Switching power supply starting circuit, method, switching power supply and electrical equipment

Abstract

The present disclosure discloses a startup circuit, method, switching power supply and electrical equipment of a switching power supply, and relates to the technical field of switching power supplies. The switching power supply includes at least one control circuit, and the startup circuit includes: a normally closed switch; a delay circuit, which is configured to delay the current signal of the control circuit until the switching power supply is started, and transmit it to the normally closed switch; a transformer, including a primary winding and at least one secondary winding, wherein the primary winding is connected to the AC power supply end through the normally closed switch; and at least one rectifier and filter circuit, wherein the at least one rectifier and filter circuit is connected to the at least one secondary winding in a one-to-one correspondence, and is connected to the at least one control circuit in a one-to-one correspondence. The present disclosure can realize the startup of the switching power supply. After the switching power supply is started, the normally closed switch is disconnected, and the signal at the AC power supply end no longer flows through the transformer in the startup circuit, thereby avoiding continuous power loss in the startup circuit.

Description

Technical Field

[0001] The present disclosure relates to the technical field of switching power supplies, and in particular to a starting circuit and method of a switching power supply, a switching power supply and an electrical device. Background Art

[0002] The AC (Alternating Current) -DC (Direct Current) switching power supply structure mainly includes four parts: an input rectification and filtering circuit part mainly composed of a rectifier bridge and an energy storage capacitor, a chopper circuit part mainly composed of a high-frequency transformer and a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), a control circuit part mainly composed of a power chip, and an output circuit rectification and filtering part mainly composed of a unidirectional diode and an energy storage capacitor.

[0003] When the AC-DC switching power supply is working, the AC input is transmitted to the chopper circuit through the input rectifier filter circuit. The signal output by the control circuit controls the MOSFET switch of the chopper circuit to make the chopper circuit work. The output of the chopper circuit is then passed through the output rectifier filter circuit to obtain a stable output voltage. Only when the control circuit works normally, the switching power supply will have an output voltage. The power chip of the control circuit requires a certain voltage to work. When the power supply is working normally, the power chip is generally powered by the auxiliary winding of the high-frequency transformer of the switching power supply. During the startup of the switching power supply, the auxiliary winding cannot provide a stable voltage, and another circuit is required to power the power chip. Summary of the invention

[0004] A technical problem to be solved by the present disclosure is to provide a starting circuit and method of a switching power supply, a switching power supply and an electrical device, so as to avoid continuous power loss in the starting circuit after the switching power supply is started.

[0005] According to one aspect of the present disclosure, a starting circuit of a switching power supply is proposed, wherein the switching power supply includes at least one control circuit, and the starting circuit includes: a normally closed switch; a delay circuit, configured to delay the current signal of at least one control circuit until the switching power supply is started, and then transmit it to the normally closed switch; a transformer, including a primary winding and at least one secondary winding, wherein the primary winding is connected to an AC power supply terminal through a normally closed switch; and at least one rectifier and filter circuit, connected in a one-to-one correspondence with the at least one secondary winding, and connected in a one-to-one correspondence with the at least one control circuit.

[0006] In some embodiments, each rectifier and filter circuit includes: a rectifier, wherein the input end of the rectifier is connected to the corresponding secondary winding and is configured to rectify the AC signal output by the corresponding secondary winding into a DC signal; and a voltage stabilizing filter circuit, wherein the input end of the voltage stabilizing filter circuit is connected to the output end of the rectifier, and the output end of the voltage stabilizing filter circuit is connected to the corresponding control circuit, and is configured to perform voltage stabilizing and filtering processing on the DC signal output by the corresponding rectifier, and input the processed DC signal to the power supply end of the corresponding control circuit.

[0007] In some embodiments, the delay circuit includes an inductor, wherein a first end of the inductor is connected to the normally closed switch; and a second end of the inductor is connected to a power supply terminal of any one of the at least one control circuit.

[0008] In some embodiments, the delay circuit includes an inductor, and at least one control circuit includes multiple control circuits, wherein a first end of the inductor is connected to a normally closed switch; and a second end of the inductor is connected to a power supply end of at least two of the multiple control circuits.

[0009] In some embodiments, the delay circuit includes a resistor and a first capacitor, wherein the first capacitor is connected to a power supply terminal of any one of the at least one control circuits through the resistor and is connected in parallel with the normally closed switch.

