Power supply circuit with over-current protection

Abstract

The utility model relates to the technical field of power supplies, and discloses an overcurrent protection power supply circuit, which comprises a power supply input circuit, a rectification filter circuit, a transformer circuit, a PWM (Pulse Width Modulation) control circuit, a voltage stabilizing circuit and an indication output circuit, and is characterized in that the output end of the power supply input circuit is respectively connected with the input end of the rectification filter circuit and the signal end of the PWM control circuit; the power input end of the PWM control circuit is connected with an external direct-current power source, the output end of the rectification filter circuit and the output end of the PWM control circuit are connected with the input end of the transformer circuit, the output end of the transformer circuit is connected with the input end of the voltage stabilizing circuit, and the output end of the voltage stabilizing circuit is connected with the input end of the indication output circuit. The output end of the indication output circuit serves as the output end of the power supply circuit; the power supply circuit realizes two-section protection in a hiccup mode and over-current locking, so that a terminal product with a high over-current point can work normally and can also be effectively protected when working abnormally, meanwhile, the process is simplified, and the cost is reduced.

Description

Technical Field

[0001] The utility model relates to the technical field of power supply, in particular to a power supply circuit with overcurrent protection. Background Art

[0002] A switching power supply, also known as an exchange power supply or a switching converter, is a high-frequency power conversion device and a type of power supply. Its function is to convert a voltage level into the voltage or current required by the user through different forms of architecture. Generally, the input of a switching power supply is mostly AC power (such as mains power), which is then output to devices that require DC power, such as personal computers, mobile phones, etc., through a switching power adapter, and the switching power supply performs the voltage and current conversion between the two.

[0003] In the current market, many switching power supplies generally use one-stage overcurrent protection, which may cause false operation or leakage, affecting the normal operation and safety of the electrical equipment used with it. In addition, this existing overcurrent protection has the problem of complex and cumbersome production process and high cost. For example, when the load current reaches the design value, the overcurrent protection is realized. When this protection circuit is used in products with instantaneous high overcurrent points of motors, there will be abnormal operation. To meet the high overcurrent point requirements, the production process is complex and the cost is high.

[0004] Therefore, in view of the above problems, the existing power supply technology needs to be further improved. Utility Model Content

[0005] The purpose of the utility model is to overcome the many problems of the existing one-stage overcurrent protection, such as: when the load current reaches the design value, the overcurrent protection is realized, and this protection circuit has abnormal operation when used in products with instantaneous high overcurrent points of motors. To meet the high overcurrent point requirements, the manufacturing process requirements are complex, the cost is high, and there are also safety issues. Through the rational design of the power supply circuit, the power input circuit, the rectifier filter circuit, the transformer circuit, the PWM control circuit, the voltage stabilization circuit and the indication output circuit are used in coordination with each other, and the two-stage protection in the hiccup mode and overcurrent lockout can be realized, so that the terminal products with high overcurrent points can work normally and can be effectively protected when working abnormally.

[0006] The technical solution of the utility model is as follows:

[0007] A power supply circuit for overcurrent protection, the power supply circuit comprising: a power input circuit, a rectifier and filter circuit, a transformer circuit, a PWM control circuit, a voltage stabilizing circuit and an indication output circuit, wherein the power input end of the power input circuit is connected to an external AC power supply, the output end of the power input circuit is respectively connected to the input end of the rectifier and filter circuit and the signal end of the PWM control circuit, the power input end of the PWM control circuit is connected to an external DC power supply, the output end of the rectifier and filter circuit and the output end of the PWM control circuit are respectively connected to the input end of the transformer circuit, the output end of the transformer circuit is connected to the input end of the voltage stabilizing circuit, the output end of the voltage stabilizing circuit is connected to the input end of the indication output circuit, and the output end of the indication output circuit serves as the output end of the power supply circuit;

