A power supply device and a flyback circuit thereof

Abstract

This application discloses a power supply device and its flyback circuit, comprising: a rectifier and filter circuit; a first end of a primary winding connected to the output end of the rectifier and filter circuit; a second end of the primary winding grounded through a first switching circuit; a first output circuit connected to a secondary winding, and a second output circuit connected to an auxiliary winding; a second switching circuit connected to both the auxiliary winding and the second output circuit; when the control circuit controls the first switching circuit to turn on and the second switching circuit to turn off, the current in the primary winding gradually increases; when the control circuit controls the first switching circuit to turn off and the second switching circuit to turn off, the first output circuit outputs a first voltage; when the control circuit controls the first switching circuit to turn off, the second switching circuit is turned on at a preset time threshold, and the second output circuit outputs a second voltage. This effectively suppresses inrush current and improves the stability of power conversion on the input side.

Description

Technical Field

[0001] This application relates to the field of power supply technology, and in particular to a power supply device and its flyback circuit. Background Technology

[0002] With the rapid development of switching power supplies, switching power supplies typically include flyback circuits. These flyback circuits consist of a transformer and a switch, with the switch connected in series with the primary winding of the transformer.

[0003] When the switch is on, current flows through the primary winding of the transformer in the flyback circuit, and energy is stored in the form of a magnetic field. When the switch is off, the current in the primary winding of the transformer decreases rapidly, and the energy stored in the leakage inductance is released. This released energy forms a resonant circuit with the capacitance of the flyback circuit, generating high-frequency oscillations. The voltage in the primary winding of the transformer rises rapidly, forming a voltage spike. This voltage spike may damage or malfunction the switch, resulting in poor stability. Utility Model Content

[0004] This application mainly provides a power supply device and its flyback circuit to solve the problem of poor stability.

[0005] This application provides a flyback circuit for use in a power supply device, the flyback circuit comprising:

[0006] A rectifier and filter circuit, wherein the input terminal of the rectifier and filter circuit receives the input voltage;

[0007] A transformer includes a primary winding, a secondary winding, and an auxiliary winding, wherein the first end of the primary winding is connected to the output end of the rectifier and filter circuit;

[0008] A first switching circuit is used, wherein the second end of the primary winding is grounded through the first switching circuit;

[0009] A first output circuit and a second output circuit, wherein the first output circuit is connected to the secondary winding and the second output circuit is connected to the auxiliary winding;

[0010] The second switching circuit is connected to the auxiliary winding and the second output circuit, respectively.

[0011] The control circuit is connected to the first switch circuit and the second switch circuit respectively;

[0012] When the control circuit controls the first switching circuit to be turned on and the second switching circuit to be turned off, the current in the primary winding gradually increases.

[0013] When the control circuit controls the first switch circuit to open and the second switch circuit to open, the first output circuit outputs a first voltage.

[0014] When the control circuit controls the first switching circuit to be disconnected, the control circuit controls the second switching circuit to be turned on at preset time threshold intervals, the second output circuit outputs a second voltage, and the first switching circuit remains disconnected.

[0015] The flyback circuit further includes a first feedback circuit and a second feedback circuit. The first feedback circuit is connected between the first output circuit and the control circuit, and the second feedback circuit is connected between the second output circuit and the control circuit.

[0016] The control circuit is used to receive a first feedback signal from the first feedback circuit and control the conduction time of the first switching circuit based on the first feedback signal.

[0017] The control circuit is used to receive a second feedback signal from the second feedback circuit and control the conduction time of the second switching circuit based on the second feedback signal.

[0018] The second output circuit includes a first capacitor, a second capacitor, a first diode, and a Zener diode. The first end of the auxiliary winding is connected to one end of the first capacitor and one end of the second capacitor. The second end of the auxiliary winding is connected to the other end of the first capacitor and the first end of the second switching circuit. The other end of the second capacitor is connected to the anode of the first diode. The cathode of the first diode is connected to the cathode of the Zener diode. The anode of the Zener diode is connected to the second end of the second switching circuit.

[0019] Specifically, when the second voltage is greater than or equal to the voltage regulation value of the Zener diode, the Zener diode is turned on and used for current shunting; when the second voltage is less than the voltage regulation value of the Zener diode, the Zener diode is turned off.

[0020] Wherein, when the second voltage is greater than or equal to the voltage regulation value of the Zener diode, the Zener diode is turned on, and the control circuit is used to detect that the second feedback signal is greater than or equal to the first preset voltage, and reduce the on-time of the second switching circuit to reduce the second voltage;

[0021] When the second voltage is less than the voltage regulation value of the Zener diode, the Zener diode is turned off. The control circuit is used to detect that the second feedback signal is less than the second preset voltage, and increase the conduction time of the second switching circuit to increase the second voltage.

