A low-power feedback switching power supply

Abstract

The utility model discloses a low -power feedback switching power supply relates to the field of electronic circuit. Including input module, control module, voltage transformation module, feedback module and output module. Input module contains lightning protection temperature control and filter rectifier circuit, realizes the lightning protection, filter and rectification to external power supply, control module integration starts, the feedback of original side, overcurrent monitoring and switching circuit, is the control core of power supply, voltage transformation module passes through transformer and peak current absorption circuit, realizes the safe transformation of voltage, feedback module utilizes the combination of photocoupler and voltage stabilizer, real -time acquisition output voltage and feedback to control module, output module adopts synchronous rectifier circuit, and cooperates filter capacitor and common mode inductance, realizes high -efficient rectification and filter. The utility model discloses through synchronous rectification technology reduction conduction loss, combines the adaptive feedback system fast adjustment duty cycle, and the power efficiency and output voltage stability are improved significantly, have high reliability, low loss, response speed fast and so on advantage.

Description

Technical Field

[0001] This utility model relates to an electronic circuit, and more particularly to a low-power feedback switching power supply. Background Technology

[0002] Switching power supplies, as core power supply components for electronic devices, are widely used in communications, consumer electronics, industrial control, and other fields. Their performance stability directly affects the operational reliability of terminal equipment. Traditional switching power supplies are prone to problems such as unstable output voltage and excessive ripple noise when faced with mains voltage fluctuations, load changes, or external electromagnetic interference, which may lead to equipment failure or shortened lifespan in severe cases.

[0003] In existing technologies, transformer modules mostly rely on diodes for secondary rectification, resulting in high conduction losses, especially in low-voltage, high-current scenarios. Furthermore, the timing of the switching transistors is out of phase with the transformer's secondary voltage, leading to low rectification efficiency. In addition, the peak current generated during transformer switching is not effectively absorbed, causing energy loss and potentially triggering circuit oscillations or component damage. Traditional switching power supplies typically employ simple voltage sampling and duty cycle adjustment mechanisms, resulting in slow response times and limited adjustment accuracy, making it difficult to achieve fast and stable output under complex operating conditions. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a switching power supply with higher efficiency and more stable voltage.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows:

[0006] A low-power feedback switching power supply, the key technology of which includes an input module, a control module, a transformer module, a feedback module and an output module;

[0007] The input terminal of the input module is connected to an external power source; the output terminal of the input module is connected to the input terminal of the control module and the first input terminal of the transformer module; the output terminal of the control module is connected to the second input terminal of the transformer module; the first and second output terminals of the transformer module are connected to the output module.

[0008] Preferably, the input module includes an input port, a surge protection and temperature control circuit, and a filter and rectifier circuit; the input port includes an L terminal and an N terminal; the surge protection and temperature control circuit includes a fuse F1, a temperature control resistor NTC1, and a varistor VR1; wherein, F1 is connected in series at the L terminal, NTC1 is connected in series at the N terminal, and VR1 is connected in parallel between F1 and NTC1 before connecting to the filter and rectifier circuit; the filter and rectifier circuit includes a filter capacitor CX1, a rectifier bridge BD1, a common film resistor LF1, and a filter capacitor EC5; CX1 is connected in parallel between F1 and NTC1, and F1 is connected to pin 2 of BD1, and NTC1 is connected to pin 1 of BD1; the output of BD1 is connected in parallel with EC5 through LF1, and the positive terminal of EC5 is used as the output of the input module.

