Flyback power supply circuit and electronic device

Abstract

The application discloses a flyback power supply circuit and electronic equipment, and belongs to the technical field of electronic equipment. The flyback power supply circuit comprises a primary winding, a control circuit, a magnetic field generating circuit, and a second switch piece. The primary winding generates a first magnetic field in a power-on state. The control circuit is connected to a first end of the primary winding, detects whether a resonance signal exists in the primary winding, and causes the magnetic field generating circuit to generate a second magnetic field in the case that the resonance signal is detected. The magnetic field generating circuit is connected to the control circuit and generates the second magnetic field under the control of the control circuit. The first magnetic field and the second magnetic field have opposite magnetic flux directions. The first end of the second switch piece is connected to the first end of the primary winding, the second end of the second switch piece is connected to the ground end of the power supply, and the third end of the second switch piece is connected to the control circuit.

Description

Technical Field

[0001] This application belongs to the field of electronic equipment technology, specifically relating to a flyback power supply circuit and an electronic device. Background Technology

[0002] In related technologies, when the switching components of a flyback power supply are in the off state during operation, the parasitic capacitance in the switching components acts on the primary winding of the transformer, thereby causing resonance in the flyback power supply and generating electromagnetic interference (EMI). This results in the flyback power supply failing to meet electromagnetic compatibility (EMC) standards.

[0003] Specifically, such as Figure 1 The flyback power supply 100' shown, during operation, in one operating cycle, when the switching component 102' is in the off state, due to the parasitic capacitance in the switching component 102' acting on the primary coil 104' of the transformer, current flows through the primary coil 104'. Simultaneously, under the electromagnetic induction phenomenon of the primary coil 104', the current in the primary coil 104' forms an oscillating current, thereby causing resonance in the flyback power supply 100'. Specifically, as... Figure 2 As shown, Figure 1 The waveform of the voltage in the primary coil 104' of the transformer during the operation of the flyback power supply 100' is shown in the figure. The horizontal axis represents time, and the vertical axis represents the voltage at one end of the primary coil 104'. At time T0, the switching component 102' is turned on, and the voltage of the primary coil 104' is at a lower potential. At time T1, the switching component 102' is turned off, and the primary coil 104' begins to release energy. Until the energy release is complete, at time T2, the parasitic capacitance of the switching component 102' begins to act on the primary coil 104', causing resonance in the flyback power supply 100'. Until the next cycle, at time T3, the switching component 102' turns on again, and the voltage of the primary coil 104' is at a lower potential. This resonance in the flyback power supply 100' generates electromagnetic interference, which affects the normal operation of electronic equipment near the flyback power supply 100', causing the flyback power supply 100' to fail to meet electromagnetic compatibility standards. Summary of the Invention

[0004] This application aims to provide a flyback power supply circuit and electronic device that can solve the problem in related technologies where resonance occurs in the flyback power supply, causing the flyback power supply to fail to meet electromagnetic compatibility standards.

[0005] In a first aspect, embodiments of this application propose a flyback power supply circuit, including: a primary winding, which generates a first magnetic field when energized;

[0006] The control circuit is connected to the first end of the primary winding to detect whether there is a resonance signal in the primary winding, and when the resonance signal is detected, to cause the magnetic field generating circuit to generate a second magnetic field.

[0007] A magnetic field generating circuit is connected to a control circuit, and under the control of the control circuit, a second magnetic field is generated.

[0008] The first magnetic field and the second magnetic field have opposite magnetic flux directions;

[0009] The second switch has its first end connected to the first end of the primary winding, its second end connected to the grounding terminal of the power supply, and its third end connected to the control circuit.

[0010] In this embodiment, a magnetic field generating circuit is incorporated into the flyback power supply circuit and connected to the primary winding via a control circuit. This allows the control circuit to detect the presence of a resonant signal in the primary winding. Upon detecting a resonant signal, the control circuit activates the magnetic field generating circuit to generate a second magnetic field. Furthermore, the second magnetic field and the first magnetic field generated when the primary winding resonates have opposite magnetic flux directions, thus canceling each other out. This prevents electromagnetic induction in the primary winding and eliminates the resonant signal. In other words, the resonance in the flyback power supply circuit disappears, ensuring that the flyback power supply meets electromagnetic compatibility standards.

