Over / under voltage protection circuit

Abstract

The present application provides an overvoltage and undervoltage protection circuit, which relates to the technical field of overvoltage and undervoltage protection. The undervoltage control subcircuit and the overvoltage control subcircuit respectively monitor the voltage of the target area. When undervoltage or overvoltage is detected, the corresponding protection subcircuit will be activated. The undervoltage protection subcircuit connects the first pin of the chip to the external low level to achieve protection, reducing the output power or completely shutting down the output. It utilizes the internal logic of the control chip and can achieve accurate undervoltage protection without complex ADC conversion. The overvoltage protection subcircuit cuts off the connection between the second pin and the external high level to achieve protection. By cutting off the external high-level connection, these pins will return to a low-level state due to the action of the internal pull-down resistor, thereby stopping the chip from working. Since there is no need to use a high-bit ADC, the quantization error and nonlinear error associated with the ADC are eliminated, while maintaining high accuracy and reducing costs, achieving a balance between accuracy and cost.

Description

Technical Field

[0001] This application relates to the field of over- and under-voltage protection technology, and more particularly to over- and under-voltage protection circuits. Background Technology

[0002] In electronic devices, power management is a crucial aspect. To protect electronic devices from voltage fluctuations, over- and under-voltage protection circuits are widely used. This protection mechanism can cut off the power supply in time when the voltage is too high or too low, thereby preventing equipment damage.

[0003] Currently, over- and under-voltage protection circuits in related technologies are usually implemented using microcontrollers or comparators. In microcontroller applications, voltage information is collected through an analog-to-digital converter (ADC), and then judgment and control are performed according to a preset threshold. In comparator applications, the collected voltage is compared with a reference voltage to achieve over- and under-voltage protection. These solutions all require corresponding external components to support the normal operation of the circuit.

[0004] However, when using microcontrollers, the different bit widths of the ADC can lead to varying degrees of temperature control error. For example, the error of an 8-bit microcontroller can reach 39mV (1 / 2). 8 The error of a 12-bit microcontroller is approximately 9.6 mV (1 / 2). 12 While increasing the number of bits in an ADC can improve accuracy, it also increases cost. Therefore, an over / under voltage protection circuit that balances accuracy and cost is needed. Summary of the Invention

[0005] This application provides an over / under voltage protection circuit to improve detection accuracy while maintaining cost.

[0006] In a first aspect, this application provides an over / under voltage protection circuit, including: an undervoltage protection circuit and an overvoltage protection circuit;

[0007] The undervoltage protection circuit includes an undervoltage control sub-circuit and an undervoltage protection sub-circuit;

[0008] The reference terminal of the undervoltage control sub-circuit is connected to the target area, the input terminal is connected to an external high-level voltage, and the output terminal is connected to the detection terminal of the undervoltage protection sub-circuit. It is used to obtain the voltage of the target area, and when the voltage of the target area is lower than the preset undervoltage protection voltage, it introduces an external high-level voltage from the input terminal and outputs it from the output terminal.

[0009] The input terminal of the undervoltage protection sub-circuit is connected to the first pin of the chip, and the output terminal is connected to an external low level. It is used to connect the first pin to an external low level when the detection terminal detects an external high level. The level of the first pin needs to be greater than the external low level.

[0010] The overvoltage protection circuit includes an overvoltage control sub-circuit and an overvoltage protection sub-circuit;

[0011] The reference terminal of the overvoltage control sub-circuit is connected to the target area, the input terminal is connected to an external high level, and the output terminal is connected to the detection terminal of the overvoltage protection sub-circuit. This is used to obtain the voltage of the target area, and when the voltage of the target area is higher than the preset overvoltage protection voltage, the output terminal switches from outputting an external high level to outputting the preset control voltage.

[0012] The input of the overvoltage protection sub-circuit is connected to an external high-level voltage, and the output is connected to the second pin of the chip. It is used to disconnect the connection between the second pin and the external high-level voltage when the preset control voltage is detected at the detection end. The voltage level of the second pin needs to be greater than that of the first pin.

