A multi-port charging circuit and switching power supply

Abstract

This invention discloses a multi-port charging circuit and a switching power supply, relating to the field of charging technology. The circuit includes: an electromagnetic compatibility (EMC) module, an absorption module, a synchronous rectification module, a voltage regulation feedback module, a pulse width modulation (PWM) control module, and a transformer T1. The EMC module is electrically connected to the absorption module via the primary-side rectification module; the absorption module is electrically connected to the primary side of the transformer T1; the synchronous rectification module is electrically connected to the secondary side of the transformer T1; the voltage regulation feedback module is electrically connected to the synchronous rectification module; and the PWM control module is electrically connected to the EMC module and the primary side of the transformer T1. This invention provides a circuit with more stable charging voltage and capable of multi-port charging, along with a matching switching power supply.

Description

Technical Field

[0001] This utility model relates to the field of charging technology, and in particular to a multi-port charging circuit and a switching power supply. Background Technology

[0002] Currently, most electronic devices use switching power supplies to save energy and improve efficiency. With the increasing popularity and application of portable electronic devices, chargers for these devices are typically equipped with multiple charging ports to meet the charging requirements of these devices simultaneously.

[0003] For safety reasons and to prevent equipment failure, there is a need for a switching power supply with a more stable charging voltage and the ability to charge multiple ports. Utility Model Content

[0004] In view of this, the present invention proposes a multi-port charging circuit and a switching power supply to solve the current problem of needing a switching power supply with more stable charging voltage and capable of multi-port charging.

[0005] The technical solution of this utility model is implemented as follows:

[0006] According to a first aspect, this utility model provides a multi-port charging circuit, the circuit comprising:

[0007] Electromagnetic compatibility module, absorption module, synchronous rectification module, voltage regulation feedback module, pulse width modulation control module, and transformer T1;

[0008] The electromagnetic compatibility module, absorption module, and pulse width modulation control module are located on the primary side of transformer T1, while the synchronous rectification module and voltage regulation feedback module are located on the secondary side of transformer T1. The input voltage is electrically connected to the electromagnetic compatibility module. The electromagnetic compatibility module is electrically connected to the absorption module through the primary side rectification module. The absorption module is electrically connected to the primary side of transformer T1. The synchronous rectification module is electrically connected to the secondary side of transformer T1 and is also connected to the load, providing output voltage to the load. The voltage regulation feedback module is electrically connected to the synchronous rectification module. The pulse width modulation control module is electrically connected to the electromagnetic compatibility module and the primary side of transformer T1. The pulse width modulation control module is equipped with an isolation device, and it samples and provides feedback from the output voltage through the isolation device.

[0009] In conjunction with the first aspect, in the first embodiment of the first aspect, the electromagnetic compatibility module in the circuit includes:

[0010] Resistors R1, R2, R3, R4, capacitor CX1, and common-mode inductor LF1;

[0011] Resistors R1 and R2 are connected in series between the live wire and the neutral wire. One end of resistor R1 is electrically connected to the live wire, and the other end of resistor R1 is electrically connected to one end of resistor R2. The other end of resistor R2 is electrically connected to the neutral wire. Resistors R3 and R4 are connected in series between the live wire and the neutral wire. One end of resistor R3 is electrically connected to the live wire, and the other end of resistor R3 is electrically connected to one end of resistor R4. The other end of resistor R4 is electrically connected to the neutral wire. Resistors R1 and R2 are electrically connected to each other. Capacitor CX1 is connected between the live wire and the neutral wire. Common mode inductor LF1 has four pins. The first pin of common mode inductor LF1 is connected to the live wire, the second pin is connected to the neutral wire, the third pin is connected to the absorption module, and the fourth pin is connected to the pulse width modulation control module.

[0012] In conjunction with the first embodiment of the first aspect, in the second embodiment of the first aspect, a varistor NR1, a fuse F1, and a thermistor NTC1 are provided before the front end of the electromagnetic compatibility module.

[0013] Varistor NR1 is connected between the live wire and the neutral wire. Fuse F1 and thermistor NTC1 are connected in series and electrically connected to the live wire. One end of fuse F1 is electrically connected to the live wire, and the other end of fuse F1 is electrically connected to one end of thermistor NTC1. The other end of thermistor NTC1 is electrically connected to the second end of common mode inductor LF1.

[0014] In conjunction with the first embodiment of the first aspect, in the third embodiment of the first aspect, the pulse width modulation control module in the circuit includes:

[0015] The main control chip U1, capacitor C2, resistor R15, resistor R12, the receiver of optocoupler U3B, capacitor C7, diode ZD1, capacitor C6, resistor R20, diode ZD2, resistor R19, capacitor C9, resistor R26, capacitor C10, electrolytic capacitor EC2, resistor R25, capacitor C11, diode D4, resistor RS1, resistor RS2, resistor RS3 and resistor RS4;

[0016] The first pin of the main control chip U1 is electrically connected to the synchronous rectification module. The third and fourth pins of the main control chip U1 are electrically connected to the synchronous rectification module via a series capacitor C2. The fifth pin of the main control chip U1 is grounded via a series capacitor C9 and resistor R26. Resistors RS1, RS2, RS3, and RS4, connected in parallel, are electrically connected to the branch formed by the series capacitor C9 and resistor R26. The sixth pin of the main control chip U1 is electrically connected to the primary side of transformer T1 via a series diode D4 and resistor R24. A resistor R25 and a capacitor C11 are connected in parallel between the positive and negative terminals of capacitor C4. Resistor R25 and capacitor C11 are connected in series. A capacitor C10 and an electrolytic capacitor EC2 are located between the negative terminal of capacitor C4 and the sixth pin of the main control chip U1. The capacitor EC2 is connected in parallel. The seventh pin of the main control chip U1 is connected to the power supply ground through the series resistor R26. The ninth pin of the main control chip U1 is grounded through the capacitor C7 and diode ZD1 connected in parallel. The tenth pin of the main control chip U1 is connected to the fourth terminal of the primary side of the transformer T1 through the resistor R19. The output terminal of the receiver of the optocoupler U3B is electrically connected to the ninth pin of the main control chip U1. The resistor R22 is electrically connected to the ninth pin of the main control chip U1. The input terminal of the receiver of the optocoupler U3B is connected to the static ground and electrically connected to the capacitor C7. The receiver of the optocoupler U3B and the capacitor C7 are connected in series on the ninth pin of the main control chip U1 and in parallel with the resistor R22. The eleventh pin of the main control chip U1 is electrically connected to the primary side rectifier module through the series resistor R15. The twelfth pin of the main control chip U1 is grounded.

