Constant current constant voltage switching power supply circuit with NFC function

Abstract

The utility model provides a kind of constant-current constant-voltage switching power supply circuit with NFC function, including EMC electromagnetic filter circuit, rectifier filter circuit, PFC boost circuit, LLC resonant circuit, output synchronous rectifier circuit, output control circuit, output voltage feedback circuit and NFC circuit;EMC electromagnetic filter circuit is connected with power input end, one end of rectifier filter circuit is connected with EMC electromagnetic filter circuit, the other end of rectifier filter circuit is connected with one end of PFC boost circuit, the other end of PFC boost circuit is connected with LLC resonant circuit, the other end of LLC resonant circuit is connected with output control circuit by output synchronous rectifier circuit and output voltage feedback circuit, output control circuit is also connected with NFC circuit and power output end, and the output voltage of wireless adjustment output control circuit is controlled by NFC circuit present terminal, NFC circuit is not susceptible to environmental factors, and reliability is high.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, specifically to a constant current and constant voltage switching power supply circuit with NFC function. Background Technology

[0002] Currently, most switching power supplies used for landscape lighting can only output in single or dual channels simultaneously. These power supplies are large, expensive, and complex in structure. When switching between multiple or single channels is required, potentiometers on the circuit must be adjusted to change the output voltage. With traditional dual-channel output, changing the voltage of one channel will also change the voltage of the other, resulting in insufficient voltage output accuracy and potential damage to peripheral equipment. With traditional single-channel output, the voltage application range is limited, which increases the matching difficulty for peripheral equipment used in outdoor landscape lighting. Utility Model Content

[0003] In view of this, the purpose of this utility model is to provide a constant current and constant voltage switching power supply circuit with NFC function. The NFC circuit enables wireless communication between the control terminal and the output control circuit. The output voltage of the output control circuit can be wirelessly adjusted through the control terminal. The NFC circuit is not easily affected by environmental factors, thus ensuring the reliability of the output voltage adjustment.

[0004] To solve the above-mentioned technical problems, the technical solution used in this utility model is as follows:

[0005] The present invention discloses a constant current and constant voltage switching power supply circuit with NFC function, comprising an EMC electromagnetic filter circuit, a rectifier filter circuit, a PFC boost circuit, an LLC resonant circuit, an output synchronous rectifier circuit, an output control circuit, an output voltage feedback circuit, and an NFC circuit. The EMC electromagnetic filter circuit is connected to the power input terminal. One end of the rectifier filter circuit is connected to the EMC electromagnetic filter circuit, and the other end of the rectifier filter circuit is connected to one end of the PFC boost circuit. The other end of the PFC boost circuit is connected to the LLC resonant circuit. The other end of the LLC resonant circuit is connected to the output control circuit through the output synchronous rectifier circuit and the output voltage feedback circuit. The output control circuit is also connected to the NFC circuit and the power output terminal. The NFC circuit is used to receive radio frequency signals to adjust the output voltage of the output control circuit.

[0006] Preferably, the EMC electromagnetic filter circuit includes a fuse F1, a common mode inductor LF1, a common mode inductor LF2, a magnetic core inductor L1, capacitors C1, C2, C3, C4, and C8, a diode D7, and a diode D8; the rectifier filter circuit includes a rectifier bridge BD1 and a capacitor C5.

[0007] One end of fuse F1 is connected to the live wire, and the other end of fuse F1 is connected to one end of common mode inductor LF1. The other end of common mode inductor LF1 is connected to the neutral wire. Capacitor C1 is connected in parallel across the two ends of common mode inductor LF1. Capacitor C2, along with capacitors C3 and C4 connected in series, is connected in parallel between common mode inductor LF1 and common mode inductor LF2. The two ends of capacitor C2, one end of capacitor C3, and one end of capacitor C4 are respectively connected to common mode inductor LF1. The other ends of capacitor C3 and capacitor C4 are grounded through capacitor C8.

[0008] One end of the common-mode inductor LF2 is connected to the positive terminal of diode D7 and one input terminal of rectifier BD1. The other end of the common-mode inductor LF2 is connected to one end of the core inductor L1. The other end of the core inductor L1 is connected to the positive terminal of diode D8 and the other input terminal of rectifier BD1. The negative terminal of diode D7 is connected to the negative terminal of diode D8. The output terminal of rectifier BD1 is connected to the PFC boost circuit through capacitor C5.

[0009] Preferably, the PFC boost circuit includes chip U1, resistors R1, R2, R5, R10, R11, R12, R13, R14, R19, R20, R26, R29, R32, R33, R34, R38, R53, R54, R55, inductors L2A, L2B, and L4, switch S1, capacitors C10, C11, C12, C13, C14, C22, C23, C47, and C48, diodes D3, D9, and D12, transistor Q4, MOSFET Q1A, and MOSFET Q1.

[0010] One end of resistor R1 is connected to the cathodes of diodes D7 and D8. The other end of resistor R1 is connected in series with resistors R2, R14, and R5. One end of resistor R5 is connected to one end of capacitor C11 and one end of resistor R26. The other ends of capacitor C11 and resistor R26 are grounded. One end of resistor R5, one end of capacitor C11, and one end of resistor R26 are also connected to the LNS pin of chip U1.

[0011] The two output terminals of the rectifier BD1 are connected through capacitor C5. Capacitor C5 is also grounded through resistor R32. Resistor E33 is connected in parallel with resistor R32. Capacitor C5 is also grounded through resistor R29 and capacitor C12 connected in series. Resistor R32 is connected in parallel with resistor R29 and capacitor C12 connected in series. One end of resistor R29 and one end of capacitor C12 are connected to the CS pin of chip U1.

[0012] One output terminal of rectifier BD1 is also connected to one end of inductor L2A. The other end of inductor L2A is connected to ground in series with inductor L4, diode D9, and capacitor C23. Diode D9 is also connected to LLC resonant circuit. Diode D9 is also connected in series with resistors R19, R20, and R45. One end of resistor R45 is grounded through parallel resistors R34, R38, and capacitor C22. Resistor R45 and capacitor C22 are also connected to the FBB pin of chip U1. Resistors R19, R20, and R45 are connected in parallel with capacitor C23.

[0013] The capacitors C10, C13, C14 and C23 are connected in parallel; the inductor L2B and inductor L2A are connected in parallel; and the diode D12 is connected in parallel with inductor L2A, inductor L4 and diode D9.

[0014] Inductor L2A is also connected to the drain of MOSFET Q1A, one end of resistor R10, and one end of capacitor C48. The other end of resistor R10 is connected to the HV pin of chip U1. The other end of capacitor C48 is connected to the source of MOSFET Q1A through resistor R55. The source of MOSFET Q1A is grounded. Resistor R54 and capacitor C47 are connected in parallel with resistor R55.

[0015] The gate of MOSFET Q1A is connected to one end of resistor R12. The other end of resistor R12 is connected to the emitter of transistor Q4, one end of resistor R13, and one end of resistor R11. The collector of transistor Q4 is connected to the source of MOSFET Q1A. The base of transistor Q4 is connected to the anode of diode D3 and resistor R53. The cathode of diode D3 is connected to resistor R10. Resistor R53 is connected to the GATEB pin of chip U1. The other end of resistor R13 is grounded. The other end of R11 is connected to the gate of MOSFET Q1. The source of MOSFET Q1 is grounded. The drain of MOSFET Q1 is connected to inductor L2A.

