A reverse connection and overvoltage protection circuit

Abstract

The utility model provides a kind of anti-reverse connection and overvoltage protection circuit, belong to switch protection technical field, including: switch unit, including two power field effect tubes, back-to-back connection between input port and output port;The input end of input voltage detection unit is connected input port;The control end of switch control unit is connected input port and the output end of input voltage detection unit respectively, and the output end of switch control unit is connected the control end of switch unit;Anti-reverse connection unit, including the first voltage stabilizing module between the output end of switch control unit and the source electrode of power field effect tube, and the second voltage stabilizing module between the control end of switch control unit and ground end. Advantageous effect: two power field effect tubes back-to-back connection is formed to the form of pair of tubes, realize the anti-reverse connection function of input voltage;While input voltage detection and switch control function do not need to rely on single-chip microcomputer control, improve circuit control real-time, eliminate software failure risk.

Description

Technical Field

[0001] This utility model relates to the field of switch protection technology, and in particular to a reverse connection and overvoltage protection circuit. Background Technology

[0002] Power MOSFETs (P-MOSFETs) are voltage-controlled devices with advantages such as extremely high gate static resistance, low drive power, high operating frequency, and good thermal stability. They are commonly used in small and medium power switching circuits.

[0003] like Figure 1 The diagram shows a switching circuit for a single P-MOSFET device. It mainly uses a microcontroller unit (MCU) to control the switching transistor Q1 to turn on and off, thereby achieving the purpose of turning on and off the input voltage Vin.

[0004] The main principle of this switching circuit is as follows: The MCU continuously monitors the input voltage (Vin) divider signal Vin_DET through its analog-to-digital (AD) converter port. When the input voltage divider signal Vin_DET is detected to be within the normal range, the MCU sends a high-level control signal Vo_EN to turn on the switch Q2, making the control terminal of the switch Q1 low, thereby turning on the switch Q1. When the input voltage divider signal Vin_DET exceeds the set upper limit, the MCU sends a low-level control signal Vo_EN to turn off the switch Q2, making the control terminal of the switch Q1 high, thereby turning off the switch Q1.

[0005] The following problems exist in this switching circuit: (1) The input voltage is detected by the MCU and the switching transistor Q1 is controlled by the MCU to turn on and off. If the software fails, the control function will also be at risk of failure; (2) The control action time will be affected by the time cycle of the software in the microcontroller, resulting in a certain control delay, which greatly reduces the real-time performance of the circuit control; (3) Since the microcontroller control circuit is used, it will occupy the resources of the two control ports of the microcontroller, resulting in a waste of resources; (4) There is only one switching transistor in the circuit to turn on and off the input voltage. When the polarity of the input voltage is reversed, GND is the positive terminal of the input voltage and Vin is the negative terminal of the input voltage. Therefore, the current will be output from GND and return directly to the negative terminal Vin of the input voltage through the body diode of the switching transistor Q1. Therefore, the reverse protection function of the input voltage cannot be realized. Utility Model Content

[0006] To solve the above technical problems, this utility model provides a reverse connection protection and overvoltage protection circuit.

[0007] The technical problem solved by this utility model can be achieved by the following technical solution:

[0008] A reverse connection and overvoltage protection circuit, comprising:

[0009] A switching unit, the switching unit including two power MOSFETs, the two power MOSFETs being connected back-to-back between an input port and an output port;

[0010] An input voltage detection unit, wherein the input terminal of the input voltage detection unit is connected to the input port;

[0011] A switch control unit, wherein the control terminal of the switch control unit is connected to the input port and the output terminal of the input voltage detection unit respectively, and the output terminal of the switch control unit is connected to the control terminal of the switch unit;

[0012] The reverse connection protection unit includes a first voltage regulator module connected between the output terminal of the switch control unit and the source of the power MOSFET, and a second voltage regulator module connected between the control terminal and the ground terminal of the switch control unit.

[0013] Preferably, the two power MOSFETs include:

[0014] A first power MOSFET, the drain of which is connected to the input port, the source of which is connected to the output terminal of the switch control unit through a first pull-up resistor, and the gate of which is connected to the output terminal of the switch control unit through a second pull-up resistor;

[0015] The second power MOSFET has its source connected to the source of the first power MOSFET, its gate connected to the output terminal of the switch control unit via a third pull-up resistor, and its drain connected to the output port.

