidirectional DC converter 1 includes a third bridge arm and a fourth bridge arm connected in parallel, wherein the third bridge arm includes a fifth switch tube S5 and a sixth switch tube S6 connected in series, and the fourth bridge arm includes a seventh switch tube S7 and an eighth switch tube S8 connected in series. There is a third node C between the fifth switch tube S5 and the sixth switch tube S6, and the third node C is electrically connected to one end of the secondary side of the resonance cavity 13. There is a fourth node D between the seventh switch tube S7 and the eighth switch tube S8, and the fourth node D is electrically connected to the other end of the secondary side of the resonance cavity 13.

[0092] The primary side of the resonant cavity 13 has a primary side current Ip, and the secondary side of the resonant cavity 13 has a secondary side current Is. In order to control the switch tube to turn on or off when its current is zero to achieve soft switching, it is necessary to obtain the time point when the primary side current Ip and the secondary side current Is are zero. In some embodiments, Figure 4 and 5 As shown, the control circuit 2 further includes a resonant cavity detection unit 27, and the resonant cavity detection unit 27 is configured to detect the primary side current Ip and the secondary side current Is and provide them to the phase shift controller 23. In other embodiments, as Figure 6 As shown, the control circuit 2 further includes a node voltage detection unit 26, which is configured to detect the voltage VA of the first node A, the voltage VB of the second node B, the voltage VC of the third node C, and the voltage VD of the fourth node D, and provide them to the phase shift controller 23. When the bidirectional DC converter 1 operates in the charging mode, and the detected voltage VC of the third node C or the voltage VD of the fourth node D is at a falling edge, the primary side current Ip and the secondary side current Is are zero. When the bidirectional DC converter 1 operates in the discharging mode, and the detected voltage VA of the first node A or the voltage VB of the second node B is at a falling edge, the primary side current Ip and the secondary side current Is are zero.

[0093] Figure 7 To display Figure 4 and Figure 5 Schematic diagram of the relationship between the phase shift angle, switching frequency and output voltage in the bidirectional DC converter and control circuit. Figure 7 As shown, the solid line is the relationship curve between the switching frequency fs and the output voltage Vo under the constant input voltage Vin, and the dotted line is the relationship curve between the phase shift angle and the output voltage Vo. As the output voltage Vo increases, the output voltage gain of the bidirectional DC converter 1 also gradually increases, wherein when the switching frequency fs is at the minimum value, the output voltage gain of the bidirectional DC converter 1 is close to one, and the minimum value of the switching frequency fs is greater than the resonant frequency fr of the resonant cavity 13. When the output voltage gain of the bidirectional DC converter 1 is less than one, the switching frequency fs decreases with the increase of the output voltage Vo, and the phase shift angle is maintained at zero. When the output voltage gain of the bidirectional DC converter 1 is greater than one, the switching frequency fs and the phase shift angle both increase with the increase of the output voltage Vo. It can be seen from this that no matter the bidirectional DC converter 1 operates in the charging mode or the discharging mode, when the output voltage gain of the bidirectional DC converter 1 is less than one, the control circuit 2 performs frequency modulation control on the bidirectional DC converter 1, and when the output voltage gain of the bidirectional DC converter 1 is greater than or equal to one, the control circuit 2 performs frequency modulation and phase shift control on the bidirectional DC converter 1.

[0094] The control of the switch in the bidirectional DC converter 1 varies according to different conditions and requirements. Various control methods will be described below.

[0095] In some embodiments, regardless of the output voltage gain of the bidirectional DC converter 1, when the bidirectional DC converter 1 operates in the charging mode, the driving signal of the fifth switch tube S5, the driving signal of the sixth switch tube S6, the driving signal of the seventh switch tube S7, and the driving signal of the eighth switch tube S8 can all operate in the synchronous rectification mode, wherein the driving signal when the output voltage gain of the bidirectional DC converter 1 is less than one is as follows: Figure 8 As shown, when the output voltage gain of the bidirectional DC converter 1 is greater than or equal to one, the driving signal Fig. 9C As shown. The driving signal of the fifth switch tube S5 is turned on for a period of time when the voltage VC of the third node C is at a high level, the driving signal of the sixth switch tube S6 is turned on for a period of time when the voltage VC of the third node C is at a low level, the driving signal of the seventh switch tube S7 is turned on for a period of time when the voltage VD of the fourth node D is at a high level, and the driving signal of the eighth switch tube S8 is turned on for a period of time when the voltage VD of the fourth node D is at a low level. When the bidirectional DC converter 1 operates in the discharge mode, the driving signal of the first switch tube S1, the driving signal of the second switch tube S2, the driving signal of the third switch tube S3 and the driving signal of the fourth switch tube S4 can all operate in the synchronous rectification mode. The driving signal of the first switch tube S1 is turned on for a period of time when the voltage VA at the first node A is at a high level, the driving signal of the second switch tube S2 is turned on for a period of time when the voltage VA at the first node A is at a low level, the driving signal of the third switch tube S3 is turned on for a period of time when the voltage VB at the second node B is at a high level, and the driving signal of the fourth switch tube S4 is turned on for a period of time when the voltage VB at the second node B is at a low level.

