Anti-reverse-connection and anti-overvoltage protection circuit

Abstract

The utility model provides an anti-reverse connection and anti-overvoltage protection circuit, which comprises an anti-reverse connection circuit, an anti-overcurrent current-limiting circuit, an anti-overvoltage circuit and a working state indicating circuit which are connected in sequence, the anti-overcurrent current-limiting circuit comprises triodes Q5 and Q6 and resistors R12 and R13, the base electrode of the triode Q6 is connected with the emitter electrode of the triode Q5, and the base electrode of the triode Q6 is connected with the emitter electrode of the triode Q6. The collector electrode of the triode Q6 is connected with the base electrode of the triode Q5, the collector electrode of the triode Q6 and the base electrode of the triode Q5 are grounded through the resistor R13, one end of the resistor R12 is connected with the emitter electrode of the triode Q5, the other end of the resistor R12 is connected with the emitter electrode of the triode Q6 and then connected with a power supply VCC end, and the collector electrode of the triode Q5 is connected to a subsequent anti-overvoltage circuit. The over-current protection circuit has the advantages that the over-current protection function and the current-limiting protection function are designed in the circuit, and the completeness and the reliability of the circuit for protecting the post-stage load function are improved.

Description

Technical Field

[0001] The utility model mainly relates to the technical field of power supply circuit protection, and in particular to an anti-reverse connection and anti-overvoltage protection circuit. Background Art

[0002] When supplying power to a DC power supply device through a DC power supply, if the positive and negative poles of the power supply are connected in reverse, the device may not work at best, or may burn and damage the device at worst, so a reverse connection protection circuit is needed. In the existing technical solution, a forward diode is connected in series at the positive power input end, and the forward conduction and reverse cutoff characteristics of the diode are utilized. Under normal circumstances, the diode is turned on and the circuit board works. When the power supply is reversed, the diode is cut off, the power supply cannot form a loop, and no reverse current flows through the circuit board, thereby effectively protecting the problem of reverse power supply connection. However, this technical solution has the following defects: 1. Energy needs to be consumed on the diode, resulting in energy loss; 2. The tube voltage drop limits the discharge degree of the battery.

[0003] In view of this, the patent with application number CN202120722526.6 discloses a reverse connection and overvoltage protection circuit. Based on PNP transistors, PMOS tubes, and NMOS tubes, a protection circuit is designed to prevent reverse connection and overvoltage of the DC power supply. Since the MOS tube works in a switching state, it will not consume too much energy in the protection circuit, thus achieving dual protection against reverse connection and overvoltage. At the same time, a fuse and RC spike absorption circuit are designed at the input end of the circuit to further improve the circuit reliability.

[0004] The patent application number CN202121364879.X discloses an anti-reverse overvoltage protection circuit, which includes a first MOSFET tube Q1 and resistors R1 and R2. GS If the current is greater than the turn-on voltage, the circuit is turned on. If the positive and negative poles of the power supply are connected to the MOSFET tube V GS When the overvoltage is less than the turn-on voltage, the MOSFET tube is cut off and no output occurs. When there is overvoltage in the overvoltage protection circuit, the voltage stabilizing diode ZD1 is turned on by overvoltage, the NPN transistor Q2 starts to work, and the subsequent MOSFET tube Q3 V GS If the voltage is lower than the opening voltage, Q3 is turned off and the load is disconnected. In addition, a secondary voltage regulator ZD2 is set. If the first-stage voltage regulator, Q2 and transistor fail, the next-stage ZD2 voltage regulator diode can also play an overvoltage protection role to achieve overvoltage protection.