[0016] Preferably, it further includes:

[0017] An input filtering unit is connected between the input port and the ground terminal;

[0018] An output filtering unit is connected between the output port and the ground terminal.

[0019] Preferably, the input filtering unit includes:

[0020] The first capacitor and the second capacitor are connected in parallel between the input port and the ground terminal;

[0021] The output filtering unit includes:

[0022] The third and fourth capacitors are connected in parallel between the output port and the ground terminal;

[0023] Preferably, the input voltage detection unit includes:

[0024] The third power MOSFET has its gate connected to the voltage sampling signal sampled from the input port, its source connected to the ground terminal, and its drain connected to the control terminal of the switch control unit.

[0025] Preferably, the voltage sampling signal is generated by a resistor voltage divider circuit, which includes a predetermined number of voltage divider resistors connected in series between the input port and the ground terminal. The points where the voltage divider resistors are connected form voltage divider nodes, and the voltage sampling signal is led out from the voltage divider nodes.

[0026] Preferably, the switch control unit includes:

[0027] The fourth power MOSFET has its gate connected to the output terminal of the input voltage detection unit, its source connected to the ground terminal, and its drain connected to the control terminal of the switching unit.

[0028] The fourth pull-up resistor is connected between the gate of the fourth power MOSFET and the input port.

[0029] Preferably, it further includes:

[0030] The fifth capacitor and the seventh resistor are connected in parallel between the gate of the fourth power MOSFET and the ground terminal.

[0031] Preferably, the first voltage regulator module includes:

[0032] A first Zener diode, the anode of which is connected to the output terminal of the switch control unit, and the cathode of which is connected to the source of the power MOSFET.

[0033] Preferably, the second voltage regulator module includes:

[0034] The second Zener diode has its anode connected to the ground terminal and its cathode connected to the control terminal of the switch control unit.

[0035] The advantages or beneficial effects of this utility model's technical solution are as follows:

[0036] This invention achieves reverse connection protection for the input voltage by using two power MOSFETs connected back-to-back to form a transistor pair. At the same time, the input voltage detection and switching control functions do not rely on microcontroller control, which improves the real-time performance of circuit control, eliminates the risk caused by software failure, and frees up the port resources occupied by the MCU. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the switching circuit of a conventional single P-MOSFET device in the prior art;

[0038] Figure 2 This is a block diagram illustrating the principle of the anti-reverse and overvoltage protection circuit in a preferred embodiment of the present invention.

[0039] Figure 3 This is a schematic diagram of the anti-reverse and overvoltage protection circuit in a preferred embodiment of the present invention. Detailed Implementation

[0040] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0041] It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0042] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but this is not intended to limit the present invention.

[0043] See Figure 2 and Figure 3 In a preferred embodiment of this utility model, based on the above-mentioned problems existing in the prior art, a reverse connection protection and overvoltage protection circuit is provided, comprising:

[0044] Switching unit 1 includes two power MOSFETs, namely a first power MOSFET Q3 and a second power MOSFET Q4, which are connected back-to-back between the input port and the output port.

[0045] Input voltage detection unit 2, the input terminal of input voltage detection unit 2 is connected to the input port;

[0046] Switch control unit 3, the control terminal of switch control unit 3 is connected to the input port and the output terminal of input voltage detection unit 2 respectively, and the output terminal of switch control unit 3 is connected to the control terminal of switch unit 1;

[0047] The reverse connection protection unit 4 includes a first voltage regulator module 41 connected between the output terminal of the switch control unit 3 and the source of the power MOSFET, and a second voltage regulator module 42 connected between the control terminal and the ground terminal of the switch control unit 3.

[0048] Specifically, in view of the problem that a single switching transistor in the prior art cannot achieve the reverse input voltage protection function, this utility model embodiment proposes that the switching transistor be connected in the form of two PMOS transistors in a pair configuration to achieve the reverse input voltage protection function.