[0008] The PWM control circuit includes a thermistor RT2, a resistor R43, a capacitor C11, a resistor R67, a diode D13, a chip U2, a resistor R1, a capacitor C9, a resistor R4, a resistor R5, a diode D3, a capacitor C8, a resistor R3, a resistor R6, a resistor R7, a resistor R8, a capacitor C12, an NMOS tube Q1, a resistor R53, a resistor R54, a resistor R36, a diode D6 and a diode D7. The "1" terminal of the chip U2 is connected in parallel to one end of the resistor R43 and one end of the resistor R67. The other end of the resistor R43 is connected in parallel to the The terminal of the chip U2 is connected to one end of the thermistor RT2, and the other end of the thermistor RT2 is grounded. The other end of the resistor R67 is connected to the positive electrode of the diode D13, and the negative electrode of the diode D13 is connected to a DC power supply. The terminal "2" of the chip U2 is connected to one end of the capacitor C11, and the other end of the capacitor C11 is grounded. The terminal "4" of the chip U2 is grounded. The terminal "3" of the chip U2 is connected in parallel to one end of the capacitor C8 and one end of the resistor R3. The other end of the capacitor C8 is grounded. The other end of the resistor R3 is connected in parallel to one end of the resistor R7, one end of the resistor R8, and one end of the capacitor C11. One end of C12 is connected to the source of NMOS tube Q1, the other end of the resistor R7 and the other end of the resistor R8 are grounded, the other end of the capacitor C12 is connected in parallel to the drain of NMOS tube Q1 and one end of the input end of the transformer circuit, the gate of NMOS tube Q1 is connected in parallel to one end of resistor R6, one end of resistor R5 and the positive electrode of diode D3, the other end of resistor R6 is grounded, the other end of resistor R5 and the negative electrode of diode D3 are connected to one end of resistor R4, the other end of resistor R4 is connected to the "5" terminal of chip U2, and the "6" terminal of chip U2 is connected to the external A DC power supply and one end of a capacitor C9, the other end of the capacitor C9 is grounded, the "8" terminal of the chip U2 is connected to one end of a resistor R1, the other end of the resistor R1 is connected in parallel to the cathode of a diode D6, the cathode of a diode D7 and one end of a resistor R36, the other end of the resistor R36 is connected to the other end of the input end of the transformer circuit and one end of a resistor R53, the other end of the resistor R53 is connected to one end of a resistor R54, the other end of the resistor R54 is connected to one end of a capacitor C8, the anode of the diode D6 and the anode of the diode D7 are respectively connected to the output end of the power input circuit.

[0009] Furthermore, the power input circuit includes a fuse F2, a capacitor CX1, a thermistor RT1, a varistor RV1, a mutual inductance LF1, a capacitor CX2, a resistor RX1, a resistor RX2, a resistor RX3 and a resistor RX4, one end of the fuse F2 is connected to the live wire of the AC power supply, the other end of the fuse F2 is respectively connected to one end of the capacitor CX1, one end of the varistor RV1 and a "4" terminal of the mutual inductance LF1, the "1" terminal of the mutual inductance LF1 is connected in parallel to the other end of the capacitor CX1, the other end of the varistor RV1 and one end of the thermistor RT1, and the The other end of the thermistor RT1 is connected to the neutral line of the AC power supply, the "3" terminal of the mutual inductance LF1 is connected in parallel to one end of the capacitor CX2, one end of the resistor RX1, one end of the resistor RX2, the positive electrode of the diode D7 and one end of the input end of the rectifier and filter circuit, the "2" terminal of the mutual inductance LF1 is connected in parallel to the other end of the capacitor CX2, one end of the resistor RX3, one end of the resistor RX4, the positive electrode of the diode D6 and the other end of the input end of the rectifier and filter circuit, and the other end of the resistor RX1 and the other end of the resistor RX2 are connected to the other end of the resistor RX3 and the other end of the resistor RX4.

[0010] Further, the rectifier and filter circuit includes a mutual inductance LF2b, a bridge rectifier BD1, a capacitor EC1, a capacitor C13, a resistor R14, a resistor R12, a resistor R13, a resistor R11, a resistor R15, a resistor R16, a capacitor C2, a resistor R44, a resistor R45, a capacitor C6 and a diode D1, the mutual inductance LF2b "2" terminal is connected to the positive electrode of the diode D6, the mutual inductance LF2b "3" terminal is connected to the positive electrode of the diode D7, the mutual inductance LF2b "1" terminal is connected to the bridge rectifier BD1 "4" terminal, the mutual inductance LF2b "4" terminal is connected to the bridge rectifier BD1 "2" terminal, the bridge rectifier BD1 "1" terminal is grounded, and the bridge rectifier BD1 "3" terminal is connected in parallel to the capacitor EC1. end, one end of capacitor C13, one end of resistor R14, one end of resistor R12, one end of resistor R13, one end of capacitor C2, one end of resistor R44 and one end of the input end of the transformer circuit, the other end of capacitor EC1 and the other end of capacitor C13 are grounded, the other end of resistor R14, the other end of resistor R12, the other end of resistor R13 and the other end of capacitor C2 are connected to one end of resistor R11, one end of resistor R15 and one end of resistor R16, the other end of resistor R11, the other end of resistor R15 and the other end of resistor R16 are connected to the cathode of diode D1, the anode of diode D1 is connected to the drain of NMOS tube Q1, the other end of resistor R44 is connected to one end of resistor R45, the other end of resistor R45 is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded.

[0011] Furthermore, the bridge rectifier BD1 selects a rectifier bridge of model KBU10060.

[0012] Furthermore, the transformer circuit includes a transformer T1, the transformer T1 "2" terminal is connected to the drain of the NMOS tube Q1, the transformer T1 "1" terminal is connected to the output end of the rectifier and filter circuit, the transformer T1 "3" terminal is connected to the input end of the voltage stabilization circuit, and the transformer T1 "4" terminal is grounded.

