Power conversion device, vehicle-mounted charger and control method

Abstract

The invention relates to the technical field of power electronics, and discloses a power conversion device, a vehicle-mounted charger and a control method. The device comprises a transformer, a primary side circuit, a secondary side circuit and a controller, a primary winding of the transformer is connected with the primary circuit, and a secondary winding of the transformer is connected with the secondary circuit; the secondary side circuit comprises a rectifying circuit and an absorption capacitance circuit; the absorption capacitance circuit is connected in parallel with a rectifying power tube in the rectifying circuit; the controller is used for controlling complementary conduction of a power tube in the primary side circuit according to the first duty ratio and a predetermined wave sending number, and pre-charging the absorption capacitor circuit; after the voltage of the absorption capacitor circuit reaches the target pre-charging voltage value, the primary side circuit is started through a driving signal of a second duty ratio, and the first duty ratio is smaller than the second duty ratio. According to the invention, the absorption capacitor in the secondary circuit is pre-charged and then is started, so that the problem that the stress of the rectifier tube in the power conversion device is large, and the direct connection of the primary circuit is easily caused is solved.

Description

Technical Field

[0001] The present application relates to the field of power electronics technology, and in particular to a power conversion device, an on-board charger, and a control method. Background Art

[0002] In isolated DC-DC converter circuits, actively controlled MOS transistors are typically used as rectifying elements in the secondary circuit. A snubber capacitor circuit is also included in the secondary circuit to absorb, suppress, or eliminate unwanted energy in the secondary circuit. While the snubber capacitor circuit can absorb energy, stress on the power transistors in the snubber capacitor circuit can easily cause a shoot-through in the primary circuit during startup, potentially damaging the circuit. Summary of the Invention

[0003] The embodiments of the present application provide a power conversion device, an on-board charger, and a control method to solve the problem that the stress of the rectifier tube in the power conversion device is high and easily causes the primary circuit to be straight-through.

[0004] A first aspect of an embodiment of the present application provides a power conversion device, the power conversion device comprising: a transformer, a primary circuit, a secondary circuit, and a controller;

[0005] The primary winding of the transformer is connected to the primary circuit, and the secondary winding of the transformer is connected to the secondary circuit;

[0006] The secondary circuit includes a rectifier circuit and an absorption capacitor circuit, and the absorption capacitor circuit is connected in parallel with the rectifier power tube in the rectifier circuit;

[0007] The controller is used to:

[0008] According to a first duty cycle and a predetermined number of waves, the power tubes in the primary circuit are controlled to be complementary and turned on to pre-charge the absorption capacitor circuit; after the voltage of the absorption capacitor circuit reaches a target pre-charge voltage value, the primary circuit is started with a drive signal of a second duty cycle, wherein the first duty cycle is smaller than the second duty cycle.

[0009] In a feasible implementation manner of the present application, the absorption capacitor circuit includes an absorption capacitor, a diode, a discharge resistor and an active absorption power tube;

[0010] The active absorption power tube is connected in series with the discharge resistor and then connected in parallel with the diode; the absorption capacitor is connected to the common connection end of the diode and the discharge resistor.

[0011] In a feasible implementation manner of the present application, the secondary winding includes a first connection end and a second connection end;

[0012] The rectifier power tube includes a first rectifier power tube and a second rectifier power tube; the first rectifier power tube is connected to the first connection end, and the second rectifier power tube is connected to the second connection end.

[0013] In a feasible embodiment of the present application, the secondary winding also includes an intermediate connection end located between the first connection end and the second connection end, and the secondary circuit also includes a filter circuit and a switching device, the filter circuit is arranged between the first connection end and the intermediate connection end; the switching device is connected to the filter circuit.

[0014] A second aspect of the embodiments of the present application provides an on-board charger, the on-board charger comprising a power supply, a load power supply, and the power conversion device provided above;

[0015] The power supply is connected to the input end of the primary circuit, and the load power supply is connected to the output end of the secondary circuit.

