A dual protection circuit

Abstract

The application relates to the technical field of protection circuits, in particular to a double protection circuit which comprises a polarity reverse connection protection circuit, a voltage reduction and stabilization circuit and an output protection circuit; the input end of the polarity reverse connection protection circuit is connected with a power supply of a power supply system, the polarity reverse connection protection circuit is used for preventing current from flowing into a later-stage circuit when reverse connection occurs; the voltage reduction and stabilization circuit is used for reducing and stabilizing input high voltage and outputting current to the output protection circuit to supply power for the output protection circuit; the output end of the voltage reduction and stabilization circuit is connected with the input end of the output protection circuit. The application has the advantages of ingenious design, prevention of positive and negative voltage reverse connection from burning the circuit, provision of a required power supply voltage for a product circuit by the voltage reduction and stabilization circuit, protection control of a very small change voltage signal by the output protection circuit after the voltage signal enters an operational amplifier for amplification, double protection provided by a MOS tube, improvement of product safety, and normal protection of another path when a single protection loop of the product fails.

Description

Technical Field

[0001] This invention relates to the field of protection circuit technology, and in particular to a dual protection circuit. Background Technology

[0002] When low-voltage, high-current products are in operation, component malfunctions may occur. In conventional single protection circuits, the protection function may fail when a component in the protection circuit malfunctions, leading to unnecessary safety accidents. Therefore, there is an urgent need for a dual protection circuit to improve product safety. Summary of the Invention

[0003] This invention addresses the technical problem in existing technologies where, when components in a conventional single protection circuit malfunction, the product's protection function fails, leading to unnecessary safety accidents. It provides a dual protection circuit.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] This invention provides a dual protection circuit, including a reverse polarity protection circuit, a step-down voltage regulator circuit, and an output protection circuit;

[0006] The input terminal of the polarity reverse connection protection circuit is connected to the power supply system. The polarity reverse connection protection circuit is used to prevent current from flowing into the subsequent circuit when the polarity is reversed.

[0007] The output terminal of the polarity reverse protection circuit is connected to the input terminal of the buck regulator circuit. The buck regulator circuit is used to step down the input high voltage and then regulate the output current to power the output protection circuit.

[0008] The output terminal of the buck regulator circuit is connected to the input terminal of the output protection circuit. The output protection circuit includes a sampling module, an operational amplifier module, and a control module connected in sequence. When the downstream circuit experiences overcurrent or circuit failure, the sampling module amplifies the detected voltage signal through the operational amplifier module and sends it to the control module. The control module is used to interrupt the voltage output.

[0009] The polarity reverse connection protection circuit includes resistors R1 and R2, a Zener diode Z1, and a MOSFET Q1. The drain of the MOSFET Q1 is connected to the power supply of the power system. The source of the MOSFET Q1 is connected to one end of resistor R2 and the cathode of Zener diode Z1. One end of resistor R1, the other end of resistor R2, and the anode of Zener diode Z1 are connected to the gate of MOSFET Q1, respectively. The other end of resistor R1 is grounded.

[0010] A capacitor EC1 is connected in parallel between the step-down voltage regulator circuit and the polarity reverse protection circuit.

[0011] The step-down voltage regulator circuit includes a step-down voltage regulator chip U1, a capacitor C1, and a capacitor C2. One end of the capacitor C1 is connected to the input terminal of the step-down voltage regulator chip U1, and the other end of the capacitor C1 is grounded. The capacitor C2 is connected to the output terminal of the step-down voltage regulator chip U1, and the output terminal of the step-down voltage regulator chip U1 is connected to the output protection circuit. The other end of the capacitor C2 is grounded.