[0096] When the output voltage gain of the bidirectional DC converter 1 is less than one, the control circuit 2 only performs frequency modulation control on the bidirectional DC converter 1 without performing phase shifting on the driving signals of each switch tube. Figure 8 for Figure 4 The switching timing diagram of the bidirectional DC converter when the output voltage gain is less than 1. Figure 8As shown, the control circuit 2 controls the bidirectional DC converter 1 by changing the switching frequency fs. In some embodiments, the switch tube of the secondary circuit 14 is controlled to work in the synchronous rectification state. Taking one cycle of the primary side current Ip change as an example, the time t1, t3 and t5 are the time points when the primary side current Ip is zero. The driving signals of the sixth switch tube S6 and the seventh switch tube S7 are turned on for a period of time from the time t1 to t3, and the driving signals of the fifth switch tube S5 and the eighth switch tube S8 are turned on for a period of time from the time t3 to t5. In other words, the time from the time t1 to t3 is the longest time for the sixth switch tube S6 and the seventh switch tube S7 to perform synchronous rectification, and the time from the time t3 to t5 is the longest time for the fifth switch tube S5 and the eighth switch tube S8 to perform synchronous rectification. Of course, in other embodiments, the switch tube of the secondary circuit 14 can also be controlled to work in the diode rectification state. Since the primary circuit 12 and the secondary circuit 14 of the bidirectional DC converter 1 are symmetrical to each other, the control method of the switch tube of the primary circuit 12 when the bidirectional DC converter 1 works in the discharge mode can be inferred by analogy with the above description, so it is not repeated here.

[0097] When the output voltage gain of the bidirectional DC converter 1 is greater than or equal to one, the control circuit 2 performs frequency modulation and phase shift control on the bidirectional DC converter 1 . Fig. 9A , 9B and 9C is Figure 4 The switching timing diagram of the bidirectional DC converter when the output voltage gain is greater than or equal to one. Fig. 9A and 9B In the embodiment, the bidirectional DC converter 1 works in the charging mode, the duty cycle of the driving signal is 50%, the control circuit 2 performs phase shift control on the sixth switch tube S6 and the eighth switch tube S8, and controls the fifth switch tube S5 and the seventh switch tube S7 to work in the diode rectification state or the synchronous rectification state, but the control method for each switch tube is different. Fig. 9A In the control mode shown, the control circuit 2 delays the turn-on time of the first switch tube S1 and the second switch tube S2 by a phase shift angle to obtain the turn-on time of the sixth switch tube S6 and the eighth switch tube S8 respectively, and controls the drive signals of the fifth switch tube S5 and the seventh switch tube S7 to maintain the off state, so that the fifth switch tube S5 and the seventh switch tube S7 work in the diode rectification state. Fig. 9B In the control method shown, the control circuit 2 delays the turn-on time of the first switch tube S1 and the second switch tube S2 by the phase shift angle to obtain the turn-on time of the sixth switch tube S6 and the eighth switch tube S8 respectively, and controls the drive signal of the fifth switch tube S5 to be turned on for a period of time between the turn-off time of the sixth switch tube S6 and the time when the primary side current Ip is zero, and controls the drive signal of the seventh switch tube S7 to be turned on for a period of time between the turn-off time of the eighth switch tube S8 and the time when the primary side current Ip is zero. Fig. 9C In the control mode shown, the control circuit 2 controls the drive signal of the fifth switch tube S5 to be turned on for a period of time during the time when the voltage VC of the third node C is at a high level, controls the drive signal of the sixth switch tube S6 to be turned on for a period of time during the time when the voltage VC of the third node C is at a low level, controls the drive signal of the fifth switch tube S5 to be turned on for a period of time between the turn-off moment of the sixth switch tube S6 and the moment when the primary side current Ip is zero, and controls the drive signal of the seventh switch tube S7 to be turned on for a period of time between the turn-off moment of the eighth switch tube S8 and the moment when the primary side current Ip is zero.

[0098] Fig.10 for Figure 5 The switching timing diagram of the bidirectional DC converter when the output voltage gain is greater than or equal to one. Fig.10 As shown, the bidirectional DC converter 1 works in the discharge mode, the duty cycle of the driving signal is 50%, and the control circuit 2 delays the turn-on time of the seventh switch tube S7 and the eighth switch tube S8 by the phase shift angle to obtain the turn-on time of the second switch tube S2 and the fourth switch tube S4, respectively, and controls the drive signals of the first switch tube S1 and the third switch tube S3 to maintain the off state, so that the first switch tube S1 and the third switch tube S3 work in the diode rectification state. Since the primary circuit 12 and the secondary circuit 14 of the bidirectional DC converter 1 are symmetrical to each other, and as shown in FIG. Fig. 9A and Fig.10 As shown, the control modes of the bidirectional DC converter 1 when operating in the charging mode and the discharging mode are also symmetrical to each other, so it can be obtained by Figure 8 , Fig. 9B and 9C The control method shown can be used to deduce the corresponding control method when the bidirectional DC converter 1 works in the discharge mode, which will not be described in detail here.

[0099] Of course, when the output voltage gain of the bidirectional DC converter 1 is greater than or equal to 1, the control method for the switch tube is not limited to Fig. 9A , Fig. 9B , Fig. 9C and Fig.10 The control method shown.

[0100] In some embodiments, the control circuit 2 performs phase shift control on the fifth switch tube S5 and the seventh switch tube S7, and controls the sixth switch tube S6 and the eighth switch tube S8 to operate in a diode rectification state or a synchronous rectification state. When the bidirectional DC converter 1 operates in a charging mode, the control circuit 2 delays the turn-on time of the first switch tube S1 and the second switch tube S2 by a phase shift angle to obtain the turn-on time of the seventh switch tube S7 and the fifth switch tube S5, respectively. The drive signal of the sixth switch tube S6 is turned on for a period of time or maintained in an off state between the turn-off time of the fifth switch tube S5 and the time when the primary side current Ip is zero. The drive signal of the eighth switch tube S8 is turned on for a period of time or maintained in an off state between the turn-off time of the seventh switch tube S7 and the time when the primary side current Ip is zero. When the bidirectional DC converter 1 operates in the discharge mode, the control circuit 2 delays the turn-on moments of the seventh switch tube S7 and the eighth switch tube S8 by the phase shift angle to obtain the turn-on moments of the first switch tube S1 and the third switch tube S3 respectively, the drive signal of the fourth switch tube S4 is turned on for a period of time or maintained in the off state between the turn-off moment of the third switch tube S3 and the moment when the secondary side current Is is zero, and the drive signal of the second switch tube S2 is turned on for a period of time or maintained in the off state between the turn-off moment of the first switch tube S1 and the moment when the secondary side current Is is zero.

