Switching power supply circuit, switching power supply, electronic equipment and power supply system

Abstract

The invention discloses a switching power supply circuit, a switching power supply, electronic equipment and a power supply system, relates to the technical field of electronics, and provides a switching power supply circuit of a novel circuit topology. The switching power supply circuit comprises a transformer which comprises a primary side coil; the first end of the primary coil is coupled to the first end of the first switch, the second end of the primary coil is coupled to the second end of the first switch, and the first capacitor is connected in series between the second end of the primary coil and the second end of the first switch; the second switch and the first switch form a series structure; the series structure is connected in parallel with the second capacitor; a first end of the first inductor is coupled to a connection point of the first switch and the second switch; the second end of the first inductor is used for being coupled with the first output end of the rectifying circuit. The connecting point of the second switch and the second capacitor is used for being coupled with the second output end of the rectifying circuit.

Description

Technical Field

[0001] The embodiments of the present application relate to the field of electronic technology, and in particular to a switching power supply circuit, a switching power supply, an electronic device, and a power supply system. Background Art

[0002] Switching power supply circuits are widely used in power adapters (or chargers) of electronic devices such as mobile phones, watches, and tablet computers, or in switching power supplies of large-screen devices, desktop computers, etc. Among them, flyback switching power supply circuits account for the majority due to their simple circuit structure and low cost. Almost all common consumer power products such as mobile phone chargers and laptop chargers use flyback switching power supply circuits. Summary of the invention

[0003] The embodiments of the present application provide a switching power supply circuit, a switching power supply, an electronic device and a power supply system, which can provide a switching power supply circuit with a novel circuit topology.

[0004] In a first aspect, a switching power supply circuit is provided. The switching power supply circuit comprises: a transformer, the transformer comprises a primary coil; a first switch and a first capacitor, the first end of the primary coil is coupled to the first end of the first switch, the second end of the primary coil is coupled to the second end of the first switch, and the first capacitor is connected in series between the second end of the primary coil and the second end of the first switch; a second switch, the second switch forms a series structure with the first switch; a second capacitor, the series structure is connected in parallel with the second capacitor; a first inductor, the first end of the first inductor is coupled to the connection point of the first switch and the second switch; the second end of the first inductor is used to couple the first output end of the rectifier circuit, and the connection point of the second switch and the second capacitor is used to couple the second output end of the rectifier circuit.

[0005] The embodiment of the present application provides a switching power supply circuit with a novel topology. In terms of structure, the first inductor L b , a first switch S1, a second switch S2 and a second capacitor C bus The boost circuit formed is used to form a power factor correction (PFC) circuit; the transformer Tr, the first switch S1, the second switch S2 and the first capacitor C r It is used to form an asymmetric half bridge converter (AHB); wherein, PFC and AHB share a first switch S1 and a second switch S2, and RCD is omitted, so fewer electronic components are used, making the switching power supply circuit structure simpler.

[0006] In addition, in this structure, the PFC and the flyback converter share the first switch S1 and the second switch S2, which reduces the distance of power transmission and improves efficiency. Since the RCD is omitted, the leakage inductance energy in this application can be stored in the first capacitor C r , and the primary coil N1, the first switch S1 and the first capacitor C r The formed resonant circuit is utilized to improve the circuit conversion efficiency.

[0007] In a possible implementation, the second switch is connected in series to the second end of the first switch; the first end of the first inductor is coupled to the second end of the first switch. Of course, a complementary structure can also be adopted, in which the second switch is connected in series to the first end of the first switch; the first end of the first inductor is coupled to the first end of the first switch.

[0008] In a possible implementation, the switching power supply circuit further includes: a first diode coupled between the first output terminal of the rectifier circuit and the second terminal of the first inductor, wherein the anode of the first diode is coupled to the first output terminal of the rectifier circuit, the cathode of the first diode is coupled to the second terminal of the first inductor, and the first diode is a fast recovery diode. In order to reduce costs, the diodes in the rectifier bridge can still use ordinary diodes, and by adding a fast recovery diode in the above connection method, the second capacitor C bus energy recharge.

[0009] In a possible implementation, the switching power supply circuit further includes: a first diode coupled between the first output terminal of the rectifier circuit and the second terminal of the first inductor, wherein the cathode of the first diode is coupled to the first output terminal of the rectifier circuit, the anode of the first diode is coupled to the second terminal of the first inductor, and the first diode is a fast recovery diode. In order to reduce costs, the diodes in the rectifier bridge can still use ordinary diodes, and by adding a fast recovery diode in the above connection method, the second capacitor C bus energy recharge.

[0010] In a possible implementation, the transformer further includes: a secondary coil; a switching power supply circuit, further including: a third switch and a third capacitor, which are connected in series between the first end and the second end of the secondary coil; and two ends of the third capacitor are used to connect the load. When the third switch is turned on, the current output by the secondary coil charges the third capacitor, and the load is supplied with power through the third capacitor.

[0011] In a possible implementation, the switching power supply circuit further includes: a rectifier circuit, wherein the first input terminal and the second input terminal of the rectifier circuit are used to connect to an AC power supply.

[0012] In a possible implementation, the rectifier circuit includes a rectifier bridge, and the rectifier bridge uses a fast recovery diode. If the reverse recovery time of the diode in the rectifier bridge is too long, the second capacitor C bus Energy re-injection affects the effect of PFC. Therefore, the diodes in the rectifier bridge can use fast recovery diodes with a reverse recovery time of generally less than 500ns.

[0013] In a second aspect, a control method for a switching power supply circuit of the first aspect and any possible implementation thereof is provided, comprising the following steps: in a first stage, controlling the first switch to be turned off and controlling the second switch to be turned on; in a second stage, controlling the first switch to be turned on and controlling the second switch to be turned off, wherein the first stage and the second stage are in the same cycle, and the first stage is before the second stage.

