Flyback conversion circuit and flyback converter

Abstract

The utility model provides a flyback conversion circuit and a flyback converter, and relates to the technical field of power conversion. In the flyback conversion circuit, according to the connection relation of three switching tubes, under the condition that a second chopping switching tube is in an on state and the other two switching tubes are in an off state, junction capacitors of a first chopping switching tube and a first switching tube are provided with charge and discharge paths, and the charge and discharge paths of the first chopping switching tube and the second switching tube are provided with charge and discharge paths. Under the condition that the first switching tube is in the on state and the other two switching tubes are in the off state, the junction capacitor of the second chopping switching tube is provided with a charging and discharging path, so that the junction capacitors of the three switching tubes can be charged and discharged, and the junction capacitors of the three switching tubes can be discharged completely. As each switching tube performs state switching under the condition that the discharge of the junction capacitor of the switching tube is finished, namely, each switching tube performs state switching under the condition that the voltages at the two ends of the switching tube are equal to zero, the flyback conversion circuit can reduce the switching loss of the switching tubes in the flyback conversion circuit.

Description

Technical Field

[0001] The utility model relates to the technical field of power conversion, in particular to a flyback conversion circuit and a flyback converter. Background Art

[0002] At present, the flyback conversion circuit has the advantages of simple structure, small number of components, multi-channel output, easy control and low cost, and is widely used in adapters, auxiliary power supplies and other occasions.

[0003] Traditional flyback converter circuits use only one switching transistor for chopping. However, this transistor performs hard switching at the moment of turn-on, resulting in high switching losses. This reduces the efficiency of the flyback converter circuit and causes large voltage and current spikes and oscillations. It can also cause significant electromagnetic interference, impacting the flyback converter circuit's electromagnetic compatibility (EMC) performance. These issues are particularly pronounced when the switching transistor is made of power electronic devices made from new-generation semiconductor materials such as silicon carbide and gallium nitride.

[0004] Therefore, how to reduce the switching loss of the switch tube in the flyback conversion circuit is a technical problem that needs to be solved urgently. Utility Model Content

[0005] In view of this, the present invention provides a flyback conversion circuit and a flyback converter to reduce the switching loss of a switch tube in the flyback conversion circuit.

[0006] To achieve the above objectives, the present invention provides the following technical solutions:

[0007] On one hand, the present application provides a flyback conversion circuit, comprising: an input capacitor, a transformer, a first target switch tube, and two chopper switch tubes; wherein:

[0008] The input end of the first chopper switch tube is connected to one end of the input capacitor, and the connection point serves as the first end of the input side of the flyback conversion circuit;

[0009] The output end of the first chopper switch tube is connected to the input end of the second chopper switch tube through the primary winding of the transformer;

[0010] The output end of the second chopper switch tube is connected to the other end of the input capacitor, and the connection point serves as the second end of the input side of the flyback conversion circuit;

[0011] The input end of the first switch tube is connected to the output end of the first chopping switch tube, and the output end of the first switch tube is connected to the output end of the second chopping switch tube;

[0012] The second chopper switch tube is in a conducting state when the other two switch tubes are in a turned-off state;

[0013] The first switch tube is in the on state when the other two switch tubes are in the off state;

[0014] Each switch tube switches state when its own junction capacitance is fully discharged.

[0015] Optionally, it further includes: at least one anti-reverse module;

[0016] The transformer comprises at least one secondary winding;

[0017] In at least one of the secondary windings, the first end of each of the secondary windings is respectively connected to the current output end of each of the anti-reverse modules, and the current input end of each of the anti-reverse modules serves as the corresponding end of the corresponding output side of the flyback conversion circuit;

[0018] or,

[0019] In at least one of the secondary windings, the second end of each of the secondary windings is connected to the current input end of each of the anti-reverse modules, and the current output end of each of the anti-reverse modules serves as the corresponding end of the corresponding output side of the flyback conversion circuit;

[0020] The first end of each secondary winding is the same as the first end of the primary winding; the first end of the primary winding is the end of the primary winding connected to the output end of the first chopper switch tube.

[0021] Optionally, the flyback conversion circuit further includes: at least one output capacitor; the output capacitor is provided between both ends of each secondary winding;

[0022] and / or,

[0023] The flyback conversion circuit further includes an absorption module; the current input end of the absorption module is connected to the input end of the second chopper switch tube, and the current output end of the absorption module is connected to the output end of the second chopper switch tube.

[0024] Optionally, the absorption module includes: an absorption resistor, an absorption capacitor and a first diode; wherein:

[0025] The anode of the first diode is connected to the input end of the second chopper switch tube;

[0026] The cathode of the first diode is connected to one end of the absorption resistor and one end of the absorption capacitor respectively;

[0027] The other end of the absorption resistor is connected to the other end of the absorption capacitor, and the connection point is connected to the output end of the second chopper switch tube.

[0028] Optionally, each of the anti-reverse modules includes: a second diode; in each of the anti-reverse modules: an anode of the second diode serves as a current input terminal of the anti-reverse module in which it is located, and a cathode of the second diode serves as a current output terminal of the anti-reverse module in which it is located;

[0029] or,

[0030] Each of the anti-reverse modules includes: a second switch tube; in each of the anti-reverse modules: a first end of the second switch tube serves as a current input end of the anti-reverse module, and a second end of the second switch tube serves as a current output end of the anti-reverse module;

[0031] The first end of the second switch tube is an end connected to the anode of its own body diode on the second switch tube, and the second end of the second switch tube is an end connected to the cathode of its own body diode on the second switch tube.

[0032] Optionally, it further includes: a soft switching capacitor; wherein:

[0033] One end of the soft switch capacitor is connected to the input end of the second chopper switch tube, and the other end of the soft switch capacitor is connected to the output end of the second chopper switch tube.

[0034] Another aspect of the present application provides a flyback converter, comprising: at least two layers of PCB boards arranged side by side and the flyback conversion circuit as described in any one of the previous aspects of the present application; wherein:

[0035] A through hole is provided on each layer of the PCB board, and the magnetic core of the transformer in the flyback conversion circuit passes through the through hole on each layer of the PCB board;

[0036] The windings on the transformer are respectively arranged on each layer of the PCB board, and the windings arranged on each layer of the PCB board are wound along the through holes on each layer of the PCB board;

[0037] Other components in the flyback conversion circuit are respectively arranged on the PCB boards of each layer.

