Switching power supply circuit and automatic reclosure applied by same

Abstract

The embodiment of the utility model provides a switching power supply circuit and an automatic reclosing lock applied by the switching power supply circuit. The switching power supply circuit comprises an input circuit and a control circuit, the output circuit comprises a direct current output end, a first diode and a first grounding end; the first input end of the rectifier bridge is coupled to the live wire end; the second input end is coupled to the zero line end; the power factor adjusting unit is coupled between the zero line end and the second input end and comprises an input resistor and a transient suppression diode which are connected in parallel; the transformer comprises a primary winding and a secondary winding; the primary winding comprises a first end coupled with the rectification output end and a second end; the secondary winding comprises a third end coupled to the anode of the first diode and a fourth end; the second end and the third end are dotted ends; the third input end of the power supply control unit is coupled to the second end, the power supply end is coupled to the DC output end, and the feedback end samples a DC output end signal to control on-off of the power supply end and the third grounding end. Power factor adjustment can be realized, and low power consumption is realized.

Description

Technical Field

[0001] The present disclosure relates to the technical field of power supply, and in particular to a switching power supply circuit and an automatic reclosing switch applied thereto. Background Art

[0002] With the increasing development of smart grid and automatic control technology, fee-controlled smart energy meters have become widely popular. Currently, a large number of fee-controlled smart energy meters used in the market use external circuit breakers (also known as automatic reclosing) to control power on and off.

[0003] However, the automatic reclosing switch has an integrated power supply circuit, which is also powered by the mains electricity. Therefore, the power consumption of the automatic reclosing switch will also be included in the electricity meter. How to reduce its power consumption as much as possible to avoid affecting the normal billing of the electricity meter has become a technical problem that needs to be solved urgently in the industry. Summary of the invention

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a switching power supply circuit and an automatic reclosing circuit to solve the problems in the related art.

[0005] The present disclosure provides a switching power supply circuit in a first aspect, comprising: an input circuit, comprising: a live wire terminal and a neutral wire terminal; an output circuit, comprising: a DC output terminal, a first ground terminal, a first diode and a first energy storage filter capacitor; one end of the first diode is coupled to the DC output terminal; the first energy storage filter capacitor is coupled between the DC output terminal and the first ground terminal; a rectifier bridge, comprising a first input terminal, a second input terminal, a rectifier output terminal and a second ground terminal; the first input terminal is coupled to the live wire terminal; the second input terminal is coupled to the neutral wire terminal; a power factor adjustment unit, coupled between the neutral wire terminal and the second input terminal, comprising: an input resistor and a transient suppression diode connected in parallel; a diode; a transformer, comprising: a primary winding and a secondary winding; the primary winding comprising a first end coupled to the rectifier output end, and a second end; the secondary winding comprising a third end coupled to the other end of the first diode, and a fourth end; wherein the second end and the third end are terminals of the same name; a power control unit, comprising: a third input end, a power supply end, a feedback end and a third ground end; the third input end is coupled to the second end; the power supply end is coupled to the DC output end via a voltage conversion unit; the feedback end is coupled to the DC output end via a voltage sampling unit; the power control unit is configured to control the on and off of the third input end and the third ground end according to a signal from the feedback end.

[0006] In an embodiment of the first aspect, the switching power supply circuit further includes: a peak absorption unit, including a second resistor, a third capacitor and a second diode; the second resistor and the second capacitor are connected in parallel, and one end of the parallel connection is coupled to the first end of the primary winding, and the other end of the parallel connection is coupled to the cathode of the second diode, and the anode of the second diode is coupled to the second end of the primary winding.

[0007] In an embodiment of the first aspect, a fourth resistor is coupled between the other end of the second resistor and the second capacitor connected in parallel and the cathode of the second diode.

[0008] In an embodiment of the first aspect, the output circuit also includes: a third resistor, connected in parallel between the DC output end and the first ground end; and / or, the anode of the first diode is coupled to one end of the first resistor, the other end of the first resistor is coupled to one end of the first capacitor, and the cathode of the first diode is coupled to the other end of the first capacitor.