[0017] In conjunction with the third embodiment of the first aspect, in the fourth embodiment of the first aspect, the primary-side rectifier module in the circuit includes:

[0018] Rectifier bridge BD1, diode D1, diode D2, polarized capacitor EC1, and capacitor C3;

[0019] The first terminal of rectifier bridge BD1 is electrically connected to the third terminal of common-mode inductor LF1. The first terminal of rectifier bridge BD1 is electrically connected to resistor R15 via series diode D1. The anode of diode D1 is electrically connected to the first terminal of rectifier bridge BD1, and the cathode of diode D1 is electrically connected to resistor R15. The second terminal of rectifier bridge BD1 is electrically connected to the fourth terminal of common-mode inductor LF1. The fourth terminal of common-mode inductor LF1 is electrically connected to resistor R15 via series diode C2. The anode of diode C2 is electrically connected to the fourth terminal of common-mode inductor LF1. The diode C2 is electrically connected to the resistor R15. The third terminal of the rectifier bridge BD1 is electrically connected to the absorption module. The fourth terminal of the rectifier bridge BD1 is grounded. A polarized capacitor EC1 and a capacitor C3 are connected in parallel between the third and fourth terminals of the rectifier bridge BD1. One end of the capacitor C3 is connected between the third and fourth terminals of the rectifier bridge BD1, and the other end of the capacitor C3 is connected to the power supply ground. The positive terminal of the polarized capacitor EC1 is connected between the third and fourth terminals of the rectifier bridge BD1, and the negative terminal of the polarized capacitor EC1 is connected to the power supply ground.

[0020] In conjunction with the fourth embodiment of the first aspect, in the fifth embodiment of the first aspect, the absorption module in the circuit includes:

[0021] Capacitor C1, resistors R7, R5, R8, R6, R8A, and diode D3;

[0022] The first terminal of the primary side of transformer T1 is connected to the synchronous rectifier module 300 and the positive terminal of diode D3 through series resistor B1. The negative terminal of diode D3 is electrically connected to the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1 through the first branch, the second branch and the third branch arranged in parallel.

[0023] The first branch consists of capacitor C1 and resistor R7 connected in series. One end of capacitor C1 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of capacitor C1 is electrically connected to one end of resistor R7, and the other end of resistor R7 is electrically connected to the negative terminal of diode D3.

[0024] The second branch consists of resistors R5 and R8 connected in series. One end of resistor R5 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of resistor R5 is electrically connected to one end of resistor R8, and the other end of resistor R8 is electrically connected to the negative terminal of diode D3.

[0025] The third branch consists of resistors R6 and R8A connected in series. One end of resistor R6 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of resistor R6 is electrically connected to one end of resistor R8A, and the other end of resistor R8A is electrically connected to the negative terminal of diode D3.

[0026] In conjunction with the fifth embodiment of the first aspect, in the sixth embodiment of the first aspect, the synchronous rectification module in the circuit includes:

[0027] Rectifier chip U2, resistor R9, capacitor C8, resistor R14, MOSFET Q1, resistor R23, and capacitor C5;

[0028] The first pin of rectifier chip U2 supplies power to the load through common-mode inductor LF3. The first terminal of common-mode inductor LF3 is electrically connected to the eighth terminal of the secondary side of transformer T1 and the first pin of rectifier chip U2. The second terminal of common-mode inductor LF3 is electrically connected to the seventh terminal of the secondary side of transformer T1 through series MOSFET Q1. The third terminal of common-mode inductor LF3 is electrically connected to the V+ terminal. The fourth terminal of common-mode inductor LF3 is electrically connected to the V- terminal. The drain of MOSFET Q1 is electrically connected to the seventh terminal of the secondary side of transformer T1. The source of MOSFET Q1 is electrically connected to the second terminal of common-mode inductor LF3. The gate of MOSFET Q1 is electrically connected to the fifth pin of rectifier chip U2. A resistor R9 and a capacitor C8 are connected in parallel between the drain and source of MOSFET Q1. The resistor R9 and capacitor C8 are connected in series. One end of the resistor R9 is electrically connected to the drain of the MOSFET and the seventh terminal of the secondary side of transformer T1. The other end of the resistor R9 is electrically connected to one end of the capacitor C8. The other end of the capacitor C8 is electrically connected to the source of MOSFET Q1. The second pin of rectifier chip U2 is connected to signal ground. The third pin of rectifier chip U2 is connected to signal ground through a series resistor R23. The fourth pin of rectifier chip U2 is connected to signal ground through a series capacitor C5. The sixth pin of rectifier chip U2 is electrically connected to the seventh terminal of the secondary side of transformer T1 through a series resistor R14.

[0029] In conjunction with the sixth embodiment of the first aspect, in the seventh embodiment of the first aspect, the voltage regulation feedback module in the circuit includes:

[0030] Resistors R10, R16, R21, R13, the light source of optocoupler U3A, capacitor C4, resistor R14, and Zener diode U4;

[0031] The first pin of rectifier chip U2 is grounded through the fourth and fifth branches connected in parallel.

[0032] The fourth branch consists of a resistor R10, the light source of the optocoupler U3A, and a Zener diode U4 connected in series. One end of the resistor R10 is electrically connected between the first end of the common-mode inductor LF3 and the eighth end of the secondary side of the transformer T1. The other end of the resistor R10 is electrically connected to the input end of the light source of the optocoupler U3A. The output end of the light-emitting diode U4 is electrically connected to the negative terminal of the Zener diode U4, and the positive terminal of the Zener diode U4 is connected to the signal ground.