[0011] Secondly, embodiments of this application provide an electronic device including the flyback power supply circuit of the first aspect.

[0012] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0013] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0014] Figure 1 A schematic diagram of the structure of a flyback power supply in the related technology is shown;

[0015] Figure 2 It shows Figure 1 Voltage waveform diagram in the primary coil of the transformer in a flyback power supply;

[0016] Figure 3 One of the structural schematic diagrams of a flyback power supply circuit according to an embodiment of this application is shown;

[0017] Figure 4 A second schematic diagram of the structure of a flyback power supply circuit according to an embodiment of this application is shown;

[0018] Figure 5 It shows Figure 3 Voltage waveform diagram in the primary winding of a flyback power supply circuit.

[0019] Figure label:

[0020] 100′ flyback power supply, 102′ switching components, 104′ primary coil;

[0021] 100 Flyback power supply circuit, 102 Primary winding, 104 Control circuit, 106 Magnetic field generating circuit, 108 Cancellation winding, 110 First switch, 112 Second switch, 114 Voltage regulator circuit, 116 Zener diode, 118 First diode, 120 Secondary winding, 122 Second diode, 124 First energy storage capacitor, 126 Second energy storage capacitor, 128 Input terminal, 130 Ground terminal. Detailed Implementation

[0022] The embodiments of this application will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0023] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0024] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0025] The flyback power supply circuit and electronic device according to embodiments of this application are described below with reference to the accompanying drawings.

[0026] In some embodiments of this application, a flyback power supply circuit is provided, such as Figure 3 As shown, the flyback power supply circuit 100 includes a primary winding 102, a control circuit 104, and a magnetic field generating circuit 106. When energized, the primary winding 102 generates a first magnetic field. The control circuit 104 is connected to the first end of the primary winding 102 and detects whether a resonance signal exists in the primary winding 102. If a resonance signal is detected, the magnetic field generating circuit generates a second magnetic field. The magnetic field generating circuit 106 is connected to the control circuit 104 and generates the second magnetic field under the control of the control circuit 104. The first and second magnetic fields have opposite magnetic flux directions. The flyback power supply circuit 100 also includes a second switch 112. The first end of the second switch 112 is connected to the first end of the primary winding 102, the second end of the second switch 112 is connected to the power supply ground terminal 130, and the third end of the second switch 112 is connected to the control circuit 104.

[0027] In this embodiment, the flyback power supply circuit 100 includes a primary winding 102. When energized, the primary winding 102 generates a first magnetic field, which in turn acts on the secondary winding. This interaction between the primary and secondary windings allows the flyback power supply to regulate the input power voltage, thereby outputting a voltage suitable for electrical equipment. Furthermore, the flyback power supply circuit 100 also includes a control circuit 104 and a magnetic field generating circuit 106. The control circuit 104 is connected to one end of the primary winding 102. During operation, the control circuit 104 can detect the presence of a resonance signal in the primary winding 102. Furthermore, if the control circuit 104 detects a resonance signal, it can control the magnetic field generating circuit 106 to generate a second magnetic field.

[0028] like Figure 3 As shown, compared with flyback power supplies in related technologies, the flyback power supply circuit 100 provided in this application also includes a magnetic field generating circuit 106. The magnetic field generating circuit 106 is connected to the control circuit 104. Simultaneously, during the operation of the flyback power supply circuit 100, the control circuit 104 detects the resonant signal in the primary winding 102. It can be understood that when a resonant signal exists in the primary winding 102, it indicates that current is flowing through the primary winding 102, causing a first magnetic field to be generated around the primary winding 102.

[0029] Furthermore, upon detecting a resonant signal in the primary winding 102, the control circuit 104 can control the operation of the magnetic field generating circuit 106, that is, energize the magnetic field generating circuit 106. After being energized, the magnetic field generating circuit 106 generates a second magnetic field. The second magnetic field and the first magnetic field have opposite magnetic flux directions, thus canceling out the first magnetic field and causing it to disappear. After the first magnetic field disappears, the primary winding 102 no longer generates electromagnetic induction, thereby eliminating the oscillating current in the primary winding 102, and consequently, eliminating the resonance in the flyback power supply circuit 100. After the resonance disappears, the generation of electromagnetic interference in the flyback power supply circuit 100 is effectively reduced, ensuring that the flyback power supply meets electromagnetic compatibility standards and reducing interference from other electronic devices.

