Voltage protection circuit

Abstract

The invention discloses a voltage protection circuit. The protection circuit comprises a high-voltage detection circuit, a low-voltage detection circuit, a logic control circuit, a time delay circuit and an on-off execution circuit, the output end of the high-voltage detection circuit and the output end of the low-voltage detection circuit are respectively connected to the input end of the logic control circuit, and the output end of the logic control circuit is connected to the control end of the on-off execution circuit through the time delay circuit; the circuit is used for stably outputting an input voltage to a load end in a normal range, when the input voltage exceeds a preset high-voltage or low-voltage threshold value, the output is automatically cut off, a visual alarm is provided through the state indication circuit, and the circuit can be used for realizing the intelligent control of the input voltage through a precise voltage detection module, a logic control module, a delay filtering module and an on-off execution module. The problems that in the prior art, protection precision is not high, response characteristics are not ideal, and adaptability to transient voltage fluctuation is poor are solved.

Description

Technical Field

[0001] This invention relates to the technical field of electronic circuits, specifically to a voltage protection circuit. Background Technology

[0002] In practical applications, power supply circuits often face a variety of unstable factors. Circuits designed to deal with these factors are called protection circuits, such as overcurrent protection, overvoltage protection, overheat protection, no-load protection, and short-circuit protection circuits.

[0003] In existing electronic devices, especially those with batteries, power supply protection designs are often quite simple. A common practice is to only provide high and low voltage status indicators during charging input, lacking the ability to automatically cut off the input power in case of abnormal voltage. This can lead to the device operating under unstable or abnormal voltage conditions, potentially causing device damage or even safety accidents.

[0004] To achieve automatic high and low voltage protection, existing technologies have adopted protection circuit solutions based on discrete components such as transistors, Zener diodes, and comparators. Although such solutions reduce costs and simplify the structure to some extent, they still have problems such as low protection accuracy, unsatisfactory response characteristics, and poor adaptability to transient voltage fluctuations. Especially near the voltage critical point, they are prone to malfunctions or protection failures due to circuit parameter drift or temperature changes, which affects the reliability and service life of the equipment. Summary of the Invention

[0005] The purpose of this invention is to provide a voltage protection circuit to solve the problems mentioned in the background art.

[0006] To achieve the above objectives, the present invention provides the following technical solution: a voltage protection circuit, which includes a high voltage detection circuit, a low voltage detection circuit, a logic control circuit, a delay circuit, and an on / off execution circuit; The output terminals of the high-voltage detection circuit and the low-voltage detection circuit are respectively connected to the input terminal of the logic control circuit, and the output terminal of the logic control circuit is connected to the control terminal of the on / off execution circuit through a delay circuit. The high-voltage detection circuit is used to detect the input voltage in real time and output a first trigger signal when the input voltage is higher than a first precision preset threshold. The low-voltage detection circuit is used to detect the input voltage in real time and output a second trigger signal when the input voltage is lower than the second precision preset threshold. The logic control circuit is used to output a shutdown control signal when it receives a first trigger signal or a second trigger signal; The delay circuit is used to delay the turn-off control signal and filter out interference caused by transient voltage fluctuations; The on / off execution circuit is used to cut off the output voltage when a delayed shutdown control signal is received.

[0007] Preferably, the high-voltage detection circuit includes a precision voltage reference source, a first error amplifier, a first voltage divider resistor, and a second voltage divider resistor; Wherein, the first end of the first voltage divider resistor is connected to the positive terminal of the input voltage, the second end of the first voltage divider resistor is connected together with the first end of the second voltage divider resistor and the non-inverting input terminal of the first error amplifier, and the second end of the second voltage divider resistor is grounded; The inverting input of the first error amplifier is connected to a precision voltage reference source, and the output of the first error amplifier serves as the output of the high-voltage detection circuit, outputting a first trigger signal.

[0008] Preferably, the low-voltage detection circuit includes a second error amplifier, a third voltage divider resistor, and a fourth voltage divider resistor; Among them, the first end of the third voltage divider resistor is connected to the positive terminal of the input voltage, the second end of the third voltage divider resistor is connected together with the first end of the fourth voltage divider resistor and the inverting input terminal of the second error amplifier, and the second end of the fourth voltage divider resistor is grounded. The non-inverting input of the second error amplifier is connected to an adjustable reference voltage source to precisely set the second precision preset threshold. The output of the second error amplifier serves as the output of the low-voltage detection circuit, outputting the second trigger signal.

