Double-transistor flyback power supply circuit

Abstract

The embodiment of the utility model provides a double-transistor flyback power supply circuit. A driving transformer of the double-transistor flyback power supply circuit comprises a first primary side coil, a first secondary side coil and a second secondary side coil. The flyback transformer comprises a second primary side coil. The second electrode of the first switch tube is electrically coupled with the first end of the second primary side coil and the second end of the first secondary side coil, and the control electrode of the first switch tube is electrically coupled to the first end of the first secondary side coil. The first electrode of the second switch tube is electrically coupled with the second end of the second primary side coil, the second electrode of the second switch tube is electrically coupled with the second end of the second secondary side coil, and the control electrode of the second switch tube is electrically coupled to the first end of the second secondary side coil. The driving circuit is electrically coupled with the first primary side coil to transmit a pulse width modulation signal to the first primary side coil. The driving circuit is suitable for being electrically coupled with a direct current power supply end.

Description

Technical Field

[0001] The embodiments disclosed herein relate generally to the field of electrical equipment, and more particularly to a two-tube flyback power supply circuit. Background Technology

[0002] The dual-transistor flyback power supply circuit, as a power supply unit with stable voltage and current, is suitable for applications requiring medium to high voltage AC / DC input and multiple outputs. The dual-transistor flyback power supply circuit operates based on the magnetic flux coupling and flyback effect of a transformer. When both switching transistors are turned on, the input power is stored in the magnetic core through the primary coil of the transformer. When the switching transistors are turned off, the energy stored in the magnetic field is released to the load through the secondary coil. The dual-transistor flyback power supply circuit achieves electrical isolation, reduces electromagnetic interference, and improves efficiency. Utility Model Content

[0003] Embodiments of this disclosure provide a dual-transistor flyback power supply circuit. The dual-tube flyback power supply circuit includes: a drive transformer, including a first primary coil, a first secondary coil, and a second secondary coil; a flyback transformer, including a second primary coil and a third secondary coil; a first switch, the first electrode of which is adapted to be electrically coupled to the bus, the second electrode of which is electrically coupled to the first end of the second primary coil and the second end of the first secondary coil, and the control electrode of which is electrically coupled to the first end of the first secondary coil; a second switch, the first electrode of which is electrically coupled to the second end of the second primary coil, the second electrode of which is electrically coupled to the second end of the second secondary coil and the bus ground, and the control electrode of which is electrically coupled to the first end of the second secondary coil; and a drive circuit, electrically coupled to both ends of the first primary coil to transmit a pulse width modulation signal to the first primary coil, the drive circuit being adapted to be electrically coupled to the DC power supply terminal, wherein when the pulse width modulation signal is a high-level signal, the first primary coil is energized, and when the pulse width modulation signal is a low-level signal, the excess current generated by the magnetic field energy stored in the first primary coil flows to the DC power supply terminal.

[0004] In some embodiments, the driving circuit includes: a third switch transistor, the first electrode of which is electrically coupled to the second terminal of the first primary coil, and the second electrode of which is electrically coupled to the bus ground; a first diode, the anode of which is electrically coupled to the second terminal of the first primary coil, and the cathode of which is adapted to be electrically coupled to the DC power supply terminal; a pulse width modulator, electrically coupled to the control electrode of the third switch transistor and the first terminal of the first primary coil; and a first resistor, electrically coupled between the control electrode of the third switch transistor and the bus ground.

[0005] In some embodiments, the driving circuit further includes a bidirectional Zener diode, one end of which is electrically coupled to the cathode of the first diode, and the other end of which is adapted to be electrically coupled to a DC power supply terminal.

[0006] In some embodiments, the dual-transistor flyback power supply circuit further includes: a first adjustment circuit electrically coupled to both ends of the first secondary coil and electrically coupled to the control electrode of the first switching transistor, the first adjustment circuit being adapted to turn on the first switching transistor when the first secondary coil generates a high-level signal and to turn off the first switching transistor when the first secondary coil generates a low-level signal; and a second adjustment circuit electrically coupled to both ends of the second secondary coil and electrically coupled to the control electrode of the second switching transistor, the second adjustment circuit being adapted to turn on the second switching transistor when the second secondary coil generates a high-level signal and to turn off the second switching transistor when the second secondary coil generates a low-level signal.

[0007] In some embodiments, the first regulating circuit includes: a second diode, the cathode of which is electrically coupled to the control electrode of the first switching transistor, and the anode of which is electrically coupled to a first terminal of the first secondary coil; and a first P-type transistor, the first electrode of which is electrically coupled to the cathode of the second diode, the control electrode of which is electrically coupled to the anode of the second diode, and the second electrode of which is electrically coupled to a second terminal of the first secondary coil; the second regulating circuit includes: a third diode, the cathode of which is electrically coupled to the control electrode of the second switching transistor, and the anode of which is electrically coupled to a first terminal of the second secondary coil; and a second P-type transistor, the first electrode of which is electrically coupled to the cathode of the third diode, the control electrode of which is electrically coupled to the anode of the third diode, and the second electrode of which is electrically coupled to a second terminal of the second secondary coil.