[0009] In an embodiment of the first aspect, the switching power supply circuit, the voltage conversion unit includes: a third diode, a sixth resistor and a second energy storage filter capacitor; the positive electrode of the third diode is coupled to the DC output end, the negative electrode of the third diode is coupled to one end of the sixth resistor, the other end of the sixth resistor is coupled to the power supply end and one end of the second energy storage filter capacitor, and the other end of the second energy storage filter capacitor is grounded.

[0010] In an embodiment of the first aspect, the second end and the third end are like-named ends, the third end is coupled to the anode of the first diode and the cathode of the first diode is coupled to the DC output end; or, the first end and the third end are like-named ends, the third end is coupled to the cathode of the first diode and the anode of the first diode is coupled to the DC output end, and the output circuit further includes: a fourth diode, whose anode is coupled to the DC output end and whose cathode is coupled to the second ground end.

[0011] In an embodiment of the first aspect, the power control unit includes a MOS tube, a drain of the MOS tube is coupled to the third input terminal, a source is coupled to the third ground terminal, and a gate is coupled to be controlled by the feedback terminal.

[0012] In an embodiment of the first aspect, the switching power supply circuit further includes: at least one energy storage filter capacitor connected in parallel between the ground terminal and the output terminal of the rectifier bridge.

[0013] In an embodiment of the first aspect, the switching power supply circuit, the input circuit also includes: a varistor coupled between the live wire terminal and the neutral wire terminal; and / or a winding resistor coupled between the live wire terminal and the rectifier bridge.

[0014] A second aspect of the present disclosure provides an automatic reclosing device, comprising: a switching power supply circuit as described in any one of the first aspects.

[0015] As described above, the present disclosure provides a switching power supply circuit and an automatic reclosing switch for its application, wherein the switching power supply circuit includes: an input circuit including a live wire and a neutral wire; an output circuit including a DC output terminal, a first diode and a first ground terminal; a rectifier bridge, wherein the first input terminal is coupled to the live wire terminal; the second input terminal is coupled to the neutral wire terminal; a power factor adjustment unit is coupled between the neutral wire terminal and the second input terminal, and includes: a parallel input resistor and a transient suppression diode; a transformer, including: a primary winding and a secondary winding; the primary winding includes a first terminal and a second terminal coupled to the rectifier output terminal; the secondary winding includes a third terminal and a fourth terminal coupled to the positive electrode of the first diode; the second terminal and the third terminal are terminals of the same name; the third input terminal of the power control unit is coupled to the second terminal, the power supply terminal is coupled to the DC output terminal, and the feedback terminal samples the DC output terminal signal to control the on / off of the power supply terminal and the third ground terminal. Power factor adjustment can be achieved, and low power consumption can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 A schematic diagram showing the structure of a switching power supply circuit in an embodiment of the present disclosure is shown. DETAILED DESCRIPTION

[0017] The following is an explanation of the embodiments of the present disclosure by specific examples, and those skilled in the art can easily understand other advantages and effects of the present disclosure from the information disclosed by the present disclosure. The present disclosure can also be implemented or applied through other different specific embodiments, and the details in the present disclosure can also be modified or changed in various ways according to different viewpoints and application modules without departing from the spirit of the present disclosure. It should be noted that the embodiments in the present disclosure and the features in the embodiments can be combined with each other without conflict.

[0018] The following is a detailed description of the embodiments of the present disclosure with reference to the accompanying drawings so that those skilled in the art can easily implement the present disclosure. The present disclosure can be embodied in many different forms and is not limited to the embodiments described herein.

[0019] In the representations of the present disclosure, the reference terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" and the like mean that the specific features, structures, materials or characteristics represented in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. Moreover, the specific features, structures, materials or characteristics represented may be combined in any one or a group of embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine different embodiments or examples represented in the present disclosure and the features of different embodiments or examples, unless they are mutually contradictory.

[0020] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the representation of the present disclosure, "a group" means two or more, unless otherwise clearly and specifically defined.

[0021] In order to clearly describe the present disclosure, components not related to the description are omitted, and the same reference numerals are given to the same or similar components throughout the specification.

[0022] Throughout the specification, when a device is said to be "connected" to another device, this includes not only the case of "direct connection" but also the case of "indirect connection" by placing other elements therebetween. In addition, when a device is said to "include" a certain component, unless otherwise stated, it does not exclude other components, but means that other components may be included.