[0033] The fifth branch consists of resistors R16 and R21 connected in series. One end of resistor R16 is electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary side of transformer T1. The other end of resistor R16 is electrically connected to one end of resistor R21, and the other end of resistor R21 is connected to signal ground. Resistor R13 is connected in parallel between the input and output terminals of the light source of optocoupler U3A. The end of resistor R21 furthest from signal ground is connected to the positive terminal of Zener diode U4. Resistor R16 and resistor R21, and the light source of optocoupler U3A and Zener diode U4 are electrically connected through capacitor C4 and resistor R18 connected in series. One end of capacitor C4 is electrically connected between the light source of optocoupler U3A and Zener diode U4, and the other end of capacitor C4 is electrically connected to one end of resistor R18. The other end of resistor C4 is electrically connected between resistors R16 and R21.

[0034] In conjunction with the sixth embodiment of the first aspect, in the eighth embodiment of the first aspect, the circuit further includes polarized capacitor EC3, polarized capacitor EC4, capacitor CY1, and capacitor CY2. Polarized capacitors EC3 and EC4 are electrically connected to the secondary winding of transformer T1. The positive terminals of polarized capacitors EC3 and EC4 are electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary winding of transformer T1. The negative terminals of polarized capacitors EC3 and EC4 are electrically connected between the second terminal of common-mode inductor LF3 and the seventh terminal of the secondary winding of transformer T1. The negative terminals of polarized capacitors EC3 and EC4 are both connected to signal ground. Capacitors CY1 and CY2 are electrically connected between signal ground and power ground.

[0035] According to a second aspect, the present invention also provides a switching power supply, the switching power supply comprising: a multi-port charging circuit according to any one of the preceding claims.

[0036] The multi-port charging circuit and switching power supply of this utility model have the following advantages over the prior art:

[0037] This paper presents a flyback switching power supply by incorporating an electromagnetic compatibility (EMC) module, an absorption module, a synchronous rectification module, a voltage regulation feedback module, a pulse width modulation (PWM) control module, and a transformer. The PWM control module regulates the input voltage to store energy at the transformer's primary side. Under the control of the PWM control module, the previously stored back electromotive force is released to the load using the transformer's primary side, thus charging the load. This flyback switching power supply can achieve multiple outputs, simultaneously charging multiple electronic devices within the load. Furthermore, the EMC module effectively suppresses electromagnetic interference and improves the circuit's resistance to electromagnetic interference. The system enhances its electromagnetic interference (EMI) immunity by optimizing the circuit to meet relevant EMI standards. An absorption module controls the discharge voltage from the primary side within a preset range. A synchronous rectification module and a voltage regulation feedback module perform synchronous rectification and voltage regulation feedback of the input voltage, respectively. An isolation device samples and feeds back the output voltage, providing a feedback signal to the pulse width modulation (PWM) control module. This process achieves isolated feedback; when the output voltage exceeds a preset value, the isolation device feeds back to the PWM control module, which then generates a corresponding protection signal. Therefore, this invention can not only charge multiple electronic devices simultaneously but also provide a stable voltage, achieving more stable and safer charging. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0039] Figure 1 This is a schematic diagram of the multi-port charging circuit of this utility model;

[0040] Figure 2 This is a circuit diagram of the multi-port charging circuit of this utility model. Detailed Implementation

[0041] The technical solutions of this utility model will be clearly and completely described below with reference to the embodiments of this utility model. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. Based on the embodiments of this utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of this utility model.

[0042] It should be noted that similar reference numerals and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0043] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0044] Currently, most electronic devices use switching power supplies to save energy and improve efficiency. With the increasing popularity and application of portable electronic devices, chargers for these devices are typically equipped with multiple charging ports to meet the charging requirements of these devices simultaneously.

[0045] For safety reasons and to prevent equipment failure, there is a need for a switching power supply with a more stable charging voltage and the ability to charge multiple ports.

[0046] The multi-port charging circuit and switching power supply provided in this manual are intended to provide a circuit with a more stable charging voltage and the ability to perform multi-port charging, as well as a matching switching power supply.

[0047] Please see Figure 1 and Figure 2 , Figure 1 A schematic diagram of the structure of the multi-port charging circuit according to an embodiment of the present invention is shown. Figure 2 A circuit diagram of a multi-port charging circuit according to an embodiment of the present invention is shown.

[0048] The circuit specifically includes:

[0049] Electromagnetic compatibility (EMC) module 100, absorption module 200, synchronous rectification module 300, voltage regulation feedback module 400, and pulse width modulation module 100. The system comprises a Modulation (PWM) control module 500 and a transformer T1. An EMC module 100, an absorption module 200, and the PWM control module 500 are located on the primary side of the transformer T1. A synchronous rectification module 300 and a voltage regulation feedback module 400 are located on the secondary side of the transformer T1. The input voltage is electrically connected to the EMC module 100. The EMC module 100 is electrically connected to the absorption module 200 via the primary rectification module. The absorption module 200 is electrically connected to the primary side of the transformer T1. The synchronous rectification module 300 is electrically connected to the secondary side of the transformer T1 and is also connected to the load, providing an output voltage to the load. The voltage regulation feedback module 400 is electrically connected to the synchronous rectification module 300. The PWM module 500 is electrically connected to the EMC module 100 and the primary side of the transformer T1. The PWM module 500 includes an isolation device, which samples and provides feedback from the output voltage.

[0050] In this embodiment, the input voltage is the AC mains voltage. After the input voltage is connected to the circuit, it will first enter the EMC module, i.e., the EMC circuit.

[0051] More specifically, the EMC module 100 in this circuit includes:

[0052] Resistors R1, R2, R3, and R4, capacitor CX1, and common-mode inductor LF1 constitute the EMC module 100, i.e., the EMC circuit. Resistors R1 and R2 are connected in series between the live wire (L line) and the neutral wire (N line). One end of resistor R1 is electrically connected to the live wire, and the other end of resistor R1 is electrically connected to one end of resistor R2. The other end of resistor R2 is electrically connected to the neutral wire. Resistors R3 and R4 are connected in series between the live wire and the neutral wire. One end of resistor R3 is connected to the live wire... Electrically connected, the other end of resistor R3 is electrically connected to one end of resistor R4, the other end of resistor R4 is electrically connected to the neutral wire, and resistors R1 and R2 are electrically connected to resistors R3 and R4. Capacitor CX1 is similarly connected between the live wire and the neutral wire. Common mode inductor LF1 has four pins. The first pin of common mode inductor LF1 is connected to the live wire, the second pin of common mode inductor LF1 is connected to the neutral wire, the third pin of common mode inductor LF1 is electrically connected to the primary side rectifier module, and the fourth pin of common mode inductor LF1 is electrically connected to the PWM control module 500.