[0009] Preferably, the control module includes a startup circuit, a primary-side feedback circuit, an overcurrent monitoring circuit, and a switching circuit;

[0010] The input terminal of the startup circuit is connected to the output terminal of the input module. Series resistors R40 and R41 are then connected to the VDD pin of control chip U3, capacitor C1, the positive terminal of EC1, and the negative terminal of diode D2, respectively. The positive terminal of D2 is connected to port 1 of the auxiliary winding of T1 via series resistors R7 and R11. Port 2 of the auxiliary winding, the negative terminal of EC1, and the other end of C1 are grounded. Port 1 of the auxiliary winding is connected to the SEL pin of U3 and grounded. The primary-side feedback circuit includes the transistor portion of optocoupler U2, with U2's collector connected in series with resistor R1. 7. Connect the FB pin of U3; capacitors C6 and C2 are connected in parallel between the collector and emitter of U2; the emitter of U2 is grounded; the switching circuit includes a variable resistor R13 connected to the drain of MOSFET Q1; a resistor R14 is connected to the positive terminal of D3; the other end of R14 and the other end of R13 are connected to the GATE pin of U3; the source of Q1 is grounded through a protective resistor; the overcurrent monitoring circuit includes a resistor R15 connected in parallel between the gate and source of Q1, R12 connected to one end of R15, and the CS pin of U3 connected to the other end of R12.

[0011] Preferably, the transformer module includes the primary winding, secondary winding, and peak current absorption circuit of transformer T1;

[0012] The spike current absorption circuit is located between the output terminal of the input module and the 4-port of the transformer T1.

[0013] Preferably, the feedback module includes an input terminal VHV, a diode portion of optocoupler U2, and a voltage regulator U6; VHV is connected to resistor R44, the negative terminal of Zener diode D6, and resistor R21; the other end of R44 and the positive terminal of D6 are connected to the positive terminal of the diode portion of U2 through resistor R39; the other end of R21 is connected to the reference voltage terminal of U6 and grounded; the negative terminal of the diode portion of U2 is connected to the negative terminal of U6; and the positive terminal of U6 is grounded.

[0014] Preferably, the output module includes a rectifier filter circuit, a light-emitting diode LED1, a positive output terminal V+, and a negative output terminal V-.

[0015] The rectifier and filter circuit includes a synchronous rectifier circuit, a filter capacitor, a voltage divider resistor, a bidirectional breakdown diode, and a common-mode inductor. In the synchronous rectifier circuit, the GND pin, VDD pin, RW pin of U5 and the source of D1 are connected to the first output terminal of the transformer module. The drain of D1 is connected to the VO pin and HV pin of U5. The gate of D1 is connected to the GATE pin. The source of D1 is connected to the V+ terminal. Between V+ and V-, capacitors EC2, EC4, C11, resistor R37, diode ESD1, LED1, and common-mode inductor L1 are connected in parallel.

[0016] The beneficial effects of adopting the above technical solution are as follows:

[0017] In this invention, a synchronous rectification circuit is used to control the switching and conduction of the MOSFET, replacing the traditional diode rectification. At the same time, the low on-resistance of the MOSFET reduces power loss. Combined with precise drive timing control, the power efficiency and reliability are significantly improved.

[0018] This invention utilizes a feedback system combining an optocoupler and a voltage regulator to capture voltage fluctuations in real time and quickly adjust the input duty cycle of the voltage, thereby achieving negative feedback regulation and ensuring the stability of the output voltage. Attached Figure Description

[0019] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0020] Figure 1 This is a circuit diagram of a low-power feedback switching power supply proposed in this utility model. Detailed Implementation

[0021] To make the above-mentioned objectives, features, and advantages of this utility model more apparent and understandable, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0022] like Figure 1 A low-power feedback switching power supply includes an input module, a control module, a transformer module, a feedback module, and an output module.