[0023] Although the terms first, second, etc. are used to represent various elements in this article in some examples, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For example, the first interface and the second interface, etc. are represented. Moreover, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising" and "including" indicate that there are the described features, steps, operations, elements, modules, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or a group of other features, steps, operations, elements, modules, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Therefore, "A, B or C" or "A, B and / or C" means "any of the following: A; B; C; A and B; A and C; B and C; A, B and C". Only when the combination of elements, functions, steps or operations is inherently mutually exclusive in some way, will there be an exception to this definition.

[0024] The technical terms used herein are only used to refer to specific embodiments and are not intended to limit the present disclosure. The singular form used herein also includes the plural form unless the sentence clearly indicates the contrary meaning. The meaning of "including" used in the specification is to specify specific characteristics, regions, integers, steps, operations, elements and / or components, and does not exclude the existence or addition of other characteristics, regions, integers, steps, operations, elements and / or components.

[0025] Although not defined differently, all terms, including technical and scientific terms used herein, have the same meaning as those generally understood by those skilled in the art to which the present disclosure belongs. Terms defined in commonly used dictionaries are additionally interpreted as having meanings consistent with relevant technical literature and the message of the present disclosure, and shall not be overly interpreted as ideal or very formal meanings unless defined.

[0026] At present, fee-controlled smart meters generally use external circuit breakers (i.e., automatic reclosing switches) to control power on and off. However, the power consumption of the automatic reclosing switch will be included in the meter, affecting the normal billing of the meter and resulting in additional electricity costs for users.

[0027] In view of this, a switching power supply circuit is provided in an embodiment of the present disclosure, which can achieve power factor adjustment through a simple circuit, thereby reducing power consumption to solve the problems in the related art.

[0028] like Figure 1 As shown, a circuit structure schematic diagram of a switching power supply circuit in an embodiment of the present disclosure is shown.

[0029] The switching power supply circuit comprises: an input circuit, a rectifier bridge (B1), an output circuit, a power factor adjustment unit, a transformer (T1) and a power control unit (U1).

[0030] The input circuit includes a live terminal (L) and a neutral terminal (N), wherein the live terminal is used to connect to the live wire of the alternating current, and the neutral terminal is used to connect to the neutral wire of the alternating current. As an example, the voltage of the alternating current can be between 85V and 265V.

[0031] The output circuit includes a DC output terminal, a first ground terminal, a first diode (D1) and a first energy storage filter capacitor (CE1). The DC output terminal and the first ground terminal are used to connect a load and output a DC voltage output obtained by converting the AC voltage, wherein the DC voltage is, for example, 12V. The first energy storage filter capacitor is coupled between the DC output terminal and the first ground terminal, and releases electrical energy to form the 12V DC voltage output.

[0032] The rectifier bridge is coupled to the input circuit. Specifically, the rectifier bridge includes a first input terminal, a second input terminal, a rectifier output terminal and a second ground terminal. The first input terminal is coupled to the live wire terminal, and the second input terminal is coupled to the neutral wire terminal. As an example, the rectifier bridge is formed by connecting 4 diodes, which are defined as a first rectifier diode, a second rectifier diode, a third rectifier diode and a fourth rectifier diode. The cathodes of the first rectifier diode and the second rectifier diode are connected and lead to the rectifier output terminal, the anode of the first rectifier diode and the cathode of the third rectifier diode are connected to lead to the first input terminal, the anode of the second rectifier diode and the cathode of the fourth rectifier diode are connected to lead to the second input terminal, and the anodes of the third rectifier diode and the fourth rectifier diode are connected to lead to the second ground terminal.

[0033] As an example, at least one energy storage capacitor may be coupled between the second ground terminal and the rectifier output terminal. Figure 1 The third energy storage capacitor (EC1) and the fourth energy storage capacitor (EC2) are shown in parallel. The specifications of EC1 and EC2 can be the same and are used to store and filter electric energy.

[0034] It should be noted that CE1, CE2, EC1, and EC2 can also play a filtering role. As an example, CE1, CE2, EC1, and EC2 can be polarized capacitors with the negative poles grounded.