[0005] The patent with application number CN202011334343.3 proposes an overvoltage suppression protection and anti-reverse connection circuit. The anti-reverse connection circuit includes a resistor R3, a voltage zener diode V3, and a MOS tube Q4. When the polarity of the power supply is reversed, the V3 voltage zener tube is forward-conducted, the voltage between the MOS tube GS is small, the drain and source of the MOS tube are not conducting, and the circuit cannot work normally, thereby playing a role in preventing reverse connection. The overvoltage protection circuit includes voltage zener tubes V1 and V2, transistors Q1 and Q3, MOS tube Q2, and capacitor C5. When the voltage is too large, the voltage zener tube V2 breaks down, the transistors Q1 and Q3 are turned on, there is no voltage difference between the two ends of the voltage zener tube V1, the MOS tube Q2 is not conducting, and the power supply has no output, thereby protecting the subsequent circuit.

[0006] The above technical solutions all use MOS tubes to form anti-reverse connection and overvoltage protection circuits. However, during the MOS opening process, there is a large voltage transient, namely dv / dt, which generates a large displacement current Cdv / dt in the parasitic capacitor, forming a current spike; during the MOS closing process, a current transient, di / dt, is generated in the channel, and the transient current generates a spike voltage Ldi / dt at the parasitic inductance end. This spike voltage can easily break down the MOS tube, causing damage to the MOS tube, thereby causing damage to the entire anti-reverse connection and overvoltage protection circuit. In addition, the existing anti-reverse connection and overvoltage protection circuit has no status indication when a fault occurs. Utility Model Content

[0007] The technical problem to be solved by the utility model is how to prevent the reduction of the safety of the anti-reverse connection and anti-overvoltage circuits caused by peak voltage, circuit overcurrent and circuit failure.

[0008] The utility model solves the above technical problems through the following technical means: a reverse connection and overvoltage protection circuit, comprising a reverse connection protection circuit, an overcurrent protection and current limiting circuit, an overvoltage protection circuit and a working status indication circuit connected in sequence, wherein the overcurrent protection and current limiting circuit comprises transistors Q5, Q6, resistors R12 and R13, the base of the transistor Q6 is connected to the emitter of the transistor Q5, the collector of the transistor Q6 is connected to the base of the transistor Q5, the collector of the transistor Q6 and the base of the transistor Q5 are grounded through the resistor R13, one end of the resistor R12 is connected to the emitter of the transistor Q5, and the other end is connected to the emitter of the transistor Q6 and then connected to the power supply VCC end, and the collector of the transistor Q5 is connected to the subsequent overvoltage protection circuit.

[0009] As a preferred technical solution, the collector of the transistor Q6 and the base of the transistor Q5 are grounded through a resistor R13 and a resistor R9 and a capacitor C3 connected in series.

[0010] As a preferred technical solution, the resistor R12 is an adjustable resistor.

[0011] As a preferred technical solution, the anti-reverse connection circuit includes a MOSFET tube Q4, a resistor R1, a resistor R3, a capacitor C1 and a voltage-stabilizing diode D1, the resistors R1 and R3 are connected in series between VCC and the source of the MOSFET tube Q4, the drain of the MOSFET tube Q4 is connected to the node between the resistor R1 and the resistor R3, the other end of the resistor R1 serves as the positive end of the power input, the voltage-stabilizing diode D1 and the capacitor C1 are connected in parallel between the gate and the source of the MOSFET tube Q4, wherein the negative end of the voltage-stabilizing diode D1 is connected to the gate of the MOSFET tube Q4, and one end of the drain of the MOSFET tube Q4 is the negative end of the power input and is grounded.

[0012] As a preferred technical solution, the anti-reverse connection circuit also includes a resistor R9 and a capacitor C3. The capacitor C3 and the resistor R9 are connected in series and connected between the drain and source of the MOSFET tube Q4 to form an RC spike protection circuit.