[0038] Optionally, the primary winding of the transformer is divided into 2N groups, where N is a positive integer, and the 2N groups are symmetrically arranged on the N layers of PCB boards located at the top and the N layers of PCB boards located at the bottom;

[0039] The transformer includes at least one secondary winding, and each secondary winding is respectively arranged on each layer of the PCB board located in the middle.

[0040] Optionally, the first chopper switch tube in the flyback conversion circuit is arranged on any layer of the PCB board located at the top;

[0041] The second chopper switch tube in the flyback conversion circuit is arranged on any one of the top layers of the PCB board;

[0042] The first switch tube in the flyback conversion circuit is arranged on any layer of the PCB board at the bottom;

[0043] The input capacitor in the flyback conversion circuit is arranged on any layer of the PCB board located at the bottom.

[0044] Optionally, the flyback conversion circuit includes at least one output capacitor, and each of the output capacitors is arranged on any layer of the PCB board located at the top;

[0045] and / or,

[0046] The flyback conversion circuit includes an absorption module; the absorption module includes an absorption resistor, an absorption capacitor and a first diode; the absorption resistor is arranged on any layer of the PCB board located at the top; the absorption capacitor is arranged on any layer of the PCB board located at the bottom; and the first diode is arranged on any layer of the PCB board located at the bottom.

[0047] and / or,

[0048] The flyback conversion circuit includes at least one anti-flyback module, and each of the anti-flyback modules is arranged on any one of the top layers of the PCB board.

[0049] Optionally, except for the windings of the transformer, other devices arranged on each layer of the PCB board are arranged at a position where the distance between them and the magnetic core is less than a preset value.

[0050] It can be seen from the above technical solution that the present invention provides a flyback conversion circuit. It can be seen from the connection relationship of the three switching tubes that when the second chopper switching tube is in the on state and the other two switching tubes are in the off state, the junction capacitances of the first chopper switching tube and the first switching tube both have a charge and discharge path, and when the first switching tube is in the on state and the other two switching tubes are in the off state, the junction capacitance of the second chopper switching tube has a charge and discharge path, so that the junction capacitances of the three switching tubes can all be charged and discharged, so that the junction capacitances of the three switching tubes can all be discharged. In addition, since each switching tube switches state when its own junction capacitance is discharged, that is, each switching tube switches state when the voltage across its own terminals is equal to zero, the flyback conversion circuit can reduce the switching loss of the switching tubes in itself. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0052] Figures 1-9 Schematic diagrams of the structures of nine implementations of the flyback conversion circuit provided in the embodiments of the present application;

[0053] Figure 10a A schematic structural diagram of the top PCB board of the flyback converter provided in an embodiment of the present application;

[0054] Figure 10b A schematic structural diagram of a middle-layer PCB board of a flyback converter provided in an embodiment of the present application;

[0055] Figure 10c A schematic diagram of the structure on the bottom PCB board of the flyback converter provided in an embodiment of the present application;

[0056] Figure 11 A flowchart of a soft switch control method provided in an embodiment of the present application;

[0057] Figure 12 for Figure 8 The schematic diagram of the working process of the flyback conversion circuit shown. DETAILED DESCRIPTION

[0058] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, 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 efforts are within the scope of protection of this application.

[0059] In this application, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus comprising the element.

[0060] In order to reduce the switching loss of the switch tube in the flyback conversion circuit, the present application provides a flyback conversion circuit, the specific structure of which is as follows: Figure 1 As shown, it specifically includes: input capacitor Cin, transformer T and three switching tubes. The connection relationship between each component is as follows:

[0061] The input end of the first chopper switch tube S1 is connected to one end of the input capacitor Cin, and the connection point serves as the first end of the input side of the flyback conversion circuit. The output end of the first chopper switch tube S1 is connected to the input end of the second chopper switch tube S3 via the primary winding of the transformer T. The output end of the second chopper switch tube S3 is connected to the other end of the input capacitor Cin, and the connection point serves as the second end of the input side of the flyback conversion circuit. The first chopper switch tube S1 and the second chopper switch tube S3 are first switched to the on state simultaneously, and then switched to the off state simultaneously, and this cycle repeats, that is, the first chopper switch tube S1 and the second chopper switch tube S3 jointly perform chopping.

[0062] Optional, such as Figure 1 As shown, the first chopper switch tube S1 can be a MOS tube. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific circumstances, all of which are within the protection scope of this application.

[0063] It should be noted that Figure 1 Coss_S1 in is the junction capacitance of the first chopper switch tube S1.

[0064] Optional, such as Figure 1 As shown, the second chopper switch tube S3 can be a MOS tube. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific circumstances, all of which are within the protection scope of this application.

[0065] It should be noted that the connection method of the secondary winding of the transformer T is the same as the connection method of the secondary winding of the transformer T in the flyback conversion circuit in the prior art, and will not be repeated here. In addition, under normal circumstances, if Figure 1 As shown, the primary winding of transformer T can be equivalent to the leakage inductance and the excitation inductance connected in series. In addition, Figure 1 Coss_S3 in is the junction capacitance of the second chopper switch tube S3.

[0066] As can be seen from the above, the first chopper switch tube S1 and the second chopper switch tube S3 jointly perform chopping, and the connection method of the secondary winding of the transformer T in the flyback conversion circuit provided by this embodiment is the same as the connection method of the secondary winding of the transformer T in the flyback conversion circuit in the prior art. Therefore, the flyback conversion circuit provided by this embodiment complies with the working principle of flyback conversion, and the flyback conversion circuit provided by this embodiment can realize flyback conversion.

[0067] The input end of the first switch tube S2 is connected to the output end of the first chopping switch tube S1 , and the output end of the first switch tube S2 is connected to the output end of the second chopping switch tube S3 .

[0068] Optional, such as Figure 1 As shown, the first switch tube S2 can be a MOS tube. In practical applications, including but not limited to this, no specific limitation is made here. It can be determined according to specific circumstances and is within the protection scope of this application.

[0069] It should be noted that Figure 1 Coss_S2 in is the junction capacitance of the first switch tube S2.