[0016] Preferably, the LLC resonant circuit includes resistors R3, R4, R7, R15, R16, R17, R22, R23, R24, R25, R44, and R37; capacitors C6, C7, R8, C17, C18, C18, C30, C31, C32, C33, C35, and C49; inductors L3A and L3B; diodes D1, D2, D4, and D5; Zener diode ZD1; transistor Q5; MOSFET Q2 and Q3; diode D6; and transformer T2.

[0017] One end of resistor R23 is connected to the GATEH pin of chip U1, the other end of resistor R23 is connected to one end of resistor R22, the other end of resistor R22 is connected to one end of resistor R16 and the gate of MOSFET Q2, and diode D4 is connected in parallel with resistor R22.

[0018] The drain of MOSFET Q2 is connected to the cathode of diode D9, and the source of MOSFET Q2 is connected to the drain of MOSFET Q3. The source of MOSFET Q2 is connected to the ISEN pin of chip U1 through capacitor C31. The gate of MOSFET Q3 is connected in series with resistors R25 and R24 and the GATEL pin of chip U1. The gate of MOSFET Q3 is also connected to one end of resistor R17, and the other end of resistor R17 is connected to capacitor C31. The source of MOSFET Q2 is also connected to one end of inductor L3A and capacitor C4. One end of capacitor C49 is connected to the source of MOSFET Q3; the T2D winding of transformer T2 is connected to the other end of inductor L3A and one end of capacitors C32 and C33; the other end of capacitor C32 is connected to one end of resistor R37, one end of resistor R9 and one end of resistor R8; the other end of resistor R8 is grounded and the other ends of resistor R8, resistor R9 and capacitor C33 are all connected to capacitor C31; the other end of resistor R37 is connected to the ISEN pin of chip U1.

[0019] Capacitor C30 is also connected to the negative terminal of diode D2. The positive terminal of diode D2 is connected to the HS pin of chip U1 and is also connected to the negative terminal of diode D1, one end of capacitor C18, and one end of capacitor C7. The diode D1 is connected to the emitter of transistor Q5. The base of transistor Q5 is connected to the negative terminal of Zener diode ZD1 and one end of resistor R4. The collector of transistor Q5 is connected to the negative terminal of diode D6, the other end of resistor R4, and one end of capacitor C35. Transformer T2 is connected to the positive terminal of diode D6, the other end of capacitor C35, the other end of Zener diode ZD1, the other end of capacitor C7, and the other end of capacitor C18, and is connected to the VSEN pin of chip U1 through capacitor C6. Resistor R15 is connected in parallel with capacitor C6, and resistor R44 is connected between resistor R4 and capacitor C6. Windings T2A, T2B, and T2C of transformer T2 are all connected to the output synchronous rectifier circuit.

[0020] Preferably, the output synchronous rectification circuit includes capacitors C9, C20, C21, C24, C25, C26, C27, C28, C29, C34, C36, C37, C38, C39, C40, C41, and C45; resistors R31, R47, R46, R63, R64, R65, R66, R69, R70, R71, R72, R73, and RS1; diodes D11 and D10; Zener diode ZD2; MOSFETs Q8 and Q9; transistor Q10; and chip U3.

[0021] The winding T2A of transformer T2 is connected to the positive terminal of diode D10, one end of capacitor C29, and the rectification terminal of Zener diode ZD2. The negative terminal of diode D10 is connected to the other end of capacitor C29 and to an external power supply. The VO+ terminal of transformer T2 is also connected to one end of resistor R46 and the collector of transistor Q10. The other end of resistor R46 is connected to the base of transistor Q10. The emitter of transistor Q10 is connected to the positive terminal of diode D11. The negative terminal of diode D1 is connected to an external power supply.

[0022] The VO+ terminal of transformer T2 is connected in series with resistors R47 and RS1 and then grounded. Capacitor C45 is connected in parallel with the series resistors R47 and RS1. Capacitors C24, C23, C26, C27, C28, and resistor R31 are connected in parallel with resistor R7. Resistors R47 and RS1 are also connected to the winding T2A of transformer T2.

[0023] The winding T2A of the transformer T2 is also connected to one end of capacitor C38, the source of MOSFET Q8, the gate of MOSFET Q8, the second pin of chip U3, the fifth pin of chip U3, and one end of resistor R69. The other end of resistor R69 is connected to the third pin of chip U3. Capacitor C34 is connected in parallel with resistor R69. The other end of capacitor C38 is connected to the sixth pin of chip U3 through resistors R7 and R63 connected in series. Resistors R70 and R71 are connected in parallel. The drain of MOSFET Q8 is also connected to the winding T2B of transformer T2 and resistor R7. The base of MOSFET Q8 is also connected to the eighth pin of chip U3 through resistor R65.

[0024] The winding T2A of the transformer T2 is also connected to one end of the capacitor C39, the source of the MOSFET Q9, and the gate of the MOSFET Q9. The gate of the MOSFET Q9 is also connected to the gate of the MOSFET Q8 and one end of the resistor R66. The other end of the resistor R66 is connected to the first pin of the chip U3. The other end of the capacitor C39 is connected to the fourth pin of the chip U3 through the series resistors R73 and R64. The resistors R72 and R73 are connected in parallel. The drain of the MOSFET Q9 is also connected to the winding T2C of the transformer T2 and the resistor R73.

[0025] The fifth pin of chip U3 is also connected to the seventh pin of chip U3 through resistor C36. The capacitor C37 is connected in parallel with capacitor C36. The seventh pin of chip U3 is also connected to an external power supply.

[0026] Preferably, the output control circuit includes capacitors CX1, CX2, CX3, CX4, CX5, CX13, CX14, CX15, CX16, CX17, and CX18; resistors RX1, RX2, RX3, RX4, RX5, RX6, RX20, RX21, RX22, RX23, RX24, RX25, RX26, RX27, and RX28; a thermistor NX1; chips UX1, UX2, UX4, and UX5; a light-emitting diode LD1; and a Zener diode UX2.

[0027] The first and third pins of chip UX1 are connected to the two ends of capacitor CX1. The first pin of chip UX1 is grounded, the second pin of chip UX1 is connected to an external power supply, capacitor CX2 is connected in parallel with capacitor CX1, and the third pin of chip UX1 is also connected to the VDD pin of chip UX4.

[0028] One end of the resistor RX3 is connected to the winding T2A of the transformer T2, and the other end of the resistor RX3 is connected to the VCS terminal of the chip UX4 through the series resistors RX4 and RX24. The capacitor CX4 is connected in parallel with the resistor RX4.

[0029] The first pin of the chip UX5 is connected to resistors RX4 and RX24. The second and third pins of the chip UX5 are grounded. The third pin of the chip UX5 is also connected to one end of capacitor CX18 and one end of capacitor CX15. The other end of capacitor CX18 is connected to resistor RX3. The other end of capacitor CX15 is connected to the VCS terminal of the chip UX4.

[0030] One end of the resistor RX26 is connected to the LLC resonant circuit, and the other end of the resistor RX26 is connected to one end of the resistor RX27 and the VOS pin of the chip UX4. The other end of the resistor RX27 is grounded, and the capacitor CX16 is connected in parallel with the resistor RX27.

[0031] One end of the thermistor NX1 is connected to the fifth pin of the chip UX5, and the other end of the thermistor NX1 is connected to the VTS pin of the chip UX4 and one end of the resistor RX28. The other end of the resistor RX28 is grounded. The resistor RX25 is connected in parallel with the thermistor NX1, and the capacitor CX17 is connected in parallel with the resistor RX28.