[0053] Resistors R1, R2, R3, and R4 will perform filtering and discharge. Using multiple resistors can effectively distribute the power carried by each resistor, protect the resistors, and improve the filtering and discharge effect. Capacitor CX1 is a differential mode capacitor (X capacitor), which plays a role in filtering differential mode interference. Common mode inductor LF1 can attenuate common mode current.

[0054] The EMC module 100 can effectively suppress electromagnetic interference in the circuit, while improving the circuit's own anti-electromagnetic interference capability, optimizing the generated electromagnetic interference, and making the circuit comply with the corresponding electromagnetic compatibility standards.

[0055] In this embodiment, a varistor NR1, a fuse F1, and a thermistor NTC1 are provided at the front end of the EMC module 100, i.e. before the EMC module 100 is connected to the input voltage. The varistor NR1 is connected between the live wire and the neutral wire. The fuse F1 and the thermistor NTC1 are connected in series and electrically connected to the live wire. One end of the fuse F1 is electrically connected to the live wire, and the other end of the fuse F1 is electrically connected to one end of the thermistor NTC1. The other end of the thermistor NTC1 is electrically connected to the second end of the common mode inductor LF1.

[0056] When the current flowing through the switching power supply is too large, the fuse F1 will trip to protect the circuit; the varistor NR1 can suppress the spikes in the transient input voltage; connecting a thermistor NTC1 in series at the input terminal of the input voltage can increase the impedance of the circuit, thus effectively suppressing the surge current formed by the surge voltage generated when the circuit starts to run. When the circuit enters steady-state operation, the thermistor NTC1 heats up due to the continuous operating current in the circuit, making the resistance value of the thermistor NTC1 very small, and its impact on the circuit can be almost completely ignored.

[0057] More specifically, the PWM control module 500 in this circuit includes:

[0058] The main control chip U1, capacitor C2, resistor R15, resistor R12, the receiver of optocoupler U3B, capacitor C7, diode ZD1, capacitor C6, resistor R20, diode ZD2, resistor R19, capacitor C9, resistor R26, capacitor C10, electrolytic capacitor EC2, resistor R25, capacitor C11, diode D4, resistor RS1, resistor RS2, resistor RS3, and resistor RS4 constitute the PWM control module 500, i.e., the PWM circuit.

[0059] The main control chip U1 has 12 pins. The first pin, DRAIN, is electrically connected to the synchronous rectification module 300. The third and fourth pins, the two GND pins, are electrically connected to the synchronous rectification module 300 via a series capacitor C2. The fifth pin, a single GND pin, is grounded via a series capacitor C9 and resistor R26. One end of capacitor C9 is electrically connected to the fifth pin of the main control chip U1, and the other end is electrically connected to one end of resistor R26. The other end is connected to the power supply ground. A branch consisting of a capacitor C9 and a resistor R26, connected in series, is electrically connected to resistors RS1, RS2, RS3, and RS4, which are connected in parallel. Resistors RS1, RS2, RS3, and RS4 are all electrically connected between the power supply ground and the static ground. Furthermore, one end of each of resistors RS1, RS2, RS3, and RS4 is connected between capacitor C9 and the fifth pin of the main control chip U1, and the other end of each of resistors RS1, RS2, RS3, and RS4 is connected to resistor R26. Between pin 6 and power ground, pin 6 (VDD) of the main control chip U1 is electrically connected to the primary side of transformer T1 via diode D4 and resistor R24, which are connected in series. The negative terminal of capacitor C4 is electrically connected to pin 6 of the main control chip U1, and the positive terminal of capacitor C4 is electrically connected to one end of resistor R24. The other end of resistor R24 ​​is connected to the fourth terminal of the primary side of transformer T1. Resistor R25 and capacitor C11 are connected in parallel between the positive and negative terminals of capacitor C4, and resistor R25 and capacitor C11 are connected in series. One end of resistor R25 is electrically connected to pin 6 of the main control chip U1. The other end of resistor R25 is electrically connected to one end of capacitor C11, and the other end of capacitor C11 is electrically connected to resistor R24. Between the negative terminal of capacitor C4 and the sixth pin of the main control chip U1, there are capacitor C10 and electrolytic capacitor EC2. Capacitor C10 and electrolytic capacitor EC2 are connected in parallel. One end of capacitor C10 is connected between the negative terminal of capacitor C4 and the sixth pin of the main control chip U1, and the other end of capacitor C10 is connected to ground. The positive terminal of electrolytic capacitor EC2 is connected between the negative terminal of capacitor C4 and the sixth pin of the main control chip U1, and the negative terminal of electrolytic capacitor EC2 is connected to ground.

[0060] The seventh pin (CS pin) of the main control chip U1 is connected to the power ground through a series resistor R26. The ninth pin (COMP pin) of the main control chip U1 is grounded through a capacitor C7 and a diode ZD1 connected in parallel. One end of capacitor C7 is electrically connected to the ninth pin of the main control chip U1, and the other end of capacitor C7 is connected to ground. The cathode of diode ZD1 is electrically connected to the ninth pin of the main control chip U1, and the anode of diode ZD1 is connected to ground.

[0061] The tenth pin (VS pin) of the main control chip U1 is connected to the fourth terminal of the primary side of transformer T1 through resistor R19. A capacitor C6, a resistor R20, and a diode ZD2 are electrically connected in parallel between resistor R19 and ground. One end of capacitor C6 and resistor R20 is connected between resistor R19 and the tenth pin of the main control chip U1, and the other end is grounded. The cathode of diode ZD2 is connected between resistor R19 and the tenth pin of the main control chip U1, and the anode of diode ZD2 is connected to... The output terminal of the receiver of optocoupler U3B is electrically connected to pin 9 of the main control chip U1. Resistor R22 is also electrically connected to pin 9 of the main control chip U1. The input terminal of the receiver of optocoupler U3B is connected to ground and to capacitor C7. The receiver of optocoupler U3B and capacitor C7 are connected in series on pin 9 of the main control chip U1 and in parallel with resistor R22. Pin 11, the HV pin, of the main control chip U1 is electrically connected to the primary-side rectifier module through series resistor R15. Pin 12, the GND pin, of the main control chip U1 is grounded.