[0012] The output protection circuit includes an MCU chip U3, an operational amplifier U2, an LED1, diodes D1, D2, D3, and D4, resistors R3, R4, R5, R6, R7, R8, R10, R12, R14, R15, R16, R18, R19, R20, and R21, an electronic resistor R22, an NTC converter, MOSFETs Q2 and Q3, transistors Q4 and Q5, a SCR Q6, a transistor Q7, and a Zener diode ZU1. Pin RA2 of the MCU chip U3 is connected to the anode of LED1. One end of resistor R12 and one end of resistor R16 are respectively connected to the cathode of LED1. The other end of resistor R12 is connected to the base of transistor Q4. The collector of transistor Q4 is connected to one end of resistor R15, and the other end of resistor R15 is connected to... The gate of MOSFET Q2 is connected to one end of resistor R14, and the other end of resistor R14 is connected to the source of MOSFET Q2. The other end of resistor R16 is connected to the base of transistor Q5. The emitter of transistor Q5 is connected to the emitter of transistor Q4. The collector of transistor Q5 is connected to one end of resistor R19. The other end of resistor R19 is connected to one end of resistor R18 and the gate of MOSFET Q3. The other end of resistor R18 is connected to the drain of MOSFET Q2 and the source of MOSFET Q3. The drain of MOSFET Q3 is connected to an external load. The emitter of transistor Q4 is connected to one end of resistor R3. The other end of resistor R3 is connected to one end of resistor R5 and one end of resistor R4. The other end of resistor R5 is connected to the INA+ pin of operational amplifier U2. One end of resistor R3 is also connected to the V- pin of operational amplifier U2. The other end of resistor R4 is connected to one end of resistor R6. The other end of resistor R6 is connected to the INB+ pin of operational amplifier U2.

[0013] The OUTA pin of the operational amplifier U2 is connected to the anode of diode D3 and the anode of diode D4, respectively. The cathode of diode D4 is connected to one end of resistor R10, and the other end of resistor R10 is connected to the IINA pin of operational amplifier U2.

[0014] The OUTB pin of operational amplifier U2 is connected to the anodes of diodes D1 and D2, respectively. The cathode of diode D2 is connected to one end of resistor R8. The other end of resistor R8 is connected to the INB- pin of operational amplifier U2 and one end of resistor R9. The other end of resistor R9 is connected to one end of resistor R4. The cathodes of diodes D1 and D3 are connected to one end of resistor R7, respectively. The other end of resistor R7 is connected to the emitter of transistor Q7 and one end of resistor R21, respectively. The other end of resistor R21 is connected to Zener diode ZU, respectively. The common terminal of the LED is connected to one end of the resistor R22. The output terminal of the Zener diode ZU1 is connected to the base of the transistor Q7 and the anode of the LED1. One end of the NTC is connected to the other end of the resistor R22. The input terminal of the Zener diode ZU1 is connected to the other end of the NTC. The collector of the transistor Q7 is connected to the control terminal of the thyristor Q6 and one end of the resistor R23. The anode of the thyristor Q6 is connected to the other end of the resistor R20. The cathode of the thyristor Q6 is connected to the V- pin of the operational amplifier U2 and the other end of the resistor R23.

[0015] The sampling module includes resistors R3 and R4; the operational amplifier module includes operational amplifier U2, resistors R5 and R6, diodes D1 and D3, resistors R7 and R21; and the control module includes Zener diode ZU1, NTC, transistor Q7, and silicon controlled rectifier Q6.

[0016] The operational amplifier U2 is model LM258.

[0017] The beneficial effects of this invention are:

[0018] This invention is ingeniously designed. The input polarity reverse protection can prevent the circuit from burning out due to reversed positive and negative voltages. The step-down power supply circuit can provide the power supply voltage required by the product circuit. The output protection circuit samples a very small change in voltage signal, amplifies it with an operational amplifier, and performs protection control. It also provides dual protection through a MOSFET, improving product safety and ensuring that if one protection circuit fails, another can still provide normal protection. Attached Figure Description

[0019] Figure 1 This is a circuit diagram of a dual protection circuit according to the present invention.

[0020] Figure 2 This is a circuit diagram of the polarity reverse connection protection circuit of the present invention.

[0021] Figure 3 This is a circuit diagram of the step-down voltage regulator circuit of the present invention.

[0022] Figure 4 This is a circuit diagram of the output protection circuit of the present invention.

[0023] 1. Reverse polarity protection circuit; 2. Step-down voltage regulator circuit; 3. Output protection circuit. Detailed Implementation

[0024] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention. The present invention will be described in detail below with reference to the accompanying drawings.