[0013] Furthermore, the voltage stabilizing circuit includes a transformer output voltage stabilizing circuit and an output voltage voltage stabilizing circuit, the input end of the transformer output voltage stabilizing circuit is connected to the output end of the transformer circuit, and the output end of the transformer output voltage stabilizing circuit is connected to the input end of the output voltage stabilizing circuit and the input end of the indication output circuit.

[0014] Furthermore, the transformer output voltage stabilizing circuit includes a diode ZD2, a capacitor C1, a resistor R20, a resistor R19, a zener diode D6 and a zener diode D6a, the positive electrode of the diode ZD2, one end of the capacitor C1, the positive electrode of the zener diode D6 and the positive electrode of the zener diode D6a are connected to one end of the output end of the transformer circuit, the other end of the capacitor C1 is connected to one end of the resistor R20 and one end of the resistor R19, the other end of the resistor R20 and the other end of the resistor R19 are connected to the cathode of the diode ZD2, the cathode of the zener diode D6, the cathode of the zener diode D6a and the input end of the output voltage stabilizing circuit and the input end of the indication output circuit.

[0015] Furthermore, the output voltage stabilizing circuit includes a resistor R30, a resistor R21, a resistor R27, a resistor R22, an optical coupler U3, a resistor R69, a resistor R70, a resistor R9, a capacitor C10, a resistor R24, a capacitor C7, a voltage regulator U1 and a resistor R25, one end of the resistor R30 and one end of the resistor R27 are connected to the output end of the transformer output stabilizing circuit, the other end of the resistor R30 is connected to one end of the resistor R21, the other end of the resistor R21 is connected in parallel to the optical coupler U3 "2" terminal and one end of the resistor R22, and the optical coupler U3 "4" terminal and the other end of the resistor R22 are connected to the resistor R The other end of the resistor R27 is connected in parallel to one end of the capacitor C10, the other end of the capacitor C7, one end of the resistor R25 and the "3" terminal of the voltage regulator U1. The other end of the resistor R24 ​​is connected to the other end of the capacitor C10. The other end of the resistor R25 and the "1" terminal of the voltage regulator U1 are grounded together. The "1" terminal of the optocoupler U3 is connected in parallel to one end of the resistor R9, one end of the resistor R70 and one end of the resistor R69. The other end of the resistor R9 and the other end of the resistor R70 are grounded together with the "3" terminal of the optocoupler U3. The other end of the resistor R69 is connected to the "2" terminal of the chip U2.

[0016] Furthermore, the indication output circuit includes an inductor L1, a capacitor EC4, a capacitor EC3, a capacitor EC2, a mutual inductance LF3, a resistor R2a and an LED1, one end of the inductor L1, one end of the capacitor EC4 and one end of the capacitor EC3 are commonly connected to the output end of the voltage stabilizing circuit, one end of the capacitor EC2 and the mutual inductance LF3 "4" terminal are commonly connected to the other end of the inductor L1, the other end of the capacitor EC4, the other end of the capacitor EC3, the other end of the capacitor EC2 and the mutual inductance LF3 "1" terminal are commonly grounded, the mutual inductance LF3 "3" terminal is connected to one end of the resistor R2a and the positive pole of the output end, the other end of the resistor R2a is connected to the positive pole of LED1, and the mutual inductance LF3 "2" terminal is commonly grounded with the negative pole of LED1 and the negative pole of the output end.

[0017] Furthermore, the chip U2 is a chip of model OB5283.

[0018] Furthermore, the optical coupler U3 is an optical coupler of model 817C.

[0019] Furthermore, the voltage regulator tube U1 is a TL431 voltage regulator tube.

[0020] Beneficial Effects

[0021] The utility model rationalizes the design of the power supply circuit, adopts the cooperation of the power supply input circuit, the rectifier filter circuit, the transformer circuit, the PWM control circuit, the voltage stabilizing circuit and the indicating output circuit, and can realize two-stage protection in the hiccup mode and overcurrent lockout, so that the terminal products with high overcurrent points can work normally and can be effectively protected when working abnormally. Among them, the two-stage output current protection threshold is set for the OB5283 chip in the PWM control circuit, and the two thresholds correspond to the normal OCP protection and the peak power protection respectively. When the output is overloaded, the two-stage overcurrent protection will be activated to realize the protection of entering the periodic hiccup mode first, and then entering the peak overcurrent lockout protection product. Only when the AC power supply is restarted can it work normally. Specifically, the two-stage output current protection threshold is used, the first stage is the overload periodic hiccup mode, and the second stage is the peak overcurrent protection lockout function in the frequency doubling mode, which effectively protects the product, simplifies the process, and realizes cost reduction. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 The utility model is a schematic diagram of the structure of a power supply circuit with overcurrent protection.