[0062] It should be noted that the second pin (NC pin) and the eighth pin (OTP pin) of the main control chip U1 are not used in this circuit.

[0063] The PWM control module 500 is the main and core part of this circuit. After the EMC module 100 obtains the input voltage, it feeds the input voltage, which is the mains power, back to the PWM control module 500 at the input end for processing. The PWM control module 500 is responsible for regulating the output power to achieve a dynamic balance.

[0064] Pin 6 of the main control chip U1 is powered by the primary side, and pin 11 is connected to the rectified high-voltage DC power supply for chip startup and internal high-voltage circuitry. The conduction of the MOSFET inside the main control chip U1 is controlled by detecting the voltage at the corresponding pin. When the MOSFET inside the main control chip U1 is on and forms a circuit, the primary winding terminal of transformer T1 is negative, and the secondary winding terminal is also negative. The synchronous rectifier module 300 and the voltage regulation feedback module 400 connected to the secondary side of transformer T1 are not working, and transformer T1 stores energy. When the MOSFET inside the main control chip U1 is off, the primary winding of transformer T1 has a back electromotive force that needs to be released. At this time, the primary winding terminal of transformer T1 is positive, and the secondary winding terminal is also positive. The synchronous rectifier module 300 and the voltage regulation feedback module 400 connected to the secondary side of transformer T1 process the input voltage accordingly. It can be seen that this circuit uses a flyback power supply.

[0065] The receiver of optocoupler U3B and the light source of optocoupler U3A (described later) together constitute a complete optocoupler. The optocoupler can sample and provide feedback on the output voltage. When the light source of optocoupler U3B is energized and turned on, it can further turn on the receiver, thereby outputting a feedback signal to the main control chip U1. Since the receiver of optocoupler U3B is an isolation device, this process achieves isolated feedback. When the output voltage is detected to exceed the preset value, it is fed back to the main control chip U1 through the receiver of optocoupler U3B. The main control chip U1 will generate a corresponding signal for protection.

[0066] In this embodiment, the primary-side rectifier module consists of a rectifier bridge BD1, diodes D1 and D2, a polarized capacitor EC1, and a capacitor C3. The rectifier bridge BD1 has four terminals. The first terminal of the rectifier bridge BD1 is electrically connected to the third terminal of the common-mode inductor LF1. The first terminal of the rectifier bridge BD1 is also electrically connected to a resistor R15 via a series diode D1. The anode of diode D1 is electrically connected to the first terminal of the rectifier bridge BD1, and the cathode of diode D1 is electrically connected to the resistor R15. The second terminal of the rectifier bridge BD1 is electrically connected to the fourth terminal of the common-mode inductor LF1. The fourth terminal of the common-mode inductor LF1 is connected to a resistor R15 via a series diode C2. 5. Electrical connections: The positive terminal of diode C2 is electrically connected to the fourth terminal of common-mode inductor LF1, and the negative terminal of diode C2 is electrically connected to resistor R15. The third terminal of rectifier bridge BD1 is electrically connected to absorption module 200. The fourth terminal of rectifier bridge BD1 is grounded. A polarized capacitor EC1 and a capacitor C3 are connected in parallel between the third and fourth terminals of rectifier bridge BD1. One end of capacitor C3 is connected between the third and fourth terminals of rectifier bridge BD1, and the other end of capacitor C3 is connected to power supply ground. The positive terminal of polarized capacitor EC1 is connected between the third and fourth terminals of rectifier bridge BD1, and the negative terminal of polarized capacitor EC1 is connected to power supply ground.

[0067] It is understandable that the primary-side rectifier module is the rectifier circuit on the primary side of transformer T1. The input voltage received by EMC module 100 is rectified on the primary side through rectifier bridge BD1 in the primary-side rectifier module, and the voltage waveform is corrected through the charging and discharging of polarized capacitor EC1 and capacitor C3.

[0068] More specifically, the absorption module 200 in this circuit includes:

[0069] The electronic components, including capacitor C1, resistors R7, R5, R8, R6, R8A, and diode D3, constitute the absorption module 200, i.e., the absorption circuit. The first terminal of the primary winding of transformer T1 is connected to the synchronous rectification module 300 and the positive terminal of diode D3 via a series resistor B1. The negative terminal of diode D3 is electrically connected to the third terminal of rectifier bridge BD1 and the third terminal of the primary winding of transformer T1 via three parallel branches: the first branch, the second branch, and the third branch. The first branch consists of capacitor C1 and resistor R7 connected in series. One end of capacitor C1 is electrically connected to the third terminal of rectifier bridge BD1 and the third terminal of the primary winding of transformer T1. The other end of capacitor C1... One branch is electrically connected to one end of resistor R7, and the other end of resistor R7 is electrically connected to the negative terminal of diode D3. The second branch is composed of resistors R5 and R8 connected in series. One end of resistor R5 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of resistor R5 is electrically connected to one end of resistor R8, and the other end of resistor R8 is electrically connected to the negative terminal of diode D3. The third branch is composed of resistors R6 and R8A connected in series. One end of resistor R6 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of resistor R6 is electrically connected to one end of resistor R8A, and the other end of resistor R8A is electrically connected to the negative terminal of diode D3.

[0070] Since transformer T1 also has winding coils and generated magnetism, when the primary winding circuit of transformer T1 is disconnected, there is a back electromotive force in the primary winding that needs to be released. Therefore, at this time, the same-name terminal of the primary winding is the positive terminal. At this time, the current flows through diode D3 to charge capacitor C1. Capacitor C1 then discharges through other resistors in the absorption module 200. In this way, the absorption module 200 can be used to control the discharge voltage within a preset range.

[0071] In this embodiment, the third terminal of the rectifier bridge BD1 and the third terminal of the primary side of the transformer T1 are both electrically connected to the VBUS terminal.

