Switching power supply chip and circuit suitable for converter and intelligent direct current metering and control equipment

Abstract

The invention relates to a switching power supply chip and circuit suitable for a converter and intelligent direct current metering and control equipment. The switching power supply chip comprises a VCC detection pin, a feedback detection pin, a detection circuit, a logic judgment circuit, a power switching circuit and a time delay circuit, the detection circuit comprises a VCC detection circuit connected with the VCC detection pin and a feedback detection circuit connected with the delay circuit, and is used for acquiring VCC and feedback voltage; the logical judgment circuit is connected with the detection circuit, acquires VCC and feedback voltage and determines a working mode; the power switch circuit is connected with the logic judgment circuit, and is used for adjusting pulses and controlling on-off of a switch tube; and the delay circuit is connected with the feedback detection pin. The problems of restarting and shutdown of electronic equipment in a strong magnetic environment are solved, primary side feedback is carried out based on a chip, an optocoupler feedback circuit is not needed, the volume of a transformer is reduced through an added strong magnetic mode, the maximum power of a power supply is reduced, the circuit cost is reduced, the PCB space is saved, and the engineering practicability is high.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a switching power supply chip and circuit suitable for converters, intelligent direct current metering and control equipment. Background Art

[0002] Under the influence of external magnetic fields (such as fixed magnets and electromagnets), the normal operation of electronic equipment such as converters and intelligent DC metering and control equipment will be affected at the least, and the problems of restarting and shutting down of electronic equipment such as converters and intelligent DC metering and control equipment will occur at the worst. For the restart and shutdown of electronic equipment such as converters and intelligent DC metering and control equipment in strong magnetic environments, the main reason is that strong magnetism changes the characteristics of the power transformer, which seriously reduces the load capacity of the power supply and makes the electronic equipment such as converters and intelligent DC metering and control equipment unable to operate normally. At present, the main methods to solve this kind of problem are: ① Replace the magnetic core that is less affected by strong magnetism to improve the load capacity of the transformer in a strong magnetic environment; ② Make the power of the power supply very large so that it can meet the normal operation requirements of electronic equipment such as converters and intelligent DC metering and control equipment in a strong magnetic environment. Although the above measures can improve the restart or shutdown of electronic equipment such as converters and intelligent DC metering and control equipment in a strong magnetic field, it will bring about the problem of increased cost and occupy a larger PCB layout space, which will have a negative impact on the design of circuits of electronic equipment such as converters and intelligent DC metering and control equipment. Summary of the invention

[0003] The purpose of the present invention is to provide a switching power supply chip and circuit suitable for converters, intelligent DC metering and control equipment, which improves the problems of restarting and shutting down of electronic equipment such as converters, intelligent DC metering and control equipment in a strong magnetic environment. Primary side feedback is performed based on the switching power supply chip, and no optocoupler feedback circuit is required, thereby reducing circuit design costs and saving PCB layout space.

[0004] The purpose of the present invention can be achieved through the following technical solutions.

[0005] A switching power supply chip suitable for electronic devices such as converters, intelligent DC metering and control equipment, including a VCC detection pin, a feedback detection pin, a detection circuit, a logic judgment circuit, a power switch circuit and a delay circuit;

[0006] The detection circuit includes a VCC detection circuit electrically connected to the VCC detection pin and a feedback detection circuit electrically connected to the delay circuit to obtain a VCC voltage signal and a feedback voltage signal;

[0007] The logic judgment circuit is electrically connected to the detection circuit to obtain the VCC voltage signal and the feedback voltage signal detected by the detection circuit, and determine the working mode of the switching power supply according to the VCC voltage signal and the feedback voltage signal, wherein the working mode includes a normal mode and a strong magnetic mode;

[0008] The power switch circuit is electrically connected to the logic judgment circuit, and the pulse signal is adjusted according to the working mode determined by the logic judgment circuit to control the on and off of the power switch tube;

[0009] The delay circuit is electrically connected to the feedback detection pin.

[0010] Preferably, the logic of the VCC detection circuit for determining the VCC state of the switching power supply according to the detected VCC voltage signal includes:

[0011] If the VCC voltage signal is higher than the overvoltage threshold VCC_OV, it is determined that VCC is in an overvoltage state; if the VCC voltage signal is lower than the undervoltage threshold VCC_UV, it is determined that VCC is in an undervoltage state.

