CN216929862U - Feedback circuit of flyback switching power supply - Google Patents

Abstract

The utility model provides a feedback circuit of a flyback switching power supply, which comprises an optical coupler, a three-terminal voltage regulator, a second resistor, a first capacitor, a fifth resistor and a sixth resistor. The first pin of the optical coupler is connected with the output end of the power supply, the second pin of the optical coupler is connected with the cathode of the three-terminal voltage regulator, and the anode of the three-terminal voltage regulator is grounded. The feedback end of the three-end voltage stabilizing source is connected with the output end of the power supply through a fifth resistor and is grounded through a sixth resistor. The first capacitor and the second resistor are connected in parallel for filtering, and two ends of the second resistor are respectively connected with a first pin and a second pin of the optical coupler. The input end of the optical coupler is connected with the first capacitor in parallel to absorb disturbance ripples in the circuit, so that burst interference signals when the load output by the power supply changes are prevented from being transmitted to the power supply management chip through the optical coupler, misoperation of the power supply management chip is prevented, and the stability of the output power supply is ensured.

Description

Feedback circuit of flyback switching power supply

[ technical field ] A

The utility model relates to the technical field of feedback circuits, in particular to a feedback circuit of a flyback switching power supply.

[ background ] A method for producing a semiconductor device

As is known, a switching power supply is configured to perform rectification and filtering processing on an input power supply and then output the rectified power supply from a transformer, wherein the output voltage is fed back to a power management chip through a feedback circuit, and the power management chip controls the on/off or the magnitude of the output power supply of the transformer by controlling a power switch, so as to achieve a constant voltage effect. However, in the existing feedback circuit, when the output load of the power supply changes, interference is easily received, and further, an error feedback may occur, so that the power supply management chip works erroneously and the stability of the power supply output is affected.

Accordingly, the prior art is in need of improvement and development.

[ Utility model ] content

The utility model aims to provide a feedback circuit of a flyback switching power supply, which is used for solving the problem that the feedback circuit in the conventional switching power supply is easily interfered.

The technical scheme of the utility model is as follows: a feedback circuit of a flyback switching power supply comprises an optical coupler, a three-terminal voltage regulator, a second resistor, a first capacitor, a fifth resistor and a sixth resistor;

a first pin of the optical coupler is connected with a power output end, a second pin of the optical coupler is connected with a cathode of the three-terminal voltage regulator, and an anode of the three-terminal voltage regulator is grounded; the feedback end of the three-end voltage-stabilizing source is connected with the output end of the power supply through the fifth resistor and is grounded through the sixth resistor; the first capacitor and the second resistor are connected in parallel and used for filtering, and two ends of the second resistor are respectively connected with the first pin and the second pin of the optical coupler.

Further, the feedback circuit further comprises a first resistor, and the first pin of the optocoupler is connected to the power output terminal through the first resistor.

Further, the feedback circuit further includes: the third resistor, a third capacitor connected in series with the third resistor, and a second capacitor;

and the second pin of the optical coupler and the cathode of the three-terminal voltage regulator are respectively connected with two ends of a second capacitor, and two ends of the third resistor, which are connected with the third capacitor in series, are respectively connected with two ends of the second capacitor.

Further, the feedback circuit further comprises a fourth resistor connected in parallel with the sixth resistor.

Further, the three-terminal voltage regulator is an LM431 model chip.

The utility model has the beneficial effects that: compared with the prior art, the input end of the optical coupler is connected with the first capacitor in parallel to absorb disturbance ripples in the circuit, so that burst interference signals when the load output by the power supply changes are prevented from being transmitted to the power supply management chip through the optical coupler, misoperation of the power supply management chip is prevented, and the stability of the output power supply is ensured.

[ description of the drawings ]

Fig. 1 is a schematic circuit diagram of the present invention.

[ detailed description ] embodiments

The utility model is further described with reference to the following figures and embodiments.

Referring to fig. 1, a feedback circuit of a flyback switching power supply according to an embodiment of the present invention is shown.

