A control circuit and a non-isolated flyback circuit

Abstract

The utility model provides a kind of control circuit and non-isolated flyback circuit, control circuit includes detection unit and timing unit, wherein, the first end of detection unit is connected output feedback signal, second end is connected power supply signal, output end is coupled timing unit, for generating detection signal based on output feedback signal and power supply signal;The input end of timing unit is coupled the output end of detection unit, for generating protection control signal based on detection signal.The utility model is through the signal state of detection feedback pin, when detecting open circuit or short-circuit abnormality, quickly triggers protection mechanism, cuts off output or limit voltage, to effectively protect the equipment of rear stage from damage, effectively improve the reliability and security of system, simplify peripheral protection circuit design, applicable to non-isolated flyback switching power supply application.

Description

Technical Field

[0001] This utility model relates to the field of electronics, specifically, but not limited to, a control circuit and a non-isolated flyback circuit. Background Technology

[0002] In home appliance applications, such as white goods like air conditioners, refrigerators, and washing machines, as well as small appliances like rice cookers and fans, auxiliary power supplies are typically designed using non-isolated topologies to optimize system cost and efficiency. Buck converters and non-isolated flyback converters are two common non-isolated topology solutions. Generally, in low-power applications, Buck converters are more advantageous due to their simpler structure and lower cost; while in higher-power applications, non-isolated flyback converters are a more suitable choice due to their higher conversion efficiency and better cost performance.

[0003] However, non-isolated flyback converters still have certain reliability risks in practical applications, especially when the feedback (FB) circuit fails, which may cause the converter output voltage to rise abnormally, thereby damaging the downstream circuit components. Common failure modes include: (1) FB pin open circuit or short circuit: If the feedback signal fails due to the pin being open or short-circuited, the control loop cannot properly regulate the output voltage, which may lead to uncontrolled output voltage. (2) Upper bias resistor R1 open circuit: If Figure 1 As shown, when the upper bias resistor R1 is open-circuited due to damage to the resistor body or breakage of the PCB trace connected to it, the voltage of the FB pin becomes abnormal, causing the control circuit to misjudge it as a low feedback voltage, and thus continuously increase the output voltage. (3) The lower bias resistor R2 is short-circuited: as shown Figure 2 As shown, when the bias resistor R2 is short-circuited due to the resistor itself or when the FB pin is short-circuited to ground (GND) due to solder bridging, the voltage of the FB pin will be pulled low, which may also trigger the control circuit to incorrectly increase the output voltage.

[0004] In view of this, a new control structure is needed to solve at least some of the above problems. Utility Model Content

[0005] Addressing at least one or more problems in the background art, this utility model proposes a control circuit and a non-isolated flyback circuit. By detecting the signal status of the feedback pin through a built-in detection unit, a protection mechanism is quickly triggered when an open circuit or short circuit abnormality is detected, cutting off the output or limiting the voltage, thereby effectively protecting downstream equipment from damage. This effectively improves the reliability and safety of the system, simplifies the design of the peripheral protection circuit, and is suitable for non-isolated flyback switching power supply applications.

[0006] According to one aspect of the present invention, a control circuit includes:

[0007] The detection unit has an output feedback signal connected to its first end and a power supply signal connected to its second end. The output end is coupled to a timing unit and is used to generate a detection signal based on the output feedback signal and the power supply signal.

[0008] The timing unit, whose input is coupled to the output of the detection unit, is used to generate a protection control signal based on the detection signal.

[0009] Optionally, the detection unit includes:

[0010] The first comparison module has an output feedback signal connected to its first end and a first threshold signal connected to its second end. Its output end is coupled to a logic operation module and is used to generate a first comparison signal based on the output feedback signal and the first threshold signal.

[0011] The second comparison module has a power supply signal connected to its first end, a second threshold signal connected to its second end, and an output terminal coupled to a logic operation module. It is used to generate a second comparison signal based on the power supply signal and the second threshold signal.

[0012] The logic operation module has a first end coupled to the output of the first comparison module, a second end coupled to the output of the second comparison module, and an output end coupled to a timing unit, for generating a detection signal based on the first comparison signal and the second comparison signal.

[0013] Optionally, the first comparison module includes:

[0014] A first voltage source, with its high-potential end coupled to a first comparator and its low-potential end grounded, is used to generate a first threshold signal.