[0049] In addressing the problems of existing technologies that use MCUs to control the switching transistor Q1 to turn on and off, such as the risk of control function failure due to software malfunction, reduced real-time performance due to control delay, and resource waste due to port occupation, this utility model embodiment implements input voltage detection and switch control functions entirely by hardware circuits, without relying on a microcontroller and corresponding software control. This improves the real-time performance of circuit control, eliminates the risks caused by software malfunction, and frees up MCU port resources.

[0050] In a preferred embodiment, the two power MOSFETs include:

[0051] The first power MOSFET Q3 has its drain connected to the input port, its source connected to the output terminal of the switch control unit 3 via the first pull-up resistor R6, and its gate connected to the output terminal of the switch control unit 3 via the second pull-up resistor R7.

[0052] The source of the second power MOSFET Q4 is connected to the source of the first power MOSFET Q3. The gate of the second power MOSFET Q4 is connected to the output terminal of the switch control unit 3 through the third pull-up resistor R8. The drain of the second power MOSFET Q4 is connected to the output port.

[0053] Specifically, in this embodiment, when the gates (i.e., control terminals) of the first power MOSFET Q3 and the second power MOSFET Q4 are at a low level, the first power MOSFET Q3 and the second power MOSFET Q4 are turned on.

[0054] When the gates (i.e. control terminals) of the first power MOSFET Q3 and the second power MOSFET Q4 are at a high level, the first power MOSFET Q3 and the second power MOSFET Q4 are turned off.

[0055] The input voltage Vin is controlled by forming a pair of power MOSFETs Q3 and Q4.

[0056] In this embodiment, the first power MOSFET Q3 and the second power MOSFET Q4 are selected as P-channel MOSFETs.

[0057] In a preferred embodiment, it further includes:

[0058] The input filter unit is connected between the input port and the ground terminal;

[0059] The output filter unit is connected between the output port and the ground terminal.

[0060] Specifically, in this embodiment, an input filtering unit is provided at the input end of the circuit to filter out high-frequency noise in the input signal.

[0061] By setting an output filter unit at the circuit output terminal, noise interference in the signal is reduced, ensuring the quality and stability of the output signal and improving the stability of the circuit.

[0062] In a preferred embodiment, the input filtering unit includes:

[0063] The first capacitor C2 and the second capacitor C3 are connected in parallel between the input port and the ground terminal.

[0064] Specifically, in this embodiment, the input filtering unit is composed of a first capacitor C2 and a second capacitor C3 connected in parallel to form an input filtering network, which is used to absorb and disperse high-frequency noise from the input terminal and protect the subsequent circuits from interference.

[0065] In a preferred embodiment, the output filtering unit includes:

[0066] The third capacitor C4 and the fourth capacitor C5 are connected in parallel between the output port and the ground terminal.

[0067] Specifically, in this embodiment, the output filtering unit consists of a third capacitor C4 and a fourth capacitor C5 connected in parallel to form an output filtering network, which is used to filter out high-frequency noise and harmonics in the output signal and ensure the stability of the output signal.

[0068] In a preferred embodiment, the input voltage detection unit 2 includes:

[0069] The third power MOSFET Q5 has its gate connected to the voltage sampling signal sampled from the input port, its source connected to the ground terminal, and its drain connected to the control terminal of the switch control unit 3.

[0070] Specifically, when the gate (i.e., the control terminal) of the third power MOSFET Q5 is at a low level, the third power MOSFET Q5 is turned off;

[0071] When the gate (i.e., control terminal) of the third power MOSFET Q5 is high, the third power MOSFET Q5 is turned on.

[0072] In this embodiment, the third power MOSFET Q5 is an N-channel MOSFET.

[0073] In a preferred embodiment, the voltage sampling signal is generated by a resistor voltage divider circuit, which includes a predetermined number of voltage divider resistors connected in series between the input port and the ground terminal. The points where the voltage divider resistors are connected form voltage divider nodes, and the voltage sampling signal is led out from the voltage divider nodes.

[0074] Specifically, in this embodiment, the voltage divider circuit uses two voltage divider resistors, but it is not limited to this. The number of voltage divider resistors can be set according to actual needs, and this utility model does not limit this.

[0075] Specifically, the two voltage divider resistors include: the fifth resistor R9 and the sixth resistor R10, which are connected in series between the input port and the ground terminal.