[0030] Specifically, see Figure 1 , Figure 2 , Figure 4 and Figure 5 As can be seen, compared with the flyback power supply in related technologies, the flyback power supply circuit 100 provided in this application adds a magnetic field generating circuit 106. By setting the magnetic field generating circuit 106, the resonance can be eliminated at the beginning of the resonance stage, thereby effectively reducing the generation of electromagnetic interference.

[0031] Furthermore, the flyback power supply circuit 100 also includes: a second switch 112, the first end of the second switch 112 being connected to the first end of the primary winding 102, the second end of the second switch 112 being connected to the ground terminal 130 of the power supply, and the third end of the second switch 112 being connected to the control circuit 104.

[0032] like Figure 3 and Figure 4 As shown, by setting the second switch 112, the connection and disconnection between the primary winding 102 and the power input terminal 128 and the power ground terminal 130 can be controlled during the operation of the flyback power supply circuit 100. Specifically, when the two ends of the primary winding 102 are connected to the power input terminal 128 and the power ground terminal 130 respectively, the primary winding 102 begins to charge. When the primary winding 102 is disconnected from the power ground terminal 130, the primary winding 102 begins to release energy to the secondary winding, so as to realize the transformation process of the flyback power supply.

[0033] Specifically, the first end of the second switch 112 is connected to the first end of the primary winding 102, the second end of the second switch 112 is connected to the ground terminal 130 of the power supply, and the third end of the second switch 112 is connected to the control circuit 104. This allows the control circuit 104 to control the second switch 112, that is, to control the connection and disconnection between the first and second ends of the second switch 112, thereby controlling the connection and disconnection between the primary winding 102 and the input terminal 128 and the ground terminal 130 of the power supply.

[0034] Specifically, the second switching element 112 can be an N-type MOSFET. The gate of the MOSFET is connected to the control circuit 104, the drain is connected to the first end of the primary winding 102, and the source is connected to the ground terminal 130 of the power supply. The control circuit 104 can periodically control the switching between the drain and the source according to the specific operating requirements of the flyback power supply circuit 100. It is understood that the MOSFET generates parasitic capacitance during operation. When the drain and source are disconnected, the parasitic capacitance acts on the primary winding 102 connected to the drain, causing capacitance to be generated in the primary winding 102 and resonating under electromagnetic induction. The magnetic field generating circuit 106 effectively eliminates this resonance, ensuring the electromagnetic compatibility of the flyback power supply circuit 100.

[0035] This application incorporates a magnetic field generating circuit 106 in the flyback power supply circuit 100, connected to the primary winding 102 via a control circuit 104. The control circuit 104 detects the presence of a resonant signal in the primary winding 102. Upon detecting a resonant signal, the control circuit 104 activates the magnetic field generating circuit 106, generating a second magnetic field. This second magnetic field has an opposite flux direction to the first magnetic field generated by the primary winding 102, thus canceling out the first magnetic field and eliminating electromagnetic induction in the primary winding 102. This eliminates the resonant signal in the primary winding 102, ensuring the flyback power supply meets electromagnetic compatibility standards.

[0036] In some embodiments of this application, the magnetic field generating circuit 106 includes a canceling winding 108 and a first switching element 110. The first end of the canceling winding 108 and the first end of the primary winding 102 are of the same name. That is, when the directions of the canceling winding 108 and the primary winding 102 are the same, both the first end of the canceling winding 108 and the first end of the primary winding 102 are the starting points; when the directions of the canceling winding 108 and the primary winding 102 are opposite, one of the first ends of the canceling winding 108 and the first end of the primary winding 102 is the starting point, and the other is the ending point. In other words, "of the same name" refers to the ends of two (or more) windings that have the same potential polarity at any given time under the action of the same alternating magnetic flux.

[0037] The first switch 110 is connected between the control circuit 104 and the first end of the canceling winding 108. Under the control of the control circuit 104, the first switch 110 is turned on or off.

[0038] The second end of the cancelling winding 108 and the second end of the primary winding 102 are both connected to the power input terminal 128. When the first switching element 110 is turned on, the cancelling winding 108 generates a second magnetic field.

[0039] It is understandable that the cancelling winding 108 can share a magnetic core with the primary winding 102 or not, as long as it can achieve the cancelling effect.