[0016] A third aspect of the embodiments of the present application provides a control method applied to the power conversion device provided above, the method comprising:

[0017] According to a first duty cycle and a predetermined number of wave transmissions, the power tubes in the primary circuit are controlled to be complementary and conductive, so as to pre-charge the absorption capacitor circuit;

[0018] After the voltage of the absorption capacitor circuit reaches a target pre-charge voltage value, the primary circuit is started with a driving signal of a second duty cycle, wherein the first duty cycle is smaller than the second duty cycle.

[0019] In a feasible implementation manner of the present application, the first duty cycle is calculated by the conduction parameter of the rectifier power tube in the secondary circuit and the input voltage of the primary circuit, wherein the conduction parameter is the shortest conduction time required for the rectifier power tube under the action of the driving signal.

[0020] In a feasible implementation manner of the present application, the first duty cycle is greater than the minimum duty cycle of the rectifier power tube during conduction.

[0021] In a feasible implementation manner of the present application, when the absorption capacitor circuit is pre-charged for the first time, the number of waves transmitted is calculated as follows:

[0022] Calculate a first voltage boost amplitude transmitted from a single wave of the primary circuit to the absorption capacitor circuit based on the input voltage of the primary circuit, the operating frequency of the rectifier power tube in the secondary circuit, the pre-charge period, and the first duty cycle;

[0023] The wave generation quantity is calculated based on the target pre-charge voltage value and the first voltage boost amplitude.

[0024] In a feasible implementation manner of the present application, if the absorption capacitor circuit is pre-charged again, the number of waves transmitted is calculated as follows:

[0025] determining a retention voltage of the absorption capacitor circuit;

[0026] Calculate, based on the input voltage of the primary circuit, the operating frequency of the rectifier power tube in the secondary circuit, the pre-charge period, and the first duty cycle, a second voltage boost amplitude transmitted from the primary circuit to the absorption capacitor circuit by a single wave transmission;

[0027] The wave generation quantity is calculated based on the target pre-charge voltage value, the second voltage boost amplitude, and the retention voltage.

[0028] In a feasible implementation manner of the present application, the target pre-charge voltage value is calculated by the input voltage of the primary circuit and the turns ratio of the transformer.

[0029] The fourth aspect of an embodiment of the present application provides an electronic device, comprising: a memory and at least one processor, wherein instructions are stored in the memory; at least one processor calls the instructions in the memory so that the electronic device executes the control method of the power conversion device of the third aspect mentioned above.

[0030] In the technical solution provided by the embodiment of the present application, the device includes a transformer, a primary circuit, a secondary circuit, and a controller; the primary winding of the transformer is connected to the primary circuit, and the secondary winding of the transformer is connected to the secondary circuit; the secondary circuit includes a rectifier circuit and an absorption capacitor circuit, and the absorption capacitor circuit is connected in parallel with the rectifier power tube in the rectifier circuit; the controller is used to control the power tubes in the primary circuit to be complementary conductive according to a first duty cycle and a predetermined number of wave transmissions, and pre-charge the absorption capacitor circuit; after the voltage of the absorption capacitor circuit reaches a target pre-charge voltage value, the primary circuit is started with a drive signal of a second duty cycle, and the first duty cycle is less than the second duty cycle. That is, in the embodiment of the present application, by controlling the primary circuit to be conductive in advance before the power conversion device is started, the absorption capacitor is pre-charged, and the primary circuit is started when the charge reaches the steady-state operating voltage value of the rectifier power tube in the secondary circuit. This control method not only solves the problem of stress at the moment of startup of the power conversion device causing the primary power tube to be turned on, but also realizes that the secondary capacitor value can be arbitrarily set and the problem of high stress on the rectifier power tube in the secondary circuit is avoided. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of an embodiment of a power conversion device in an embodiment of the present application;

[0032] Figure 2This is a circuit diagram of a power conversion device in an embodiment of the present application;

[0033] Figure 3 This is a schematic diagram of a first embodiment of a control method for a power conversion device in an embodiment of the present application;

[0034] Figure 4 Schematic diagram of a second embodiment of a control method for a power conversion device in an embodiment of the present application;

[0035] Figure 5 This is a working timing diagram of the startup control of the power conversion device in an embodiment of the present application;

[0036] Figure 6 This is a schematic diagram of an electronic device in an embodiment of the present application. DETAILED DESCRIPTION

[0037] An embodiment of the present application provides a power conversion device, an on-board charger, and a control method. The power conversion device is controlled to start up by pre-charging the active absorption capacitor on the secondary circuit of the power conversion device before the power conversion device is powered on. Pre-charging is used to solve the problem that the rectifier tube voltage may be too high when the power conversion device is started.