[0025] A dual protection circuit, such as Figures 1 to 4 As shown, it includes a polarity reverse protection circuit, a step-down voltage regulator circuit, and an output protection circuit. A capacitor EC1 is connected in parallel between the step-down voltage regulator circuit and the polarity reverse protection circuit.

[0026] In this embodiment, the input terminal of the reverse polarity protection circuit is connected to the power supply system. The reverse polarity protection circuit is used to prevent current from flowing into the subsequent circuit when reversed. The reverse polarity protection circuit includes resistors R1 and R2, a Zener diode Z1, and a MOSFET Q1. The drain of the MOSFET Q1 is connected to the power supply system. The source of the MOSFET Q1 is connected to one end of resistor R2 and the cathode of Zener diode Z1. One end of resistor R1, the other end of resistor R2, and the anode of Zener diode Z1 are connected to the gate of MOSFET Q1, respectively. The other end of resistor R1 is grounded. Specifically, when the input voltage polarity is correct, MOSFET Q1 is forward-biased through its built-in PMOS diode to supply power to the subsequent stage. The supply voltage is divided by resistors R1 and R2 to ensure that the gate voltage of MOSFET Q1 is lower than the required turn-on voltage at the source. Furthermore, the circuit uses Zener diode Z1 to regulate the voltage, keeping the gate-source voltage of MOSFET Q1 within its normal operating range. Because the internal resistance of MOSFET Q1 is very small, it can handle a large current with minimal loss after being turned on. When the input voltage is reversed, the built-in PMOS diode of MOSFET Q1 is cut off in both forward and reverse directions. Simultaneously, because the gate voltage is higher than the source voltage, the PMOS diode of MOSFET Q1 cannot conduct. Therefore, when a reverse voltage is applied, MOSFET Q1 is not conducting, resulting in no output from the circuit and protection against damage.

[0027] In this embodiment, the output terminal of the polarity reverse protection circuit is connected to the input terminal of the buck regulator circuit. The buck regulator circuit is used to step down the input high voltage and stabilize the output current to power the output protection circuit. The buck regulator circuit includes a buck regulator chip U1, capacitor C1, and capacitor C2. The buck regulator chip U1 is an LM7805. One end of capacitor C1 is connected to the input terminal of the buck regulator chip U1, and the other end of capacitor C1 is grounded. Capacitor C2 is connected to the output terminal of the buck regulator chip U1, and the output terminal of the buck regulator chip U1 is connected to the output protection circuit. The other end of capacitor C2 is grounded. Specifically, the buck regulator chip U1 steps down the input high voltage and stabilizes it to 5V to power the circuit of this invention.

[0028] In this embodiment, the output terminal of the buck regulator circuit is connected to the input terminal of the output protection circuit. The output protection circuit includes a sampling module, an operational amplifier module, and a control module connected in sequence. When the downstream circuit experiences overcurrent or circuit failure, the sampling module amplifies the detected voltage signal through the operational amplifier module and sends it to the control module. The control module is used to interrupt the voltage output. The output protection circuit includes an MCU chip U3, an operational amplifier U2, an LED1, diodes D1, D2, and D3, and diodes... The components include: transistor D4, resistors R3, R4, R5, R6, R7, R8, R10, R12, R14, R15, R16, R18, R19, R20, R21, resistor R22, resistor R23, NTC, MOSFET Q2, MOSFET Q3, transistor Q4, transistor Q5, SCR Q6, transistor Q7, and Zener diode ZU1; the MCU chip U3 is a PIC12F1501.

