Flyback conversion circuit, flyback converter and soft switching control method
By optimizing the flyback converter circuit with a three-switch transistor structure and soft-switching control method, the problem of high switching losses is solved, and higher efficiency and lower noise electromagnetic compatibility performance are achieved, making it suitable for flyback converter applications.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-16
- Publication Date
- 2026-04-17
AI Technical Summary
Traditional flyback converter circuits suffer from significant switching losses in the switching transistors, leading to reduced efficiency and the potential generation of voltage and current spikes and oscillations, which affect electromagnetic compatibility performance. This problem is particularly pronounced when using next-generation semiconductor materials such as silicon carbide and gallium nitride.
A three-switch structure and soft-switching control method are adopted. By controlling the switching sequence of the switching transistors and the charging and discharging path of the junction capacitor, the switching loss is reduced, and the circuit performance is optimized through anti-reverse module, absorption module and soft-switching capacitor.
It effectively reduces the switching losses of the switching transistor, reduces voltage and current spikes, improves electromagnetic compatibility performance, and reduces the overall circuit loss and cost.
Smart Images
Figure CN121886953A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of power conversion technology, and in particular to a flyback converter circuit, a flyback converter, and a soft-switching control method. Background Technology
[0002] Currently, flyback converter circuits have advantages such as simple structure, few components, multiple outputs, easy control, and low cost, and are widely used in adapters, auxiliary power supplies, and other applications.
[0003] Traditional flyback converter circuits use only one switching transistor for chopping. However, this transistor hard-switches at the moment of turn-on, resulting in significant switching losses. This reduces the efficiency of the flyback converter and causes large voltage and current spikes and oscillations. Furthermore, it can lead to significant electromagnetic interference, affecting the electromagnetic compatibility (EMC) performance of the flyback converter. These problems are particularly pronounced when the switching transistor is made of next-generation semiconductor materials such as silicon carbide (SiC) and gallium nitride (GaN).
[0004] Therefore, how to reduce the switching losses of the switching transistors in the flyback converter circuit is a technical problem that urgently needs to be solved. Summary of the Invention
[0005] In view of this, the present invention provides a flyback converter circuit, a flyback converter, and a soft-switching control method to reduce the switching losses of the switching transistors in the flyback converter circuit.
[0006] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:
[0007] The first aspect of this application provides a flyback converter circuit, comprising: an input capacitor, a transformer, a first target switch transistor, and two chopper switches; wherein:
[0008] The input terminal of the first chopper switch is connected to one end of the input capacitor, and the connection point serves as the first terminal of the input side of the flyback converter circuit.
[0009] The output terminal of the first chopper switch is connected to the input terminal of the second chopper switch through the primary winding of the transformer;
[0010] The output terminal of the second chopper switch is connected to the other end of the input capacitor, and the connection point serves as the second terminal of the input side of the flyback converter circuit.
[0011] The input terminal of the first switching transistor is connected to the output terminal of the first chopper switching transistor, and the output terminal of the first switching transistor is connected to the output terminal of the second chopper switching transistor.
[0012] The second chopper switch is in the on state when the other two switches are in the off state;
[0013] The first switching transistor is in the on state when the other two switching transistors are in the off state.
[0014] Each switch transitions to a new state after its junction capacitance has been fully discharged.
[0015] Optionally, it may also include: at least one anti-reverse module;
[0016] The transformer includes at least one secondary winding;
[0017] In at least one of the secondary windings, the first end of each secondary winding is connected to the current output terminal of each anti-reverse module, and the current input terminal of each anti-reverse module serves as the corresponding terminal of the corresponding output side of the flyback converter circuit.
[0018] or,
[0019] In at least one of the secondary windings, the second end of each secondary winding is connected to the current input terminal of each anti-reverse module, and the current output terminal of each anti-reverse module serves as the corresponding terminal of the corresponding output side of the flyback converter circuit.
[0020] The first end of each of the secondary windings 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 that is connected to the output end of the first chopper switch.
[0021] Optionally, the flyback converter circuit further includes: at least one output capacitor; and the output capacitor is disposed between the two ends of each of the secondary windings;
[0022] And / or,
[0023] The flyback converter circuit further includes: an absorption module; the current input terminal of the absorption module is connected to the input terminal of the second chopper switch, and the current output terminal of the absorption module is connected to the output terminal of the second chopper switch.
[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 terminal of the second chopper switch.
[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 terminal of the second chopper switch.
[0028] Optionally, each of the anti-reverse modules includes: a second diode; in each anti-reverse module: the anode of the second diode serves as the current input terminal of the anti-reverse module to which it is located, and the cathode of the second diode serves as the current output terminal of the anti-reverse module to which it is located;
[0029] or,
[0030] Each of the anti-reverse modules includes: a second switch; in each anti-reverse module: the first end of the second switch serves as the current input terminal of the anti-reverse module to which it belongs, and the second end of the second switch serves as the current output terminal of the anti-reverse module to which it belongs;
[0031] The first end of the second switch is the end of the second switch connected to the anode of its own body diode, and the second end of the second switch is the end of the second switch connected to the cathode of its own body diode.
[0032] Optionally, it also includes: soft-switching capacitors; wherein:
[0033] One end of the soft-switching capacitor is connected to the input terminal of the second chopper switch, and the other end of the soft-switching capacitor is connected to the output terminal of the second chopper switch.
[0034] A second aspect of this application provides a flyback converter, comprising: at least two PCB layers arranged side-by-side and a flyback converter circuit as described in any one of the first aspects of this application; wherein:
[0035] Each layer of the PCB board has through holes, and the magnetic core of the transformer in the flyback converter circuit passes through the through holes 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] The other components in the flyback converter circuit are respectively mounted 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 top N layers of the PCB board and the bottom N layers of the PCB board, respectively.
[0039] The transformer includes at least one secondary winding, and each of the secondary windings is respectively disposed on the PCB board located in the middle.
[0040] Optionally, the first chopper switch in the flyback converter circuit is disposed on any of the top layers of the PCB board;
[0041] The second chopper switch in the flyback converter circuit is disposed on any of the top layers of the PCB board;
[0042] The first switching transistor in the flyback converter circuit is disposed on any layer of the PCB board located at the bottom.