[0040] In the embodiments of this application, such as Figure 4 As shown, the magnetic field generating circuit 106 in the flyback power supply circuit 100 specifically includes a canceling winding 108 and a first switching element 110. One end of the canceling winding 108 is the same as the first end of the primary winding 102, and the second end of both the canceling winding 108 and the second end of the primary winding 102 are connected to the power input terminal 128.

[0041] The first switching element 110 is connected to the canceling winding 108, so that the conduction and disconnection of the canceling winding 108 can be controlled by controlling the switching element. It can be understood that when the canceling winding 108 is conducting, the canceling winding 108 can generate a second magnetic field.

[0042] Specifically, the first switch 110 is connected between the control circuit 104 and the first end of the cancelling winding 108, so that the control circuit 104 can control the opening and closing of the first switch 110 according to the detected resonant signal. That is, when the control circuit 104 detects the resonant signal, the control circuit 104 controls the first switch 110 to close. At this time, the first end of the cancelling winding 108 and the second end of the primary winding 102 are the same end, and the second end of the cancelling winding 108 and the second end of the primary winding 102 are both connected to the power input terminal 128. Thus, when the first switch 110 is closed, the circuit direction in the cancelling winding 108 is the same as the current direction in the primary winding 102, and the rotation direction of the cancelling winding 108 is opposite to that of the primary winding 102. This means that when the current is the same, the second magnetic field generated by the cancelling winding 108 has the opposite magnetic flux direction to the first magnetic field generated by the primary winding 102.

[0043] Furthermore, such as Figure 4 As shown, the cancelling winding 108 shares a magnetic core with the primary winding 102, thus making the generation space of the second magnetic field the same as that of the first magnetic field. Simultaneously, when the magnetic flux directions of the second and first magnetic fields are opposite, the second magnetic field can cancel out the first magnetic field of the primary winding 102 within the same space, preventing the primary winding 102 from generating electromagnetic induction and eliminating the resonant signal in the primary winding 102. This also eliminates the resonance in the flyback power supply circuit 100, ensuring that the flyback power supply meets electromagnetic compatibility standards.

[0044] Furthermore, such as Figure 5The diagram shows the voltage waveform in the primary winding 102 of the flyback power supply circuit 100, where the horizontal axis represents time and the vertical axis represents the voltage at the first terminal of the primary winding 102. During the operation of the flyback power supply circuit 100, at time t0, the first and second terminals of the second switch 112 are turned on, and the primary winding 102 begins to charge. The first terminal of the primary winding 102 is at a lower potential until time t1, when the first and second terminals of the second switch 112 are disconnected, and the primary winding 102 begins to release energy. Energy release is complete at time t2, at which point the parasitic capacitance of the second switch 112 begins to act on the primary winding 102, generating resonance in the flyback power supply circuit 100. The control circuit 104 detects the first trough of the resonance at time t3, and then controls the first switch 110 to turn on, canceling the second magnetic field generated by the winding 108. Meanwhile, since the cancelling winding 108 and the primary winding 102 share a common magnetic core, when the first switch 110 is turned on, the current flowing into the cancelling winding 108 and the primary winding 102 is the same. This ensures that the magnitude of the second magnetic field generated by the cancelling winding 108 is the same as the magnitude of the first magnetic field, thus ensuring that the second magnetic field cancels out the first magnetic field and eliminates the resonance. The voltage at the first end of the primary winding 102 remains stable. At this time, the control circuit 104 can control the first switch 110 to turn off until time t4, when one operating cycle of the flyback power supply circuit 100 is completed. The control circuit 104 then controls the first end of the second switch 112 to turn on with the second end of the second switch 112, entering the next operating cycle. Compared to the resonant signal in the flyback power supply in related technologies, see [link to relevant documentation]. Figure 2 As shown, the flyback power supply circuit 100 of this application can eliminate resonance at the beginning of the resonance stage, thereby reducing the generation of electromagnetic interference.

[0045] In some embodiments of this application, the number of turns of the offset winding 108 is the same as the number of turns of the primary winding.

[0046] In this embodiment, by setting the number of turns of the canceling winding 108 to be the same as the number of turns of the primary winding 102, when both the canceling winding 108 and the primary winding 102 are connected to the power input terminal 128, current can pass through the canceling winding 108 and the primary winding 102 simultaneously, thereby ensuring that the canceling winding 108 can generate a second magnetic field, and the magnetic induction intensity of the second magnetic field is the same as that of the first magnetic field, so that the second magnetic field can cancel the first magnetic field.