[0015] The first comparator has its non-inverting input coupled to the first voltage source, its inverting input connected to the output feedback signal, and its output input coupled to the logic operation module. It is used to compare the output feedback signal and the first threshold signal and generate a first comparison signal.

[0016] Optionally, the second comparison module includes:

[0017] The second voltage source, with its high-potential end coupled to the second comparator and its low-potential end grounded, is used to generate the second threshold signal.

[0018] The second comparator has a non-inverting input connected to the power supply signal, an inverting input coupled to the second voltage source, and an output coupled to the logic operation module. It is used to compare the power supply signal and the second threshold signal and generate a second comparison signal.

[0019] Optionally, the logic operation module includes:

[0020] The AND gate has its first input terminal coupled to the output terminal of the first comparison module, its second input terminal coupled to the output terminal of the second comparison module, and its output terminal coupled to the timing unit. It is used to perform a logical AND operation on the first comparison signal and the second comparison signal to generate a detection signal.

[0021] Optionally, the detection signal includes a first state signal and a second state signal, wherein the first state signal indicates that the output feedback signal is less than the first threshold signal and the power supply signal is greater than the second threshold signal, and the second state signal indicates that the output feedback signal is greater than or equal to the first threshold signal or the power supply signal is less than or equal to the second threshold signal.

[0022] Optionally, the timing unit includes:

[0023] The timer module, with its input coupled to the output of the detection unit, is used to calculate the duration of the detection signal and output a protection control signal when the duration reaches a target time value.

[0024] Optionally, the protection control signal is a latching signal or a self-resetting signal.

[0025] Optionally, the control circuit further includes:

[0026] The switching transistor, with its control terminal coupled to the output terminal of the timing unit, is used to turn on or off based on a protection control signal.

[0027] According to another aspect of this utility model, a non-isolated flyback circuit includes a transformer, a half-wave rectifier filter circuit, a voltage divider circuit, a switching transistor, and a control circuit for any of the above. One end of the half-wave rectifier filter circuit is coupled to the positive output terminal of the non-isolated flyback circuit, and the other end of the half-wave rectifier filter circuit is coupled to the control circuit. A first end of the switching transistor is coupled to the primary winding of the transformer. A first end of a detection unit in the control circuit is coupled to the voltage divider circuit, a second end of the detection unit is coupled to the half-wave rectifier filter circuit, and the output terminal of a timing unit is coupled to the control terminal of the switching transistor.

[0028] According to another aspect of the present invention, a non-isolated flyback circuit includes a transformer, a half-wave rectifier filter circuit, a voltage divider circuit, and the aforementioned control circuit. One end of the half-wave rectifier filter circuit is coupled to the positive output terminal of the non-isolated flyback circuit, and the other end of the half-wave rectifier filter circuit is coupled to the control circuit. A first end of a detection unit in the control circuit is coupled to the voltage divider circuit, a second end of the detection unit is coupled to the half-wave rectifier filter circuit, and a first end of a switching transistor is coupled to the primary winding of the transformer.

[0029] The control circuit and non-isolated flyback circuit proposed in this invention monitor the open or short circuit faults of the FB pin in real time by setting a detection unit, and quickly trigger the protection mechanism when an abnormality occurs, so as to avoid damage to downstream equipment due to overvoltage, effectively improving the reliability and safety of the system. The open and short circuit protection functions are integrated into the control circuit, simplifying the design of the external protection circuit, reducing the complexity of PCB layout, and lowering the design cost. The control circuit is suitable for various non-isolated flyback switching power supply applications. Attached Figure Description

[0030] The accompanying drawings are provided to further illustrate the present invention and, together with the description, serve to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0031] Figure 1 The circuit diagram of an existing non-isolated flyback converter with an open-circuit fault in resistor R1 is shown.

[0032] Figure 2 The circuit diagram of a non-isolated flyback converter with a short-circuit fault in resistor R2 is shown.

[0033] Figure 3 A control circuit structure diagram of an embodiment of the present invention is shown;

[0034] Figure 4 A non-isolated flyback circuit structure diagram according to an embodiment of the present invention is shown;

[0035] Figure 5 A non-isolated flyback circuit structure diagram of another embodiment of the present invention is shown. Detailed Implementation

[0036] To further understand this utility model, preferred embodiments of this utility model are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of this utility model, and not for limiting the scope of the claims of this utility model.

[0037] The description in this section pertains to only a few typical embodiments, and this utility model is not limited to the scope of the embodiments described. Combinations of different embodiments, substitution of some technical features in different embodiments, and substitution of the same or similar prior art with some technical features in the embodiments are also within the scope of the description and protection of this utility model.