[0035] The power factor adjustment unit is coupled between the neutral terminal and the second input terminal, and includes a parallel input resistor (R9) and a transient suppression diode (VR1). It can be understood that the power factor is the cosine value of the difference between the phase angles of the current and the voltage. Through the cooperation of R9 and VR1, the peak value of the input current passing through R9 can be limited to achieve peak correction, that is, the peak value of the input current flowing through R9 is made flat, thereby reducing the signal phase difference between the input voltage and the input current to approach 0 degrees, and the power factor (i.e., the cosine value) can be made close to 1. The power factor refers to the ratio of the active power of the AC circuit to the apparent power. The higher the power factor, the higher the active power output ratio, which can effectively reduce power consumption.

[0036] Optionally, the input circuit further comprises a varistor (RV1) coupled between the live wire terminal and the neutral wire terminal. The varistor forms a current loop between the live wire terminal and the neutral wire terminal. When an overvoltage or surge current is generated in the circuit, the current will preferentially pass through the parallel varistor to achieve a protective effect.

[0037] Optionally, a winding resistor (FR1) may be provided between the live wire end and the rectifier bridge. On the one hand, when the input current is too large, the winding resistor generates more heat and will automatically melt and cut off the circuit, thus playing a role in overcurrent protection; on the other hand, it may also play a role in lightning strike and surge protection.

[0038] The transformer includes a primary winding and a secondary winding. The primary winding includes a first end coupled to the rectifier output end, and a second end. The secondary winding includes a third end coupled to the other end of the first diode, and a fourth end. The second end and the third end are the same-named ends, i.e., the positive ends of each side. One end of the first diode is coupled to the DC output end, and the positive electrode of the first diode is coupled to the third end of the DC output end.

[0039] The power control unit includes a third input terminal, a power supply terminal, a feedback terminal and a third ground terminal. The third input terminal is coupled to the second terminal. The power supply terminal is coupled to the DC output terminal via a voltage conversion unit. The feedback terminal is coupled to the DC output terminal via a voltage sampling unit. The power control unit is configured to control the on / off of the third input terminal (SW) and the third ground terminal according to a signal at the feedback terminal.

[0040] As an example, when the third input terminal and the third ground terminal are turned on, the path from SW to GND of the input circuit is turned on, and the current flows from the first terminal to the second terminal of the primary winding, completing the energy storage of the primary winding, and also the energy storage of the input measured capacitor (such as EC1, EC2, etc.). According to the principle that the potentials at both ends of the transformer with the same polarity are maintained, the current direction of the secondary winding is reversely cut off by D1 at this time, so there is no current on the secondary winding. However, if there is stored energy in CE1 in the previous cycle, it will be discharged at this time to maintain the +12V DC output of the DC output terminal.

[0041] When the third input terminal and the third ground terminal are connected, the path from the second end of the primary winding to the ground is disconnected and no energy is stored. Current flows through the secondary winding, passing through D1 in the forward direction to store energy in the output capacitor and to supply power to the load connected to the DC output terminal and the second ground terminal.

[0042] The load consumes the energy of the secondary winding and the first energy storage capacitor. When the output voltage drops, the feedback terminal samples this situation and triggers the power control unit to increase the on-off frequency of the third input terminal and the third ground terminal to maintain the output voltage stable at +12V; or, when the output voltage rises, the feedback terminal samples this situation and triggers the power control unit to reduce the on-off frequency of the third input terminal and the third ground terminal to maintain +12V stable.

[0043] In some embodiments, the power control unit has a built-in MOS tube, the drain (D) of the MOS tube is coupled to the third input terminal, the source (S) is coupled to the third ground terminal, and the gate (G) is coupled to be controlled by the feedback terminal to control the on-off frequency of the third input terminal and the third ground terminal to stabilize the output voltage of the DC output terminal.

[0044] In some embodiments, the power control unit can be implemented by a power control chip, such as a chip of model PN636X and a related series with similar functions, or a power control chip of other manufacturers with similar principles. Exemplarily, the power control unit may include multiple SW pins, which can be connected and coupled to the second end of the transformer to increase the current carrying capacity. Exemplarily, there is also a built-in current limiting point detection inside the power control unit, which detects the current flowing through the MOS tube. When this current exceeds the built-in current limiting point, an overcurrent protection action can be executed to shut down the MOS tube. Because the larger the load on the output side, the greater the current flowing through the MOS in the primary winding.