[0032] One end of resistor RX15 is connected to an external power supply, the other end of resistor RX15 is connected to the VAS pin of chip UX4 and one end of resistor RX6, the other end of resistor RX6 is grounded, and capacitor CX5 is connected in parallel with resistor RX6.

[0033] One end of resistor RX1 is connected to the LEDG pin of chip UX4, and the other end of resistor RX1 is connected to the positive terminal of light-emitting diode LD1, while the negative terminal of light-emitting diode LD1 is grounded; one end of resistor RX2 is connected to the VDD pin of chip UX4, and the other end of resistor RX2 is connected to the first pin of chip UX2, the second pin of chip UX2 is grounded, the third pin of chip UX2 is connected to the ninth pin of chip UX4, and capacitor CX3 is connected in parallel with chip UX2.

[0034] Resistor RX20 is connected to the VDD pin of chip UX4. Resistor RX21 and resistor RX20 are also connected to the PWMA pin of chip UX4. Resistor RX21 is grounded through capacitor CX13. Resistor RX21 and capacitor CX13 are also connected to the power output terminal.

[0035] Resistor RX22 is connected to the VDD pin of chip UX4. Resistor RX23 and resistor RX22 are also connected to the PWMB pin of chip UX4. Resistor RX23 is grounded through capacitor CX14. Resistor RX23 and capacitor CX14 are also connected to the power output terminal.

[0036] The NFC circuit includes chip U4; the fifth pin of chip U4 is connected to the SB5 pin of chip UX4, the sixth pin of chip U4 is connected to the SB2 pin of UX4, and the eighth pin of chip U4 is connected to the SB3 pin of UX4.

[0037] Preferably, the NFC circuit further includes an RF transformer T1 and a capacitor C16; the second pin and the third pin of the chip U4 are connected to the RF transformer T1; the capacitor C16 is connected in parallel with the RF transformer T1.

[0038] Preferably, the output voltage feedback circuit includes optocoupler U2, resistors RX8 and RX9, diodes DX1B and DX1A, resistors RX10, RX11, RX12, RX13, RX14, RX15, RS16, RX17, RS18, RX19, and RX29, capacitors CX6, CX8, CS9, CX10, CX11, and CX12, and operational amplifier UX6.

[0039] One end of resistor RX29 is connected to the VDD terminal of chip UX4, and the other end of resistor RX29 is grounded through capacitor CX6. The other end of resistor RX29 is connected to the VDA pin of chip UX5, the eighth pin of operational amplifier UX6, and one end of resistor RX8. The other end of resistor RX8 is connected to one end of resistor RX9, and the other end of resistor RX9 is connected to the anode of diode DX1B and the anode of diode DX1A.

[0040] The negative terminal of diode DX1B is connected to the seventh pin of the operational amplifier. The seventh pin of the operational amplifier UX6 is also connected to the sixth pin of the operational amplifier UX6 through resistor RX10 and capacitor CX8. The sixth pin of the operational amplifier UX6 is connected to one end of resistor RX17, one end of capacitor CX12, and one end of resistor RX19. The other end of capacitor CX12 is connected to one end of resistor RX18. The other ends of resistors RX17 and RX18 are connected to the VO+ terminal of transformer T2. The other end of resistor RX19 is grounded. The fifth pin of the operational amplifier UX6 is grounded through resistor RX15. Capacitor CX11 is connected in parallel with resistor RX15. The fifth pin of the operational amplifier UX6 is also connected to resistor RX21 and capacitor CX13 in series through resistor RX14.

[0041] The positive terminal of diode DX1A is connected to the first pin of operational amplifier UX6. The first pin of operational amplifier UX6 is connected to the second pin of operational amplifier UX6 through resistor RX11 and capacitor CX9. The second pin of operational amplifier UX6 is grounded through resistor RX12. The third pin of operational amplifier UX6 is connected to resistor RX22 and capacitor CX14 through a series resistor RX16.

[0042] The fourth pin of the operational amplifier UX6 is connected to the winding T2A of the transformer T2 through a series capacitor CX10 and a resistor RX13; one end of the optocoupler U2 is connected to both ends of the resistor RX8, and the other end of the optocoupler U2 is connected to both ends of the capacitor C17; the capacitor CX7 is connected in parallel with the resistor RX9.

[0043] Preferably, it also includes a surge protection circuit, which includes an impedance Z1, a thermistor N1, and a relay K1.

[0044] The impedance Z1 and capacitor C2 are connected in parallel across the common-mode inductor LF1. The relay K1 is connected between the other end of the common-mode inductor LF2 and one end of the magnetic core inductor L1. The relay K1 is also connected to one input terminal of the rectifier BD1 in the EMC electromagnetic filter circuit. The relay K1 is also connected to the LLC resonant circuit through resistor R7.

[0045] Compared with existing technologies, the advantages of the constant current and constant voltage switching power supply circuit with NFC function described in this utility model are mainly reflected in:

[0046] An NFC circuit is used to achieve wireless control of the output voltage. Based on NFC near-field communication, the control terminal communicates with the NFC circuit within a certain range. The NFC circuit is connected to the output control circuit. Chip U4 receives the radio frequency signal from the control terminal and outputs an adjustment signal to chip UX4. Chip U4 adjusts the duty cycle of the PWM according to the adjustment signal. When the duty cycle increases, the output voltage of UX4 increases; when the duty cycle decreases, the output voltage of UX4 decreases. Simultaneously, the NFC circuit is a digital circuit, which is less affected by environmental factors, ensuring the reliability of the output voltage adjustment. An RF transformer is included in the NFC circuit to extend the communication distance of chip U4.

[0047] The GATEL pin of chip U1 is connected to capacitor C33. Chip U1 detects the voltage level on capacitor C33. When the voltage of capacitor C33 exceeds the rated value, chip U1 disconnects from MOSFET Q2, MOSFET Q3, and transistor Q5, and stops supplying power to transformer T2, thereby realizing overcurrent protection and overpower protection.

[0048] This invention enables wireless communication between the control terminal and the output control circuit via an NFC circuit; the output voltage of the output control circuit can be wirelessly adjusted through the control terminal, achieving compatibility with devices of different voltages. Attached Figure Description

[0049] The above and other objects, features, and advantages of this invention will become clearer through a more detailed description of the preferred embodiments shown in the accompanying drawings. The same reference numerals indicate the same parts throughout the drawings, and the drawings are not intentionally drawn to scale with actual dimensions; the focus is on illustrating the gist of this invention.

[0050] Figure 1 This is a schematic diagram of the present invention.

[0051] Figure 2This is a schematic diagram of the EMC electromagnetic filter circuit, surge protection circuit, rectifier filter circuit, PFC boost circuit, LLC resonant circuit, and output synchronous rectifier circuit in this utility model.

[0052] Figure 3 This is a schematic diagram of the output control circuit, output voltage feedback circuit, and NFC circuit in this utility model. Detailed Implementation

[0053] The technical solution of this utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand this utility model and implement it. However, the embodiments are not intended to limit this utility model. In this embodiment, it should be understood that the terms "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this utility model.

[0054] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to and integrated with the other element, or there may be an intervening element present. The terms "mounted," "one end," "the other end," and similar expressions used in this invention are for illustrative purposes only.