[0076] In a preferred embodiment, the switch control unit 3 includes:

[0077] The fourth power MOSFET Q6 has its gate connected to the output terminal of the input voltage detection unit 2, its source connected to the ground terminal, and its drain connected to the control terminal of the switching unit 1.

[0078] The fourth pull-up resistor R11 is connected between the gate and the input port of the fourth power MOSFET Q6.

[0079] Specifically, when the gate (i.e., the control terminal) of the fourth power MOSFET Q6 is low, the fourth power MOSFET Q6 is turned off;

[0080] When the gate (i.e., the control terminal) of the fourth power MOSFET Q6 is at a high level, the fourth power MOSFET Q6 is turned on.

[0081] In this embodiment, the fourth power MOSFET Q6 is an N-channel MOSFET.

[0082] In a preferred embodiment, it further includes:

[0083] The fifth capacitor C6 and the seventh resistor R12 are connected in parallel between the gate of the fourth power MOSFET Q6 and the ground terminal.

[0084] In a preferred embodiment, the first voltage regulator module 41 includes:

[0085] The first Zener diode ZD2 has its anode connected to the output terminal of the switch control unit 3, and its cathode connected to the source of the power MOSFET.

[0086] Specifically, due to the forward conduction of the first Zener diode ZD2, the gate-source voltage of the switching unit 1, which includes two power MOSFETs, namely the first power MOSFET Q3 and the second power MOSFET Q4, is clamped at 0.6V, protecting the power MOSFETs from damage caused by excessively high gate voltage, thereby protecting the power MOSFET devices.

[0087] In a preferred embodiment, the second voltage regulator module 42 includes:

[0088] The second Zener diode ZD3 has its anode connected to the ground terminal and its cathode connected to the control terminal of the switch control unit 3.

[0089] Specifically, due to the forward conduction of the second Zener diode ZD3, the gate-source voltage of the fourth power MOSFET Q6 is clamped at 0.6V, protecting the power MOSFET from damage caused by excessive gate voltage, thereby protecting the power MOSFET device.

[0090] The anti-reverse and overvoltage protection circuit of this utility model embodiment is as follows: Figure 3 As shown, its working principle is as follows:

[0091] When the input voltage Vin is within the set voltage range, the input voltage Vin is divided by the fifth resistor R9 and the sixth resistor R10. The voltage after voltage division is insufficient to drive the third power MOSFET Q5 to conduct. At this time, the control terminal of the fourth power MOSFET Q6 is kept at a high level due to the effect of the fourth pull-up resistor R11, causing the fourth power MOSFET Q6 to conduct. The drain of the fourth power MOSFET Q6 becomes low level, which at the same time pulls the control terminals of the first power MOSFET Q3 and the second power MOSFET Q4 to a low level, causing the first power MOSFET Q3 and the second power MOSFET Q4 to conduct.

[0092] When the input voltage Vin exceeds the set voltage range, the input voltage Vin is divided by resistors R9 and R10. The divided voltage is sufficient to drive the third power MOSFET Q5 to conduct. After Q5 conducts, it pulls the gate of the fourth power MOSFET Q6 low, causing Q6 to turn off. At this time, the gates of the first power MOSFET Q3 and the second power MOSFET Q4 are pulled high by the first pull-up resistor R6 and the third pull-up resistor R8, respectively, turning off Q3 and Q4. Thus, the overvoltage protection function of the circuit can be realized in real time through the hardware circuit.

[0093] Due to the forward conduction of the second Zener diode ZD3, the gate-source voltage of the fourth power MOSFET Q6 is clamped at 0.6V, which protects the gate and source of the fourth power MOSFET Q6 and prevents the control terminal from being damaged by excessive forward voltage.

[0094] Similarly, due to the forward conduction of the first Zener diode ZD2, the gate-source voltages of the first power MOSFET Q3 and the second power MOSFET Q4 are also clamped at 0.6V, which also protects the gate and source of the first power MOSFET Q3 and the second power MOSFET Q4.