[0045] Optionally, the switching power supply circuit further includes a peak absorption unit. The peak absorption unit includes a second resistor (R2), a third capacitor (C3) and a second diode (D2), forming an RCD clamping circuit to absorb spike pulses. Specifically, the second resistor is connected in parallel with the second capacitor, and one end of the parallel connection is coupled to the first end of the primary winding, and the other end of the parallel connection is coupled to the cathode of the second diode, and the anode of the second diode is coupled to the second end of the primary winding. Further optionally, a fourth resistor (R4) is coupled between the other end of the second resistor and the second capacitor in parallel and the cathode of the second diode to adjust the impedance.

[0046] Optionally, the output circuit further includes a third resistor (R3) connected in parallel between the DC output terminal and the first ground terminal, so that the switching power supply has a certain current control capability, pulls down the increased voltage, and avoids loss of control. At the same time, when the power is off, the residual electric energy in the circuit is released through R3.

[0047] Optionally, the anode of the first diode is coupled to one end of the first resistor (R1), the other end of the first resistor is coupled to one end of the first capacitor (C1), and the cathode of the first diode is coupled to the other end of the first capacitor. R1 and C1 form a resistor-capacitor absorption circuit to absorb the high-voltage pulse voltage generated instantly in the circuit, especially to prevent the reverse high-voltage pulse voltage from breaking through the first diode.

[0048] In some embodiments, the voltage conversion unit is used to convert the output voltage of the DC output terminal into a power supply voltage suitable for U1 (for example, 5V or 3.3V, etc.). The voltage conversion unit includes a third diode (D3), a sixth resistor (R6) and a second energy storage filter capacitor (CE2). The anode of the third diode is coupled to the DC output terminal, the cathode of the third diode is coupled to one end of the sixth resistor, the other end of the sixth resistor is coupled to the power supply terminal and one end of the second energy storage filter capacitor, and the other end of the second energy storage filter capacitor is grounded.

[0049] In some embodiments, the voltage sampling unit can be implemented by a resistor voltage divider circuit, and the voltage dividing point of the resistor voltage divider circuit is coupled to the feedback terminal. Exemplarily, the resistor voltage divider circuit includes a fifth resistor (R5), a seventh resistor (R7) and an eighth resistor (R8), one end of the fifth resistor is coupled to the DC output terminal, the other end of the fifth resistor is coupled to one end of the seventh resistor, the other end of the seventh resistor is coupled to one end of the eighth resistor and coupled to the feedback terminal as a voltage dividing point, and the other end of the eighth resistor is grounded. Optionally, a second capacitor (C2) can be connected in parallel to both ends of the eighth resistor.

[0050] In other embodiments, by changing the winding mode of the transformer and the corresponding circuit structure, a switching power supply with another working mode can also be realized. For example, the first end and the third end can also be the same end, then the polarity of the first diode is the same as Figure 1 The secondary winding is connected with opposite polarity, the third end of the secondary winding is coupled to the cathode of the first diode and the anode of the first diode is coupled to the DC output end, and the output circuit also includes: a fourth diode (not shown), the anode of which is coupled to the DC output end and the cathode of which is coupled to the second ground end.

[0051] A second aspect of the present disclosure provides an automatic reclosing device, comprising: a switching power supply circuit as described in any one of the first aspects.

[0052] As described above, the present disclosure provides a switching power supply circuit and an automatic reclosing switch for its application, wherein the switching power supply circuit includes: an input circuit including a live wire and a neutral wire; an output circuit including a DC output terminal, a first diode and a first ground terminal; a rectifier bridge, wherein the first input terminal is coupled to the live wire terminal; the second input terminal is coupled to the neutral wire terminal; a power factor adjustment unit is coupled between the neutral wire terminal and the second input terminal, and includes: a parallel input resistor and a transient suppression diode; a transformer, including: a primary winding and a secondary winding; the primary winding includes a first terminal and a second terminal coupled to the rectifier output terminal; the secondary winding includes a third terminal and a fourth terminal coupled to the positive electrode of the first diode; the second terminal and the third terminal are terminals of the same name; the third input terminal of the power control unit is coupled to the second terminal, the power supply terminal is coupled to the DC output terminal, and the feedback terminal samples the DC output terminal signal to control the on / off of the power supply terminal and the third ground terminal. Power factor adjustment can be achieved, and low power consumption can be achieved.