[0038] The terms "first," "second," "third," "fourth," etc. (if any) in the specification and claims of the present application and in the above-mentioned drawings are used to distinguish similar objects and are not necessarily used to describe a specific order or sequential sequence. It should be understood that the numbers used in this way are interchangeable where appropriate, so that the embodiments of the present application described herein can, for example, be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having," and any variations thereof, are intended to cover non-exclusive inclusions, for example, a process, method, system, product, or apparatus comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products, or apparatus.

[0039] Please refer to Figure 1 , is an implementation method of a power conversion device provided in an embodiment of the present application, and the power conversion device includes a transformer 110, a primary circuit 120, a secondary circuit 130 and a controller 140; it should be noted that the transformer 110 is a two-input and three-output transformer, which includes a primary winding, a magnetic core and a secondary winding, wherein the primary winding has two input ends and the secondary winding has three output ends (leading out pins at both ends and the middle position of the winding respectively).

[0040] In this embodiment, the controller 140 is connected to the primary circuit 120 and the secondary circuit 130 respectively. Specifically, the output end of the controller 140 is connected to the control end of the primary circuit 120 and the secondary circuit 130. The controller 140 drives the rectifier tubes in the primary circuit 120 and the secondary circuit 130 by outputting driving signals with different duty cycles.

[0041] The primary winding of the transformer 110 is connected to the primary circuit 120, and the secondary winding of the transformer 110 is connected to the secondary circuit 130; in actual application, the power conversion device is connected to the load through the output end of the secondary circuit 130, such as a load battery or other electrical equipment.

[0042] The secondary circuit 130 includes a rectifier circuit 131 and an absorption capacitor circuit 132 . The absorption capacitor circuit 132 is connected in parallel with the rectifier power tube in the rectifier circuit 131 .

[0043] In this embodiment, the absorption capacitor circuit 132 includes an absorption capacitor, a diode, a discharge resistor and an active absorption power tube;

[0044] The active absorption power tube is connected in series with the discharge resistor and then connected in parallel with the diode; the absorption capacitor is connected to the common connection end of the diode and the discharge resistor.

[0045] It is understandable that the power conversion device can be a power conversion circuit, such as a DCDC conversion circuit, a DCDC converter, etc. Figure 2 As shown, taking the DCDC conversion circuit as an example, the primary circuit 120 in the DCDC conversion circuit is composed of Figure 2 The power tubes Q1, Q2, Q3 and Q4 in the secondary circuit 130 include a rectifier circuit 131 and an absorption capacitor circuit 132, wherein the rectifier circuit 131 is composed of Figure 2 The rectifier power tubes Q5 and Q6 are composed of the absorption capacitor circuit 132. Figure 2 The absorption power transistors Q8 and Q9, absorption capacitors C1 and C2, and diodes D1 and D2 are composed of the absorption power transistors Q8 and Q9, absorption capacitors C1 and C2, and diodes D1 and D2. Among them, all the power transistors here can be actively controlled MOS transistors, and the MOS transistors can be with or without body diodes. The body diode can provide a freewheeling channel when turned off to maintain the continuous flow of current. The body diode is turned on when turned off, reducing energy loss and improving conversion efficiency.

[0046] Specifically, the secondary winding includes a first connection end, a second connection end and an intermediate connection end;

[0047] The rectifier power tube includes a first rectifier power tube (i.e., Q6) and a second rectifier power tube (i.e., Q5); the first rectifier power tube is connected to the first connection end, the second rectifier power tube is connected to the second connection end, and the intermediate connection end is located between the first connection end and the second connection end.

