Series-parallel switching circuit for bidirectional power conversion

Abstract

The present application discloses a series-parallel switching circuit for bidirectional power conversion. The series-parallel switching circuit comprises: a first bidirectional direct-current (DC) voltage source and a second bidirectional DC voltage source; a first bidirectional DC / DC isolation conversion circuit and a second bidirectional DC / DC isolation conversion circuit; a series-parallel switching switch for setting a connection relationship between the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit to a series relationship or a parallel relationship; a first output filter capacitor and a second output filter capacitor, wherein when the series-parallel switching switch is switched, voltages on the first output filter capacitor and the second output filter capacitor remain unchanged; and a bleeder circuit and a soft-start circuit. According to the circuit, a rapid series-parallel switching function of the bidirectional DC / DC isolation conversion circuits can be achieved, and the applicability of the bidirectional DC / DC isolation conversion circuits can be greatly improved.

Description

Series-parallel switching circuit for bidirectional power conversion

[0001] This application claims priority to the Chinese patent application with application number 2023112438961 filed with the State Intellectual Property Office of China on September 26, 2023, and priority to the Chinese patent application with the invention title “Series-parallel switching circuit for bidirectional power conversion”, all contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the technical field of electric energy conversion, and in particular to a series-parallel switching circuit for bidirectional power conversion. Background Art

[0003] With the rapid development of the new energy industry and new battery technologies, power conversion has evolved from traditional unidirectional flow to bidirectional flow, driving a growing range of new energy applications. To achieve bidirectional energy flow, isolated DC / DC topologies require a wider voltage gain conversion ratio, high power density, reliable input and output electrical isolation, and higher conversion efficiency.

[0004] Currently, to achieve a wide output voltage range in bidirectional DC / DC converter circuits, a series-parallel design is typically employed to convert two bidirectional DC / DCs. These topologies typically employ dual active bridge circuits or bidirectional LLC circuits, which are current source conversion topologies. When performing series-parallel conversion, current source conversion circuits require completely disconnecting the output circuit from the external environment, reducing the output capacitor voltage to 0V via a bleeder circuit, and then performing series-parallel switching and pre-charge soft-start. This solution cannot achieve fast switching between series and parallel circuits.

[0005] Summary of the Invention

[0006] In view of this, the present application provides a series-parallel switching circuit for bidirectional power conversion to solve the problem of being unable to achieve fast switching of series-parallel switching.

[0007] In a first aspect, the present application provides a series-parallel switching circuit for bidirectional power conversion, comprising:

[0008] A first bidirectional DC voltage source and a second bidirectional DC voltage source are configured to provide a DC voltage for bidirectional power conversion, wherein the energy transfer direction from the first bidirectional DC voltage source to the second bidirectional DC voltage source is forward;

[0009] The first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit are used to realize a bidirectional DC-to-DC conversion function;

[0010] a series-parallel switching switch, configured to connect the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit to a series connection or a parallel connection, so that the series-parallel switching circuit for bidirectional power conversion switches between a series operating mode and a parallel operating mode;

[0011] a first output filter capacitor and a second output filter capacitor, wherein the first output filter capacitor is an output filter capacitor of the first bidirectional DC / DC isolation converter circuit, and the second output filter capacitor is an output filter capacitor of the second bidirectional DC / DC isolation converter circuit, wherein when the series-parallel switch is switched, the voltages on the first output filter capacitor and the second output filter capacitor remain unchanged;

[0012] a discharge circuit, configured to discharge the first output filter capacitor and the second output filter capacitor when the circuit is powered off;

[0013] A soft-start circuit includes a soft-start relay switch and a soft-start resistor, which is used to pre-charge the capacitance of the first output filter capacitor and the second output filter capacitor so that the voltage difference between the first output filter capacitor, the second output filter capacitor and the first bidirectional DC voltage source or the second bidirectional DC voltage source is within a preset range.

[0014] According to the aspects and any possible implementation methods described above, an implementation method is further provided, wherein the series-parallel switching switch includes a first switch, a second switch, a third switch and a fourth switch, wherein when the first switch and the second switch are closed and the third switch and the fourth switch are disconnected, the series-parallel switching circuit of the bidirectional power conversion is switched to the parallel working mode, and when the first switch and the second switch are disconnected and the third switch and the fourth switch are closed, the series-parallel switching circuit of the bidirectional power conversion is switched to the series working mode, wherein the path of the series-parallel switching switch does not include the first output filter capacitor and / or the second output filter capacitor, wherein one end of the first output filter capacitor is connected to the positive side of the voltage source, one end of the second output filter capacitor is connected to the negative side of the voltage source, and the other end of the first output filter capacitor is connected to the other end of the second output filter capacitor.