[0009] Preferably, the logic control circuit includes an OR gate circuit; The first input terminal of the OR gate is connected to the output terminal of the first error amplifier, and the second input terminal of the OR gate is connected to the output terminal of the second error amplifier. The output terminal of the OR gate outputs a shutdown control signal.

[0010] Preferably, the delay circuit includes a resistor-capacitor integration circuit and a Schmitt trigger; The input of the resistor-capacitor integrator circuit is connected to the output of the OR gate circuit, and is used to integrate and delay the turn-off control signal; the input of the Schmitt trigger is connected to the output of the resistor-capacitor integrator circuit, and is used to output the delayed signal after waveform shaping to the on / off execution circuit.

[0011] Preferably, the on / off execution circuit includes a driving transistor and a P-channel MOSFET; The base of the driving transistor is connected to the output of the Schmitt trigger through a current-limiting resistor, the emitter of the driving transistor is grounded, and the output electrode of the driving transistor is connected to the gate of the P-channel MOSFET; the source of the P-channel MOSFET is connected to the positive terminal of the input voltage, and the drain serves as the voltage output terminal. When the driving transistor is turned on, the gate of the P-channel MOSFET is pulled low to a low level and turns on. When the driving transistor is turned off, the gate of the P-channel MOSFET becomes high due to the pull-up resistor and turns off.

[0012] Preferably, the protection circuit further includes a status indication circuit, which is connected between the output of the logic control circuit and ground, and is used to provide visual indication when the circuit is in the protection off state.

[0013] Preferably, the status indication circuit includes an indicator light and a current-limiting resistor. The indicator light and the current-limiting resistor are connected in series, with one end connected to the output terminal of the logic control circuit and the other end grounded.

[0014] Preferably, the adjustable reference voltage source is composed of a precision adjustable voltage regulator and its peripheral resistor network, used to achieve fine-tuning of the second precision preset threshold.

[0015] Preferably, the voltage divider resistors in the high-voltage detection circuit and the low-voltage detection circuit are metal film resistors.

[0016] Compared with the prior art, the beneficial effects of the present invention are: This invention provides a fully hardware-implemented voltage protection circuit for stable output to the load within the normal input voltage range. When the input voltage exceeds a preset high or low voltage threshold, the output is automatically shut off, and a visual alarm is provided through a status indicator circuit. This circuit solves the problems of low protection accuracy, unsatisfactory response characteristics, and poor adaptability to transient voltage fluctuations in existing technologies through modules such as precision voltage detection, logic control, delay filtering, and on / off execution. Especially near the voltage critical point, through high-precision components and delay design, it avoids malfunctions or protection failures caused by parameter drift or temperature changes, thereby improving the reliability and service life of the equipment. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the voltage protection circuit module of the present invention. Detailed Implementation

[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0019] Please see Figure 1The present invention provides a technical solution: The embodiments of the present invention propose a voltage protection circuit for outputting to the load end within the normal range of the input voltage. When the input voltage exceeds the preset high voltage or low voltage threshold, it realizes the full hardware shutdown output function. The voltage protection circuit specifically includes a high voltage detection circuit, a low voltage detection circuit, a logic control circuit, a delay circuit, an on / off execution circuit, and a status indication circuit. The output terminals of the high-voltage detection circuit and the low-voltage detection circuit are respectively connected to the input terminals of the logic control circuit. The output terminal of the logic control circuit is connected to the control terminal of the on / off execution circuit through a delay circuit. The high-voltage detection circuit is used to detect the input voltage in real time and outputs a first trigger signal when the input voltage is higher than a first precision preset threshold. The low-voltage detection circuit is used to detect the input voltage in real time and outputs a second trigger signal when the input voltage is lower than a second precision preset threshold. The logic control circuit is used to output a shutdown control signal when it receives the first or second trigger signal. The delay circuit is used to delay the shutdown control signal to filter out interference caused by transient voltage fluctuations. The on / off execution circuit is used to cut off the output voltage when it receives the delayed shutdown control signal. The status indication circuit is connected between the output terminal of the logic control circuit and ground to provide visual indication when the circuit is in a protected shutdown state.