[0023] Figure 2 The utility model is a schematic diagram of the principle of an overcurrent protection power supply circuit.

[0024] Figure numbers: 01, power input circuit; 02, rectifier and filter circuit; 03, voltage stabilization circuit; 04, indication output circuit; 05, transformer circuit; 06, PWM control circuit. DETAILED DESCRIPTION

[0025] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0026] See also Figure 1-Figure 2 As shown, the utility model provides a power supply circuit with overcurrent protection, which includes: a power input circuit 01, a rectifier and filter circuit 02, a transformer circuit 05, a PWM control circuit 06, a voltage stabilizing circuit 03 and an indication output circuit 04, wherein the power input end of the power input circuit 01 is connected to an external AC power supply, the output end of the power input circuit 01 is respectively connected to the input end of the rectifier and filter circuit 02 and the signal end of the PWM control circuit 06, the power input end of the PWM control circuit 06 is connected to an external DC power supply, the output end of the rectifier and filter circuit 02 and the output end of the PWM control circuit 06 are respectively connected to the input end of the transformer circuit 05, the output end of the transformer circuit 05 is connected to the input end of the voltage stabilizing circuit 03, the output end of the voltage stabilizing circuit 03 is connected to the input end of the indication output circuit 04, and the output end of the indication output circuit 04 serves as the output end of the power supply circuit;

[0027] The voltage stabilizing circuit 03 includes a transformer output voltage stabilizing circuit and an output voltage stabilizing circuit, the input end of the transformer output voltage stabilizing circuit is connected to the output end of the transformer circuit 05, and the output end of the transformer output voltage stabilizing circuit is connected to the input end of the output voltage stabilizing circuit and the input end of the indicating output circuit 04;

[0028] Specifically, the power input circuit 01 includes a fuse F2, a capacitor CX1, a thermistor RT1, a varistor RV1, a mutual inductance LF1, a capacitor CX2, a resistor RX1, a resistor RX2, a resistor RX3 and a resistor RX4; the rectifier and filter circuit 02 includes a mutual inductance LF2b, a bridge rectifier BD1, a capacitor EC1, a capacitor C13, a resistor R14, a resistor R12, a resistor R13, a resistor R11, a resistor R15, a resistor R16, a capacitor C2, a resistor R44, a resistor R45, a capacitor C6 and a diode D1; the voltage stabilizing circuit 03 includes a resistor R30, a resistor R21, a resistor R27, a resistor R22, an optical coupler U3, a resistor R69, a resistor R70, a resistor R9, a capacitor C10, a resistor R24, a capacitor C7, a voltage regulator U1 and a resistor R25 in the output voltage stabilizing circuit, and a diode Z in the transformer output stabilizing circuit. D2, capacitor C1, resistor R20, resistor R19, voltage regulator D6 and voltage regulator D6a; the transformer circuit 05 includes transformer T1; the indication output circuit 04 includes inductor L1, capacitor EC4, capacitor EC3, capacitor EC2, mutual inductance LF3, resistor R2a and LED1; the PWM control circuit 06 includes thermistor RT2, resistor R43, capacitor C11, resistor R67, diode D13, chip U2, resistor R1, capacitor C9, resistor R4, resistor R5, diode D3, capacitor C8, resistor R3, resistor R6, resistor R7, resistor R8, capacitor C12, NMOS tube Q1, resistor R53, resistor R54, resistor R36, diode D6 and diode D7; the power supply circuit also includes resistor R12, diode D2, capacitor EC6, diode D4, capacitor EC5, resistor R23 and resistor R23a;

[0029] Among them, one end of the fuse F2 in the power input circuit 01 is connected to the live wire of the AC power supply, and the other end of the fuse F2 is respectively connected to one end of the capacitor CX1, one end of the varistor RV1 and the mutual inductance LF1 "4" terminal, the mutual inductance LF1 "1" terminal is connected in parallel to the other end of the capacitor CX1, the other end of the varistor RV1 and one end of the thermistor RT1, the other end of the thermistor RT1 is connected to the neutral line of the AC power supply, the mutual inductance LF1 "3" terminal is connected in parallel to one end of the capacitor CX2, one end of the resistor RX1, one end of the resistor RX2, the positive electrode of the diode D7 and the mutual inductance LF2b "3" terminal of the rectifier and filter circuit 02, the mutual inductance LF1 "2" terminal is connected in parallel to the other end of the capacitor CX2, one end of the resistor RX3, one end of the resistor RX4, the positive electrode of the diode D6 and the mutual inductance LF2b "2" terminal of the rectifier and filter circuit 02, the other end of the resistor RX1 and the other end of the resistor RX2 are commonly connected to the other end of the resistor RX3 and the other end of the resistor RX4;