[0013] By employing the above technical solution, the undervoltage control subcircuit and overvoltage control subcircuit monitor the voltage of the target area respectively. When undervoltage or overvoltage is detected, the corresponding protection subcircuit is activated. The undervoltage protection subcircuit achieves protection by connecting the chip's first pin to an external low level, reducing output power or completely shutting down the output. Utilizing the internal logic of the control chip, accurate undervoltage protection can be achieved without complex ADC conversion. The overvoltage protection subcircuit achieves protection by disconnecting the second pin from an external high level. By disconnecting the external high-level connection, these pins will return to a low level due to the internal pull-down resistors, thus stopping the chip from working. Since a high-bit ADC is not required, quantization and nonlinearity errors associated with the ADC are eliminated. Furthermore, the key control pins of the chip are directly operated instead of through a complex analog-to-digital conversion process. This direct control reduces intermediate steps and the possibility of error accumulation. Therefore, this solution maintains high accuracy while reducing costs, achieving a balance between accuracy and cost.

[0014] In conjunction with some embodiments of the first aspect, in some embodiments, the undervoltage protection circuit further includes an undervoltage differential adjustable sub-circuit;

[0015] The detection terminal of the undervoltage hysteresis adjustable sub-circuit is connected to the output terminal of the undervoltage control sub-circuit, and the input terminal is interconnected with the reference terminal and the target area of ​​the undervoltage control sub-circuit. It is used to form a feedback network between the reference terminal and the target area of ​​the undervoltage control sub-circuit when the detection terminal detects an external high level, so that the voltage obtained by the detection terminal of the undervoltage protection sub-circuit is reduced.

[0016] By adopting the above technical solution, when the undervoltage control subcircuit detects undervoltage and outputs a high level, the undervoltage hysteresis adjustable subcircuit will form a feedback network between the reference terminal and the target area of ​​the undervoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection terminal of the undervoltage protection subcircuit, which can prevent the protection circuit from frequently switching when the voltage fluctuates repeatedly near the critical point. Specifically, when the voltage recovers from the undervoltage state, it needs to reach a higher threshold before the protection state can be released. This avoids the frequent switching phenomenon that may occur during the slow voltage recovery process.

[0017] In conjunction with some embodiments of the first aspect, in some embodiments, the undervoltage protection circuit further includes an undervoltage compensation sub-circuit;

[0018] The input terminal of the undervoltage compensation sub-circuit is interconnected with the reference terminal and target area of ​​the undervoltage control sub-circuit, and the output terminal of the undervoltage compensation sub-circuit is interconnected with the input terminal and output terminal of the undervoltage control sub-circuit. This is used to slow down the rate of voltage rise when the input voltage of the undervoltage control sub-circuit increases, and to slow down the rate of voltage drop when the output voltage of the undervoltage control sub-circuit decreases.

[0019] By adopting the above technical solution, and connecting it to the input and output terminals of the undervoltage control sub-circuit, it plays a buffering role when the voltage changes. When the input voltage of the undervoltage control sub-circuit increases, the undervoltage compensation sub-circuit will slow down the rate of voltage rise; when the output voltage decreases, it will slow down the rate of voltage fall, making the voltage change smoother. This not only avoids the problem of voltage jump at the critical point, but also improves the response speed of the circuit near the undervoltage point.

[0020] In conjunction with some embodiments of the first aspect, in some embodiments, the undervoltage protection circuit further includes a rectifier filter sub-circuit;

[0021] The reference terminal of the undervoltage control sub-circuit is connected to the target area through the rectifier and filter sub-circuit, and the reference terminal of the overvoltage control sub-circuit is also connected to the target area through the rectifier and filter sub-circuit; this is used to rectify and filter the voltage of the target area and then input it to the reference terminals of the undervoltage control sub-circuit and the overvoltage control sub-circuit, respectively.

[0022] By adopting the above technical solution, the rectifier filter sub-circuit is located between the target area and the reference terminals of the undervoltage control sub-circuit and the overvoltage control sub-circuit, ensuring that only positive voltage is transmitted and avoiding potential damage to the circuit caused by negative voltage. Secondly, the filtering function smooths voltage fluctuations and filters out high-frequency noise and transient interference, resulting in a more stable and reliable voltage signal. This provides an accurate reference voltage for the undervoltage and overvoltage control sub-circuits, reducing false triggering and improving detection accuracy.