[0043] The input capacitor in the flyback converter circuit is located on any layer of the PCB board at the bottom.
[0044] Optionally, the flyback converter circuit includes at least one output capacitor, each of which is disposed on any of the top layers of the PCB board;
[0045] And / or,
[0046] The flyback converter circuit includes an absorption module; the absorption module includes an absorption resistor, an absorption capacitor, and a first diode; the absorption resistor is disposed on any of the top layers of the PCB board; the absorption capacitor is disposed on any of the bottom layers of the PCB board; and the first diode is disposed on any of the bottom layers of the PCB board.
[0047] And / or,
[0048] The flyback converter circuit includes at least one anti-flyback module, and each anti-flyback module is disposed on any layer of the PCB board located at the top.
[0049] Optionally, apart from the transformer windings, other components on each layer of the PCB are positioned at a distance less than a preset value from the magnetic core.
[0050] A third aspect of this application provides a soft-switching control method applied to a flyback converter circuit as described in any of the first aspects of this application; the soft-switching control method includes:
[0051] The first chopper switch in the flyback converter circuit is switched to the on state, the second chopper switch is switched to the on state, and the first switch is in the off state.
[0052] After a first preset time, the first chopper switch is controlled to switch to the off state;
[0053] When the junction capacitance of the first chopper switch is fully charged and the junction capacitance of the first switch is fully discharged, the first switch is controlled to switch to the on state and the second chopper switch is controlled to switch to the off state.
[0054] When the junction capacitance of the second chopper switch is completely discharged, the first switch is controlled to switch to the off state and the second chopper switch is controlled to switch to the on state.
[0055] After the junction capacitance of the first chopper switch has been discharged and the first switch has been charged, determine whether to allow the flyback converter circuit to continue operating.
[0056] If the flyback converter circuit continues to operate, the first chopper switch is controlled to switch to the on state, and the process returns to the step of controlling the first chopper switch to switch to the off state after a first preset time.
[0057] Optionally, if the voltage across the primary winding of the transformer in the flyback converter circuit is zero, then the junction capacitance of the first chopper switch is fully charged and the junction capacitance of the first switch is fully discharged.
[0058] Optionally, if the voltage across the primary winding of the transformer in the flyback converter circuit is zero and the current in the primary winding remains unchanged for a second preset time, then the junction capacitance of the second chopper switch is discharged.
[0059] Optionally, if the voltage across the primary winding of the transformer in the flyback converter circuit is equal to the voltage on the input side of the flyback converter circuit, then the junction capacitance of the first chopper switch is discharged and the first switch is charged.
[0060] As can be seen from the above technical solution, the present invention provides a flyback converter circuit. From the connection relationship of the three switches, it is known that when the second chopper switch is in the on state and the other two switches are in the off state, the junction capacitances of both the first chopper switch and the first switch have charging and discharging paths. Furthermore, when the first switch is in the on state and the other two switches are in the off state, the junction capacitance of the second chopper switch has a charging and discharging path. Therefore, the junction capacitances of all three switches can be charged and discharged, thus ensuring that all three junction capacitances are fully discharged. Since each switch switches its state only after its own junction capacitance has been fully discharged—that is, when the voltage across each switch is zero—this flyback converter circuit can reduce the switching losses of its switches. Attached Figure Description
[0061] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.
[0062] Figures 1-9 These are schematic diagrams illustrating nine different implementations of the flyback converter circuit provided in this application.
[0063] Figure 10a This is a schematic diagram of the structure on the top PCB board of the flyback converter provided in the embodiments of this application;
[0064] Figure 10b This is a schematic diagram of the structure on the middle layer PCB of the flyback converter provided in the embodiments of this application;
[0065] Figure 10c This is a schematic diagram of the structure on the bottom PCB board of the flyback converter provided in the embodiments of this application;
[0066] Figure 11 A schematic flowchart illustrating the soft-switching control method provided in an embodiment of this application;
[0067] Figure 12 for Figure 8 The diagram shows the working process of the flyback converter circuit. Detailed Implementation
[0068] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.
[0069] In this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0070] To reduce the switching losses of the switching transistors in the flyback converter circuit, this application provides a flyback converter circuit, the specific structure of which is as follows: Figure 1 As shown, the components include: input capacitor Cin, transformer T, and three switching transistors. The specific connections between these components are as follows:
[0071] The input terminal of the first chopper switch S1 is connected to one end of the input capacitor Cin, and this connection point serves as the first terminal of the input side of the flyback converter circuit. The output terminal of the first chopper switch S1 is connected to the input terminal of the second chopper switch S3 through the primary winding of the transformer T. The output terminal of the second chopper switch S3 is connected to the other end of the input capacitor Cin, and this connection point serves as the second terminal of the input side of the flyback converter circuit. The first chopper switch S1 and the second chopper switch S3 first switch to the on state simultaneously, and then switch to the off state simultaneously, and this cycle repeats, that is, the first chopper switch S1 and the second chopper switch S3 perform chopping together.
[0072] Optional, such as Figure 1 As shown, the first chopper switch S1 can be a MOSFET. In practical applications, it may include, but is not limited to, other types of transistors. No specific limitation is made here. It may be determined according to the specific circumstances and is within the protection scope of this application.
[0073] It should be noted that, Figure 1 Coss_S1 in the figure represents the junction capacitance of the first chopper switch S1.
[0074] Optional, such as Figure 1 As shown, the second chopper switch S3 can be a MOSFET. In practical applications, it may include, but is not limited to, other types of transistors. No specific limitation is made here. It may be determined according to the specific circumstances and is within the protection scope of this application.
[0075] It should be noted that the connection method of the secondary winding of transformer T is the same as that of the secondary winding of transformer T in the existing flyback converter circuit, and will not be repeated here. Additionally, under normal circumstances, such as... Figure 1 As shown, the primary winding of transformer T can be equivalently represented as a series connection of leakage inductance and magnetizing inductance. Furthermore, Figure 1 Coss_S3 in the figure represents the junction capacitance of the second chopper switch S3.