[0015] According to the aspects described above and any possible implementation method, an implementation method is further provided. When the series-parallel switching circuit of the bidirectional power conversion operates in the forward energy transfer power-up state, the soft-start relay switch is in the disconnected state. Thereafter, the first bidirectional DC voltage source or the second bidirectional DC voltage source charges the internal voltage through the soft-start resistor, wherein the internal voltage includes the voltage on the first output filter capacitor and the second output filter capacitor. When the voltage difference across the soft-start relay switch reaches a preset threshold, the soft-start relay switch is closed to complete the pre-charging action.

[0016] According to the aspects described above and any possible implementation, an implementation is further provided, in which when the series-parallel switching circuit of the bidirectional power conversion is powered off, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, then the soft start relay switch is disconnected, and the output voltage is obtained. When the output voltage drops to a preset safe voltage range, the discharge circuit is started to discharge the internal voltage to complete the discharge function.

[0017] According to the aspects described above and any possible implementation method, an implementation method is further provided. When the series-parallel switching circuit of the bidirectional power conversion switches from the series working mode to the parallel working mode, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy. Afterwards, a delay operation is performed according to the parallel working mode switched by the series-parallel switching switch, and after the delay operation ends, the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit is started to complete the switching of the parallel working mode.

[0018] According to the above aspects and any possible implementation, an implementation is further provided, in which, in the delayed operation of the parallel working mode switched according to the series-parallel switching switch, a first time is delayed after the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, the first switch and the second switch are disconnected after the first time delay, and a second time is delayed, and the third switch and the fourth switch are closed after the second time delay, and then a third time is delayed to start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the third time delay, thereby completing the switching of the parallel working mode, wherein the first time is set according to the current freewheeling time, the second time is set according to the delay of the soft-start relay switch disconnecting action, and the third time is set according to the delay of the soft-start relay switch closing action.

[0019] According to the aspects described above and any possible implementation method, an implementation method is further provided. When the series-parallel switching circuit of the bidirectional power conversion switches from the parallel working mode to the series working mode, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy. Afterwards, a delay operation is performed according to the series working mode switched by the series-parallel switching switch, and after the delay operation ends, the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit is started to complete the switching of the series working mode.

[0020] According to the above aspects and any possible implementation, an implementation is further provided, in which, in the delayed operation of the series working mode switched by the series-parallel switching switch, a first time is delayed after the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, the third switch and the fourth switch are disconnected after the first time delay, and a second time is delayed, and the first switch and the second switch are closed after the second time delay, and then a third time is delayed to start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the third time delay, thereby completing the switching of the series working mode, wherein the first time is set according to the current freewheeling time, the second time is set according to the delay of the soft-start relay switch disconnecting action, and the third time is set according to the delay of the soft-start relay switch closing action.

[0021] In a second aspect, the present application provides a method for switching the working mode of bidirectional power conversion, including using the series-parallel switching circuit of the bidirectional power conversion as described in the first aspect to realize switching between the series working mode and the parallel working mode.

[0022] In a third aspect, the present application provides a switching power supply comprising a series-parallel switching circuit for bidirectional power conversion as described in the first aspect.

[0023] In the present application, by setting two bidirectional DC / DC isolation conversion circuits and corresponding output filter capacitors, and making the voltage across the output filter capacitors of the two bidirectional DC / DC isolation conversion circuits remain unchanged during the series-parallel switching process, the decoupling process between the series-parallel switching of the two bidirectional DC / DC isolation conversion circuits and the corresponding output filter capacitors is realized, the adhesion risk of the voltage difference switching across the soft start relay is eliminated, and the power discharge function and soft start pre-charge function are supported during the series-parallel switching of the two bidirectional DC / DC isolation conversion circuits. The present application greatly reduces the series-parallel switching time of the bidirectional DC / DC isolation conversion circuit, can realize the series-parallel fast switching function of the bidirectional DC / DC isolation conversion circuit, and greatly improves the applicability of the bidirectional DC / DC isolation conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0025] FIG1 is a schematic diagram of a series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application;

[0026] FIG2 is a schematic diagram of a dual active bridge series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application;

[0027] 3 is a flow chart of a control method for a series-parallel switching circuit for bidirectional power conversion according to an embodiment of the present application;

[0028] FIG4 is a schematic diagram of another series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application;

[0029] FIG5 is a schematic diagram of a series-parallel switching circuit for another bidirectional power conversion in an embodiment of the present application. DETAILED DESCRIPTION

[0030] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0031] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0032] The terms used in the embodiments of the present application are for the purpose of describing specific embodiments only and are not intended to limit the present application. The singular forms "a", "an", "this", and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms unless the context clearly indicates otherwise.