[0014] Thus, in the first stage, the first inductor L is switched on by controlling the second switch to conduct. b Charging to realize the PFC function of the switching power supply circuit; controlling the first switch to turn off, isolating the AHBFC of the subsequent stage from the PFC, and the AHBFC of the subsequent stage is charged through the second capacitor C bus The bus voltage V at both ends b and the first capacitor C r The resonant capacitor voltage V Cr Add to the excitation inductance L m and resonant inductor L r On the line, a resonant current i is generated. Lr In the second stage, the first switch is controlled to be turned on and the first inductor L b Upper current i Lb The current flowing through the first switch is the bus capacitor C bus Charging, realizing the PFC function of the switching power supply circuit; the second switch is turned off, isolating the subsequent AHBFC from the PFC, and the resonant current i Lr The current flows through the first switch. In this way, PFC is used to correct the power factor and reduce harmonics, and the subsequent AHBFC is used to achieve isolation. The volume is reduced by sharing the second switch, which reduces the cost. In addition, in the above process, the leakage inductance current of the transformer can be used by the first capacitor C r storage and in the subsequent stage with the resonant current i Lr The excitation inductance L provided to the transformer in the form of m , thus reducing the leakage current consumption and improving the overall efficiency.

[0015] In a possible implementation, a first sub-stage is included between the first stage and the second stage; in the first sub-stage, the first switch S1 is controlled to be turned off, and the second switch S2 is controlled to be turned off. Since the first switch S1 and the second switch S2 can be controlled to be turned off, the first inductor L b The current i Lb and the second capacitor C r The resonant current i Lr , the charge on the junction capacitance of the first switch S1 is drawn away, thereby realizing zero voltage switching (zero voltage switch, ZVS) of the first switch S1 in the subsequent stage.

[0016] In a possible implementation, a second sub-stage is included between the first stage and the second stage, and the second sub-stage is located after the first sub-stage; in the second sub-stage, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

[0017] In a possible implementation, after the second stage, a third sub-stage is further included; in the third sub-stage, the first switch S1 is controlled to be turned off, and the second switch S2 is controlled to be turned off. Since the first switch S1 and the second switch S2 can be controlled to be turned off, the over-negative resonant current i Lr The charge on the junction capacitance of the second switch S2 is drawn away, thereby achieving ZVS of the second switch S2 in the subsequent stage.

[0018] In a possible implementation, a fourth sub-stage is included after the third sub-stage; in the fourth sub-stage, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

[0019] In a third aspect, a switching power supply is provided, comprising a housing, and a switching power supply circuit provided in the housing as provided in the first aspect and any possible implementation thereof.

[0020] In a possible implementation, the switching power supply includes a charger.

[0021] In a fourth aspect, a chip is provided for executing the control method of the switching power supply circuit as described in the second aspect and any possible implementation manner thereof.

[0022] In a fifth aspect, an electronic device is provided, comprising a switching power supply as provided in the third aspect and possible implementations thereof, and a load connected to the switching power supply.

[0023] In a sixth aspect, a power supply system is provided, comprising a switching power supply as provided in the third aspect and possible implementations thereof, and an electronic device connected to the switching power supply.

[0024] Among them, the technical problems solved by the second to sixth aspects and their possible implementation methods and the technical effects achieved can be referred to the relevant description in the above-mentioned first aspect and its possible implementation methods, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A schematic diagram of the structure of a power supply system provided in an embodiment of the present application;

[0026] Figure 2 A schematic diagram of the structure of an electronic device provided in an embodiment of the present application;

[0027] Figure 3 A schematic diagram of the structure of a Type-C interface provided in an embodiment of the present application;

[0028] Figure 4 A schematic diagram of the structure of a switching power supply circuit provided in an embodiment of the present application;

[0029] Figure 5 A schematic diagram of the structure of a switching power supply circuit provided in another embodiment of the present application;

[0030] Figure 6 A schematic diagram of the structure of a switching power supply circuit provided in yet another embodiment of the present application;

[0031] Figure 7 A schematic diagram of the structure of a switching power supply circuit provided in yet another embodiment of the present application;

[0032] Figure 8 A schematic diagram of the structure of a switching power supply circuit provided in another embodiment of the present application;

[0033] Fig. 9 A schematic diagram of a control waveform of a switch provided in an embodiment of the present application;

[0034] Fig.10 An equivalent circuit diagram of a switching power supply circuit provided in an embodiment of the present application Figure 1 ;

[0035] Fig.11 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application Figure 2 ;

[0036] Fig.12 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 3 ;

[0037] Fig.13 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 4 ;

[0038] Fig.14 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application Figure 5 ;

[0039] Fig.15 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 6 ;

[0040] Fig.16 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 7 ;

[0041] Fig.17 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application Figure 8 ;

[0042] Fig.18 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 9 ;

[0043] Fig.19 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 10 ;

[0044] Fig. 20 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application Figure 10 one;

[0045] Fig.21 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 10 two;

[0046] Fig. 22 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 10 three;

[0047] Fig.23 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application Figure 10 Four;

[0048] Fig.24 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 10 five;

[0049] Fig.25 An equivalent circuit diagram of a switching power supply circuit provided in another embodiment of the present application is shown in FIG. Figure 10 six;

[0050] Fig.26 A schematic diagram of the structure of a switching power supply circuit provided in yet another embodiment of the present application;

[0051] Fig. 27 A schematic diagram of the structure of a switching power supply circuit provided in yet another embodiment of the present application;

[0052] Fig.28 A schematic diagram of the structure of a switching power supply circuit provided in another embodiment of the present application;

[0053] Fig.29 A schematic structural diagram of a switching power supply circuit provided in yet another embodiment of the present application. DETAILED DESCRIPTION

[0054] The technical solutions in some embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings.

[0055] In the following, the terms "first", "second", etc. are used only for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, the meaning of "multiple" is two or more. In addition, in this application, directional terms such as "upper" and "lower" may be defined, including but not limited to, relative to the orientation of the components schematically placed in the accompanying drawings. It should be understood that these directional terms may be relative concepts, which are used for relative description and clarification, and may change accordingly according to the change of the orientation of the components placed in the accompanying drawings. Unless otherwise clearly specified and limited, the term "coupling" should be understood in a broad sense. For example, "coupling" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. When used to describe a three-port switch (also called a switch device, such as a switch tube or a switch transistor), "first end" and "second end" may refer to the connection ends of the switch respectively, and "control end" may refer to the control end of the switch. For example, for a metal-oxide-semiconductor field-effect transistor (MOSFET), the control end may refer to the gate (gate, g) of the MOS tube, the first end may refer to the source (source, s) of the MOS tube, and the second end may refer to the drain (drain, d) of the MOS tube, or the first end may refer to the drain of the MOS tube and the second end may refer to the source of the MOS tube. In the embodiment of the present application, each switch may include a MOSFET, but in order to minimize the increase in internal resistance caused by the switches connected in series on the line, each switch may also include two or more MOSFETs connected in parallel.