[0055] like Figure 1-3 As shown, a constant current and constant voltage switching power supply circuit with NFC function includes an EMC electromagnetic filter circuit, a rectifier filter circuit, a PFC boost circuit, an LLC resonant circuit, an output synchronous rectifier circuit, an output control circuit, an output voltage feedback circuit, and an NFC circuit. The EMC electromagnetic filter circuit is connected to the power input terminal. One end of the rectifier filter circuit is connected to the EMC electromagnetic filter circuit, and the other end of the rectifier filter circuit is connected to one end of the PFC boost circuit. The other end of the PFC boost circuit is connected to the LLC resonant circuit. The other end of the LLC resonant circuit is connected to the output control circuit through the output synchronous rectifier circuit and the output voltage feedback circuit. The output control circuit is also connected to the NFC circuit and the power output terminal. The NFC circuit is used to receive radio frequency signals to adjust the output voltage of the output control circuit.

[0056] The EMC electromagnetic filter circuit includes a fuse F1, common mode inductors LF1 and LF2, a magnetic core inductor L1, capacitors C1, C2, C3, C4, and C8, and diodes D7 and D8; the rectifier filter circuit includes a rectifier bridge BD1 and capacitor C5.

[0057] One end of fuse F1 is connected to the live wire, and the other end of fuse F1 is connected to one end of common mode inductor LF1. The other end of common mode inductor LF1 is connected to the neutral wire. Capacitor C1 is connected in parallel across the two ends of common mode inductor LF1. Capacitor C2, along with capacitors C3 and C4 connected in series, is connected in parallel between common mode inductor LF1 and common mode inductor LF2. The two ends of capacitor C2, one end of capacitor C3, and one end of capacitor C4 are respectively connected to common mode inductor LF1. The other ends of capacitor C3 and capacitor C4 are grounded through capacitor C8.

[0058] One end of the common-mode inductor LF2 is connected to the positive terminal of diode D7 and one input terminal of rectifier BD1. The other end of the common-mode inductor LF2 is connected to one end of the core inductor L1. The other end of the core inductor L1 is connected to the positive terminal of diode D8 and the other input terminal of rectifier BD1. The negative terminal of diode D7 is connected to the negative terminal of diode D8. The output terminal of rectifier BD1 is connected to the PFC boost circuit through capacitor C5.

[0059] The PFC boost circuit includes chip U1, resistors R1, R2, R5, R10, R11, R12, R13, R14, R19, R20, R26, R29, R32, R33, R34, R38, R53, R54, R55, inductors L2A, L2B, and L4, switch S1, capacitors C10, C11, C12, C13, C14, C22, C23, C47, and C48, diodes D3, D9, and D12, transistor Q4, MOSFET Q1A, and MOSFET Q1. In this embodiment, chip U1 is model SY5055AHXP.

[0060] One end of resistor R1 is connected to the cathodes of diodes D7 and D8. The other end of resistor R1 is connected in series with resistors R2, R14, and R5. One end of resistor R5 is connected to one end of capacitor C11 and one end of resistor R26. The other ends of capacitor C11 and resistor R26 are grounded. One end of resistor R5, one end of capacitor C11, and one end of resistor R26 are also connected to the LNS pin of chip U1.

[0061] The two output terminals of the rectifier BD1 are connected through capacitor C5. Capacitor C5 is also grounded through resistor R32. Resistor E33 is connected in parallel with resistor R32. Capacitor C5 is also grounded through resistor R29 and capacitor C12 connected in series. Resistor R32 is connected in parallel with resistor R29 and capacitor C12 connected in series. One end of resistor R29 and one end of capacitor C12 are connected to the CS pin of chip U1.

[0062] One output terminal of rectifier BD1 is also connected to one end of inductor L2A. The other end of inductor L2A is connected to ground in series with inductor L4, diode D9, and capacitor C23. Diode D9 is also connected to LLC resonant circuit. Diode D9 is also connected in series with resistors R19, R20, and R45. One end of resistor R45 is grounded through parallel resistors R34, R38, and capacitor C22. Resistor R45 and capacitor C22 are also connected to the FBB pin of chip U1. Resistors R19, R20, and R45 are connected in parallel with capacitor C23.

[0063] The capacitors C10, C13, C14 and C23 are connected in parallel; the inductor L2B and inductor L2A are connected in parallel; and the diode D12 is connected in parallel with inductor L2A, inductor L4 and diode D9.

[0064] Inductor L2A is also connected to the drain of MOSFET Q1A, one end of resistor R10, and one end of capacitor C48. The other end of resistor R10 is connected to the HV pin of chip U1. The other end of capacitor C48 is connected to the source of MOSFET Q1A through resistor R55. The source of MOSFET Q1A is grounded. Resistor R54 and capacitor C47 are connected in parallel with resistor R55.

[0065] The gate of MOSFET Q1A is connected to one end of resistor R12. The other end of resistor R12 is connected to the emitter of transistor Q4, one end of resistor R13, and one end of resistor R11. The collector of transistor Q4 is connected to the source of MOSFET Q1A. The base of transistor Q4 is connected to the anode of diode D3 and resistor R53. The cathode of diode D3 is connected to resistor R10. Resistor R53 is connected to the GATEB pin of chip U1. The other end of resistor R13 is grounded. The other end of R11 is connected to the gate of MOSFET Q1. The source of MOSFET Q1 is grounded. The drain of MOSFET Q1 is connected to inductor L2A.

[0066] The LLC resonant circuit includes resistors R3, R4, R7, R15, R16, R17, R22, R23, R24, R25, R44, and R37; capacitors C6, C7, R8, C17, C18, C18, C30, C31, C32, C33, C35, and C49; inductors L3A and L3B; diodes D1, D2, D4, and D5; Zener diode ZD1; transistor Q5; MOSFET Q2 and Q3; diode D6; and transformer T2.

[0067] One end of resistor R23 is connected to the GATEH pin of chip U1, the other end of resistor R23 is connected to one end of resistor R22, the other end of resistor R22 is connected to one end of resistor R16 and the gate of MOSFET Q2, and diode D4 is connected in parallel with resistor R22.

[0068] The drain of MOSFET Q2 is connected to the cathode of diode D9, and the source of MOSFET Q2 is connected to the drain of MOSFET Q3. The source of MOSFET Q2 is connected to the ISEN pin of chip U1 through capacitor C31. The gate of MOSFET Q3 is connected in series with resistors R25 and R24 and the GATEL pin of chip U1. The gate of MOSFET Q3 is also connected to one end of resistor R17, and the other end of resistor R17 is connected to capacitor C31. The source of MOSFET Q2 is also connected to one end of inductor L3A and capacitor C4. One end of capacitor C49 is connected to the source of MOSFET Q3; the T2D winding of transformer T2 is connected to the other end of inductor L3A and one end of capacitors C32 and C33; the other end of capacitor C32 is connected to one end of resistor R37, one end of resistor R9 and one end of resistor R8; the other end of resistor R8 is grounded and the other ends of resistor R8, resistor R9 and capacitor C33 are all connected to capacitor C31; the other end of resistor R37 is connected to the ISEN pin of chip U1.

[0069] Capacitor C30 is also connected to the negative terminal of diode D2. The positive terminal of diode D2 is connected to the HS pin of chip U1 and is also connected to the negative terminal of diode D1, one end of capacitor C18, and one end of capacitor C7. The diode D1 is connected to the emitter of transistor Q5. The base of transistor Q5 is connected to the negative terminal of Zener diode ZD1 and one end of resistor R4. The collector of transistor Q5 is connected to the negative terminal of diode D6, the other end of resistor R4, and one end of capacitor C35. Transformer T2 is connected to the positive terminal of diode D6, the other end of capacitor C35, the other end of Zener diode ZD1, the other end of capacitor C7, and the other end of capacitor C18, and is connected to the VSEN pin of chip U1 through capacitor C6. Resistor R15 is connected in parallel with capacitor C6, and resistor R44 is connected between resistor R4 and capacitor C6. Windings T2A, T2B, and T2C of transformer T2 are all connected to the output synchronous rectifier circuit.