[0101] In some other embodiments, the control circuit 2 performs phase shift control on the fifth switch tube S5 and the sixth switch tube S6, and controls the seventh switch tube S7 and the eighth switch tube S8 to operate in a diode rectification state or a synchronous rectification state. When the bidirectional DC converter 1 operates in a charging mode, the control circuit 2 delays the turn-on time of the second switch tube S2 by a phase shift angle to obtain the turn-on time of the fifth switch tube S5, the drive signal of the sixth switch tube S6 is complementary to the drive signal of the fifth switch tube S5, the drive signal of the seventh switch tube S7 is turned on for a period of time or maintained in an off state between the turn-off time of the fifth switch tube S5 and the time when the primary side current Ip is zero, the drive signal of the eighth switch tube S8 is turned on for a period of time or maintained in an off state between the turn-off time of the sixth switch tube S6 and the time when the primary side current Ip is zero, When the bidirectional DC converter 1 operates in the discharge mode, the control circuit 2 delays the turn-on time of the eighth switch tube S8 by the phase shift angle to obtain the turn-on time of the third switch tube S3, the drive signal of the fourth switch tube S4 is complementary to the drive signal of the third switch tube S3, the drive signal of the first switch tube S1 is turned on for a period of time or maintained in the off state between the turn-off time of the third switch tube S3 and the time when the secondary side current Is is zero, and the drive signal of the second switch tube S2 is turned on for a period of time or maintained in the off state between the turn-off time of the fourth switch tube S4 and the time when the secondary side current Is is zero.

[0102] In some other embodiments, the control circuit 2 performs phase shift control on the seventh switch tube S7 and the eighth switch tube S8, and controls the fifth switch tube S5 and the sixth switch tube S6 to operate in a diode rectification state or a synchronous rectification state. When the bidirectional DC converter 1 operates in a charging mode, the control circuit 2 delays the turn-on time of the first switch tube S1 by a phase shift angle to obtain the turn-on time of the seventh switch tube S7, the drive signal of the eighth switch tube S8 is complementary to the drive signal of the seventh switch tube S7, the drive signal of the fifth switch tube S5 is turned on for a period of time or maintained in an off state between the turn-off time of the seventh switch tube S7 and the time when the primary side current Ip is zero, and the drive signal of the sixth switch tube S6 is turned on for a period of time or maintained in an off state between the turn-off time of the eighth switch tube S8 and the time when the primary side current Ip is zero. When the bidirectional DC converter 1 operates in the discharge mode, the control circuit 2 delays the turn-on time of the seventh switch tube S7 by the phase shift angle to obtain the turn-on time of the first switch tube S1, the drive signal of the second switch tube S2 is complementary to the drive signal of the first switch tube S1, the drive signal of the third switch tube S3 is turned on for a period of time or maintained in the off state between the turn-off time of the first switch tube S1 and the time when the secondary side current Is is zero, and the drive signal of the fourth switch tube S4 is turned on for a period of time or maintained in the off state between the turn-off time of the second switch tube S2 and the time when the secondary side current Is is zero.

[0103] Please refer to Figure 4 In some embodiments, the control circuit 2 further includes an input voltage detection unit 281, an output voltage detection unit 282, and an output current detection unit 283. The input voltage detection unit 281 is configured to detect an input voltage Vin and provide it to the phase-shift controller 23. The output voltage detection unit 282 is configured to detect an output voltage Vo and provide it to the regulating modules 21, 21' and the phase-shift controller 23. The output current detection unit 283 is configured to detect an output current Io and provide it to the regulating modules 21, 21'.

[0104] In some embodiments, the resonant cavity 13 of the bidirectional DC converter 1 further includes a resonant element, such as Figure 4 As shown, the primary side of the resonant cavity 13 includes a resonant inductor Lr and a primary side capacitor Crp, and the secondary side of the resonant cavity 13 includes a secondary side capacitor Crs. In fact, the actual implementation of the resonant element of the resonant cavity 13 is not limited thereto. Fig.11A , Fig. 11B , Fig. 11C , Fig.11D , Fig.11E , Fig.11F , Fig.11G and Fig.11H for Figure 4 Schematic diagram of the circuit structure of various embodiments of the resonant cavity. Fig.11AIn the illustrated embodiment, the primary side of the resonant cavity 13 includes a primary side inductor Lrp and a primary side capacitor Crp, and the secondary side of the resonant cavity 13 includes a secondary side inductor Lrs and a secondary side capacitor Crs. Fig. 11B In the illustrated embodiment, the primary side of the resonant cavity 13 includes a primary side capacitor Crp, and the secondary side of the resonant cavity 13 includes a resonant inductor Lr and a secondary side capacitor Crs. Fig. 11C In the illustrated embodiment, the primary side of the resonant cavity 13 includes a primary side inductor Lrp and a resonant capacitor Cr, and the secondary side of the resonant cavity 13 includes a secondary side inductor Lrs. Fig.11D In the illustrated embodiment, the primary side of the resonant cavity 13 includes a primary side inductor Lrp, and the secondary side of the resonant cavity 13 includes a secondary side inductor Lrs and a resonant capacitor Cr. Fig.11E In the embodiment shown, the primary side of the resonant cavity 13 includes a resonant inductor Lr and a resonant capacitor Cr. Fig.11F In the embodiment shown, the secondary side of the resonant cavity 13 includes a resonant inductor Lr and a resonant capacitor Cr. Fig.11G In the illustrated embodiment, the primary side of the resonant cavity 13 includes a resonant inductor Lr, and the secondary side of the resonant cavity 13 includes a resonant capacitor Cr. Fig.11H In the illustrated embodiment, the primary side of the resonant cavity 13 includes a resonant capacitor Cr, and the secondary side of the resonant cavity includes a resonant inductor Lr.