[0038] The terms "coupled" or "connected" in this specification include both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection through an electrically conductive medium like a conductor, which may contain parasitic inductance or capacitance. It can also be a connection through intermediate circuits or components described in the embodiments of this specification. Indirect connections may also include connections through other active or passive devices that achieve the same or similar function, such as connections through switches, signal amplification circuits, follower circuits, or other circuits or components. "Multiple" or "more" indicates two or more.

[0039] A control circuit is provided for implementing open-circuit and short-circuit protection for the feedback pin in a non-isolated flyback circuit. For example... Figure 3 As shown, the control circuit includes a detection unit 1 and a timing unit 2, wherein:

[0040] The first terminal of the detection unit 1 (serving as the FB pin of the control circuit) is connected to the output feedback signal VFB, and the second terminal (serving as the VDD pin of the control circuit) is connected to the power supply signal VDD. The output terminal is coupled to the timing unit 2. The detection unit 1 is used to monitor the output feedback signal VFB (i.e., the voltage of the FB pin) and the power supply signal VDD (i.e., the voltage of the VDD pin), and generates a detection signal Out based on the output feedback signal VFB and the power supply signal VDD.

[0041] The input terminal of timing unit 2 is coupled to the output terminal of detection unit 1. The timing unit 2 is used to generate a protection control signal PT based on the detection signal Out.

[0042] In one embodiment, such as Figure 3 As shown, the detection unit 1 includes a first comparison module 11, a second comparison module 12, and a logic operation module 13, wherein:

[0043] The first terminal of the first comparison module 11 (i.e., the FB pin of the control circuit) is connected to the output feedback signal VFB, the second terminal is connected to the first threshold signal Vth1, and the output terminal is coupled to the logic operation module 13. The first comparison module 11 is used to generate a first comparison signal Out1 based on the output feedback signal FB and the first threshold signal Vth1.

[0044] The first terminal of the second comparison module 12 (i.e., the VDD pin of the control circuit) is connected to the power supply signal VDD, the second terminal is connected to the second threshold signal Vth2, and the output terminal is coupled to the logic operation module 13. The second comparison module 12 is used to generate a second comparison signal Out2 based on the power supply signal VDD and the second threshold signal Vth2.

[0045] The first end of the logic operation module 13 is coupled to the output end of the first comparison module 11, the second end is coupled to the output end of the second comparison module 12, and the output end is coupled to the timing unit 2, for generating a detection signal Out based on the first comparison signal Out1 and the second comparison signal Out2.

[0046] In one specific implementation, such as Figure 3 As shown, the first comparison module 11 includes a first voltage source and a first comparator U1, wherein:

[0047] The high-potential terminal of the first voltage source is coupled to the first comparator U1, and the low-potential terminal is grounded. The first voltage source is used to provide the first threshold signal Vth1 to the first comparator U1.

[0048] The non-inverting input of the first comparator U1 is coupled to the first voltage source, the inverting input (i.e., the FB pin of the control circuit) is connected to the output feedback signal VFB, and the output is coupled to the logic operation module 13. The first comparator U1 is used to compare the output feedback signal VFB and the first threshold signal Vth1 and generate a first comparison signal Out1. When the output feedback signal VFB < the first threshold signal Vth1, Out1 is high; when the output feedback signal VFB ≥ the first threshold signal Vth1, Out1 is low.

[0049] In another specific implementation, such as Figure 3 As shown, the second comparison module 12 includes a second voltage source and a second comparator U2, wherein:

[0050] The high-potential terminal of the second voltage source is coupled to the second comparator U2, and the low-potential terminal is grounded. The second voltage source is used to provide the second threshold signal Vth2 to the second comparator U2.

[0051] The non-inverting input (i.e., the VDD pin of the control circuit) of the second comparator U2 is connected to the power supply signal VDD, the inverting input is coupled to the second voltage source, and the output is coupled to the logic operation module 13. The second comparator U2 compares the power supply signal VDD with the second threshold signal Vth2 and generates a second comparison signal Out2. When the power supply signal VDD > the second threshold signal Vth2, Out2 is high; when the power supply signal VDD ≤ the second threshold signal Vth2, Out2 is low.