[0048] In another feasible implementation, the secondary circuit 130 further includes a filter circuit 133 and a switch device 134 . The filter circuit 133 is disposed between the first connection end and the intermediate connection end; and the switch device 134 is connected to the filter circuit 133 .

[0049] like Figure 2 As shown, the filter circuit 133 is composed of an inductor L2 and a capacitor C3, and the switching device 134 is Q7 in the figure. One end of the switching device 134 is connected to the common connection end of the inductor L2 and the capacitor C3, and the other end is connected to the load. The switching device 134 is used to control the voltage output of the power conversion device to the load.

[0050] In this embodiment, based on the above-mentioned circuit structure, in order to reduce the stress of the drain-source voltage Vds of the rectifier power tubes Q5 and Q6 in the secondary circuit 130, the controller 140 successively outputs drive signals with different duty cycles to achieve control, so as to pre-charge the absorption capacitor in the secondary circuit 130 and provide a certain voltage to relieve the voltage stress of the rectifier power tube.

[0051] Specifically, the controller 140 first controls the complementary conduction of the power tubes in the primary circuit 120 according to the first duty cycle and the predetermined number of waves, and pre-charges the absorption capacitor circuit 132; then detects the voltage of the absorption capacitor in the absorption capacitor circuit 132 in real time, and after the voltage of the absorption capacitor in the absorption capacitor circuit 132 reaches the target pre-charge voltage value, starts the primary circuit 120 with a driving signal of a second duty cycle, wherein the first duty cycle is smaller than the second duty cycle.

[0052] It should be noted that the first duty cycle is actually a ratio of high and low signals calculated based on the shortest on-time of the rectifier power section.

[0053] By implementing the device provided above, a signal of the first duty cycle and the corresponding number of waves is output in advance to control the pre-charging of the absorption capacitor in the secondary circuit, and the primary circuit is started after the pre-charge voltage meets the requirements. This control method not only solves the problem of stress at the moment of startup of the power conversion device causing the primary power tube to be directly turned on, but also realizes that the capacitance value of the secondary side can be set at will and avoids the problem of high stress on the rectifier power tube in the secondary circuit.

[0054] See also Figure 3 , Figure 3A flow chart of a control method for a power conversion device provided in an embodiment of the present application. The power conversion device includes a transformer, a primary circuit and a secondary circuit provided on both sides of the transformer, and the secondary circuit is provided with a secondary rectifier circuit and an absorption capacitor circuit. Figure 1 and 2 .

[0055] like Figure 3 As shown, the control method of the power conversion device may include the following implementation steps:

[0056] 301. According to a first duty cycle and a predetermined number of wave transmissions, control the complementary conduction of power tubes in the primary circuit to pre-charge the absorption capacitor circuit.

[0057] This step is actually a control step before the power conversion device is started. Specifically, the power tube in the primary circuit is turned on in a complementary control manner to pre-charge the absorption capacitor circuit of the secondary circuit.

[0058] It should be noted that before the power conversion device is started, it should be understood that before the primary circuit of the power conversion device is normally controlled. Specifically, the control can be achieved by setting two working modes. The first working mode is the pre-charging mode, and the second working mode is the voltage conversion mode. In the pre-charging mode, the driving signal is constructed using the pre-calculated first duty cycle and output to the primary circuit to drive the on and off of each power tube. The input voltage is output to the secondary circuit through the transformer to pre-charge the absorption capacitor circuit.

[0059] In practical applications, the startup instruction of the power conversion device is detected, and the startup instruction is controlled to be executed slowly using a preset buffer setting program to control it to work in a pre-charging mode. In this mode, a PWM signal for pre-charging the absorption capacitor in the secondary circuit is constructed based on the first duty cycle, and then the complementary conduction of the power tube in the primary circuit is controlled based on the PWM signal to output a charging voltage signal to the secondary circuit.

[0060] Through the control of pre-charging, the absorption capacitor on the secondary side stores energy, providing a certain voltage drop for the power tube on the secondary side, so that the voltage drop is not zero when the power conversion device starts and works normally. That is to say, a reverse voltage is provided by the absorption capacitor with a certain voltage to suppress the voltage spike generated during the startup process, thereby avoiding the problem of the primary side power tube being directly connected due to the spike voltage.