The feedback circuit of the flyback switching power supply comprises an optical coupler U1, a three-terminal voltage regulator U2, a second resistor R2, a first capacitor C1, a fifth resistor R5 and a sixth resistor R6. The first pin of the optical coupler U1 is connected with the power output end, the second pin is connected with the cathode of the three-terminal voltage regulator U2, and the anode of the three-terminal voltage regulator U2 is grounded. The feedback end of the three-terminal voltage regulator U2 is connected with the power output end through a fifth resistor R5 and is grounded through a sixth resistor R6. The first capacitor C1 is connected in parallel with the second resistor R2 for filtering, and two ends of the second resistor R2 are respectively connected to the first pin and the second pin of the optocoupler U1.

According to the utility model, a reference voltage with a certain value can be provided by matching the three-terminal voltage regulator U2 with the sixth resistor R6, and the voltage difference between the first pin and the second pin of the optical coupler U1 is matched, so that the conduction of the optical coupler U1 is realized and voltage feedback is provided for the power management chip when the power output is too large, the power output of the transformer is reduced by the power management chip through the power switch, and no feedback exists when the output power is too small, so that the power output of the transformer is increased by the power management chip through the power switch, the feedback effect of the feedback circuit is realized, and the stability of the output power is realized. In addition, the input end of the optocoupler U1 is connected with the second resistor R2 in parallel, so that the current threshold can be raised, the optocoupler U1 is prevented from being conducted mistakenly, and the anti-interference performance of the optocoupler U1 can be improved. In addition, the first capacitor C1 is connected in parallel to the input end of the optical coupler U1, disturbance ripples in the circuit are absorbed, burst interference signals when the load output by the power supply changes are prevented from being transmitted to the power supply management chip through the optical coupler U1, misoperation of the power supply management chip is prevented, stability of the output power supply is guaranteed, and the problem that the feedback circuit in the existing switching power supply is easily interfered by the burst interference signals caused by load changes to cause misoperation of the power supply management chip is solved.

Specifically, in one embodiment, the three-terminal regulator U2 is a chip of model LM 431.

In one embodiment, to limit the current to the input of the optocoupler U1, the feedback circuit further includes a first resistor R1, and the first pin of the optocoupler U1 is connected to the power supply output terminal through the first resistor R1.

In one embodiment, to provide the required feedback loop compensation to the optocoupler U1 to stabilize the control loop, the feedback circuit further includes: a third resistor R3, a third capacitor C3 connected in series with the third resistor R3, and a second capacitor C2. The second pin of the optical coupler U1 and the cathode of the three-terminal voltage regulator U2 are respectively connected to two ends of a second capacitor C2, and two ends of a third resistor R3 connected in series with a third capacitor C3 are respectively connected to two ends of a second capacitor C2.

In one embodiment, the feedback circuit further includes a fourth resistor R4 connected in parallel with the sixth resistor R6 for outputting a desired reference voltage from a three-terminal regulator U2.

While the foregoing is directed to embodiments of the present invention, it will be understood by those skilled in the art that various changes may be made without departing from the spirit and scope of the utility model.

Claims (5)

1. A feedback circuit of a flyback switching power supply is characterized by comprising an optical coupler, a three-terminal voltage regulator, a second resistor, a first capacitor, a fifth resistor and a sixth resistor;

a first pin of the optical coupler is connected with a power output end, a second pin of the optical coupler is connected with a cathode of the three-terminal voltage regulator, and an anode of the three-terminal voltage regulator is grounded; the feedback end of the three-end voltage-stabilizing source is connected with the output end of the power supply through the fifth resistor and is grounded through the sixth resistor; the first capacitor and the second resistor are connected in parallel and used for filtering, and two ends of the second resistor are respectively connected with the first pin and the second pin of the optical coupler.

2. The feedback circuit of the flyback switching power supply of claim 1, further comprising a first resistor, wherein the first pin of the optocoupler is coupled to the power supply output via the first resistor.

3. The feedback circuit of the flyback switching power supply of claim 2, wherein the feedback circuit further comprises: the third resistor, a third capacitor connected in series with the third resistor, and a second capacitor;

and the second pin of the optical coupler and the cathode of the three-terminal voltage regulator are respectively connected with two ends of a second capacitor, and two ends of the third resistor, which are connected with the third capacitor in series, are respectively connected with two ends of the second capacitor.

4. The feedback circuit of the flyback switching power supply of claim 3, further comprising a fourth resistor in parallel with the sixth resistor.

5. The feedback circuit of the flyback switching power supply of claim 4, wherein the three-terminal regulator is a chip of type LM 431.

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