[0033] It should be understood that the term "and / or" as used herein is simply a term used to describe the existence of three possible relationships between related objects. For example, "A and / or B" can represent the existence of A alone, the existence of both A and B, and the existence of B alone. Furthermore, the character " / " in this document generally indicates that the related objects are in an "or" relationship.

[0034] It should be understood that although the terms "first," "second," and "third" may be used in the embodiments of the present application to describe preset ranges, etc., these preset ranges should not be limited to these terms. These terms are merely used to distinguish one preset range from another. For example, without departing from the scope of the embodiments of the present application, the first preset range may also be referred to as the second preset range, and similarly, the second preset range may also be referred to as the first preset range.

[0035] The word "if," as used herein, may be interpreted as "at the time of" or "when" or "in response to determining" or "in response to detecting," depending on the context. Similarly, the phrases "if it is determined" or "if (stated condition or event) is detected" may be interpreted as "when it is determined" or "in response to the determination" or "when detecting (stated condition or event)" or "in response to detecting (stated condition or event)," depending on the context.

[0036] The present application provides a series-parallel switching circuit for bidirectional power conversion, comprising:

[0037] The first bidirectional DC voltage source and the second bidirectional DC voltage source are used to provide DC voltage for bidirectional power conversion, wherein the energy transfer direction from the first bidirectional DC voltage source to the second bidirectional DC voltage source is forward.

[0038] Bidirectional power supports both forward and reverse power transmission, and DC voltage sources can be provided in both the forward and reverse directions. Specifically, in the embodiments of this application, the power direction from the first bidirectional DC voltage source to the second bidirectional DC voltage source is defined as the forward direction, and this is used as the basis for the following explanation.

[0039] The first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit are used to realize a bidirectional DC-to-DC conversion function.

[0040] In one embodiment, the core components for realizing bidirectional power conversion in the series-parallel switching circuit of bidirectional power conversion are a first bidirectional DC / DC isolation conversion circuit and a second bidirectional DC / DC isolation conversion circuit. The two circuits can specifically realize a wide range of bidirectional voltage output through series-parallel switching, thereby making the output range of the output voltage wider.

[0041] The series-parallel switching switch is used to set the connection relationship between the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit to a series relationship or a parallel relationship, so that the series-parallel switching circuit of the bidirectional power conversion switches to operate in a series working mode or a parallel working mode.

[0042] In one embodiment, a series-parallel switching function for realizing bidirectional power conversion can be specifically provided with a series-parallel switching switch, which includes two switching modes. One is to place the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit in a series relationship. At this time, the circuit switches to the series working mode, and the upper limit of the voltage output value in this series working mode can be higher; the other is to place the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit in a parallel relationship. At this time, the circuit switches to the parallel working mode, and the lower limit of the voltage output value in this series working mode can be lower.

[0043] A first output filter capacitor and a second output filter capacitor, the first output filter capacitor is the output filter capacitor of the first bidirectional DC / DC isolation conversion circuit, and the second output filter capacitor is the output filter capacitor of the second bidirectional DC / DC isolation conversion circuit, wherein when the series-parallel switch is switched, the voltage on the first output filter capacitor and the second output filter capacitor remains unchanged.

[0044] In one embodiment, the circuit power conversion is accompanied by a filtering requirement. The present application specifically provides a first output filter capacitor and a second output filter capacitor. The filter capacitor is specifically provided for the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit to filter the output current. It should be noted that the present application focuses on decoupling the first output filter capacitor and the second output filter capacitor from the series-parallel switching switch so that the voltage on the first output filter capacitor and the second output filter capacitor is not affected when the series-parallel switching switch is switched. This approach can avoid the problem of the voltage difference between the first output filter capacitor and the second output filter capacitor and the external voltage (the first bidirectional DC voltage source voltage or the second bidirectional DC voltage source voltage) being too large when the series-parallel switching switch is switched. In this way, there is no need to completely disconnect the connection between the internal and external (DC voltage source) of the circuit, and the rapid switching of the series-parallel switching can be achieved without having to wait for the whole process.

[0045] The discharge circuit is used to discharge the first output filter capacitor and the second output filter capacitor when the circuit is powered off.

[0046] In one embodiment, when the series-parallel switching circuit of the bidirectional power conversion is in a power-off shutdown state, or the power supply is unplugged online, if a shutdown command is received or a power unplug signal is recognized, the first output filter capacitor and the second output filter capacitor can be discharged through the discharge circuit, so that the circuit discharges the first output filter capacitor and the second output filter capacitor to a safe voltage, thereby achieving effective protection of the circuit.