[0076] As can be seen from the above, the first chopper switch S1 and the second chopper switch S3 together perform chopping. Furthermore, the connection method of the secondary winding of the transformer T in the flyback converter circuit provided in this embodiment is the same as the connection method of the secondary winding of the transformer T in the flyback converter circuit in the prior art. Therefore, the flyback converter circuit provided in this embodiment conforms to the working principle of flyback conversion, and thus the flyback converter circuit provided in this embodiment can realize flyback conversion.
[0077] The input terminal of the first switch S2 is connected to the output terminal of the first chopper switch S1, and the output terminal of the first switch S2 is connected to the output terminal of the second chopper switch S3.
[0078] Optional, such as Figure 1 As shown, the first switching transistor S2 can be a MOSFET. In practical applications, it may include, but is not limited to, other transistors. No specific limitation is made here. It can be determined according to the specific situation and is within the protection scope of this application.
[0079] It should be noted that, Figure 1 Coss_S2 in the figure represents the junction capacitance of the first switching transistor S2.
[0080] The second chopper switch S3 is in the on state when the other two switches are both off. Figure 1 It can be seen that when the second chopper switch S3 is in the on state and the other two switches are in the off state, the junction capacitance of the first chopper switch S1 forms a circuit with the input capacitance Cin and the second chopper switch S3, the leakage inductance, and the magnetizing inductance. The junction capacitance of the first switch S2 forms a circuit with the second chopper switch S3, the leakage inductance, and the magnetizing inductance. Therefore, under this condition, both the junction capacitance of the first chopper switch S1 and the junction capacitance of the first switch S2 have charging and discharging paths.
[0081] The first switch S2 is in the on state when the other two switches are both off. Figure 1 It can be seen that when the first switch S2 is in the on state and the other two switches are in the off state, the junction capacitance of the second chopper switch S3 forms a circuit with the leakage inductance and the magnetizing inductance through the first switch S2. Therefore, under this condition, the junction capacitance of the second chopper switch S3 has a charging and discharging path.
[0082] It should be noted that how the junction capacitance of the three switching transistors is charged and discharged will be explained in detail in the following embodiments, and will not be repeated here.
[0083] Each switch transitions to a new state after its junction capacitance has been fully discharged.
[0084] It should be noted that how to achieve state switching for each switch after its own junction capacitance has been discharged will be explained in detail in the following embodiments, and will not be repeated here.
[0085] As described above, when the second chopper switch S3 is in the ON state and the other two switches are in the OFF state, the junction capacitances of both the first chopper switches S1 and S2 have charging and discharging paths. Furthermore, when the first switch S2 is in the ON state and the other two switches are in the OFF state, the junction capacitance of the second chopper switch S3 has a charging and discharging path. Therefore, the junction capacitances of all three switches can be charged and discharged, resulting in all three junction capacitances being fully discharged. Since each switch switches its state only after its own junction capacitance has been fully discharged—that is, when the voltage across its terminals is zero—this flyback converter circuit can reduce the switching losses of its individual switches.
[0086] Another embodiment of this application provides another implementation of the flyback converter circuit, the specific structure of which is as follows: Figure 1 , Figure 2 or Figure 3 As shown. In this embodiment, the transformer T includes at least one secondary winding and is provided with at least one anti-reverse module 10.
[0087] In a specific example, such as Figure 1 or Figure 3 As shown, in at least one secondary winding, the first end of each secondary winding is connected to the current output terminal of each anti-reverse module 10, and the current input terminal of each anti-reverse module 10 serves as the corresponding terminal of the corresponding output side of the flyback converter circuit.
[0088] For example, transformer T includes two secondary windings, and the flyback converter circuit includes two anti-reverse modules 10. The first end of the first secondary winding is connected to the current output terminal of the first anti-reverse module, and the current input terminal of the first anti-reverse module serves as the first terminal of the first output side of the flyback converter circuit. The second end of the first secondary winding serves as the second terminal of the first output side of the flyback converter circuit. The first end of the second secondary winding is connected to the current output terminal of the second anti-reverse module, and the current input terminal of the second anti-reverse module serves as the first terminal of the second output side of the flyback converter circuit. The second end of the second secondary winding serves as the second terminal of the second output side of the flyback converter circuit.
[0089] The reverse current protection module 10 is a module that allows current to flow into and out from only one end. Specifically, the current input terminal of the reverse current protection module 10 refers to the port on the module that allows current to flow in, and the current output terminal refers to the port on the module that allows current to flow out. For example, assuming that current flows into the reverse current protection module 10 from its first terminal and out from its second terminal, then the first terminal of the reverse current protection module 10 is its current input terminal, and the second terminal is its current output terminal.
[0090] 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 terminal of the first chopper switch S1.
[0091] In another specific example, such as Figure 2 As shown, in at least one secondary winding, the second end of each secondary winding is connected to the current input terminal of each anti-reverse module 10, and the current output terminal of each anti-reverse module 10 serves as the corresponding terminal of the corresponding output side of the flyback converter circuit.
[0092] For example, transformer T includes two secondary windings, and flyback converter circuit includes two anti-reverse modules 10. The first end of the first secondary winding serves as the first terminal of the first output side of the flyback converter circuit, and the second end of the first secondary winding is connected to the current input terminal of the first anti-reverse module. The current output terminal of the first anti-reverse module serves as the second terminal of the first output side of the flyback converter circuit. The first end of the second secondary winding serves as the first terminal of the second output side of the flyback converter circuit, and the second end of the second secondary winding is connected to the current input terminal of the second anti-reverse module. The current output terminal of the second anti-reverse module serves as the second terminal of the second output side of the flyback converter circuit.
[0093] It should be noted that the anti-reverse module 10, the current input terminal of the anti-reverse module 10, the current output terminal of the anti-reverse module 10, and the first terminal of each secondary winding are the same as in the example above, and will not be repeated here.
[0094] The two examples above illustrate two connection methods for each secondary winding. No specific limitations are made here, and the choice can be made depending on the specific circumstances. All of these are within the scope of protection of this application.