[0022] The second switching circuit includes a second switching transistor, the first end of which is connected to the second end of the auxiliary winding, and the second end of which is connected to the positive terminal of the Zener diode.

[0023] The control circuit includes a control chip and a first optocoupler circuit. The first end of the first optocoupler circuit is connected to the control chip, the fourth end of the first optocoupler circuit is connected to the third end of the second switching transistor, and the second and third ends of the first optocoupler circuit are grounded.

[0024] The first switching circuit includes a first switching transistor, the first end of the first switch is connected to the second end of the primary winding, the second end of the first switch is grounded, and the third end of the first switch is connected to the control circuit.

[0025] The first output circuit includes a second diode and a third capacitor. The first end of the secondary winding is connected to one end of the third capacitor through the second diode, and the second end of the secondary winding is connected to the other end of the third capacitor.

[0026] The first feedback circuit includes a second optocoupler circuit, the fourth terminal of which is connected to the control circuit, the first terminal of which is connected between the second diode and the third capacitor, and the second and third terminals of which are grounded.

[0027] The second feedback circuit includes a third optocoupler circuit, the fourth terminal of which is connected to the control circuit, the first terminal of which is connected to the second output circuit, and the second and third terminals of which are grounded.

[0028] This application also provides a power supply device including the flyback circuit described above.

[0029] The beneficial effects of this application are as follows: The flyback circuit of this application includes a rectifier filter circuit, a transformer, a first switching circuit, a first output circuit, a second output circuit, a second switching circuit, and a control circuit; the input terminal of the rectifier filter circuit receives the input voltage; the transformer includes a primary winding, a secondary winding, and an auxiliary winding; the first end of the primary winding is connected to the output terminal of the rectifier filter circuit; the second end of the primary winding is grounded through the first switching circuit; the first output circuit is connected to the secondary winding; the second output circuit is connected to the auxiliary winding; the second switching circuit is connected to both the auxiliary winding and the second output circuit; the control circuit is connected to both the first and second switching circuits; when the control circuit controls the first switching circuit to be on and the second switching circuit to be off, the current in the primary winding gradually increases; when the control circuit controls the first switching circuit to be off and the second switching circuit to be off, the first output circuit outputs a first voltage; when the control circuit controls the first switching circuit to be off, the control circuit controls the second switching circuit to be on at preset time threshold intervals, the second output circuit outputs a second voltage, and the first switching circuit remains off. By controlling the on / off states of the first and second switching circuits at different stages, the energy storage and release process of the primary winding can be actively managed. During the primary-side energy storage stage, controlling the first switching circuit to be on and the second switching circuit to be off allows the current in the primary winding to gradually build up, effectively suppressing inrush current and improving the smoothness of the input-side power conversion. After the first switching circuit is off, energy is released and resonantly transferred to the secondary and auxiliary windings sequentially, achieving efficient and stable power supply to the first and second output circuits respectively. In particular, the control circuit precisely achieves non-overlapping conduction of the first and second switching circuits through a preset time threshold. The resonant process allows the energy of the primary winding to be more fully transferred to the auxiliary winding, improving energy utilization efficiency, significantly reducing energy loss, effectively reducing device heating, and improving the system's energy efficiency ratio. Furthermore, the multi-path distribution and resonant energy recovery design not only improves the power supply stability of the main and auxiliary outputs but also reduces the stress and failure probability of the switching transistors, thereby significantly enhancing the overall stability and reliability of the circuit. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0031] Figure 1 This is a schematic diagram of the framework of an embodiment of the flyback circuit of this application;

[0032] Figure 2 yes Figure 1 A circuit diagram of one embodiment of a flyback circuit. Detailed Implementation

[0033] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0035] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order, or primary and secondary relationship of the indicated technical features.

[0036] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0037] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0038] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0039] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a connection between two components or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0040] Please see Figure 1 and Figure 2 As shown, Figure 1 This is a schematic diagram of the framework of one embodiment of the flyback circuit of this application. Figure 2 yes Figure 1 A circuit diagram of one embodiment of a flyback circuit. The flyback circuit 100 of this embodiment includes a rectifier filter circuit 10, a transformer 20, a first switching circuit 30, a first output circuit 40, a second output circuit 50, a second switching circuit 60, and a control circuit 70. The flyback circuit 100 is applied to a power supply device, which includes, but is not limited to, a charger, adapter, or switching power supply.