[0061] In another feasible embodiment, the complementary controlled PWM signal is calculated based on the parameters of the power tube of the power conversion device. Specifically, the first duty cycle and the number of waves transmitted are first calculated according to the parameters of the power tube, and then the driving signal is constructed based on the first duty cycle and the number of waves transmitted.

[0062] The first duty cycle is calculated by the conduction parameter of the rectifier power tube in the secondary circuit and the input voltage of the primary circuit, wherein the conduction parameter is the shortest conduction time required for the rectifier power tube under the action of the driving signal; the first duty cycle is greater than the minimum duty cycle of the rectifier power tube.

[0063] It is understandable that the driving signal obtained based on the first duty cycle and the number of waves is only output to the power tubes that are both upper bridges or lower bridges, and the power tubes that are both upper bridges or lower bridges are cross-conducted. Figure 2 Q1 and Q2 or Q3 and Q4 in the circuit enable the input voltage to provide energy to the absorption capacitor through the transformer to charge it.

[0064] 302. After the voltage of the absorption capacitor circuit reaches a target pre-charge voltage value, the primary circuit is started with a driving signal of a second duty cycle, where the first duty cycle is smaller than the second duty cycle.

[0065] In this embodiment, in the process of controlling the primary circuit to pre-charge the absorption capacitor circuit, the voltage on the absorption capacitor circuit is detected in real time, and the detected voltage is compared with the target pre-charge voltage value. When the comparison is satisfied, the start instruction is executed to start the primary circuit.

[0066] In another feasible embodiment, since the output drive signal during the pre-charge control process is constructed by the first duty cycle and the number of waves, when detecting whether the target pre-charge voltage value is met, the pre-charge time can be monitored and determined. That is, the pre-charge control countdown is performed at the beginning of pre-charge to achieve monitoring and determination. Specifically, a timing program is set up and the countdown is started at the same time as the pre-charge control is started to control the overall startup control of the power conversion device.

[0067] In an embodiment of the present application, by pre-charging the absorption capacitor circuit, a drain-source voltage is provided to the secondary power tube at the moment of startup, and the spike voltage in the voltage is suppressed to reduce the voltage stress of the power tube during switching, thereby avoiding damage to the power tube due to the spike voltage during startup.

[0068] See also Figure 4 , another flow chart of the control method of the power conversion device provided in an embodiment of the present application, specifically includes:

[0069] 401. Before powering on a power conversion device, calculate a first duty cycle based on parameters of a rectifier power tube in a secondary circuit and an input voltage of the power conversion device.

[0070] It should be noted that the first duty cycle is calculated through the conduction parameter of the rectifier power tube in the secondary circuit and the input voltage of the primary circuit, wherein the conduction parameter is the shortest conduction time required for the rectifier power tube under the action of the driving signal; the first duty cycle is greater than the minimum duty cycle of the rectifier power tube, and the minimum duty cycle is one of the parameters in the rectifier power tube.

[0071] In actual applications, the rectifier power tube is not turned on immediately after the input drive signal, but there is a certain buffer time, and it is turned on after the buffer time. The time that the high level corresponding to this buffer time occupies the entire cycle is the minimum duty cycle.

[0072] 402. Calculate the number of firing waves based on the retained voltage of the absorption capacitor in the secondary circuit, the first duty cycle, and the target pre-charge voltage.

[0073] 403. Determine a first driving signal for precharging the absorption capacitor based on the first duty cycle and the number of transmitted waves.

[0074] It should be noted that the first driving signal is specifically constructed based on two parameters: the first duty cycle and the number of transmitted waves, wherein the number of transmitted waves is calculated based on the parameters of each power tube in the power conversion device and the input voltage.