[0047] The soft-start circuit includes a soft-start relay switch and a soft-start resistor, which are used to pre-charge the capacitance of the first output filter capacitor and the second output filter capacitor so that the voltage difference between the first output filter capacitor, the second output filter capacitor and the first bidirectional DC voltage source or the second bidirectional DC voltage source is within a preset range.

[0048] In one embodiment, the soft-start circuit provided in the present application is applied before the bidirectional power conversion and is associated with the decoupling setting of the series-parallel switching switch, the first output filter capacitor and the second output filter capacitor. Specifically, the soft-start circuit will pre-charge the first output filter capacitor and the second output filter capacitor before the bidirectional power conversion, and make the voltage on the first output filter capacitor and the second output filter capacitor equal to or close to the voltage on the bidirectional DC voltage source. In this way, in view of the above-mentioned decoupling setting of the series-parallel switching switch, the first output filter capacitor and the second output filter capacitor, since the voltage on the first output filter capacitor and the second output filter capacitor is not affected when the series-parallel switching switch is switched, the voltage on the first output filter capacitor and the second output filter capacitor will be kept within a safe range with the external voltage, and the switching of the series-parallel switching switch will not cause the circuit to be disconnected for discharge operation. The present application can seamlessly realize the switching between the series working mode and the parallel working mode under the premise of circuit safety, significantly improving the applicability of the series-parallel switching circuit for bidirectional power conversion.

[0049] Furthermore, the series-parallel switching switch includes a first switch, a second switch, a third switch and a fourth switch, wherein when the first switch and the second switch are closed and the third switch and the fourth switch are disconnected, the series-parallel switching circuit of the bidirectional power conversion is switched to a parallel working mode, and when the first switch and the second switch are disconnected and the third switch and the fourth switch are closed, the series-parallel switching circuit of the bidirectional power conversion is switched to a series working mode, wherein the path of the series-parallel switching switch does not include the first output filter capacitor and / or the second output filter capacitor, wherein one end of the first output filter capacitor is connected to the positive side of the voltage source, one end of the second output filter capacitor is connected to the negative side of the voltage source, and the other end of the first output filter capacitor is connected to the other end of the second output filter capacitor.

[0050] Furthermore, when the series-parallel switching circuit of the bidirectional power conversion operates in the forward energy transfer power-on state, the soft-start relay switch is in the disconnected state. Afterwards, the first bidirectional DC voltage source or the second bidirectional DC voltage source charges the internal voltage through the soft-start resistor, wherein the internal voltage includes the voltage on the first output filter capacitor and the second output filter capacitor. When the voltage difference across the soft-start relay switch reaches a preset threshold, the soft-start relay switch is closed to complete the pre-charging action.

[0051] Furthermore, when the series-parallel switching circuit of the bidirectional power conversion switches from the series working mode to the parallel working mode, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy. Afterwards, a delay operation is performed according to the parallel working mode switched by the series-parallel switching switch, and after the delay operation is completed, the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit is started to complete the switching of the parallel working mode.

[0052] Furthermore, in the delayed operation according to the parallel working mode switched by the series-parallel switching switch, a first time is delayed after the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, the first switch and the second switch are disconnected after the first delay, and a second time is delayed, and the third switch and the fourth switch are closed after the second delay, and then a third time is delayed to start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the third delay, thereby completing the switching of the parallel working mode, wherein the first time is set according to the current follow-flow time, the second time is set according to the delay of the soft-start relay switch disconnection action, and the third time is set according to the delay of the soft-start relay switch closing action.

[0053] Furthermore, when the series-parallel switching circuit of the bidirectional power conversion switches from the parallel working mode to the series working mode, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy. Afterwards, a delay operation is performed according to the series working mode switched by the series-parallel switching switch, and after the delay operation is completed, the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit is started to complete the switching of the series working mode.

[0054] Furthermore, in the delayed operation according to the series working mode switched by the series-parallel switching switch, a first time is delayed after the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, and the third switch and the fourth switch are disconnected after the first delay, and a second time is delayed. After the second delay, the first switch and the second switch are closed. Thereafter, a third time is delayed to start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the third delay, thereby completing the switching of the series working mode, wherein the first time is set according to the current follow-flow time, the second time is set according to the delay of the soft-start relay switch disconnection action, and the third time is set according to the delay of the soft-start relay switch closing action.

[0055] Furthermore, when the series-parallel switching circuit of the bidirectional power conversion is powered off, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy. After that, the soft start relay switch is disconnected and the output voltage is obtained. When the output voltage drops to a preset safe voltage range, the discharge circuit is started to discharge the internal voltage to complete the discharge function.