[0095] Taking the secondary winding of a transformer T as an example, as shown in the two examples above, when both the first chopper switch S1 and the second chopper switch S3 are switched to the on state, the current induced in the secondary winding flows into its second terminal and out of its first terminal. Therefore, the current induced in the secondary winding cannot flow through the corresponding anti-reverse module 10, resulting in no current on the output side of the flyback converter circuit. When both the first chopper switch S1 and the second chopper switch S3 are switched to the off state, the current induced in the secondary winding flows into its first terminal and out of its second terminal. Therefore, the current induced in the secondary winding can flow through the corresponding anti-reverse module 10, resulting in current on the output side of the flyback converter circuit. In summary, the connection method of the secondary winding conforms to the working principle of flyback converter, therefore, the flyback converter circuit provided in this embodiment can realize flyback converter.
[0096] Another embodiment of this application provides another implementation of the flyback converter circuit, the specific structure of which is as follows: Figure 4 or Figure 5As shown, this embodiment, based on the above embodiment, further includes at least one output capacitor COUT. The connection relationships between the various devices are described in detail below:
[0097] An output capacitor COUT is provided between the two ends of each secondary winding. In practical applications, a capacitor with a larger capacitance value can be directly selected as the output capacitor COUT, or multiple capacitors with smaller capacitance values can be connected in parallel as the output capacitor COUT.
[0098] Since the output capacitor COUT is located between the two ends of the secondary winding, it can clamp the voltage across the secondary winding, thus preventing overvoltage from occurring on the load connected to the secondary winding. This reduces the possibility of damage to the load connected to the secondary winding and improves the safety performance of the flyback converter circuit.
[0099] Another embodiment of this application provides another implementation of the flyback converter circuit, the specific structure of which is as follows: Figure 6 or Figure 7 As shown, this embodiment, based on the above embodiment, further includes an absorption module 20. The connection relationship between these devices is specifically described below:
[0100] The current input terminal of the absorption module 20 is connected to the input terminal of the second chopper switch S3, and the current output terminal of the absorption module 20 is connected to the output terminal of the second chopper switch S3.
[0101] 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 terminals of the second chopper switch S3, thus avoiding overvoltage of the second chopper switch S3, thereby reducing the possibility of damage to the second chopper switch S3 and improving the safety performance of the flyback converter circuit.
[0102] Another embodiment of this application provides a specific implementation of the absorption module 20, the specific structure of which is as follows: Figure 6 or Figure 7 As shown, it specifically includes: an absorption resistor Rx, an absorption capacitor Cclamp, and a first diode D1. The connection relationships between the components are as follows:
[0103] 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 the absorption resistor Rx and one end of the absorption capacitor Cclamp. 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.
[0104] It should be noted that, Figure 6 or Figure 7Coss_D1 in the figure represents the junction capacitance of the first diode D1.
[0105] As can be seen from the above connection relationship, this embodiment of the absorption module 20 is an RCD absorption circuit. The RCD absorption circuit is already very mature in the prior art, and its working principle will not be described in detail here.
[0106] Another embodiment of this application provides a specific implementation of the anti-reverse module 10, applicable to each anti-reverse module 10. The specific structure of this implementation is as follows: Figures 1-5 or Figure 7 As shown, it specifically includes: the second diode D2.
[0107] The anode of the second diode D2 serves as the current input terminal of the reverse protection module 10, and the cathode of the second diode D2 serves as the current output terminal of the reverse protection module 10. In practical applications, a diode with a larger maximum allowable current can be directly selected as the second diode D2, or multiple diodes with smaller maximum allowable currents can be connected in parallel as the second diode D2.
[0108] It should be noted that using diodes to limit the current direction, i.e., to achieve reverse polarity protection, is a mature technology, and its specific principles will not be explained in detail here. Additionally, Figures 1-5 or Figure 7 Coss_D2 in the figure represents the junction capacitance of the second diode D2.
[0109] Another embodiment of this application provides another specific implementation of the anti-reverse module 10, applicable to each anti-reverse module 10. The specific structure of this implementation is as follows: Figure 6 As shown, it specifically includes: the second switch S4.
[0110] The first terminal of the second switch S4 serves as the current input terminal of the anti-reverse module 10 to which it belongs, and the second terminal of the second switch S4 serves as the current output terminal of the anti-reverse module 10 to which it belongs.
[0111] Wherein, the first end of the second switch S4 is the end of the second switch S4 connected to the anode of its own body diode, and the second end of the second switch S4 is the end of the second switch S4 connected to the cathode of its own body diode.
[0112] It should be noted that, Figure 6 Coss_S4 in the figure represents the junction capacitance of the second switching transistor S4.
[0113] Optional, such as Figure 6As shown, the second switch S4 can be a MOSFET. In practical applications, it may include, but is not limited to, other types of transistors. No specific limitation is made here. It may be determined according to the specific circumstances and is within the protection scope of this application.
[0114] As described above, the anode of the body diode of the second switching transistor S4 serves as the current input terminal of the reverse protection module 10, and the cathode of the body diode of the second switching transistor S4 serves as the current output terminal of the reverse protection module 10. Therefore, this embodiment of the reverse protection module 10 is equivalent to a diode. Furthermore, since using a diode to limit the current direction, i.e., to achieve the reverse protection function, is already a mature technology, its specific principle will not be explained in detail here.
[0115] Additionally, if the maximum current that the body diode can withstand when forward biased is small, making it impossible for the second switch S4 to meet the actual current demand, then the second switch S4 can be switched to meet the actual current demand. The specific method for switching the state of the second switch S4 is as follows: when both the first chopper switch S1 and the second chopper switch S3 are simultaneously switched to the ON state, the second switch S4 switches to the OFF state; when both the first chopper switch S1 and the second chopper switch S3 are simultaneously switched to the OFF state, the second switch S4 switches to the ON state.
[0116] As can be seen from the above, the second switch S4 switches to the conducting state when its own body diode is forward biased, which can increase the current carrying capacity of the second switch S4 when its own body diode is forward biased, thereby increasing the possibility that the second switch S4 can meet the actual current requirements.