[0030] Among them, the mutual inductance LF2b "2" terminal in the rectifier and filter circuit 02 is connected to the positive electrode of the diode D6, the mutual inductance LF2b "3" terminal is connected to the positive electrode of the diode D7, the mutual inductance LF2b "1" terminal is connected to the bridge rectifier BD1 "4" terminal, the mutual inductance LF2b "4" terminal is connected to the bridge rectifier BD1 "2" terminal, the bridge rectifier BD1 "1" terminal is grounded, and the bridge rectifier BD1 "3" terminal is connected in parallel to one end of the capacitor EC1, one end of the capacitor C13, one end of the resistor R14, one end of the resistor R12, one end of the resistor R13, one end of the capacitor C2, one end of the resistor R44 and the transformer T1 "1" of the transformer circuit 05. Terminal, the other end of capacitor EC1 and the other end of capacitor C3 are grounded, the other end of resistor R14, the other end of resistor R12, the other end of resistor R13 and the other end of capacitor C2 are connected to one end of resistor R11, one end of resistor R15 and one end of resistor R16, the other end of resistor R11, the other end of resistor R15 and the other end of resistor R16 are connected to the cathode of diode D1, the anode of diode D1 is connected to the drain of NMOS tube Q1, the other end of resistor R44 is connected to one end of resistor R45, the other end of resistor R45 is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded; the bridge rectifier BD1 selects a rectifier bridge of model KBU10060;

[0031] Among them, the transformer T1 "2" terminal in the transformer circuit 05 is connected to the drain of the NMOS tube Q1, the transformer T1 "1" terminal is connected to the bridge rectifier BD1 "3" terminal of the rectifier filter circuit 02, the transformer T1 "3" terminal is connected to the positive electrode of the diode ZD2 of the voltage stabilizing circuit 03, and the transformer T1 "4" terminal is grounded;

[0032] Among them, the positive electrode of the diode ZD2, one end of the capacitor C1, the positive electrode of the voltage regulator D6 and the positive electrode of the voltage regulator D6a in the transformer output voltage stabilizing circuit are connected to the transformer T1 "3" terminal of the transformer circuit 05, the other end of the capacitor C1 is connected to one end of the resistor R20 and one end of the resistor R19, the other end of the resistor R20 and the other end of the resistor R19 are connected to the negative electrode of the diode ZD2, the negative electrode of the voltage regulator D6, the negative electrode of the voltage regulator D6a and one end of the resistor R30 of the output voltage stabilizing circuit 03 and one end of the inductor L1 of the indicating output circuit 04;

[0033] Among them, one end of the resistor R30 and one end of the resistor R27 in the output voltage stabilizing circuit are connected to the negative electrode of the voltage regulator D6a of the transformer output voltage stabilizing circuit, the other end of the resistor R30 is connected to one end of the resistor R21, the other end of the resistor R21 is connected in parallel to the optocoupler U3 "2" terminal and one end of the resistor R22, the optocoupler U3 "4" terminal and the other end of the resistor R22 are connected to one end of the resistor R24, one end of the capacitor C7 and the voltage regulator U1 "2" terminal, the other end of the resistor R27 is connected in parallel to one end of the capacitor C10, the other end of the capacitor C7, one end of the resistor R25 and the voltage regulator U1 "3" terminal , the other end of the resistor R24 ​​is connected to the other end of the capacitor C10, the other end of the resistor R25 is grounded together with the "1" terminal of the voltage regulator U1, the "1" terminal of the optocoupler U3 is connected in parallel to one end of the resistor R9, one end of the resistor R70 and one end of the resistor R69, the other end of the resistor R9, the other end of the resistor R70 and the "3" terminal of the optocoupler U3 are grounded together, and the other end of the resistor R69 is connected to the "2" terminal of the chip U2; the chip U2 is selected as the OB5283 chip, the optocoupler U3 is selected as the 817C optocoupler, and the voltage regulator U1 is selected as the TL431 voltage regulator;