[0012] Preferably, when it is determined that VCC is in an overvoltage state, the power switch circuit stops working immediately, and when the VCC voltage signal decreases to VCC_OV-VCCOV_HYS, the power switch circuit resumes working, wherein VCCOV_HYS is the VCC hysteresis voltage; when it is determined that VCC is in an undervoltage state, the undervoltage protection is triggered, and the power switch circuit stops working immediately and enters a constant current charging state, waiting for the VCC voltage signal to rise to VCC_ST before entering a soft start mode, wherein VCC_ST is the VCC start threshold voltage.

[0013] Preferably, the feedback voltage signal is collected by the delay circuit;

[0014] The feedback detection circuit determines the output state of the switching power supply according to the detected feedback voltage signal, and the logic is as follows:

[0015] If the feedback voltage signal is higher than the feedback reference value VREF_CV, it is determined that the output voltage of the switching power supply is in an overvoltage state; otherwise, it is determined that the output voltage of the switching power supply is in an undervoltage state.

[0016] Preferably, when it is determined that the switching power supply is over-voltage, the duty cycle of the power switch tube in the power switching circuit is reduced; otherwise, the duty cycle of the power switch tube in the power switching circuit is increased.

[0017] Preferably, it is characterized in that the output end of the delay circuit is connected to the feedback detection circuit;

[0018] The delay time is a fixed value, and the maximum value is less than the minimum on-time of the power switch tube in the power switch circuit.

[0019] Preferably, the logic for determining the working mode of the switching power supply by the logic judgment circuit includes:

[0020] If VCC is in an overvoltage state for N consecutive cycles and the output voltage of the switching power supply is in an undervoltage state, it enters the strong magnetic mode: in the strong magnetic mode, the output voltage is temporarily increased by adjusting the pulse frequency and duty cycle, thereby ensuring that the output voltage due to the VCC overvoltage state is always greater than the required minimum voltage, so that the subsequent circuit can operate normally.

[0021] Preferably, the power switching circuit operates in a quasi-resonant mode.

[0022] A switching power supply circuit suitable for electronic devices such as converters, intelligent DC metering and control equipment, characterized by comprising any of the switching power supply chips described above.

[0023] Preferably, it includes a rectification and filtering unit, an energy conversion unit, and a signal modulation unit;

[0024] The rectifier and filter unit is used to convert AC power into DC voltage to provide power for the entire switching power supply, and is composed of a rectifier bridge and a filter capacitor C1; the energy conversion unit converts the DC voltage into a stable DC output, and is composed of a high-frequency transformer, a rectifier diode D2 and a filter capacitor C3; the signal modulation unit includes a VCC modulation circuit and a feedback modulation circuit, and is used to convert the output of the energy conversion unit into a VCC voltage signal and a feedback voltage signal;

[0025] The VCC modulation circuit is composed of voltage-dividing resistors R2 and R3; the feedback modulation circuit is composed of anti-leakage inductance impact resistor R1, rectifier diode D1, and filter capacitor C2;

[0026] The switching power supply chip includes a ground pin and two switch control pins;

[0027] The connection relationship is as follows: the two AC input terminals of the rectifier bridge are connected to the live wire and the neutral wire respectively, and the two DC output terminals are connected in parallel with the filter capacitor C1; one end of the filter capacitor C1 is grounded, and the other end is connected to the opposite end of the primary main winding of the high-frequency transformer; the primary same-name terminal of the high-frequency transformer is connected to the two switch control pins of the switching power supply chip; the secondary same-name terminal of the high-frequency transformer is connected to the positive electrode of the rectifier diode D2; the negative electrode of the rectifier diode D2 is connected to one end of the filter capacitor C3; the other end of the filter capacitor C3 is connected to the zero potential point and the opposite-name terminal of the secondary of the high-frequency transformer; the primary auxiliary power supply winding of the high-frequency transformer The same-name ends are respectively connected to one end of the anti-leakage inductance impact resistor R1 and the voltage-dividing resistor R2, the other end of the voltage-dividing resistor R2 is respectively connected to the feedback detection pin of the switching power supply chip and one end of the voltage-dividing resistor R3, the other end of the voltage-dividing resistor R3 is respectively connected to the opposite-name end of the primary auxiliary power supply winding of the high-frequency transformer, one end of the filter capacitor C2, the ground pin of the switching power supply chip, and grounded; the other end of the anti-leakage inductance impact resistor R1 is connected to the positive electrode of the rectifier diode D1; the negative electrode of the rectifier diode D1 is respectively connected to the other end of the filter capacitor C2 and the VCC detection pin of the switching power supply chip.

