CN-121978382-A - Reverse current detection circuit, forward topology structure and switching power supply

CN121978382ACN 121978382 ACN121978382 ACN 121978382ACN-121978382-A

Abstract

The application provides a reverse current detection circuit, a forward topological structure and a switching power supply, wherein the reverse current detection circuit comprises a current sensing device, a first resistor, a second resistor, a third resistor and a first diode, wherein the primary side of the current sensing device is connected with a target device in series, the first resistor is connected with the secondary side of the current sensing device in parallel, the first end of the first resistor is connected with the anode of the first diode, the cathode of the first diode is connected with the first end of the third resistor, the second end of the third resistor is connected with the first end of the second resistor, the second end of the second resistor is grounded, the second end of the third resistor outputs a first detection signal, and the first detection signal is used for comparing with a first threshold value to judge whether a branch circuit where a reverse current flows through the target device exists. The reverse current detection circuit, the forward topology structure and the switching power supply provided by the embodiment of the application are beneficial to prolonging the service life of devices in a branch circuit and avoiding the failure of the devices caused by reverse current.

Inventors

MA XINFU
LI XIULOU
WANG YUETIAN

Assignees

深圳欧陆通电子股份有限公司

Dates

Publication Date: 20260505
Application Date: 20251229

Claims (10)

1. The reverse current detection circuit is characterized by comprising a current signal sampling detection unit, wherein: the current signal sampling detection unit comprises a current sensing device, a first resistor, a second resistor, a third resistor and a first diode; The primary side of the current sensing device is connected with the target device in series, the first resistor is connected with the secondary side of the current sensing device in parallel, the first end of the first resistor is connected with the anode of the first diode, the cathode of the first diode is connected with the first end of the third resistor, the second end of the third resistor is connected with the first end of the second resistor, and the second end of the second resistor is grounded; The second end of the third resistor outputs a first detection signal, and the first detection signal is used for comparing with a first threshold value to judge whether a reverse current flows through a branch where the target device is located.
2. The reverse current detection circuit according to claim 1, further comprising a bias unit, wherein the bias unit is connected to the second end of the third resistor, and is configured to amplify the first detection signal to obtain a second detection signal, and the second detection signal is used to compare with a second threshold to determine whether a reverse current flows through a branch where the target device is located, so as to improve an anti-interference capability of the reverse current detection circuit.
3. The reverse current detection circuit of claim 2, wherein the bias unit comprises a fourth resistor, a fifth resistor, a sixth resistor, a second diode, and a first capacitor, wherein: The first end of the sixth resistor is connected with the second end of the third resistor, the second end of the sixth resistor is respectively connected with the first end of the fourth resistor, the first end of the fifth resistor and the first end of the first capacitor, the second ends of the fourth resistor and the first capacitor are grounded, the second end of the fifth resistor is connected with a power supply voltage, and the second end of the sixth resistor outputs a second detection signal.
4. The reverse current detection circuit according to claim 3, wherein the bias unit further comprises a second diode, an anode of the second diode is connected to the second end of the sixth resistor, and a cathode of the second diode is connected to the power supply voltage.
5. The reverse current detection circuit according to claim 3, wherein the second threshold value is greater than or equal to K, and K is calculated from the supply voltage, the resistance value of the second resistor, the resistance value of the fourth resistor, the resistance value of the fifth resistor, and the resistance value of the sixth resistor.
6. A reverse current detection circuit according to any one of claims 1 to 5, wherein the target device is a freewheeling switch in a rectifying circuit of a forward topology.
7. A forward topology comprising a transformer, a primary side circuit, a rectifier circuit, and a reverse current detection circuit according to any one of claims 1 to 6, wherein: The transformer comprises a primary winding and a secondary winding, the primary circuit is connected with the primary winding, the rectifying circuit is connected with the secondary winding, the rectifying circuit comprises a follow current switch, and the reverse current detection circuit is used for detecting reverse current of a branch where the follow current switch is located.
8. The forward topology of claim 7, wherein said rectifying circuit further comprises a rectifying switch, an inductance, a third capacitance, and an output load resistance, wherein: The first end of the rectifying switch is connected with the first end of the secondary winding, and the second end of the rectifying switch is connected with the negative end; The first end of the inductor is connected with the second end of the secondary winding, the second end of the inductor is connected with the positive end, the first end of the third capacitor and the first end of the output load resistor are connected with the positive end, and the second end of the third capacitor and the second end of the output load resistor are connected with the negative end.
9. The forward topology of claim 7, wherein said primary side circuit comprises a clamp switch, a clamp capacitor, a main switch, and a second capacitor, wherein: the clamping switch is connected with the clamping capacitor in series and then connected with the primary winding in parallel; The first end of the main switch is connected with the first end of the primary winding, the second end of the main switch is connected with the first end of the second capacitor, and the second end of the second capacitor is connected with the second end of the primary winding.
10. A switching power supply, comprising the forward topology of any one of claims 7 to 9 and a controller connected to a control terminal of the freewheel switch, the controller being configured to turn off the freewheel switch after determining that a reverse current flows through a branch in which the freewheel switch is located based on a detection signal provided by a reverse current detection circuit.