[0075] Specifically, the number of waves can be calculated in two cases:

[0076] The first is when the absorption capacitor circuit is precharged for the first time, the number of waves is calculated as follows:

[0077] Calculate a first voltage boost amplitude transmitted from a single wave of the primary circuit to the absorption capacitor circuit based on the input voltage of the primary circuit, the operating frequency of the rectifier power tube in the secondary circuit, the pre-charge period, and the first duty cycle;

[0078] The wave generation quantity is calculated based on the target pre-charge voltage value and the first voltage boost amplitude.

[0079] The first method is to pre-charge the absorption capacitor circuit again, and the number of waves is calculated as follows:

[0080] determining a retention voltage of the absorption capacitor circuit;

[0081] Calculate, based on the input voltage of the primary circuit, the operating frequency of the rectifier power tube in the secondary circuit, the pre-charge period, and the first duty cycle, a second voltage boost amplitude transmitted from the primary circuit to the absorption capacitor circuit by a single wave transmission;

[0082] The wave generation quantity is calculated based on the target pre-charge voltage value, the second voltage boost amplitude, and the retention voltage.

[0083] It is understandable that the difference between the first time and the second time lies in whether there is a voltage in the absorption capacitor. If there is a voltage, the number of first drive signals sent is relatively small.

[0084] Furthermore, when the input voltage remains unchanged, the voltage increase amplitude caused by a single wave transmission on the absorption capacitor remains unchanged. When the input voltage changes, it is necessary to recalculate the first duty cycle and the voltage increase amplitude of a single transmission, and then calculate the new transmission quantity based on the retained voltage in the absorption capacitor.

[0085] 404. Based on the first driving signal, control the power tube in the primary circuit to perform complementary wave generation to pre-charge the absorption capacitor circuit.

[0086] Below is Figure 2 Taking the power conversion device of the structure shown in the figure as an example, the startup control of the power conversion device is divided into two stages, namely the pre-charge stage and the normal startup stage. Figure 5 As shown in the figure, T0-T1 is the pre-charge stage, and T1-T2 is the normal startup stage.

[0087] In actual applications, the execution of the two stages is controlled by setting control instructions, that is, whether the start control instruction is triggered. If so, the power conversion device is controlled to enter the pre-charging stage. The control of the pre-charging stage is mainly to generate a first drive signal through the controller and output it to the driver chip to drive the power tubes Q1-Q4 to pre-charge the absorption capacitors C1 and C2.

[0088] That is, during T0-T1, the power conversion device first enters the pre-charge mode, and in the pre-charge mode, a first drive signal is constructed to control Q1 and Q2 to transmit complementary waves. The first drive signal is constructed by setting the first duty cycle of the signal and the number of waves transmitted during T0-T1 to achieve the following:

[0089] 1. First duty cycle: Set the minimum duty cycle in the pre-charge stage to limit the conduction time of the power tubes Q1 and Q2 in the primary circuit, thereby controlling the size of the drain-source current (Ids); the first duty cycle here is also determined according to the type of power tube, that is, the first duty cycle of power tubes with different parameters is different.

[0090] 2. Number of waves: The number of waves in the pre-charge stage is dynamically adjusted according to the input voltage and the minimum pre-charge duty cycle to control the voltage rise amplitude of the active absorption capacitors (C1, C2) to reach the target pre-charge voltage value. The voltage of the absorption capacitor is then used to limit the stress of the drain-source voltage Vds of the power tubes Q8 and Q9. That is, the peak voltage of the drive signal on the power tubes Q8 and Q9 is suppressed by the voltage of the absorption capacitor to reduce the voltage stress.

[0091] In this embodiment, the number of waves is not a fixed value, but is related to the input voltage and the retention voltage of the absorption capacitor. That is, the corresponding number of waves is calculated and calibrated by software according to different input voltages and retention voltages to ensure that the voltage of the active absorption capacitors (C1, C2) is adapted to the target pre-charge voltage value.

[0092] 405. After the voltage of the absorption capacitor circuit reaches the target pre-charge voltage value, start the primary circuit with a driving signal of a second duty cycle.