[0070] The output synchronous rectification circuit includes capacitors C9, C20, C21, C24, C25, C26, C27, C28, C29, C34, C36, C37, C38, C39, C40, C41, and C45; resistors R31, R47, R46, R63, R64, R65, R66, R69, R70, R71, R72, R73, and RS1; diodes D11 and D10; Zener diode ZD2; MOSFETs Q8 and Q9; transistor Q10; and chip U3. In this embodiment, chip U3 is model MP6924AGS.

[0071] The winding T2A of transformer T2 is connected to the positive terminal of diode D10, one end of capacitor C29, and the rectification terminal of Zener diode ZD2. The negative terminal of diode D10 is connected to the other end of capacitor C29 and to an external power supply. The VO+ terminal of transformer T2 is also connected to one end of resistor R46 and the collector of transistor Q10. The other end of resistor R46 is connected to the base of transistor Q10. The emitter of transistor Q10 is connected to the positive terminal of diode D11. The negative terminal of diode D1 is connected to an external power supply.

[0072] The VO+ terminal of transformer T2 is connected in series with resistors R47 and RS1 and then grounded. Capacitor C45 is connected in parallel with the series resistors R47 and RS1. Capacitors C24, C23, C26, C27, C28, and resistor R31 are connected in parallel with resistor R7. Resistors R47 and RS1 are also connected to the winding T2A of transformer T2.

[0073] The winding T2A of the transformer T2 is also connected to one end of capacitor C38, the source of MOSFET Q8, the gate of MOSFET Q8, the second pin of chip U3, the fifth pin of chip U3, and one end of resistor R69. The other end of resistor R69 is connected to the third pin of chip U3. Capacitor C34 is connected in parallel with resistor R69. The other end of capacitor C38 is connected to the sixth pin of chip U3 through resistors R7 and R63 connected in series. Resistors R70 and R71 are connected in parallel. The drain of MOSFET Q8 is also connected to the winding T2B of transformer T2 and resistor R7. The base of MOSFET Q8 is also connected to the eighth pin of chip U3 through resistor R65.

[0074] The winding T2A of the transformer T2 is also connected to one end of the capacitor C39, the source of the MOSFET Q9, and the gate of the MOSFET Q9. The gate of the MOSFET Q9 is also connected to the gate of the MOSFET Q8 and one end of the resistor R66. The other end of the resistor R66 is connected to the first pin of the chip U3. The other end of the capacitor C39 is connected to the fourth pin of the chip U3 through the series resistors R73 and R64. The resistors R72 and R73 are connected in parallel. The drain of the MOSFET Q9 is also connected to the winding T2C of the transformer T2 and the resistor R73.

[0075] The fifth pin of chip U3 is also connected to the seventh pin of chip U3 through resistor C36. The capacitor C37 is connected in parallel with capacitor C36. The seventh pin of chip U3 is also connected to an external power supply.

[0076] The output control circuit includes capacitors CX1, CX2, CX3, CX4, CX5, CX13, CX14, CX15, CX16, CX17, and CX18; resistors RX1, RX2, RX3, RX4, RX5, RX6, RX20, RX21, RX22, RX23, RX24, RX25, RX26, RX27, and RX28; a thermistor NX1; chips UX1, UX2, UX4, and UX5; an LED LD1; and a Zener diode UX2. In this embodiment, chip UX4 is model STC8H1K08T-33I-TSSOP20.

[0077] The first and third pins of chip UX1 are connected to the two ends of capacitor CX1. The first pin of chip UX1 is grounded, the second pin of chip UX1 is connected to an external power supply, capacitor CX2 is connected in parallel with capacitor CX1, and the third pin of chip UX1 is also connected to the VDD pin of chip UX4.

[0078] One end of the resistor RX3 is connected to the winding T2A of the transformer T2, and the other end of the resistor RX3 is connected to the VCS terminal of the chip UX4 through the series resistors RX4 and RX24. The capacitor CX4 is connected in parallel with the resistor RX4.

[0079] The first pin of the chip UX5 is connected to resistors RX4 and RX24. The second and third pins of the chip UX5 are grounded. The third pin of the chip UX5 is also connected to one end of capacitor CX18 and one end of capacitor CX15. The other end of capacitor CX18 is connected to resistor RX3. The other end of capacitor CX15 is connected to the VCS terminal of the chip UX4.

[0080] One end of the resistor RX26 is connected to the LLC resonant circuit, and the other end of the resistor RX26 is connected to one end of the resistor RX27 and the VOS pin of the chip UX4. The other end of the resistor RX27 is grounded, and the capacitor CX16 is connected in parallel with the resistor RX27.

[0081] One end of the thermistor NX1 is connected to the fifth pin of the chip UX5, and the other end of the thermistor NX1 is connected to the VTS pin of the chip UX4 and one end of the resistor RX28. The other end of the resistor RX28 is grounded. The resistor RX25 is connected in parallel with the thermistor NX1, and the capacitor CX17 is connected in parallel with the resistor RX28.

[0082] One end of resistor RX15 is connected to an external power supply, the other end of resistor RX15 is connected to the VAS pin of chip UX4 and one end of resistor RX6, the other end of resistor RX6 is grounded, and capacitor CX5 is connected in parallel with resistor RX6.

[0083] One end of resistor RX1 is connected to the LEDG pin of chip UX4, and the other end of resistor RX1 is connected to the positive terminal of light-emitting diode LD1, while the negative terminal of light-emitting diode LD1 is grounded; one end of resistor RX2 is connected to the VDD pin of chip UX4, and the other end of resistor RX2 is connected to the first pin of chip UX2, the second pin of chip UX2 is grounded, the third pin of chip UX2 is connected to the ninth pin of chip UX4, and capacitor CX3 is connected in parallel with chip UX2.

[0084] Resistor RX20 is connected to the VDD pin of chip UX4. Resistor RX21 and resistor RX20 are also connected to the PWMA pin of chip UX4. Resistor RX21 is grounded through capacitor CX13. Resistor RX21 and capacitor CX13 are also connected to the power output terminal.

[0085] Resistor RX22 is connected to the VDD pin of chip UX4. Resistor RX23 and resistor RX22 are also connected to the PWMB pin of chip UX4. Resistor RX23 is grounded through capacitor CX14. Resistor RX23 and capacitor CX14 are also connected to the power output terminal.

[0086] The NFC circuit includes chip U4, RF transformer T1, and capacitor C16. Pin 5 of chip U4 is connected to pin SB5 of chip UX4, pin 6 of chip U4 is connected to pin SB2 of chip UX4, and pin 8 of chip U4 is connected to pin SB3 of chip UX4. Pins 2 and 3 of chip U4 are connected to RF transformer T1. Capacitor C16 is connected in parallel with RF transformer T1. In this embodiment, chip U4 is model ST25DV02K-W1.

[0087] The output voltage feedback circuit includes optocoupler U2, resistors RX8 and RX9, diodes DX1B and DX1A, resistors RX10, RX11, RX12, RX13, RX14, RX15, RS16, RX17, RS18, RX19, RX29, capacitors CX6, CX8, CS9, CX10, CX11, CX12, and operational amplifier UX6.