[0056] The present application and more possible implementation methods are described below in detail with reference to the accompanying drawings.

[0057] Figure 1 is a schematic diagram of a series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application. As shown in Figure 1, the series-parallel switching circuit for bidirectional power conversion includes two (upper and lower) bidirectional DC / DC isolation conversion circuits, namely bidirectional DC / DC isolation conversion circuit 1# and bidirectional DC / DC isolation conversion circuit 2#.

[0058] Specifically, Vin→Vo can be defined as the forward energy transfer direction, where Vin is the bidirectional DC input voltage source, Vo is the bidirectional DC output voltage source, K1 / K2 / K3 / K4 work together as a series-parallel switching switch, C1 is the upper output filter capacitor, C2 is the lower output filter capacitor, Cbus is the input filter capacitor, K5 is the soft-start relay switch, Rs is the soft-start resistor, Ds is the soft-start diode, and the output side includes a discharge circuit and an EMC (Electromagnetic Compatibility) filter circuit.

[0059] Furthermore, based on FIG1 , in order to illustrate in more detail the implementation of the series-parallel switching circuit for bidirectional power conversion and the related control method of the present application, a series-parallel connection of dual active bridge circuits is specifically described as an example.

[0060] Figure 2 is a schematic diagram of a dual active bridge series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application. As shown in Figure 2, Vin is the forward DC input voltage, Vo is the forward DC output voltage, Cbus is the input filter capacitor, C1 is the upper output filter capacitor, C2 is the lower output filter capacitor, Cout is the output full bus capacitor, Q1 / Q2 / Q3 / Q4 are the primary active switches of the upper dual active bridge, Q5 / Q6 / Q7 / Q8 are the secondary active switches of the upper dual active bridge, L1 is the resonant inductor of the upper circuit, Cd1 is the DC blocking capacitor of the upper primary circuit, Cd3 is the DC blocking capacitor of the upper secondary circuit, Tr1 is the upper main transformer; Q11 / Q12 / Q13 / Q14 are the lower circuits. The primary side active switching tube of the upper dual active bridge, Q15 / Q16 / Q17 / Q18 are the secondary side active switching tubes of the lower dual active bridge, L2 is the resonant inductor of the lower channel, Cd2 is the DC blocking capacitor of the primary side of the lower channel, Cd4 is the DC blocking capacitor of the secondary side of the lower channel, Tr2 is the lower main transformer; K1 / K2 / K3 / K4 are series-parallel switching switches, Rx is the bleeder resistor, Qx is the bleeder switching tube, Lf is the common-mode filter inductor, K5 is the soft-start relay switch, Rs is the soft-start resistor, Ds is the soft-start diode, Isamp1 is the upper current sampling resistor, and Isamp2 is the lower current sampling resistor.

[0061] Taking Figure 2 as an example, when the bidirectional circuit operates in the forward energy transfer state, the soft-start relay switch K5 is in the disconnected state, and the low voltages across the output capacitor Cout, the upper output filter capacitor C1, and the lower output filter capacitor C2 are all 0V. At this time, the external voltage Vin charges the internal output capacitor Cout, the upper output filter capacitor C1, and the lower output filter capacitor C2 of the circuit through the soft-start resistor Rs. When the internal voltage pre-charge is close to Vin, the voltage difference across the soft-start relay switch K5 is close to 0V, and the soft-start relay switch K5 is closed to complete the pre-charge action.

[0062] Taking Figure 2 as an example, when the series-parallel switching circuit of the bidirectional power conversion is powered off and is in a power-off shutdown state, or when the power supply is unplugged online, if a shutdown command is received or a power unplug signal is recognized, the series-parallel switching circuit of the bidirectional power conversion performs the following steps:

[0063] Set the switch drives of the main power switches Q1 / Q2 / Q3 / Q4 / Q5 / Q6 / Q7 / Q8 and Q11 / Q12 / Q13 / Q14 / Q15 / Q16 / Q17 / Q18 to low to stop energy transmission.

[0064] After stopping the energy transmission and sealing the wave, the soft start relay switch K5 is disconnected, and the output voltage Vin is identified. When the output voltage Vin drops to a safe voltage, the discharge switch Qx of the discharge circuit is activated, and the residual voltage of the output internal capacitor Cout, the upper output filter capacitor C1, and the lower output filter capacitor C2 is discharged to a safe voltage through the discharge circuit, thereby realizing the discharge function.

