A primary side feedback adaptive switching power supply

Abstract

The utility model discloses a kind of primary side feedback self-adapting switching power supply, it is related to electronic circuit field. Including input, voltage transformation, control module and output port. Input module carries out lightning protection, rectification filtering pretreatment to external ac power supply;Control module takes CRE6255MDQ chip as core, realizes primary side feedback control by auxiliary winding voltage division, saves secondary feedback circuit, dynamically adjusts the duty cycle of switching tube to stabilize output;Voltage transformation module is processed after synchronous rectification and filtering, and output stable DC voltage. The utility model simplifies circuit structure by primary side feedback technology, reduces component quantity and cost, improves adaptive adjustment capability, can effectively cope with input voltage fluctuation and load variation, with overcurrent, overvoltage protection function and low-loss characteristics, suitable for the efficient stable power supply of multiple electronic equipment.

Description

Technical Field

[0001] This utility model relates to the field of electronic circuits, and in particular to a primary-side feedback adaptive 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] Traditional switching power supplies typically employ secondary feedback circuits, using numerous optocouplers for isolated feedback to achieve stable output voltage control. This approach suffers from complex circuit structures, a large number of components, and high costs. Furthermore, traditional power supplies have limited adaptive adjustment capabilities when faced with input voltage fluctuations or load changes, potentially leading to insufficient output voltage stability. Additionally, existing switching power supplies suffer from significant energy losses and insufficient reliability. Utility Model Content

[0004] The technical problem to be solved by this utility model is to provide a switching power supply with simple structure, high stability and low energy loss.

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

[0006] A primary-side feedback adaptive switching power supply, the key feature of which is that the power supply includes an input module, a transformer module, a control module, and an output port;

[0007] The input terminal of the input module is connected to an external power supply, and the output terminal of the input module is connected to the first input terminal of the transformer module and the input terminal of the control module; the output terminal of the control module is connected to the first input terminal and the second input terminal of the transformer module; the first output terminal and the second output terminal of the transformer module are connected in parallel to the output port.

[0008] Preferably, the input module includes an input port, a surge protection and temperature control circuit, and a rectifier and filter circuit; the input ports ACL and ACN are connected to an external AC power supply as input terminals of the input module; the input port ACL is connected in series with a fuse F1 and then in parallel with a varistor MOV1 between it and ACN, and is connected to the two input terminals of the rectifier bridge DB1; the output terminal of DB1 is connected to a filter capacitor and a common-mode inductor, and the filtered current is output through the positive terminal of the filter capacitor EC2.

[0009] Preferably, the control module includes a startup circuit, an auxiliary winding power supply circuit, a control circuit, and a voltage feedback circuit. The startup circuit receives the current from the output module through the input terminal of the control module and connects it to the VDD pin of the control chip U1 after a series resistor. The auxiliary winding power supply circuit connects one end of the auxiliary winding of transformer T1 to the VDD pin through a rectifier diode D2 and a resistor R7. The control circuit connects to the first and second input terminals of the transformer module through a peak current absorption circuit connected in parallel between the C pin of U1 and the input terminal of the control module. In the voltage feedback circuit, resistors R5 and R6 are connected in series between the auxiliary winding and the ground terminal, and R5 and R6 are connected through the FB pin of U1. The other end of the auxiliary winding is grounded. The CS pin of U1 is grounded.

[0010] Preferably, U1 is a CRE6255MDQ chip.

[0011] Preferably, the transformer module includes the primary winding and secondary winding of transformer T1.

[0012] Preferably, a rectifier and filter circuit is connected between the output port and the transformer module; the output port includes DC+ and DC-; the first output terminal of the transformer module is connected to capacitor C3, the D pin of U2, and the negative terminal of diode D3, respectively; the other end of C3 is grounded through resistor R12; the second output terminal of the transformer module is connected to resistor R13, the positive terminal of capacitor EC4, and DC+, respectively; the other end of R13 is connected to the positive terminal of D3, the GND pin of U2, and DC-, respectively; the negative terminal of EC4 is connected to capacitor C4 and DC-; the other end of C4 is connected to the VDD pin of U2; U2 is a dual MOS transistor integrated chip, the D pin is the built-in drain pin, and VDD is the gate pin; DC- is grounded.

[0013] The beneficial effects of adopting the above technical solution are as follows:

[0014] This invention uses a primary-side feedback circuit to achieve primary-side feedback, omitting the secondary feedback circuit, reducing the number of components and the complexity of the circuit board layout, and improving the stability of the circuit.

[0015] This invention uses auxiliary winding voltage division feedback to control the chip to monitor the secondary output voltage in real time, dynamically adjust the duty cycle of the switching transistor, adapt to input voltage fluctuations and load changes, and improve output stability.