[0070] The second chopper switch tube S3 is in the on state when the other two switch tubes are in the off state. Figure 1 It can be seen that when the second chopper switch tube S3 is in the on state and the other two switch tubes are in the off state, the junction capacitance of the first chopper switch tube S1 forms a loop with the leakage inductance and the excitation inductance through the input capacitor Cin and the second chopper switch tube S3, and the junction capacitance of the first switch tube S2 forms a loop with the leakage inductance and the excitation inductance through the second chopper switch tube S3. Therefore, in this case, the junction capacitance of the first chopper switch tube S1 and the junction capacitance of the first switch tube S2 both have a charging and discharging path.

[0071] The first switch tube S2 is in the on state when the other two switch tubes are in the off state. Figure 1 It can be seen that when the first switch tube S2 is in the on state and the other two switch tubes are in the off state, the junction capacitance of the second chopper switch tube S3 forms a loop through the first switch tube S2, the leakage inductance, and the excitation inductance. Therefore, in this case, the junction capacitance of the second chopper switch tube S3 has a charging and discharging path.

[0072] It should be noted that how the junction capacitances of the three switching tubes are charged and discharged will be described in detail in the following embodiments and will not be elaborated here.

[0073] Each switch tube switches state when its own junction capacitance is fully discharged.

[0074] It should be noted that how to implement state switching of each switch tube when its junction capacitance is completely discharged will be described in detail in the following embodiments and will not be repeated here.

[0075] As can be seen from the above, when the second chopper switch tube S3 is in the on state and the other two switches are in the off state, the junction capacitances of the first chopper switch tube S1 and the first switch tube S2 both have a charge and discharge path. Furthermore, when the first switch tube S2 is in the on state and the other two switches are in the off state, the junction capacitance of the second chopper switch tube S3 has a charge and discharge path. Therefore, the junction capacitances of all three switches can be charged and discharged, and thus the junction capacitances of all three switches can be fully discharged. Furthermore, because each switch tube switches state when its own junction capacitance is fully discharged, that is, each switch tube switches state when its own voltage across its terminals is zero, this flyback conversion circuit can reduce the switching losses of the switches within itself.

[0076] Another embodiment of the present application provides another implementation of the flyback conversion circuit, the specific structure of which is as follows: Figure 1 、 Figure 2 or Figure 3 In this embodiment, the transformer T includes at least one secondary winding and is provided with at least one anti-reverse module 10 .

[0077] In a specific example, if Figure 1 or Figure 3 As shown, in at least one secondary winding, the first end of each secondary winding is respectively connected to the current output end of each anti-reverse module 10, and the current input end of each anti-reverse module 10 serves as the corresponding end of the corresponding output side of the flyback conversion circuit.

[0078] For example, the transformer T includes two secondary windings, and the flyback conversion circuit includes two anti-backlash modules 10. The first end of the first secondary winding is connected to the current output end of the first anti-backlash module, the current input end of the first anti-backlash module serves as the first end of the first output side of the flyback conversion circuit, and the second end of the first secondary winding serves as the second end of the first output side of the flyback conversion circuit. The first end of the second secondary winding is connected to the current output end of the second anti-backlash module, the current input end of the second anti-backlash module serves as the first end of the second output side of the flyback conversion circuit, and the second end of the second secondary winding serves as the second end of the second output side of the flyback conversion circuit.

[0079] The anti-reverse module 10 is a module that only allows current to flow in and out of one end. Specifically, the current input end of the anti-reverse module 10 refers to the port on the anti-reverse module 10 that allows current to flow in, and the current output end of the anti-reverse module 10 refers to the port on the anti-reverse module 10 that allows current to flow out. For example, assuming that current flows into the first end of the anti-reverse module 10 and flows out of the second end of the anti-reverse module 10, the first end of the anti-reverse module 10 is the current input end of the anti-reverse module 10, and the second end of the anti-reverse module 10 is the current output end of the anti-reverse module 10.

[0080] The first end of each secondary winding is the same as the first end of the primary winding; the first end of the primary winding is the end of the primary winding connected to the output end of the first chopper switch tube S1.

[0081] In another specific example, Figure 2 As shown, in at least one secondary winding, the second end of each secondary winding is respectively connected to the current input end of each anti-reverse module 10, and the current output end of each anti-reverse module 10 serves as the corresponding end of the corresponding output side of the flyback conversion circuit.

[0082] For example, the transformer T includes two secondary windings, and the flyback conversion circuit includes two anti-backlash modules 10. The first end of the first secondary winding serves as the first end of the first output side of the flyback conversion circuit, the second end of the first secondary winding is connected to the current input end of the first anti-backlash module, and the current output end of the first anti-backlash module serves as the second end of the first output side of the flyback conversion circuit. The first end of the second secondary winding serves as the first end of the second output side of the flyback conversion circuit, the second end of the second secondary winding is connected to the current input end of the second anti-backlash module, and the current output end of the second anti-backlash module serves as the second end of the second output side of the flyback conversion circuit.

[0083] It should be noted that the anti-reverse module 10, the current input end of the anti-reverse module 10, the current output end of the anti-reverse module 10, and the first end of each secondary winding are the same as those in the above example and will not be repeated here.

[0084] The above two examples show two connection methods for each secondary winding, which are not specifically limited here and can be determined according to specific circumstances and are all within the scope of protection of this application.

[0085] Taking the secondary winding of a transformer T as an example, it can be seen from the above two examples that when the first chopper switch tube S1 and the second chopper switch tube S3 are both switched to the on state, the current induced by the secondary winding flows in from its second end and flows out from its first end. Therefore, the current induced by the secondary winding cannot flow through the corresponding anti-reverse module 10, and thus there is no current on the output side of the flyback conversion circuit. When the first chopper switch tube S1 and the second chopper switch tube S3 are both switched to the off state, the current induced by the secondary winding flows in from its first end and flows out from its second end. Therefore, the current induced by the secondary winding can flow through the corresponding anti-reverse module 10, and thus there is current on the output side of the flyback conversion circuit. In summary, the connection method of the secondary winding conforms to the working principle of the flyback conversion. Therefore, the flyback conversion circuit provided in this embodiment can achieve flyback conversion.

[0086] Another embodiment of the present application provides another implementation of the flyback conversion circuit, the specific structure of which is as follows: Figure 4 or Figure 5 As shown, this embodiment, based on the above embodiment, further includes: at least one output capacitor COUT. The connection relationship between the various components is as follows:

[0087] An output capacitor COUT is provided between the two ends of each secondary winding. In practical applications, a capacitor with a larger capacitance can be directly selected as the output capacitor COUT, or multiple capacitors with smaller capacitance can be connected in parallel to form the output capacitor COUT.