[0056] The technical solution in this application will be described below in conjunction with the accompanying drawings.

[0057] The switching power supply circuit and the switching power supply provided in the embodiments of the present application can be applied to electronic devices such as mobile phones, tablet computers, laptop computers, ultra-mobile personal computers (UMPCs), handheld computers, netbooks, personal digital assistants (PDAs), wearable electronic devices, virtual reality devices, or chargers for the above electronic devices.

[0058] Combination Figure 1 As shown, an embodiment of the present application provides a power supply system consisting of a switching power supply 20 and an electronic device 10. Typically, the switching power supply 20 includes a housing, a switching power supply circuit installed in the housing, wherein the input side of the switching power supply circuit is typically connected to the mains via a plug provided on the housing, and the output side of the switching power supply circuit is connected to the electronic device via a plug 200. In addition, typically the switching power supply circuit can be soldered to a printed circuit board PCB in the housing. In some examples, the switching power supply 20 may be a separately sold product such as a charger or a power adapter. Alternatively, the switching power supply 20 may also be a component integrated into the above-mentioned electronic device, so that the switching power supply 20 and the load R inside the electronic device 10 are electrically connected. load Connect to the load R load powered by.

[0059] For example, Figure 2 A schematic structural diagram of an electronic device 10 is shown.

[0060] like Figure 2 As shown, the electronic device 10 may include a processor 110, an external memory interface 120, an internal memory 121, a universal serial bus (USB) interface 130, a charging circuit 140, a power management module 141, a battery 142, an antenna 1, an antenna 2, a mobile communication module 150, a wireless communication module 160, an audio module 170, a speaker 170A, a receiver 170B, a microphone 170C, an earphone interface 170D, a sensor module 180, a button 190, a motor 191, an indicator 192, a camera 193, a display screen 194, and a subscriber identification module (SIM) card interface 195, etc.

[0061] It is to be understood that the structure illustrated in this embodiment does not constitute a specific limitation on the electronic device 10. In other embodiments of the present application, the electronic device 10 may include more or fewer components than shown in the figure, or combine some components, or split some components, or arrange the components differently. The components shown in the figure may be implemented in hardware, software, or a combination of software and hardware.

[0062] Processor 110 may include one or more processing units.

[0063] For example, the processor 110 may include an application processor (AP), a modem processor, a graphics processing unit (GPU), an image signal processor (ISP), a controller, a video codec, a digital signal processor (DSP), a baseband processor, and / or a neural-network processing unit (NPU), etc. Different processing units may be independent devices or integrated into one or more processors.

[0064] In some embodiments, the electronic device 10 may also include one or more processors 110. The processor 110 may be the nerve center and command center of the electronic device 10. The processor 110 may generate an operation control signal according to the instruction operation code and the timing signal to complete the control of fetching and executing instructions.

[0065] The processor 110 may also be provided with a memory for storing instructions and data.

[0066] In some embodiments, the memory in the processor 110 is a cache memory. The memory can store instructions or data that the processor 110 has just used or cyclically used. If the processor 110 needs to use the instruction or data again, it can be directly called from the memory. This avoids repeated access, reduces the waiting time of the processor 110, and thus improves the efficiency of the electronic device 10 system.

[0067] In some embodiments, the processor 110 may include one or more interfaces. The interface may include an inter-integrated circuit (I2C) interface, an inter-integrated circuit sound (I2S) interface, a pulse code modulation (PCM) interface, a universal asynchronous receiver / transmitter (UART) interface, a mobile industry processor interface (MIPI), a general-purpose input / output (GPIO) interface, a subscriber identity module (SIM) interface, and / or a universal serial bus (USB) interface, etc.

[0068] The USB interface 130 is an interface that complies with USB standard specifications, and specifically can be a Mini USB interface, a MicroUSB interface, a USB Type C interface, etc. The USB interface 130 can be used to connect the switching power supply 20 to charge the electronic device 10, can also be used to transmit data between the electronic device 10 and peripheral devices, and can also be used to connect headphones to play audio through the headphones.

[0069] It is understandable that the interface connection relationship between the modules illustrated in the embodiment of the present invention is only a schematic illustration and does not constitute a structural limitation on the electronic device 10. In other embodiments of the present application, the electronic device 10 may also adopt different interface connection methods in the above embodiments, or a combination of multiple interface connection methods.

[0070] The charging circuit 140 is used to receive charging input from a charger. The charger can be a wireless charger or a wired charger. While charging the battery 142 , the charging circuit 140 can also power the electronic device 10 through the power management module 141 .

[0071] In some wired charging embodiments, the charging circuit 140 may receive charging input from a wired charger through the USB interface 130. In some wireless charging embodiments, the charging circuit 140 may receive wireless charging input through a wireless charging coil of the electronic device 10. Then in some examples of the present application, the wireless charger may include the above-mentioned switching power supply 20 and a wireless charging base or a wireless charging pad connected to the switching power supply 20 through the USB interface 130; wherein the wireless charging base or the wireless charging pad is provided with a transmitting coil for wirelessly charging the electronic device 10.

[0072] The power management module 141 is used to connect the battery 142, the charging circuit 140 and the processor 110. The power management module 141 receives input from the battery 142 and / or the charging circuit 140, and supplies power to the processor 110, the internal memory 121, the display screen 194, the camera 193, and the wireless communication module 160. The power management module 141 can also be used to monitor parameters such as battery capacity, battery cycle number, and battery health status (leakage, impedance).

[0073] In some embodiments, the power management module 141 may also be disposed in the processor 110. In other embodiments, the power management module 141 and the charging circuit 140 may also be disposed in the same device.