[0023] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes a voltage regulator sub-circuit;

[0024] The input terminal of the voltage regulator sub-circuit is interconnected with the output terminal and the second pin of the overvoltage protection sub-circuit. This is used to stabilize the voltage received by the second pin to a preset stable voltage when the voltage in the target area is not higher than the preset overvoltage protection voltage.

[0025] By adopting the above technical solution, the output terminals of the voltage regulator sub-circuit and the overvoltage protection sub-circuit are connected to the second pin of the chip. Under normal operating conditions (i.e., when the voltage in the target area does not exceed the preset overvoltage protection voltage), the voltage regulator sub-circuit stabilizes the voltage received by the second pin at the preset stable voltage value. This ensures that the second pin of the chip receives a stable power supply within the normal operating range, improving the chip's efficiency and lifespan.

[0026] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes an overvoltage differential adjustable sub-circuit;

[0027] The detection terminal and input terminal of the overvoltage hysteresis adjustable sub-circuit are interconnected with the output terminal of the overvoltage control sub-circuit, and the output terminal is interconnected with the reference terminal and target area of ​​the overvoltage control sub-circuit. This is used to form a feedback network between the reference terminal and the target area of ​​the overvoltage control sub-circuit when a preset voltage is detected at the detection terminal, so that the voltage obtained by the detection terminal of the overvoltage protection sub-circuit is reduced.

[0028] By adopting the above technical solution, when the overvoltage control subcircuit detects overvoltage and outputs a preset voltage, the overvoltage hysteresis adjustable subcircuit forms a feedback network between the reference terminal and the target area of ​​the overvoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection terminal of the overvoltage protection subcircuit, thereby preventing the protection circuit from frequently switching when the voltage fluctuates repeatedly near the critical point. When the voltage drops from the overvoltage state, it needs to drop to a lower threshold before the protection state can be released. This avoids the frequent switching phenomenon that may occur during the slow voltage drop process.

[0029] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes an overvoltage compensation sub-circuit;

[0030] The input terminal of the overvoltage compensation sub-circuit is interconnected with the reference terminal and target area of ​​the overvoltage control sub-circuit, and the output terminal of the overvoltage compensation sub-circuit is interconnected with the input terminal and output terminal of the overvoltage control sub-circuit. This is used to slow down the rate of voltage rise when the input voltage of the overvoltage control sub-circuit increases, and to slow down the rate of voltage drop when the output voltage of the overvoltage control sub-circuit decreases.

[0031] By adopting the above technical solution, the overvoltage compensation sub-circuit is connected to the input and output terminals of the overvoltage control sub-circuit, and plays a buffering role when the voltage changes. When the input voltage of the overvoltage control sub-circuit increases, the overvoltage compensation sub-circuit will slow down the rate of voltage rise; when the output voltage decreases, it will slow down the rate of voltage fall, making the voltage change smoother. This not only avoids the problem of voltage jump at the critical point, but also improves the response speed of the circuit near the overvoltage point.

[0032] Secondly, this application provides an over / under voltage protection circuit, including: a three-terminal adjustable shunt parallel regulator Q1, a Zener diode D5, a transistor Q2, a three-terminal adjustable shunt parallel regulator Q6, a Zener diode D7, a transistor Q4, and a transistor Q5.

[0033] The reference terminal of the three-terminal adjustable shunt parallel voltage regulator Q1 is connected to the target area, the input terminal is connected to the cathode of the Zener diode D5, and the external high-level signal is connected, while the output terminal is grounded.

[0034] The output terminal of Zener diode D5 is connected to the base of transistor Q2;

[0035] The transmitter stage of transistor Q2 is connected to the first pin, and the collector stage is grounded.

[0036] The reference terminal of the three-terminal adjustable shunt parallel voltage regulator Q6 is connected to the target area, the input terminal is connected to the cathode of the voltage regulator diode D7, and the external high-level signal is connected, while the output terminal is grounded.

[0037] The output terminal of Zener diode D7 is connected to the base of a Darlington transistor consisting of transistors Q4 and Q5;

[0038] The transmitting stage of the Darlington transistor is connected to an external high-level signal, and the collector stage of the Darlington transistor is connected to the second pin.