[0072] More specifically, the synchronous rectification module 300 in this circuit includes:

[0073] The rectifier chip U2, resistor R9, capacitor C8, resistor R14, MOSFET Q1, resistor R23, and capacitor C5 constitute the synchronous rectification module 300, i.e., the synchronous rectification circuit. The rectifier chip U2 has six pins. Its first pin, VO, supplies power to the load through a common-mode inductor LF3. The first terminal of LF3 is electrically connected to the eighth terminal of the secondary side of transformer T1 and the first pin of rectifier chip U2. The second terminal of LF3 is electrically connected to the seventh terminal of the secondary side of transformer T1 through a series MOSFET Q1. The third terminal of LF3 is electrically connected to the V+ terminal (positive terminal of the load power supply), and the fourth terminal is electrically connected to the V- terminal (negative terminal of the load power supply). The drain of MOSFET Q1 is electrically connected to the seventh terminal of the secondary side of transformer T1, and the source of MOSFET Q1 is electrically connected to the common-mode inductor LF3. The second terminal of the inductor LF3 is electrically connected. The gate of the MOSFET Q1 is electrically connected to the fifth pin (GT pin) of the rectifier chip U2. A resistor R9 and a capacitor C8 are connected in parallel between the drain and source of the MOSFET Q1. The resistor R9 and capacitor C8 are connected in series. One end of the resistor R9 is electrically connected to the drain of the MOSFET and the seventh terminal of the secondary side of the transformer T1. The other end of the resistor R9 is electrically connected to one end of the capacitor C8. The other end of the capacitor C8 is electrically connected to the source of the MOSFET Q1. The second pin (GND pin) of the rectifier chip U2 is connected to the signal ground. The third pin (VT pin) of the rectifier chip U2 is connected to the signal ground through a series resistor R23. The fourth pin (VCC pin) of the rectifier chip U2 is connected to the signal ground through a series capacitor C5. The sixth pin (VCC pin) of the rectifier chip U2 is electrically connected to the seventh terminal of the secondary side of the transformer T1 through a series resistor R14.

[0074] It is understandable that the synchronous rectification module 300 is the rectifier circuit on the secondary side of transformer T1, responsible for synchronously rectifying the input voltage to supply power to the load side. Rectifier chip U2 is responsible for performing the aforementioned synchronous rectification of the input voltage, and it controls the conduction of MOSFET Q1 through its fifth pin. This forms a low-resistance path between the drain and source of MOSFET Q1, transmitting the rectified input voltage to common-mode inductor LF3, which then provides energy to the load, effectively charging it. Common-mode inductor LF3 also attenuates common-mode current.

[0075] More specifically, the voltage regulation feedback module 400 in this circuit includes:

[0076] Resistors R10, R16, R21, R13, the light source of optocoupler U3A, capacitor C4, resistor R14, and Zener diode U4 constitute the voltage regulation feedback module 400, i.e., the voltage regulation feedback circuit. The first pin of rectifier chip U2 is grounded through a fourth and fifth branch connected in parallel. The fourth branch consists of resistor R10, the light source of optocoupler U3A, and Zener diode U4 connected in series. One end of resistor R10 is electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary side of transformer T1. The other end of resistor R10 is electrically connected to the input terminal of the light source of optocoupler U3A. The output terminal of LED U4 is electrically connected to the negative terminal of Zener diode U4, and the positive terminal of Zener diode U4 is connected to signal ground. The fifth branch consists of resistor R10 connected in series... The system consists of resistor R16 and resistor R21. One end of resistor R16 is electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary side of transformer T1. The other end of resistor R16 is electrically connected to one end of resistor R21. The other end of resistor R21 is connected to signal ground. Resistor R13 is connected in parallel between the input and output terminals of the light source of optocoupler U3A. The end of resistor R21 away from signal ground is connected to the positive terminal of Zener diode U4. Resistor R16 and resistor R21, and the light source of optocoupler U3A and Zener diode U4 are electrically connected through capacitor C4 and resistor R18 connected in series. One end of capacitor C4 is electrically connected between the light source of optocoupler U3A and Zener diode U4. The other end of capacitor C4 is electrically connected to one end of resistor R18. The other end of resistor R18 is electrically connected between resistor R16 and resistor R21.

[0077] To achieve a regulated output voltage, this circuit needs to be regulated by a voltage feedback module 400. The voltage feedback module 400 performs corresponding voltage regulation and filtering. Stabilizing the voltage is a result of continuous feedback. The voltage feedback module 400 provides a light signal to the user through an LED to remind the user to provide energy to the load.

[0078] The circuit also includes polarized capacitors EC3, EC4, CY1, and CY2. Polarized capacitors EC3 and EC4 are electrically connected to the secondary winding of transformer T1. The positive terminals of polarized capacitors EC3 and EC4 are electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary winding of transformer T1. The negative terminals of polarized capacitors EC3 and EC4 are electrically connected between the second terminal of common-mode inductor LF3 and the seventh terminal of the secondary winding of transformer T1. The negative terminals of polarized capacitors EC3 and EC4 are both connected to signal ground. Capacitors CY1 and CY2 are electrically connected between signal ground and power ground.

[0079] When the back electromotive force present in the primary winding of transformer T1 is released, it is output after being filtered by polarized capacitors EC3 and EC4.

[0080] This utility model embodiment also provides a switching power supply based on the above-described multi-port charging circuit. The working mode of the switching power supply is as described in the multi-port charging circuit above, and will not be repeated here.

[0081] This utility model provides a multi-port charging circuit and switching power supply. Through an electromagnetic compatibility module 100, an absorption module 200, a synchronous rectification module 300, a voltage regulation feedback module 400, a pulse width modulation control module 500, and a transformer T1, it provides a flyback switching power supply. The pulse width modulation control module 500 controls the input voltage to store energy at the edge of the transformer T1. Under the control of the pulse width modulation control module 500, the previously stored back electromotive force is released to the load via the primary side of the transformer T1, providing energy to the load and charging it. This flyback switching power supply can achieve multiple outputs, simultaneously charging multiple electronic devices in the load. Furthermore, the electromagnetic compatibility module 100 effectively suppresses electromagnetic interference. The circuit's electromagnetic interference (EMI) is mitigated, and its anti-EMI capability is improved. The generated EMI is optimized to ensure compliance with relevant electromagnetic compatibility standards. The absorption module 200 controls the discharge voltage released from the primary side within a preset range. The synchronous rectification module 300 and voltage regulation feedback module 400 respectively perform synchronous rectification and voltage regulation feedback of the input voltage. The isolation device samples and feeds back the output voltage, then outputs a feedback signal to the pulse width modulation (PWM) control module 500. This process achieves isolated feedback; when the output voltage exceeds a preset value, it is fed back to the PWM control module 500 through the isolation device, which generates a corresponding protection signal. Therefore, this invention can not only charge multiple electronic devices simultaneously but also provide a stable voltage for them, achieving more stable and safer charging.