[0117] Another embodiment of this application provides another implementation of the flyback converter 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 devices is specifically described below:
[0118] One end of the soft-switching capacitor CZVS is connected to the input terminal of the second chopper switch S3, and the other end of the soft-switching capacitor CZVS is connected to the output terminal of the second chopper switch S3. That is, the soft-switching capacitor CZVS is connected in parallel with the junction capacitance of the second chopper switch S3.
[0119] Since the soft-switching capacitor CZVS is connected in parallel with the junction capacitance of the second chopper switch S3, the value of the junction capacitance of the second chopper switch S3 when the discharge current is stable can be adjusted by adjusting the capacitance value of the soft-switching capacitor CZVS.
[0120] Another embodiment of this application provides a flyback converter, the specific structure of which is as follows: Figures 10a-10cAs shown, it specifically includes: at least two PCB layers, and a flyback converter circuit as provided in the above embodiments of this application.
[0121] The PCBs on each layer are arranged side by side.
[0122] Through holes are provided on each PCB layer, and the magnetic core 100 of the transformer T in the flyback converter circuit passes through the through holes on each PCB layer.
[0123] The windings of transformer T are respectively set on each layer of PCB board, and the windings on each layer of PCB board are wound along the through holes on each layer of PCB board. The windings of transformer T include primary windings and all secondary windings.
[0124] Other components in the flyback converter circuit are mounted on the respective PCB layers.
[0125] Electrical connection between any two PCB layers is achieved via a 200-hole via. Since this method of electrical connection between any two PCB layers is already well-established in existing technology, it will not be described in detail here.
[0126] In this embodiment, since the PCBs are arranged side-by-side and the core 100 of the transformer T passes through through-holes on each PCB, the windings on each PCB are wound along the through-holes on their respective layers, thus achieving the transformer function of the transformer T. Furthermore, this arrangement of the transformer T reduces its size, thereby reducing the size of the flyback converter and lowering its overall cost. This also allows the flyback converter to be applied in more scenarios.
[0127] Another embodiment of this application provides another implementation of the flyback converter, which differs from the above-described implementation in that:
[0128] In this embodiment, the primary winding of transformer T is divided into 2N groups, where N is a positive integer. These 2N groups are symmetrically arranged on the top N-layer PCB board and the bottom N-layer PCB board, respectively. For example, as... Figures 10a-10c As shown, the number of layers of the PCB board is 3, which are respectively denoted 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 of 01 and 02, which are respectively set on the top PCB board and the bottom PCB board.
[0129] In this embodiment, the transformer T includes at least one secondary winding, and each secondary winding is respectively disposed on a PCB board located in the middle. For example, as Figure 10b As shown, transformer T includes a secondary winding 03, which is mounted on the middle layer PCB board.
[0130] In this embodiment, since the primary winding of transformer T is divided into multiple groups and set on different PCB boards, the area of each PCB board is reduced, thus making the structure of flyback transformer T more symmetrical, thereby reducing the volume of flyback converter and reducing the overall cost of flyback converter. This also allows flyback converter to be applied in more scenarios.
[0131] Another embodiment of this application provides another implementation of the flyback converter, which differs from the above-described implementation in that:
[0132] In this embodiment, the first chopper switch S1 in the flyback converter circuit is disposed on any of the top layers of the PCB board, and the second chopper switch S3 in the flyback converter circuit is disposed on any of the top layers of the PCB board. In other words, the first chopper switch S1 and the second chopper switch S3 can be disposed on the same top layer of the PCB board, or they can be disposed on different top layers of the PCB board. For example, ... Figure 10a As shown, the first chopper switch S1 and the second chopper switch S3 are both mounted on the top PCB board.
[0133] In this embodiment, the first switch S2 in the flyback converter circuit is disposed on any layer of the PCB board located at the bottom, and the input capacitor Cin in the flyback converter circuit is disposed on any layer of the PCB board located at the bottom. In other words, the first switch S2 and the input capacitor Cin can be disposed on the same layer of the PCB board located at the bottom, or they can be disposed on different layers of the PCB board located at the bottom. For example, as Figure 10c As shown, the first switching transistor S2 and the input capacitor Cin are both located on the bottom PCB board.
[0134] The above is only one arrangement of other devices in the flyback converter circuit besides the transformer T. In practical applications, there are other arrangements, including but not limited to this. No specific limitation is made here. It can be determined according to the specific situation, and all are within the protection scope of this application.
[0135] Another embodiment of this application provides another implementation of the flyback converter, which differs from the above-described implementation in that:
[0136] In this embodiment, the flyback converter circuit includes at least one output capacitor COUT, and each output capacitor COUT is disposed on any of the top layers of the PCB board. In other words, all output capacitors COUT can be disposed on the same top layer of the PCB board, or they can not all be disposed on the same top layer of the PCB board. For example, as Figure 10a As shown, the flyback converter circuit includes an output capacitor COUT, which is mounted on the top PCB board.
[0137] It should be noted that if multiple capacitors with small capacitance values are connected in parallel as the output capacitor COUT, then as follows: Figure 10a As shown, multiple capacitors with small capacitance values are connected in parallel.
[0138] The above is only one way to set the output capacitor COUT. In practical applications, there are other methods, including but not limited to this one. No specific limitation is made here. It can be determined according to the specific situation, and all of them are within the protection scope of this application.
[0139] Another embodiment of this application provides another implementation of the flyback converter, which differs from the above-described implementation in that:
[0140] 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 disposed on any of the top PCB layers, the absorption capacitor Cclamp is disposed on any of the bottom PCB layers, and the first diode D1 is disposed on any of the bottom PCB layers. For example, as... Figure 10a As shown, the absorption resistor Rx is set on the top PCB board, as... Figure 10c As shown, the absorption capacitor Cclamp and the first diode D1 are both mounted on the bottom PCB board.
[0141] The above is only one configuration of the absorption module 20. In practical applications, there are other configurations, including but not limited to this one. No specific limitation is made here. It can be determined according to the specific situation, and all are within the protection scope of this application.