[0074] In addition, combined Figure 1 As shown, in order to enable the electronic device 10 to be coupled to the switching power supply 20 (charger), the switching power supply 20 may include a plug 200 that is plugged into the USB interface 130 of the electronic device (or wireless charging base). Figure 3 As shown, the above plug may be a Type-C interface. The Type-C interface may include Figure 3 The CC pin shown. The type of external device coupled to the Type-C interface can be identified through the CC pin. Figure 3 As shown, both the A side and the B side of the Type-C interface include two symmetrically arranged VBUS pins (used to provide USB voltage, pins 4 and 9, which are used as voltage output terminals in the embodiment of the present application), a CC pin (pin 5), a D+ pin (pin 6 on the A side and pin 7 on the B side), a D- pin (pin 7 on the A side and pin 6 on the B side)), and an SBU pin (pin 8 is a spare pin, where the A side is marked as SBU1 and the B side is marked as SBU2). In addition, the plug may also have other pins for grounding, idleness, etc., wherein when the plug 200 of the switching power supply 20 is inserted into the USB interface 130 of the electronic device 10, the electronic device 10 can be charged or powered.

[0075] For AC / DC switching power supplies with input power <75W, the general solution in the industry is to directly connect a conversion circuit (for example, a DC / DC conversion circuit, DC / DC) after the rectifier circuit. Figure 4 As shown, a typical topological structure of a switching power supply circuit is provided, which includes: a rectifier circuit 201 and a DC / DC 202. The input side of the rectifier circuit 201 is coupled to an AC power source (for example, the following mainly uses a mains voltage V in As an example, the rectifier circuit 201 generally includes four rectifier diodes (D 11 -D 14 );D 11 The cathode coupling D 13 The cathode, D 11 Anode coupling D 12 The cathode, D 12 The anode is coupled to ground GND, D 13 Anode coupling D 14 The cathode, D 14 The anode is coupled to ground GND. in Since D 11 The anode of D 13 The anode of the rectifier circuit 201 is input as the second input terminal, D 13 The cathode of the DC / DC202 is coupled to the power supply terminal of the subsequent DC / DC202 to output power to the subsequent DC / DC202. In addition, the ground terminal of the DC / DC202 is coupled to the ground GND; the first output terminal and the second output terminal of the DC / DC202 are coupled to the load R load In addition, a bus capacitor C is connected in series between the power supply terminal and the ground terminal of DC / DC202. bus A capacitor C is connected in series between the first output terminal and the second output terminal of DC / DC202. o , the second output terminal of the DC / DC 202 is coupled to the ground GND. Generally, the input side and the output side of the DC / DC 202 are electrically isolated, so in the following scheme, the ground GND coupled to the ground terminal of the input side of the DC / DC 202 is isolated from the ground GND coupled to the second output terminal of the output side of the DC / DC 202.

[0076] For AC / DC switching power supplies with input power ≥ 75W, in order to meet the harmonic limits of the International Electrotechnical Commission IEC61000-3-2 (International Electro Technical Commission, IEC)), a two-stage solution will be used after the rectifier circuit. Figure 5As shown, a power factor correction (PFC) circuit 203 is connected in series between the rectifier circuit 201 and the DC / DC 202 .

[0077] Combination Figure 6 A flyback switching power supply circuit is shown, wherein DC / DC 202 includes: a transformer Tr, a switch Q1, a switch Q2, a primary control chip IC1, and a secondary control chip IC2 (the secondary control chip is also called a synchronous rectifier integrated circuit (SRIC).

[0078] The transformer Tr includes a primary coil N1 and a secondary coil N2. The primary coil is coupled to the switch Q1. For example, the first end p1 of the primary coil N1 is coupled to C bus The first end of the primary coil N1 (the power supply end of the DC / DC 202); the second end p2 of the primary coil N1 is coupled to the ground GND through the switch Q1. The second end s2 of the secondary coil N2 is coupled to the voltage output end V o , for example, the voltage output terminal V o It can be the VBUS pin in the plug 200 (i.e., the Type-C interface), and the first end s1 of the secondary coil N2 is coupled to the ground GND through the switch Q2. Of course, in some examples, the switch Q2 can also be set to connect the second end s2 of the secondary coil N2 to the voltage output terminal V o Among them, the voltage output terminal V o The above-mentioned capacitor C is also arranged between the ground GND o . In addition, it also includes a capacitor C1 and a diode D1 arranged between the first end p1 and the second end p2 of the primary coil N1, wherein the first end of the capacitor C1 is coupled to the first end p1 of the primary coil N1, the second end of the capacitor C1 is coupled to the cathode of the diode D1, and the anode of the diode D1 is coupled to the second end p2 of the primary coil N1; in addition, a resistor R1 is connected in parallel between the two ends of the capacitor C1, and the capacitor C1, the diode D1 and the resistor R1 form an RCD topology. The primary control chip IC1 is coupled to the control end of the switch Q1, and the secondary control chip IC2 is coupled to the control end of the switch Q2.

[0079] In addition, if Figure 6 As shown, the rectifier circuit 201 and C bus A PFC203 is also coupled between the first end (power end) of r And switch Q fpc Among them, the inductor L r The first end is coupled to the rectifier circuit 201 (D 11 cathode), inductor L rThe second end of the diode D2 is coupled to the anode of the diode D2, and the cathode of the diode D2 is coupled to the power supply end C bus The anode of diode D2 is also connected to the switch Q fpc Coupled to ground GND. In addition, the PFC control chip IC pfc Connection switch Q fpc control terminal.

[0080] In addition, the input terminal (D 11 The anode and D 13 An electromagnetic compatibility (EMC) filter circuit 204 (usually an EMC circuit includes an inductor and a capacitor) may be connected in series between the anode of the capacitor and the mains. o One end is used as the voltage output terminal V o , voltage output terminal V o A load switch Q may also be coupled between the plug 200 and the load . Switch Q load The control end and the plug 200 are also connected to the protocol integrated circuit IC. Generally, in some examples, the first end p1 of the primary coil N1 and the first end s1 of the secondary coil N2 may be referred to as the same-name end, and the second end p2 of the primary coil N1 and the second end s2 of the secondary coil N2 may be referred to as the opposite-name end. Of course, those skilled in the art may also define other naming methods for each coil, which is not limited in the embodiments of the present application.