[0039] Thirdly, this application provides an over / under voltage protection circuit, including: resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, and R19; rectifier diodes D1, D2, D3, D4, and D6; Zener diodes D5, D7, and D8; capacitors C1, C2, C3, C4, C5, C6, and C7; three-terminal adjustable shunt parallel voltage regulators Q1 and Q6; transistors Q2, Q3, Q4, and Q5; and MOSFET Q7.

[0040] The anodes of rectifier diodes D1 and D3 are both connected to the target area. The cathodes of rectifier diodes D1 and D3 are both grounded through capacitor C2 and connected to the anode of rectifier diode D4 through resistors R1, R2, and R3 connected in series.

[0041] The cathode of rectifier diode D4 is interconnected with the first terminal of resistor R7, the first terminal of capacitor C3, and the first terminal of resistor R13;

[0042] The second terminal of resistor R7 is interconnected with the first terminal of resistor R9, the first terminal of resistor R10, the first terminal of capacitor C4, the first terminal of capacitor C1, and the reference terminal of the three-terminal adjustable shunt parallel regulator Q1.

[0043] The input terminal of the three-terminal adjustable shunt parallel voltage regulator Q1, the second terminal of capacitor C1, the first terminal of resistor R4, and the cathode of Zener diode D5 are interconnected, and the output terminal of the three-terminal adjustable shunt parallel voltage regulator Q1 is grounded.

[0044] The second end of resistor R4 is connected to the cathode of rectifier diode D2;

[0045] The anode of rectifier diode D2 is connected to a high-level external circuit.

[0046] The anode of Zener diode D5 is connected to the first terminal of resistor R5;

[0047] The second terminal of resistor R5 is interconnected with the first terminal of resistor R8, the base of transistor Q2, and the base of transistor Q3;

[0048] The emitter of transistor Q2 is connected to the first pin of the chip through resistor R6, and the collector of transistor Q2 is grounded.

[0049] The emitter of transistor Q3 is connected to the second terminal of resistor R10, and the collector of transistor Q3 is grounded.

[0050] The second terminal of resistor R13 is connected to the first terminal of resistor R16, the first terminal of resistor R17, the first terminal of capacitor C5, the first terminal of capacitor C6, and the reference terminal of the three-terminal adjustable shunt parallel regulator Q6.

[0051] The second terminal of resistor R16 and the second terminal of capacitor C6 are grounded;

[0052] The input terminal of the three-terminal adjustable shunt parallel voltage regulator Q6 is interconnected with the second terminal of capacitor C5, the first terminal of resistor R12, and the cathode of Zener diode D7; the output terminal of the three-terminal adjustable shunt parallel voltage regulator Q6 is grounded.

[0053] The second terminal of resistor R12 is connected to the cathode of rectifier diode D6;

[0054] The anode of rectifier diode D6 is connected to a high-level external circuit.

[0055] The anode of Zener diode D7 is connected to the first terminal of resistor R14;

[0056] The second end of resistor R14 is connected to the base of the Darlington transistor composed of transistors Q4 and Q5, and the first end of resistor R15.

[0057] The emitter of the Darlington transistor is connected to a high-level external circuit via resistor R11. The collector of transistor Q4 is interconnected with the first terminal of capacitor C7, the second terminal of resistor R15, the first terminal of resistor R18, the cathode of Zener diode D8, and the second pin of the chip.

[0058] The second terminal of capacitor C7, the anode of Zener diode D8, and the gate of MOSFET Q7 are connected;

[0059] The second terminal of the source connection resistor R17 of MOSFET Q7;

[0060] The second terminal of resistor R18 is grounded through resistor R19; the second terminal of resistor R18 is connected to the drain of MOSFET Q7.