[0142] Another embodiment of this application provides another implementation of the flyback converter, which differs from the above-described implementation in that:
[0143] The flyback converter circuit includes at least one anti-reverse module 10, each of which is disposed on any layer of the PCB board located at the top. In other words, the anti-reverse modules 10 can be disposed on the same layer of the PCB board at the top, or not all of them can be disposed on the same layer of the PCB board at the top. For example, the flyback converter circuit includes one anti-reverse module 10, which is disposed on the top layer PCB board. If the anti-reverse module 10 includes a second diode D2, then... Figure 10a As shown, the second diode D2 is mounted on the top PCB board.
[0144] It should be noted that if the anti-reverse module 10 includes a second diode D2, and multiple diodes with smaller maximum allowable currents are connected in parallel as the second diode D2, then as follows: Figure 10a As shown, multiple diodes with smaller maximum allowable currents are connected in parallel.
[0145] The above is only one way of setting the anti-reverse module 10. In practical applications, there are other methods, including but not limited to this one. No specific limitation is made here. It can be determined according to the specific situation. All of them are within the protection scope of this application.
[0146] Another embodiment of this application provides another implementation of a flyback converter, which differs from the above-described implementation in that:
[0147] Apart from the windings of transformer T, all other components on each PCB layer are positioned at a distance less than a preset value from the magnetic core 100.
[0148] The distance between the object and the magnetic core 100 is less than the preset value, indicating that the distance between the object and the magnetic core 100 is small, that is, the object is close to the magnetic core 100.
[0149] In this embodiment, since the distance between the device and the magnetic core 100 is less than a preset value, it indicates that the device is close to the magnetic core 100. Therefore, except for the winding of the transformer T, other devices on each PCB board are placed in positions close to the magnetic core 100, thereby improving the coupling between the primary winding and the secondary winding.
[0150] Another embodiment of this application provides a soft-switching control method applied to the flyback converter circuit provided in the above embodiments. The specific flow of this soft-switching control method is as follows: Figure 11 As shown, the specific steps include:
[0151] S110 controls the first chopper switch in the flyback converter circuit to be switched to the on state, the second chopper switch to be switched to the on state, and the first switch to be switched to the off state.
[0152] by Figure 8 Taking the flyback converter circuit shown as an example, the state switching process of the first chopper switch, the second chopper switch, and the first switch in the flyback converter circuit is as follows: Figure 12 As shown. Step S110 is equivalent to... Figure 12 It is executed at time t0.
[0153] S120. After the first preset time, control the first chopper switch to switch to the off state.
[0154] The first preset time is the time during which the first chopper switch and the second chopper switch perform chopping together. In practical applications, the first preset time is set according to the actual situation and is not specifically limited here.
[0155] by Figure 8 Taking the flyback converter circuit shown as an example, the state switching process of the first chopper switch, the second chopper switch, and the first switch in the flyback converter circuit is as follows: Figure 12As shown. In step S120, controlling the first chopper switch to the off state is equivalent to... Figure 12 Executed at time t1.
[0156] S130. Determine whether the junction capacitance of the first chopper switch is fully charged and whether the junction capacitance of the first switch in the flyback converter circuit is fully discharged.
[0157] If the junction capacitance of the first chopper switch is fully charged and the junction capacitance of the first switch in the flyback converter circuit is fully discharged, then steps S140 and S150 are executed sequentially; if the junction capacitance of the first chopper switch is not fully charged and / or the junction capacitance of the first switch in the flyback converter circuit is not fully discharged, then the process returns to step S130.
[0158] In a specific example, if it is determined that the voltage across the primary winding of the transformer in the flyback converter circuit is equal to zero, then it is determined that the junction capacitance of the first chopper switch is fully charged and the junction capacitance of the first switch is fully discharged.
[0159] The above example only shows one implementation of step S130. In practical applications, there are other implementations, including but not limited to this one. No specific limitation is made here, and the specific implementation can be determined according to the specific circumstances.
[0160] S140, control the first switch to the on state and the second chopper switch in the flyback converter circuit to the off state.
[0161] by Figure 8 Taking the flyback converter circuit shown as an example, the state switching process of the first chopper switch, the second chopper switch, and the first switch in the flyback converter circuit is as follows: Figure 12 As shown. Step S140 is equivalent to... Figure 12 The execution occurs at time t2.
[0162] S150. Determine whether the junction capacitance of the second chopper switch has been completely discharged.
[0163] If the junction capacitance of the second chopper switch is completely discharged, then steps S160 and S170 are executed sequentially; if the junction capacitance of the second chopper switch is not completely discharged, then the process returns to step S150.
[0164] In a specific example, if it is determined that the voltage across the primary winding of the transformer in the flyback converter circuit is equal to zero and the current on the primary winding remains unchanged within a second preset time, then it is determined that the junction capacitance of the second chopper switch has been discharged.
[0165] If the current in the primary winding remains constant within the second preset time period, it indicates that the current in the primary winding has reached a stable state. In practical applications, the second preset time period is set according to the actual situation and is not specifically limited here.
[0166] The above example only shows one implementation of step S150. In practical applications, it includes, but is not limited to, this. No specific limitation is made here, and it can be determined according to the specific situation.
[0167] S160, control the first switch to the off state and the second chopper switch to the on state.
[0168] by Figure 8 Taking the flyback converter circuit shown as an example, the state switching process of the first chopper switch, the second chopper switch, and the first switch in the flyback converter circuit is as follows: Figure 12 As shown. Step S160 is equivalent to... Figure 12 Executed at time t4.
[0169] S170. Determine whether the junction capacitance of the first chopper switch transistor has been completely discharged and whether the first switch transistor has been completely charged.
[0170] If the junction capacitance of the first chopper switch is completely discharged and the first switch is completely charged, then step S180 is executed; if the junction capacitance of the first chopper switch is not completely discharged and / or the first switch is not completely charged, then the process returns to step S170.
[0171] In a specific example, if it is determined that the voltage across the primary winding of the transformer in the flyback converter circuit is equal to the voltage on the input side of the flyback converter circuit, then it is determined that the junction capacitance of the first chopper switch has been discharged and the first switch has been charged.