[0088] One end of resistor RX29 is connected to the VDD terminal of chip UX4, and the other end of resistor RX29 is grounded through capacitor CX6. The other end of resistor RX29 is connected to the VDA pin of chip UX5, the eighth pin of operational amplifier UX6, and one end of resistor RX8. The other end of resistor RX8 is connected to one end of resistor RX9, and the other end of resistor RX9 is connected to the anode of diode DX1B and the anode of diode DX1A.

[0089] The negative terminal of diode DX1B is connected to the seventh pin of the operational amplifier. The seventh pin of the operational amplifier UX6 is also connected to the sixth pin of the operational amplifier UX6 through resistor RX10 and capacitor CX8. The sixth pin of the operational amplifier UX6 is connected to one end of resistor RX17, one end of capacitor CX12, and one end of resistor RX19. The other end of capacitor CX12 is connected to one end of resistor RX18. The other ends of resistors RX17 and RX18 are connected to the VO+ terminal of transformer T2. The other end of resistor RX19 is grounded. The fifth pin of the operational amplifier UX6 is grounded through resistor RX15. Capacitor CX11 is connected in parallel with resistor RX15. The fifth pin of the operational amplifier UX6 is also connected to resistor RX21 and capacitor CX13 in series through resistor RX14.

[0090] The positive terminal of diode DX1A is connected to the first pin of operational amplifier UX6. The first pin of operational amplifier UX6 is connected to the second pin of operational amplifier UX6 through resistor RX11 and capacitor CX9. The second pin of operational amplifier UX6 is grounded through resistor RX12. The third pin of operational amplifier UX6 is connected to resistor RX22 and capacitor CX14 through a series resistor RX16.

[0091] The fourth pin of the operational amplifier UX6 is connected to the winding T2A of the transformer T2 through a series capacitor CX10 and a resistor RX13; one end of the optocoupler U2 is connected to both ends of the resistor RX8, and the other end of the optocoupler U2 is connected to both ends of the capacitor C17; the capacitor CX7 is connected in parallel with the resistor RX9.

[0092] In a preferred embodiment, a surge protection circuit is further included, comprising an impedance Z1, a thermistor N1, and a relay K1.

[0093] The impedance Z1 and capacitor C2 are connected in parallel across the common-mode inductor LF1. The relay K1 is connected between the other end of the common-mode inductor LF2 and one end of the magnetic core inductor L1. The relay K1 is also connected to one input terminal of the rectifier BD1 in the EMC electromagnetic filter circuit. The relay K1 is also connected to the LLC resonant circuit through resistor R7.

[0094] In this embodiment, chip UX4 is connected to chip UX1, diode DX1A, diode DX1B, capacitor CX9, resistor RX13, resistor RX16, capacitor CX10, capacitor CX11, resistor RX15, resistor RX14, capacitor CX13, resistor RX21, resistor RX29, resistor RX22, resistor RX23, resistor RX17, capacitor CX12, resistor RX19, capacitor CX5, resistor RX6, capacitor CX16, resistor RX27, capacitor CX1, capacitor CX14, resistor RX18, resistor RX5, resistor RX3, resistor RX2, resistor RX4, and capacitor CX4.

[0095] An NFC circuit is used to achieve wireless control of the output voltage. Based on NFC near-field communication, the control terminal communicates with the NFC circuit within a certain range. The NFC circuit is connected to the output control circuit. Chip U4 receives the radio frequency signal from the control terminal and outputs an adjustment signal to chip UX4. Chip U4 adjusts the duty cycle of the PWM according to the adjustment signal. When the duty cycle increases, the output voltage of UX4 increases; when the duty cycle decreases, the output voltage of UX4 decreases. Simultaneously, the NFC circuit is a digital circuit, which is less affected by environmental factors, ensuring the reliability of the output voltage adjustment. An RF transformer is included in the NFC circuit to extend the communication distance of chip U4.

[0096] The control terminal can be a mobile phone or an NFC reader / writer; the control terminal inputs a voltage value to the chip UX4, and the chip U4 reads the voltage value received by the chip UX4; the chip U4 maps the current voltage value to the duty cycle of the PWM; then the chip U4 outputs a PWM square wave corresponding to the duty cycle, and the PWM square wave is filtered by the resistor RX21 and the capacitor CX13 and then output to the power output terminal.

[0097] Meanwhile, the GATEL pin of chip U1 is connected to capacitor C33. Chip U1 detects the voltage level on capacitor C33. When the voltage of capacitor C33 exceeds the rated value, chip U1 disconnects from MOSFET Q2, MOSFET Q3, and transistor Q5, and stops supplying power to transformer T2, thereby achieving overcurrent protection and overpower protection.

[0098] In this specification, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0099] In the description of this specification, the references to terms such as "preferred embodiment," "another embodiment," "other embodiment," or "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in a suitable manner in any one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0100] Although embodiments of this application have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting this application. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of this application.

Claims

1. A constant current and constant voltage switching power supply circuit with NFC function, characterized in that: It includes an EMC electromagnetic filter circuit, a rectifier filter circuit, a PFC boost circuit, an LLC resonant circuit, an output synchronous rectifier circuit, an output control circuit, an output voltage feedback circuit, and an NFC circuit. The EMC electromagnetic filter circuit is connected to the power input terminal. One end of the rectifier filter circuit is connected to the EMC electromagnetic filter circuit, and the other end of the rectifier filter circuit is connected to one end of the PFC boost circuit. The other end of the PFC boost circuit is connected to the LLC resonant circuit. The other end of the LLC resonant circuit is connected to the output control circuit through the output synchronous rectifier circuit and the output voltage feedback circuit. The output control circuit is also connected to the NFC circuit and the power output terminal.

2. The constant current and constant voltage switching power supply circuit with NFC function according to claim 1, characterized in that: The EMC electromagnetic filter circuit includes a fuse F1, common mode inductors LF1 and LF2, a magnetic core inductor L1, capacitors C1, C2, C3, C4, and C8, and diodes D7 and D8; the rectifier filter circuit includes a rectifier bridge BD1 and capacitor C5. One end of fuse F1 is connected to the live wire, and the other end of fuse F1 is connected to one end of common mode inductor LF1. The other end of common mode inductor LF1 is connected to the neutral wire. Capacitor C1 is connected in parallel across the two ends of common mode inductor LF1. Capacitor C2, along with capacitors C3 and C4 connected in series, is connected in parallel between common mode inductor LF1 and common mode inductor LF2. The two ends of capacitor C2, one end of capacitor C3, and one end of capacitor C4 are respectively connected to common mode inductor LF1. The other ends of capacitor C3 and capacitor C4 are grounded through capacitor C8. One end of the common-mode inductor LF2 is connected to the positive terminal of diode D7 and one input terminal of rectifier BD1. The other end of the common-mode inductor LF2 is connected to one end of the core inductor L1. The other end of the core inductor L1 is connected to the positive terminal of diode D8 and the other input terminal of rectifier BD1. The negative terminal of diode D7 is connected to the negative terminal of diode D8. The output terminal of rectifier BD1 is connected to the PFC boost circuit through capacitor C5.