[0105] In addition, the primary side inductance Lrp and the secondary side inductance Lrs are equivalent to the resonant inductance Lr, and their relationship satisfies equation (1). The primary side capacitance Crp and the secondary side capacitance Crs are equivalent to the resonant capacitance Cr, and their relationship satisfies equation (2).

[0106]

[0107]

[0108] Wherein, Np and Ns are the primary side turns and the secondary side turns of the transformer 131 respectively.

[0109] By using the resonant inductor Lr and the resonant capacitor Cr, the resonant frequency fr can be calculated by equation (3).

[0110]

[0111] Fig.12 for Figure 4 The possible implementation methods of the above-mentioned resonant cavity 13 can be equivalent to: Fig.12 The equivalent resonant cavity 13' shown is Fig.12As shown, the equivalent resonant cavity 13' includes a resonant inductor Lr and a resonant capacitor Cr, and as shown in equation (4), the voltage between the third node and the fourth node also changes accordingly.

[0112]

[0113] VC'_D' is the voltage between the third node C' and the fourth node D' when the resonant cavity 13 is equivalent to the resonant inductor Lr and the resonant capacitor Cr, and VC_D is the voltage between the third node C and the fourth node D when the resonant cavity 13 includes the transformer 131 and the resonant element.

[0114] Fig.13 This is a flow chart of a control method of a preferred embodiment of the present disclosure. The control method of this embodiment is applicable to Figure 4 and Figure 5 The bidirectional DC converter 1 and the control circuit 2 shown include the following steps:

[0115] First, the regulating modules 21 and 21 ′ are used to generate a regulating signal according to the output voltage Vo, the reference voltage Vref, the output current Io and the reference current Iref (as shown in step S10 ).

[0116] Next, the oscillator 22 is used to receive and generate a switching frequency fs according to the adjustment signal, and a first control signal is generated according to the switching frequency fs (as shown in step S20 ).

[0117] Next, the phase shift controller 23 receives the switching frequency fs, obtains a phase shift angle according to the input voltage Vin and the output voltage Vo, and generates a second control signal according to the switching frequency fs and the phase shift angle (as shown in step S30 ).

[0118] Next, when the bidirectional DC converter 1 operates in the charging mode, the primary driving circuit 24 is used to receive and generate a primary driving signal according to the first control signal. When the bidirectional DC converter 1 operates in the discharging mode, the primary driving circuit 24 is used to receive and generate a primary driving signal according to the second control signal to drive the operation of the primary circuit 12 (as shown in step S40). Any of the aforementioned control methods can be used to control the switch tube in the primary circuit 12.

[0119] Finally, when the bidirectional DC converter 1 operates in the charging mode, the secondary side driving circuit 25 is used to receive and generate a secondary side driving signal according to the second control signal. When the bidirectional DC converter 1 operates in the discharging mode, the secondary side driving circuit 25 is used to receive and generate a secondary side driving signal according to the first control signal to drive the operation of the secondary circuit 14 (as shown in step S50), wherein any of the aforementioned switch tube control methods can be used to control the switch tube in the secondary circuit 14.

[0120] Fig.14 for Fig.13 Flow chart of the sub-steps of the control method shown in FIG. Fig.14 As shown, step S10 of the control method further includes the following sub-steps:

[0121] Utilizing the first operator 211, 211' to generate a difference between the output voltage Vo and the reference voltage Vref according to the output voltage Vo and the reference voltage Vref (as shown in step S11);

[0122] The voltage loop regulators 212 and 212' generate a voltage loop regulating signal according to the difference between the output voltage Vo and the reference voltage Vref (as shown in step S12);

[0123] The comparator 213 receives and compares the voltage loop adjustment signal and the reference current Iref, and generates a signal according to the comparison result (as shown in step S13), wherein the signal output by the comparator 213 is the voltage loop adjustment signal or the reference current Iref;

[0124] Utilizing the second operator 214 to generate a difference between the signal and the output current Io according to the signal and the output current Io (as shown in step S14); and

[0125] The current loop regulator 215 is used to generate a regulating signal according to the difference between the signal and the output current Io (as shown in step S15 ).

[0126] Fig.15 for Fig.13 A flowchart of another embodiment of the sub-steps of the control method shown in FIG. Fig.14 Similar steps in the above are indicated by the same reference numerals and will not be described again here. Fig.14 The sub-steps of step S10 shown are as follows: Fig.15 As shown, step S10 of the control method is changed to include sub-steps S11, S12 and the following sub-steps:

[0127] Utilize the second operator 214' to generate a difference between the output current Io and the reference current Iref according to the output current Io and the reference current Iref (as shown in step S13');

[0128] Utilize the current loop regulator 215' to generate a current loop regulation signal according to the difference between the output current Io and the reference current Iref (as shown in step S14'); and

[0129] The comparator 213 ′ is used to receive and compare the voltage loop regulating signal and the current loop regulating signal, and a regulating signal is generated according to the comparison result (as shown in step S15 ′), wherein the generated regulating signal is the voltage loop regulating signal or the current loop regulating signal.