[0013] As a preferred technical solution, the overvoltage protection circuit includes a MOSFET tube Q1, a triode Q2, Q3, resistors R2, R4, R5, R6, R7, R8, R10 and a voltage stabilizing diode D3. The emitter of the triode Q2 is connected to the collector of the triode Q5 and VCC1 at the same time. VCC1 is connected to the source of the MOSFET tube Q4 through a series resistor R6 and a voltage stabilizing diode D3. The base of the triode Q2 is connected to the node between the cathode of the voltage stabilizing diode D3 and the resistor R6 through a resistor R8. The collector of the triode Q2 is connected to the collector of the MOSFET tube Q4 through a series resistor R5 and R7. 4 source, the node between resistors R5 and R7 is connected to the base of transistor Q3, VCC1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to the source of MOSFET tube Q4 through resistor R4, the node between resistor R2 and resistor R4 is connected to the collector of transistor Q3, the collector of transistor Q3 is connected to the gate of MOSFET tube Q1, the emitter of transistor Q3 is connected to the source of MOSFET tube Q1 and is connected to the source of MOSFET tube Q4, the first end of resistor R2 is used as the positive end of power output, and the drain of MOSFET tube Q1 is used as the negative end of power output.

[0014] As a further preferred technical solution, a resistor R11 and a capacitor C4 are connected in series between the source and the drain of the MOSFET tube Q1 to form an RC spike protection circuit.

[0015] As a further preferred technical solution, a voltage zener diode D2 and a capacitor C2 are connected in parallel between the gate and source of the MOSFET tube Q1, and the cathode of the voltage zener diode D2 is connected to the gate of the MOSFET tube Q1.

[0016] As a further preferred technical solution, the voltage stabilization value of the voltage stabilizing diode D3 is adjustable.

[0017] As a preferred technical solution, the working status indication circuit includes a light emitting diode D4 and a resistor R10, and VCC1 is sequentially connected to the light emitting diode D4, the resistor R10, the drain of the MOSFET tube Q1 and the negative terminal of the power output.

[0018] In the above technical solution, the transistors Q5 and Q6 are PNP transistors, and the MOSFET tubes are all N-channel MOSFET tubes.

[0019] The advantages of the utility model are:

[0020] 1. The circuit is designed with overcurrent protection and current limiting functions. By changing the value of the resistor, it can also limit the current, thus improving the integrity and reliability of the circuit in protecting the subsequent load function.

[0021] 2. In the overvoltage protection circuit, adjusting the voltage stabilization value of the voltage stabilizing diode D3 can adjust the overvoltage range of the circuit, so that the circuit can meet the needs of different power supply ranges;

[0022] 3. This solution is based on PNP transistors, NPN transistors, voltage regulator diodes, and N-channel MOSFET tubes to design anti-reverse connection circuits, anti-overvoltage circuits, and anti-overcurrent and current limiting circuits. Since the MOSFET tube works in a switching state, the energy provided to the load by the circuit output will not be consumed too much in the protection circuit, which improves the utilization rate of electric energy and realizes triple protection of reverse connection, overvoltage, and overcurrent;

[0023] 4. An RC spike protection circuit is added between the source and drain of the MOSFET tube to improve the safety of the circuit;

[0024] 5. The circuit also adds a working status indication circuit. When the system does not have overvoltage and reverse connection, the indicator light is on; when the system has overvoltage and reverse connection, the indicator light is off, thereby reminding the operator. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is an overall circuit diagram of the reverse connection protection overvoltage protection circuit of the embodiment of the utility model. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the embodiments of the utility model clearer, the technical solution in the embodiments of the utility model will be clearly and completely described below in combination with the embodiments of the utility model. Obviously, the described embodiments are part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0027] This scheme proposes an anti-reverse connection and anti-overvoltage protection circuit, including an anti-reverse connection circuit, an anti-overvoltage circuit, an anti-overcurrent current limiting circuit and a working status indication circuit. N-channel MOSFET tubes are selected in both the anti-reverse connection circuit and the anti-overvoltage circuit, because N-channel MOSFET tubes have small on-resistance, large market demand, low price, and the product has its own protection circuit and stable operation.

[0028] Anti-reverse connection circuit Figure 1 As shown, it includes a MOSFET tube Q4, a resistor R1, a resistor R3, a resistor R9, a capacitor C1, a capacitor C3, and a voltage regulator diode D1.