[0081] In this way, the AC mains power passes through the EMC filter circuit 204 (which removes electromagnetic interference from the power grid, such as common mode interference and series mode interference), and the AC current is filtered into DC power by the rectifier circuit 201. Then, the PFC control chip IC pfc By controlling the switch Q pfc The duty cycle of the DC power is adjusted to achieve power factor adjustment of the DC power. Then, it is input to DC / DC202 for voltage conversion. Among them, the control signal output by the primary control chip IC1 (for example, it can be a pulse width modulation (PWM) signal) controls the on or off of the switch Q1; the control signal output by the secondary control chip IC2 (for example, it can be a PWM signal) controls the on or off of the switch Q2. Among them, the flyback working principle of the switching power supply is: during the conduction period of the switch Q1, the energy is stored in the transformer Tr through the primary coil N1. At this time, the switch Q2 is turned off, and the voltage output terminal V o Power supply is provided by capacitor C o Maintain; during the off period of switch Q1, switch Q2 is turned on, and the voltage stored in transformer T rThe energy inside is released through the secondary coil N2. The primary control chip IC1 controls the on-duty cycle or switching frequency of the switch Q1 to achieve stable power output. In order to adjust the output voltage, the protocol IC adjusts the output voltage through interaction with the electronic device. Of course, it should be noted that since the following examples do not involve the control of the protocol IC, the following examples will be simplified to the capacitor C o The two ends of the load R are directly connected load It can be understood that when the switching power supply is used as a stand-alone product, the load R load Refers to the load of the electronic device, which can be considered as the load R load The switching power supply circuit is connected via the above-mentioned plug 200, and the output power is negotiated via the protocol IC.

[0082] In this way, combined Figure 5 and Figure 6 As shown in the figure, the commonly used solutions are two-stage topologies. The front stage of the topology adopts discontinuous conduction mode boost (DCM boost) PFC, and the back stage of the topology is a flyback converter. The DCM Boost PFC converter has the advantages of zero-current-switching (ZCS) of the switch tube and no reverse recovery of the boost diode D2. It is also simple to control and low in cost. It is suitable for small and medium power and cost-sensitive occasions. However, this topology requires multiple electronic components and has a complex structure, which is not conducive to cost control. In addition, the power of this two-stage topology also passes through two stages, and the efficiency is low. And refer to Figure 6 In the DC / DC 202 shown, since an RCD (R1, C1 and D1 are connected to form a topology) is used to absorb the leakage inductance energy of the transformer Tr, the energy is ultimately lost in the resistor R1, and the circuit conversion efficiency is reduced.

[0083] In order to solve the above problems, Figure 7 and Figure 8 In the invention, a novel switching power supply circuit is provided, comprising:

[0084] Transformer r , transformer T r Including primary coil N1; switch S1 and capacitor C r The first end p1 of the primary coil N1 is coupled to the first end of the switch S1, the second end p2 of the primary coil N1 is coupled to the second end of the switch S1, and the capacitor C r Connected in series between the second end p2 of the primary coil N1 and the second end of the switch S1; the switch S2, the switch S2 and the switch S1 are connected in series to form a series structure; the capacitor C bus , the series structure of switch S1 and switch S2 and capacitor C busParallel connection; inductance L b , inductance L b The first end of the inductor L is coupled to the connection point of the switch S1 and the switch S2; b The second end of the switch S2 is used to couple the first output end of the rectifier circuit 201, and the switch S2 and the capacitor C bus The connection point is used to couple the second output terminal of the rectifier circuit 201. Exemplarily, the transformer Tr can be equivalent to the leakage inductance L r (i.e. resonant inductance), magnetizing inductance L m and an ideal transformer with a turns ratio N1:N2 of n:1.

[0085] Among them, compared with Figure 6 The switching power supply circuit shown in the figure, the embodiment of the present application provides a switching power supply circuit with a novel topology. In terms of structure, the inductor L b , switch S1, switch S2 and capacitor C bus The boost circuit formed is used to form PFC; the transformer Tr, the switch S1, the switch S2 and the capacitor C r It is used to form an asymmetric half bridge converter (AHB); wherein, PFC and AHB share switches S1 and S2, and RCD is omitted, so fewer electronic components are used, making the switching power supply circuit structure simpler.

[0086] In addition, in this structure, the PFC and flyback converters share switches S1 and S2, which reduces the distance of power transmission and improves efficiency. Since the RCD is omitted, the leakage inductance energy in this application can be stored in the first capacitor C r , and the primary coil N1, switch S1 and capacitor C r The formed resonant circuit is utilized to improve the circuit conversion efficiency.

[0087] in, Figure 7 and Figure 8 The difference is that in Figure 8 Provided Figure 7 A complementary structure.

[0088] Specifically, Figure 7 The middle switch S2 is connected in series to the second end of the switch S1; the inductor L b The first end of is coupled to the second end of the switch S1. Figure 8 In the embodiment, switch S2 is connected in series to the first end of switch S1; inductor L b The first end of is coupled to the first end of the switch S1.

[0089] In addition, combined Figure 7 and Figure 8As shown, the rectifier circuit 201 and the secondary coil N2 of the transformer Tr are also shown, wherein the switching power supply circuit further includes: a switch S SR And the capacitor C o , connected in series between the first and second ends of the secondary coil N2; capacitor C o The two ends are used to connect the load R load .like Figure 7 or Figure 8 As shown, the load R load One end is coupled to V o , and the other end is coupled to ground GND.

[0090] Among them, Figure 7 and Figure 8 In the embodiment, the rectifier circuit 201 can adopt a rectifier bridge, and its specific structure can be referred to Figure 3 It should be noted that in the description Figure 7 In the diode D 13 The cathode of the diode D is used as the first output terminal of the rectifier circuit 201. 14 The anode of is used as the second output terminal of the rectifier circuit 201; Figure 8 In the diode D 13 The cathode of the diode D is used as the second output terminal of the rectifier circuit 201. 14 The anode of is used as the first output terminal of the rectifier circuit 201.

[0091] Based on the above hardware connection structure, the control method of the switching power supply circuit is as follows:

[0092] S101 . In the first stage, the first switch is controlled to be turned off, and the second switch is controlled to be turned on.

[0093] Exemplarily, a first sub-stage is included between the first stage and the second stage; in the first sub-stage, the first switch is controlled to be turned off, and the second switch is controlled to be turned off. A second sub-stage is included between the first stage and the second stage, and the second sub-stage is located after the first sub-stage; in the second sub-stage, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

[0094] S102. In the second stage, the first switch is controlled to be turned on, and the second switch is controlled to be turned off, wherein the first stage and the second stage are in the same cycle, and the first stage is before the second stage.