[0008] In some embodiments, the first regulating circuit further includes: a second resistor electrically coupled between the control electrode of the first switching transistor and the first electrode of the first P-type transistor; the second regulating circuit further includes: a third resistor electrically coupled between the control electrode of the second switching transistor and the first electrode of the second P-type transistor.

[0009] In some embodiments, the first adjustment circuit further includes: a fourth resistor electrically coupled between the control electrode of the first switch and the second electrode of the first P-type transistor, wherein the resistance value of the fourth resistor is greater than the on-resistance of the first P-type transistor; the second adjustment circuit further includes: a fifth resistor electrically coupled between the control electrode of the second switch and the second electrode of the second P-type transistor, wherein the resistance value of the fifth resistor is greater than the on-resistance of the second P-type transistor.

[0010] In some embodiments, the dual-tube flyback power supply circuit further includes: a feedback circuit electrically coupled to the third secondary coil and the pulse width modulator, the feedback circuit being adapted to detect the voltage value output by the third secondary coil and provide it to the pulse width modulator, the pulse width modulator being adapted to control the duty cycle of the pulse width modulation signal based on the voltage value.

[0011] In some embodiments, the dual-transistor flyback power supply circuit further includes: an auxiliary power supply coil, magnetically coupled to the second primary coil and electrically coupled to a pulse width modulator, the auxiliary power supply coil being adapted to detect the frequency and trough of the voltage waveform of the second primary coil and provide it to the pulse width modulator, the pulse width modulator being adapted to simultaneously turn on the first and second switching transistors when the voltage waveform of the second primary coil is at a trough.

[0012] In some embodiments, the dual-tube flyback power supply circuit further includes: a capacitor electrically coupled to both ends of the auxiliary power supply coil; and a fourth diode electrically coupled between the auxiliary power supply coil and the capacitor, with the cathode of the fourth diode electrically coupled to the DC power supply terminal.

[0013] In embodiments of this disclosure, the dual-transistor flyback power supply circuit includes a drive transformer, a flyback transformer, a first switching transistor, a second switching transistor, and a drive circuit. The drive transformer includes a first primary winding, a first secondary winding, and a second secondary winding. The flyback transformer includes a second primary winding and a third secondary winding. The first electrode of the first switching transistor is adapted to be electrically coupled to the bus, the second electrode of the first switching transistor is electrically coupled to a first end of the second primary winding and a second end of the first secondary winding, and the control electrode of the first switching transistor is electrically coupled to a first end of the first secondary winding. The first electrode of the second switching transistor is electrically coupled to a second end of the second primary winding, the second electrode of the second switching transistor is electrically coupled to a second end of the second secondary winding and the bus ground, and the control electrode of the second switching transistor is electrically coupled to a first end of the second secondary winding. The drive circuit is electrically coupled to both ends of the first primary winding to transmit a pulse width modulation (PWM) signal to the first primary winding, and the drive circuit is adapted to be electrically coupled to a DC power supply terminal. When the PWM signal is a high-level signal, the first primary winding is energized. When the pulse width modulation signal is low, the excess current generated by the magnetic field energy stored in the first primary coil flows to the DC power supply terminal. Using this arrangement, the leakage inductance energy of the drive transformer can be recovered to the input along the DC power supply terminal without buffer loss or heat generation issues. Furthermore, it solves the volt-second balance problem of the drive transformer's magnetic circuit, preventing rapid saturation. In addition, by using the drive transformer to control the first switching transistor and its on / off states, the drive transformer can isolate the high-voltage bus, thus solving the problem of driving the high-side switching transistor.

[0014] It should be understood that the content described in this section is not intended to limit the key or essential features of the embodiments of this disclosure, nor is it intended to restrict the scope of this disclosure. Other features of this disclosure will become readily apparent from the following description. Attached Figure Description

[0015] The above and other features, advantages, and aspects of the embodiments of this disclosure will become more apparent from the accompanying drawings and the following detailed description. In the drawings, the same or similar reference numerals denote the same or similar elements, wherein:

[0016] Figure 1 A schematic diagram of a dual-transistor flyback power supply circuit according to an embodiment of the present disclosure is shown; and

[0017] Figure 2 The main topology circuit diagram of a dual-transistor flyback power supply circuit according to an embodiment of the present disclosure is shown.