[0088] Since the output capacitor COUT is arranged between the two ends of the secondary winding, the output capacitor COUT can clamp the voltage at both ends of the secondary winding, thereby avoiding overvoltage of the load connected to the secondary winding, thereby reducing the possibility of damage to the load connected to the secondary winding, and thus improving the safety performance of the flyback converter circuit.

[0089] Another embodiment of the present application provides another implementation of the flyback conversion circuit, the specific structure of which is as follows: Figure 6 or Figure 7 As shown, this embodiment further includes an absorption module 20 based on the above embodiment. The connection relationship between these components is as follows:

[0090] The current input end of the absorption module 20 is connected to the input end of the second chopper switch tube S3 , and the current output end of the absorption module 20 is connected to the output end of the second chopper switch tube S3 .

[0091] As can be seen from the connection relationship of the absorption module 20, the absorption module 20 can clamp the voltage between the input and output ends of the second chopper switch tube S3, thereby avoiding overvoltage of the second chopper switch tube S3, thereby reducing the possibility of damage to the second chopper switch tube S3, and further improving the safety performance of the flyback conversion circuit.

[0092] Another embodiment of the present application provides a specific implementation of the absorption module 20, and its specific structure is as follows Figure 6 or Figure 7 As shown, it specifically includes: absorption resistor Rx, absorption capacitor Cclamp and first diode D1. The connection relationship between each component is as follows:

[0093] The anode of the first diode D1 is connected to the input terminal of the second chopper switch S3. The cathode of the first diode D1 is connected to one end of an absorption resistor Rx and one end of an absorption capacitor Cclamp, respectively. The other end of the absorption resistor Rx is connected to the other end of the absorption capacitor Cclamp, and the connection point is connected to the output terminal of the second chopper switch S3.

[0094] It should be noted that Figure 6 or Figure 7 Coss_D1 in is the junction capacitance of the first diode D1.

[0095] It can be seen from the above connection relationship that this embodiment of the absorption module 20 is an RCD absorption circuit. The RCD absorption circuit is very mature in the prior art, and its working principle will not be described in detail here.

[0096] Another embodiment of the present application provides a specific implementation of the anti-reverse module 10, which is applicable to each anti-reverse module 10. The specific structure of this implementation is as follows. Figures 1 to 5 or Figure 7 As shown, it specifically includes: a second diode D2.

[0097] The anode of the second diode D2 serves as the current input terminal of the anti-reverse module 10 in which it is located, and the cathode of the second diode D2 serves as the current output terminal of the anti-reverse module 10 in which it is located. In practical applications, a diode with a larger maximum current allowed to flow can be directly selected as the second diode D2, or multiple diodes with smaller maximum current allowed to flow can be selected and connected in parallel to serve as the second diode D2.

[0098] It should be noted that the use of diodes to limit the direction of current, that is, to achieve the anti-reverse function, is already very mature in the prior art, and its specific principles will not be described in detail here. Figures 1 to 5 or Figure 7 Coss_D2 in is the junction capacitance of the second diode D2.

[0099] Another embodiment of the present application provides another specific implementation of the anti-reverse module 10, which is applicable to each anti-reverse module 10. The specific structure of this implementation is as follows: Figure 6 As shown, it specifically includes: a second switch tube S4.

[0100] The first end of the second switch tube S4 serves as the current input end of the anti-reverse module 10 , and the second end of the second switch tube S4 serves as the current output end of the anti-reverse module 10 .

[0101] The first end of the second switch tube S4 is connected to the anode of its own body diode, and the second end of the second switch tube S4 is connected to the cathode of its own body diode.

[0102] It should be noted that Figure 6 Coss_S4 in is the junction capacitance of the second switch tube S4.

[0103] Optional, such as Figure 6 As shown, the second switch tube S4 can be a MOS tube. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific circumstances, all of which are within the protection scope of this application.

[0104] As can be seen from the above, the anode of the body diode of the second switch transistor S4 serves as the current input terminal of the anti-reverse module 10, and the cathode of the body diode of the second switch transistor S4 serves as the current output terminal of the anti-reverse module 10. Therefore, this embodiment of the anti-reverse module 10 is equivalent to a diode. Since the use of diodes to limit current direction, that is, to achieve the anti-reverse function, is well-established in the prior art, its specific principles will not be described in detail here.

[0105] In addition, if the maximum current that the body diode can withstand when forward biased is small, so that the second switch tube S4 cannot meet the actual current demand, the second switch tube S4 can also be switched to meet the actual current demand. The specific method of switching the state of the second switch tube S4 is as follows: when the first chopper switch tube S1 and the second chopper switch tube S3 are switched to the on state at the same time, the second switch tube S4 is switched to the off state; when the first chopper switch tube S1 and the second chopper switch tube S3 are switched to the off state at the same time, the second switch tube S4 is switched to the on state.

[0106] As can be seen from the above, the second switch tube S4 switches to the on state when its own body diode is forward biased, thereby increasing the current-bearing capacity of the second switch tube S4 when its own body diode is forward biased, thereby increasing the possibility that the second switch tube S4 meets the actual current demand.

[0107] Another embodiment of the present application provides another implementation of the flyback conversion circuit, the specific structure of which is as follows: Figure 8 or Figure 9 As shown, this embodiment, based on the above embodiment, further includes: a soft switching capacitor CZVS. The connection relationship between these components is as follows:

[0108] One end of the soft switch capacitor CZVS is connected to the input end of the second chopper switch tube S3, and the other end of the soft switch capacitor CZVS is connected to the output end of the second chopper switch tube S3, that is, the soft switch capacitor CZVS is connected in parallel with the junction capacitance of the second chopper switch tube S3.

[0109] Since the soft switch capacitor CZVS is connected in parallel to the junction capacitance of the second chopper switch tube S3 , the junction capacitance of the second chopper switch tube S3 can be adjusted when the discharge current is stable by adjusting the capacitance of the soft switch capacitor CZVS.

[0110] Another embodiment of the present application provides a flyback converter, the specific structure of which is as follows: Figure 10a to Figure 10c As shown, it specifically includes: at least two layers of PCB boards, and the flyback conversion circuit provided in the above embodiment of the present application.