[0029] Pin RA2 of the MCU chip U3 is connected to the anode of LED1. One end of resistor R12 and one end of resistor R16 are respectively connected to the cathode of LED1. The other end of resistor R12 is connected to the base of transistor Q4. The collector of transistor Q4 is connected to one end of resistor R15. The other end of resistor R15 is connected to the gate of MOSFET Q2 and one end of resistor R14. The other end of resistor R14 is connected to the source of MOSFET Q2. The other end of resistor R16 is connected to the base of transistor Q5. The emitter of transistor Q5 is connected to the emitter of transistor Q4. The collector of transistor Q5 is connected to the cathode of LED1. One end of resistor R19 is connected to the gate of MOSFET Q3, and the other end of resistor R19 is connected to one end of resistor R18 and the gate of MOSFET Q3. The other end of resistor R18 is connected to the drain of MOSFET Q2 and the source of MOSFET Q3. The drain of MOSFET Q3 is connected to an external load. The emitter of transistor Q4 is connected to one end of resistor R3. The other end of resistor R3 is connected to one end of resistor R5 and one end of resistor R4. The other end of resistor R5 is connected to the INA+ pin of operational amplifier U2. One end of resistor R3 is also connected to the V- pin of operational amplifier U2. The other end of resistor R4 is connected to one end of resistor R6. The other end of resistor R6 is connected to the INB+ pin of operational amplifier U2.

[0030] The OUTA pin of the operational amplifier U2 is connected to the anode of diode D3 and the anode of diode D4, respectively. The cathode of diode D4 is connected to one end of resistor R10, and the other end of resistor R10 is connected to the IINA pin of operational amplifier U2.

[0031] The OUTB pin of operational amplifier U2 is connected to the anodes of diodes D1 and D2, respectively. The cathode of diode D2 is connected to one end of resistor R8. The other end of resistor R8 is connected to the INB- pin of operational amplifier U2 and one end of resistor R9. The other end of resistor R9 is connected to one end of resistor R4. The cathodes of diodes D1 and D3 are connected to one end of resistor R7, respectively. The other end of resistor R7 is connected to the emitter of transistor Q7 and one end of resistor R21, respectively. The other end of resistor R21 is connected to the common terminal of Zener diode ZU1 and one end of resistor R22, respectively. The output terminal of Zener diode ZU1 is connected to the base of transistor Q7 and the anode of LED1, respectively. The NTC... One end of the Zener diode ZU1 is connected to the other end of the NTC. The collector of the transistor Q7 is connected to the control terminal of the thyristor Q6 and one end of the resistor R23. The anode of the thyristor Q6 is connected to the other end of the resistor R20. The cathode of the thyristor Q6 is connected to the V-pin of the operational amplifier U2 and the other end of the resistor R23. The sampling module includes resistors R3 and R4. The operational amplifier module includes operational amplifier U2, resistors R5 and R6, diodes D1 and D3, resistors R7 and R21. The control module includes the Zener diode ZU1, the NTC, the transistor Q7, and the thyristor Q6.

[0032] Specifically, the working principle is as follows: When the circuit is powered on, the buck regulator circuit starts to supply power normally, and the MCU chip U3 also starts to work normally. The high level output from the RA2 pin of the MCU chip is limited by resistor R20, and then drives transistors Q4 and Q5 to conduct through LED1 and resistors R12 and R16 respectively. The conduction of transistors Q4 and Q5 pulls down the gate potential of MOSFETs Q2 and Q3. The series voltage divider of resistors R14 and R15 and resistors R18 and R19 uses the gate of MOSFETs Q2 and Q3 to reach the PMOS conduction voltage point and conduct. Therefore, the input voltage is output to the subsequent stage through the conducting MOSFETs Q2 and Q3.

[0033] When there is overcurrent or short circuit in the subsequent stage, the weak voltage signal detected by the two series-connected resistors R3 and R4 is sent to operational amplifier U2 for voltage amplification via resistors R5 and R6. Resistors R3, R4, R5, and R6 are used to set the amplification factor of the two channels of operational amplifier U2. The amplified voltage is then sent to the voltage reference pin ZU1 via diodes D1 and D3, resistors R7 and R21. Diodes D1 and D3 are the isolation diodes for the two operational amplifier outputs, but due to the temperature drift of diodes, diodes D2 and D4 are connected in series in the amplification factor setting circuit. As a temperature drift compensation, its working principle is that when the temperature is high, the forward voltage drop of diodes D1 and D3 will decrease, which will increase the output voltage of op-amp U2. However, since diodes D2 and D4 are also connected in series in the amplification factor setting circuit, the forward voltage drop of diodes D3 and D4 will also decrease. At this time, the voltage factor of the amplifier circuit is reduced due to the lower forward voltage drop of diodes D3 and D4, which strengthens the negative feedback of the amplification factor and makes the amplification factor smaller. In the circuit, diodes D1 and D2 are complementary, and diodes D3 and D4 are complementary. After the diodes are complementary, it is equivalent to temperature drift complementarity, so the effect of temperature drift due to diodes is canceled.