[0018] Explanation of reference numerals in the attached figures:

[0019] 10. Drive transformer; 11. First primary winding; 12. First secondary winding; 13. Second secondary winding;

[0020] 20. Flyback transformer; 21. Second primary winding; 22. Third secondary winding;

[0021] 31. First switching transistor; 32. Second switching transistor;

[0022] 40. Drive circuit; 41. Third switching transistor; 42. First diode; 43. Pulse width modulator; 44. First resistor; 45. Bidirectional Zener diode;

[0023] 50. First regulating circuit; 51. Second diode; 52. First P-type transistor; 53. Second resistor; 54. Fourth resistor;

[0024] 60. Second regulating circuit; 61. Third diode; 62. Second P-type transistor; 63. Third resistor; 64. Fifth resistor;

[0025] 70. Feedback circuit; 71. Adjustable precision parallel voltage regulator; 72. Optocoupler;

[0026] 81. Auxiliary power supply coil; 82. Capacitor; 83. Fourth diode;

[0027] 90. Output circuit; 91. Fifth diode; 92. First capacitor; 93. Load;

[0028] 100. Busbar; 101. AC power supply; 102. DC power supply; 103. Second capacitor; 104. Third capacitor;

[0029] 200. Power supply circuit. Detailed Implementation

[0030] Preferred embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0031] The term "comprising" and its variations as used herein signify open inclusion, i.e., "including but not limited to". Unless otherwise stated, the term "or" means "and / or". The term "based on" means "at least partially based on". The terms "one example embodiment" and "one embodiment" mean "at least one example embodiment". The term "another embodiment" means "at least one additional embodiment". The terms "first", "second", etc., may refer to different or the same objects.

[0032] In some conventional two-transistor flyback power supply circuits, the driving circuit has low efficiency, which may lead to energy waste.

[0033] This disclosure provides a dual-transistor flyback power supply circuit. The dual-transistor flyback power supply circuit includes a drive transformer, a flyback transformer, a first switching transistor, a second switching transistor, and a drive circuit. The drive transformer includes a first primary winding, a first secondary winding, and a second secondary winding. The flyback transformer includes a second primary winding and a third secondary winding. The first electrode of the first switching transistor is adapted to be electrically coupled to a bus, the second electrode of the first switching transistor is electrically coupled to a first terminal of the second primary winding and a second terminal of the first secondary winding, and the control electrode of the first switching transistor is electrically coupled to a first terminal of the first secondary winding. The first electrode of the second switching transistor is electrically coupled to a second terminal of the second primary winding, the second electrode of the second switching transistor is electrically coupled to a second terminal of the second secondary winding and bus ground, and the control electrode of the second switching transistor is electrically coupled to a first terminal of the second secondary winding. The drive circuit is electrically coupled to both ends of the first primary winding to transmit a pulse width modulation (PWM) signal to the first primary winding, and the drive circuit is adapted to be electrically coupled to a DC power supply terminal. When the PWM signal is a high-level signal, the first primary winding is energized. When the pulse width modulation signal is low, the excess current generated by the magnetic field energy stored in the first primary coil flows to the DC power supply terminal. Using this arrangement, the leakage inductance energy of the drive transformer can be recovered to the input along the DC power supply terminal, without buffer losses or heat generation issues. Furthermore, it solves the volt-second balance problem of the drive transformer's magnetic circuit, preventing rapid saturation. In addition, by using the drive transformer to control the first switching transistor's on and off states, the drive transformer can isolate the high-voltage bus, thus solving the problem of driving the high-side switching transistor. The following will combine... Figure 1 and Figure 2 The principles of this disclosure will be described in detail below.

[0034] like Figure 1 and Figure 2 As shown, the dual-transistor flyback power supply circuit includes a drive transformer 10, a flyback transformer 20, a first switching transistor 31, a second switching transistor 32, and a drive circuit 40.

[0035] The drive transformer 10 includes a first primary coil 11, a first secondary coil 12, and a second secondary coil 13. The first secondary coil 12 and the second secondary coil 13 are magnetically coupled to the first primary coil 11 via a magnetic core. When a change in the current in the first primary coil 11 causes a change in its magnetic field, an electromotive force (EMF) is induced in the magnetically coupled first secondary coil 12 and second secondary coil 13. In some embodiments, the first secondary coil 12 and the second secondary coil 13 have the same specifications, such as the number of turns, wire diameter, and material properties. Under the same magnetic field change conditions, the first secondary coil 12 and the second secondary coil 13 can generate induced EMFs of equal magnitude and phase, ensuring that the EMF outputs between them are synchronized and balanced.

[0036] The flyback transformer 20 includes a second primary coil 21 and a third secondary coil 22, which are magnetically coupled through a magnetic core. When a change in the current in the second primary coil 21 causes a change in its magnetic field, an electromotive force is induced in the magnetically coupled third secondary coil 22. In some embodiments, the third secondary coil 22 can be electrically coupled to an output circuit 90. The output circuit 90 may include electrical components such as a first capacitor 92 and a fifth diode 91, which can rectify and filter the current output from the third secondary coil 22 to ensure the stability of the output current.