[0010] In some embodiments, the delay circuit includes a resistor and a first capacitor, and at least one control circuit includes multiple control circuits, wherein the first capacitor is connected to the power supply terminal of at least two of the multiple control circuits through a resistor and is connected in parallel with a normally closed switch.

[0011] In some embodiments, the normally closed switch includes a normally closed relay, wherein a first end of a coil of the normally closed relay is connected to a delay circuit and a second end is grounded; a first contact of the normally closed relay is connected to a first end of a primary winding and a second contact is configured to be connected to a first end of an AC power supply terminal; and a second end of the primary winding is configured to be connected to a second end of the AC power supply terminal.

[0012] In some embodiments, the voltage stabilizing and filtering circuit includes a second capacitor, wherein a first end of the second capacitor is connected to a first output end of a corresponding rectifier and to a power supply end of a corresponding control circuit; and a second end of the second capacitor is connected to a second output end of the corresponding rectifier and to ground.

[0013] In some embodiments, the turns ratio of the primary winding of the transformer to each of the at least one secondary winding is determined according to the power supply voltage required by the corresponding control circuit.

[0014] In some embodiments, the inductance value of the inductor is determined according to the start-up time of the switching power supply.

[0015] In some embodiments, the capacitance value of the first capacitor is determined according to a startup time of the switching power supply.

[0016] According to another aspect of the present disclosure, a switching power supply is also provided, comprising the above-mentioned starting circuit.

[0017] According to another aspect of the present disclosure, an electrical device is also provided, comprising the above-mentioned switching power supply.

[0018] According to another aspect of the present disclosure, a starting method for a starting circuit of a switching power supply as described above is also proposed, comprising: during the starting process of the switching power supply, the normally closed switch is in a closed state; the transformer converts a first AC signal output from the AC power supply end into at least one second AC signal, and transmits each of the at least one second AC signal to a corresponding rectifier and filter circuit; each of the at least one rectifier and filter circuit rectifies and filters the received second AC signal into a DC signal for supplying power to a corresponding control circuit; and after the switching power supply is started, the normally closed switch is in an open state.

[0019] In the disclosed embodiment, during the startup process of the switching power supply, the normally closed switch is closed, and the signal at the AC power supply end is transformed by the transformer and then input into the rectifier filter circuit for rectification and filtering. The DC signal output by the rectifier filter circuit is input into the control circuit, and after the power chip or the driver chip of the control circuit is powered, the switching power supply is started. After the switching power supply is started, the normally closed switch is disconnected, and the signal at the AC power supply end no longer flows through the transformer in the startup circuit, thereby avoiding continuous power loss in the startup circuit. The circuit structure is simple and the reliability of the switching power supply is enhanced.

[0020] Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The accompanying drawings, which constitute a part of the specification, illustrate embodiments of the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0022] The present disclosure may be more clearly understood from the following detailed description with reference to the accompanying drawings, in which:

[0023] Figure 1 It is a schematic diagram of the structure of some embodiments of the startup circuit of the switching power supply disclosed in the present invention.

[0024] Figure 2 Schematic diagrams of the structures of other embodiments of the startup circuit of the switching power supply disclosed in the present invention.

[0025] Figure 3Schematic diagrams of the structures of other embodiments of the startup circuit of the switching power supply disclosed in the present invention.

[0026] Figure 4 The present invention is a flowchart of some embodiments of the startup method of the switching power supply disclosed in the present invention. DETAILED DESCRIPTION

[0027] Various exemplary embodiments of the present disclosure will now be described in detail with reference to the accompanying drawings. It should be noted that the relative arrangement of components and steps, numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present disclosure unless otherwise specifically stated.

[0028] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0029] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the present disclosure, its application, or uses.

[0030] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0031] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0032] It should be noted that like reference numerals and letters refer to similar items in the following figures, and therefore, once an item is defined in one figure, it need not be further discussed in subsequent figures.

[0033] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0034] In the related art, a series resistor is used to divide the bus voltage to power the power chip of the control circuit during the startup phase of the switching power supply. When the startup process is over and the auxiliary winding of the transformer takes over the power supply of the power chip, the added resistance is still consuming power. In addition, if multiple power chips need to be powered on at the same time during the startup process of the switching power supply, and the operating voltage required for each power chip is different, the power loss will increase if the resistor voltage is divided, so an auxiliary power supply is required to power these power chips.

[0035] Figure 1The schematic diagram of some embodiments of the startup circuit of the switching power supply disclosed in the present invention is as follows. The switching power supply includes at least one control circuit 110 , and the startup circuit includes a normally closed switch 120 , a delay circuit 130 , a transformer 140 and at least one rectifier filter circuit 150 .