[0023] The input module serves as the interface between the power system and the external power supply, and features surge protection, temperature control, and filtering / rectification functions. It includes an input port, a surge protection and temperature control circuit, and a rectifier / filter circuit. The input port includes an inductor (L) terminal and a neutral (N) terminal. The surge protection and temperature control circuit includes a fuse F1, a temperature control resistor NTC1, and a varistor VR1. F1 is connected in series at the inductor (L) terminal, NTC1 is connected in series at the neutral (N) terminal, and VR1 is connected in parallel between F1 and NTC1 before connecting to the filter / rectifier circuit. This surge protection and temperature control circuit effectively handles abnormal conditions such as lightning strikes and overvoltage, protecting the safety of subsequent circuit components. The filtering and rectifier circuit includes a filter capacitor CX1, a rectifier bridge BD1, a common film resistor LF1, and a filter capacitor EC5. CX1 is connected in parallel between F1 and NTC1, with F1 connected to pin 2 of BD1 and NTC1 connected to pin 1 of BD1. The output of BD1 is connected in parallel with EC5 through LF1, and the positive terminal of EC5 is used as the output terminal of the input module. CX1 acts as a preliminary filter between F1 and NTC1. The rectifier bridge BD1 converts the input AC power into DC power. The common film resistor LF1 further suppresses electromagnetic interference. The filter capacitor EC5 smooths and filters the rectified DC power, and finally, the positive terminal of EC5 is used as the output terminal of the input module, providing a stable DC power input for subsequent modules.

[0024] The control module is the core of the power supply, responsible for key functions such as feedback regulation, overcurrent monitoring, and switching control. It includes a startup circuit, a primary-side feedback circuit, an overcurrent monitoring circuit, and a switching circuit. The input terminal of the startup circuit is connected to the output terminal of the input module. Series resistors R40 and R41 are then connected to the VDD pin of control chip U3, the positive terminal of capacitor C1 and EC1, and the negative terminal of diode D2, respectively. The positive terminal of D2 is connected to port 1 of the auxiliary winding of T1 via series resistors R7 and R11. Port 2 of the auxiliary winding, the negative terminal of EC1, and the other end of C1 are grounded. Port 1 of the auxiliary winding is connected to the SEL pin of U3 and grounded. The primary-side feedback circuit includes the transistor section of optocoupler U2. The collector of U2 is connected in series with resistor R17 and then connected to the FB pin of U3; capacitors C6 and C2 are connected in parallel between the collector and emitter of U2; the emitter of U2 is grounded; the switching circuit includes the drain of MOSFET Q1 connected to variable resistor R13; the positive terminal of D3 is connected to resistor R14; the other end of R14 and the other end of R13 are connected to the GATE pin of U3; the source of Q1 is grounded through a protective resistor; the overcurrent monitoring circuit includes resistor R15 connected in parallel between the gate and source of Q1, R12 connected to one end of R15, and the CS pin of U3 connected to the other end of R12.

[0025] After the input module is powered on, the startup circuit provides a startup voltage to the VDD pin of the control chip U3 through series resistors R40 and R41, while simultaneously charging capacitors C1 and EC1 and connecting diode D2. Diode D2, in conjunction with the auxiliary winding, maintains the power supply to U3 after the circuit starts up. The primary-side feedback circuit feeds back the voltage or current information at the output terminal to the FB pin of the control chip U3 through the transistor section of optocoupler U2, achieving precise regulation of the power output and ensuring output stability. The switching circuit uses MOSFET Q1 as its core. Its drain is connected to resistor R13, its source is grounded through a protection resistor, and its gate is connected to the GATE pin of U3 through resistors R13 and R14. U3 controls the conduction and cutoff of Q1, thereby controlling the operation of the transformer module. The overcurrent monitoring circuit monitors the current of Q1 in real time through resistor R15 connected in parallel between the gate and source of Q1, as well as R12 connected to it and the CS pin of U3. When the current exceeds the set threshold, U3 takes timely protective measures to prevent the circuit from being damaged due to overcurrent.

[0026] The transformer module includes the primary winding, secondary winding, and peak current absorption circuit of transformer T1. Transformer T1 transforms the voltage, converting the DC voltage provided by the input module into the required AC voltage, which is then output through the secondary winding. The peak current absorption circuit is located between the output terminal of the input module and the four ports of transformer T1. It absorbs the peak current generated by the transformer during switching, preventing damage to other components in the circuit and improving the reliability and stability of the power supply.