[0095] After the second stage, a third sub-stage is included; in the third sub-stage, the first switch is controlled to be turned off and the second switch is controlled to be turned off. After the third sub-stage, a fourth sub-stage is included; in the fourth sub-stage, the first switch is controlled to be turned off and the second switch is controlled to be turned off. In the fifth sub-stage after the fourth sub-stage, the first switch is controlled to be turned off and the second switch is controlled to be turned on.

[0096] Combination Fig. 9 Provides control timing for Figure 7 The control method of the switching power supply circuit shown is specifically described as follows:

[0097] in, Fig. 9 The time period t0-t8 in the example is based on the input voltage of the mains voltage v in Taking the positive half cycle (i.e. one cycle mentioned above) as an example, the transformer Tr is equivalent to the leakage inductance L r , magnetizing inductance L m and an ideal transformer with a turns ratio N1:N2 of n:1, combined with the equivalent circuit diagrams of each stage (see Figure 10-Figure 17 ) A cycle (or working cycle) of the switching power supply circuit is described as follows:

[0098] Reference Fig.10 As shown, at t0~t1 (i.e. the first stage): the control switch S1 is turned off, S2 is turned on, and the input voltage v in Add inductor L b In one switching cycle, v in Approximate constant, inductance L b Upper current i Lb At the same time, the capacitor C bus The bus voltage V at both ends b and capacitor C r The resonant capacitor voltage V Cr Add to the excitation inductance L m and resonant inductor L r On, the resonant current i Lr Linear increase.

[0099] Reference Fig.11 As shown, during t1-t2 (i.e., the first sub-stage), switches S1 and S2 are controlled to be turned off, and the inductor L b The current i Lb and capacitor C r The resonant current i Lr , extracting the charge on the junction capacitance of the switch S1, thereby achieving zero voltage switching (ZVS) of the switch S1 in the subsequent stage.

[0100] Reference Fig.12 As shown, during t2-t3 (i.e., the second sub-stage): the switches S1 and S2 are turned off, the junction capacitance voltage of the switch S1 drops to 0, S1 is not turned on yet, and the inductor L b Upper current i Lb and the resonant current i LrFlows through the body diode of switch S1. Usually switches S1 and S2 are not turned on at the same time. Therefore, when the time (i.e., dead time) of controlling the switch S1 and S2 to be turned off from time t1 is long enough, the mode t2-t3 will appear. Therefore, the stage t2-t3 is optional.

[0101] Reference Fig.13 As shown, during t3-t4 (i.e., the first part of the second stage): the switch S1 is turned on and the switch S2 is turned off, and the inductor L b Upper current i Lb The current flowing through switch S1 is the bus capacitance C bus Charging, resonant current i Lr The current flows through switch S1, and switch S SR On, magnetizing inductance L m The voltage of the secondary coil N2 is clamped, and the current i Lm Linear decrease; the output current i of the secondary coil N2 s .

[0102] Reference Fig.14 As shown, during t4-t5 (i.e., the second part of the second stage): the switch S1 is turned on and the switch S2 is turned off, and the inductor L b Upper current i Lb drops to 0, the resonant current i Lr The current flows through switch S1, and switch S SR On, magnetizing inductance L m The voltage of the secondary coil N2 is clamped, and the excitation inductor current i Lm Linearly decrease, the secondary coil N2 output current i s .

[0103] Reference Fig.15 As shown, at t5-t6 (i.e., the third sub-stage): the switches S1 and S2 are turned off, and the over-negative resonant current i Lr The charge on the junction capacitance of switch S2 is drawn away, thereby achieving ZVS of switch S2 in the subsequent stage; in this stage, switch S SR On, magnetizing inductance L m The voltage of the secondary coil N2 is clamped, and the excitation inductor current i Lm Linearly decrease, the secondary coil N2 output current i s .

[0104] Reference Fig.16 As shown, during t6-t7 (i.e., the fourth sub-stage): the switches S1 and S2 are turned off, the voltage of the junction capacitor of the switch S2 drops to 0, the switch S2 is not turned on yet, and the resonant current i Lr Flows through the body diode of switch S2. Since at this time, the resonant current i Lr and the excitation current i Lmare not equal, there must be current flowing into the ideal transformer, switch S SR The secondary coil N2 is forced to conduct current i s , magnetizing inductance L m Clamped by the secondary voltage, the magnetizing inductor current i Lm Linearly decreases. The resonant inductance L r Approximately bear the bus capacitance C bus The voltage V bus , resonant current i Lr It rises linearly at a very fast speed until it is equal to the excitation current i Lm .

[0105] Reference Fig.17 As shown, during t7-t8 (i.e., the fifth sub-stage), the control switch S1 is turned off and S2 is turned on. If the resonant current i Lr Failed to catch up with the excitation current i Lm , then when switch S2 is turned on, switch S SR Continuous conduction. Input voltage v in Add inductor L b On, the inductor L b Upper current i Lb Linear rise. After time t8, the next control cycle begins, which repeats the stages from t0 to t8.

[0106] Combination Fig. 9 Provides control timing for Figure 8 The control method of the switching power supply circuit shown is specifically described as follows:

[0107] in, Fig. 9 The time period t0-t8 in the example is based on the input voltage of the mains voltage v in Taking the positive half cycle (i.e. one cycle mentioned above) as an example, the transformer Tr is equivalent to the leakage inductance L r , magnetizing inductance L m and an ideal transformer with a turns ratio N1:N2 of n:1, combined with the equivalent circuit diagrams of each stage (see Figure 18-Figure 25 ) A cycle (or working cycle) of the switching power supply circuit is described as follows:

[0108] Reference Fig.18 As shown, at t0~t1 (i.e. the first stage): the control switch S1 is turned off, S2 is turned on, and the input voltage v in Add inductor L b In one switching cycle, v in Approximate constant, inductance L b Upper current i Lb At the same time, the capacitor C bus The bus voltage V at both ends band capacitor C r The resonant capacitor voltage V Cr Add to the excitation inductance L m and resonant inductor L r On, the resonant current i Lr Linear increase.