[0020] In one specific embodiment, the high-voltage detection circuit includes a precision voltage reference source D1, a first error amplifier U1, a first voltage divider resistor R1, and a second voltage divider resistor R2. The first terminal of the first voltage divider resistor R1 is connected to the positive terminal VIN of the input voltage. The second terminal of the first voltage divider resistor R1 is connected together with the first terminal of the second voltage divider resistor R2 and the non-inverting input terminal of the first error amplifier U1. The second terminal of the second voltage divider resistor R2 is grounded to GND. The inverting input terminal of the first error amplifier U1 is connected to the cathode of the precision voltage reference source D1, the anode of D1 is grounded, and the output terminal of the first error amplifier U1 serves as the output terminal of the high-voltage detection circuit, outputting a first trigger signal.

[0021] The high-voltage detection circuit monitors the input voltage in real time. When the input voltage exceeds the first precision preset threshold, it outputs the first trigger signal. The voltage divider resistors R1 and R2 divide the input voltage VIN to obtain a sampled voltage, which is sent to the non-inverting input of U1 and compared with the voltage value of the precision voltage reference D1 at the inverting input. When the sampled voltage exceeds the reference voltage of D1, U1 outputs a high-level first trigger signal, indicating that the input voltage is too high. The use of the precision voltage reference source D1 and metal film resistors R1 and R2 ensures the accuracy and temperature stability of the high-voltage threshold, avoiding the threshold error caused by Zener diode drift in traditional discrete component solutions.

[0022] In one specific embodiment, the low-voltage detection circuit includes a second error amplifier U2, a third voltage divider resistor R3, and a fourth voltage divider resistor R4. The first terminal of the third voltage divider resistor R3 is connected to the positive terminal VIN of the input voltage. The second terminal of the third voltage divider resistor R3 is connected together with the first terminal of the fourth voltage divider resistor R4 and the inverting input terminal of the second error amplifier U2. The second terminal of the fourth voltage divider resistor R4 is grounded to GND. The non-inverting input terminal of the second error amplifier U2 is connected to the output terminal of the adjustable reference voltage source U3. The output terminal of the second error amplifier U2 serves as the output terminal of the low-voltage detection circuit, outputting a second trigger signal.

[0023] The low-voltage detection circuit monitors the input voltage in real time. When the input voltage is lower than the second precision preset threshold, it outputs a second trigger signal. Voltage divider resistors R3 and R4 divide the input voltage VIN to obtain a sampled voltage, which is sent to the inverting input of U2 and compared with the output voltage of the adjustable reference voltage source U3 at the non-inverting input. When the sampled voltage is lower than the reference voltage of U3, U2 outputs a high-level second trigger signal, indicating that the input voltage is too low. The adjustable reference voltage source U3 consists of a precision adjustable voltage regulator and its peripheral resistor network, allowing fine-tuning of the second precision preset threshold to adapt to the needs of different application scenarios. The use of metal film resistors R3 and R4 further improves the voltage division accuracy and reduces the impact of temperature changes on the threshold.

[0024] In one specific embodiment, the logic control circuit includes an OR gate circuit U4, the first input terminal of the OR gate circuit U4 is connected to the output terminal of the first error amplifier U1, the second input terminal of the OR gate circuit U4 is connected to the output terminal of the second error amplifier U2, and the output terminal of the OR gate circuit U4 outputs a shutdown control signal.

[0025] The function of the logic control circuit is to integrate high voltage and low voltage detection signals. When any trigger signal is received, it immediately outputs a shutdown control signal. When any input terminal of U4 is high from U1 or U2, it indicates that the input voltage exceeds the normal range. U4 outputs a high-level shutdown control signal. This OR logic design ensures a fast response under overvoltage or undervoltage conditions, achieving comprehensive protection.

[0026] In one specific embodiment, the delay circuit includes a resistor-capacitor integrator circuit and a Schmitt trigger U5. The input of the resistor-capacitor integrator circuit is connected to the output of the OR gate circuit U4, and the output of the resistor-capacitor integrator circuit is connected to the input of the Schmitt trigger U5. The output of the Schmitt trigger U5 is connected to the control terminal of the on / off execution circuit. The resistor-capacitor integrator circuit includes a resistor R5 and a capacitor C1. The first end of the resistor R5 is connected to the output of the OR gate circuit U4, and the second end of the resistor R5 is connected together with the first end of the capacitor C1 and the input of the Schmitt trigger U5. The second end of the capacitor C1 is grounded to GND.