[0037] Each of the first switching transistor 31 and the second switching transistor 32 includes a first electrode, a second electrode, and a control electrode. In some embodiments, the first switching transistor 31 and the second switching transistor 32 may be metal-oxide-semiconductor field-effect transistors, with the first electrode of each switching transistor being the source, the second electrode being the drain, and the control electrode being the gate. In other embodiments, the first switching transistor 31 and the second switching transistor 32 may be insulated-gate bipolar transistors, with the first electrode of each switching transistor being the collector, the second electrode being the emitter, and the control electrode being the gate.

[0038] like Figure 1 and Figure 2 As shown, the first electrode of the first switch transistor 31 is electrically coupled to the bus 100, the second electrode of the first switch transistor 31 is electrically coupled to the first end of the second primary coil 21 and the second end of the first secondary coil 12, and the control electrode of the first switch transistor 31 is electrically coupled to the first end of the first secondary coil 12. The first electrode of the second switch transistor 32 is electrically coupled to the second end of the second primary coil 21, the second electrode of the second switch transistor 32 is electrically coupled to the second end of the second secondary coil 13 and the bus ground, and the control electrode of the second switch transistor 32 is electrically coupled to the first end of the second secondary coil 13.

[0039] In some embodiments, such as Figure 2 As shown, a power supply circuit 200 can be used to supply power to the bus 100. The power supply circuit 200 may include an AC power supply 101, which is rectified to form a DC power supply 102. The bus 100 is electrically coupled to the DC power supply 102, thereby providing a bus voltage to the first electrode of the first switching transistor 31.

[0040] In some embodiments, the power supply circuit 200 further includes a second capacitor 103 and a third capacitor 104 connected in series across the DC power supply 102. In this way, the bus voltage can be made more stable.

[0041] It should be understood that in other embodiments, the power supply circuit 200 may directly include a DC power supply 102 without the need for an AC power supply 101 and a rectifier circuit, as long as it can supply power to the bus 100. This disclosure is not intended to limit this.

[0042] like Figure 1 and Figure 2 As shown, the driving circuit 40 is electrically coupled to both ends of the first primary coil 11. The driving circuit 40 can transmit pulse width modulation signals to the first primary coil 11, and the driving circuit 40 is electrically coupled to the DC power supply terminal VCC.

[0043] When the pulse width modulation signal applied by the drive circuit 40 to the first primary coil 11 is a high-level signal, current flows through the first primary coil 11 and establishes a magnetic field in the core, i.e., the excitation process. Due to magnetic coupling, the changing magnetic field induces corresponding electromotive forces in the first secondary coil 12 and the second secondary coil 13. When a high-level signal is output from the first terminal of the first secondary coil 12 and the first terminal of the second secondary coil 13, the first switch 31 and the second switch 32 are turned on according to their control electrode voltages, thereby controlling the flow of energy in the circuit.

[0044] When the pulse width modulation signal applied by the drive circuit 40 to the first primary coil 11 is a low-level signal, the current in the first primary coil 11 is interrupted, but the magnetic field energy previously stored in the magnetic core needs to be released. This magnetic field energy is converted into current and returned to the DC power supply terminal for recycling. During this process, the induced electromotive force generated by the first secondary coil 12 and the second secondary coil 13 causes the first switch 31 and the second switch 32 to switch states, thereby allowing energy to be transferred from the second primary coil 21 of the flyback transformer 20 to the third secondary coil 22, and then supplied to the load 93 electrically coupled to the output circuit 90.

[0045] Using this arrangement, the drive circuit 40 can return the leakage inductance energy of the drive transformer 10 to the input terminal, reducing losses and heat generation, and maintaining the volt-second balance of the drive transformer 10 to prevent rapid saturation. Simultaneously, by using the drive transformer 10 to isolate the high-voltage bus, the problem of driving the high-side switch is solved, making the entire dual-transistor flyback power supply circuit more stable.

[0046] In some embodiments, such as Figure 1 and Figure 2 As shown, the driving circuit 40 includes a third switching transistor 41, a first diode 42, a pulse width modulator 43, and a first resistor 44.

[0047] like Figure 1 and Figure 2As shown, the first end of the first primary coil 11 is electrically coupled to the pulse width modulator 43, and the second end of the first primary coil 11 is electrically coupled to the first electrode of the third switch 41 and the anode of the first diode 42. The second electrode of the third switch 41 is electrically coupled to the bus ground, and the control electrode of the third switch 41 is electrically coupled to the pulse width modulator 43. The cathode of the first diode 42 is adapted to be connected to the DC power supply terminal for energy recovery. The first resistor 44 is electrically coupled between the control electrode of the third switch 41 and the bus ground, serving a current limiting and protection function.