[0028] The beneficial technical effects of the present invention are as follows: while improving the restart and shutdown problems of electronic devices such as converters, intelligent DC metering and control equipment in a strong magnetic environment, primary side feedback is performed based on a switching power supply chip, and no optocoupler feedback circuit is required. Due to the addition of a strong magnetic mode, the size of the transformer is reduced, the maximum power of the power supply is reduced, the circuit design cost is reduced, and the PCB layout space is saved, and the engineering practicality is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 It is the basic circuit diagram of the switching power supply in the present invention.

[0031] Figure 2 is the output voltage V of the switching power supply in the strong magnetic mode in the embodiment of the present invention out Waveform graph.

[0032] Figure 3 4 is a voltage waveform diagram of the switching power supply VCC in the strong magnetic mode in an embodiment of the present invention.

[0033] Figure 4 1 is a voltage waveform diagram of the switching power supply SW in the strong magnetic mode in an embodiment of the present invention.

[0034] Figure 5 1 is a waveform diagram of the feedback voltage of the switching power supply in the strong magnetic mode in an embodiment of the present invention.

[0035] Figure 6 This is a working logic diagram of the internal circuit of the switching power supply chip in the present invention.

[0036] Figure numerals: 1 is a rectifier and filter unit; 2 is an energy conversion unit; 3 is a signal modulation unit; N1 is a switching power supply chip. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0038] Embodiment: The embodiment provides a switching power supply chip and circuit suitable for converters, intelligent DC metering and control devices to improve problems such as restarting and shutting down of electronic devices such as converters, intelligent DC metering and control devices in strong magnetic environments.

[0039] A switching power supply is a high-frequency electric energy conversion device and a type of power supply. Its function is to switch the input DC voltage into a high-frequency pulse voltage signal by controlling the on and off of the power switch tube. At the same time, the high-frequency pulse voltage signal is transformed by a high-frequency transformer or inductor and processed by a filter circuit to finally obtain a stable DC output voltage. The output voltage of the switching power supply can be adjusted and stabilized as needed to meet the power requirements of different devices. In this process, the high-frequency transformer plays an important role in energy storage and conversion, and its characteristics are affected by many factors, among which strong magnetism is particularly serious. When the magnetic core of the high-frequency transformer is interfered by strong magnetism, its own inductance value L will drop sharply. According to the energy formula of the transformer It can be seen that when the inductance value L decreases, the energy stored in the transformer decreases, and the energy coupled to the secondary end of the transformer also decreases at this time, so the secondary output voltage decreases. At this time, if no measures are taken, the normal operation of the back-end circuit of the switching power supply will be affected or directly stop running. In order to solve this technical problem, the present application provides a switching power supply chip N1 suitable for electronic devices such as converters, intelligent DC metering and control equipment, and the chip includes a detection circuit, a logic judgment circuit, a power switch circuit and a delay circuit. The VCC voltage and feedback voltage of the high-frequency transformer are detected by the detection circuit respectively, and then the working condition of the high-frequency transformer is judged. When VCC is in an overvoltage state and the feedback is in an undervoltage state, the logic judgment circuit will judge that the high-frequency transformer is to work in a strong magnetic environment, and the chip will adjust the working mode to the strong magnetic mode accordingly. In the strong magnetic mode, by adjusting the pulse frequency and duty cycle, the output voltage is temporarily increased, thereby ensuring that the output voltage due to the VCC overvoltage state is always greater than the required minimum voltage, so that the back-end circuit can operate normally. In addition, the chip adopts a primary feedback method, and the output voltage is sampled by the voltage of the auxiliary winding to ensure the stability of the output voltage, while reducing the cost increased by the use of a photoelectric coupler.