[0029] Resistors R1 and R3 are connected in series between VCC and the source of MOSFET tube Q4, and the drain of MOSFET tube Q4 is connected to the node between resistors R1 and R3, so that resistors R1 and R3 form a voltage divider circuit, and the other end of resistor R1 is used as the positive end of power input, and voltage zener diode D1 and capacitor C1 are connected in parallel between the gate and source of MOSFET tube Q4, wherein the negative end of voltage zener diode D1 is connected to the gate of MOSFET tube Q4, and voltage zener diode D1, capacitor C1 and resistor R3 form a parallel relationship. Capacitor C3 and resistor R9 are connected in series between the drain and source of MOSFET tube Q4 to form an RC spike protection circuit, and one end of the drain of MOSFET tube Q4 is the negative end of power input and is grounded.

[0030] Working principle of the anti-reverse connection circuit: When the power supply is connected normally, the power supply VCC flows back to GND through resistors R1, R3 and the internal parasitic diode of MOSFET tube Q4 to form a loop. At this time, a voltage difference (U) is generated between the source and gate of MOS tube Q4 using the principle of series voltage division. GS >0), MOSFET tube Q4 is turned on, and the source and drain of MOSFET tube Q4 are connected to GND after being turned on, and the circuit works normally. Among them, the voltage zener diode D1 and the capacitor C1 are used to protect the MOSFET tube Q4. By using the reverse breakdown characteristics of the voltage zener diode D1, when the voltage is higher than the normal working voltage of the MOSFET tube Q4, the voltage zener diode D1 reversely breaks down so that the gate voltage of the MOSFET tube Q4 is always in the normal working range, preventing the MOSFET tube Q4 from being damaged by excessive voltage. The capacitor C1 plays a role in filtering and anti-interference, making the MOSFET tube Q4 work more stably. When the power supply is reversed, the source and gate of the MOSFET tube Q4 cannot generate a voltage difference, the MOSFET tube Q4 cannot be turned on, the current loop cannot be generated, and the power supply has no output, thereby realizing the anti-reverse connection function.

[0031] Overcurrent protection circuit such as Figure 1As shown: it includes transistors Q5, Q6, resistors R12, R13, transistors Q5 and Q6 are PNP tubes, the base of transistor Q6 is connected to the emitter of transistor Q5, the collector of transistor Q6 is connected to the base of transistor Q5, the collector of transistor Q6 and the base of transistor Q5 are connected to the source of MOSFET tube Q4 through resistor R13, one end of resistor R12 is connected to the emitter of transistor Q5, and the other end is connected to the emitter of transistor Q6 and then connected to the power supply VCC terminal.

[0032] Working principle of overcurrent protection and current limiting circuit: When the subsequent load has overcurrent, the voltage difference generated by resistor R12 turns on transistor Q6. At this time, VCC is short-circuited to GND through the emitter, collector and resistor R13 of transistor Q6, so that the subsequent stage has no output; when the subsequent load has no overcurrent, transistor Q6 is not turned on, and VCC supplies power to the subsequent stage through the conduction of transistor Q5; by changing the resistance value of resistor R12, it can also play a role in current limiting.

[0033] Overvoltage protection circuit Figure 1 As shown: it includes MOSFET tube Q1, transistor Q2, transistor Q3, resistor R2, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R10, resistor R11, capacitor C2, capacitor C4 and voltage regulator diode D3.