[0130] In summary, the present disclosure provides a control circuit and method suitable for a bidirectional DC converter, wherein the regulating module generates a regulating signal according to the output voltage, the reference voltage, the output current and the reference current, outputs a control signal through the oscillator, and the phase shift controller generates another control signal according to the corresponding switching frequency and the input and output voltages, so that the driving circuit controls the switch tubes of the primary and secondary circuits of the bidirectional DC converter according to the control signal. Therefore, the control circuit and method of the present disclosure utilizes frequency modulation and / or phase shifting to control the bidirectional DC converter, which can meet the requirements of a wide range of voltage gain, and because it has a resonant element, it can realize soft switching, effectively reduce switching losses and improve system efficiency.

[0131] It should be noted that the above are only preferred embodiments for illustrating the present disclosure, and the present disclosure is not limited to the embodiments described, and the scope of the present disclosure is determined by the claims. In addition, the present disclosure can be modified in various ways by those skilled in the art, but they do not deviate from the scope of protection of the claims.

Claims

1. A control circuit is applicable to a bidirectional DC converter. The bidirectional DC converter is applied to a vehicle power supply system and can operate switchably in a charging mode or a discharging mode. The bidirectional DC converter receives an input voltage and outputs an output voltage and an output current. The bidirectional DC converter includes a primary side, a primary circuit, a resonant cavity, a secondary circuit, and a secondary side. The resonant cavity includes a transformer. The primary circuit is electrically connected between the primary side and a primary side of the resonant cavity. The secondary circuit is electrically connected between the secondary side and a secondary side of the resonant cavity. The control circuit includes: An adjustment module that outputs an adjustment signal based on the output voltage, a reference voltage, the output current, and a reference current; An oscillator connected to the adjustment module to receive and output a switching frequency based on the adjustment signal, and output a first control signal based on the switching frequency; A phase-shift controller connected to the oscillator to receive the switching frequency, obtain a phase-shift angle based on the input voltage and the output voltage, and output a second control signal based on the switching frequency and the phase-shift angle; A primary-side drive circuit connected to the primary circuit. When the bidirectional DC converter operates in the charging mode, the primary-side drive circuit receives and outputs a primary-side drive signal to the primary circuit based on the first control signal output by the oscillator. When the bidirectional DC converter operates in the discharging mode, the primary-side drive circuit receives and outputs the primary-side drive signal to the primary circuit based on the second control signal output by the phase-shift controller to drive the operation of the primary circuit; And A secondary-side drive circuit connected to the secondary circuit. When the bidirectional DC converter operates in the charging mode, the secondary-side drive circuit receives and outputs a secondary-side drive signal to the secondary circuit based on the second control signal output by the phase-shift controller. When the bidirectional DC converter operates in the discharging mode, the secondary-side drive circuit receives and outputs the secondary-side drive signal to the secondary circuit based on the first control signal output by the oscillator to drive the operation of the secondary circuit. The primary circuit of the bidirectional DC converter includes a first bridge arm and a second bridge arm connected in parallel. The first bridge arm includes a first switch tube and a second switch tube connected in series. The second bridge arm includes a third switch tube and a fourth switch tube connected in series. There is a first node between the first switch tube and the second switch tube, and this first node is electrically connected to one end of the primary side. There is a second node between the third switch tube and the fourth switch tube, and this second node is electrically connected to the other end of the primary side. The secondary circuit of the bidirectional DC converter includes a third bridge arm and a fourth bridge arm connected in parallel. The third bridge arm includes a fifth switch tube and a sixth switch tube connected in series. The fourth bridge arm includes a seventh switch tube and an eighth switch tube connected in series. There is a third node between the fifth switch tube and the sixth switch tube, and this third node is electrically connected to one end of the secondary side. There is a fourth node between the seventh switch tube and the eighth switch tube, and this fourth node is electrically connected to the other end of the secondary side. There is a primary side current on the primary side of the resonant cavity and a secondary side current on the secondary side of the resonant cavity. The control circuit further includes a node voltage detection unit configured to detect the voltages of the first node, the second node, the third node, and the fourth node and provide them to the phase shift controller. When the bidirectional DC converter operates in the charging mode and the voltage of the detected third node or the fourth node is at a falling edge, the primary side current and the secondary side current are zero. When the bidirectional DC converter operates in the discharging mode and the voltage of the detected first node or the second node is at a falling edge, the primary side current and the secondary side current are zero.

2. The control circuit according to claim 1, wherein when the bidirectional DC converter operates in the charging mode, the bidirectional DC converter outputs the output voltage and the output current to a vehicle-mounted battery. When the bidirectional DC converter operates in the discharging mode, the bidirectional DC converter receives the input voltage from the vehicle-mounted battery.

3. The control circuit according to claim 1, wherein the adjustment module includes a first arithmetic unit and a voltage loop regulator connected to each other. The first arithmetic unit outputs the difference between the output voltage and the reference voltage to the voltage loop regulator based on the output voltage and the reference voltage. The voltage loop regulator outputs a voltage loop adjustment signal based on the difference between the output voltage and the reference voltage.

4. The control circuit according to claim 3, wherein the adjustment module further includes a comparator, a second arithmetic unit, and a current loop regulator. The comparator is connected to the voltage loop regulator and the second arithmetic unit, and the current loop regulator is connected to the second arithmetic unit and the oscillator. The comparator receives and compares the voltage loop adjustment signal and the reference current, and outputs a signal to the second arithmetic unit according to the comparison result. The second arithmetic unit outputs the difference between the signal and the output current to the current loop regulator according to the signal and the output current. The current loop regulator outputs the adjustment signal to the oscillator according to the difference between the signal and the output current.

5. The control circuit according to claim 4, wherein the signal output by the comparator is the voltage loop adjustment signal or the reference current.