[0034] Among them, the chip U2 "1" terminal in the PWM control circuit 06 is connected in parallel to one end of the resistor R43 and one end of the resistor R67, the other end of the resistor R43 is connected to one end of the thermistor RT2, the other end of the thermistor RT2 is grounded, the other end of the resistor R67 is connected to the positive electrode of the diode D13, the negative electrode of the diode D13 is connected to the DC power supply (VCC1), the chip U2 "2" terminal is connected to one end of the capacitor C11, the other end of the capacitor C11 is grounded, the chip U2 "4" terminal is grounded, the chip U2 "3" terminal is connected in parallel to one end of the capacitor C8 and one end of the resistor R3, the other end of the capacitor C8 is grounded, the other end of the resistor R3 is connected in parallel to one end of the resistor R7, one end of the resistor R8, one end of the capacitor C12 and the source of the NMOS tube Q1, the other end of the resistor R7 and the other end of the resistor R8 are grounded, and the other end of the capacitor C12 is connected in parallel to the drain of the NMOS tube Q1 and the transformer circuit The input end of 05, the gate of NMOS tube Q1 is connected in parallel to one end of resistor R6, one end of resistor R5 and the positive electrode of diode D3, the other end of resistor R6 is grounded, the other end of resistor R5 and the negative electrode of diode D3 are connected to one end of resistor R4, the other end of resistor R4 is connected to the "5" terminal of chip U2, the "6" terminal of chip U2 is connected to the external DC power supply (VCC) and one end of capacitor C9, the other end of capacitor C9 is grounded, the "8" terminal of chip U2 is connected to one end of resistor R1, the other end of resistor R1 is connected in parallel to the negative electrode of diode D6, the negative electrode of diode D7 and one end of resistor R36, the other end of resistor R36 is connected to the input end of transformer circuit 05 and one end of resistor R53, the other end of resistor R53 is connected to one end of resistor R54, the other end of resistor R54 is connected to one end of capacitor C8, the positive electrode of diode D6 and the positive electrode of diode D7 are respectively connected to the output end of power input circuit 01;

[0035] Among them, one end of the inductor L1, one end of the capacitor EC4 and one end of the capacitor EC3 in the indication output circuit 04 are connected to the cathode of the diode ZD2 of the voltage stabilizing circuit 03, one end of the capacitor EC2 and the mutual inductance LF3 "4" terminal are connected to the other end of the inductor L1, the other end of the capacitor EC4, the other end of the capacitor EC3, the other end of the capacitor EC2 and the mutual inductance LF3 "1" terminal are grounded, the mutual inductance LF3 "3" terminal is connected to one end of the resistor R2a and the positive electrode of the output terminal, the other end of the resistor R2a is connected to the positive electrode of LED1, and the mutual inductance LF3 "2" terminal is grounded together with the negative electrode of LED1 and the negative electrode of the output terminal;

[0036] Among them, the "5" terminal of transformer T1 is connected to one end of resistor R12, the other end of resistor R12 is connected to the positive electrode of diode D2, the negative electrode of diode D2 is connected in parallel to the positive electrode of diode D4 and one end of capacitor EC6, the negative electrode of diode D4 serves as a DC power supply VCC1, and the negative electrode of diode D4 is connected in parallel to one end of capacitor EC5 and one end of resistor R23a, the other end of resistor R23a is connected to one end of resistor R23, the other end of resistor R23 serves as a DC power supply VCC, and the "6" terminal of transformer T1 is grounded together with the other end of capacitor EC6 and the other end of capacitor EC5.

[0037] Specific implementation methods of the utility model: After assembling the power supply circuit, in order to meet the overload and peak current output requirements, a two-stage output current protection threshold is set for the chip U2 of model OB5283, and the two thresholds correspond to normal OCP protection and peak power protection respectively; when the output is overloaded, after the primary current detection resistor R7 and the resistor R8, the chip U2 "3" terminal detects that the voltage exceeds the OCP protection voltage threshold (assuming 0.295V) and lasts for 1.5s, and the OCP protection enters the periodic hiccup mode; when the output is at the peak current, it enters the frequency doubling mode, and the chip U2 "3" terminal (IC-CS pin) detects that the voltage exceeds the OCP protection voltage threshold (assuming 0.84V) and lasts for 1.5s. At this time, the IC-CS pin is over-voltage, the IC chip U2 stops, the secondary has no output, and the peak overcurrent locks the protection product. Only when the AC power supply is restarted can it work normally.