[0052] In another specific embodiment, the logic operation module 13 includes an AND gate, wherein:

[0053] The first input of the AND gate is coupled to the output of the first comparison module 11, the second input is coupled to the output of the second comparison module 12, and the output is coupled to the timing unit 2. The AND gate performs a logical AND operation on the first comparison signal Out1 and the second comparison signal Out2 to generate a detection signal Out. When the output feedback signal VFB < the first threshold signal Vth1 and the power supply signal VDD > the second threshold signal Vth2 (i.e., the FB pin may be open), the detection signal Out is high (at this time, the detection signal Out is the first state signal). When the output feedback signal VFB ≥ the first threshold signal Vth1 or the power supply signal VDD ≤ the second threshold signal Vth2 (i.e., normal or VDD undervoltage), the detection signal Out is low (at this time, the detection signal Out is the second state signal).

[0054] In another embodiment, the timing unit 2 includes a timer module, wherein:

[0055] The input of the timer module is coupled to the output of the detection unit 1. The timer module is used to calculate the duration of the detection signal Out as the first state signal, and outputs a protection control signal PT when the duration of the detection signal Out as the first state signal reaches a target time value. Preferably, the protection control signal PT is a latching signal or a self-resetting signal. The latching signal requires power-off reset to release the protection, while the self-resetting signal automatically resumes normal operation after the abnormality disappears (i.e., the detection signal Out changes to the second state signal).

[0056] A non-isolated flyback circuit, such as Figure 4 As shown, the system includes a transformer, a half-wave rectifier and filter circuit, a voltage divider circuit, a switching transistor, and the aforementioned control circuit. One end of the half-wave rectifier and filter circuit is coupled to the positive output terminal of the non-isolated flyback circuit, and the other end is coupled to the control circuit. The first end of the switching transistor is coupled to the primary winding of the transformer. In the control circuit, the first end of detection unit 1 is coupled to the voltage divider circuit, the second end of detection unit 2 is coupled to the half-wave rectifier and filter circuit, and the output terminal of timing unit 2 (serving as the gate pin of the control circuit) is coupled to the control terminal of the switching transistor. Preferably, the switching transistor is a power MOSFET, with its drain coupled to the primary winding of the transformer and its gate coupled to the output terminal of timing unit 2 of the control circuit. The power MOSFET is turned on or off based on the protection control signal PT output by the control circuit.

[0057] In one embodiment, the voltage divider circuit includes resistors R1 and R2 connected in series, wherein: the first end of resistor R1 is coupled to the positive output terminal of the non-isolated flyback circuit, the second end of resistor R1 is coupled to the first end of resistor R2, the second end of resistor R2 is grounded, and the first end of the detection unit 1 of the control circuit (i.e., the FB pin of the control circuit) is coupled to the connection point of resistors R1 and R2.

[0058] In another embodiment, the half-wave rectifier filter circuit includes a diode and a capacitor, wherein: the anode of the diode is coupled to the positive output terminal of the non-isolated flyback circuit, the cathode is coupled to the first terminal of the capacitor, the second terminal of the capacitor is grounded, and the second terminal of the detection unit 1 of the control circuit (i.e., the VDD pin of the control circuit) is coupled to the cathode of the diode.

[0059] At this time, the protection trigger condition is: when the FB pin voltage VFB < the first threshold signal Vth1 and the VDD pin voltage VDD > the second threshold signal Vth2, and after a preset target time value is reached, the control circuit outputs the protection control signal PT to control the switching transistor to turn off.

[0060] A control circuit is provided for implementing open-circuit and short-circuit protection for a feedback pin in a non-isolated flyback circuit. The control circuit includes a detection unit 1, a timing unit 2, and a switching transistor, wherein the switching transistor is integrated within the control circuit.

[0061] The first terminal of the detection unit 1 (serving as the FB pin of the control circuit) is connected to the output feedback signal VFB, and the second terminal (serving as the VDD pin of the control circuit) is connected to the power supply signal VDD. The output terminal is coupled to the timing unit 2. The detection unit 1 is used to monitor the output feedback signal VFB (i.e., the voltage of the FB pin) and the power supply signal VDD (i.e., the voltage of the VDD pin), and generates a detection signal Out based on the output feedback signal VFB and the power supply signal VDD.

[0062] The input terminal of timing unit 2 is coupled to the output terminal of detection unit 1, and the output terminal is coupled to a switching transistor. Timing unit 2 is used to generate a protection control signal PT based on the detection signal Out.