6. The control circuit according to claim 3, wherein the adjustment module further includes a second arithmetic unit, a current loop regulator, and a comparator. The second arithmetic unit is connected to the current loop regulator, and the comparator is connected to the current loop regulator, the voltage loop regulator, and the oscillator. The second arithmetic unit outputs the difference between the output current and the reference current to the current loop regulator according to the output current and the reference current. The current loop regulator outputs a current loop adjustment signal according to the difference between the output current and the reference current. The comparator receives and compares the voltage loop adjustment signal and the current loop adjustment signal, and outputs the adjustment signal to the oscillator according to the comparison result.

7. The control circuit according to claim 6, wherein the adjustment signal output by the comparator is the voltage loop adjustment signal or the current loop adjustment signal.

8. The control circuit according to claim 1, wherein a secondary side current exists on the secondary side of the resonant cavity. The control circuit further includes a resonant cavity detection unit configured to detect the primary side current and the secondary side current and provide them to the phase shift controller.

9. The control circuit according to claim 1 or 8, wherein when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the control circuit delays the conduction times of the first switch and the second switch by the phase shift angle to obtain the conduction times of the sixth switch and the eighth switch respectively. The driving signal of the fifth switch conducts for a period of time or remains in the off state between the turn-off time of the sixth switch and the time when the primary side current becomes zero. The driving signal of the seventh switch conducts for a period of time or remains in the off state between the turn-off time of the eighth switch and the time when the primary side current becomes zero. When the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the control circuit delays the conduction times of the seventh switch and the eighth switch by the phase shift angle to obtain the conduction times of the second switch and the fourth switch respectively. The driving signal of the first switch conducts for a period of time or remains in the off state between the turn-off time of the second switch and the time when the secondary side current becomes zero. The driving signal of the third switch conducts for a period of time or remains in the off state between the turn-off time of the fourth switch and the time when the secondary side current becomes zero.

10. The control circuit according to claim 1 or 8, wherein when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the control circuit delays the conduction times of the first switch and the second switch by the phase shift angle to obtain the conduction times of the seventh switch and the fifth switch respectively. The driving signal of the sixth switch conducts for a period of time or remains in the off state between the turn-off time of the fifth switch and the time when the primary side current becomes zero. The driving signal of the eighth switch conducts for a period of time or remains in the off state between the turn-off time of the seventh switch and the time when the primary side current becomes zero. When the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the control circuit delays the conduction times of the seventh switch and the eighth switch by the phase shift angle to obtain the conduction times of the first switch and the third switch respectively. The driving signal of the fourth switch conducts for a period of time or remains in the off state between the turn-off time of the third switch and the time when the secondary side current becomes zero. The driving signal of the second switch conducts for a period of time or remains in the off state between the turn-off time of the first switch and the time when the secondary side current becomes zero.

11. The control circuit according to claim 1 or 8, wherein when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the control circuit delays the conduction time of the second switching tube by the phase shift angle to obtain the conduction time of the fifth switching tube. The driving signal of the sixth switching tube is complementary to the driving signal of the fifth switching tube. The driving signal of the seventh switching tube conducts for a period of time or remains in the off state between the turn-off time of the fifth switching tube and the time when the primary-side current becomes zero. The driving signal of the eighth switching tube conducts for a period of time or remains in the off state between the turn-off time of the sixth switching tube and the time when the primary-side current becomes zero. When the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the control circuit delays the conduction time of the eighth switching tube by the phase shift angle to obtain the conduction time of the third switching tube. The driving signal of the fourth switching tube is complementary to the driving signal of the third switching tube. The driving signal of the first switching tube conducts for a period of time or remains in the off state between the turn-off time of the third switching tube and the time when the secondary-side current becomes zero. The driving signal of the second switching tube conducts for a period of time or remains in the off state between the turn-off time of the fourth switching tube and the time when the secondary-side current becomes zero.

12. The control circuit according to claim 1 or 8, wherein when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the control circuit delays the conduction time of the first switching tube by the phase shift angle to obtain the conduction time of the seventh switching tube. The driving signal of the eighth switching tube is complementary to the driving signal of the seventh switching tube. The driving signal of the fifth switching tube conducts for a period of time or remains in the off state between the turn-off time of the seventh switching tube and the time when the primary-side current becomes zero. The driving signal of the sixth switching tube conducts for a period of time or remains in the off state between the turn-off time of the eighth switching tube and the time when the primary-side current becomes zero. When the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the control circuit delays the conduction time of the seventh switching tube by the phase shift angle to obtain the conduction time of the first switching tube. The driving signal of the second switching tube is complementary to the driving signal of the first switching tube. The driving signal of the third switching tube conducts for a period of time or remains in the off state between the turn-off time of the first switching tube and the time when the secondary-side current becomes zero. The driving signal of the fourth switching tube conducts for a period of time or remains in the off state between the turn-off time of the second switching tube and the time when the secondary-side current becomes zero.

13. The control circuit according to claim 1, wherein when the bidirectional DC converter operates in the charging mode, the driving signal of the fifth switch tube conducts for a period of time within the time when the voltage at the third node is at a high level, the driving signal of the sixth switch tube conducts for a period of time within the time when the voltage at the third node is at a low level, the driving signal of the seventh switch tube conducts for a period of time within the time when the voltage at the fourth node is at a high level, the driving signal of the eighth switch tube conducts for a period of time within the time when the voltage at the fourth node is at a low level; when the bidirectional DC converter operates in the discharging mode, the driving signal of the first switch tube conducts for a period of time within the time when the voltage at the first node is at a high level, the driving signal of the second switch tube conducts for a period of time within the time when the voltage at the first node is at a low level, the driving signal of the third switch tube conducts for a period of time within the time when the voltage at the second node is at a high level, the driving signal of the fourth switch tube conducts for a period of time within the time when the voltage at the second node is at a low level.

14. The control circuit according to claim 1, wherein the control circuit further comprises an input voltage detection unit, an output voltage detection unit and an output current detection unit. The input voltage detection unit is configured to detect the input voltage and provide it to the phase shift controller. The output voltage detection unit is configured to detect the output voltage and provide it to the regulation module and the phase shift controller. The output current detection unit is configured to detect the output current and provide it to the regulation module.