[0082] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A multi-port charging circuit, characterized in that: The circuit includes: Electromagnetic compatibility module 100, absorption module 200, synchronous rectification module 300, voltage regulation feedback module 400, pulse width modulation control module 500, and transformer T1; The electromagnetic compatibility module 100, the absorption module 200, and the pulse width modulation control module 500 are located on the primary side of the transformer T1. The synchronous rectification module 300 and the voltage regulation feedback module 400 are located on the secondary side of the transformer T1. The input voltage is electrically connected to the electromagnetic compatibility module 100. The electromagnetic compatibility module 100 is electrically connected to the absorption module 200 through the primary side rectification module. The absorption module 200 is electrically connected to the primary side of the transformer T1. The synchronous rectification module 300 is electrically connected to the secondary side of the transformer T1 and is also connected to the load, providing an output voltage to the load. The voltage regulation feedback module 400 is electrically connected to the synchronous rectification module 300. The pulse width modulation control module 500 is electrically connected to the electromagnetic compatibility module 100 and the primary side of the transformer T1. The pulse width modulation control module 500 is equipped with an isolation device, and the pulse width modulation control module 500 samples and provides feedback from the output voltage through the isolation device.

2. The multi-port charging circuit as described in claim 1, characterized in that: The electromagnetic compatibility module 100 in the circuit includes: Resistors R1, R2, R3, R4, capacitor CX1, and common-mode inductor LF1; Resistors R1 and R2 are connected in series between the live wire and the neutral wire. One end of resistor R1 is electrically connected to the live wire, and the other end of resistor R1 is electrically connected to one end of resistor R2. The other end of resistor R2 is electrically connected to the neutral wire. Resistors R3 and R4 are connected in series between the live wire and the neutral wire. One end of resistor R3 is electrically connected to the live wire, and the other end of resistor R3 is electrically connected to one end of resistor R4. The other end of resistor R4 is electrically connected to the neutral wire. Resistors R1 and R2 are electrically connected to resistors R3 and R4. Capacitor CX1 is connected between the live wire and the neutral wire. Common mode inductor LF1 has four pins. The first pin of common mode inductor LF1 is connected to the live wire, the second pin is connected to the neutral wire, the third pin is electrically connected to the absorption module 200, and the fourth pin is electrically connected to the pulse width modulation control module 500.

3. The multi-port charging circuit as described in claim 2, characterized in that: A varistor NR1, a fuse F1, and a thermistor NTC1 are provided before the front end of the electromagnetic compatibility module 100; Varistor NR1 is connected between the live wire and the neutral wire. Fuse F1 and thermistor NTC1 are connected in series and electrically connected to the live wire. One end of fuse F1 is electrically connected to the live wire, and the other end of fuse F1 is electrically connected to one end of thermistor NTC1. The other end of thermistor NTC1 is electrically connected to the second end of common mode inductor LF1.

4. The multi-port charging circuit as described in claim 2, characterized in that: The pulse width modulation control module 500 in the circuit includes: The main control chip U1, capacitor C2, resistor R15, resistor R12, the receiver of optocoupler U3B, capacitor C7, diode ZD1, capacitor C6, resistor R20, diode ZD2, resistor R19, capacitor C9, resistor R26, capacitor C10, electrolytic capacitor EC2, resistor R25, capacitor C11, diode D4, resistor RS1, resistor RS2, resistor RS3 and resistor RS4; The first pin of the main control chip U1 is electrically connected to the synchronous rectification module 300. The third and fourth pins of the main control chip U1 are electrically connected to the synchronous rectification module 300 through a series capacitor C2. The fifth pin of the main control chip U1 is grounded through a series capacitor C9 and a resistor R26. Resistors RS1, RS2, RS3, and RS4, which are connected in parallel, are electrically connected to the branch formed by the series capacitor C9 and resistor R26. The sixth pin of the main control chip U1 is electrically connected to the primary side of the transformer T1 through a series diode D4 and a resistor R24. A resistor R25 and a capacitor C11 are connected in parallel between the positive and negative terminals of capacitor C4. Resistor R25 and capacitor C11 are connected in series. A capacitor C10 and an electrolytic capacitor EC2 are located between the negative terminal of capacitor C4 and the sixth pin of the main control chip U1. The main control chip U1 is connected in parallel with electrolytic capacitor EC2. The seventh pin of the main control chip U1 is connected to the power supply ground through series resistor R26. The ninth pin of the main control chip U1 is grounded through capacitor C7 and diode ZD1 connected in parallel. The tenth pin of the main control chip U1 is connected to the fourth terminal of the primary side of transformer T1 through resistor R19. The output terminal of the receiver of optocoupler U3B is electrically connected to the ninth pin of the main control chip U1. Resistor R22 is electrically connected to the ninth pin of the main control chip U1. The input terminal of the receiver of optocoupler U3B is connected to static ground and electrically connected to capacitor C7. The receiver of optocoupler U3B and capacitor C7 are connected in series on the ninth pin of the main control chip U1 and in parallel with resistor R22. The eleventh pin of the main control chip U1 is electrically connected to the primary side rectifier module through series resistor R15. The twelfth pin of the main control chip U1 is grounded.

5. The multi-port charging circuit as described in claim 4, characterized in that: The primary-side rectifier module in the circuit includes: Rectifier bridge BD1, diode D1, diode D2, polarized capacitor EC1, and capacitor C3; The first terminal of rectifier bridge BD1 is electrically connected to the third terminal of common-mode inductor LF1. The first terminal of rectifier bridge BD1 is electrically connected to resistor R15 via series diode D1. The anode of diode D1 is electrically connected to the first terminal of rectifier bridge BD1, and the cathode of diode D1 is electrically connected to resistor R15. The second terminal of rectifier bridge BD1 is electrically connected to the fourth terminal of common-mode inductor LF1. The fourth terminal of common-mode inductor LF1 is electrically connected to resistor R15 via series diode C2. The anode of diode C2 is electrically connected to the fourth terminal of common-mode inductor LF1. The cathode of diode C2 is electrically connected to resistor R15. The third terminal of rectifier bridge BD1 is electrically connected to absorption module 200. The fourth terminal of rectifier bridge BD1 is grounded. A polarized capacitor EC1 and a capacitor C3 are connected in parallel between the third and fourth terminals of rectifier bridge BD1. One end of capacitor C3 is connected between the third and fourth terminals of rectifier bridge BD1, and the other end of capacitor C3 is connected to power ground. The positive terminal of polarized capacitor EC1 is connected between the third and fourth terminals of rectifier bridge BD1, and the negative terminal of polarized capacitor EC1 is connected to power ground.