[0109] Reference Fig.19 As shown, during t1-t2 (i.e., the first sub-stage), switches S1 and S2 are controlled to be turned off, and the inductor L b The current i Lb and capacitor C r The resonant current i Lr , extracting the charge on the junction capacitance of the switch S1, thereby achieving zero voltage switching (ZVS) of the switch S1 in the subsequent stage.

[0110] Reference Fig. 20 As shown, during t2-t3 (i.e., the second sub-stage): the switches S1 and S2 are turned off, the junction capacitance voltage of the switch S1 drops to 0, S1 is not turned on yet, and the inductor L b Upper current i Lb and the resonant current i Lr Flows through the body diode of switch S1. Usually switches S1 and S2 are not turned on at the same time. Therefore, when the time (i.e., dead time) of controlling the switch S1 and S2 to be turned off from time t1 is long enough, the mode t2-t3 will appear. Therefore, the stage t2-t3 is optional.

[0111] Reference Fig.21 As shown, during t3-t4 (i.e., the first part of the second stage): the switch S1 is turned on and the switch S2 is turned off, and the inductor L b Upper current i Lb The current flowing through switch S1 is the bus capacitance C bus Charging, resonant current i Lr The current flows through switch S1, and switch S SR On, magnetizing inductance L m The voltage of the secondary coil N2 is clamped, and the current i Lm Linear decrease; the output current i of the secondary coil N2 s .

[0112] Reference Fig. 22 As shown, during t4-t5 (i.e., the second part of the second stage): the switch S1 is turned on and the switch S2 is turned off, and the inductor L b Upper current i Lb drops to 0, the resonant current i Lr The current flows through switch S1, and switch S SR On, magnetizing inductance L mThe voltage of the secondary coil N2 is clamped, and the excitation inductor current i Lm Linearly decrease, the secondary coil N2 output current i s .

[0113] Reference Fig.23 As shown, at t5-t6 (i.e., the third sub-stage): the switches S1 and S2 are turned off, and the over-negative resonant current i Lr The charge on the junction capacitance of switch S2 is drawn away, thereby achieving ZVS of switch S2 in the subsequent stage; in this stage, switch S SR On, magnetizing inductance L m The voltage of the secondary coil N2 is clamped, and the excitation inductor current i Lm Linearly decrease, the secondary coil N2 output current i s .

[0114] Reference Fig.24 As shown, during t6-t7 (i.e., the fourth sub-stage): the switches S1 and S2 are turned off, the voltage of the junction capacitor of the switch S2 drops to 0, the switch S2 is not turned on yet, and the resonant current i Lr Flows through the body diode of switch S2. Since at this time, the resonant current i Lr and the excitation current i Lm are not equal, there must be current flowing into the ideal transformer, switch S SR The secondary coil N2 is forced to conduct current i s , magnetizing inductance L m Clamped by the secondary voltage, the magnetizing inductor current i Lm Linearly decreases. The resonant inductance L r Approximately bear the bus capacitance C bus The voltage V bus , resonant current i Lr It rises linearly at a very fast speed until it is equal to the excitation current i Lm .

[0115] Reference Fig.25 As shown, during t7-t8 (i.e., the fifth sub-stage), the control switch S1 is turned off and S2 is turned on. If the resonant current i Lr Failed to catch up with the excitation current i Lm , then when switch S2 is turned on, switch S SR Continuous conduction. Input voltage v in Add inductor L b On, the inductor L b Upper current i Lb Linear rise. After time t8, the next control cycle begins, which repeats the stages from t0 to t8.

[0116] Thus, in the first stage (t0-t1), the inductor L is switched on by controlling the second switch to conduct. b Charging, realizing the PFC function of the switching power supply circuit; controlling the switch S1 to turn off, isolating the subsequent AHBFC from the PFC, and the subsequent AHBFC is charged through the capacitor C bus The bus voltage V at both ends b and capacitor C r The resonant capacitor voltage V Cr Add to the excitation inductance L m and resonant inductor L r On the line, a resonant current i is generated. Lr In the second stage (t3-t5), the control switch S1 is turned on and the inductor L b Upper current i Lb The current flowing through switch S1 is the bus capacitance C bus Charging, realizing the PFC function of the switching power supply circuit; switch S2 is turned off, isolating the subsequent AHBFC from the PFC, and the resonant current i Lr The current flows through switch S1. In this way, PFC is used to correct the power factor and reduce harmonics, and the subsequent AHBFC is used to achieve isolation. By sharing switch S1 and switch S2, the volume is reduced and the cost is reduced. In addition, in the above process, the leakage inductance current of the transformer can be r storage and in the subsequent stage with the resonant current i Lr Provided to the excitation inductor L in the form of m , thus reducing the consumption of leakage inductance current and improving overall efficiency. In addition, compared to Figure 6 The solution shown in the embodiment of the present application provides a switch S1, which is equivalent to replacing Figure 6 The diode D2 in the circuit can reduce the energy consumption caused by the voltage drop of the diode D2 and improve the circuit efficiency. Figure 6 The RCD circuit in the circuit has a simpler structure. As mentioned above, since there is no need to use RCD (R1, C1 and D1 are connected to form a topology) to absorb the leakage inductance energy of the transformer Tr, the circuit conversion efficiency is improved.

[0117] Because the rectifier circuit 201 in the embodiment of the present solution adopts a synchronous rectifier mode, when the inductor current i Lb When it drops to 0, the rectifier diode (D 11 and D 14 ) is too long, which may cause the capacitor C bus The energy recharge affects the effect of PFC. Figure 7 and Figure 8 In the rectifier circuit 201 shown in FIG. 1 , the rectifier bridge of the rectifier circuit 201 adopts a fast recovery diode. That is, the diode D11 -D 14 All fast recovery diodes can be used. Among them, the reverse recovery time of ordinary diodes is generally >500ns; the reverse recovery time of the fast recovery diodes provided in the embodiments of the present application is generally less than 500ns, for example, the fast recovery diodes can be fast recovery diodes with a reverse recovery time between 150ns-500ns; or, ultra-fast recovery diodes with a reverse recovery time generally between 15ns-35ns; or, Schottky diodes with a reverse recovery time <10ns, etc.