15. The control circuit according to claim 1, wherein the resonant cavity of the bidirectional DC converter comprises a resonant inductor.

16. The control circuit according to claim 1, wherein the primary side of the resonant cavity comprises a primary side inductor, the secondary side of the resonant cavity comprises a secondary side inductor, and the primary side inductor and the secondary side inductor are equivalent to a resonant inductor.

17. The control circuit according to claim 1, wherein the resonant cavity of the bidirectional DC converter comprises a resonant capacitor.

18. The control circuit according to claim 1, wherein the primary side of the resonant cavity comprises a primary side capacitor, the secondary side of the resonant cavity comprises a secondary side capacitor, and the primary side capacitor and the secondary side capacitor are equivalent to a resonant capacitor.

19. The control circuit according to claim 1, wherein the resonant cavity of the bidirectional DC converter has a resonant frequency, and the switching frequency is greater than the resonant frequency.

20. The control circuit according to claim 1, wherein the oscillator is a voltage-controlled oscillator.

21. A control method is applicable to a bidirectional DC converter. The bidirectional DC converter is applied to a vehicle power supply system and can operate in a charging mode or a discharging mode switchably. The bidirectional DC converter receives an input voltage and outputs an output voltage and an output current. The bidirectional DC converter includes a primary side, a primary circuit, a resonant cavity, a secondary circuit, and a secondary side. The resonant cavity includes a transformer. The primary circuit is electrically connected between the primary side and a primary side of the resonant cavity. The secondary circuit is electrically connected between the secondary side and a secondary side of the resonant cavity. The control method includes the following steps: Step (a): Use an adjustment module to generate an adjustment signal based on the output voltage, a reference voltage, the output current, and a reference current; Step (b): Use an oscillator to receive and generate a switching frequency based on the adjustment signal, and generate a first control signal based on the switching frequency; Step (c): Use a phase shift controller to receive the switching frequency, obtain a phase shift angle based on the input voltage and the output voltage, and generate a second control signal based on the switching frequency and the phase shift angle; Step (d): When the bidirectional DC converter operates in the charging mode, use a primary side drive circuit to receive and generate a primary side drive signal based on the first control signal. When the bidirectional DC converter operates in the discharging mode, use the primary side drive circuit to receive and generate the primary side drive signal based on the second control signal to drive the operation of the primary circuit; And Step (e): When the bidirectional DC converter operates in the charging mode, use a secondary side drive circuit to receive and generate a secondary side drive signal based on the second control signal. When the bidirectional DC converter operates in the discharging mode, use the secondary side drive circuit to receive and generate the secondary side drive signal based on the first control signal to drive the operation of the secondary circuit, wherein the primary circuit of the bidirectional DC converter includes a first bridge arm and a second bridge arm connected in parallel with each other. The first bridge arm includes a first switch tube and a second switch tube connected in series with each other. The second bridge arm includes a third switch tube and a fourth switch tube connected in series with each other. There is a first node between the first switch tube and the second switch tube, and the first node is electrically connected to one end of the primary side. There is a second node between the third switch tube and the fourth switch tube, and the second node is electrically connected to the other end of the primary side. The secondary circuit of the bidirectional DC converter includes a third bridge arm and a fourth bridge arm connected in parallel with each other. The third bridge arm includes a fifth switch tube and a sixth switch tube connected in series with each other. The fourth bridge arm includes a seventh switch tube and an eighth switch tube connected in series with each other. There is a third node between the fifth switch tube and the sixth switch tube, and the third node is electrically connected to one end of the secondary side. There is a fourth node between the seventh switch tube and the eighth switch tube, and the fourth node is electrically connected to the other end of the secondary side, A primary side current exists on the primary side of the resonant cavity, and a secondary side current exists on the secondary side of the resonant cavity. The control circuit further includes a node voltage detection unit configured to detect the voltages of the first node, the second node, the third node, and the fourth node and provide them to the phase shift controller. When the bidirectional DC converter operates in the charging mode and the detected voltage of the third node or the fourth node is on the falling edge, the primary side current and the secondary side current are zero. When the bidirectional DC converter operates in the discharging mode and the detected voltage of the first node or the second node is on the falling edge, the primary side current and the secondary side current are zero.

22. The control method according to claim 21, wherein when the bidirectional DC converter operates in the charging mode, the bidirectional DC converter outputs the output voltage and the output current to a vehicle-mounted battery. When the bidirectional DC converter operates in the discharging mode, the bidirectional DC converter receives the input voltage from the vehicle-mounted battery.

23. The control method according to claim 21, wherein step (a) includes the following sub-steps: Step (a1) using a first arithmetic unit to generate a difference between the output voltage and the reference voltage based on the output voltage and the reference voltage; and Step (a2) using a voltage loop regulator to generate a voltage loop regulation signal based on the difference between the output voltage and the reference voltage.

24. The control method according to claim 23, wherein step (a) further includes the following sub-steps: Step (a3) using a comparator to receive and compare the voltage loop regulation signal and the reference current, and generating a signal based on the comparison result; Step (a4) using a second arithmetic unit to generate a difference between the signal and the output current based on the signal and the output current; and Step (a5) using a current loop regulator to generate the regulation signal based on the difference between the signal and the output current.

25. The control method according to claim 24, wherein in step (a3), the generated signal is the voltage loop regulation signal or the reference current.

26. The control method according to claim 23, wherein step (a) further includes the following sub-steps: Step (a3) using a second arithmetic unit to generate a difference between the output current and the reference current based on the output current and the reference current; Step (a4) using a current loop regulator to generate a current loop regulation signal based on the difference between the output current and the reference current; and Step (a5) using a comparator to receive and compare the voltage loop regulation signal and the current loop regulation signal, and generating the regulation signal based on the comparison result.