[0047] Furthermore, the primary winding 102 and the canceling winding 108 can be connected to different power sources. When the primary winding 102 and the canceling winding 108 are connected to different power sources, the number of turns of the coil in the canceling winding 108 can be set to be different from the number of turns of the coil in the primary winding 102. This ensures that when the primary winding 102 generates a resonant signal, current can flow through the canceling winding 108 to generate a second magnetic field.

[0048] In some embodiments of this application, generating a second magnetic field in the magnetic field generating circuit 106 upon detecting a resonant signal in the primary winding 102 includes:

[0049] When the control circuit 104 detects that the resonant signal meets the first condition, it turns on the first switch 110 and turns off the first switch 110 when it detects that the resonant signal meets the second condition.

[0050] In this embodiment, during the operation of the flyback power supply circuit 100, the control circuit 104 detects the resonant signal in the primary winding 102 and controls the magnetic field generating circuit 106 to conduct when the resonant signal appears in the primary winding 102, thereby generating a second magnetic field to make the resonant signal disappear. During one cycle of the flyback power supply circuit 100's operation, and to avoid the magnetic field generating circuit 106 affecting the normal operation of the flyback power supply circuit 100 when it is conducting, the control circuit 104 needs to control the first switch 110 to close after detecting the resonant signal and when the resonant signal meets the first condition, so that the magnetic field generating circuit 106 generates the second magnetic field. Simultaneously, to ensure that the conduction of the magnetic field generating circuit 106 does not affect the next operating cycle of the flyback power supply circuit 100, the control circuit 104 needs to control the first switch 110 to open after the resonant signal weakens or disappears and before the next operating cycle of the flyback power supply circuit 100. That is, the control circuit 104 also needs to control the first switch 110 to turn off when the resonant signal meets the second condition.

[0051] By controlling the first switching element 110 according to the first and second conditions of the resonance signal, the control circuit 104 can ensure that when resonance occurs in the flyback power supply circuit 100, the magnetic field generating circuit 106 can be used to make the resonance signal smaller in time, thus ensuring that the flyback power supply circuit 100 meets electromagnetic compatibility. At the same time, it can also effectively avoid the magnetic field generating circuit 106 from interfering with the normal operation of the flyback power supply circuit 100, thus ensuring the normal operation of the flyback power supply circuit 100.

[0052] In some embodiments of this application, the first condition includes: the nth trough of the resonant signal occurs, where n is a natural number;

[0053] Alternatively, the first condition includes: the number of resonances of the resonant signal is greater than a first predetermined number.

[0054] In this embodiment of the application, during the operation of the flyback power supply circuit 100, when the control circuit 104 detects a resonant signal and the nth trough of the resonant signal appears, the control circuit 104 can control the first switching element 110 to be turned on, thereby enabling the magnetic field generating circuit 106 to generate a second magnetic field, so as to cancel the first magnetic field generated by the primary winding 102 through the second magnetic field, thereby eliminating the resonance.

[0055] In other words, the first condition for the control circuit 104 to turn on the first switch 110 is the occurrence of the nth trough of the resonant signal. This effectively prevents the first switch 110 from turning on too early, which would cause the second magnetic field generated by the magnetic field generating circuit 106 to interfere with the first magnetic field generated by the primary winding 102 for the normal operation of the flyback power supply circuit 100, thus ensuring the stable operation of the flyback power supply circuit 100. Specifically, n can be 1, meaning that the control circuit 104 can control the first switch 110 to turn on when it detects the first trough of the resonant signal. This not only prevents the magnetic field generating circuit 106 from interfering with the normal operation of the flyback power supply circuit 100, but also eliminates resonance in time, reducing the generation of electromagnetic interference.

[0056] Alternatively, if the control circuit 104 detects a resonant signal and the number of resonances is greater than a first predetermined number, the control circuit 104 can control the first switch 110 to turn on, so that the magnetic field generating circuit 106 can generate a second magnetic field, which cancels out the first magnetic field generated by the primary winding 102, thereby eliminating the resonance.