[0111] The PCB boards of each layer are arranged side by side.

[0112] Through holes are provided on each layer of the PCB board, and the magnetic core 100 of the transformer T in the flyback conversion circuit passes through the through holes on each layer of the PCB board.

[0113] The windings on the transformer T are respectively arranged on each layer of PCB boards, and the windings arranged on each layer of PCB boards are wound along the through holes on each layer of PCB boards. The windings on the transformer T include the primary winding and all the secondary windings.

[0114] Other components in the flyback conversion circuit are respectively arranged on each layer of the PCB board.

[0115] Any two layers of PCB boards are electrically connected by way of vias 200. Since any two layers of PCB boards are electrically connected by way of vias 200, this is already very mature in the prior art and will not be described in detail herein.

[0116] In this embodiment, since the PCB layers are arranged side by side, and the magnetic core 100 of the transformer T passes through through-holes provided on each PCB layer, the windings provided on each PCB layer are wound along the through-holes on the PCB layer, thereby achieving the winding of the magnetic core 100 and realizing the voltage transformation function of the transformer T. Furthermore, this arrangement of the transformer T can reduce the size of the transformer T, thereby reducing the size of the flyback converter, thereby reducing the overall cost of the flyback converter and allowing the flyback converter to be applied in more scenarios.

[0117] Another embodiment of the present application provides another implementation of a flyback converter. This implementation differs from the above implementation in that:

[0118] In this embodiment, the primary winding of the transformer T is divided into 2N groups, where N is a positive integer, and the 2N groups are symmetrically arranged on the top N-layer PCB board and the bottom N-layer PCB board. Figure 10a to Figure 10c As shown, the number of layers of the PCB board is equal to 3, which are respectively recorded as the top PCB board, the middle PCB board, and the bottom PCB board. The primary winding of the transformer T is divided into two groups 01 and 02, and the two groups 01 and 02 are respectively set on the top PCB board and the bottom PCB board.

[0119] In this embodiment, the transformer T includes at least one secondary winding, and each secondary winding is respectively arranged on each layer of the PCB board located in the middle. Figure 10b As shown, the transformer T includes a secondary winding 03, which is arranged on the middle layer PCB board.

[0120] In this embodiment, since the primary windings of the transformer T are divided into multiple groups and are respectively arranged on different PCB boards, the area of ​​each layer of the PCB board is reduced, so that the structure of the flyback transformer T is more symmetrical, thereby reducing the volume of the flyback converter, and further reducing the overall cost of the flyback converter, and also allowing the flyback converter to be applied in more scenarios.

[0121] Another embodiment of the present application provides another implementation of a flyback converter. This implementation differs from the above implementation in that:

[0122] In this embodiment, the first chopper switch tube S1 in the flyback conversion circuit is arranged on any PCB board at the top, and the second chopper switch tube S3 in the flyback conversion circuit is arranged on any PCB board at the top. In other words, the first chopper switch tube S1 and the second chopper switch tube S3 can be arranged on the same PCB board at the top, or on different PCB boards at the top. For example, Figure 10a As shown, the first chopper switch tube S1 and the second chopper switch tube S3 are both arranged on the top PCB board.

[0123] In this embodiment, the first switch tube S2 in the flyback conversion circuit is arranged on any PCB board at the bottom, and the input capacitor Cin in the flyback conversion circuit is arranged on any PCB board at the bottom. In other words, the first switch tube S2 and the input capacitor Cin can be arranged on the same PCB board at the bottom, or on different PCB boards at the bottom. For example, Figure 10c As shown, the first switch tube S2 and the input capacitor Cin are both arranged on the bottom PCB board.

[0124] The above is only one configuration method of other components in the flyback conversion circuit except the transformer T. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific situation, all of which are within the scope of protection of this application.

[0125] Another embodiment of the present application provides another implementation of a flyback converter. This implementation differs from the above implementation in that:

[0126] In this embodiment, the flyback converter circuit includes at least one output capacitor COUT, and each output capacitor COUT is arranged on any one of the top PCB boards. In other words, each output capacitor COUT can be arranged on the same top PCB board, or not all of them can be arranged on the same top PCB board. For example, Figure 10a As shown, the flyback converter circuit includes an output capacitor COUT, and the output capacitor COUT is arranged on the top PCB board.

[0127] It should be noted that if multiple capacitors with smaller capacitance are selected and connected in parallel as the output capacitor COUT, then Figure 10a As shown, multiple capacitors with smaller capacitance are connected in parallel.

[0128] The above is only one way to set the output capacitor COUT. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to specific circumstances, all of which are within the scope of protection of this application.

[0129] Another embodiment of the present application provides another implementation of a flyback converter. This implementation differs from the above implementation in that:

[0130] The flyback converter circuit includes an absorption module 20. The absorption module 20 includes an absorption resistor Rx, an absorption capacitor Cclamp, and a first diode D1. The absorption resistor Rx is set on any PCB board at the top, the absorption capacitor Cclamp is set on any PCB board at the bottom, and the first diode D1 is set on any PCB board at the bottom. For example, Figure 10aAs shown, the absorption resistor Rx is set on the top PCB board, as shown in Figure 10c As shown, the absorption capacitor Cclamp and the first diode D1 are both arranged on the bottom PCB board.

[0131] The above is only one configuration of the absorption module 20. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific situation, all of which are within the scope of protection of this application.

[0132] Another embodiment of the present application provides another implementation of a flyback converter. This implementation differs from the above implementation in that:

[0133] The flyback conversion circuit includes at least one anti-backward module 10, and each anti-backward module 10 is arranged on any of the top PCB boards. In other words, each anti-backward module 10 can be arranged on the same top PCB board, or not all of them can be arranged on the same top PCB board. For example, the flyback conversion circuit includes one anti-backward module 10, and the anti-backward module 10 is arranged on the top PCB board. If the anti-backward module 10 includes a second diode D2, then Figure 10a As shown, the second diode D2 is arranged on the top PCB board.

[0134] It should be noted that if the anti-reverse module 10 includes a second diode D2, and multiple diodes with smaller maximum currents are selected and connected in parallel as the second diode D2, then Figure 10a As shown, a plurality of diodes with smaller maximum currents allowed to flow therethrough are connected in parallel.