27. The control method according to claim 26, wherein in step (a5), the generated regulation signal is the voltage loop regulation signal or the current loop regulation signal.

28. The control method according to claim 21 further includes using a resonant cavity detection unit to detect the primary side current and the secondary side current and provide them to the phase shift controller.

29. The control method according to claim 21 or 28, wherein in step (e), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the conduction times of the first switch tube and the second switch tube are delayed by the phase shift angle to respectively obtain the conduction times of the sixth switch tube and the eighth switch tube. The drive signal of the fifth switch tube conducts for a period of time or remains in the off state between the turn-off time of the sixth switch tube and the time when the primary side current becomes zero. The drive signal of the seventh switch tube conducts for a period of time or remains in the off state between the turn-off time of the eighth switch tube and the time when the primary side current becomes zero. In step (d), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the conduction times of the seventh switch tube and the eighth switch tube are delayed by the phase shift angle to respectively obtain the conduction times of the second switch tube and the fourth switch tube. The drive signal of the first switch tube conducts for a period of time or remains in the off state between the turn-off time of the second switch tube and the time when the secondary side current becomes zero. The drive signal of the third switch tube conducts for a period of time or remains in the off state between the turn-off time of the fourth switch tube and the time when the secondary side current becomes zero.

30. The control method according to claim 21 or 28, wherein in step (e), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the conduction times of the first switch tube and the second switch tube are delayed by the phase shift angle to respectively obtain the conduction times of the seventh switch tube and the fifth switch tube. The drive signal of the sixth switch tube conducts for a period of time or remains in the off state between the turn-off time of the fifth switch tube and the time when the primary side current becomes zero. The drive signal of the eighth switch tube conducts for a period of time or remains in the off state between the turn-off time of the seventh switch tube and the time when the primary side current becomes zero. In step (d), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the conduction times of the seventh switch tube and the eighth switch tube are delayed by the phase shift angle to respectively obtain the conduction times of the first switch tube and the third switch tube. The drive signal of the fourth switch tube conducts for a period of time or remains in the off state between the turn-off time of the third switch tube and the time when the secondary side current becomes zero. The drive signal of the second switch tube conducts for a period of time or remains in the off state between the turn-off time of the first switch tube and the time when the secondary side current becomes zero.

31. The control method according to claim 21 or 28, wherein in step (e), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the conduction time of the second switch tube is delayed by the phase shift angle to obtain the conduction time of the fifth switch tube. The driving signal of the sixth switch tube is complementary to the driving signal of the fifth switch tube. The driving signal of the seventh switch tube conducts for a period of time or remains in the off state between the turn-off time of the fifth switch tube and the time when the primary side current becomes zero. The driving signal of the eighth switch tube conducts for a period of time or remains in the off state between the turn-off time of the sixth switch tube and the time when the primary side current becomes zero. In step (d), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the conduction time of the eighth switch tube is delayed by the phase shift angle to obtain the conduction time of the third switch tube. The driving signal of the fourth switch tube is complementary to the driving signal of the third switch tube. The driving signal of the first switch tube conducts for a period of time or remains in the off state between the turn-off time of the third switch tube and the time when the secondary side current becomes zero. The driving signal of the second switch tube conducts for a period of time or remains in the off state between the turn-off time of the fourth switch tube and the time when the secondary side current becomes zero.

32. The control method according to claim 21 or 28, wherein in step (e), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the charging mode, the conduction time of the first switch tube is delayed by the phase shift angle to obtain the conduction time of the seventh switch tube. The driving signal of the eighth switch tube is complementary to the driving signal of the seventh switch tube. The driving signal of the fifth switch tube conducts for a period of time or remains in the off state between the turn-off time of the seventh switch tube and the time when the primary side current becomes zero. The driving signal of the sixth switch tube conducts for a period of time or remains in the off state between the turn-off time of the eighth switch tube and the time when the primary side current becomes zero. In step (d), when the output voltage gain of the bidirectional DC converter is greater than or equal to one and it operates in the discharging mode, the conduction time of the seventh switch tube is delayed by the phase shift angle to obtain the conduction time of the first switch tube. The driving signal of the second switch tube is complementary to the driving signal of the first switch tube. The driving signal of the third switch tube conducts for a period of time or remains in the off state between the turn-off time of the first switch tube and the time when the secondary side current becomes zero. The driving signal of the fourth switch tube conducts for a period of time or remains in the off state between the turn-off time of the second switch tube and the time when the secondary side current becomes zero.

33. The control method according to claim 21, wherein in the step (e), when the bidirectional DC converter operates in the charging mode, the driving signal of the fifth switch tube conducts for a period of time within the time when the voltage at the third node is at a high level, the driving signal of the sixth switch tube conducts for a period of time within the time when the voltage at the third node is at a low level, the driving signal of the seventh switch tube conducts for a period of time within the time when the voltage at the fourth node is at a high level, and the driving signal of the eighth switch tube conducts for a period of time within the time when the voltage at the fourth node is at a low level. In the step (d), when the bidirectional DC converter operates in the discharging mode, the driving signal of the first switch tube conducts for a period of time within the time when the voltage at the first node is at a high level, the driving signal of the second switch tube conducts for a period of time within the time when the voltage at the first node is at a low level, the driving signal of the third switch tube conducts for a period of time within the time when the voltage at the second node is at a high level, and the driving signal of the fourth switch tube conducts for a period of time within the time when the voltage at the second node is at a low level.

34. The control method according to claim 21, wherein the resonant cavity of the bidirectional DC converter has a resonant frequency, and the switching frequency is greater than the resonant frequency.

Images