[0040] In order to enable those skilled in the art to better understand the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0041] Figure 1 The switching power supply circuit diagram provided in the embodiment mainly includes a rectifier filter unit 1, an energy conversion unit 2, a signal modulation unit 3 and a switching power supply chip N1, wherein:

[0042] The rectifier and filter unit 1 includes a rectifier bridge BR1 and a filter capacitor C1, which are used to convert the input AC voltage into a stable DC voltage;

[0043] The energy conversion unit 2 includes a high-frequency transformer T1, a rectifier diode D2 and a filter capacitor C3;

[0044] The signal modulation unit 3 includes voltage-dividing resistors R3 and R2, an anti-leakage inductance impact resistor R1, a rectifier diode D1 and a filter capacitor C2;

[0045] The switching power supply chip N1 adopts primary side feedback control technology and supports working in a strong magnetic environment;

[0046] When the switching power supply is not in a strong magnetic state, the input AC voltage is converted into a DC voltage through the rectifier bridge BR1, and the DC voltage is converted into a stable DC voltage through the filter capacitor C1 and provided to the high-frequency transformer T1 for energy storage and energy conversion; the switching power supply chip N1 charges the filter capacitor C2 through the main winding of the high-frequency transformer T1. When the voltage of the filter capacitor C2 rises to the opening threshold VCC_ST When the switching power supply chip N1 starts to operate, the high-frequency transformer T1 enters a high-frequency conversion state, stores the stable DC voltage in the form of magnetic energy, and outputs the stored magnetic energy in the form of voltage when the power switch tube of the switching power supply chip N1 is turned off.

[0047] Among them, the output of the high-frequency transformer T1 mainly includes two aspects: on the one hand, it is converted into a DC voltage through the rectifier diode D2, and at the same time converted into a stable DC output voltage through the filter capacitor C3; on the other hand, it outputs a feedback voltage through the primary auxiliary power supply winding for collection by the switching power supply chip N1. The output end of the primary auxiliary power supply winding is connected to the voltage dividing resistors R3 and R2. Through the voltage dividing of R3 and R2, the VCC voltage is converted into the working voltage required by the feedback detection pin on the switching power supply chip N1, that is, V REF_CV At the same time, the output voltage of the primary auxiliary power supply winding is converted into a DC voltage through the anti-leakage inductance impact resistor R1 and the rectifier diode D1, and is supplied to the switching power supply chip N1 through the filter capacitor C2 for VCC voltage signal acquisition.

[0048] Furthermore, when the load increases or decreases, the output voltage V out At this time, when the switching power supply chip N1 detects the change in the feedback voltage signal, it will adjust the on-duty cycle of the power switch circuit, increase the energy stored in the high-frequency transformer T1, and then increase or decrease the output voltage V out , so that it maintains a stable value.

[0049] It should be noted that when the switching power supply is running, due to the leakage inductance of the high-frequency transformer T1, the output voltage of the primary auxiliary power supply winding will fluctuate for a period of time. Figure 5 As shown in the figure, the output voltage of the primary auxiliary power supply winding has an overshoot for a period of time, which will interfere with the feedback detection circuit of the switching power supply chip N1, causing it to enter the feedback overvoltage protection mechanism. Therefore, a delay circuit is designed inside the switching power supply chip N1 to act on the feedback detection circuit, delaying the feedback detection circuit by T delay Time, missing the overshoot value of the output voltage of the primary auxiliary power supply winding, and detecting the feedback voltage signal.