[0041] The input terminal of the rectifier-filter circuit 10 receives the input voltage, and the rectifier-filter circuit 10 is used to rectify and filter the input voltage. For example, the rectifier-filter circuit 10 receives AC mains power and uses it to rectify and filter the AC mains power.

[0042] In some embodiments, the rectifier-filter circuit 10 includes a rectifier bridge 11 and a filter circuit 12. The second and third terminals of the rectifier bridge 11 serve as the input terminals of the rectifier-filter circuit 10, and the first terminal of the rectifier bridge 11 serves as the output terminal of the rectifier-filter circuit 10. The first and fourth terminals of the rectifier bridge 11 are connected to the filter circuit 12. The filter circuit 12 includes a fourth capacitor C4 and a fifth capacitor C5. One end of the fourth capacitor C4 and one end of the fifth capacitor C5 are connected to the first terminal of the rectifier bridge 11, and the other ends of the fourth capacitor C4, the other ends of the fifth capacitor C5, and the fourth terminal of the rectifier bridge 11 are grounded. The fourth capacitor C4 and the fifth capacitor C5 are used to filter the voltage output by the rectifier bridge 11.

[0043] The transformer 20 includes a primary winding 21, a secondary winding 22, and an auxiliary winding 23. The second end of the primary winding 21, the first end of the secondary winding 22, and the first end of the auxiliary winding 23 are terminals with the same name. The first end of the primary winding 21 is connected to the output terminal of the rectifier and filter circuit 10, that is, the first end of the primary winding 21 is connected to the first end of the rectifier bridge 11.

[0044] The second end of the primary winding 21 is grounded through the first switching circuit 30; the first output circuit 40 is connected to the secondary winding 22, and the second output circuit 50 is connected to the auxiliary winding 23. The second switching circuit 60 is connected to both the auxiliary winding 23 and the second output circuit 50, and is used to control the connection between the auxiliary winding 23 and the second output circuit 50.

[0045] The control circuit 70 is connected to the first switch circuit 30 and the second switch circuit 60 respectively. The control circuit 70 is used to control the first switch circuit 30 to be turned on or off, and to control the second switch circuit 60 to be turned on or off.

[0046] When the control circuit 70 controls the first switching circuit 30 to turn on and the second switching circuit 60 to turn off, the current in the primary winding 21 gradually increases.

[0047] Specifically, when the control circuit 70 controls the first switching circuit 30 to be turned on and the second switching circuit 60 to be turned off, the rectifier filter circuit 10, the primary winding 21 and the first switching circuit 30 are connected, the primary winding 21 of the transformer 20 is energized, the current of the primary winding 21 gradually increases, and the transformer 20 stores energy (i.e. the current of the primary winding 21) in the magnetic core of the transformer 20 in the form of a magnetic field, that is, the energy stored in the transformer 20.

[0048] When the control circuit 70 controls the first switch circuit 30 to open and the second switch circuit 60 to open, the first output circuit 40 outputs the first voltage.

[0049] Specifically, when the control circuit 70 controls the first switching circuit 30 to open and the second switching circuit 60 to open, the current in the primary winding 21 decreases rapidly, the energy stored in the transformer 20 begins to be released, and a portion of the energy stored in the transformer 20 is transferred to the secondary winding 22 through the coupling effect. At this time, the first output circuit 40 connected to the secondary winding 22 outputs the first voltage.

[0050] When the control circuit 70 controls the first switching circuit 30 to be disconnected, the control circuit 70 controls the second switching circuit 60 to be turned on at preset time threshold intervals, the second output circuit 50 outputs the second voltage, and the first switching circuit 40 remains disconnected.

[0051] Specifically, when the control circuit 70 controls the first switching circuit 30 to be disconnected, the control circuit 70 controls the second switching circuit 60 to be turned on at preset time threshold intervals, and the second output circuit 50, the second switching circuit 60 and the auxiliary winding 23 are connected; the energy released by the primary winding 21 (another part of the energy stored in the transformer 20) is transmitted to the auxiliary winding 23 through resonance, so that the second output circuit 50 connected to the auxiliary winding 23 outputs a second voltage, and the first switching circuit 30 remains disconnected.