[0027] The feedback module includes an input terminal VHV, the diode section of optocoupler U2, and a voltage regulator U6. VHV is connected to resistor R44, the cathode of the Zener diode D6, and resistor R21. The other end of R44 and the anode of D6 are connected to the anode of the diode section of U2 through resistor R39. The other end of R21 is connected to the reference voltage terminal of U6 and grounded. The cathode of the diode section of U2 is connected to the cathode of U6. The anode of U6 is grounded.

[0028] The input terminal VHV of the feedback module collects voltage information from the output module. When the output voltage changes, the voltage of VHV also changes accordingly. The output voltage controls the internal resistance of the voltage regulator U4. When the voltage does not match the standard output voltage, the brightness of U2 changes, causing a change in the current at the U2 transistor, which in turn changes the voltage at the FB pin, ultimately changing the duty cycle of the signal generated by the GATE pin, thereby changing the input voltage of the transformer module. In specific implementation, when the output voltage is less than the standard voltage, the reference terminal voltage of U6 decreases, the internal resistance of U6 increases, the current flowing through U2 decreases, the brightness of the light weakens, the conduction degree of the U2 transistor decreases, the voltage at FB changes, the duty cycle of the output signal at the GATE increases, the energy stored on the input side of the transformer T1 increases, driving the voltage of subsequent circuits to rise, and vice versa, realizing voltage feedback regulation, and ultimately achieving a stable output of rated DC voltage.

[0029] The output module includes a rectifier and filter circuit, LED1, a positive output terminal V+, and a negative output terminal V-. The rectifier and filter circuit includes a synchronous rectifier circuit, a filter capacitor, a voltage divider resistor, a bidirectional breakdown diode, and a common-mode inductor. In the synchronous rectifier circuit, the GND, VDD, and RW pins of U5 and the source of D1 are connected to the first output terminal of the transformer module. The drain of D1 is connected to the VO and HV pins of U5. The gate of D1 is connected to the GATE pin. The source of D1 is connected to the V+ terminal. Capacitors EC2, EC4, and C11, resistor R37, diode ESD1, LED1, and common-mode inductor L1 are connected in parallel between V+ and V-.

[0030] The output voltage of the secondary winding of the transformer module is input to the synchronous rectification circuit of the output module. In the synchronous rectification circuit, MOSFET D1 acts as the rectifier, its gate driven by the GATE signal from the control module to achieve synchronous rectification. Compared to traditional diode rectification, this significantly reduces conduction losses and improves power efficiency. The rectified pulsating DC voltage is first smoothed by filter capacitors EC2, EC4, and C11 to filter out high-frequency ripple. Common-mode inductor L1 is connected in series in the output circuit to suppress common-mode noise and improve the electromagnetic compatibility of the output power supply. A bidirectional breakdown diode ESD1 is connected in parallel between V+ and V-. When a momentary overvoltage occurs at the output terminal, ESD1 quickly conducts and discharges, protecting the load and internal circuitry. Resistor R37 is used for voltage division or load matching. Simultaneously, the output voltage is acquired through the input VHV of the feedback module for closed-loop feedback regulation. A light-emitting diode LED1 is connected in parallel at the output terminal. When the output voltage is normal, LED1 illuminates, visually indicating the power supply's operating status.

[0031] The above description of the disclosed embodiments enables those skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A low-power feedback switching power supply, characterized in that, It includes an input module, a control module, a transformer module, a feedback module, and an output module; The input terminal of the input module is connected to an external power source; the output terminal of the input module is connected to the input terminal of the control module and the first input terminal of the transformer module; the output terminal of the control module is connected to the second input terminal of the transformer module; the first and second output terminals of the transformer module are connected to the output module.

