Anti-backflow circuits and electrical equipment

Abstract

The present invention provides a backflow prevention circuit and an electrical device, comprising: a power circuit, a sampling circuit and a control circuit; the sampling circuit is connected to an input voltage Vin, and is connected to the control circuit through the power circuit, thereby controlling a PMOS tube Q1 in the control circuit. The backflow prevention circuit of the present invention has a simple structure, a reliable backflow prevention effect, and is easy to promote and apply.

Description

Technical Field

[0001] The present invention relates to the field of electronic circuits, and in particular to an anti-backflow circuit and an electrical device. Background Art

[0002] The anti-backflow circuit is used in many occasions. Its function is to ensure that each single power supply is independent of each other and does not have a backflow phenomenon. Since the diode has unidirectional conductivity, it is a natural anti-backflow circuit. However, since the forward voltage drop of the diode is relatively large, when the output current is large, the circuit loss is very large. In some charging circuits, when the input voltage is lower than the voltage of the charged battery, the battery will discharge to the input circuit through the power inductor and the internal diode of the power MOS.

[0003] For example, patent document CN110676830A discloses a current backflow prevention circuit and a smart door lock system, wherein the current backflow prevention circuit includes: a first current backflow prevention module, a boost circuit, and a second current backflow prevention module. The existing backflow prevention circuit structure is relatively complex, and its use in some low-cost devices will significantly increase the production cost, making it difficult to apply. Summary of the invention

[0004] In view of the defects in the prior art, an object of the present invention is to provide an anti-backflow circuit and an electrical device.

[0005] According to the present invention, a backflow prevention circuit includes: a power circuit, a sampling circuit and a control circuit;

[0006] The sampling circuit is connected to an input voltage Vin and is connected to the control circuit via the power circuit, thereby controlling the PMOS tube Q1 in the control circuit.

[0007] Preferably, the sampling circuit comprises a resistor R10 and a resistor R13 connected in series, one end of the resistor R10 is connected to the input voltage Vin, and the other end is grounded through the resistor R13.

[0008] Preferably, the power circuit comprises: a resistor R3, a comparator U2 and an optical coupler U10;

[0009] One end of the resistor R3 is connected to the input voltage Vin, and the other end is connected to the anode of the light emitting diode in the optocoupler U10, the anode of the comparator U2 is connected between the resistor R13 and the ground, the cathode of the comparator U2 is connected to the cathode of the light emitting diode in the optocoupler U10, and the reference electrode of the comparator U2 is connected between the resistor R10 and the resistor R13;

[0010] The emitter of the phototransistor in the optocoupler U10 is grounded, and the collector of the phototransistor in the optocoupler U10 is connected to the control circuit.

[0011] Preferably, the control circuit comprises: a resistor R1, a resistor R2, a resistor R6 and the PMOS tube Q1;

[0012] One end of the resistor R6 is connected to the optical coupler U10, and one end of the resistor R1 and the resistor R2 are connected in parallel to the other end of the resistor R6;

[0013] The other end of the resistor R2 is connected to the battery voltage Vcharge;

[0014] The other end of the resistor R1 is connected to the gate of the PMOS transistor Q1 , the source of the PMOS transistor Q1 is connected to the battery voltage Vcharge, and the drain of the PMOS transistor Q1 is connected to the input voltage Vin.

[0015] The electrical equipment provided according to the present invention includes any one of the above-mentioned backflow prevention circuits.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The anti-backflow circuit of the present invention has a simple structure, a reliable anti-backflow effect, and is easy to promote and apply.

[0018] When the input voltage of VIN is greater than the turn-on voltage point, the MOS turns on the input current and passes through the MOS channel to the subsequent circuit.

[0019] When the input voltage is lower than the turn-on voltage point, the MOS is turned off to prevent the battery from flowing back to the VIN terminal.

[0020] Adjusting the sampling circuit parameters can change the MOS turn-on voltage point. It can be set according to the battery voltage and input voltage. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Other features, objects and advantages of the present invention will become more apparent from the detailed description of non-limiting embodiments made with reference to the following drawings:

[0022] Figure 1 It is a circuit structure diagram of the anti-backflow circuit of the present invention. DETAILED DESCRIPTION

[0023] The present invention is described in detail below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the present invention, but are not intended to limit the present invention in any form. It should be noted that, for those of ordinary skill in the art, several changes and improvements can also be made without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

[0024] like Figure 1As shown, the invention provides an anti-backflow circuit, comprising: a power circuit, a sampling circuit and a control circuit. The sampling circuit is connected to an input voltage Vin, and is connected to the control circuit through the power circuit, thereby controlling the PMOS tube Q1 in the control circuit.