[0052] In this embodiment, when the control circuit 70 controls the first switching circuit 30 to be turned on and the second switching circuit 60 to be turned off, the current in the primary winding 21 gradually increases. When the control circuit 70 controls the first switching circuit 30 to be turned off and the second switching circuit 60 to be turned off, the first output circuit 40 outputs a first voltage. When the control circuit 70 controls the first switching circuit 30 to be turned off, the control circuit 70 controls the second switching circuit 60 to be turned on at preset time thresholds, and the second output circuit 50 outputs a second voltage. By controlling the on and off of the first switching circuit 30 and the second switching circuit 60 at different stages, the energy storage and release process of the primary winding 21 can be actively managed. During the primary-side energy storage stage, by controlling the first switching circuit 30 to be turned on and the second switching circuit 70 to be turned off, the current in the primary winding 21 is gradually built up, effectively suppressing inrush current and improving the stability of the power conversion on the input side. After the first switching circuit 30 is disconnected, energy is released and resonantly transferred to the secondary winding 22 and the auxiliary winding 23 in sequence, thereby achieving efficient and stable power supply to the first output circuit 40 and the second output circuit 50, respectively. In particular, the control circuit 70 precisely achieves non-overlapping conduction of the first switching circuit 30 and the second switching circuit 70 through a preset time threshold. Through the resonance process, the energy of the primary winding 21 is more fully transferred to the auxiliary winding 23, improving energy utilization efficiency, significantly reducing energy loss, effectively reducing device heating, and improving the system energy efficiency ratio. In addition, the design of multi-path distribution and resonant energy recovery not only improves the power supply stability of the main and auxiliary outputs, but also reduces the stress and failure probability of the switching transistors, thereby significantly enhancing the overall stability and reliability of the circuit.

[0053] Compared to existing LDO (Low Dropout Regulator) modules, in this embodiment, the auxiliary winding 23 is directly powered through the second output circuit 50, eliminating the need for an LDO module. This simplifies the flyback circuit 100, reduces the number of external components and circuit complexity, decreases the PCB (Printed Circuit Board) area occupied, and lowers costs. Unlike existing RCD (Resistor-Capacitor-Diode) circuits where the resistor continuously heats up, the flyback circuit 100 in this embodiment eliminates the need for an RCD circuit, avoiding the problem of continuous resistor heating and extending component lifespan. Furthermore, by controlling the second switching circuit 60 to conduct at preset time threshold intervals when the first switching circuit 30 is disconnected (i.e., the first and second switching circuits 30 and 60 do not conduct simultaneously), precise control of the interval between the first and second switching circuits 30 and 60's conduction improves the efficiency of energy transfer from the primary winding 21 to the auxiliary winding 23 via resonance.

[0054] According to some embodiments of this application, the flyback circuit 100 of this embodiment further includes a first feedback circuit 80 and a second feedback circuit 90. The first feedback circuit 80 is connected between the first output circuit 40 and the control circuit 70, and the second feedback circuit 90 is connected between the second output circuit 50 and the control circuit 70.

[0055] The control circuit 70 is used to receive a first feedback signal from the first feedback circuit 80 and control the conduction time of the first switching circuit 30 based on the first feedback signal.

[0056] The control circuit 70 receives a second feedback signal from the second feedback circuit 90 and controls the conduction time of the second switching circuit 60 based on the second feedback signal. Both the first and second feedback signals can be feedback voltages.

[0057] In some embodiments, the control circuit 70 has a reference voltage. The control circuit 70 compares a first feedback signal with the reference voltage and controls the on-time of the first switching circuit 30 based on the comparison result to stabilize the first voltage output by the first output circuit 40. The control circuit 70 also compares a second feedback signal with the reference voltage and controls the on-time of the second switching circuit 60 based on the comparison result to stabilize the second voltage output by the second output circuit 50. For example, the reference voltage is 2.5V.

[0058] In this embodiment, the control circuit 70 receives a first feedback signal from the first feedback circuit 80 and controls the conduction time of the first switching circuit 30 based on the first feedback signal. The control circuit 70 also receives a second feedback signal from the second feedback circuit 90 and controls the conduction time of the second switching circuit 60 based on the second feedback signal. By doing so, the stability of the first and second voltages can be improved, thereby improving the stability of the flyback circuit 100.

[0059] According to some embodiments of this application, the second output circuit 50 of this embodiment includes a first capacitor C1, a second capacitor C2, a first diode D1, and a Zener diode Dz.

[0060] The first end of the auxiliary winding 23 is connected to one end of the first capacitor C1 and one end of the second capacitor C2, respectively. The second end of the auxiliary winding 23 is connected to the other end of the first capacitor C1 and the first end of the second switching circuit 60, respectively. The other end of the second capacitor C2 is connected to the positive terminal of the first diode D1. The negative terminal of the first diode D1 is connected to the negative terminal of the Zener diode Dz. The positive terminal of the Zener diode Dz is connected to the second end of the second switching circuit 60.

[0061] In some embodiments, the second feedback circuit 90 is connected to the negative terminal of the first diode D1 and the negative terminal of the Zener diode Dz, respectively, to obtain the second voltage output by the second output circuit 50. The second feedback circuit 90 is used to convert the second voltage into a second feedback signal.