[0027] The function of the delay circuit is to delay and shape the turn-off control signal, and filter out interference caused by transient voltage fluctuations. When U4 outputs the turn-off control signal, C1 is charged through R5, causing the voltage at the input of Schmitt trigger U5 to rise slowly until it exceeds the positive threshold of U5. Then, U5 outputs the flipped signal. This RC integral delay effectively avoids false turn-off caused by instantaneous fluctuations in the input voltage. At the same time, Schmitt trigger U5 shapes the waveform of the delayed signal to eliminate jitter and ensure the stable operation of the on / off execution circuit.

[0028] In one specific embodiment, the switching execution circuit includes a driving transistor Q1 and a P-channel MOSFET Q2. The base of the driving transistor Q1 is connected to the output terminal of the Schmitt trigger U5 through a current-limiting resistor R6. The emitter of the driving transistor Q1 is grounded to GND. The collector of the driving transistor Q1 is connected to the gate of the P-channel MOSFET Q2 and the first terminal of the pull-up resistor R7. The source of the P-channel MOSFET Q2 is connected to the positive input voltage terminal VIN, and the drain of the P-channel MOSFET Q2 serves as the voltage output terminal VOUT. The second terminal of the pull-up resistor R7 is connected to the positive input voltage terminal VIN.

[0029] The function of the on / off execution circuit is to cut off the output voltage when a delayed shutdown control signal is received. When the Schmitt trigger U5 outputs a high level, it drives transistor Q1 to conduct, pulling the gate of P-channel MOSFET Q2 low to a low level, and Q2 conducts. When the gate of the P-channel MOSFET is low, it conducts, and the output voltage VOUT is normal. When U5 outputs a low level, indicating that the shutdown control signal is valid, Q1 is turned off, and the gate of P-channel MOSFET Q2 is pulled high through the pull-up resistor R7, turning off Q2 and thus cutting off the output voltage. This design achieves full hardware shutdown, with fast response speed, and the low on-resistance of P-channel MOSFET Q2 reduces power loss.

[0030] In one specific embodiment, the status indication circuit includes an indicator LED1 and a current-limiting resistor R8. The anode of the indicator LED1 is connected to the output terminal of the OR gate circuit U4 in the logic control circuit, and the cathode of the indicator LED1 is grounded to GND through the current-limiting resistor R8.

[0031] The function of the status indicator circuit is to provide visual indication when the circuit is in the protection off state; when the logic control circuit outputs the off control signal, LED1 lights up, indicating that the protection action has been triggered; when the input voltage is normal, the off control signal is low level, and LED1 turns off. This indication function makes it convenient for users to monitor the circuit status in real time.

[0032] When the high-voltage detection circuit detects that the input voltage VIN is higher than the first precision preset threshold, the first error amplifier U1 outputs a high-level first trigger signal to the OR gate circuit U4, which is set by the precision voltage reference source D1 and the voltage divider resistors R1 and R2. When the low-voltage detection circuit detects that the input voltage VIN is lower than the second precision preset threshold, the second error amplifier U2 outputs a high-level second trigger signal to the OR gate circuit U4, which is set by the adjustable reference voltage source U3 and the voltage divider resistors R3 and R4.

[0033] When the OR gate U4 receives any trigger signal, it outputs a high-level shutdown control signal. This signal is then integrated by the delay circuit, R5 and C1, and shaped and delayed by the Schmitt trigger U5 before being output to the on / off execution circuit.

[0034] In the on / off execution circuit, the driving transistor Q1 is turned off when the turn-off control signal is low after the delay, which causes the gate of the P-channel MOSFET Q2 to be pulled up to a high level by the pull-up resistor R7, turning off Q2 and thus cutting off the output voltage VOUT. At the same time, the LED1 of the status indicator circuit lights up to indicate the protection status. The delay circuit ensures that transient voltage fluctuations will not cause false operation, while precision components and logic control improve the accuracy and reliability of protection.