[0038] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A power supply circuit with overcurrent protection, characterized in that: The power supply circuit comprises: a power supply input circuit, a rectifier and filter circuit, a transformer circuit, a PWM control circuit, a voltage stabilizing circuit and an indication output circuit, wherein the power supply input end of the power supply input circuit is connected to an external AC power supply, the output end of the power supply input circuit is respectively connected to the input end of the rectifier and filter circuit and the signal end of the PWM control circuit, the power supply input end of the PWM control circuit is connected to an external DC power supply, the output end of the rectifier and filter circuit and the output end of the PWM control circuit are respectively connected to the input end of the transformer circuit, the output end of the transformer circuit is connected to the input end of the voltage stabilizing circuit, the output end of the voltage stabilizing circuit is connected to the input end of the indication output circuit, and the output end of the indication output circuit serves as the output end of the power supply circuit; The PWM control circuit includes a thermistor RT2, a resistor R43, a capacitor C11, a resistor R67, a diode D13, a chip U2, a resistor R1, a capacitor C9, a resistor R4, a resistor R5, a diode D3, a capacitor C8, a resistor R3, a resistor R6, a resistor R7, a resistor R8, a capacitor C12, an NMOS tube Q1, a resistor R53, a resistor R54, a resistor R36, a diode D6 and a diode D7. The "1" terminal of the chip U2 is connected in parallel to one end of the resistor R43 and one end of the resistor R67. The other end of the resistor R43 is connected in parallel to the The terminal of the chip U2 is connected to one end of the thermistor RT2, and the other end of the thermistor RT2 is grounded. The other end of the resistor R67 is connected to the positive electrode of the diode D13, and the negative electrode of the diode D13 is connected to a DC power supply. The "2" terminal of the chip U2 is connected to one end of the capacitor C11, and the other end of the capacitor C11 is grounded. The "4" terminal of the chip U2 is grounded. The "3" terminal of the chip U2 is connected in parallel to one end of the capacitor C8 and one end of the resistor R3, and the other end of the capacitor C8 is grounded. The other end of the resistor R3 is connected in parallel to one end of the resistor R7, one end of the resistor R8, and one end of the capacitor C11. One end of C12 is connected to the source of NMOS tube Q1, the other end of the resistor R7 and the other end of the resistor R8 are grounded, the other end of the capacitor C12 is connected in parallel to the drain of NMOS tube Q1 and one end of the input end of the transformer circuit, the gate of NMOS tube Q1 is connected in parallel to one end of resistor R6, one end of resistor R5 and the positive electrode of diode D3, the other end of resistor R6 is grounded, the other end of resistor R5 and the negative electrode of diode D3 are connected to one end of resistor R4, the other end of resistor R4 is connected to the "5" terminal of chip U2, and the "6" terminal of chip U2 is connected to the external A DC power supply and one end of a capacitor C9, the other end of the capacitor C9 is grounded, the "8" terminal of the chip U2 is connected to one end of a resistor R1, the other end of the resistor R1 is connected in parallel to the cathode of a diode D6, the cathode of a diode D7 and one end of a resistor R36, the other end of the resistor R36 is connected to the other end of the input end of the transformer circuit and one end of a resistor R53, the other end of the resistor R53 is connected to one end of a resistor R54, the other end of the resistor R54 is connected to one end of a capacitor C8, the anode of the diode D6 and the anode of the diode D7 are respectively connected to the output end of the power input circuit.

2. The overcurrent protection power supply circuit according to claim 1, characterized in that: The power input circuit includes a fuse F2, a capacitor CX1, a thermistor RT1, a varistor RV1, a mutual inductance LF1, a capacitor CX2, a resistor RX1, a resistor RX2, a resistor RX3 and a resistor RX4. One end of the fuse F2 is connected to the live wire of the AC power supply, and the other end of the fuse F2 is respectively connected to one end of the capacitor CX1, one end of the varistor RV1 and a "4" terminal of the mutual inductance LF1. The "1" terminal of the mutual inductance LF1 is connected in parallel to the other end of the capacitor CX1, the other end of the varistor RV1 and one end of the thermistor RT1. The other end of the resistor RT1 is connected to the neutral line of the AC power supply, the mutual inductance LF1 "3" terminal is connected in parallel to one end of the capacitor CX2, one end of the resistor RX1, one end of the resistor RX2, the positive electrode of the diode D7 and one end of the input end of the rectifier and filter circuit, the mutual inductance LF1 "2" terminal is connected in parallel to the other end of the capacitor CX2, one end of the resistor RX3, one end of the resistor RX4, the positive electrode of the diode D6 and the other end of the input end of the rectifier and filter circuit, and the other end of the resistor RX1 and the other end of the resistor RX2 are connected to the other end of the resistor RX3 and the other end of the resistor RX4.

3. The overcurrent protection power supply circuit according to claim 1, characterized in that: The rectifier and filter circuit includes a mutual inductance LF2b, a bridge rectifier BD1, a capacitor EC1, a capacitor C13, a resistor R14, a resistor R12, a resistor R13, a resistor R11, a resistor R15, a resistor R16, a capacitor C2, a resistor R44, a resistor R45, a capacitor C6 and a diode D1. The mutual inductance LF2b "2" terminal is connected to the positive electrode of the diode D6, the mutual inductance LF2b "3" terminal is connected to the positive electrode of the diode D7, the mutual inductance LF2b "1" terminal is connected to the bridge rectifier BD1 "4" terminal, the mutual inductance LF2b "4" terminal is connected to the bridge rectifier BD1 "2" terminal, the bridge rectifier BD1 "1" terminal is grounded, and the bridge rectifier BD1 "3" terminal is connected in parallel to one end of the capacitor EC1 and the resistor D7. One end of capacitor C13, one end of resistor R14, one end of resistor R12, one end of resistor R13, one end of capacitor C2, one end of resistor R44 and one end of the input end of the transformer circuit, the other end of capacitor EC1 and the other end of capacitor C13 are grounded, the other end of resistor R14, the other end of resistor R12, the other end of resistor R13 and the other end of capacitor C2 are connected to one end of resistor R11, one end of resistor R15 and one end of resistor R16, the other end of resistor R11, the other end of resistor R15 and the other end of resistor R16 are connected to the cathode of diode D1, the anode of diode D1 is connected to the drain of NMOS tube Q1, the other end of resistor R44 is connected to one end of resistor R45, the other end of resistor R45 is connected to one end of capacitor C6, and the other end of capacitor C6 is grounded.