[0062] When the control circuit 70 controls the second switching circuit 60 to open, the second output circuit 50 is not connected to the auxiliary winding 23. When the control circuit 70 controls the second switching circuit 60 to open, the second output circuit 50 is connected to the auxiliary winding 23. The energy released by the primary winding 21 (another part of the energy stored in the transformer 20) is transferred to the first capacitor C1 through resonance. The first capacitor C1 is used to absorb the energy released by the primary winding 21. Compared with the existing RCD circuit, it avoids resistance loss and can improve the efficiency of the energy released by the primary winding 21 being transferred to the auxiliary winding 23 through resonance, thus improving the effect of EMI (Electromagnetic Interference).

[0063] According to some embodiments of this application, in this embodiment, when the second voltage is greater than or equal to the regulated voltage of the Zener diode Dz, the Zener diode Dz is turned on, and the Zener diode Dz is used for current shunting. That is, when the Zener diode Dz is turned on, the Zener diode Dz shunts the second voltage to reduce the second voltage. When the Zener diode Dz is turned on, the Zener diode Dz can quickly clamp the voltage, which can prevent overvoltage damage to the subsequent circuit connected to the second output circuit 50.

[0064] When the second voltage is less than the Zener diode Dz's regulated voltage, Zener diode Dz is turned off and does not consume the energy of auxiliary winding 23.

[0065] In this embodiment, when the second voltage is greater than or equal to the regulated voltage of Zener diode Dz, Zener diode Dz conducts and is used for current shunt; when the second voltage is less than the regulated voltage of Zener diode Dz, Zener diode Dz is cut off. That is, through the coupling characteristics of Zener diode Dz and auxiliary winding 23, the second voltage can be adjusted and stabilized via Zener diode Dz, thereby achieving stable power supply over a wide input voltage range, eliminating the need for an LDO module and reducing costs.

[0066] According to some embodiments of this application, in this embodiment, when the second voltage is greater than or equal to the regulated voltage value of the Zener diode Dz, the Zener diode Dz is turned on, and the control circuit 70 is used to detect that the second feedback signal is greater than or equal to the first preset voltage, and reduce the conduction time of the second switching circuit 60 to reduce the second voltage.

[0067] When the second voltage is less than the Zener diode Dz's regulated voltage, the Zener diode Dz is turned off. The control circuit 70 is used to detect that the second feedback signal is less than the second preset voltage, and increase the conduction time of the second switching circuit 60 to increase the second voltage.

[0068] In some embodiments, the load is connected in parallel with the Zener diode Dz, and the second voltage of the second output circuit 50 is used to supply power to the load.

[0069] When the load current is small, the second voltage is prone to be too high. At this time, the second voltage is greater than or equal to the voltage regulation value of the Zener diode Dz. The Zener diode Dz is turned on and used for current shunting. The second feedback signal detected by the second feedback circuit 90 is too high, that is, the second feedback signal is greater than the first preset voltage. Then the control circuit 70 is used to reduce the conduction time of the second switching circuit 60. The resonance time of the auxiliary winding 23 and the first capacitor C1 is reduced, reducing the energy recovered by the auxiliary winding 23 from the primary winding 21, thereby reducing the second voltage.

[0070] When the load current is large, the second voltage is low. At this time, the second voltage is less than the voltage regulation value of the Zener diode Dz, so the Zener diode Dz is cut off. The second feedback signal detected by the second feedback circuit 90 is low. That is, the control circuit 70 detects that the second feedback signal is less than the second preset voltage and increases the conduction time of the second switching circuit 60. The resonance time between the auxiliary winding 23 and the first capacitor C1 increases, and the auxiliary winding 23 recovers the energy released by the primary winding 21, thereby increasing the second voltage. The second preset voltage is less than or equal to the first preset voltage.

[0071] In this embodiment, when the second voltage is greater than or equal to the regulated voltage of the Zener diode Dz, the Zener diode Dz is turned on. The control circuit 70 detects that the second feedback signal is greater than or equal to the first preset voltage and reduces the conduction time of the second switching circuit 60 to reduce the second voltage. When the second voltage is less than the regulated voltage of the Zener diode Dz, the Zener diode Dz is turned off. The control circuit 70 detects that the second feedback signal is less than the second preset voltage and increases the conduction time of the second switching circuit 60 to increase the second voltage. Through the above method, the second feedback circuit 90 and the control circuit 70 form a feedback loop, which can realize dynamic control of the conduction time of the second switching circuit 60, realize automatic adjustment of the proportion of energy recovered by the auxiliary winding 23 from the primary winding 21 based on load changes, and improve the overall efficiency of the flyback circuit 100.