[0048] In some embodiments, the third switch 41 may be a metal-oxide-semiconductor field-effect transistor, with the first electrode of the third switch 41 being the source, the second electrode being the drain, and the control electrode being the gate. In other embodiments, the third switch 41 may also be an insulated-gate bipolar transistor, with the first electrode of the third switch 41 being the collector, the second electrode being the emitter, and the control electrode being the gate.

[0049] When the pulse width modulation signal output by the pulse width modulator 43 is a high-level signal, the high-level signal is not only applied to the first end of the first primary coil 11, but is also transmitted to the control electrode of the third switch 41, causing the third switch 41 to conduct. As the third switch 41 conducts, current flows from the first primary coil 11 and the third switch 41 to the bus ground, thereby establishing a magnetic field in the first primary coil 11 and realizing the excitation process.

[0050] When the pulse width modulation signal output by the pulse width modulator 43 is a low-level signal, the third switch 41 is turned off, cutting off the current path in the first primary coil 11. Since the magnetic field energy previously stored in the first primary coil 11 needs to be released, the voltage across the first primary coil 11 is reversed, causing the first diode 42 to be forward biased and turned on.

[0051] In this way, the leakage inductance energy of the drive transformer 10 can be recovered to the input terminal, while the pulse width modulator 43 controls the on and off times of the third switch 41 to achieve efficient energy management and conversion. Furthermore, the first resistor 44 can effectively protect and stabilize the third switch 41.

[0052] In some embodiments, such as Figure 1 and Figure 2 As shown, the driving circuit 40 also includes a bidirectional Zener diode 45. One end of the bidirectional Zener diode 45 is electrically coupled to the cathode of the first diode 42, and the other end of the bidirectional Zener diode 45 is adapted to be electrically coupled to the DC power supply terminal.

[0053] When the pulse width modulated signal output by the pulse width modulator 43 is a low-level signal, the third switch 41 is turned off, cutting off the current path in the first primary coil 11. Excess energy stored in the first primary coil 11 is converted into current, flowing through the first diode 42 and the bidirectional Zener diode 45 to the DC power supply terminal, completing the energy recovery process. The bidirectional Zener diode provides overvoltage protection by rapidly switching to a low-resistance state when the voltage across it exceeds a specific threshold, and helps stabilize the voltage in the process.

[0054] In some embodiments, such as Figure 1 and Figure 2 As shown, the dual-transistor flyback power supply circuit also includes a first adjustment circuit 50 and a second adjustment circuit 60. The first adjustment circuit 50 is electrically coupled to both ends of the first secondary coil 12 and to the control electrode of the first switching transistor 31. The first adjustment circuit 50 can control the first switching transistor 31 to turn on or off based on the voltage signal on the first secondary coil 12. The second adjustment circuit 60 is electrically coupled to both ends of the second secondary coil 13 and to the control electrode of the second switching transistor 32. The second adjustment circuit 60 can control the second switching transistor 32 to turn on or off based on the voltage signal on the second secondary coil 13.

[0055] The first regulating circuit 50 can monitor the voltage across the first secondary coil 12. If a high-level signal is detected from the first secondary coil 12, the first switching transistor 31 is turned on; if a low-level signal is detected from the first secondary coil 12, the first switching transistor 31 is turned off.

[0056] The second regulating circuit 60 monitors the voltage across the second secondary coil 13. If a high-level signal is detected from the second secondary coil 13, the second switching transistor 32 is turned on; if a low-level signal is detected from the second secondary coil 13, the second switching transistor 32 is turned off.

[0057] In this way, the first regulating circuit 50 and the second regulating circuit 60 can control the turn-on and turn-off times of the first switching transistor 31 and the second switching transistor 32, ensuring that they are as consistent as possible and reducing losses and electromagnetic interference caused by inconsistency. Furthermore, the first regulating circuit 50 and the second regulating circuit 60 can optimize the driving waveform of the pulse width modulation signal, enabling the first switching transistor 31 and the second switching transistor 32 to turn off quickly, thereby increasing the switching frequency of the dual-transistor flyback power supply circuit.

[0058] In some embodiments, such as Figure 1As shown, the first regulating circuit 50 includes a second diode 51 and a first P-type transistor 52. The cathode of the second diode 51 is electrically coupled to the control electrode of the first switching transistor 31, and the anode of the second diode 51 is electrically coupled to the first terminal of the first secondary coil 12. The first electrode of the first P-type transistor 52 is electrically coupled to the cathode of the second diode 51, the control electrode of the first P-type transistor 52 is electrically coupled to the anode of the second diode 51, and the second electrode of the first P-type transistor 52 is electrically coupled to the second terminal of the first secondary coil 12. In some embodiments, the second electrode of the first P-type transistor 52 may be electrically coupled to the bus ground. With this arrangement, when a low-level signal is output from the first terminal of the first secondary coil 12, the first P-type transistor 52 is turned on, which can quickly discharge the parasitic capacitance (e.g., gate-source capacitance) at the control electrode of the first switching transistor 31, thereby accelerating the change of the control electrode voltage and helping to improve the turn-off efficiency of the first switching transistor 31.