2. The low-power feedback switching power supply according to claim 1, characterized in that, The input module includes an input port, a surge protection and temperature control circuit, and a filtering and rectifier circuit. The input port includes an L terminal and an N terminal. The surge protection and temperature control circuit includes a fuse F1, a temperature control resistor NTC1, and a varistor VR1. The fuse F1 is connected in series at the L terminal, the temperature control resistor NTC1 is connected in series at the N terminal, and the varistor VR1 is connected in parallel between the fuse F1 and the temperature control resistor NTC1 before connecting to the filtering and rectifier circuit. The filtering and rectifier circuit includes a filter capacitor CX1, a rectifier bridge BD1, a common film resistor LF1, and a filter capacitor EC5. The filter capacitor CX1 is connected in parallel between the fuse F1 and the temperature control resistor NTC1, and the fuse F1 is connected to pin 2 of the rectifier bridge BD1. The temperature control resistor NTC1 is connected to pin 1 of the rectifier bridge BD1. The output terminal of the rectifier bridge BD1 is connected in parallel with the filter capacitor EC5 through the common film resistor LF1, and the positive terminal of the filter capacitor EC5 is used as the output terminal of the input module.

3. The low-power feedback switching power supply according to claim 1, characterized in that, The control module includes a startup circuit, a primary-side feedback circuit, an overcurrent monitoring circuit, and a switching circuit. The input terminal of the startup circuit is connected to the output terminal of the input module. Series resistors R40 and R41 are then connected to the VDD pin of control chip U3, the positive terminal of capacitor C1 and EC1, and the negative terminal of diode D2, respectively. The positive terminal of diode D2 is connected to port 1 of the auxiliary winding of transformer T1 via series resistors R7 and R11. Port 2 of the auxiliary winding, the negative terminal of capacitor EC1, and the other end of capacitor C1 are grounded. Port 1 of the auxiliary winding is connected to the SEL pin of control chip U3 and grounded. The primary-side feedback circuit includes the transistor portion of optocoupler U2. The collector of optocoupler U2 is connected to control chip U3 via series resistor R17. The FB pin of 3; capacitors C6 and C2 are connected in parallel between the collector and emitter of optocoupler U2; the emitter of optocoupler U2 is grounded; the switching circuit includes a variable resistor R13 connected to the drain of MOSFET Q1; a resistor R14 connected to the cathode of diode D3; the other end of resistor R14 and the other end of resistor R13 are connected to the GATE pin of control chip U3; the source of MOSFET Q1 is grounded through a protection resistor; the overcurrent monitoring circuit includes a resistor R15 connected in parallel between the gate and source of MOSFET Q1, a resistor R12 connected to one end of resistor R15, and the CS pin of control chip U3 connected to the other end of resistor R12.

4. The low-power feedback switching power supply according to claim 1, characterized in that, The transformer module includes the primary winding, secondary winding, and peak current absorption circuit of transformer T1. The spike current absorption circuit is located between the output terminal of the input module and the 4-port of the transformer T1.

5. A low-power feedback switching power supply according to claim 1, characterized in that, The feedback module includes an input terminal VHV, the diode portion of optocoupler U2, and a voltage regulator U6. The input terminal VHV is connected to resistor R44, the cathode of Zener diode D6, and resistor R21. The other end of resistor R44 and the anode of Zener diode D6 are connected to the anode of the diode portion of optocoupler U2 via resistor R39. The other end of R21 is connected to the reference voltage terminal of voltage regulator U6 and grounded. The cathode of the diode portion of optocoupler U2 is connected to the cathode of voltage regulator U6. The anode of voltage regulator U6 is grounded.

6. A low-power feedback switching power supply according to claim 1, characterized in that, The output module includes a rectifier filter circuit, a light-emitting diode LED1, a positive output terminal V+, and a negative output terminal V-. The rectifier and filter circuit includes a synchronous rectifier circuit, a filter capacitor, a voltage divider resistor, a bidirectional breakdown diode, and a common-mode inductor. In the synchronous rectifier circuit, the GND pin, VDD pin, RW pin of U5 and the source of MOSFET D1 are connected to the first output terminal of the transformer module. The drain of MOSFET D1 is connected to the VO pin and HV pin of U5. The gate of MOSFET D1 is connected to the GATE pin. The source of MOSFET D1 is connected to the V+ terminal. Capacitors EC2, EC4, and C11, resistor R37, diode ESD1, LED1, and common-mode inductor L1 are connected in parallel between V+ and V-.

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