[0093] The target pre-charge voltage is a voltage value determined by the functional relationship between the input voltage and the transformer turns ratio. Specifically, it is twice the product of the input voltage and the transformer turns ratio, that is, it satisfies the following relationship:

[0094] V 目标预充电压值 =2*Vin / N, where 1 / N is the transformer turns ratio and Vin is the input voltage.

[0095] In an embodiment of the present application, before the power conversion device is started, the power tube of the primary circuit is controlled to transmit the input voltage to the absorption capacitor of the secondary side and pre-charge it; since the capacitor is pre-charged and there is voltage, the power conversion device will not cause direct conduction to the primary power tube when it is started, and it can also ensure that the power tube of the secondary side will not generate excessive stress, so that the startup process is smooth under different input voltages.

[0096] See also Figure 6 As shown, the electronic device includes a processor 600 and a memory 601 , wherein the memory 601 stores machine executable instructions that can be executed by the processor 600 , and the processor 600 executes the machine executable instructions to implement the control method of the power conversion device.

[0097] Furthermore, Figure 6 The electronic device shown further includes a bus 602 and a communication interface 603 , and the processor 600 , the communication interface 603 and the memory 601 are connected via the bus 602 .

[0098] Among them, the memory 601 may include a high-speed random access memory (RAM), and may also include a non-volatile memory (non-volatile memory), for example, at least one disk storage. The communication connection between the system network element and at least one other network element is realized through at least one communication interface 603 (which can be wired or wireless), and the Internet, wide area network, local area network, metropolitan area network, etc. can be used. The bus 602 can be an ISA bus, a PCI bus, or an EISA bus, etc. The bus can be divided into an address bus, a data bus, a control bus, etc. For ease of representation, Figure 6 Only one bidirectional arrow is used in the diagram, but this does not mean that there is only one bus or one type of bus.

[0099] The processor 600 may be an integrated circuit chip with signal processing capabilities. During implementation, each step of the above method can be completed by hardware integrated logic circuits or software instructions in the processor 600. The above processor 600 may be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it may also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of this application. The general-purpose processor may be a microprocessor or any conventional processor. The steps of the method disclosed in the embodiments of this application can be directly implemented and executed by a hardware decoding processor, or by a combination of hardware and software modules in the decoding processor. The software module can be located in a storage medium mature in the art, such as random access memory, flash memory, read-only memory, programmable read-only memory, electrically erasable programmable memory, registers, etc. The storage medium is located in the memory 601 , and the processor 600 reads the information in the memory 601 and completes the method steps of the aforementioned embodiment in combination with its hardware.

[0100] The present application also provides an on-board charger, which includes a power supply, a load power supply and a power conversion device as described in the above embodiment; the power supply is connected to the input end of the primary circuit, and the load power supply is connected to the output end of the secondary circuit.

[0101] Those skilled in the art will clearly understand that, for the convenience and brevity of description, the specific working processes of the systems, devices and units described above can refer to the corresponding processes in the aforementioned method embodiments and will not be repeated here.

[0102] If the functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present application, or the part that contributes to the prior art or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes several instructions for enabling a computer device (which can be a personal computer, a server, or a network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application. The aforementioned storage medium includes various media that can store program codes, such as a USB flash drive, a mobile hard disk, a read-only memory (ROM), a random access memory (RAM), a magnetic disk or an optical disk.

[0103] In the description of the present application, the terms “first”, “second” and “third” are used for descriptive purposes only and should not be understood as indicating or implying relative importance.

[0104] Finally, it should be noted that the above embodiments are only specific implementation methods of the present application, which are used to illustrate the technical solutions of the present application, rather than to limit them. The scope of protection of the present application is not limited thereto. Although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that any person skilled in the art who is familiar with the technical field can still modify the technical solutions described in the above embodiments within the technical scope disclosed in the present application, or make equivalent replacements for some of the technical features therein; and these modifications, changes or replacements do not deviate from the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A power conversion device, characterized in that: The power conversion device includes: a transformer, a primary circuit, a secondary circuit and a controller; The primary winding of the transformer is connected to the primary circuit, and the secondary winding of the transformer is connected to the secondary circuit; The secondary circuit includes a rectifier circuit and an absorption capacitor circuit, and the absorption capacitor circuit is connected in parallel with the rectifier power tube in the rectifier circuit; The controller is used to: According to a first duty cycle and a predetermined number of waves, the power tubes in the primary circuit are controlled to be complementary and turned on to pre-charge the absorption capacitor circuit; after the voltage of the absorption capacitor circuit reaches a target pre-charge voltage value, the primary circuit is started with a drive signal of a second duty cycle, wherein the first duty cycle is smaller than the second duty cycle.