[0053] The above embodiments are merely illustrative of the principles and effects of the present disclosure, and are not intended to limit the present disclosure. Anyone familiar with the technology may modify or change the above embodiments without violating the spirit and scope of the present disclosure. Therefore, all equivalent modifications or changes made by those with ordinary knowledge in the technical field without departing from the spirit and technical ideas disclosed in the present disclosure shall still be covered by the protection scope of the present disclosure.

Claims

1. A switching power supply circuit, characterized in that: include: Input circuit, including: live wire terminal and neutral wire terminal; The output circuit comprises: a DC output terminal, a first ground terminal, a first diode and a first energy storage filter capacitor; one end of the first diode is coupled to the DC output terminal; the first energy storage filter capacitor is coupled between the DC output terminal and the first ground terminal; A rectifier bridge, comprising a first input terminal, a second input terminal, a rectifier output terminal and a second ground terminal; the first input terminal is coupled to the live terminal; the second input terminal is coupled to the neutral terminal; A power factor adjustment unit is coupled between the neutral terminal and the second input terminal, and includes: an input resistor and a transient suppression diode connected in parallel; A transformer, comprising: a primary winding and a secondary winding; the primary winding comprises a first end coupled to the rectifier output end, and a second end; the secondary winding comprises a third end coupled to the other end of the first diode, and a fourth end; A power control unit comprises: a third input terminal, a power supply terminal, a feedback terminal and a third ground terminal; the third input terminal is coupled to the second terminal; the power supply terminal is coupled to the DC output terminal via a voltage conversion unit; the feedback terminal is coupled to the DC output terminal via a voltage sampling unit; the power control unit is configured to control the on and off of the third input terminal and the third ground terminal according to a signal from the feedback terminal.

2. The switching power supply circuit according to claim 1, characterized in that: Also includes: The peak absorption unit includes a second resistor, a third capacitor and a second diode; the second resistor and the second capacitor are connected in parallel, and one end of the parallel connection is coupled to the first end of the primary winding, the other end of the parallel connection is coupled to the cathode of the second diode, and the anode of the second diode is coupled to the second end of the primary winding.

3. The switching power supply circuit according to claim 2, characterized in that: A fourth resistor is coupled between the other end of the second resistor and the second capacitor connected in parallel and the cathode of the second diode.

4. The switching power supply circuit according to claim 1, characterized in that: Also includes: a third resistor connected in parallel between the DC output terminal and the first ground terminal; And / or, the anode of the first diode is coupled to one end of the first resistor, the other end of the first resistor is coupled to one end of the first capacitor, and the cathode of the first diode is coupled to the other end of the first capacitor.

5. The switching power supply circuit according to claim 1, characterized in that: The voltage conversion unit includes: a third diode, a sixth resistor and a second energy storage filter capacitor; the positive electrode of the third diode is coupled to the DC output end, the negative electrode of the third diode is coupled to one end of the sixth resistor, the other end of the sixth resistor is coupled to the power supply end and one end of the second energy storage filter capacitor, and the other end of the second energy storage filter capacitor is grounded.

6. The switching power supply circuit according to claim 1, characterized in that: The second end and the third end are ends of the same name, the third end is coupled to the anode of the first diode and the cathode of the first diode is coupled to the DC output end; or the first end and the third end are ends of the same name, the third end is coupled to the cathode of the first diode and the anode of the first diode is coupled to the DC output end, and the output circuit further includes: a fourth diode, the anode of which is coupled to the DC output end and the cathode of which is coupled to the second ground end.

7. The switching power supply circuit according to claim 1, characterized in that: The power control unit comprises a MOS tube, a drain of the MOS tube is coupled to the third input terminal, a source of the MOS tube is coupled to the third ground terminal, and a gate of the MOS tube is coupled to be controlled by the feedback terminal.

8. The switching power supply circuit according to claim 1, characterized in that: Also includes: At least one energy storage filter capacitor is connected in parallel between the ground terminal and the output terminal of the rectifier bridge.

9. The switching power supply circuit according to claim 1, characterized in that: The input circuit further includes: a varistor coupled between the live wire terminal and the neutral wire terminal; and / or a winding resistor coupled between the live wire terminal and the rectifier bridge.

10. An automatic reclosing device, characterized in that: include: A switching power supply circuit as claimed in any one of claims 1 to 9.

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