[0036] The delay circuit 130 is configured to delay the current signal of at least one control circuit 110 until the switching power supply is started and then transmit the current signal to the normally closed switch 120 .

[0037] In some embodiments, after the switching power supply is started, the normally closed switch 120 is switched from the closed state to the conducting state. The normally closed switch 120 is, for example, a normally closed relay.

[0038] In some embodiments, the delay circuit 130 is, for example, an inductor, or a combination of a resistor and a first capacitor. If the delay circuit 130 is an inductor, the first end of the inductor is connected to the normally closed switch, and the second end of the inductor is connected to the power supply terminal of any one of the at least one control circuit. If the delay circuit 130 is a combination of a resistor and a first capacitor, the first capacitor is connected to the power supply terminal of any one of the at least one control circuit through the resistor, and is connected in parallel with the normally closed switch.

[0039] If there are multiple control circuits 110, after the switching power supply is started, the power chips of the multiple control circuits 110 are powered by the corresponding auxiliary windings of the same high-frequency transformer. Therefore, the delay circuit 130 can be connected to only any one of the multiple control circuits 110, reducing the connection circuit lines.

[0040] In some embodiments, the second end of the inductor is connected to the power supply terminals of at least two control circuits among the plurality of control circuits, or the first capacitor is connected to the power supply terminals of at least two control circuits among the plurality of control circuits through a resistor.

[0041] The transformer 140 includes a primary winding and at least one secondary winding, wherein the primary winding is connected to an AC power source terminal via a normally closed switch 120 .

[0042] At least one rectifying and filtering circuit 150 is connected to at least one secondary winding in a one-to-one correspondence, and is also connected to at least one control circuit 110 in a one-to-one correspondence.

[0043] The number of the control circuit 110, the rectifier filter circuit 150, and the secondary winding is the same, that is, if the switching power supply includes several control circuits 110, the startup circuit includes several rectifier filter circuits 150, and the transformer 140 includes several secondary windings. For example, if the switching power supply includes one control circuit 110, the startup circuit includes one rectifier filter circuit 150, and the transformer 140 includes one secondary winding. The secondary winding, the rectifier filter circuit 150, and the control circuit 110 are electrically connected in sequence.

[0044] In some embodiments, the rectifier and filter circuit 150 includes a rectifier and a voltage stabilizing filter circuit. The input end of the rectifier is connected to the corresponding secondary winding, and is configured to rectify the AC signal output by the corresponding secondary winding into a DC signal. The input end of the voltage stabilizing filter circuit is connected to the output end of the rectifier, and the output end of the voltage stabilizing filter circuit is connected to the corresponding control circuit, and is configured to perform voltage stabilizing filter processing on the DC signal output by the corresponding rectifier, and input the processed DC signal to the power supply end of the corresponding control circuit.

[0045] In the above embodiment, during the startup process of the switching power supply, the normally closed switch is closed, and the signal at the AC power supply end is transformed by the transformer and then input into the rectifier filter circuit for rectification and filtering. The DC signal output by the rectifier filter circuit is input into the control circuit, and after the power chip or the driver chip of the control circuit is powered, the switching power supply is started. After the switching power supply is started, the normally closed switch is disconnected, and the signal at the AC power supply end no longer flows through the transformer in the startup circuit, thereby avoiding continuous power loss in the startup circuit. The circuit structure is simple and the reliability of the switching power supply is enhanced.

[0046] Figure 2 The schematic diagram of the structure of other embodiments of the startup circuit of the switching power supply disclosed in the present invention is shown in FIG. In this embodiment, the switching power supply includes a control circuit, the normally closed switch is taken as an example of a normally closed relay, the delay circuit is taken as an example of an inductor, and the voltage stabilizing filter circuit is introduced as an example of a capacitor.

[0047] The startup circuit includes a normally closed relay J, an inductor L, a transformer T1, a rectifier U1, and a second capacitor C1. The first end of the inductor L is connected to the first end of the coil of the normally closed relay J, and the second end of the inductor L is connected to the power supply end of the control circuit, for example, to the chip power supply pin. The second end of the coil of the normally closed relay J is grounded. The first contact of the normally closed relay J is connected to the first end of the primary winding of the transformer T1, and the second contact is configured to be connected to the first end 1 of the AC power supply end. The second end of the primary winding is configured to be connected to the second end 2 of the AC power supply end.