2. The power conversion device according to claim 1, characterized in that: The absorption capacitor circuit includes an absorption capacitor, a diode, a discharge resistor and an active absorption power tube; The active absorption power tube is connected in series with the discharge resistor and then connected in parallel with the diode; the absorption capacitor is connected to the common connection end of the diode and the discharge resistor.

3. The power conversion device according to claim 2, characterized in that: The secondary winding includes a first connection end and a second connection end; The rectifier power tube includes a first rectifier power tube and a second rectifier power tube; the first rectifier power tube is connected to the first connection end, and the second rectifier power tube is connected to the second connection end.

4. The power conversion device according to claim 3, characterized in that: The secondary winding also includes an intermediate connection end located between the first connection end and the second connection end. The secondary circuit also includes a filter circuit and a switching device. The filter circuit is arranged between the first connection end and the intermediate connection end; the switching device is connected to the filter circuit.

5. A vehicle-mounted charger, characterized in that: The on-board charger comprises a power supply, a load power supply and a power conversion device as claimed in any one of claims 1 to 4; The power supply is connected to the input end of the primary circuit, and the load power supply is connected to the output end of the secondary circuit.

6. A control method for a power conversion device according to any one of claims 1 to 4, characterized in that: The method comprises: According to a first duty cycle and a predetermined number of wave transmissions, the power tubes in the primary circuit are controlled to be complementary and conductive, so as to pre-charge the absorption capacitor circuit; After the voltage of the absorption capacitor circuit reaches a target pre-charge voltage value, the primary circuit is started with a driving signal of a second duty cycle, wherein the first duty cycle is smaller than the second duty cycle.

7. The control method of the power conversion device according to claim 6, characterized in that: The first duty cycle is calculated by the conduction parameter of the rectifier power tube in the secondary circuit and the input voltage of the primary circuit, wherein the conduction parameter is the shortest conduction time required for the rectifier power tube under the action of the driving signal.

8. The control method of the power conversion device according to claim 7, characterized in that: The first duty cycle is greater than the minimum duty cycle of the rectifier power tube during conduction.

9. The control method of the power conversion device according to claim 6, characterized in that: When the absorption capacitor circuit is precharged for the first time, the number of waves is calculated as follows: Calculate a first voltage boost amplitude transmitted from a single wave of the primary circuit to the absorption capacitor circuit based on the input voltage of the primary circuit, the operating frequency of the rectifier power tube in the secondary circuit, the pre-charge period, and the first duty cycle; The wave generation quantity is calculated based on the target pre-charge voltage value and the first voltage boost amplitude.

10. The control method of the power conversion device according to claim 6, characterized in that: If the absorption capacitor circuit is precharged again, the number of waves is calculated as follows: determining a retention voltage of the absorption capacitor circuit; Calculate, based on the input voltage of the primary circuit, the operating frequency of the rectifier power tube in the secondary circuit, the pre-charge period, and the first duty cycle, a second voltage boost amplitude transmitted from the primary circuit to the absorption capacitor circuit by a single wave transmission; The wave generation quantity is calculated based on the target pre-charge voltage value, the second voltage boost amplitude, and the retention voltage.

11. The control method of the power conversion device according to claim 6, characterized in that: The target pre-charge voltage value is calculated by the input voltage of the primary circuit and the turns ratio of the transformer.

12. An electronic device, characterized in that: The electronic device includes: a memory and at least one processor, wherein instructions are stored in the memory, and the memory and the at least one processor are interconnected via a line; The at least one processor calls the instructions in the memory so that the electronic device executes the control method of the power conversion device according to any one of claims 6 to 11.

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