[0063] A switching transistor, with its control terminal coupled to the output terminal of the timing unit 2, is used to turn the device on or off based on the protection control signal PT output by the timing unit 2. Preferably, the switching transistor is a power MOSFET, and the gate of the power MOSFET is coupled to the output terminal of the timing unit 2.

[0064] A non-isolated flyback circuit, such as Figure 5As shown, the system includes a transformer, a half-wave rectifier and filter circuit, a voltage divider circuit, and the aforementioned control circuit. One end of the half-wave rectifier and filter circuit is coupled to the positive output terminal of the non-isolated flyback circuit, and the other end is coupled to the control circuit. The first end of the detection unit 1 in the control circuit is coupled to the voltage divider circuit, the second end of the detection unit 1 is coupled to the half-wave rectifier and filter circuit, and the first end of the switching transistor (serving as the drain pin of the control circuit) is coupled to the primary winding of the transformer. Preferably, the switching transistor is a power MOSFET, and the drain of the power MOSFET is coupled to the primary winding of the transformer.

[0065] In one embodiment, the voltage divider circuit includes resistors R1 and R2 connected in series, wherein: the first end of resistor R1 is coupled to the positive output terminal of the non-isolated flyback circuit, the second end of resistor R1 is coupled to the first end of resistor R2, the second end of resistor R2 is grounded, and the first end of the detection unit 1 of the control circuit (i.e., the FB pin of the control circuit) is coupled to the connection point of resistors R1 and R2.

[0066] In another embodiment, the half-wave rectifier filter circuit includes a diode and a capacitor, wherein: the anode of the diode is coupled to the positive output terminal of the non-isolated flyback circuit, the cathode is coupled to the first terminal of the capacitor, the second terminal of the capacitor is grounded, and the second terminal of the detection unit 1 of the control circuit (i.e., the VDD pin of the control circuit) is coupled to the cathode of the diode.

[0067] At this time, the protection trigger condition is: when the FB pin voltage VFB < the first threshold signal Vth1 and the VDD pin voltage VDD > the second threshold signal Vth2, and after a preset target time value is reached, the control circuit turns off the internal switching transistor.

[0068] The control methods corresponding to the above control circuit include:

[0069] S1, detect the output feedback signal VFB and the power supply signal VDD;

[0070] S2. Compare the output feedback signal VFB with the first threshold signal Vth1 to generate a first comparison signal Out1; compare the power supply signal VDD with the second threshold signal Vth2 to generate a second comparison signal Out2; perform a logical AND operation on the first comparison signal Out1 and the second comparison signal Out2 to generate a detection signal Out;

[0071] S3. Calculate the duration of the detection signal Out, and generate a protection control signal PT when the duration reaches the target time value;

[0072] S4. Based on the protection control signal PT, control the switch tube to turn on or off.

[0073] In one embodiment, the detection signal Out includes a first state signal and a second state signal, wherein the first state signal indicates that the output feedback signal VFB < the first threshold signal Vth1 and the power supply signal VDD > the second threshold signal Vth2, and the second state signal indicates that the output feedback signal VFB ≥ the first threshold signal Vth1 or the power supply signal VDD ≤ the second threshold signal Vth2.

[0074] In one specific implementation, when the duration of the first state signal reaches the target time value, the control switch is turned off.

[0075] In another embodiment, the protection control signal PT is a latching signal or a self-resetting signal. The latching signal requires power-off reset to release the protection, while the self-resetting signal automatically resumes normal operation after the abnormality disappears (i.e., the detection signal Out changes to the second state signal).

[0076] Those skilled in the art should know that the logic controls such as "high level" and "low level", "set" and "reset", "AND gate" and "OR gate", "non-inverting input" and "inverting input" in the logic control involved in the specification or drawings can be interchanged or changed, and the same function or purpose as the above embodiment can be achieved by adjusting the subsequent logic control.

[0077] The description and application of this utility model herein are illustrative and not intended to limit the scope of the utility model to the above embodiments. The effects or advantages described in the specification may not be apparent in actual experimental examples due to uncertainties in specific conditions or parameters or other factors, and such descriptions are not intended to limit the scope of the utility model. Variations and modifications to the embodiments disclosed herein are possible, and various substitutions and equivalent components of the embodiments are well known to those skilled in the art. It should be clear to those skilled in the art that this utility model can be implemented in other forms, structures, arrangements, proportions, and with other components, materials, and parts without departing from the spirit or essential characteristics of the utility model. Other variations and modifications can be made to the embodiments disclosed herein without departing from the scope and spirit of the utility model.