[0034] Transistor Q2 is a PNP tube, and transistor Q3 is an NPN tube. The emitter of transistor Q2 is connected to the collector of transistor Q5 and VCC1 at the same time. VCC1 is connected to the source of MOSFET tube Q4 through resistor R6 and voltage regulator diode D3 in series. The base of transistor Q2 is connected to the node between the cathode of voltage regulator diode D3 and resistor R6 through resistor R8. The collector of transistor Q2 is connected to the source of MOSFET tube Q4 through resistor R5 and R7 in series. The node between resistor R5 and R7 is connected to the base of transistor Q3. VCC1 is connected to the first end of resistor R2. The second end of resistor R2 is connected to the source of MOSFET tube Q4 through resistor R4. The node between resistor R2 and resistor R4 The collector of the transistor Q3 is connected, the collector of the transistor Q3 is connected to the gate of the MOSFET tube Q1, the emitter of the transistor Q3 is connected to the source of the MOSFET tube Q1 and is connected to the source of the MOSFET tube Q4, the Zener diode D2 and the capacitor C2 are connected in parallel between the gate and the source of the MOSFET tube Q1, the cathode of the Zener diode D2 is connected to the gate of the MOSFET tube Q1, and the resistor R11 and the capacitor C4 are connected in series between the source and the drain of the MOSFET tube Q1 to form an RC spike protection circuit, the first end of the resistor R2 serves as the positive end of the power output, and the drain of the MOSFET tube Q1 serves as the negative end of the power output.

[0035] Working principle of overvoltage protection circuit: When the power supply is overvoltage, the voltage zener diode D3 is broken down, and VCC1 is divided into two paths through R6. One path flows to GND through the voltage zener diode D3, and the other path flows to the base of the transistor Q2 through R8. Since the voltage zener diode D3 is broken down, the voltage is maintained at its regulated value. At this time, a voltage difference (U BE <0, transistor Q2 is turned on, and the power supply VCC1 flows into transistor Q3 through transistor Q2 and resistor R5, generating a voltage difference between the base and emitter of transistor Q3 (U BE >0), transistor Q3 is turned on, pulling down the voltage at the gate of MOSFET tube Q1. No voltage difference can be formed between the gate and source of MOSFET tube Q1, the circuit cannot be turned on, and the power supply has no output, thus realizing the overvoltage protection function. Zener diode D2 and capacitor C2 are used to protect the gate of MOSFET tube Q1. When the voltage is too high, the reverse breakdown characteristic of Zener tube D2 is used to stabilize the voltage at a safe voltage to prevent the MOSFET tube Q1 from being damaged by excessive voltage;

[0036] When the power supply is not over-voltage, transistor Q2 is not conducting, and the power supply VCC1 cannot flow to the base of transistor Q3 through R5. Transistor Q3 is not conducting. At this time, VCC1 is divided into the gate of MOSFET tube Q1 through resistors R2 and R4 in series. There is a voltage difference between the gate and source of MOSFET tube Q1, which makes (U GS >0), MOSFET tube Q1 is turned on, forming a loop so that the power can be output.

[0037] In addition, by adjusting the voltage stabilization value of the voltage stabilizing diode D3, the overvoltage range of the circuit can be adjusted.

[0038] Working status indication circuit: includes light emitting diode D4 and resistor R10, VCC1 is connected to light emitting diode D4, resistor R10 in sequence, connected to the drain of MOSFET tube Q1 and the negative terminal of power supply output.

[0039] Working principle: When there is no overvoltage or reverse connection in the system, MOSFET tube Q1 is turned on, VCC1 forms a loop through light-emitting diode D4, resistor R10, drain and source of MOSFET tube Q1 to GND, and indicator light D4 is lit; when there is overvoltage or reverse connection in the system, indicator light D4 is off, thereby reminding the operator whether the circuit is working normally.

[0040] When the circuit works normally, transistor Q5 is in the on state, and VCC is directly connected to the subsequent VCC1 through resistor R12.

[0041] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A reverse connection and overvoltage protection circuit, characterized in that: The invention comprises a reverse connection prevention circuit, an overcurrent prevention and current limiting circuit, an overvoltage prevention circuit and a working status indication circuit which are connected in sequence. The overcurrent prevention and current limiting circuit comprises transistors Q5, Q6, resistors R12 and R13. The base of the transistor Q6 is connected to the emitter of the transistor Q5, the collector of the transistor Q6 is connected to the base of the transistor Q5, the collector of the transistor Q6 and the base of the transistor Q5 are grounded through the resistor R13, one end of the resistor R12 is connected to the emitter of the transistor Q5, and the other end is connected to the emitter of the transistor Q6 and then connected to the power supply VCC end, and the collector of the transistor Q5 is connected to the subsequent overvoltage prevention circuit.

2. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that: The resistor R12 is an adjustable resistor.

3. The reverse connection and overvoltage protection circuit according to claim 1, characterized in that: The anti-reverse connection circuit includes a MOSFET tube Q4, a resistor R1, a resistor R3, a capacitor C1 and a voltage-stabilizing diode D1. The resistors R1 and R3 are connected in series between VCC and the source of the MOSFET tube Q4. The drain of the MOSFET tube Q4 is connected to the node between the resistors R1 and R3. The other end of the resistor R1 serves as the positive end of the power input. The voltage-stabilizing diode D1 and the capacitor C1 are connected in parallel between the gate and the source of the MOSFET tube Q4. The negative end of the voltage-stabilizing diode D1 is connected to the gate of the MOSFET tube Q4. One end of the drain of the MOSFET tube Q4 serves as the negative end of the power input and is grounded.

4. The reverse connection and overvoltage protection circuit according to claim 3, characterized in that: The reverse connection protection circuit also includes a resistor R9 and a capacitor C3. The capacitor C3 and the resistor R9 are connected in series and connected between the drain and the source of the MOSFET tube Q4 to form an RC peak protection circuit.

5. The reverse connection and overvoltage protection circuit according to claim 3, characterized in that: The overvoltage protection circuit includes a MOSFET tube Q1, a triode Q2, Q3, resistors R2, R4, R5, R6, R7, R8, R10 and a voltage stabilizing diode D3. The emitter of the triode Q2 is connected to the collector of the triode Q5 and VCC1 at the same time. VCC1 is connected to the source of the MOSFET tube Q4 through a series resistor R6 and a voltage stabilizing diode D3. The base of the triode Q2 is connected to the node between the cathode of the voltage stabilizing diode D3 and the resistor R6 through a resistor R8. The collector of the triode Q2 is connected to the source of the MOSFET tube Q4 through a series resistor R5 and R7. The node between resistors R5 and R7 is connected to the base of transistor Q3, VCC1 is connected to the first end of resistor R2, the second end of resistor R2 is connected to the source of MOSFET tube Q4 through resistor R4, the node between resistor R2 and resistor R4 is connected to the collector of transistor Q3, the collector of transistor Q3 is connected to the gate of MOSFET tube Q1, the emitter of transistor Q3 is connected to the source of MOSFET tube Q1 and connected to the source of MOSFET tube Q4, the first end of resistor R2 serves as the positive end of power output, and the drain of MOSFET tube Q1 serves as the negative end of power output.

6. The reverse connection and overvoltage protection circuit according to claim 5, characterized in that: A resistor R11 and a capacitor C4 are connected in series between the source and the drain of the MOSFET tube Q1 to form an RC spike protection circuit.

7. The reverse connection and overvoltage protection circuit according to claim 5, characterized in that: The voltage zener diode D2 and the capacitor C2 are connected in parallel between the gate and the source of the MOSFET tube Q1, and the cathode of the voltage zener diode D2 is connected to the gate of the MOSFET tube Q1.

8. The reverse connection and overvoltage protection circuit according to claim 5, characterized in that: The voltage stabilization value of the voltage stabilizing diode D3 is adjustable.

9. The reverse connection and overvoltage protection circuit according to claim 5, characterized in that: The working state indicating circuit comprises a light emitting diode D4 and a resistor R10, and VCC1 is sequentially connected to the light emitting diode D4, the resistor R10, the drain of the MOSFET tube Q1 and the negative terminal of the power output.

10. The reverse connection and overvoltage protection circuit according to any one of claims 1 to 9, characterized in that: The transistors Q5 and Q6 are PNP transistors, and the MOSFETs are all N-channel MOSFETs.

Images