[0072] In some embodiments, the rectifier-filter circuit 10 receives an input voltage range of 90V-264V, which is a wide input voltage range. When the control circuit 70 controls the first switching circuit 30 to open, the primary winding 21 is equivalent to a leakage inductance. The energy stored in the leakage inductance (i.e., the energy released by the primary winding 21) is related to the input voltage. For example, the larger the input voltage, the more energy is stored in the leakage inductance; the smaller the input voltage, the less energy is stored in the leakage inductance.

[0073] When the input voltage is high, for example, greater than 220V, the leakage inductance stores more energy, the auxiliary winding 23 induces more energy, and the second voltage rises. At this time, the second voltage is greater than or equal to the voltage regulation value of the Zener diode Dz, the Zener diode Dz is turned on, and the Zener diode Dz is used for shunt current. The control circuit 70 reduces the conduction time of the second switching circuit 60, the resonance time of the auxiliary winding 23 and the first capacitor C1 is reduced, the auxiliary winding 23 recovers the energy released by the primary winding 21, and thus reduces the second voltage, which can avoid overvoltage of the second voltage.

[0074] When the input voltage is low, such as less than 150V, the energy stored in the leakage inductance is small, and the energy induced in the auxiliary winding 23 is also small, resulting in a decrease in the second voltage. At this time, the second voltage is less than the Zener diode Dz's voltage regulation value, causing Dz to turn off. The control circuit 70 increases the conduction time of the second switching circuit 60, increasing the resonance duration between the auxiliary winding 23 and the first capacitor C1. This increases the energy recovered by the auxiliary winding 23 from the primary winding 21, thereby increasing the second voltage and preventing undervoltage. Therefore, this embodiment can achieve stable power supply over a wide input voltage range.

[0075] According to some embodiments of this application, the second switching circuit 60 of this embodiment includes a second switching transistor Q2, the first end of the second switching transistor Q2 is connected to the second end of the auxiliary winding 23, and the second end of the second switching transistor Q2 is connected to the positive terminal of the Zener diode Dz.

[0076] The control circuit 70 includes a control chip U1 and a first optocoupler circuit OC1. The first terminal of the first optocoupler circuit OC1 is connected to the control chip U1, the fourth terminal of the first optocoupler circuit OC1 is connected to the third terminal of the second switch Q2, and the second and third terminals of the first optocoupler circuit OC1 are grounded.

[0077] In this embodiment, the second switch Q2 can be an N-type MOSFET, with its first terminal being the drain, its second terminal being the source, and its third terminal being the gate. In other embodiments, the second switch Q2 can be other types of switches.

[0078] In this embodiment, the control chip U1 controls the second switching transistor Q2 through the first optocoupler circuit OC1. The first optocoupler circuit OC1 achieves electrical isolation, that is, the primary winding 21 and the auxiliary winding 23 are electrically isolated, which prevents the high voltage of the primary winding 21 from entering the auxiliary winding 23 and causing damage, thereby improving the EMI (Electromagnetic Interference) performance.

[0079] According to some embodiments of this application, the first switching circuit 30 of this embodiment includes a first switching transistor Q1, the first end of the first switching transistor Q1 is connected to the second end of the primary winding 21, the second end of the first switching transistor Q1 is grounded, and the third end of the first switching transistor Q1 is connected to the control circuit 70.

[0080] In this embodiment, the first switch Q1 can be an N-type MOSFET, with its first terminal being the drain, its second terminal being the source, and its third terminal being the gate. In other embodiments, the first switch Q1 can be other types of switches.

[0081] Specifically, the third terminal of the first switching transistor Q1 is connected to the control chip U1, which controls the first switching transistor Q1 via a PWM (Pulse Width Modulation) signal. The control chip U1 adjusts the duty cycle of the PWM signal based on the first feedback signal to improve the stability of the first voltage.

[0082] In some embodiments, the first output circuit 40 includes a second diode D2 and a third capacitor C3. The first end of the secondary winding 22 is connected to one end of the third capacitor C3 through the second diode D2, and the second end of the secondary winding 22 is connected to the other end of the third capacitor C3.

[0083] When the control chip U1 controls the first switching transistor Q1 to be turned on, the second diode D2 is in the off state, and the first output circuit 40 has no voltage output. When the control chip U1 controls the first switching transistor Q1 to be turned off, the second diode D2 is in the on state, and the first output circuit 40 outputs the first voltage.

[0084] In some embodiments, the first feedback circuit 80 includes a second optocoupler circuit OC2, the fourth terminal of the second optocoupler circuit OC2 is connected to the control circuit 70, the first terminal of the second optocoupler circuit OC2 is connected between the second diode D2 and the third capacitor C3, and the second and third terminals of the second optocoupler circuit OC2 are grounded.