Claims

1. A control circuit, characterized in that, include: The detection unit has an output feedback signal connected to its first end and a power supply signal connected to its second end. The output end is coupled to a timing unit and is used to generate a detection signal based on the output feedback signal and the power supply signal. The timing unit, whose input is coupled to the output of the detection unit, is used to generate a protection control signal based on the detection signal.

2. The control circuit according to claim 1, characterized in that, The detection unit includes: The first comparison module has an output feedback signal connected to its first end and a first threshold signal connected to its second end. Its output end is coupled to a logic operation module and is used to generate a first comparison signal based on the output feedback signal and the first threshold signal. The second comparison module has a power supply signal connected to its first end, a second threshold signal connected to its second end, and an output terminal coupled to a logic operation module. It is used to generate a second comparison signal based on the power supply signal and the second threshold signal. The logic operation module has a first end coupled to the output of the first comparison module, a second end coupled to the output of the second comparison module, and an output end coupled to a timing unit, for generating a detection signal based on the first comparison signal and the second comparison signal.

3. The control circuit according to claim 2, characterized in that, The first comparison module includes: A first voltage source, with its high-potential end coupled to a first comparator and its low-potential end grounded, is used to generate a first threshold signal. The first comparator has its non-inverting input coupled to the first voltage source, its inverting input connected to the output feedback signal, and its output input coupled to the logic operation module. It is used to compare the output feedback signal and the first threshold signal and generate a first comparison signal.

4. The control circuit according to claim 2, characterized in that, The second comparison module includes: The second voltage source, with its high-potential end coupled to the second comparator and its low-potential end grounded, is used to generate the second threshold signal. The second comparator has a non-inverting input connected to the power supply signal, an inverting input coupled to the second voltage source, and an output coupled to the logic operation module. It is used to compare the power supply signal and the second threshold signal and generate a second comparison signal.

5. The control circuit according to claim 2, characterized in that, The logic operation module includes: The AND gate has its first input terminal coupled to the output terminal of the first comparison module, its second input terminal coupled to the output terminal of the second comparison module, and its output terminal coupled to the timing unit. It is used to perform a logical AND operation on the first comparison signal and the second comparison signal to generate a detection signal.

6. The control circuit according to claim 1 or 2, characterized in that, The detection signal includes a first state signal and a second state signal, wherein the first state signal indicates that the output feedback signal is less than the first threshold signal and the power supply signal is greater than the second threshold signal, and the second state signal indicates that the output feedback signal is greater than or equal to the first threshold signal or the power supply signal is less than or equal to the second threshold signal.

7. The control circuit according to claim 1, characterized in that, The timing unit includes: The timer module, with its input coupled to the output of the detection unit, is used to calculate the duration of the detection signal and output a protection control signal when the duration reaches a target time value.

8. The control circuit according to claim 1 or 7, characterized in that, The protection control signal is a latching signal or a self-recovering signal.

9. The control circuit according to claim 1, characterized in that, The control circuit also includes: The switching transistor, with its control terminal coupled to the output terminal of the timing unit, is used to turn on or off based on a protection control signal.

10. A non-isolated flyback circuit, characterized in that, The device includes a transformer, a half-wave rectifier filter circuit, a voltage divider circuit, a switching transistor, and a control circuit as described in any one of claims 1-8, wherein one end of the half-wave rectifier filter circuit is coupled to the positive output terminal of the non-isolated flyback circuit, and the other end of the half-wave rectifier filter circuit is coupled to the control circuit; the first end of the switching transistor is coupled to the primary winding of the transformer; the first end of the detection unit in the control circuit is coupled to the voltage divider circuit, the second end of the detection unit is coupled to the half-wave rectifier filter circuit, and the output terminal of the timing unit is coupled to the control terminal of the switching transistor.

11. A non-isolated flyback circuit, characterized in that, The system includes a transformer, a half-wave rectifier filter circuit, a voltage divider circuit, and a control circuit as described in claim 9, wherein one end of the half-wave rectifier filter circuit is coupled to the positive output terminal of the non-isolated flyback circuit, and the other end of the half-wave rectifier filter circuit is coupled to the control circuit; the first end of the detection unit in the control circuit is coupled to the voltage divider circuit, the second end of the detection unit is coupled to the half-wave rectifier filter circuit, and the first end of the switching transistor is coupled to the primary winding of the transformer.

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