[0016] This invention uses a synchronous rectifier chip U2 to reduce rectification losses, and works with a filter capacitor to achieve low ripple output, thereby reducing circuit energy loss and improving the stability of the output current. Attached Figure Description

[0017] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0018] Figure 1 This is a circuit diagram of a primary-side feedback adaptive switching power supply proposed in this utility model. Detailed Implementation

[0019] 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.

[0020] like Figure 1 A primary-side feedback adaptive switching power supply includes an input module, a transformer module, a control module, and an output port;

[0021] The input module connects to an external input voltage and preprocesses the input voltage to facilitate the implementation of subsequent module functions. The output terminals of the input module are connected to the transformer module and the control module respectively. The control module controls the duty cycle of the input voltage of the transformer module and performs primary-side feedback based on the feedback from the transformer module to achieve stable output. The output terminal of the transformer module is rectified and filtered before passing through the output port to obtain a stable output voltage.

[0022] The input module includes an input port, a surge protection and temperature control circuit, and a rectifier and filter circuit. Its specific structure is as follows:

[0023] Input ports ACL and ACN are connected to an external AC power supply as input terminals. ACL is connected in series with fuse F1, and a varistor MOV1 is connected in parallel with ACN to form a surge protection and temperature control circuit.

[0024] Fuse F1 is used to blow when the current is abnormal, protecting the downstream circuit. When an abnormal situation such as a short circuit or overload occurs in the circuit, causing the current to be too large, fuse F1 will blow quickly, cutting off the circuit and preventing the excessive current from damaging the subsequent rectifier bridge DB1, filter capacitor, control chip and other components.

[0025] The varistor MOV1 conducts and discharges during voltage surges to suppress overvoltage and prevent device damage. In situations such as lightning strikes or power grid switching, instantaneous voltage surges occur. At this time, the varistor MOV1 rapidly reduces its resistance, guiding the excessive voltage to ground, thereby protecting other components from overvoltage impacts and ensuring the safe and stable operation of the entire circuit.

[0026] The aforementioned surge protection output terminal is connected to the two input terminals of the rectifier bridge DB1. DB1 converts AC power to DC power, and the output terminal is connected in sequence to a filter capacitor and a common-mode inductor. After filtering, a stable DC voltage is output through the positive terminal of EC2, providing a clean DC input power supply for the transformer module and the control module.

[0027] The control module includes a startup circuit, an auxiliary winding power supply circuit, a control circuit, and a voltage feedback circuit. The core component is U1 (CRE6255MDQ chip), and the functions of each part are as follows:

[0028] Startup circuit: It receives the current from the input module through the control module input terminal, connects it to the VDD pin of the control chip U1 through a series resistor, provides the startup voltage for the chip, and triggers the initialization of the control module. When the switching power supply is first connected to the external power supply, the startup circuit starts working. It draws current from the input module, and after appropriate current limiting by the series resistor, provides the voltage required for startup to the VDD pin of the control chip U1.

[0029] Auxiliary winding power supply circuit: One end of the auxiliary winding of transformer T1 is connected to the VDD pin of U1 through rectifier diode D2 and resistor R7. When the power supply is started, the induced voltage of the auxiliary winding is rectified by D2 and current limited by R7 to provide continuous power supply for U1, replacing the startup circuit to maintain chip operation. The energy loss of the auxiliary winding power supply circuit is smaller and more stable compared with the direct power supply from the input module in the startup circuit.

[0030] Control Circuit: A spike current absorption circuit is connected in parallel between pin C of U1 and the input terminal of the control module, and is connected to the first and second input terminals of the transformer module. This circuit absorbs the spike voltage generated during switching of the switching transistor, protecting the control chip and the switching transistor, and improving circuit stability. Pin C of U1 is the drain of the internal high-voltage MOSFET. The switching frequency of the internal high-voltage MOSFET is controlled by the voltage feedback circuit and the current sampling pin, thereby controlling the duty cycle of the voltage input before the transformer module.

[0031] Voltage feedback circuit: Resistors R5 and R6 are connected in series between the auxiliary winding and the ground terminal. The FB pin of U1 is connected between R5 and R6, and the other end of the auxiliary winding is grounded. The voltage of the auxiliary winding is divided by R5 and R6, and the FB pin collects the voltage division signal, indirectly feeding back the secondary output voltage to realize primary-side feedback control. No secondary feedback circuit is needed. The voltage feedback circuit is the key part to realize primary-side feedback adaptive control. There is a certain proportional relationship between the voltage of the auxiliary winding and the secondary output voltage. By dividing the voltage of the auxiliary winding by R5 and R6, the FB pin of U3 collects this voltage division signal, which indirectly tells us about the secondary output voltage. Then the chip adjusts the control signal according to this feedback signal to achieve precise control of the output voltage, simplifying the structure and improving the adaptive adjustment capability. The CS pin of U1 is grounded for current sampling or reference ground connection. When the current is too large, the protection action of U1 is triggered.