[0050] When the switching power supply is running stably, the high-frequency transformer T1 is put into strong magnetic mode by using an electromagnet or a fixed magnet. At this time, the strong magnetic environment reduces the inductance of the high-frequency transformer T1, thereby shortening the stabilization time of the primary auxiliary power supply winding, thereby reducing the voltage detected by the feedback detection circuit. Figure 5As shown in the waveform of stage t1. As mentioned above, when the feedback voltage signal decreases, the switching power supply chip N1 will increase the output voltage V by increasing the power switch frequency and conduction duty cycle. out Increase, such as Figure 4 However, due to the sudden drop in the inductance of the high-frequency transformer T1, the switching power supply chip N1 adjusts the frequency and duty cycle to the maximum, which makes the output voltage V out At the same time, the voltage of filter capacitor C2 increases until it reaches the overvoltage protection value V of the VCC pin of the switching power supply chip N1. CC_OV , at this time the output voltage V out Also rises to the maximum value V out_max At this time, the VCC overvoltage protection mechanism is activated, the switching power chip N1 stops running, and the VCC voltage gradually decreases. Figure 3 shown.

[0051] Furthermore, when the switching power supply chip N1 stops running, the output voltage V out and VCC voltage signals gradually decrease. When the VCC voltage signal drops to V CC_OV –V CCOV_HYS When the switching power supply chip N1 is restarted, the output voltage is lower than the design value due to the strong magnetic field, causing the feedback voltage signal to be lower than V REF_CV Therefore, the switching power supply chip N1 increases the duty cycle and the switching frequency, making the output voltage V out Then, the switching power supply will enter the strong magnetic mode, in which the output voltage V out_min The value is always greater than the minimum value required by the subsequent circuit of the switching power supply to ensure the normal operation of the subsequent circuit.

[0052] The above is a detailed introduction to the switching power supply chip and circuit suitable for converters, intelligent DC metering and control equipment provided by the present application. The various embodiments in the specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same and similar parts between the embodiments can refer to each other. For the circuit disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant parts can refer to the method part description. It should be pointed out that for ordinary technicians in this technical field, without departing from the principles of the present application, several improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the claims of the present application.

[0053] It should also be noted that, in this specification, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprise", "include" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the statement "comprises a ..." does not exclude the presence of other identical elements in the process, method, article or device including the element.

Claims

1. A switching power supply chip suitable for converters, intelligent DC metering and control equipment, characterized in that: It includes a VCC detection pin, a feedback detection pin, a detection circuit, a logic judgment circuit, a power switch circuit and a delay circuit; The detection circuit includes a VCC detection circuit electrically connected to the VCC detection pin and a feedback detection circuit electrically connected to the delay circuit to obtain a VCC voltage signal and a feedback voltage signal; The logic judgment circuit is electrically connected to the detection circuit to obtain the VCC voltage signal and the feedback voltage signal detected by the detection circuit, and determine the working mode of the switching power supply according to the VCC voltage signal and the FB voltage signal, wherein the working mode includes a normal mode and a strong magnetic mode; The power switch circuit is electrically connected to the logic judgment circuit, and the pulse signal is adjusted according to the working mode determined by the logic judgment circuit to control the on and off of the power switch tube; The delay circuit is electrically connected to the feedback detection pin.

2. A switching power supply chip suitable for converters, intelligent DC metering and control equipment according to claim 1, characterized in that: The logic of the VCC detection circuit for determining the VCC state of the switching power supply according to the detected VCC voltage signal includes: If the VCC voltage signal is higher than the overvoltage threshold VCC_OV, it is determined that VCC is in an overvoltage state; if the VCC voltage signal is lower than the undervoltage threshold VCC_UV, it is determined that VCC is in an undervoltage state.

3. A switching power supply chip suitable for converters, intelligent DC metering and control equipment according to claim 2, characterized in that: When it is determined that VCC is in an overvoltage state, the power switch circuit stops working immediately, and when the VCC voltage signal drops to VCC_OV-VCCOV_HYS, the power switch circuit resumes working, where VCCOV_HYS is the VCC hysteresis voltage; when it is determined that VCC is in an undervoltage state, the undervoltage protection is triggered, and the power switch circuit stops working immediately and enters a constant current charging state, waiting for the VCC voltage signal to rise to VCC_ST before entering the soft start mode, where VCC_ST is the VCC start threshold voltage.

4. A switching power supply chip suitable for a converter, intelligent DC metering and control equipment according to claim 1, characterized in that: Collecting the feedback voltage signal through the delay circuit; The feedback detection circuit determines the output state of the switching power supply according to the detected feedback voltage signal, and the logic is as follows: If the feedback voltage signal is higher than the feedback reference value VREF_CV, it is determined that the output voltage of the switching power supply is in an overvoltage state; otherwise, it is determined that the output voltage of the switching power supply is in an undervoltage state.