4. The overcurrent protection power supply circuit according to claim 1, characterized in that: The transformer circuit includes a transformer T1, wherein a "2" terminal of the transformer T1 is connected to the drain of the NMOS tube Q1, a "1" terminal of the transformer T1 is connected to the output end of the rectifier and filter circuit, a "3" terminal of the transformer T1 is connected to the input end of the voltage stabilization circuit, and a "4" terminal of the transformer T1 is grounded.

5. The overcurrent protection power supply circuit according to claim 1, characterized in that: The voltage stabilizing circuit comprises a transformer output voltage stabilizing circuit and an output voltage voltage stabilizing circuit, the input end of the transformer output voltage stabilizing circuit is connected to the output end of the transformer circuit, and the output end of the transformer output voltage stabilizing circuit is connected to the input end of the output voltage stabilizing circuit and the input end of the indication output circuit.

6. The overcurrent protection power supply circuit according to claim 5, characterized in that: The transformer output voltage stabilizing circuit includes a diode ZD2, a capacitor C1, a resistor R20, a resistor R19, a voltage regulator D6 and a voltage regulator D6a. The positive electrode of the diode ZD2, one end of the capacitor C1, the positive electrode of the voltage regulator D6 and the positive electrode of the voltage regulator D6a are connected to one end of the output end of the transformer circuit. The other end of the capacitor C1 is connected to one end of the resistor R20 and one end of the resistor R19. The other end of the resistor R20 and the other end of the resistor R19 are connected to the negative electrode of the diode ZD2, the negative electrode of the voltage regulator D6, the negative electrode of the voltage regulator D6a and the input end of the output voltage stabilizing circuit and the input end of the indication output circuit.

7. The overcurrent protection power supply circuit according to claim 5, characterized in that: The output voltage stabilizing circuit includes a resistor R30, a resistor R21, a resistor R27, a resistor R22, an optical coupler U3, a resistor R69, a resistor R70, a resistor R9, a capacitor C10, a resistor R24, a capacitor C7, a voltage regulator U1 and a resistor R25. One end of the resistor R30 and one end of the resistor R27 are connected to the output end of the transformer output stabilizing circuit. The other end of the resistor R30 is connected to one end of the resistor R21. The other end of the resistor R21 is connected in parallel to the "2" terminal of the optical coupler U3 and one end of the resistor R22. The "4" terminal of the optical coupler U3 and the other end of the resistor R22 are connected to the resistor R24. One end, one end of capacitor C7 and the "2" terminal of the voltage regulator U1, the other end of resistor R27 is connected in parallel to one end of capacitor C10, the other end of capacitor C7, one end of resistor R25 and the "3" terminal of the voltage regulator U1, the other end of resistor R24 ​​is connected to the other end of capacitor C10, the other end of resistor R25 and the "1" terminal of the voltage regulator U1 are grounded, the "1" terminal of the optocoupler U3 is connected in parallel to one end of resistor R9, one end of resistor R70 and one end of resistor R69, the other end of resistor R9, the other end of resistor R70 and the "3" terminal of the optocoupler U3 are grounded, and the other end of resistor R69 is connected to the "2" terminal of the chip U2.

8. The overcurrent protection power supply circuit according to claim 1, characterized in that: The indication output circuit includes an inductor L1, a capacitor EC4, a capacitor EC3, a capacitor EC2, a mutual inductor LF3, a resistor R2a and an LED1. One end of the inductor L1, one end of the capacitor EC4 and one end of the capacitor EC3 are connected to the output end of the voltage stabilizing circuit. One end of the capacitor EC2 and the "4" terminal of the mutual inductor LF3 are connected to the other end of the inductor L1. The other end of the capacitor EC4, the other end of the capacitor EC3, the other end of the capacitor EC2 and the mutual inductor LF3 "1" terminal are grounded. The mutual inductor LF3 "3" terminal is connected to one end of the resistor R2a and the positive pole of the output end. The other end of the resistor R2a is connected to the positive pole of LED1. The mutual inductor LF3 "2" terminal is grounded together with the negative pole of LED1 and the negative pole of the output end.

9. The overcurrent protection power supply circuit according to claim 1, characterized in that: The chip U2 is OB5283.

10. The overcurrent protection power supply circuit according to claim 7, characterized in that: The optical coupler U3 is an optical coupler of model 817C.

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