[0034] Additionally, resistor R22 is used to adjust the reference point voltage of Zener diode ZU1, and NTC is used for temperature compensation adjustment. When the reference voltage of Zener diode ZU1 reaches 2.5V, Zener diode ZU1 conducts, pulling down the base voltage of transistor Q7, causing transistor Q7 to conduct. The voltage of transistor Q7 triggers the SCR Q6 to conduct and pull down the positive voltage of LED1. Since LED1 is a red LED, its conduction voltage is about 1.5V, while the voltage drop after the SCR Q6 conducts is about 1V, so LED1 does not conduct. The bases of transistors Q4 and Q5 are not conducting because there is no driving voltage. MOSFETs Q2 and Q3 are also not conducting because transistors Q4 and Q5 are not conducting and are pulled up to a high level by resistors R14 and R18. Therefore, there is no output voltage, achieving the purpose of protecting the subsequent circuit.

[0035] After the overcurrent or short circuit in the subsequent stage is cleared, to allow the circuit to automatically resume output, the voltage on the SCR-controlled Q6 needs to be released (because the SCR characteristic is that once triggered, it will remain locked on as long as there is current at the AK terminal). Since pin RA4 of MCU chip U3 is connected to the positive terminal of LED1, when the AD pin detects that the positive terminal voltage of LED1 is lower than 1.5V, pin RA2 of MCU chip U3 will turn off for 3 seconds according to the set logic and then output a high level again. During the 3-second off period of pin RA2 of MCU chip U3, the SCR-controlled Q6... Since there is no voltage and no sustaining current, the high level output from the RA2 pin of the MCU chip U3 is limited by resistor R20, and then drives transistors Q4 and Q5 to conduct through LED1, resistors R12 and R16 respectively. The conduction of transistors Q4 and Q5 pulls the gate potential of MOSFETs Q2 and Q3 low to reach the PMOS turn-on voltage point and turn them on. Therefore, the input voltage is output to the subsequent stage again through the conducting MOSFETs Q2 and Q3. The same operation is performed if there is an overcurrent or short circuit protection.

[0036] In this embodiment, the operational amplifier U2 is an LM258.

[0037] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes, and modifications made to the above embodiments based on the present invention without departing from the scope of the present invention are within the scope of the present invention.