[0057] In other words, the first condition for the control circuit 104 to control the first switch 110 to conduct is that the number of resonances is greater than a first predetermined number. Similarly, by controlling the first switch 110 to conduct when the number of resonances is detected to be greater than the first predetermined number, it is possible to effectively prevent the first switch 110 from conducting too early, which would cause the second magnetic field generated by the magnetic field generating circuit 106 to interfere with the first magnetic field generated by the primary winding 102 for the normal operation of the flyback power supply circuit 100, thus ensuring the stable operation of the flyback power supply circuit 100. At the same time, by controlling the first switch 100 to conduct when the number of resonances is greater than the first predetermined number, it is also possible to prevent other signals in the environment from interfering with the judgment of the resonance signal, ensuring the accurate timing of resonance elimination. Specifically, the first predetermined number can be 1, that is, when the number of resonances reaches 1, the first switch 110 can be controlled to conduct, so that the magnetic field generating circuit 106 can generate a second magnetic field, which cancels out the first magnetic field generated by the primary winding 102, thereby achieving resonance elimination.

[0058] In some embodiments of this application, the second condition includes: the absolute value of the amplitude of the resonant signal is less than a predetermined amplitude;

[0059] Alternatively, the second condition includes: the number of resonances of the resonant signal is greater than a second predetermined number.

[0060] In this embodiment, after the first switch 110 is turned on, the magnetic field generating circuit 106 generates a second magnetic field. The second magnetic field cancels out the first magnetic field of the primary winding 102, thereby eliminating electromagnetic induction in the primary winding 102 and thus eliminating resonance. At this time, the control circuit 104 continues to detect the resonance signal in the primary winding 102. When the control circuit 104 detects that the absolute value of the amplitude of the resonance signal is less than a predetermined amplitude, it can control the first switch 110 to be turned off to ensure the normal operation of the flyback power supply circuit 100 in the next cycle.

[0061] In other words, the second condition for the control circuit 104 to control the first switch 110 to turn off is that the absolute value of the amplitude of the resonant signal is less than a predetermined amplitude. It can be understood that as the amplitude of the resonant signal gradually decreases, the energy of the resonance also gradually decreases, and at the same time, the electromagnetic interference generated by the resonance also gradually decreases. When the absolute value of the amplitude of the resonant signal decreases to the predetermined amplitude, it indicates that the electromagnetic interference generated by the resonance is very small, sufficient to ensure that the flyback power supply circuit 100 meets the electromagnetic compatibility standards. At this time, the control circuit 104 can control the first switch 110 to turn off to ensure the normal operation of the flyback power supply circuit 100 in the next operating cycle.

[0062] Alternatively, when the control circuit 104 detects that the resonance number of the resonant signal is greater than the second predetermined number, it can control the first switch 110 to be turned off to ensure the normal operation of the flyback power supply circuit 100 in the next cycle.

[0063] In other words, the second condition for the control circuit 104 to control the first switch 110 to turn off is that the resonance number of the resonant signal is greater than the second predetermined number. As the resonance number of the resonant signal gradually increases, the resonance energy gradually decreases, and thus the resonance amplitude also decreases. The electromagnetic interference generated by the resonance also gradually decreases. When the resonance number of the resonant signal gradually increases to be greater than the second predetermined number, the absolute value of the resonance signal amplitude also decreases to below the predetermined amplitude. At this time, the electromagnetic interference generated by the resonance is very small, which is sufficient to ensure that the flyback power supply circuit 100 can meet the electromagnetic compatibility standard. At this time, the control circuit 104 can control the first switch 110 to turn off to ensure the normal operation of the flyback power supply circuit 100 in the next operating cycle.

[0064] In some embodiments of this application, the flyback power supply circuit 100 further includes a voltage regulator circuit 114, the first end of which is connected to the first end of the primary winding 102, and the second end of which is connected to the second end of the primary winding 102.

[0065] In the embodiments of this application, such as Figure 3 and Figure 4 As shown, by setting the voltage regulator circuit 114, the voltage value in the flyback power supply circuit 100 can be kept below the safe voltage value to prevent damage caused by excessive voltage between the first and second terminals of the second switch 112. In particular, a high voltage will be generated at the moment when the first and second terminals of the second switch 112 are disconnected. By setting the voltage regulator circuit 114, the voltage at the moment when the first and second terminals of the second switch 112 are turned on is kept below the safe voltage, thus ensuring the safety of the flyback power supply circuit 100.