3. The constant current and constant voltage switching power supply circuit with NFC function according to claim 2, characterized in that: The PFC boost circuit includes chip U1, resistors R1, R2, R5, R10, R11, R12, R13, R14, R19, R20, R26, R29, R32, R33, R34, R38, R53, R54, R55, inductors L2A, L2B, and L4, switch S1, capacitors C10, C11, C12, C13, C14, C22, C23, C47, and C48, diodes D3, D9, and D12, transistor Q4, MOSFET Q1A, and MOSFET Q1; One end of resistor R1 is connected to the cathodes of diodes D7 and D8. The other end of resistor R1 is connected in series with resistors R2, R14, and R5. One end of resistor R5 is connected to one end of capacitor C11 and one end of resistor R26. The other ends of capacitor C11 and resistor R26 are grounded. One end of resistor R5, one end of capacitor C11, and one end of resistor R26 are also connected to the LNS pin of chip U1. The two output terminals of the rectifier BD1 are connected through capacitor C5. Capacitor C5 is also grounded through resistor R32. Resistor E33 is connected in parallel with resistor R32. Capacitor C5 is also grounded through series resistor R29 and capacitor C12. Resistor R32 is connected in parallel with series resistor R29 and capacitor C12. One end of resistor R29 and one end of capacitor C12 are connected to the CS pin of chip U1. One output terminal of rectifier BD1 is also connected to one end of inductor L2A. The other end of inductor L2A is connected to ground in series with inductor L4, diode D9, and capacitor C23. Diode D9 is also connected to LLC resonant circuit. Diode D9 is also connected in series with resistors R19, R20, and R45. One end of resistor R45 is grounded through parallel resistors R34, R38, and capacitor C22. Resistor R45 and capacitor C22 are also connected to the FBB pin of chip U1. Resistors R19, R20, R45, and capacitor C23 are connected in parallel. The capacitors C10, C13, and C14 are connected in parallel with the capacitor C23; the inductor L2B is connected in parallel with the inductor L2A; and the diode D12 is connected in parallel with the inductor L2A, the inductor L4, and the diode D9. Inductor L2A is also connected to the drain of MOSFET Q1A, one end of resistor R10, and one end of capacitor C48. The other end of resistor R10 is connected to the HV pin of chip U1. The other end of capacitor C48 is connected to the source of MOSFET Q1A through resistor R55. The source of MOSFET Q1A is grounded. Resistor R54 and capacitor C47 are connected in parallel with resistor R55. The gate of MOSFET Q1A is connected to one end of resistor R12. The other end of resistor R12 is connected to the emitter of transistor Q4, one end of resistor R13, and one end of resistor R11. The collector of transistor Q4 is connected to the source of MOSFET Q1A. The base of transistor Q4 is connected to the anode of diode D3 and resistor R53. The cathode of diode D3 is connected to resistor R10. Resistor R53 is connected to the GATEB pin of chip U1. The other end of resistor R13 is grounded. The other end of R11 is connected to the gate of MOSFET Q1. The source of MOSFET Q1 is grounded. The drain of MOSFET Q1 is connected to inductor L2A.

4. The constant current and constant voltage switching power supply circuit with NFC function according to claim 3, characterized in that: The LLC resonant circuit includes resistors R3, R4, R7, R15, R16, R17, R22, R23, R24, R25, R44, and R37; capacitors C6, C7, R8, C17, C18, C18, C30, C31, C32, C33, C35, C49; inductors L3A and L3B; diodes D1, D2, D4, and D5; Zener diode ZD1; transistor Q5; MOSFET Q2 and Q3; diode D6; and transformer T2. One end of resistor R23 is connected to the GATEH pin of chip U1, the other end of resistor R23 is connected to one end of resistor R22, the other end of resistor R22 is connected to one end of resistor R16 and the gate of MOSFET Q2, and diode D4 is connected in parallel with resistor R22. The drain of MOSFET Q2 is connected to the cathode of diode D9, and the source of MOSFET Q2 is connected to the drain of MOSFET Q3. The source of MOSFET Q2 is connected to the ISEN pin of chip U1 through capacitor C31. The gate of MOSFET Q3 is connected in series with resistors R25 and R24 and the GATEL pin of chip U1. The gate of MOSFET Q3 is also connected to one end of resistor R17, and the other end of resistor R17 is connected to capacitor C31. The source of MOSFET Q2 is also connected to one end of inductor L3A and capacitor C4. One end of 9 is connected, and the other end of capacitor C49 is connected to the source of MOSFET Q3; the T2D winding of transformer T2 is connected to the other end of inductor L3A and one end of capacitors C32 and C33; the other end of capacitor C32 is connected to one end of resistor R37, one end of resistor R9 and one end of resistor R8; the other end of resistor R8 is grounded, and the other ends of resistor R8, resistor R9 and capacitor C33 are all connected to capacitor C31; the other end of resistor R37 is connected to the ISEN pin of chip U1. Capacitor C30 is also connected to the negative terminal of diode D2. The positive terminal of diode D2 is connected to the HS pin of chip U1 and is also connected to the negative terminal of diode D1, one end of capacitor C18, and one end of capacitor C7. The diode D1 is connected to the emitter of transistor Q5. The base of transistor Q5 is connected to the negative terminal of Zener diode ZD1 and one end of resistor R4. The collector of transistor Q5 is connected to the negative terminal of diode D6, the other end of resistor R4, and one end of capacitor C35. Transformer T2 is connected to the positive terminal of diode D6, the other end of capacitor C35, the other end of Zener diode ZD1, the other end of capacitor C7, and the other end of capacitor C18, and is connected to the VSEN pin of chip U1 through capacitor C6. Resistor R15 is connected in parallel with capacitor C6, and resistor R44 is connected between resistor R4 and capacitor C6. Windings T2A, T2B, and T2C of transformer T2 are all connected to the output synchronous rectifier circuit.

5. The constant current and constant voltage switching power supply circuit with NFC function according to claim 1, characterized in that: The output synchronous rectification circuit includes capacitors C9, C20, C21, C24, C25, C26, C27, C28, C29, C34, C36, C37, C38, C39, C40, C41, and C45; resistors R31, R47, R46, R63, R64, R65, R66, R69, R70, R71, R72, R73, and RS1; diodes D11 and D10; Zener diode ZD2; MOSFETs Q8 and Q9; transistor Q10; and chip U3. The winding T2A of transformer T2 is connected to the positive terminal of diode D10, one end of capacitor C29, and the rectifier terminal of Zener diode ZD2. The negative terminal of diode D10 is connected to the other end of capacitor C29 and to an external power supply. The VO+ terminal of transformer T2 is also connected to one end of resistor R46 and the collector of transistor Q10. The other end of resistor R46 is connected to the base of transistor Q10. The emitter of transistor Q10 is connected to the positive terminal of diode D11. The negative terminal of diode D1 is connected to an external power supply. The VO+ terminal of transformer T2 is connected to ground in series with resistors R47 and RS1. Capacitor C45 is connected in parallel with resistors R47 and RS1. Capacitors C24, C23, C26, C27, C28, and resistor R31 are connected in parallel with resistor R7. Resistors R47 and RS1 are also connected to winding T2A of transformer T2. The winding T2A of the transformer T2 is also connected to one end of the capacitor C38, the source of the MOSFET Q8, the gate of the MOSFET Q8, the second pin of the chip U3, the fifth pin of the chip U3, and one end of the resistor R69. The other end of the resistor R69 is connected to the third pin of the chip U3. The capacitor C34 is connected in parallel with the resistor R69. The other end of the capacitor C38 is connected to the sixth pin of the chip U3 through the series resistors R7 and R63. The resistors R70 and R71 are connected in parallel. The drain of the MOSFET Q8 is also connected to the winding T2B of the transformer T2 and the resistor R7. The base of the MOSFET Q8 is also connected to the eighth pin of the chip U3 through the resistor R65. The winding T2A of the transformer T2 is also connected to one end of the capacitor C39, the source of the MOSFET Q9, and the gate of the MOSFET Q9. The gate of the MOSFET Q9 is also connected to the gate of the MOSFET Q8 and one end of the resistor R66. The other end of the resistor R66 is connected to the first pin of the chip U3. The other end of the capacitor C39 is connected to the fourth pin of the chip U3 through the series resistors R73 and R64. The resistors R72 and R73 are connected in parallel. The drain of the MOSFET Q9 is also connected to the winding T2C of the transformer T2 and the resistor R73. The fifth pin of chip U3 is also connected to the seventh pin of chip U3 through resistor C36. The capacitor C37 is connected in parallel with capacitor C36. The seventh pin of chip U3 is also connected to an external power supply.