6. The multi-port charging circuit as described in claim 5, characterized in that: The absorption module 200 in the circuit includes: Capacitor C1, resistors R7, R5, R8, R6, R8A, and diode D3; The first terminal of the primary side of transformer T1 is connected to the synchronous rectifier module 300 and the positive terminal of diode D3 through series resistor B1. The negative terminal of diode D3 is electrically connected to the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1 through the first branch, the second branch and the third branch arranged in parallel. The first branch consists of capacitor C1 and resistor R7 connected in series. One end of capacitor C1 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of capacitor C1 is electrically connected to one end of resistor R7, and the other end of resistor R7 is electrically connected to the negative terminal of diode D3. The second branch consists of resistors R5 and R8 connected in series. One end of resistor R5 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of resistor R5 is electrically connected to one end of resistor R8, and the other end of resistor R8 is electrically connected to the negative terminal of diode D3. The third branch consists of resistors R6 and R8A connected in series. One end of resistor R6 is electrically connected between the third terminal of rectifier bridge BD1 and the third terminal of the primary side of transformer T1. The other end of resistor R6 is electrically connected to one end of resistor R8A, and the other end of resistor R8A is electrically connected to the negative terminal of diode D3.

7. The multi-port charging circuit as described in claim 6, characterized in that: The synchronous rectification module 300 in the circuit includes: Rectifier chip U2, resistor R9, capacitor C8, resistor R14, MOSFET Q1, resistor R23, and capacitor C5; The first pin of rectifier chip U2 supplies power to the load through common-mode inductor LF3. The first terminal of common-mode inductor LF3 is electrically connected to the eighth terminal of the secondary side of transformer T1 and the first pin of rectifier chip U2. The second terminal of common-mode inductor LF3 is electrically connected to the seventh terminal of the secondary side of transformer T1 through series MOSFET Q1. The third terminal of common-mode inductor LF3 is electrically connected to the V+ terminal. The fourth terminal of common-mode inductor LF3 is electrically connected to the V- terminal. The drain of MOSFET Q1 is electrically connected to the seventh terminal of the secondary side of transformer T1. The source of MOSFET Q1 is electrically connected to the second terminal of common-mode inductor LF3. The gate of MOSFET Q1 is electrically connected to the fifth pin of rectifier chip U2. A resistor R9 and a capacitor C8 are connected in parallel between the drain and source of MOSFET Q1. The resistor R9 and capacitor C8 are connected in series. One end of the resistor R9 is electrically connected to the drain of the MOSFET and the seventh terminal of the secondary side of transformer T1. The other end of the resistor R9 is electrically connected to one end of the capacitor C8. The other end of the capacitor C8 is electrically connected to the source of MOSFET Q1. The second pin of rectifier chip U2 is connected to signal ground. The third pin of rectifier chip U2 is connected to signal ground through a series resistor R23. The fourth pin of rectifier chip U2 is connected to signal ground through a series capacitor C5. The sixth pin of rectifier chip U2 is electrically connected to the seventh terminal of the secondary side of transformer T1 through a series resistor R14.

8. The multi-port charging circuit as described in claim 7, characterized in that: The voltage regulation feedback module 400 in the circuit includes: Resistors R10, R16, R21, R13, the light source of optocoupler U3A, capacitor C4, resistor R14, and Zener diode U4; The first pin of rectifier chip U2 is grounded through the fourth and fifth branches connected in parallel. The fourth branch consists of a resistor R10, the light source of the optocoupler U3A, and a Zener diode U4 connected in series. One end of the resistor R10 is electrically connected between the first end of the common-mode inductor LF3 and the eighth end of the secondary side of the transformer T1. The other end of the resistor R10 is electrically connected to the input end of the light source of the optocoupler U3A. The output end of the light-emitting diode U4 is electrically connected to the negative terminal of the Zener diode U4, and the positive terminal of the Zener diode U4 is connected to the signal ground. The fifth branch consists of resistors R16 and R21 connected in series. One end of resistor R16 is electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary side of transformer T1. The other end of resistor R16 is electrically connected to one end of resistor R21, and the other end of resistor R21 is connected to signal ground. Resistor R13 is connected in parallel between the input and output terminals of the light source of optocoupler U3A. The end of resistor R21 furthest from signal ground is connected to the positive terminal of Zener diode U4. Resistor R16 and resistor R21, and the light source of optocoupler U3A and Zener diode U4 are electrically connected through capacitor C4 and resistor R18 connected in series. One end of capacitor C4 is electrically connected between the light source of optocoupler U3A and Zener diode U4, and the other end of capacitor C4 is electrically connected to one end of resistor R18. The other end of resistor C4 is electrically connected between resistors R16 and R21.

9. The multi-port charging circuit as described in claim 7, characterized in that: The circuit also includes polarized capacitors EC3, EC4, CY1, and CY2. Polarized capacitors EC3 and EC4 are electrically connected to the secondary winding of transformer T1. The positive terminals of polarized capacitors EC3 and EC4 are electrically connected between the first terminal of common-mode inductor LF3 and the eighth terminal of the secondary winding of transformer T1. The negative terminals of polarized capacitors EC3 and EC4 are electrically connected between the second terminal of common-mode inductor LF3 and the seventh terminal of the secondary winding of transformer T1. The negative terminals of polarized capacitors EC3 and EC4 are both connected to signal ground. Capacitors CY1 and CY2 are electrically connected between signal ground and power ground.

10. A switching power supply, characterized in that: The switching power supply includes: The multi-port charging circuit according to any one of claims 1-9.

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