[0118] In addition, in order to reduce the cost, the diode D 11 -D 14 Ordinary diodes can still be used, refer to Fig.26 and Fig. 27 As shown, by adding a fast recovery diode D 15 , to avoid capacitor C bus For details, refer to Fig.26 As shown, the switching power supply circuit further includes: a first output terminal coupled to the rectifier circuit 201 and the inductor L b The second end of the diode D 15 , where diode D 15 The anode of the diode D is coupled to the first output terminal of the rectifier circuit 201. 15 The cathode coupling inductor L b The second end of the diode D 15 Use fast recovery diodes. Fig. 27 As shown, the switching power supply circuit further includes: a first output terminal coupled to the rectifier circuit 201 and the inductor L b The second end of the diode D 15 , where diode D 15 The cathode of the diode D is coupled to the first output terminal of the rectifier circuit 201. 15 The anode coupling inductance L b The second end of the diode D 15 Use fast recovery diodes.

[0119] A chip is also provided, which can be applied to the above-mentioned switching power supply circuit to control the switch S1, the switch S2 and the switch S SR Implement the control method as described above. Fig.28 As shown, the switches S1, S2 and S SR The control end of is connected to the control chip IC1. In addition, in some examples, reference Fig.29 As shown, it is also possible to use a separate primary side control chip IC1 to control switch S1 and switch S2, and a secondary side control chip IC2 to control switch SSR The control terminals of the switches S1 and S2 can be connected to the primary control chip IC1; SR The control end of is connected to the secondary control chip IC2. It should be noted that the primary control chip IC1 and the secondary control chip IC2 are separated by discrete devices (such as Fig.28 As shown), in the above control scheme, a bus for timing synchronization needs to be set between the primary control chip IC1 and the secondary control chip IC2, so that the primary control chip IC1 and the secondary control chip IC2 provide control signals to the corresponding switches with reference to the same timing.

[0120] Although the present application is described herein in conjunction with various embodiments, in the process of implementing the present application for which protection is claimed, those skilled in the art may understand and implement other variations of the disclosed embodiments by viewing the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other components or steps, and "a" or "an" does not exclude multiple situations. Certain measures are recorded in different dependent claims, but this does not mean that these measures cannot be combined to produce good results.

[0121] The embodiments of the present application have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A switching power supply circuit, characterized in that: include: A transformer, the transformer comprising a primary coil; a first switch and a first capacitor, wherein the first end of the primary coil is coupled to the first end of the first switch, the second end of the primary coil is coupled to the second end of the first switch, and the first capacitor is connected in series between the second end of the primary coil and the second end of the first switch; a second switch, the second switch being connected in series with the first switch to form a series structure; a second capacitor, the series structure being connected in parallel with the second capacitor; A first inductor, wherein the first end of the first inductor is coupled to the connection point between the first switch and the second switch; the second end of the first inductor is used to couple to the first output end of the rectifier circuit, and the connection point between the second switch and the second capacitor is used to couple to the second output end of the rectifier circuit.

2. The switching power supply circuit according to claim 1, characterized in that: The second switch is connected in series to the second end of the first switch; The first end of the first inductor is coupled to the second end of the first switch.

3. The switching power supply circuit according to claim 1, characterized in that: The second switch is connected in series to a first end of the first switch; The first end of the first inductor is coupled to the first end of the first switch.

4. The switching power supply circuit according to claim 2, characterized in that: The switching power supply circuit also includes: a first diode coupled between the first output end of the rectifier circuit and the second end of the first inductor, wherein the anode of the first diode is coupled to the first output end of the rectifier circuit, the cathode of the first diode is coupled to the second end of the first inductor, and the first diode is a fast recovery diode.

5. The switching power supply circuit according to claim 3, characterized in that: The switching power supply circuit also includes: a first diode coupled between the first output end of the rectifier circuit and the second end of the first inductor, wherein the cathode of the first diode is coupled to the first output end of the rectifier circuit, the anode of the first diode is coupled to the second end of the first inductor, and the first diode is a fast recovery diode.

6. The switching power supply circuit according to any one of claims 1 to 5, characterized in that: The transformer further comprises: a secondary coil; The switching power supply circuit further includes: a third switch and a third capacitor, which are connected in series between the first end and the second end of the secondary coil; and the two ends of the third capacitor are used to connect a load.

7. The switching power supply circuit according to any one of claims 1 to 6, characterized in that: The switching power supply circuit further comprises: the rectifier circuit, wherein the first input terminal and the second input terminal of the rectifier circuit are used to connect to an AC power supply.

8. The switching power supply circuit according to claim 7, characterized in that: The rectifier circuit comprises a rectifier bridge, and the rectifier bridge adopts a fast recovery diode.

9. A control method for a switching power supply circuit according to any one of claims 1 to 8, characterized in that: In the first stage, the first switch is controlled to be turned off, and the second switch is controlled to be turned on; In the second stage, the first switch is controlled to be turned on, and the second switch is controlled to be turned off, wherein the first stage and the second stage are in the same cycle, and the first stage is before the second stage.

10. The method according to claim 9, characterized in that A first sub-stage is further included between the first stage and the second stage; In the first sub-phase, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

11. The method according to claim 10, characterized in that A second sub-stage is further included between the first stage and the second stage, and the second sub-stage is located after the first sub-stage; In the second sub-phase, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

12. The method according to any one of claims 9 to 11, characterized in that: After the second stage, a third sub-stage is also included; In the third sub-phase, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

13. The method according to claim 12, characterized in that A fourth sub-stage is further included after the third sub-stage; In the fourth sub-phase, the first switch is controlled to be turned off, and the second switch is controlled to be turned off.

14. A switching power supply, characterized in that: It comprises a housing, and a switching power supply circuit as claimed in any one of claims 1 to 8 arranged in the housing.

15. The switching power supply according to claim 14, characterized in that: The switching power supply includes a charger.

16. A chip, characterized in that: Used to execute the control method of the switching power supply circuit as described in any one of claims 9 to 13.

17. An electronic device, characterized in that: The invention comprises the switching power supply as claimed in claim 14, and a load connected to the switching power supply.

18. A power supply system, characterized in that: It comprises the switching power supply as claimed in claim 14 or 15 and an electronic device connected to the switching power supply.

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