[0135] The above is only one configuration method of the anti-reverse module 10. In practical applications, including but not limited to this, no specific limitation is made here and it can be determined according to the specific situation, all of which are within the scope of protection of this application.

[0136] Another embodiment of the present application provides another implementation of a flyback converter. This implementation differs from the above implementation in that:

[0137] Except for the windings of the transformer T, other components arranged on each layer of the PCB are arranged at positions where the distance between them and the magnetic core 100 is less than a preset value.

[0138] If the distance to the magnetic core 100 is less than the preset value, it means that the distance to the magnetic core 100 is small, that is, the distance to the magnetic core 100 is close.

[0139] In this embodiment, since the distance between the core 100 and the magnetic core 100 is less than the preset value, which indicates that the distance to the core 100 is relatively close, other devices arranged on each layer of the PCB board, except for the winding of the transformer T, are arranged at a position relatively close to the core 100, thereby improving the coupling between the primary winding and the secondary winding.

[0140] Another embodiment of the present application provides a soft switch control method, which is applied to the flyback converter circuit provided in the above embodiment. The specific process of the soft switch control method is as follows: Figure 11 As shown, the specific steps include:

[0141] S110 , controlling the first chopper switch tube in the flyback conversion circuit to switch to the on state, the second chopper switch tube to switch to the on state, and the first switch tube to be in the off state.

[0142] by Figure 8 Taking the flyback conversion circuit shown in FIG. 1 as an example, the state switching process of the first chopper switch tube, the second chopper switch tube, and the first switch tube in the flyback conversion circuit is as follows: Figure 12 As shown. Step S110 is equivalent to Figure 12 Executed at time t0.

[0143] S120 , after a first preset time, controlling the first chopper switch tube to switch to an off state.

[0144] The first preset time is the time during which the first chopping switch tube and the second chopping switch tube perform chopping together. In practical applications, the first preset time is set according to actual conditions and is not specifically limited here.

[0145] by Figure 8 Taking the flyback conversion circuit shown in FIG. 1 as an example, the state switching process of the first chopper switch tube, the second chopper switch tube, and the first switch tube in the flyback conversion circuit is as follows: Figure 12 As shown. In step S120, controlling the first chopper switch to switch to the off state is equivalent to Figure 12 It is executed at time t1.

[0146] S130: Determine whether the junction capacitance of the first chopper switch tube is fully charged, and whether the junction capacitance of the first switch tube in the flyback conversion circuit is fully discharged.

[0147] If the junction capacitance of the first chopper switch tube is fully charged and the junction capacitance of the first switch tube in the flyback conversion circuit is fully discharged, steps S140 and S150 are executed in sequence; if the junction capacitance of the first chopper switch tube is not fully charged and / or the junction capacitance of the first switch tube in the flyback conversion circuit is not fully discharged, the process returns to step S130.

[0148] In a specific example, if it is determined that the voltage across the primary winding of the transformer in the flyback conversion circuit is equal to zero, it is determined that the junction capacitance of the first chopper switch tube is fully charged and the junction capacitance of the first switch tube is fully discharged.

[0149] The above example only shows one implementation of step S130. In practical applications, including but not limited to this, no specific limitation is made here and it may depend on the specific situation.

[0150] S140 , controlling the first switch tube to switch to the on state and the second chopper switch tube in the flyback conversion circuit to switch to the off state.

[0151] by Figure 8 Taking the flyback conversion circuit shown in FIG. 1 as an example, the state switching process of the first chopper switch tube, the second chopper switch tube, and the first switch tube in the flyback conversion circuit is as follows: Figure 12 As shown. Step S140 is equivalent to Figure 12 It is executed at time t2.

[0152] S150: Determine whether the junction capacitance of the second chopper switch tube is completely discharged.

[0153] If the junction capacitance of the second chopper switch tube is completely discharged, steps S160 and S170 are sequentially executed; if the junction capacitance of the second chopper switch tube is not completely discharged, the process returns to step S150 .

[0154] In a specific example, if it is determined that the voltage across the primary winding of the transformer in the flyback conversion circuit is zero and the current on the primary winding remains unchanged within the second preset time, it is determined that the junction capacitance of the second chopper switch tube is discharged.

[0155] The current on the primary winding remains unchanged during the second preset time, indicating that the current on the primary winding has reached stability. In practical applications, the second preset time is set according to actual conditions and is not specifically limited here.

[0156] The above example only shows one implementation of step S150. In practical applications, including but not limited to this, no specific limitation is made here and it may depend on the specific situation.

[0157] S160 , controlling the first switch tube to switch to the off state and the second chopper switch tube to switch to the on state.

[0158] by Figure 8 Taking the flyback conversion circuit shown in FIG. 1 as an example, the state switching process of the first chopper switch tube, the second chopper switch tube, and the first switch tube in the flyback conversion circuit is as follows: Figure 12 As shown. Step S160 is equivalent to Figure 12 It is executed at time t4 in the above example.

[0159] S170: Determine whether the junction capacitance of the first chopper switch tube is completely discharged, and whether the first switch tube is completely charged.

[0160] If the junction capacitance of the first chopper switch tube is discharged and the first switch tube is charged, step S180 is executed; if the junction capacitance of the first chopper switch tube is not discharged and / or the first switch tube is not charged, the process returns to step S170.

[0161] In a specific example, if it is determined that the voltage across the primary winding of the transformer in the flyback conversion circuit is equal to the voltage on the input side of the flyback conversion circuit, it is determined that the junction capacitance of the first chopper switch tube is discharged and the first switch tube is charged.

[0162] The above example only shows one implementation of step S170. In practical applications, including but not limited to this, no specific limitation is made here and it may depend on the specific situation.

[0163] S180: Determine whether to continue operating the flyback conversion circuit.

[0164] If the flyback conversion circuit is enabled to continue to operate, step S190 is executed and the process returns to step S120 ; if the flyback conversion circuit is not enabled to continue to operate, the process stops.

[0165] S190, controlling the first chopper switch tube to switch to the on state.

[0166] by Figure 8 Taking the flyback conversion circuit shown in FIG. 1 as an example, the state switching process of the first chopper switch tube, the second chopper switch tube, and the first switch tube in the flyback conversion circuit is as follows: Figure 12 As shown. Step S190 is equivalent to Figure 12 It is executed at time t5.