[0085] The second feedback circuit 90 includes a third optocoupler circuit OC3. The fourth terminal of the third optocoupler circuit OC3 is connected to the control circuit 70. The first terminal of the third optocoupler circuit OC3 is connected to the second output circuit 50. The second and third terminals of the third optocoupler circuit OC3 are grounded.

[0086] In this circuit, the fourth terminal of the second optocoupler circuit OC2 is connected to the control chip U1; the first terminal of the third optocoupler circuit OC3 is connected to the negative terminal of the first diode D1 and the negative terminal of the Zener diode Dz, and the fourth terminal of the third optocoupler circuit OC3 is connected to the control chip U1.

[0087] Specifically, the light-emitting diode side of the second optocoupler circuit OC2 receives the first voltage output by the first output circuit 40, and the light intensity of the light-emitting diode of the second optocoupler circuit OC2 changes with the first voltage. The photodiode side of the second optocoupler circuit OC2 is connected to the control chip U1. The second optocoupler circuit OC2 is used to convert the first voltage into a current input value to control the control chip U1. The control chip U1 is used to control the first switch Q1 to turn on or off based on the first feedback signal of the second optocoupler circuit OC2.

[0088] The LED side of the third optocoupler circuit OC3 receives the second voltage output by the second output circuit 50. The light intensity of the LED in the third optocoupler circuit OC3 changes with the second voltage. The photodiode side of the third optocoupler circuit OC3 is connected to the control chip U1. The third optocoupler circuit OC3 is used to convert the second voltage into a current input value to control the control chip U1. The control chip U1 is used to control the second switch Q2 to be turned on or off through the first optocoupler circuit OC1 based on the second feedback signal of the third optocoupler circuit OC3.

[0089] In some embodiments, the preset time threshold of this application can be equal to 0.2 multiplied by the resonant period, where the resonant period refers to the resonant period formed by the equivalent leakage inductance of the primary winding 21 and the parasitic capacitance of the first switching transistor Q1, which can improve the efficiency of energy released by the primary winding 21 being transferred to the auxiliary winding 23 through resonance. In other embodiments, the preset time threshold can be equal to a coefficient multiplied by the resonant period, where the coefficient ranges from 0.1 to 0.3.

[0090] The resonant frequency formed by the equivalent leakage inductance of the primary winding 21 and the parasitic capacitance of the first switching transistor Q1 can be 5 times the conduction frequency of the second switching transistor Q2. That is, the resonant frequency is far away from the conduction frequency of the second switching transistor Q2, which can improve the EMI effect.

[0091] This application also provides a power supply device, including the flyback circuit 100 described above, which will not be repeated here.

[0092] In this application, when the control circuit 70 controls the first switching circuit 30 to be turned on and the second switching circuit 60 to be turned off, the current in the primary winding 21 gradually increases. When the control circuit 70 controls the first switching circuit 30 to be turned off and the second switching circuit 60 to be turned off, the first output circuit 40 outputs a first voltage. When the control circuit 70 controls the first switching circuit 30 to be turned off, the control circuit 70 controls the second switching circuit 60 to be turned on at preset time thresholds, and the second output circuit 50 outputs a second voltage. By controlling the on and off of the first switching circuit 30 and the second switching circuit 60 at different stages, the energy storage and release process of the primary winding 21 can be actively managed. During the primary-side energy storage stage, by controlling the first switching circuit 30 to be turned on and the second switching circuit 70 to be turned off, the current in the primary winding 21 is gradually built up, effectively suppressing inrush current and improving the stability of the power conversion on the input side. After the first switching circuit 30 is disconnected, energy is released and resonantly transferred to the secondary winding 22 and the auxiliary winding 23 in sequence, thereby achieving efficient and stable power supply to the first output circuit 40 and the second output circuit 50, respectively. In particular, the control circuit 70 precisely achieves non-overlapping conduction of the first switching circuit 30 and the second switching circuit 70 through a preset time threshold. Through the resonance process, the energy of the primary winding 21 is more fully transferred to the auxiliary winding 23, improving energy utilization efficiency, significantly reducing energy loss, effectively reducing device heating, and improving the system energy efficiency ratio. In addition, the design of multi-path distribution and resonant energy recovery not only improves the power supply stability of the main and auxiliary outputs, but also reduces the stress and failure probability of the switching transistors, thereby significantly enhancing the overall stability and reliability of the circuit.

[0093] The above description is merely an embodiment of this application and does not limit the patent scope of this application. Any equivalent structural or procedural transformations made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of this application.