[0172] The above example only shows one implementation of step S170. In practical applications, there are other implementations, including but not limited to this one. No specific limitation is made here, and the specific implementation can be determined according to the specific circumstances.
[0173] S180: Determine whether to allow the flyback converter circuit to continue operating.
[0174] If the flyback converter circuit continues to operate, then step S190 is executed, and the process returns to step S120; if the flyback converter circuit does not continue to operate, then execution stops.
[0175] S190, control the first chopper switch to switch to the on state.
[0176] by Figure 8 Taking the flyback converter circuit shown as an example, the state switching process of the first chopper switch, the second chopper switch, and the first switch in the flyback converter circuit is as follows: Figure 12 As shown. Step S190 is equivalent to... Figure 12 It is executed at time t5.
[0177] During the t0-t1 phase, the first chopper switch S1 is in the ON state, the second chopper switch S3 is in the ON state, and the first switch S2 is in the OFF state. The voltage uab across the primary winding is equal to the input voltage Uin of the flyback converter circuit, the voltage ucd across the secondary winding is equal to Uin / n, the second diode D2 is reverse biased, the current is in the secondary winding is 0, and the current ip in the primary winding gradually increases at a rate of change of Uin / Lm. Here, n is the turns ratio of the transformer, and Lm is the magnetizing inductance.
[0178] During the t1-t2 phase, the first chopper switch S1 is off, the second chopper switch S3 is on, and the first switch S2 is off. 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. 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. The current ip on the primary winding can be considered to remain unchanged until time t2, when the charging and discharging of the junction capacitances Coss_S1 of the first chopper switch S1 and Coss_S2 of the first switch S2 ends, 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 off, and the first switch S2 is on.
[0179] 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. Since the current ip on 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, at which point it is clamped by the output capacitor Cout and no longer changes. The voltage uab across the primary winding decreases to -Uout×n, at which point it is clamped by the absorption capacitor Cclamp and no longer changes. After this, the energy stored in the leakage inductor Lr is released into the capacitor Cclamp through the first diode D1 and consumed 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. As a result, the current ip on the primary winding decays to 0, and the current is on the secondary winding first rises and then decreases linearly until the current is on the secondary winding decreases to 0 at time t3.
[0180] During the t3-t4 stage, the first chopper switch S1 is off, the second chopper switch S3 is off, and the first switch S2 is on. Since the voltage across the soft-switching capacitor Czvs and the Coss_S3 of the second chopper switch S3 is greater than 0, the soft-switching 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. Because 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 onwards. The voltage uab across the primary winding and the voltage ucd across the secondary winding also slowly increase until both voltage uab and ucd rise from negative values to 0, and the current ip in the primary winding reaches a stable value. The stability of the current ip on the primary winding can be adjusted by changing the size of the soft-switching capacitor Czvs.
[0181] During the t4-t5 phase, the first chopper switch S1 is off, the second chopper switch S3 is on, and the first switch S2 is off. Since the current ip on 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. Conversely, the junction capacitance Coss_S2 of the first switch S2 is gradually charged through Lr, Lm, and the second chopper switch S3. Consequently, the voltage uab across the primary winding and the voltage ucd across the secondary winding slowly rise from 0. At t5, the current ip on the primary winding returns to 0, and the voltage uab across the primary winding and the voltage ucd across the secondary winding reach their stable values Uin and Uin / n, respectively. The charging and discharging of the junction capacitances Coss_S1 and Coss_S2 of the first chopper switch S1 and the first switch S2 ends. One cycle ends, and subsequent cycles follow the same pattern as described above, without further explanation. By adjusting the size of the soft-switching capacitor Czvs, the stable value of the current ip on the primary winding can be adjusted, thereby adjusting the voltage change rate of the voltage uab across the primary winding and the voltage ucd across the secondary winding.
[0182] As can be seen from the above, the state switching of the first chopper switch S1 occurs at time t0 and time t1 respectively. The junction capacitance Coss_S1 of the first chopper switch S1 has been discharged completely in the t4-t5 stage of the previous cycle. Therefore, the soft switching of the first chopper switch S1 is realized, thereby reducing the switching loss of the first chopper switch S1.
[0183] As described above, the second chopper switch S3 switches to the off state at time t2, and its junction capacitance Coss_S3 has already discharged completely during the t2-t4 phase of the previous cycle, thus achieving soft turn-off of the second chopper switch S1. The second chopper switch S3 switches to the on state at time t4, and its junction capacitance Coss_S3 has already discharged completely during the t2-t4 phase of the current cycle, thus achieving soft turn-on of the second chopper switch S1. In summary, soft switching of the second chopper switch S2 is achieved, thereby reducing its switching losses.
[0184] As can be seen from the above, the state switching of the first switch S2 occurs at time t2 and time t4 respectively. The junction capacitance Coss_S2 of the first switch S2 has been discharged completely in the t1-t2 stage of this cycle. Therefore, the soft switching of the first switch S2 is realized, thereby reducing the switching loss of the first switch S2.
[0185] In summary, this soft-switching control method achieves soft switching for each switch in the flyback converter circuit, meaning that each switch switches its state when the voltage across its terminals is zero, thus reducing the switching losses of each switch.
[0186] The features described above in the disclosed embodiments can be substituted or combined with each other, enabling those skilled in the art to implement or use this application. The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention using the methods and techniques disclosed above, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the present invention's technical solutions still fall within the protection scope of the present invention.
Claims
1. A flyback conversion circuit, characterized by, include: Input capacitor, transformer, first target switch transistor, and two chopper switches; wherein: The input terminal of the first chopper switch is connected to one end of the input capacitor, and the connection point serves as the first terminal of the input side of the flyback converter circuit. The output terminal of the first chopper switch is connected to the input terminal of the second chopper switch through the primary winding of the transformer; The output terminal of the second chopper switch is connected to the other end of the input capacitor, and the connection point serves as the second terminal of the input side of the flyback converter circuit. The input terminal of the first switching transistor is connected to the output terminal of the first chopper switching transistor, and the output terminal of the first switching transistor is connected to the output terminal of the second chopper switching transistor. The second chopper switch is in the on state when the other two switches are in the off state; The first switching transistor is in the on state when the other two switching transistors are in the off state. Each switch transitions to a new state after its junction capacitance has been fully discharged.