[0059] In some embodiments, such as Figure 1 As shown, the second regulating circuit 60 includes a third diode 61 and a second P-type transistor 62. The cathode of the third diode 61 is electrically coupled to the control electrode of the second switching transistor 32, and the anode of the third diode 61 is electrically coupled to the first terminal of the second secondary coil 13. The first electrode of the second P-type transistor 62 is electrically coupled to the cathode of the third diode 61, the control electrode of the second P-type transistor 62 is electrically coupled to the anode of the third diode 61, and the second electrode of the second P-type transistor 62 is electrically coupled to the second terminal of the second secondary coil 13. In some embodiments, the second electrode of the second P-type transistor 62 can be electrically coupled to the bus ground. With this arrangement, when a low-level signal is output at the first terminal of the second secondary coil 13, the second P-type transistor 62 turns on, which can quickly discharge the parasitic capacitance at the control electrode of the second switching transistor 32, thereby accelerating the voltage change of the control electrode and helping to improve the turn-off efficiency of the second switching transistor 32.

[0060] In some embodiments, such as Figure 1 As shown, the first regulating circuit 50 also includes a second resistor 53. The second resistor 53 is electrically coupled between the control electrode of the first switching transistor 31 and the first electrode of the first P-type transistor 52. With this arrangement, when a low-level signal is output from the first terminal of the first secondary coil 12, the first P-type transistor 52 is turned on. The electrical energy released when the parasitic capacitance at the control electrode of the first switching transistor 31 discharges is consumed as heat by the second resistor 53 and the first P-type transistor 52, which can accelerate the discharge of the parasitic capacitance and help improve the turn-off efficiency of the first switching transistor 31.

[0061] In some embodiments, such as Figure 1As shown, the second regulating circuit 60 also includes a third resistor 63. The third resistor 63 is electrically coupled between the control electrode of the second switch 32 and the first electrode of the second P-type transistor 62. With this arrangement, when a low-level signal is output from the first terminal of the second secondary coil 13, the second P-type transistor 62 is turned on. The electrical energy released when the parasitic capacitance at the control electrode of the second switch 32 discharges is consumed as heat by the third resistor 63 and the second P-type transistor 62, which can accelerate the discharge of the parasitic capacitance and help improve the turn-off efficiency of the second switch 32.

[0062] In some embodiments, such as Figure 1 As shown, the first regulating circuit 50 also includes a fourth resistor 54. The fourth resistor 54 is electrically coupled between the control electrode of the first switching transistor 31 and the second electrode of the first P-type transistor 52, and the resistance of the fourth resistor 54 is greater than the on-resistance of the first P-type transistor 52. With this arrangement, when a low-level signal is output from the first terminal of the first secondary coil 12, most of the electrical energy released when the parasitic capacitance at the control electrode of the first switching transistor 31 discharges is consumed as heat by the second resistor 53 and the first P-type transistor 52, and the remainder can be consumed by the fourth resistor 54.

[0063] In some embodiments, such as Figure 1 As shown, the second adjustment circuit 60 also includes a fifth resistor 64. The fifth resistor 64 is electrically coupled between the control electrode of the second switch 32 and the second electrode of the second P-type transistor 62, and the resistance of the fifth resistor 64 is greater than the on-resistance of the second P-type transistor 62. When a low-level signal is output from the first terminal of the second secondary coil 13, most of the electrical energy released during the discharge of the parasitic capacitance at the control electrode of the second switch 32 is consumed as heat by the third resistor 63 and the second P-type transistor 62; the remainder can be consumed by the fifth resistor 64.

[0064] In some embodiments, such as Figure 2 As shown, the dual-transistor flyback power supply circuit also includes a feedback circuit 70. The feedback circuit 70 is electrically coupled to the third secondary coil 22 and the pulse width modulator 43. The feedback circuit 70 can detect the voltage value output by the third secondary coil 22 and provide it to the pulse width modulator 43, which can control the duty cycle of the pulse width modulation signal based on the voltage value.

[0065] The pulse width modulator 43 can dynamically adjust the duty cycle of its generated pulse width modulation signal based on the voltage value provided by the feedback circuit 70. If the voltage output by the third secondary coil 22 is higher than the set target value, the pulse width modulator 43 will reduce the duty cycle of the pulse width modulation signal. If the voltage is lower than the target value, the duty cycle will be increased. In this way, the output voltage can be stabilized within a preset range, remaining stable even if the input voltage or load conditions change.