[0048] In some embodiments, the inductance value of the inductor L is determined according to the startup time of the switching power supply, that is, after ensuring that the switching power supply establishes a stable output voltage, the inductance of the inductor L reaches saturation, so that the normally closed relay J is disconnected. For example, if the startup time of the switching power supply is 100ms, the inductor L should ensure that the delay time is greater than 100ms.

[0049] In some embodiments, if the delay circuit adopts a combination mode of a resistor and a first capacitor, the capacitance value of the first capacitor is determined according to the startup time of the switching power supply, and the delay is achieved by charging the capacitor.

[0050] The two ends of the secondary winding of the transformer T1 are respectively connected to the two input ends of the rectifier U1, the first output end of the rectifier U1 is connected to the first end of the second capacitor C1, the second output end of the rectifier U1 is connected to the second end of the second capacitor C1, the first end of the second capacitor C1 is connected to the power supply end of the control circuit, and the second end of the second capacitor C1 is grounded.

[0051] In some embodiments, the rectifier U1 is, for example, a rectifier bridge, which includes a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4. The anode of the first diode D1 serves as the first input terminal of the rectifier bridge, the cathode of the first diode D1 serves as the first output terminal of the rectifier bridge, the cathode of the second diode D2 serves as the second input terminal of the rectifier bridge, the anode of the second diode D2 serves as the second output terminal of the rectifier bridge, the anode of the third diode D3 is connected to the cathode of the second diode D2, the cathode of the third diode D3 is connected to the cathode of the first diode D1, the cathode of the fourth diode D4 is connected to the anode of the first diode D1, and the anode of the fourth diode D4 is connected to the anode of the second diode D2.

[0052] In this embodiment, before the switching power supply is powered on and during the startup process, the normally closed relay J is in a closed state, that is, the AC input of the power supply flows into the transformer T1 through the normally closed relay J, and the AC signal is stepped down by the primary-secondary turns ratio of the transformer T1. After the current flows out of the transformer T1, it is rectified by the rectifier U1 and filtered by the second capacitor C1 to obtain a voltage suitable for the chip of the control circuit to work. After the switching power supply is started, the normally closed relay J is in an open state, and the power is supplied through the auxiliary winding of the high-frequency transformer of the switching power supply. The voltage output by the auxiliary winding should also be within the voltage range of the chip of the control circuit to work.

[0053] In some embodiments, Figure 2The first end of the auxiliary winding of the high-frequency transformer T2 of the switching power supply is connected to the anode of the fifth diode D5, the cathode of the fifth diode D5 is connected to the power supply end of the control circuit, and the second end of the auxiliary winding of the high-frequency transformer T2 is grounded. The fifth diode D5 plays a one-way cutoff role, that is, when the normally closed relay J is closed, the signal output by the rectifier U1 will not flow into the high-frequency transformer T2. When the normally closed relay is disconnected, the start-up circuit stops working, the fifth diode D5 is turned on, and the control circuit is powered by the auxiliary winding of the high-frequency transformer T2, so as to avoid continuous power loss in the start-up circuit. The circuit has a simple structure, high reliability, and improved work efficiency.

[0054] Figure 3 The schematic diagram of the structure of other embodiments of the startup circuit of the switching power supply disclosed in the present invention is shown in FIG. In this embodiment, two control circuits are taken as examples for introduction.

[0055] The start-up circuit includes a normally closed relay J, an inductor L, a transformer T1, rectifiers U1 and U2, and second capacitors C11 and C12. The first end of the inductor L is connected to the first end of the coil of the normally closed relay J, and the second end of the inductor L is connected to the power supply terminal of any one of the control circuits. The second end of the coil of the normally closed relay J is grounded. The first contact of the normally closed relay J is connected to the first end of the primary winding of the transformer T1, and the second contact is configured to be connected to the first end of the AC power supply terminal. The second end of the primary winding is configured to be connected to the second end of the AC power supply terminal.

[0056] The two ends of the first secondary winding of the transformer T1 are respectively connected to the two input ends of the rectifier U1, the first output end of the rectifier U1 is connected to the first end of the second capacitor C11, the second output end of the rectifier U1 is connected to the second end of the second capacitor C11, the first end of the second capacitor C11 is connected to the power supply end of the first control circuit, and the second end of the second capacitor C11 is grounded.