2. The flyback conversion circuit of claim 1, wherein, Also includes: At least one anti-reverse module; The transformer includes at least one secondary winding; In at least one of the secondary windings, the first end of each secondary winding is connected to the current output terminal of each anti-reverse module, and the current input terminal of each anti-reverse module serves as the corresponding terminal of the corresponding output side of the flyback converter circuit. or, In at least one of the secondary windings, the second end of each secondary winding is connected to the current input terminal of each anti-reverse module, and the current output terminal of each anti-reverse module serves as the corresponding terminal of the corresponding output side of the flyback converter circuit. The first end of each of the secondary windings is the same name as the first end of the primary winding; the first end of the primary winding is the end of the primary winding that is connected to the output terminal of the first chopper switch.
3. The flyback conversion circuit of claim 2, wherein, The flyback converter circuit further includes: at least one output capacitor; and the output capacitor is disposed between the two ends of each of the secondary windings. And / or, The flyback converter circuit further includes: an absorption module; the current input terminal of the absorption module is connected to the input terminal of the second chopper switch, and the current output terminal of the absorption module is connected to the output terminal of the second chopper switch.
4. The flyback converter circuit according to claim 3, characterized in that, 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 terminal of the second chopper switch. 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 terminal of the second chopper switch.
5. The flyback converter circuit according to claim 2, characterized in that, Each of the anti-reverse modules includes: a second diode; in each anti-reverse module: the anode of the second diode serves as the current input terminal of the anti-reverse module to which it is located, and the cathode of the second diode serves as the current output terminal of the anti-reverse module to which it is located; or, Each of the anti-reverse modules includes: a second switch; in each anti-reverse module: the first end of the second switch serves as the current input terminal of the anti-reverse module to which it belongs, and the second end of the second switch serves as the current output terminal of the anti-reverse module to which it belongs; The first end of the second switch is the end of the second switch connected to the anode of its own body diode, and the second end of the second switch is the end of the second switch connected to the cathode of its own body diode.
6. The flyback converter circuit according to any one of claims 1 to 5, characterized in that, Also includes: Soft-switching capacitors; where: One end of the soft-switching capacitor is connected to the input terminal of the second chopper switch, and the other end of the soft-switching capacitor is connected to the output terminal of the second chopper switch.
7. A flyback converter, characterized in that, include: At least two PCBs arranged side by side and a flyback converter circuit as described in any one of claims 1 to 6; wherein: Each layer of the PCB board has through holes, and the magnetic core of the transformer in the flyback converter circuit passes through the through holes 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; The other components in the flyback converter circuit are respectively mounted on the PCB boards of each layer.
8. The flyback converter according to claim 7, characterized in that, The primary winding of the transformer is divided into 2N groups, where N is a positive integer. The 2N groups are symmetrically arranged on the top N layers of the PCB board and the bottom N layers of the PCB board, respectively. The transformer includes at least one secondary winding, and each of the secondary windings is respectively disposed on the PCB board located in the middle.
9. The flyback converter according to claim 8, characterized in that, The first chopper switch in the flyback converter circuit is disposed on any of the top layers of the PCB board; The second chopper switch in the flyback converter circuit is disposed on any of the top layers of the PCB board; The first switching transistor in the flyback converter circuit is disposed on any layer of the PCB board located at the bottom. The input capacitor in the flyback converter circuit is located on any layer of the PCB board at the bottom.
10. The flyback converter according to claim 8, characterized in that, The flyback converter circuit includes at least one output capacitor, and each output capacitor is disposed on any of the top layers of the PCB board. And / or, The flyback converter circuit includes an absorption module; the absorption module includes an absorption resistor, an absorption capacitor, and a first diode; the absorption resistor is disposed on any of the top layers of the PCB board; the absorption capacitor is disposed on any of the bottom layers of the PCB board; the first diode is disposed on any of the bottom layers of the PCB board. And / or, The flyback converter circuit includes at least one anti-flyback module, and each anti-flyback module is disposed on any layer of the PCB board located at the top.
11. The flyback converter according to any one of claims 7 to 10, characterized in that, Apart from the transformer windings, all other components on each layer of the PCB are positioned at a distance from the magnetic core that is less than a preset value.
12. A soft-switching control method, characterized in that, The soft-switching control method is applied to the flyback converter circuit as described in any one of claims 1 to 6, comprising: The first chopper switch in the flyback converter circuit is switched to the on state, the second chopper switch is switched to the on state, and the first switch is in the off state. After a first preset time, the first chopper switch is controlled to switch to the off state; When the junction capacitance of the first chopper switch is fully charged and the junction capacitance of the first switch is fully discharged, the first switch is controlled to switch to the on state and the second chopper switch is controlled to switch to the off state. When the junction capacitance of the second chopper switch is completely discharged, the first switch is controlled to switch to the off state and the second chopper switch is controlled to switch to the on state. After the junction capacitance of the first chopper switch has been discharged and the first switch has been charged, determine whether to allow the flyback converter circuit to continue operating. If the flyback converter circuit continues to operate, the first chopper switch is controlled to switch to the on state, and the process returns to the step of controlling the first chopper switch to switch to the off state after a first preset time.
13. The soft-switching control method according to claim 12, characterized in that, If the voltage across the primary winding of the transformer in the flyback converter circuit is zero, then the junction capacitance of the first chopper switch is fully charged and the junction capacitance of the first switch is fully discharged.
14. The soft-switching control method according to claim 12, characterized in that, If the voltage across the primary winding of the transformer in the flyback converter circuit is zero and the current in the primary winding remains unchanged for a second preset time, then the junction capacitance of the second chopper switch is discharged.
15. The soft-switching control method according to any one of claims 12 to 14, characterized in that, If the voltage across the primary winding of the transformer in the flyback converter circuit is equal to the voltage on the input side of the flyback converter circuit, then the junction capacitance of the first chopper switch is discharged and the first switch is charged.