5. A switching power supply chip suitable for a converter, intelligent DC metering and control equipment according to claim 4, characterized in that: When it is determined that the switching power supply is over-voltage, the duty cycle of the power switch tube in the power switching circuit is reduced; otherwise, the duty cycle of the power switch tube in the power switching circuit is increased.

6. A switching power supply chip delay suitable for converters, intelligent DC metering and control equipment according to claim 1, characterized in that: The output end of the delay circuit is connected to the feedback detection circuit; The delay time is a fixed value, and the maximum value is less than the minimum on-time of the power switch tube in the power switch circuit.

7. The switching power supply chip suitable for converters, intelligent DC metering and control equipment according to claim 1, characterized in that: The logic of the logic judgment circuit determining the working mode of the switching power supply includes: If VCC is in an overvoltage state for N consecutive cycles and the output voltage of the switching power supply is in an undervoltage state, it enters the strong magnetic mode: in the strong magnetic mode, the output voltage is temporarily increased by adjusting the pulse frequency and duty cycle, thereby ensuring that the output voltage due to the VCC overvoltage state is always greater than the required minimum voltage, so that the subsequent circuit can operate normally.

8. The switching power supply chip suitable for converters, intelligent DC metering and control equipment according to claim 1, characterized in that: The power switch circuit operates in a quasi-resonant mode.

9. A switching power supply circuit suitable for converters, intelligent DC metering and control equipment, characterized in that: A switching power supply chip comprising any one of claims 1 to 8.

10. A switching power supply circuit suitable for a converter, an intelligent DC metering and control device according to claim 9, characterized in that: It includes a rectification and filtering unit, an energy conversion unit, and a signal modulation unit; The rectifier and filter unit is used to convert AC power into DC voltage to provide power for the entire switching power supply, and is composed of a rectifier bridge and a filter capacitor C1; the energy conversion unit converts the DC voltage into a stable DC output, and is composed of a high-frequency transformer, a rectifier diode D2 and a filter capacitor C3; the signal modulation unit includes a VCC modulation circuit and a feedback modulation circuit, and is used to convert the output of the energy conversion unit into a VCC voltage signal and a feedback voltage signal; The VCC modulation circuit is composed of voltage-dividing resistors R2 and R3; the feedback modulation circuit is composed of anti-leakage inductance impact resistor R1, rectifier diode D1, and filter capacitor C2; The switching power supply chip includes a ground pin and two switch control pins; The connection relationship is as follows: the two AC input terminals of the rectifier bridge are connected to the live wire and the neutral wire respectively, and the two DC output terminals are connected in parallel with the filter capacitor C1; one end of the filter capacitor C1 is grounded, and the other end is connected to the opposite end of the primary main winding of the high-frequency transformer; the primary same-name terminal of the high-frequency transformer is connected to the two switch control pins of the switching power supply chip; the secondary same-name terminal of the high-frequency transformer is connected to the positive electrode of the rectifier diode D2; the negative electrode of the rectifier diode D2 is connected to one end of the filter capacitor C3; the other end of the filter capacitor C3 is connected to the zero potential point and the opposite-name terminal of the secondary of the high-frequency transformer; the primary auxiliary power supply winding of the high-frequency transformer The same-name ends are respectively connected to one end of the anti-leakage inductance impact resistor R1 and the voltage-dividing resistor R2, the other end of the voltage-dividing resistor R2 is respectively connected to the feedback detection pin of the switching power supply chip and one end of the voltage-dividing resistor R3, the other end of the voltage-dividing resistor R3 is respectively connected to the opposite-name end of the primary auxiliary power supply winding of the high-frequency transformer, one end of the filter capacitor C2, the ground pin of the switching power supply chip, and grounded; the other end of the anti-leakage inductance impact resistor R1 is connected to the positive electrode of the rectifier diode D1; the negative electrode of the rectifier diode D1 is respectively connected to the other end of the filter capacitor C2 and the VCC detection pin of the switching power supply chip.

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