[0057] The two ends of the second secondary winding of the transformer T1 are respectively connected to the two input ends of the rectifier U2, the first output end of the rectifier U2 is connected to the first end of the second capacitor C12, the second output end of the rectifier U2 is connected to the second end of the second capacitor C12, the first end of the second capacitor C12 is connected to the power supply end of the second control circuit, and the second end of the second capacitor C12 is grounded.

[0058] In some embodiments, the turns ratio of the primary winding of the transformer to each of the at least one secondary winding is determined according to the power supply voltage required by the corresponding control circuit, that is, the voltage output by the transformer T1 can meet the requirements of each chip after rectification and filtering.

[0059] In some embodiments, the high-frequency transformer T2 of the switching power supply includes two auxiliary windings. A first end of the first auxiliary winding is connected to the anode of the fifth diode D5, a cathode of the fifth diode D5 is connected to the power supply terminal of the first control circuit, and a second end of the first auxiliary winding is grounded. A first end of the second auxiliary winding is connected to the anode of the sixth diode D6, a cathode of the sixth diode D6 is connected to the power supply terminal of the second control circuit, and a second end of the second auxiliary winding is grounded.

[0060] When the chips of each control circuit require different power supply levels during the startup of the switching power supply, the number of the secondary winding of the transformer T1 and the auxiliary winding of the high-frequency transformer T2 is increased, and the number of rectifiers and filter capacitors is increased. Before the switching power supply is powered on and during the startup process, the normally closed relay J is in a closed state, that is, the AC input of the power supply flows into the transformer T1 through the normally closed relay J, and the AC signal is stepped down by the primary and secondary turns ratio of the transformer T1. After the current flows out of the transformer T1, it is rectified by the rectifiers U1 and U2, and then filtered by the second capacitors C11 and C12 to obtain a voltage suitable for the chip of the control circuit to work. After the switching power supply is started, the normally closed relay J is disconnected, the startup circuit stops working, the fifth diode D5 and the sixth diode D6 are turned on, and the control circuit is powered by the auxiliary winding of the high-frequency transformer T2. This embodiment can power the chips of multiple control circuits without adding auxiliary power, reducing the circuit cost and volume, and can avoid continuous power loss in the startup circuit.

[0061] In some other embodiments of the present disclosure, a switching power supply is protected, and the switching power supply includes the startup circuit in the above embodiment. The switching power supply is an AC-DC switching power supply.

[0062] In some other embodiments of the present disclosure, an electrical device is protected, and the electrical device includes the switching power supply in the above embodiment.

[0063] Figure 4 The present invention is a flowchart of some embodiments of the startup method of the switching power supply disclosed in the present invention. The switching power supply includes at least one control circuit.

[0064] In step 410, during the startup of the switching power supply, the normally closed switch is in a closed state.

[0065] In step 420, the transformer converts the first AC signal output from the AC power supply end into at least one second AC signal, and transmits each of the at least one second AC signal to a corresponding rectifier and filter circuit.

[0066] In step 430 , each of the at least one rectifying and filtering circuit rectifies and filters the received second AC signal into a DC signal for supplying power to a corresponding control circuit.

[0067] In step 440, after the switching power supply is started, the normally closed switch is in an open state. After the switching power supply is started, the auxiliary winding of the original high-frequency transformer of the switching power supply supplies power to the chip of the control circuit.

[0068] In the above embodiment, during the startup process of the switching power supply, the normally closed switch is closed, the AC signal is transformed by the transformer, and then input into the rectifier filter circuit for rectification and filtering, the DC signal output by the rectifier filter circuit is input into the control circuit, and after the power chip or the driver chip of the control circuit is powered, the switching power supply is started. After the switching power supply is started, the normally closed switch is disconnected, and the signal at the AC power supply end no longer flows through the transformer in the startup circuit, thereby avoiding continuous power loss in the startup circuit.

[0069] So far, the present disclosure has been described in detail. In order to avoid obscuring the concept of the present disclosure, some details known in the art are not described. Based on the above description, those skilled in the art can fully understand how to implement the technical solution disclosed here.

[0070] The method and apparatus of the present disclosure may be implemented in many ways. For example, the method and apparatus of the present disclosure may be implemented by software, hardware, firmware, or any combination of software, hardware, and firmware. The above order of steps for the method is for illustration only, and the steps of the method of the present disclosure are not limited to the order specifically described above, unless otherwise specifically stated. In addition, in some embodiments, the present disclosure may also be implemented as a program recorded in a recording medium, which includes machine-readable instructions for implementing the method according to the present disclosure. Therefore, the present disclosure also covers a recording medium storing a program for executing the method according to the present disclosure.