[0167] During the t0-t1 phase, the first chopper switch S1 is on, the second chopper switch S3 is on, and the first switch S2 is off. The voltage uab across the primary winding equals the voltage Uin at the input of the flyback converter circuit. The voltage ucd across the secondary winding equals Uin / n. The second diode D2 is reverse biased, the current is in the secondary winding is zero, and the current ip in the primary winding gradually increases at the rate of Uin / Lm. Here, n is the turns ratio of the transformer, and Lm is the magnetizing inductance.

[0168] During the period t1-t2, the first chopper switch S1 is in the off state, the second chopper switch S3 is in the on state, and the first switch S2 is in the off state. Since the current ip on the primary winding is greater than 0, the junction capacitance Coss_S1 of the first chopper switch S1 is gradually charged through Lr, Lm, Cin, and the second chopper switch S3, and the junction capacitance Coss_S2 of the first switch S2 is gradually discharged through Lr, Lm, and the second chopper switch S3. Therefore, the voltage uab across the primary winding and the voltage ucd across the secondary winding begin to decrease, and the current ip on the primary winding can be considered to remain unchanged. Until time t2, the charging and discharging of the junction capacitance Coss_S1 of the first chopper switch S1 and the junction capacitance Coss_S2 of the first chopper switch S2 are completed, and the voltage uab across the primary winding and the voltage ucd across the secondary winding decrease to 0. At this time, the second chopper switch S3 is turned off, and the first switch S2 is turned on.

[0169] During the t2-t3 phase, the first chopper switch S1 is off, the second chopper switch S3 is off, and the first switch S2 is on. Because the current ip in the primary winding is greater than 0, the soft switching capacitor Czvs and the junction capacitance Coss_S3 of the second chopper switch S3 are gradually charged through Lr, Lm, and the first switch S2. The junction capacitance Coss_D1 of the first diode D1 is gradually discharged through Lr, Lm, the absorption capacitor Cclamp, and the first switch S2. The voltage uab across the primary winding and the voltage ucd across the secondary winding continue to decrease until the voltage ucd across the secondary winding decreases to -Uout. It is then clamped by the output capacitor Cout and no longer changes. The voltage uab across the primary winding decreases to -Uout × n and is then clamped by the absorption capacitor Cclamp and no longer changes. The energy stored in the leakage inductor Lr is then released into the capacitor Cclamp through the first diode D1 and dissipated by the absorption resistor Rx. The energy stored in the magnetizing inductor Lm is transferred to the output capacitor Cout in a linear manner during this stage, so the current ip on the primary winding decays to 0, and the current is on the secondary winding first increases and then decreases linearly until the current is on the secondary winding decreases to 0 at time t3.

[0170] During the t3-t4 phase, the first chopper switch S1 is in the off state, the second chopper switch S3 is in the off state, and the first switch S2 is in the on state. Since the voltage across the soft switch capacitor Czvs and the second chopper switch S3's Coss_S3 is greater than 0 at this time, the soft switch capacitor Czvs, the junction capacitance Coss_S3 of the second chopper switch S3, and the junction capacitance Coss_D2 of the second diode D2 are gradually discharged through Lr, Lm, and the first switch S2. The junction capacitance Coss_D1 of the first diode D1 is gradually charged through Lr, Lm, Cclamp, and the first switch S2. Since the charging and discharging currents of these capacitors all flow through the primary winding, the current ip in the primary winding gradually decreases from t3, and the voltage uab across the primary winding and the voltage ucd across the secondary winding also slowly increase until both the voltage uab across the primary winding and the voltage ucd across the secondary winding rise from negative values ​​to 0, and the current ip in the primary winding reaches a stable value. The stable value of the current ip on the primary winding can be adjusted by adjusting the size of the soft switch capacitor Czvs.

[0171] During the t4-t5 phase, the first chopper switch S1 is in the off state, the second chopper switch S3 is in the on state, and the first switch S2 is in the off state. Because the current ip in the primary winding is negative, the junction capacitance Coss_S1 of the first chopper switch S1 is gradually discharged through Lr, Lm, Cin, and the second chopper switch S3, while the junction capacitance Coss_S2 of the first switch S2 is gradually charged through Lr, Lm, and the second chopper switch S3. As a result, the voltage uab across the primary winding and the voltage ucd across the secondary winding slowly rise from 0. At t5, the current ip in the primary winding returns to 0 again, and the voltage uab across the primary winding and the voltage ucd across the secondary winding also reach the stable values ​​Uin and Uin / n, respectively. The charge and discharge of the junction capacitance Coss_S1 of the first chopper switch S1 and the junction capacitance Coss_S2 of the first switch S2 are completed. One cycle ends, and the following is exactly the same as described above and will not be repeated here. Among them, by adjusting the size of the soft switching capacitor Czvs, the size of the stable value of the current ip on the primary winding can be adjusted, thereby adjusting the voltage change rate of the voltage uab at both ends of the primary winding and the voltage ucd at both ends of the secondary winding.

[0172] As can be seen from the above, the state switching of the first chopper switch tube S1 occurs at time t0 and time t1 respectively, and the junction capacitance Coss_S1 of the first chopper switch tube S1 has been discharged in the t4-t5 stage of the previous cycle. Therefore, soft switching of the first chopper switch tube S1 is achieved, thereby reducing the switching loss of the first chopper switch tube S1.

[0173] As can be seen from the above, the second chopper switch tube S3 is switched to the off state at time t2, and the junction capacitance Coss_S3 of the second chopper switch tube S3 has been fully discharged during the t2-t4 phase of the previous cycle, thereby achieving soft shutdown of the second chopper switch tube S1. The second chopper switch tube S3 is switched to the on state at time t4, and the junction capacitance Coss_S3 of the second chopper switch tube S3 has been fully discharged during the t2-t4 phase of the current cycle, thereby achieving soft switching of the second chopper switch tube S1. In summary, soft switching of the second chopper switch tube S2 is achieved, thereby reducing the switching loss of the second chopper switch tube S2.

[0174] As can be seen from the above, the state switching of the first switch tube S2 occurs at time t2 and time t4 respectively, and the junction capacitance Coss_S2 of the first switch tube S2 has been completely discharged during the t1-t2 period of this cycle. Therefore, soft switching of the first switch tube S2 is achieved, thereby reducing the switching loss of the first switch tube S2.

[0175] In summary, the soft switching control method realizes soft switching of each switch tube in the flyback conversion circuit, that is, each switch tube switches state when the voltage across itself is zero, thereby reducing the switching loss of each switch tube.