Description

Reverse current detection circuit, forward topology structure and switching power supply Technical Field The application relates to the technical field of electronic circuits, in particular to a reverse current detection circuit, a forward topology structure and a switching power supply. Background The forward topology circuit solves the demagnetization problem of the magnetic core of the transformer through a magnetic reset mechanism, and can realize high-efficiency and reliable direct energy transmission. In the prior art, as shown in fig. 1, a forward topology circuit of a switching power supply comprises a primary side circuit, a transformer T and a secondary side circuit, wherein the secondary side circuit comprises an inductor L and an output capacitor C1 and can be used for storing energy. In the synchronous rectification process, the main switch Q3 is turned on, the rectification switch Q2 is turned on, the follow current switch Q1 is turned off, and in the above process, the device failure condition easily occurs in the secondary side circuit. Therefore, how to solve the device failure of the forward topology circuit in the synchronous rectification process becomes an important topic to be solved in the field. Disclosure of Invention Aiming at the problems in the prior art, the embodiment of the application provides a reverse current detection circuit, a forward topology structure and a switching power supply, which can at least partially solve the problems in the prior art. In a first aspect, the present application provides a reverse current detection circuit, including a current signal sampling detection unit, wherein: the current signal sampling detection unit comprises a current sensing device, a first resistor, a second resistor, a third resistor and a first diode; The primary side of the current sensing device is connected with the target device in series, the first resistor is connected with the secondary side of the current sensing device in parallel, the first end of the first resistor is connected with the anode of the first diode, the cathode of the first diode is connected with the first end of the third resistor, the second end of the third resistor is connected with the first end of the second resistor, and the second end of the second resistor is grounded; The second end of the third resistor outputs a first detection signal, and the first detection signal is used for comparing with a first threshold value to judge whether a reverse current flows through a branch where the target device is located. Further, the reverse current detection circuit provided by the embodiment of the application further comprises a bias unit, wherein the bias unit is connected with the second end of the third resistor and is used for amplifying the first detection signal to obtain a second detection signal, and the second detection signal is used for comparing with a second threshold value to judge whether a reverse current flows through a branch where the target device is located, so that the anti-interference capability of the reverse current detection circuit is improved. Further, the bias unit includes a fourth resistor, a fifth resistor, a sixth resistor, a second diode, and a first capacitor, wherein: The first end of the sixth resistor is connected with the second end of the third resistor, the second end of the sixth resistor is respectively connected with the first end of the fourth resistor, the first end of the fifth resistor and the first end of the first capacitor, the second ends of the fourth resistor and the first capacitor are grounded, the second end of the fifth resistor is connected with a power supply voltage, and the second end of the sixth resistor outputs a second detection signal. Further, the bias unit further comprises a second diode, an anode of the second diode is connected with the second end of the sixth resistor, and a cathode of the second diode is connected with the power supply voltage. Further, the second threshold is greater than or equal to K, where K is calculated according to the supply voltage, the resistance of the second resistor, the resistance of the fourth resistor, the resistance of the fifth resistor, and the resistance of the sixth resistor. Further, the target device is a freewheel switch in a rectifying circuit of a forward topology. In a second aspect, the present application provides a forward topology, including a transformer, a primary side circuit, a rectifier circuit, and a reverse current detection circuit according to any one of the above embodiments, wherein: The transformer comprises a primary winding and a secondary winding, the primary circuit is connected with the primary winding, the rectifying circuit is connected with the secondary winding, the rectifying circuit comprises a follow current switch, and the reverse current detection circuit is used for detecting reverse current of a branch where the follow current switch is located. Further,