[0066] In some embodiments, such as Figure 2 As shown, the feedback circuit 70 includes an adjustable precision parallel regulator 71 and an optocoupler 72. The adjustable precision parallel regulator 71 can be, for example, a TL431. The reference terminal of the adjustable precision parallel regulator 71 is electrically coupled to the output circuit of the third secondary coil 22 via a voltage divider network to detect whether the output voltage reaches a preset value. A light-emitting diode of the optocoupler 72 is connected in series between the cathode and anode of the adjustable precision parallel regulator 71 and grounded via a resistor bus. The phototransistor portion of the optocoupler 72 is connected to the pulse width modulator 43. When the light-emitting diode of the optocoupler 72 is driven, the phototransistor turns on or off, thereby changing the current path or level in the pulse width modulator 43, affecting the duty cycle of the pulse width modulation signal.

[0067] In some embodiments, such as Figure 2 As shown, the dual-transistor flyback power supply circuit also includes an auxiliary power supply coil 81. The auxiliary power supply coil 81 is magnetically coupled to the second primary coil 21 and electrically coupled to the pulse width modulator 43. The auxiliary power supply coil 81 can detect the frequency and trough of the voltage waveform of the second primary coil 21 and provide it to the pulse width modulator 43. The pulse width modulator 43 can simultaneously turn on the first switch 31 and the second switch 32 when the voltage waveform of the second primary coil 21 is at its trough.

[0068] When the voltage waveform of the second primary winding 21 is at its lowest point, the auxiliary power supply winding 81 sends a signal to the pulse width modulator 43. Based on the signal received from the auxiliary power supply winding 81, the pulse width modulator 43 triggers the first switch 31 and the second switch 32 to conduct when it detects that the voltage waveform is at its lowest point. By turning on the switches at the lowest point of the voltage waveform, energy loss during the switching process can be reduced. Secondly, due to the use of valley switching, the peak reverse voltage experienced by the secondary rectifier is correspondingly reduced, which helps to improve its reliability and lifespan. Furthermore, using a power factor correction or variable power factor correction output voltage can maintain efficient operation of the dual-transistor flyback power supply circuit under low-voltage input conditions.

[0069] The dual-transistor quasi-resonant dual-transistor flyback power supply circuit has low requirements for the leakage inductance of the flyback transformer 20, making mass production simpler and allowing the use of low-cost magnetic core materials. Secondly, because the dual-transistor quasi-resonant dual-transistor flyback power supply circuit clamps the drain overshoot voltage to the input voltage and has frequency dithering and valley switching characteristics, it has good electromagnetic interference suppression effect.

[0070] In some embodiments, such as Figure 2 As shown, the dual-transistor flyback power supply circuit also includes capacitor 82 (also referred to as the fourth capacitor) and a fourth diode 83. Capacitor 82 is electrically coupled to both ends of the auxiliary power supply coil 81. The fourth diode 83 is electrically coupled between the auxiliary power supply coil 81 and capacitor 82, and the cathode of the fourth diode 83 is electrically coupled to the DC power supply terminal.

[0071] When the output of the pulse width modulator 43 goes low, the current in the first primary coil 11 is cut off, and the energy previously stored in the magnetic field needs to be released. At this time, the voltage across the first primary coil 11 reverses. Due to the presence of the fourth diode 83, current can flow from the second terminal of the first primary coil 11 to the capacitor 82, thereby storing this recovered energy. The energy stored in the capacitor 82 can be reused in subsequent cycles, for example, as additional energy to supply the system at the beginning of the next pulse width modulation cycle, thereby improving the efficiency of the entire dual-transistor flyback power supply circuit.

[0072] The various embodiments of this disclosure have been described above. These descriptions are exemplary and not exhaustive, and are not limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or technical improvements to the embodiments in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A two-transistor flyback power supply circuit, characterized by comprising: include: The drive transformer (10) includes a first primary winding (11), a first secondary winding (12), and a second secondary winding (13); The flyback main transformer (20) includes a second primary winding (21) and a third secondary winding (22); The first switch (31) has a first electrode adapted to be electrically coupled to the bus (100), the second electrode of the first switch (31) is electrically coupled to the first end of the second primary coil (21) and the second end of the first secondary coil (12), and the control electrode of the first switch (31) is electrically coupled to the first end of the first secondary coil (12). The second switch (32) has its first electrode electrically coupled to the second end of the second primary coil (21), its second electrode electrically coupled to the second end of the second secondary coil (13) and the bus ground, and its control electrode electrically coupled to the first end of the second secondary coil (13); and The driving circuit (40) is electrically coupled to both ends of the first primary coil (11) to transmit a pulse width modulation signal to the first primary coil (11). The driving circuit (40) is adapted to be electrically coupled to the DC power supply terminal. When the pulse width modulation signal is a high-level signal, the first primary coil (11) is energized, and when the pulse width modulation signal is a low-level signal, the excess current generated by the magnetic field energy stored in the first primary coil (11) flows to the DC power supply terminal.