6. The constant current and constant voltage switching power supply circuit with NFC function according to claim 3, characterized in that: The output control circuit includes capacitors CX1, CX2, CX3, CX4, CX5, CX13, CX14, CX15, CX16, CX17, and CX18; resistors RX1, RX2, RX3, RX4, RX5, RX6, RX20, RX21, RX22, RX23, RX24, RX25, RX26, RX27, and RX28; a thermistor NX1; chips UX1, UX2, UX4, and UX5; an LED LD1; and a Zener diode UX2. The first and third pins of chip UX1 are connected to the two ends of capacitor CX1. The first pin of chip UX1 is grounded. The second pin of chip UX1 is connected to an external power supply. Capacitor CX2 is connected in parallel with capacitor CX1. The third pin of chip UX1 is also connected to the VDD pin of chip UX4. One end of the resistor RX3 is connected to the winding T2A of the transformer T2, and the other end of the resistor RX3 is connected to the VCS terminal of the chip UX4 through the series resistors RX4 and RX24. The capacitor CX4 is connected in parallel with the resistor RX4. The first pin of the chip UX5 is connected to resistors RX4 and RX24. The second and third pins of the chip UX5 are grounded. The third pin of the chip UX5 is also connected to one end of capacitor CX18 and one end of capacitor CX15. The other end of capacitor CX18 is connected to resistor RX3. The other end of capacitor CX15 is connected to the VCS terminal of the chip UX4. One end of the resistor RX26 is connected to the LLC resonant circuit, and the other end of the resistor RX26 is connected to one end of the resistor RX27 and the VOS pin of the chip UX4. The other end of the resistor RX27 is grounded, and the capacitor CX16 is connected in parallel with the resistor RX27. One end of the thermistor NX1 is connected to the fifth pin of the chip UX5, and the other end of the thermistor NX1 is connected to the VTS pin of the chip UX4 and one end of the resistor RX28. The other end of the resistor RX28 is grounded. The resistor RX25 is connected in parallel with the thermistor NX1, and the capacitor CX17 is connected in parallel with the resistor RX28. One end of the resistor RX15 is connected to an external power supply, the other end of the resistor RX15 is connected to the VAS pin of the chip UX4 and one end of the resistor RX6, the other end of the resistor RX6 is grounded, and the capacitor CX5 is connected in parallel with the resistor RX6. One end of resistor RX1 is connected to the LEDG pin of chip UX4, and the other end of resistor RX1 is connected to the positive terminal of light-emitting diode LD1, and the negative terminal of light-emitting diode LD1 is grounded; one end of resistor RX2 is connected to the VDD pin of chip UX4, and the other end of resistor RX2 is connected to the first pin of chip UX2, the second pin of chip UX2 is grounded, the third pin of chip UX2 is connected to the ninth pin of chip UX4, and capacitor CX3 is connected in parallel with chip UX2; Resistor RX20 is connected to the VDD pin of chip UX4. Resistor RX21 and resistor RX20 are also connected to the PWMA pin of chip UX4. Resistor RX21 is grounded through capacitor CX13. Resistor RX21 and capacitor CX13 are also connected to the power output terminal. Resistor RX22 is connected to the VDD pin of chip UX4. Resistor RX23 and resistor RX22 are also connected to the PWMB pin of chip UX4. Resistor RX23 is grounded through capacitor CX14. Resistor RX23 and capacitor CX14 are also connected to the power output terminal. The NFC circuit includes chip U4; the fifth pin of chip U4 is connected to the SB5 pin of chip UX4, the sixth pin of chip U4 is connected to the SB2 pin of UX4, and the eighth pin of chip U4 is connected to the SB3 pin of UX4.

7. The constant current and constant voltage switching power supply circuit with NFC function according to claim 6, characterized in that: The NFC circuit also includes an RF transformer T1 and a capacitor C16; the second and third pins of chip U4 are connected to the RF transformer T1; and the capacitor C16 is connected in parallel with the RF transformer T1.

8. The constant current and constant voltage switching power supply circuit with NFC function according to claim 1, characterized in that: The output voltage feedback circuit includes optocoupler U2, resistors RX8 and RX9, diodes DX1B and DX1A, resistors RX10, RX11, RX12, RX13, RX14, RX15, RS16, RX17, RS18, RX19, RX29, capacitors CX6, CX8, CS9, CX10, CX11, CX12, and operational amplifier UX6. One end of resistor RX29 is connected to the VDD terminal of chip UX4, and the other end of resistor RX29 is grounded through capacitor CX6. The other end of resistor RX29 is also connected to the VDA pin of chip UX5, the eighth pin of operational amplifier UX6, and one end of resistor RX8. The other end of resistor RX8 is connected to one end of resistor RX9, and the other end of resistor RX9 is connected to the anodes of diodes DX1B and DX1A. The negative terminal of diode DX1B is connected to the seventh pin of the operational amplifier. The seventh pin of the operational amplifier UX6 is also connected to the sixth pin of the operational amplifier UX6 through resistor RX10 and capacitor CX8. The sixth pin of the operational amplifier UX6 is connected to one end of resistor RX17, one end of capacitor CX12, and one end of resistor RX19. The other end of capacitor CX12 is connected to one end of resistor RX18. The other ends of resistors RX17 and RX18 are connected to the VO+ terminal of transformer T2. The other end of resistor RX19 is grounded. The fifth pin of the operational amplifier UX6 is grounded through resistor RX15. Capacitor CX11 is connected in parallel with resistor RX15. The fifth pin of the operational amplifier UX6 is also connected to resistor RX21 and capacitor CX13 in series through resistor RX14. The positive terminal of diode DX1A is connected to the first pin of operational amplifier UX6. The first pin of operational amplifier UX6 is connected to the second pin of operational amplifier UX6 through resistor RX11 and capacitor CX9. The second pin of operational amplifier UX6 is grounded through resistor RX12. The third pin of operational amplifier UX6 is connected to resistor RX22 and capacitor CX14 through series resistor RX16. The fourth pin of the operational amplifier UX6 is connected to the winding T2A of the transformer T2 through a series capacitor CX10 and a resistor RX13; one end of the optocoupler U2 is connected to both ends of the resistor RX8, and the other end of the optocoupler U2 is connected to both ends of the capacitor C17; the capacitor CX7 is connected in parallel with the resistor RX9.

9. The constant current and constant voltage switching power supply circuit with NFC function according to claim 2, characterized in that: It also includes a surge protection circuit, which consists of an impedance Z1, a thermistor N1, and a relay K1. The impedance Z1 and capacitor C2 are connected in parallel across the common-mode inductor LF1. The relay K1 is connected between the other end of the common-mode inductor LF2 and one end of the magnetic core inductor L1. The relay K1 is also connected to one input terminal of the rectifier BD1 in the EMC electromagnetic filter circuit. The relay K1 is also connected to the LLC resonant circuit through resistor R7.

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