[0176] For the above description of the disclosed embodiments, the features recorded in each embodiment in this specification can be replaced or combined with each other, so that professional and technical personnel in this field can implement or use this application. The above description is only a preferred embodiment of the present utility model, and does not limit the present utility model in any form. Although the present utility model has been disclosed as above with a preferred embodiment, it is not used to limit the present utility model. Any technician familiar with the field can make many possible changes and modifications to the technical solution of the present utility model using the methods and technical contents disclosed above without departing from the scope of the technical solution of the present utility model, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present utility model without departing from the content of the technical solution of the present utility model still falls within the scope of protection of the technical solution of the present utility model.

Claims

1. A flyback converter circuit, characterized in that: include: Input capacitor, transformer, first target switch tube and two chopper switch tubes; wherein: The input end of the first chopper switch tube is connected to one end of the input capacitor, and the connection point serves as the first end of the input side of the flyback conversion circuit; The output end of the first chopper switch tube is connected to the input end of the second chopper switch tube through the primary winding of the transformer; The output end of the second chopper switch tube is connected to the other end of the input capacitor, and the connection point serves as the second end of the input side of the flyback conversion circuit; The input end of the first switch tube is connected to the output end of the first chopping switch tube, and the output end of the first switch tube is connected to the output end of the second chopping switch tube; The second chopper switch tube is in a conducting state when the other two switch tubes are in a turned-off state; The first switch tube is in the on state when the other two switch tubes are in the off state; Each switch tube switches state when its own junction capacitance is fully discharged.

2. The flyback converter circuit according to claim 1, wherein: Also includes: At least one anti-counterfeiting module; The transformer comprises at least one secondary winding; In at least one of the secondary windings, the first end of each of the secondary windings is respectively connected to the current output end of each of the anti-reverse modules, and the current input end of each of the anti-reverse modules serves as the corresponding end of the corresponding output side of the flyback conversion circuit; or, In at least one of the secondary windings, the second end of each of the secondary windings is connected to the current input end of each of the anti-reverse modules, and the current output end of each of the anti-reverse modules serves as the corresponding end of the corresponding output side of the flyback conversion circuit; The first end of each secondary winding is the same as the first end of the primary winding; the first end of the primary winding is the end of the primary winding connected to the output end of the first chopper switch tube.

3. The flyback converter circuit according to claim 2, wherein: The flyback conversion circuit further includes: at least one output capacitor; the output capacitor is provided between both ends of each secondary winding; and / or, The flyback conversion circuit further includes an absorption module; the current input end of the absorption module is connected to the input end of the second chopper switch tube, and the current output end of the absorption module is connected to the output end of the second chopper switch tube.

4. The flyback converter circuit according to claim 3, wherein: The absorption module includes: an absorption resistor, an absorption capacitor and a first diode; wherein: The anode of the first diode is connected to the input end of the second chopper switch tube; The cathode of the first diode is connected to one end of the absorption resistor and one end of the absorption capacitor respectively; The other end of the absorption resistor is connected to the other end of the absorption capacitor, and the connection point is connected to the output end of the second chopper switch tube.

5. The flyback converter circuit according to claim 2, wherein: Each of the anti-reverse modules includes: a second diode; in each of the anti-reverse modules: the anode of the second diode serves as the current input terminal of the anti-reverse module in which it is located, and the cathode of the second diode serves as the current output terminal of the anti-reverse module in which it is located; or, Each of the anti-reverse modules includes: a second switch tube; in each of the anti-reverse modules: a first end of the second switch tube serves as a current input end of the anti-reverse module, and a second end of the second switch tube serves as a current output end of the anti-reverse module; The first end of the second switch tube is an end connected to the anode of its own body diode on the second switch tube, and the second end of the second switch tube is an end connected to the cathode of its own body diode on the second switch tube.

6. The flyback converter circuit according to any one of claims 1 to 5, characterized in that: Also includes: Soft switching capacitor; where: One end of the soft switch capacitor is connected to the input end of the second chopper switch tube, and the other end of the soft switch capacitor is connected to the output end of the second chopper switch tube.

7. A flyback converter, characterized in that: include: At least two layers of PCB boards arranged side by side and the flyback converter circuit according to any one of claims 1 to 6; wherein: A through hole is provided on each layer of the PCB board, and the magnetic core of the transformer in the flyback conversion circuit passes through the through hole on each layer of the PCB board; The windings on the transformer are respectively arranged on each layer of the PCB board, and the windings arranged on each layer of the PCB board are wound along the through holes on each layer of the PCB board; Other components in the flyback conversion circuit are respectively arranged on the PCB boards of each layer.

8. The flyback converter according to claim 7, wherein: The primary winding of the transformer is divided into 2N groups, where N is a positive integer, and the 2N groups are symmetrically arranged on the N layers of PCB boards located at the top and the N layers of PCB boards located at the bottom; The transformer includes at least one secondary winding, and each secondary winding is respectively arranged on each layer of the PCB board located in the middle.

9. The flyback converter according to claim 8, wherein: The first chopper switch tube in the flyback conversion circuit is arranged on any one of the top layers of the PCB board; The second chopper switch tube in the flyback conversion circuit is arranged on any one of the top layers of the PCB board; The first switch tube in the flyback conversion circuit is arranged on any layer of the PCB board at the bottom; The input capacitor in the flyback conversion circuit is arranged on any layer of the PCB board located at the bottom.

10. The flyback converter according to claim 8, wherein: The flyback conversion circuit includes at least one output capacitor, and each of the output capacitors is arranged on any layer of the PCB board located at the top; and / or, The flyback conversion circuit includes an absorption module; the absorption module includes an absorption resistor, an absorption capacitor and a first diode; the absorption resistor is arranged on any layer of the PCB board located at the top; the absorption capacitor is arranged on any layer of the PCB board located at the bottom; the first diode is arranged on any layer of the PCB board located at the bottom; and / or, The flyback conversion circuit includes at least one anti-flyback module, and each of the anti-flyback modules is arranged on any one of the top layers of the PCB board.

11. The flyback converter according to any one of claims 7 to 10, characterized in that: Except for the windings of the transformer, other components arranged on each layer of the PCB board are arranged at a position where the distance between the components and the magnetic core is less than a preset value.

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