[0065] Taking Figure 2 as an example, when switching from series operation mode to parallel operation mode in the forward working state, when the bidirectional power supply is operating in series operation mode, K5 is closed, the voltage Vcout across the internal output capacitor Cout is consistent with the external output voltage Vo, and the circuit is in series operation mode, K1 / K2 are closed, and K3 / K4 are open. When the bidirectional power supply operating mode needs to be switched to parallel operation mode, perform the following steps:

[0066] Set the switch drives of the main power switches Q1 / Q2 / Q3 / Q4 / Q5 / Q6 / Q7 / Q8 and Q11 / Q12 / Q13 / Q14 / Q15 / Q16 / Q17 / Q18 to low to stop energy transmission.

[0067] The specific process is as follows:

[0068] Stop energy transmission and wave sealing, delay the continuous current for a short period of time t1 (t1 can be designed to be several or dozens of switch working cycles), and then disconnect K1 / K2.

[0069] In this way, after stopping energy transmission and blocking the wave, the residual electric energy stored in the inductor L1 after blocking the wave can be removed according to the delayed short freewheeling time t1, so that the internal voltage and external voltage of the circuit are still kept within the safe range.

[0070] After K1 / K2 is disconnected, the relay disconnection action time t2 is delayed (t2 can be specifically designed as the maximum delay of the relay disconnection action), and then K3 / K4 is closed.

[0071] Delay the relay closing action time t3 (t3 can be specifically designed as the maximum delay of the relay closing action), and then start the main power switch tube to realize the parallel energy transmission working mode.

[0072] It should be noted that the relay action time t2 and the delayed relay closing action time t3 can take into account the delay of relay opening and closing, and can further eliminate the problem of excessive difference between internal voltage and external voltage during relay opening or closing.

[0073] Taking Figure 2 as an example, when switching from parallel operation mode to series operation mode in the forward working state, when the bidirectional power supply is operating in parallel mode, K5 is closed, the voltage Vcout across the internal output capacitor Cout is consistent with the external output voltage Vo, and the circuit is in parallel operation mode. K3 / K4 are closed, and K1 / K2 are open. When the bidirectional power supply operating mode needs to be switched to series operation mode, perform the following steps:

[0074] Set the switch drives of the main power switches Q1 / Q2 / Q3 / Q4 / Q5 / Q6 / Q7 / Q8 and Q11 / Q12 / Q13 / Q14 / Q15 / Q16 / Q17 / Q18 to low to stop energy transmission.

[0075] The specific process is as follows:

[0076] After stopping energy transmission and sealing the wave, a short follow-flow time t1 is delayed (t1 can be specifically designed to be several or dozens of switch working cycles), and then K3 / K4 is disconnected.

[0077] After K3 / K4 is disconnected, the relay disconnection action time t2 is delayed (t2 can be specifically designed as the maximum delay of the relay disconnection action), and then K1 / K2 is closed.

[0078] Delay the relay closing action time t3 (t3 can be specifically designed as the maximum delay of the relay closing action), and then start the main power switch tube to realize the series energy transfer working mode.

[0079] Furthermore, when the bidirectional circuit is in reverse operating mode, the switching circuit operating mode implements the same logic as in forward operation. When the circuit is in reverse power-up mode, the external voltage Vin also charges the circuit's internal output capacitor Cout, the upper output filter capacitor C1, and the lower output filter capacitor C2 through the soft-start resistor Rs, completing the pre-charge operation. When the reverse operating mode switches from series to parallel operation and vice versa, the operating logic is the same as in the forward mode.

[0080] In order to implement the technical solution of this application and enable more engineering and technical workers to easily understand and apply the present invention, we will further explain how to implement the series-parallel switching circuit and corresponding control method for bidirectional power conversion in combination with specific embodiments.

[0081] FIG3 is a flow chart of a control method corresponding to a series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application.

[0082] Specifically, the specific implementation of the control method of the present application can be based on the digital control chip of the bidirectional power supply module and implemented through the detailed control flow in Figure 3.

[0083] (1) Power on the bidirectional power module.

[0084] (2) Through the soft start diode Ds and the soft start resistor Rs, pre-charge the output voltage Vcout of the internal capacitor to the external voltage Vo.

[0085] (3) Receive the power-on instruction and the output voltage setting value Vo_set of the power control system, close the soft start relay switch K5, and the current working range of the power module is Sq.

[0086] (4) Determine the series-parallel working range Sw of the bidirectional power supply by setting the voltage Vo_set. Among them, when the module demand setting voltage is in the high voltage section, enter the series mode working mode and set Sw to 1; when the module demand setting voltage is in the low voltage section, enter the parallel mode working mode and set Sw to 0.