[0061] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0062] 1. The undervoltage control subcircuit and overvoltage control subcircuit monitor the voltage of the target area respectively. When undervoltage or overvoltage is detected, the corresponding protection subcircuit is activated. The undervoltage protection subcircuit achieves protection by connecting the chip's first pin to an external low level, reducing output power or completely shutting down the output. Utilizing the internal logic of the control chip, it achieves accurate undervoltage protection without complex ADC conversion. The overvoltage protection subcircuit achieves protection by disconnecting the second pin from an external high level. By disconnecting the external high-level connection, these pins will return to a low level due to the internal pull-down resistors, thus stopping the chip from working. Since a high-bit ADC is not required, quantization and nonlinearity errors associated with the ADC are eliminated. Furthermore, it directly operates the chip's key control pins instead of through a complex analog-to-digital conversion process. This direct control reduces intermediate steps and the possibility of error accumulation. Therefore, this solution maintains high accuracy while reducing cost, achieving a balance between accuracy and cost.

[0063] 2. When the undervoltage control subcircuit detects undervoltage and outputs a high level, the undervoltage hysteresis adjustable subcircuit will form a feedback network between the reference terminal and the target area of ​​the undervoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection terminal of the undervoltage protection subcircuit, which can prevent the protection circuit from frequently switching when the voltage fluctuates repeatedly near the critical point. Specifically, when the voltage recovers from the undervoltage state, it needs to reach a higher threshold before the protection state can be released. This avoids the frequent switching phenomenon that may occur during the slow voltage recovery process.

[0064] 3. By connecting to the input and output terminals of the undervoltage control sub-circuit, it acts as a buffer when the voltage changes. When the input voltage of the undervoltage control sub-circuit increases, the undervoltage compensation sub-circuit slows down the rate of voltage rise; when the output voltage decreases, it slows down the rate of voltage fall, making the voltage change smoother. This not only avoids the problem of voltage jumps at the critical point, but also improves the circuit's response speed near the undervoltage point. Attached Figure Description

[0065] Figure 1 This is a circuit diagram of an over / under voltage protection circuit in an embodiment of this application;

[0066] Figure 2 This is another circuit diagram of the over / under voltage protection circuit in the embodiments of this application; Detailed Implementation

[0067] The terminology used in the following embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. As used in the specification and appended claims of this application, the singular expressions “a,” “the,” “the,” “the,” “the,” and “this” are intended to include the plural expressions as well, unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this application refers to and includes any or all possible combinations of one or more of the listed items.

[0068] Hereinafter, the terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature, and in the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0069] refer to Figure 1 , Figure 1 This is a circuit diagram of an over / under voltage protection circuit in an embodiment of this application;

[0070] In a first aspect, this application provides an over / under voltage protection circuit, including: an undervoltage protection circuit and an overvoltage protection circuit;

[0071] This circuit integrates both undervoltage and overvoltage protection mechanisms, achieving bidirectional protection against voltage anomalies. The undervoltage protection circuit monitors and responds to situations where the voltage is too low, preventing the chip from malfunctioning or being damaged due to insufficient voltage. The overvoltage protection circuit monitors and responds to situations where the voltage is too high, avoiding damage to the chip from excessive voltage.

[0072] The undervoltage protection circuit includes an undervoltage control sub-circuit and an undervoltage protection sub-circuit;

[0073] The reference terminal of the undervoltage control sub-circuit is connected to the target area, the input terminal is connected to an external high-level voltage, and the output terminal is connected to the detection terminal of the undervoltage protection sub-circuit. It is used to obtain the voltage of the target area, and when the voltage of the target area is lower than the preset undervoltage protection voltage, it introduces an external high-level voltage from the input terminal and outputs it from the output terminal.

[0074] The target area is the monitoring point of the circuit that needs to be protected.

[0075] The undervoltage control sub-circuit collects the voltage of the target area in real time through its reference terminal. It compares this voltage with the internally set preset undervoltage protection voltage. When the voltage of the target area is detected to be lower than the preset undervoltage protection voltage, the undervoltage control sub-circuit will activate its internal switch or logic circuit to introduce an external high-level signal from the input terminal.

[0076] In some specific embodiments, the inverting input of the operational amplifier is connected to a reference voltage source as a preset undervoltage protection voltage; the non-inverting input is connected to the target area for real-time voltage acquisition; the output of the operational amplifier is connected to the base or gate of a transistor or MOSFET; the collector or drain of the transistor or MOSFET is connected to an external high-level voltage, and the emitter or source is used as the output; when the voltage in the target area is lower than a preset value, the operational amplifier outputs a high level, turning on the transistor or MOSFET and transmitting a high-level signal to the output.