[0095] When the input voltage polarity is reversed, i.e., the GND terminal becomes the positive terminal and the Vin terminal becomes the negative terminal, due to the direct conduction of the Zener diode, the gate-source voltage of the fourth power MOSFET Q6 becomes zero under reverse voltage, thus putting the fourth power MOSFET Q6 in the off state. At the same time, due to the presence of the first Zener diode ZD2, the first power MOSFET Q3 and the second power MOSFET Q4 are also in the off state. Since the first power MOSFET Q3 and the second power MOSFET Q4 are connected back-to-back to form a pair, and the PN junctions of their body diodes are in opposite directions, the input current cannot flow when both are off, thus achieving the reverse connection protection function of the input voltage.

[0096] The advantages or beneficial effects of adopting the above technical solution are as follows: This utility model achieves the reverse connection protection function of the input voltage by using two power MOSFETs connected back to back to form a pair of transistors; at the same time, the input voltage detection and switching control functions do not need to rely on the microcontroller control, which improves the real-time performance of the circuit control, eliminates the risk caused by software failure, and releases the port resource occupation of the MCU.

[0097] The above are merely preferred embodiments of the present utility model and are not intended to limit the implementation methods and protection scope of the present utility model. Those skilled in the art should realize that any equivalent substitutions and obvious changes made using the content of this specification and illustrations should be included within the protection scope of the present utility model.

Claims

1. A reverse connection and overvoltage protection circuit, characterized in that, include: A switching unit, the switching unit including two power MOSFETs, the two power MOSFETs being connected back-to-back between an input port and an output port; An input voltage detection unit, wherein the input terminal of the input voltage detection unit is connected to the input port; A switch control unit, wherein the control terminal of the switch control unit is connected to the input port and the output terminal of the input voltage detection unit, and the output terminal of the switch control unit is connected to the control terminal of the switch unit; The reverse connection protection unit includes a first voltage regulator module connected between the output terminal of the switch control unit and the source of the power MOSFET, and a second voltage regulator module connected between the control terminal and the ground terminal of the switch control unit.

2. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that, The two power MOSFETs include: A first power MOSFET, the drain of which is connected to the input port, the source of which is connected to the output terminal of the switch control unit through a first pull-up resistor, and the gate of which is connected to the output terminal of the switch control unit through a second pull-up resistor; The second power MOSFET has its source connected to the source of the first power MOSFET, its gate connected to the output terminal of the switch control unit via a third pull-up resistor, and its drain connected to the output port.

3. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that, Also includes: An input filtering unit is connected between the input port and the ground terminal; An output filtering unit is connected between the output port and the ground terminal.

4. The reverse connection and overvoltage protection circuit according to claim 3, characterized in that, The input filtering unit includes: The first capacitor and the second capacitor are connected in parallel between the input port and the ground terminal; The output filtering unit includes: The third and fourth capacitors are connected in parallel between the output port and the ground terminal.

5. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that, The input voltage detection unit includes: The third power MOSFET has its gate connected to the voltage sampling signal sampled from the input port, its source connected to the ground terminal, and its drain connected to the control terminal of the switch control unit.

6. The reverse connection and overvoltage protection circuit according to claim 5, characterized in that, The voltage sampling signal is generated by a resistor voltage divider circuit, which includes a predetermined number of voltage divider resistors connected in series between the input port and the ground terminal. The points where the voltage divider resistors are connected form voltage divider nodes, and the voltage sampling signal is led out from the voltage divider nodes.

7. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that, The switch control unit includes: The fourth power MOSFET has its gate connected to the output terminal of the input voltage detection unit, its source connected to the ground terminal, and its drain connected to the control terminal of the switching unit. The fourth pull-up resistor is connected between the gate of the fourth power MOSFET and the input port.

8. The reverse connection and overvoltage protection circuit according to claim 7, characterized in that, Also includes: The fifth capacitor and the seventh resistor are connected in parallel between the gate of the fourth power MOSFET and the ground terminal.

9. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that, The first voltage regulator module includes: A first Zener diode, the anode of which is connected to the output terminal of the switch control unit, and the cathode of which is connected to the source of the power MOSFET.

10. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that, The second voltage regulator module includes: The second Zener diode has its anode connected to the ground terminal and its cathode connected to the control terminal of the switch control unit.

Images