Claims

1. A dual protection circuit, characterized by: This includes a reverse polarity protection circuit, a step-down voltage regulator circuit, and an output protection circuit; The input terminal of the polarity reverse connection protection circuit is connected to the power supply system. The polarity reverse connection protection circuit is used to prevent current from flowing into the subsequent circuit when the polarity is reversed. The output terminal of the polarity reverse protection circuit is connected to the input terminal of the buck regulator circuit. The buck regulator circuit is used to step down the input high voltage and then regulate the output current to power the output protection circuit. The output terminal of the step-down voltage regulator circuit is connected to the input terminal of the output protection circuit. The output protection circuit includes a sampling module, an operational amplifier module, and a control module connected in sequence. When the downstream circuit is overcurrent or short-circuited, the sampling module amplifies the detected voltage signal through the operational amplifier module and sends it to the control module. The control module is used to interrupt the voltage output. The output protection circuit includes an MCU chip U3, an operational amplifier U2, an LED1, diodes D1, D2, D3, and D4, resistors R3, R4, R5, R6, R7, R8, R10, R12, R14, R15, R16, R18, R19, R20, and R21, an electronic resistor R22, an electronic resistor R23, an NTC, MOSFETs Q2 and Q3, transistors Q4 and Q5, a silicon controlled rectifier (SCR) Q6, a transistor Q7, and a Zener diode ZU1. Pin RA2 of the MCU chip U3 is connected to the anode of LED1. One end of resistor R12 and one end of resistor R16 are respectively connected to the cathode of LED1. The other end of resistor R12 is connected to the base of transistor Q4. The collector of transistor Q4 is connected to one end of resistor R15. The other end of resistor R15 is connected to the gate of MOSFET Q2 and one end of resistor R14. The other end of resistor R14 is connected to the source of MOSFET Q2. The other end of resistor R16 is connected to the base of transistor Q5. The emitter of transistor Q5 is connected to the emitter of transistor Q4. The collector of transistor Q5 is connected to one end of resistor R19. The other end of resistor R19 is connected to one end of resistor R18 and the gate of MOSFET Q3. The other end of resistor R18 is connected to the drain of MOSFET Q2 and the source of MOSFET Q3. The drain of MOSFET Q3 is connected to an external load. The emitter of transistor Q4 is connected to one end of resistor R3. The other end of resistor R3 is connected to one end of resistor R5 and one end of resistor R4. The other end of resistor R5 is connected to the INA+ pin of operational amplifier U2. One end of resistor R3 is also connected to the V- pin of operational amplifier U2. The other end of resistor R4 is connected to one end of resistor R6. The other end of resistor R6 is connected to the INB+ pin of operational amplifier U2. The OUTA pin of the operational amplifier U2 is connected to the anode of diode D3 and the anode of diode D4, respectively. The cathode of diode D4 is connected to one end of resistor R10, and the other end of resistor R10 is connected to the INA- pin of operational amplifier U2. The OUTB pin of operational amplifier U2 is connected to the anodes of diodes D1 and D2, respectively. The cathode of diode D2 is connected to one end of resistor R8. The other end of resistor R8 is connected to the INB- pin of operational amplifier U2 and one end of resistor R9. The other end of resistor R9 is connected to one end of resistor R4. The cathodes of diodes D1 and D3 are connected to one end of resistor R7, respectively. The other end of resistor R7 is connected to the emitter of transistor Q7 and one end of resistor R21, respectively. The other end of resistor R21 is connected to the common terminal of Zener diode ZU1 and one end of resistor R22, respectively. The output terminal of Zener diode ZU1 is connected to the base of transistor Q7 and the anode of LED1, respectively. One end of the NTC is connected to the other end of resistor R22. The input terminal of the transistor Q7 is connected to the other end of the NTC. The collector of the transistor Q7 is connected to the control terminal of the thyristor Q6 and one end of the resistor R23. The anode of the thyristor Q6 is connected to the other end of the resistor R20. The cathode of the thyristor Q6 is connected to the V-pin of the operational amplifier U2 and the other end of the resistor R23.

2. A dual protection circuit according to claim 1, characterized in that: The polarity reverse connection protection circuit includes resistors R1 and R2, a Zener diode Z1, and a MOSFET Q1. The drain of the MOSFET Q1 is connected to the power supply of the power system. The source of the MOSFET Q1 is connected to one end of resistor R2 and the cathode of Zener diode Z1. One end of resistor R1, the other end of resistor R2, and the anode of Zener diode Z1 are connected to the gate of MOSFET Q1, respectively. The other end of resistor R1 is grounded.

3. The dual protection circuit of claim 1, wherein: A capacitor EC1 is connected in parallel between the step-down voltage regulator circuit and the polarity reverse protection circuit.

4. The dual protection circuit of claim 1, wherein: The buck regulator circuit includes a buck regulator chip U1, a capacitor C1, and a capacitor C2. One end of the capacitor C1 is connected to the input terminal of the buck regulator chip U1, and the other end of the capacitor C1 is grounded. The capacitor C2 is connected to the output terminal of the buck regulator chip U1, and the output terminal of the buck regulator chip U1 is connected to the output protection circuit. The other end of the capacitor C2 is grounded.

5. The dual protection circuit of claim 1, wherein: The sampling module includes resistors R3 and R4; the operational amplifier module includes operational amplifier U2, resistors R5 and R6, diodes D1 and D3, resistors R7 and R21; the control module includes Zener diode ZU1, the NTC, transistor Q7 and the thyristor Q6.

6. A dual protection circuit according to claim 1 or 5, characterized in that: The operational amplifier U2 is model LM258.

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