[0066] Specifically, one end of the voltage regulator circuit 114 is connected to the first end of the primary winding 102, and the second end of the voltage regulator circuit 114 is connected to the second end of the primary winding 102.

[0067] Furthermore, the voltage regulator circuit 114 includes: a Zener diode 116, the positive terminal of which is connected to the second end of the primary winding 102;

[0068] The first diode 118 has its cathode connected to the cathode of the Zener diode 116, and its anode connected to the first end of the primary winding 102.

[0069] Specifically, the voltage regulator circuit 114 includes a Zener diode 116 and a first diode 118. The anode of the Zener diode 116 is connected to the second terminal of the primary winding 102, which means the anode of the Zener diode 116 is connected to the power input terminal 128. The cathode of the first diode 118 is connected to the cathode of the Zener diode 116, and the anode of the first diode 118 is connected to the first terminal of the primary winding 102.

[0070] Specifically, when the second switching element 112 is a MOSFET, a Zener diode 116 is used to ensure that the voltage in the flyback power supply circuit 100 is maintained below a safe voltage, thus preventing the MOSFET from being damaged. By using a first diode 118, current can be prevented from flowing from the Zener diode 116 to the MOSFET, which would cause excessive current in the MOSFET and damage it.

[0071] In some embodiments of this application, the flyback power supply circuit 100 further includes a secondary winding 120, which is coupled to the primary winding 102 and is used to connect to a load.

[0072] In the embodiments of this application, such as Figure 3 and Figure 4 As shown, the flyback power supply circuit 100 also includes a secondary winding 120 coupled to the primary winding 102. The coupling between the secondary winding 120 and the primary winding 102 allows for voltage regulation within the flyback power supply circuit 100. Furthermore, by connecting the secondary winding 120 to a load, the regulated electrical energy is delivered to the load, thus providing power. In other words, the flyback power supply circuit 100 includes a transformer, and the primary winding 102 and secondary winding 120 of the flyback power supply circuit are the primary and secondary coils of the transformer, respectively.

[0073] Furthermore, the flyback power supply circuit 100 also includes a second diode 122, the positive terminal of which is connected to the secondary winding 120, and the negative terminal of which is connected to the load.

[0074] Specifically, such as Figure 3 and Figure 4As shown, by using the second diode 122, and taking advantage of the unidirectional conduction property of the diode, the secondary winding 120 is disconnected from the load during the charging process of the primary winding 102. This ensures that the load connected to the secondary winding 120 does not consume electrical energy during the charging process of the primary winding 102, thus guaranteeing stable charging of the primary winding 102. This also ensures the stable operation of the flyback power supply circuit 100. Specifically, during the charging process of the primary winding 102, since the negative terminal of the second diode 122 is connected to the high-voltage end of the secondary winding 120, and the positive terminal of the second diode 122 is connected to the low-voltage end of the secondary winding 120, the current is cut off in the direction from the high-voltage end to the low-voltage end of the secondary winding 120. This means the load is not connected to the secondary winding 120, and therefore does not affect the charging process of the primary winding 102.

[0075] In some embodiments of this application, such as Figure 3 and Figure 4 As shown, the flyback power supply circuit 100 further includes: a first energy storage capacitor 124, the two ends of which are respectively connected to the power supply input terminal 128 and the power supply ground terminal 130.

[0076] The second energy storage capacitor 126 is connected to the two ends of the secondary winding 120.

[0077] In this embodiment, by connecting the two ends of the first energy storage capacitor 124 to the input terminal 128 and the ground terminal 130 of the power supply, respectively, the power supply stores energy on the power-side while supplying power to the flyback power circuit 100. The two ends of the first energy storage capacitor 124 are also connected to the second terminal of the first winding and the second terminal of the second switch 112, respectively. Therefore, even when the power supply is unstable, the first energy storage capacitor 124 can still supply power to the flyback power circuit 100, ensuring that the flyback power circuit 100 can stably obtain power, thus guaranteeing the stable and continuous operation of the flyback power circuit 100.

[0078] Furthermore, by connecting the two ends of the second energy storage capacitor 126 to the two ends of the secondary winding 120, the electrical energy output by the secondary winding 120 can be stored to ensure continuous power supply to the load. Specifically, during the charging process of the primary winding 102, due to the function of the second diode 122 connected to the secondary winding 120, the secondary winding 120 is disconnected from the load. At this time, the energy stored in the second energy storage capacitor 126 is used to supply power to the load, ensuring the continuous and stable operation of the load.