[0071] Although some specific embodiments of the present disclosure have been described in detail by way of example, it should be understood by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the present disclosure. It should be understood by those skilled in the art that the above embodiments may be modified without departing from the scope and spirit of the present disclosure. The scope of the present disclosure is defined by the appended claims.

Claims

1. A starting circuit for a switching power supply, wherein: The switching power supply includes at least one control circuit, and the startup circuit includes: A normally closed switch, the normally closed switch comprising a normally closed relay, wherein a first end of a coil of the normally closed relay is connected to a time delay circuit, a second end is grounded, a first contact of the normally closed relay is connected to a first end of a primary winding of a transformer, and a second contact is configured to be connected to a first end of an AC power supply terminal; A delay circuit, configured to delay the current signal of the at least one control circuit until the switching power supply is started and then transmit it to the normally closed switch; A transformer, comprising a primary winding and at least one secondary winding, wherein a second end of the primary winding is configured to be connected to a second end of the AC power source; and At least one rectifier and filter circuit is connected one-to-one with the at least one secondary winding and one-to-one with the at least one control circuit. Each of the at least one rectifier and filter circuits includes: a rectifier and a voltage stabilizing filter circuit. The input end of the rectifier is connected to the corresponding secondary winding, the input end of the voltage stabilizing filter circuit is connected to the output end of the rectifier, and the output end of the voltage stabilizing filter circuit is connected to the corresponding control circuit.

2. The startup circuit according to claim 1, wherein: The rectifier is configured to rectify the AC signal output by the corresponding secondary winding into a DC signal; and The voltage stabilizing and filtering circuit is configured to perform voltage stabilizing and filtering processing on the DC signal output by the corresponding rectifier, and input the processed DC signal to the power supply end of the corresponding control circuit.

3. The startup circuit according to claim 1, wherein: The delay circuit includes an inductor, wherein: The first end of the inductor is connected to the normally closed switch; and The second end of the inductor is connected to a power supply end of any one of the at least one control circuit.

4. The startup circuit according to claim 1, wherein: The delay circuit comprises a resistor and a first capacitor, wherein: The first capacitor is connected to a power supply terminal of any one of the at least one control circuits through the resistor, and is connected in parallel with the normally closed switch.

5. The startup circuit according to claim 2, wherein: The voltage stabilizing and filtering circuit includes a second capacitor, wherein: The first end of the second capacitor is connected to the first output end of the corresponding rectifier and to the power supply end of the corresponding control circuit; and The second end of the second capacitor is connected to the second output end of the corresponding rectifier and is grounded.

6. The startup circuit according to claim 1, wherein: The delay circuit includes an inductor, and the at least one control circuit includes a plurality of control circuits, wherein: The first end of the inductor is connected to the normally closed switch; and The second end of the inductor is connected to a power supply terminal of at least two control circuits among the plurality of control circuits.

7. The startup circuit according to claim 1, wherein: The delay circuit includes a resistor and a first capacitor, and the at least one control circuit includes a plurality of control circuits, wherein: The first capacitor is connected to power supply terminals of at least two control circuits among the plurality of control circuits through the resistor, and is connected in parallel with the normally closed switch.

8. The starting circuit according to any one of claims 1 to 7, wherein: The turns ratio of the primary winding of the transformer to each of the at least one secondary winding is determined according to the power supply voltage required by the corresponding control circuit.

9. The starting circuit according to claim 3 or 6, wherein: The inductance value of the inductor is determined according to the start-up time of the switching power supply.

10. The starting circuit according to claim 4 or 7, wherein: The capacitance value of the first capacitor is determined according to the startup time of the switching power supply.

11. A switching power supply, comprising the starting circuit according to any one of claims 1 to 10.

12. An electrical device comprising the switching power supply according to claim 11.

13. A method for starting a starting circuit of a switching power supply according to any one of claims 1 to 10, comprising: During the startup of the switching power supply, the normally closed switch is in a closed state; The transformer converts the first AC signal outputted from the AC power supply end into at least one second AC signal, and transmits each of the at least one second AC signal to a corresponding rectifier and filter circuit; Each of the at least one rectifying and filtering circuits rectifies and filters the received second AC signal into a DC signal for supplying power to the corresponding control circuit; as well as After the switching power supply is started, the normally closed switch is in an open state.

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