Claims

1. A flyback circuit, characterized in that, Applied to power supply devices, the flyback circuit includes: A rectifier and filter circuit, wherein the input terminal of the rectifier and filter circuit receives the input voltage; A transformer includes a primary winding, a secondary winding, and an auxiliary winding, wherein the first end of the primary winding is connected to the output end of the rectifier and filter circuit; A first switching circuit is used, wherein the second end of the primary winding is grounded through the first switching circuit; A first output circuit and a second output circuit, wherein the first output circuit is connected to the secondary winding and the second output circuit is connected to the auxiliary winding; The second switching circuit is connected to the auxiliary winding and the second output circuit, respectively. The control circuit is connected to the first switch circuit and the second switch circuit respectively; When the control circuit controls the first switching circuit to be turned on and the second switching circuit to be turned off, the current in the primary winding gradually increases. When the control circuit controls the first switch circuit to open and the second switch circuit to open, the first output circuit outputs a first voltage. When the control circuit controls the first switching circuit to be disconnected, the control circuit controls the second switching circuit to be turned on at preset time threshold intervals, the second output circuit outputs a second voltage, and the first switching circuit remains disconnected.

2. The flyback circuit according to claim 1, characterized in that, The flyback circuit further includes a first feedback circuit and a second feedback circuit, wherein the first feedback circuit is connected between the first output circuit and the control circuit, and the second feedback circuit is connected between the second output circuit and the control circuit. The control circuit is used to receive a first feedback signal from the first feedback circuit and control the conduction time of the first switching circuit based on the first feedback signal. The control circuit is used to receive a second feedback signal from the second feedback circuit and control the conduction time of the second switching circuit based on the second feedback signal.

3. The flyback circuit according to claim 2, characterized in that, The second output circuit includes a first capacitor, a second capacitor, a first diode, and a Zener diode. The first end of the auxiliary winding is connected to one end of the first capacitor and one end of the second capacitor, respectively. The second end of the auxiliary winding is connected to the other end of the first capacitor and the first end of the second switching circuit, respectively. The other end of the second capacitor is connected to the anode of the first diode. The cathode of the first diode is connected to the cathode of the Zener diode. The anode of the Zener diode is connected to the second end of the second switching circuit.

4. The flyback circuit according to claim 3, characterized in that, When the second voltage is greater than or equal to the voltage regulation value of the Zener diode, the Zener diode is turned on and used for current shunting; when the second voltage is less than the voltage regulation value of the Zener diode, the Zener diode is turned off.

5. The flyback circuit according to claim 3, characterized in that, When the second voltage is greater than or equal to the voltage regulation value of the Zener diode, the Zener diode is turned on. The control circuit is used to detect that the second feedback signal is greater than or equal to the first preset voltage, and reduce the on-time of the second switching circuit to reduce the second voltage. When the second voltage is less than the voltage regulation value of the Zener diode, the Zener diode is turned off. The control circuit is used to detect that the second feedback signal is less than the second preset voltage, and increase the conduction time of the second switching circuit to increase the second voltage.

6. The flyback circuit according to claim 3, characterized in that, The second switching circuit includes a second switching transistor, the first end of which is connected to the second end of the auxiliary winding, and the second end of which is connected to the positive terminal of the Zener diode. The control circuit includes a control chip and a first optocoupler circuit. The first end of the first optocoupler circuit is connected to the control chip, the fourth end of the first optocoupler circuit is connected to the third end of the second switching transistor, and the second and third ends of the first optocoupler circuit are grounded.

7. The flyback circuit according to claim 2, characterized in that, The first switching circuit includes a first switching transistor, a first terminal of the first switch is connected to the second terminal of the primary winding, a second terminal of the first switch is grounded, and a third terminal of the first switch is connected to the control circuit.

8. The flyback circuit according to claim 7, characterized in that, The first output circuit includes a second diode and a third capacitor. The first end of the secondary winding is connected to one end of the third capacitor through the second diode, and the second end of the secondary winding is connected to the other end of the third capacitor.

9. The flyback circuit according to claim 8, characterized in that, The first feedback circuit includes a second optocoupler circuit, the fourth terminal of the second optocoupler circuit is connected to the control circuit, the first terminal of the second optocoupler circuit is connected between the second diode and the third capacitor, and the second and third terminals of the second optocoupler circuit are grounded. The second feedback circuit includes a third optocoupler circuit, the fourth terminal of which is connected to the control circuit, the first terminal of which is connected to the second output circuit, and the second and third terminals of which are grounded.

10. A power supply device, characterized in that, Includes the flyback circuit as described in any one of claims 1-9.

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