[0087] (5) Identify the series-parallel working state. When Sw is equal to Sq, there is no need to change the series-parallel gear. When Sw is not equal to Sq, series-parallel switching is required.

[0088] (6) When Sw = 1, it is necessary to switch to the series working mode. Conversely, when Sw = 0, it is necessary to switch to the parallel working mode.

[0089] (7) Switch to the series gear and perform the switching from the parallel working mode to the series working mode.

[0090] (8) Switch to the parallel gear and perform the switching from the series working mode to the parallel working mode.

[0091] (9) After the switching is completed, start the power switch tube to generate waves, and enter the series working mode or the parallel working mode.

[0092] (10) Receive the shutdown instruction or detect the power unplug signal.

[0093] (11) When receiving the shutdown instruction or detecting the power unplug signal, stop the wave signal of the power tube and stop the output of energy transfer.

[0094] (12)-(13) Detect whether the external output voltage Vo drops below the safety voltage. When it does not drop to the safety voltage Vsafe, continue to wait for judgment.

[0095] (14) When it is detected that the external output voltage Vo < Vsafe, enable the discharge action and discharge the internal voltage to the safety voltage.

[0096] (15) The strategy ends and the module shuts down.

[0097] Among them, (16) is the external control of the power supply control system, including setting the output voltage requirement and setting the switching power supply on and off in accordance with steps (3) and (10).

[0098] (17) is one of the operations that triggers (10). When the user manually unplugs the power supply, the digital control chip of the bidirectional power supply module can detect that the power supply is unplugged.

[0099] FIG4 is a schematic diagram of another series-parallel switching circuit for bidirectional power conversion in an embodiment of the present application.

[0100] FIG5 is a schematic diagram of a series-parallel switching circuit for another bidirectional power conversion in an embodiment of the present application.

[0101] Furthermore, the series-parallel switching circuit for bidirectional power conversion proposed in the present application can be transformed into circuits with two different connection forms as shown in Figures 4 and 5. It can be seen that the circuits with these two connection forms can also decouple C1, C2 and K1, K2, K3, and K4, and the voltages on C1 and C2 will not change according to the switching of the series-parallel switching switches. The circuits of Figures 4 and 5 can also realize fast series-parallel switching of bidirectional DC / DC isolation conversion circuits.

[0102] In the present application, by setting two bidirectional DC / DC isolation conversion circuits and corresponding output filter capacitors, and making the voltage across the output filter capacitors of the two bidirectional DC / DC isolation conversion circuits remain unchanged during the series-parallel switching process, the decoupling process between the series-parallel switching of the two bidirectional DC / DC isolation conversion circuits and the corresponding output filter capacitors is realized, the adhesion risk of the voltage difference switching across the soft start relay is eliminated, and the power discharge function and soft start pre-charge function are supported during the series-parallel switching of the two bidirectional DC / DC isolation conversion circuits. The present application greatly reduces the series-parallel switching time of the bidirectional DC / DC isolation conversion circuit, can realize the series-parallel fast switching function of the bidirectional DC / DC isolation conversion circuit, and greatly improves the applicability of the bidirectional DC / DC isolation conversion circuit.

[0103] Furthermore, the present application also provides a method for switching the working mode of bidirectional power conversion, including using the series-parallel switching circuit of the bidirectional power conversion as described in the above embodiment to realize switching between the series working mode and the parallel working mode.

[0104] Furthermore, the present application also provides a switching power supply, comprising the series-parallel switching circuit for bidirectional power conversion as described in the above embodiment.

[0105] It should be understood that all solutions and products implemented based on the above-mentioned series-parallel switching circuit for bidirectional power conversion should fall within the scope of protection of this application.

[0106] Those skilled in the art will clearly understand that for the sake of convenience and brevity of description, only the division of the above-mentioned functional units and modules is used as an example. In actual applications, the above-mentioned functions can be distributed and completed by different functional units and modules as needed, that is, the internal structure of the device can be divided into different functional units or modules to complete all or part of the functions described above.