[0079] In some embodiments of this application, the control circuit 104 is also connected to the power input terminal 128 and the power ground terminal 130.

[0080] In the embodiments of this application, such as Figure 3 and Figure 4 As shown, the control circuit 104 specifically includes a flyback controller. The input terminal 128 of the flyback controller is connected to the power supply input terminal 128, and the ground terminal 130 of the flyback controller is connected to the power supply ground terminal 130. Simultaneously, the switch output (SW, Switch) pin of the flyback controller is connected to the first terminal of the primary winding 102 and the first switch 110, enabling the flyback controller to detect the resonant signal of the primary winding 102 and control the first switch 110 to be turned on or off. The gate control input signal (Gate) pin of the flyback controller is connected to the third terminal of the second switch 112 to control the connection / disconnection between the first terminal and the second terminal of the second switch 112.

[0081] This application also provides an electronic device, including a flyback power supply circuit 100 as described in any of the above embodiments.

[0082] The electronic device proposed in this embodiment has the beneficial effects of any of the above embodiments because it has the flyback power supply circuit 100 as described in any of the above embodiments, which will not be elaborated here.

[0083] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0084] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A flyback power supply circuit, characterized in that, include: The primary winding generates a first magnetic field when energized. A control circuit, connected to the first end of the primary winding, detects whether there is a resonance signal in the primary winding, and, if the resonance signal is detected, causes the magnetic field generating circuit to generate a second magnetic field. The magnetic field generating circuit is connected to the control circuit, and generates the second magnetic field under the control of the control circuit; The first magnetic field and the second magnetic field have opposite magnetic flux directions; The second switch has a first end connected to the first end of the primary winding, a second end connected to the grounding terminal of the power supply, and a third end connected to the control circuit. The magnetic field generating circuit includes: A canceling winding, wherein the first end of the canceling winding is the same name as the first end of the primary winding; A first switching element is connected between the control circuit and a first end of the canceling winding. Under the control of the control circuit, the first switching element is turned on or off. The second end of the cancelling winding and the second end of the primary winding are both connected to the input terminal of the power supply. When the first switch is turned on, the cancelling winding generates the second magnetic field.

2. The flyback power supply circuit according to claim 1, characterized in that, The number of turns in the offset winding is the same as the number of turns in the primary winding.

3. The flyback power supply circuit according to claim 1, characterized in that, The step of generating a second magnetic field in the magnetic field generating circuit upon detecting the resonant signal of the primary winding includes: The control circuit turns on the first switch when it detects that the resonant signal meets a first condition, and turns off the first switch when it detects that the resonant signal meets a second condition.

4. The flyback power supply circuit according to claim 3, characterized in that, The first condition includes: The nth trough of the resonant signal appears, where n is a natural number; or The resonance number of the resonant signal is greater than a first predetermined number.

5. The flyback power supply circuit according to claim 3, characterized in that, The second condition includes: The absolute value of the amplitude of the resonant signal is less than a predetermined amplitude; or The resonance number of the resonant signal is greater than the second predetermined number.

6. The flyback power supply circuit according to any one of claims 1 to 5, characterized in that, Also includes: A voltage regulator circuit, wherein a first terminal of the voltage regulator circuit is connected to a first terminal of the primary winding, and a second terminal of the voltage regulator circuit is connected to a second terminal of the primary winding.

7. The flyback power supply circuit according to any one of claims 1 to 5, characterized in that, Also includes: The secondary winding is coupled to the primary winding and is used to connect to a load. A second diode, the positive terminal of which is connected to the secondary winding, and the negative terminal of which is connected to the load.

8. The flyback power supply circuit according to claim 7, characterized in that, Also includes: The first energy storage capacitor has its two ends connected to the input terminal of the power supply and the ground terminal of the power supply, respectively. The second energy storage capacitor has its two ends connected to the two ends of the secondary winding, respectively.

9. The flyback power supply circuit according to any one of claims 1 to 5, characterized in that, The control circuit is also connected to the input terminal of the power supply and the ground terminal of the power supply.

10. An electronic device, characterized in that, include: The flyback power supply circuit as described in any one of claims 1 to 9.

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