2. The dual-tub reverse flyback power supply circuit according to claim 1, characterized by, The driving circuit (40) includes: The third switch (41) has its first electrode electrically coupled to the second end of the first primary coil (11), and its second electrode electrically coupled to the bus ground. The first diode (42) has its anode electrically coupled to the second end of the first primary coil (11), and its cathode is adapted to be electrically coupled to the DC power supply terminal. A pulse width modulator (43) is electrically coupled to the control electrode of the third switch (41) and the first terminal of the first primary coil (11); and The first resistor (44) is electrically coupled between the control electrode of the third switch (41) and the bus ground.

3. The dual-tub reverse flyback power supply circuit according to claim 2, characterized by, The driving circuit (40) further includes: A bidirectional Zener diode (45) is electrically coupled at one end to the cathode of the first diode (42) and at the other end to the DC power supply terminal.

4. The dual-transistor flyback power supply circuit according to any one of claims 1 to 3, characterized in that, Also includes: A first regulating circuit (50) is electrically coupled to both ends of the first secondary coil (12) and to the control electrode of the first switching transistor (31). The first regulating circuit (50) is adapted to turn on the first switching transistor (31) when the first secondary coil (12) generates a high-level signal, and is adapted to turn off the first switching transistor (31) when the first secondary coil (12) generates a low-level signal; and The second adjustment circuit (60) is electrically coupled to both ends of the second secondary coil (13) and to the control electrode of the second switch (32). The second adjustment circuit (60) is adapted to turn on the second switch (32) when the second secondary coil (13) generates a high-level signal, and is adapted to turn off the second switch (32) when the second secondary coil (13) generates a low-level signal.

5. The dual-tub reverse flyback power supply circuit according to claim 4, characterized by, The first adjustment circuit (50) includes: A second diode (51), the cathode of which is electrically coupled to the control electrode of the first switch (31), and the anode of which is electrically coupled to the first end of the first secondary coil (12); and The first P-type transistor (52) has its first electrode electrically coupled to the cathode of the second diode (51), its control electrode electrically coupled to the anode of the second diode (51), and its second electrode electrically coupled to the second end of the first secondary coil (12). The second regulating circuit (60) includes: A third diode (61), the cathode of which is electrically coupled to the control electrode of the second switch (32), and the anode of which is electrically coupled to the first end of the second secondary coil (13); and The second P-type transistor (62) has its first electrode electrically coupled to the cathode of the third diode (61), its control electrode electrically coupled to the anode of the third diode (61), and its second electrode electrically coupled to the second end of the second secondary coil (13).

6. The dual-tub reverse flyback power supply circuit according to claim 5, characterized by, The first adjustment circuit (50) further includes: The second resistor (53) is electrically coupled between the control electrode of the first switch (31) and the first electrode of the first P-type transistor (52); The second adjustment circuit (60) further includes: The third resistor (63) is electrically coupled between the control electrode of the second switch (32) and the first electrode of the second P-type transistor (62).

7. The dual-tub reverse flyback power supply circuit according to claim 6, characterized by, The first adjustment circuit (50) further includes: The fourth resistor (54) is electrically coupled between the control electrode of the first switch (31) and the second electrode of the first P-type transistor (52), and the resistance of the fourth resistor (54) is greater than the on-resistance of the first P-type transistor (52). The second adjustment circuit (60) further includes: The fifth resistor (64) is electrically coupled between the control electrode of the second switch (32) and the second electrode of the second P-type transistor (62), and the resistance of the fifth resistor (64) is greater than the on-resistance of the second P-type transistor (62).

8. The dual-tub reverse flyback power supply circuit according to claim 2, characterized by, Also includes: The feedback circuit (70) is electrically coupled to the third secondary coil (22) and the pulse width modulator (43). The feedback circuit (70) is adapted to detect the voltage value output by the third secondary coil (22) and provide it to the pulse width modulator (43). The pulse width modulator (43) is adapted to control the duty cycle of the pulse width modulation signal based on the voltage value.

9. The dual-tub reverse flyback power supply circuit according to claim 2, characterized by, Also includes: An auxiliary power supply coil (81) is magnetically coupled to the second primary coil (21) and electrically coupled to the pulse width modulator (43). The auxiliary power supply coil (81) is adapted to detect the frequency and trough of the voltage waveform of the second primary coil (21) and provide it to the pulse width modulator (43). The pulse width modulator (43) is adapted to simultaneously turn on the first switch (31) and the second switch (32) when the voltage waveform of the second primary coil (21) is at its trough.

10. The dual-transistor flyback power supply circuit according to claim 9, characterized in that, Also includes: The capacitor (82) is electrically coupled to both ends of the auxiliary power supply coil (81); as well as The fourth diode (83) is electrically coupled between the auxiliary power supply coil (81) and the capacitor (82), and the cathode of the fourth diode (83) is electrically coupled to the DC power supply terminal.

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