[0107] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A series-parallel switching circuit for bidirectional power conversion, characterized in that: include: A first bidirectional DC voltage source and a second bidirectional DC voltage source are used to provide a DC voltage for bidirectional power conversion, wherein the energy transfer direction from the first bidirectional DC voltage source to the second bidirectional DC voltage source is a forward direction; The first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit are used to realize a bidirectional DC-to-DC conversion function; A series-parallel switching switch, used to set the connection relationship between the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit to a series relationship or a parallel relationship, so that the series-parallel switching circuit of the bidirectional power conversion switches to work in a series working mode or a parallel working mode; a first output filter capacitor and a second output filter capacitor, wherein the first output filter capacitor is an output filter capacitor of the first bidirectional DC / DC isolation conversion circuit, and the second output filter capacitor is an output filter capacitor of the second bidirectional DC / DC isolation conversion circuit, wherein when the series-parallel switching switch is switched, the voltages on the first output filter capacitor and the second output filter capacitor remain unchanged; A discharge circuit, used for discharging the first output filter capacitor and the second output filter capacitor when the circuit is powered off; A soft-start circuit includes a soft-start relay switch and a soft-start resistor, which are used to pre-charge the capacitance of the first output filter capacitor and the second output filter capacitor so that the voltage difference between the first output filter capacitor, the second output filter capacitor and the first bidirectional DC voltage source or the second bidirectional DC voltage source is within a preset range.

2. The circuit according to claim 1, characterized in that The series-parallel switching switch includes a first switch, a second switch, a third switch and a fourth switch, wherein when the first switch and the second switch are closed and the third switch and the fourth switch are opened, the series-parallel switching circuit of the bidirectional power conversion is switched to the parallel working mode, and when the first switch and the second switch are opened and the third switch and the fourth switch are closed, the series-parallel switching circuit of the bidirectional power conversion is switched to the series working mode, wherein the passage path of the series-parallel switching switch does not include the first output filter capacitor and / or the second output filter capacitor, wherein one end of the first output filter capacitor is connected to the positive side of the voltage source, one end of the second output filter capacitor is connected to the negative side of the voltage source, and the other end of the first output filter capacitor is connected to the other end of the second output filter capacitor.

3. The circuit according to claim 1, characterized in that When the series-parallel switching circuit of the bidirectional power conversion operates in the forward energy transfer power-on state, the soft-start relay switch is in the disconnected state, and then the first bidirectional DC voltage source or the second bidirectional DC voltage source charges the internal voltage through the soft-start resistor, wherein the internal voltage includes the voltage on the first output filter capacitor and the second output filter capacitor, and when the voltage difference across the soft-start relay switch reaches a preset threshold, the soft-start relay switch is closed to complete the pre-charging action.

4. The circuit according to claim 3, characterized in that When the series-parallel switching circuit of the bidirectional power conversion is powered off, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, and then the soft start relay switch is disconnected, and the output voltage is obtained. When the output voltage drops to a preset safety voltage range, the discharge circuit is started to discharge the internal voltage to complete the discharge function.

5. The circuit according to claim 2, characterized in that When the series-parallel switching circuit of the bidirectional power conversion switches from the series working mode to the parallel working mode, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, and then perform a delay operation according to the parallel working mode switched by the series-parallel switching switch, and start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the delay operation to complete the switching of the parallel working mode.

6. The circuit according to claim 5, characterized in that In the delay operation of the parallel working mode switched according to the series-parallel switching switch, a first time is delayed after the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, the first switch and the second switch are disconnected after the first time is delayed, and a second time is delayed, and the third switch and the fourth switch are closed after the second time is delayed, and then a third time is delayed to start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the third time is delayed, so as to complete the switching of the parallel working mode, wherein the first time is set according to the current follow-up time, the second time is set according to the delay of the disconnection action of the soft-start relay switch, and the third time is set according to the delay of the closing action of the soft-start relay switch.

7. The circuit according to claim 2, characterized in that When the series-parallel switching circuit of the bidirectional power conversion switches from the parallel working mode to the series working mode, the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, and then perform a delay operation according to the series working mode switched by the series-parallel switching switch, and start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the delay operation ends, thereby completing the switching of the series working mode.

8. The circuit according to claim 7, characterized in that In the delay operation of the series working mode switched according to the series-parallel switching switch, a first time is delayed after the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit stop transmitting energy, the third switch and the fourth switch are disconnected after the first time is delayed, and a second time is delayed, and the first switch and the second switch are closed after the second time is delayed, and then a third time is delayed to start the energy transmission function of the first bidirectional DC / DC isolation conversion circuit and the second bidirectional DC / DC isolation conversion circuit after the third time is delayed, so as to complete the switching of the series working mode, wherein the first time is set according to the current follow-up time, the second time is set according to the delay of the disconnection action of the soft-start relay switch, and the third time is set according to the delay of the closing action of the soft-start relay switch.

9. A method for switching working modes of bidirectional power conversion, characterized in that: The series-parallel switching circuit for bidirectional power conversion as described in any one of claims 1 to 8 is used to realize switching between a series working mode and a parallel working mode.

10. A switching power supply, characterized in that: A series-parallel switching circuit for bidirectional power conversion comprising the circuit described in any one of claims 1-8.

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