[0025] The sampling circuit includes a resistor R10 and a resistor R13 connected in series. One end of the resistor R10 is connected to the input voltage Vin, and the other end is grounded through the resistor R13.

[0026] The power circuit includes: resistor R3, comparator U2 and optocoupler U10. One end of resistor R3 is connected to input voltage Vin, and the other end is connected to the anode of the light-emitting diode in optocoupler U10. The anode of comparator U2 is connected between resistor R13 and ground, the cathode of comparator U2 is connected to the cathode of the light-emitting diode in optocoupler U10, and the reference electrode of comparator U2 is connected between resistor R10 and resistor R13. The emitter of the phototransistor in optocoupler U10 is grounded, and the collector of the phototransistor in optocoupler U10 is connected to the control circuit.

[0027] The control circuit includes: a resistor R1, a resistor R2, a resistor R6 and a PMOS tube Q1. One end of the resistor R6 is connected to the optocoupler U10, and one end of the resistor R1 and the resistor R2 are connected in parallel to the other end of the resistor R6. The other end of the resistor R2 is connected to the battery voltage Vcharge. The other end of the resistor R1 is connected to the gate of the PMOS tube Q1, the source of the PMOS tube Q1 is connected to the battery voltage Vcharge, and the drain of the PMOS tube Q1 is connected to the input voltage Vin.

[0028] The working principle of the present invention is as follows:

[0029] The voltage sampling circuit composed of resistors R10 and R13 collects the input voltage Vin.

[0030] When the Vin terminal voltage is greater than 15V, the cathode of the comparator U2 (TL431) is at a low level, the optocoupler U10 provides current through the resistor R3, the optocoupler's phototransistor is turned on, and the G pole of the PMOS tube Q1 is pulled down to a low level. The PMOS tube is turned on, and the charging current flows through the PMOS tube.

[0031] When the Vin voltage is less than 15V, the cathode of U2 (TL431) is at a high level, forcing the optocoupler to cut off. The G pole of the PMOS tube Q1 increases the bias voltage through the internal diode-R2-R1 resistor, forcing the PMOS tube Q1 to turn off, thereby achieving unidirectional current within a specific range.

[0032] The present invention can be applied to various electrical equipment to prevent the battery voltage from flowing back to the input terminal.

[0033] The above describes the specific embodiments of the present invention. It should be understood that the present invention is not limited to the above specific embodiments, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the essence of the present invention. In the absence of conflict, the embodiments of the present application and the features in the embodiments can be combined with each other arbitrarily.

Claims

1. A backflow prevention circuit, characterized in that: include: Power circuit, sampling circuit and control circuit; The sampling circuit is connected to an input voltage Vin and connected to the control circuit through the power circuit, thereby controlling the PMOS tube Q1 in the control circuit; The power circuit includes: a resistor R3, a comparator U2 and an optical coupler U10; One end of the resistor R3 is connected to the input voltage Vin, and the other end is connected to the anode of the light emitting diode in the optocoupler U10, the anode of the comparator U2 is connected between the resistor R13 and the ground, the cathode of the comparator U2 is connected to the cathode of the light emitting diode in the optocoupler U10, and the reference electrode of the comparator U2 is connected between the resistor R10 and the resistor R13; The emitter of the phototransistor in the optical coupler U10 is grounded, and the collector of the phototransistor in the optical coupler U10 is connected to the control circuit; The control circuit includes: a resistor R1, a resistor R2, a resistor R6 and the PMOS tube Q1; One end of the resistor R6 is connected to the optical coupler U10, and one end of the resistor R1 and the resistor R2 are connected in parallel to the other end of the resistor R6; The other end of the resistor R2 is connected to the battery voltage Vcharge; The other end of the resistor R1 is connected to the gate of the PMOS transistor Q1 , the source of the PMOS transistor Q1 is connected to the battery voltage Vcharge, and the drain of the PMOS transistor Q1 is connected to the input voltage Vin.

2. The anti-backflow circuit according to claim 1, characterized in that: The sampling circuit includes a resistor R10 and a resistor R13 connected in series. One end of the resistor R10 is connected to an input voltage Vin, and the other end is grounded through the resistor R13.

3. An electrical device, characterized in that: The invention comprises the anti-backflow circuit as claimed in any one of claims 1 or 2.

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