[0032] The transformer module includes the primary winding and secondary winding of transformer T1: the primary winding receives the DC voltage from the input module and the switching signal from the control module, and transfers energy to the secondary winding through electromagnetic induction; the AC voltage output by the secondary winding is processed by the subsequent rectifier and filter circuit to realize voltage level conversion and meet the voltage requirements of the output port.

[0033] A rectifier and filter circuit is connected between the output port and the transformer module, as follows:

[0034] The first output terminal (one end of the secondary winding) of the transformer module is connected to capacitor C3, the D pin of U2, and the negative terminal of diode D3, respectively: C3 is used to filter out high-frequency noise, and R12 is grounded to form a discharge circuit to stabilize the voltage of the D pin; the second output terminal (the other end of the secondary winding) of the transformer module is connected to resistor R13, the positive terminal of capacitor EC4, and DC+, respectively: R13 is connected to the positive terminal of D3, the GND pin of U2, and DC- to form a rectification circuit; U2 is a dual MOSFET rectifier chip, and the VDD pin obtains the start-up voltage through EC4, thereby controlling the opening and closing of the D pin to achieve synchronous rectification of the output voltage and ensure a stable DC voltage output for DC+ and DC-; DC- is grounded as the output reference ground, forming a complete output circuit.

[0035] 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 primary-side feedback adaptive switching power supply, characterized in that, The power supply includes an input module, a transformer module, a control module, and an output port; The input terminal of the input module is connected to an external power supply, and the output terminal of the input module is connected to the first input terminal of the transformer module and the input terminal of the control module; the output terminal of the control module is connected to the first input terminal and the second input terminal of the transformer module; the first output terminal and the second output terminal of the transformer module are connected in parallel to the output port.

2. The primary-side feedback adaptive 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 rectifier and filter circuit. The input ports ACL and ACN are connected to an external AC power supply as the input terminals of the input module. The input port ACL is connected in series with a fuse F1 and then in parallel with a varistor MOV1 between it and ACN, and is connected to the two input terminals of the rectifier bridge DB1. The output terminal of the rectifier bridge DB1 is connected to a filter capacitor and a common-mode inductor, and the filtered current is output through the positive terminal of the filter capacitor EC2.

3. The primary-side feedback adaptive switching power supply according to claim 1, characterized in that, The control module includes a startup circuit, an auxiliary winding power supply circuit, a control circuit, and a voltage feedback circuit. The startup circuit receives the current from the output module through the input terminal of the control module and connects it to the VDD pin of the control chip U1 after a series resistor. The auxiliary winding power supply circuit connects one end of the auxiliary winding of transformer T1 to the VDD pin through a rectifier diode D2 and a resistor R7. The control circuit connects to the first and second input terminals of the transformer module through a peak current absorption circuit connected in parallel between the C pin of the control chip U1 and the input terminal of the control module. In the voltage feedback circuit, resistors R5 and R6 are connected in series between the auxiliary winding and the ground terminal, and the connection between resistors R5 and R6 is made through the FB pin of the control chip U1. The other end of the auxiliary winding is grounded. The CS pin of the control chip U1 is grounded.

4. The primary-side feedback adaptive switching power supply according to claim 3, characterized in that, The control chip U1 is a CRE6255MDQ chip.

5. The primary-side feedback adaptive switching power supply according to claim 1, characterized in that, The transformer module includes the primary winding and secondary winding of transformer T1.

6. The primary-side feedback adaptive switching power supply according to claim 1, characterized in that, A rectifier and filter circuit is connected between the output port and the transformer module; the output port includes DC+ and DC-; the first output terminal of the transformer module is connected to capacitor C3, the D pin of chip U2, and the negative terminal of diode D3, respectively; the other end of capacitor C3 is grounded through resistor R12; the second output terminal of the transformer module is connected to resistor R13, the positive terminal of capacitor EC4, and DC+, respectively; the other end of resistor R13 is connected to the positive terminal of diode D3, the GND pin of chip U2, and DC-, respectively; the negative terminal of capacitor EC4 is connected to capacitor C4 and DC-; the other end of capacitor C4 is connected to the VDD pin of chip U2; chip U2 is a dual MOS transistor integrated chip, the D pin is the built-in drain pin, and VDD is the gate pin; DC- is grounded.

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