[0035] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A voltage protection circuit, characterized by: The protection circuit comprises a high-voltage detection circuit, a low-voltage detection circuit, a logic control circuit, a delay circuit and a on-off execution circuit; The output ends of the high-voltage detection circuit and the low-voltage detection circuit are connected to the input ends of the logic control circuit respectively, and the output end of the logic control circuit is connected to the control end of the on-off execution circuit through the delay circuit; The high-voltage detection circuit is used for detecting the input voltage in real time and outputting a first trigger signal when the input voltage is higher than a first precise preset threshold value; The low-voltage detection circuit is used for detecting the input voltage in real time and outputting a second trigger signal when the input voltage is lower than a second precise preset threshold value; The logic control circuit is used for outputting an off control signal when the first trigger signal or the second trigger signal is received; The delay circuit is used for delaying the off control signal and filtering out the interference caused by transient voltage fluctuation; The on-off execution circuit is used for cutting off the output voltage when the delayed off control signal is received.

2. The voltage protection circuit of claim 1, wherein: The high-voltage detection circuit comprises a precise voltage reference source, a first error amplifier, a first voltage dividing resistor and a second voltage dividing resistor; The first end of the first voltage dividing resistor is connected to the positive end of the input voltage, the second end of the first voltage dividing resistor and the first end of the second voltage dividing resistor are commonly connected to the non-inverting input end of the first error amplifier, and the second end of the second voltage dividing resistor is grounded; The inverting input end of the first error amplifier is connected to the precise voltage reference source, and the output end of the first error amplifier serves as the output end of the high-voltage detection circuit and outputs the first trigger signal.

3. The voltage protection circuit of claim 1, wherein: The low-voltage detection circuit comprises a second error amplifier, a third voltage dividing resistor and a fourth voltage dividing resistor; The first end of the third voltage dividing resistor is connected to the positive end of the input voltage, the second end of the third voltage dividing resistor and the first end of the fourth voltage dividing resistor are commonly connected to the inverting input end of the second error amplifier, and the second end of the fourth voltage dividing resistor is grounded; The non-inverting input end of the second error amplifier is connected to an adjustable reference voltage source, which is used for accurately setting the second precise preset threshold value, and the output end of the second error amplifier serves as the output end of the low-voltage detection circuit and outputs the second trigger signal.

4. The voltage protection circuit of claim 1, wherein: The logic control circuit comprises an OR gate circuit; The first input end of the OR gate circuit is connected to the output end of the first error amplifier, the second input end of the OR gate circuit is connected to the output end of the second error amplifier, and the output end of the OR gate circuit outputs the off control signal.

5. The voltage protection circuit of claim 1, wherein: The delay circuit comprises a resistor-capacitor integration circuit and a Schmitt trigger; The input end of the resistor-capacitor integration circuit is connected to the output end of the OR gate circuit, which is used for integrating and delaying the off control signal; the input end of the Schmitt trigger is connected to the output end of the resistor-capacitor integration circuit, which is used for outputting the delayed signal to the on-off execution circuit after waveform shaping.

6. The voltage protection circuit of claim 1, wherein: The on-off execution circuit comprises a driving triode and a P-channel MOS tube; The base of the driving triode is connected to the output end of the Schmitt trigger through a current-limiting resistor, the emitter of the driving triode is grounded, the output electrode of the driving triode is connected to the gate of the P-channel MOS tube, the source of the P-channel MOS tube is connected to the positive end of the input voltage, and the drain serves as the voltage output end. When the driving triode is turned on, the gate of the P-channel MOS tube is pulled to low level and turned on; when the driving triode is turned off, the gate of the P-channel MOS tube becomes high level due to the action of the pull-up resistor, thereby being turned off.

7. The voltage protection circuit of claim 1, wherein: The protection circuit further comprises a state indicating circuit connected between the output of the logic control circuit and the ground for visual indication when the circuit is in the protection-off state.

8. A voltage protection circuit according to claim 7, characterised in that: The state indicating circuit comprises an indicating lamp and a current-limiting resistor, and the indicating lamp and the current-limiting resistor are connected in series, one end of which is connected to the output of the logic control circuit and the other end is grounded.

9. The voltage protection circuit of claim 3, wherein: The adjustable reference voltage source is composed of a precision adjustable voltage stabilizer and its peripheral resistor network, for realizing fine adjustment of the second precision preset threshold value.

10. The voltage protection circuit of claim 1, wherein: The voltage dividing resistors in the high-voltage detection circuit and the low-voltage detection circuit are metal film resistors.

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