[0077] In other specific embodiments, a three-terminal adjustable shunt parallel regulator, such as the TL431, is selected; the cathode K terminal of the regulator is connected to the positive terminal of the power supply through a current-limiting resistor, and the anode A terminal of the regulator is connected to a low potential (e.g., ground); the reference terminal R terminal of the regulator is connected to the target area for real-time voltage acquisition; a simple voltage divider circuit is designed to reduce the voltage in the target area to a range acceptable to the regulator (typically 0-2.5V); a pull-up resistor is added to the K terminal to provide a high-level output in the high-impedance state. The circuit works as follows: When the voltage at the reference terminal R is greater than 2.5V (i.e., the voltage in the target region is normal), the internal operational amplifier of the regulator outputs a low level, making the base voltage of the internal transistor high. At this time, the collector junction and emitter junction of the internal transistor are conducting, which is equivalent to the cathode terminal K and the anode terminal A being conducting. The voltage at terminal K is lower than 2.5V, resulting in a low-level output. When the voltage at the reference terminal R is less than 2.5V (i.e., undervoltage occurs), the internal operational amplifier of the regulator outputs a high level, making the base voltage of the internal transistor low. At this time, the collector junction and emitter junction of the internal transistor are reverse biased, and the transistor is cut off. Simultaneously, the internal diode connected in parallel is also in a cut-off state. Under these circumstances, the voltage between terminal K and terminal A is equal to the power supply voltage, and terminal K exhibits a high impedance state. A high-level output is obtained through the pull-up resistor, indicating that an undervoltage condition has occurred.

[0078] This three-terminal adjustable shunt parallel regulator can output a clear high or low level signal at terminal K under different conditions; it has high stability, the difference in output level is obvious, the value is very stable, it is not affected by external factors, and there is almost no fluctuation.

[0079] The input terminal of the undervoltage protection sub-circuit is connected to the first pin of the chip, and the output terminal is connected to an external low level. It is used to connect the first pin to an external low level when the detection terminal detects an external high level. The level of the first pin needs to be greater than the external low level.

[0080] When the undervoltage control subcircuit detects that the voltage in the target area is lower than the preset undervoltage protection voltage, it will output a high-level signal at its output terminal (i.e., the detection terminal of the undervoltage protection subcircuit). After receiving this high-level signal, the undervoltage protection subcircuit will immediately change its internal state, switching the input terminal originally connected to the first pin of the chip to the output terminal connected to the external low level. This switching will quickly reduce the voltage applied to the first pin of the chip, making it close to but slightly higher than the external low level. This slightly higher voltage difference is caused by the voltage drop of the internal components of the undervoltage protection subcircuit, which ensures that the chip can still maintain a minimum working capacity or standby state when protected.

[0081] The overvoltage protection circuit includes an overvoltage control sub-circuit and an overvoltage protection sub-circuit;

[0082] The reference terminal of the overvoltage control sub-circuit is connected to the target area, the input terminal is connected to an external high level, and the output terminal is connected to the detection terminal of the overvoltage protection sub-circuit. This is used to obtain the voltage of the target area, and when the voltage of the target area is higher than the preset overvoltage protection voltage, the output terminal switches from outputting an external high level to outputting the preset control voltage.

[0083] It should be noted that the principle and steps of the overvoltage control sub-circuit are the same as those of the undervoltage control sub-circuit. The relevant principles and steps can be referred to, but the specific settings are different. The preset overvoltage protection voltage should be higher than the preset undervoltage protection voltage, which will not be elaborated here.

[0084] The input of the overvoltage protection sub-circuit is connected to an external high-level voltage, and the output is connected to the second pin of the chip. It is used to disconnect the connection between the second pin and the external high-level voltage when the preset control voltage is detected at the detection end. The voltage level of the second pin needs to be greater than that of the first pin.

[0085] It should be noted that the principle and steps of the overvoltage protection sub-circuit are the same as those of the undervoltage protection sub-circuit, and the relevant principles and steps can be referred to.

[0086] The first pin is the chip's dimming pin, enable pin, COMP compensation pin, and other pins with high and low levels; the first pin is the control chip's PWM pin, enable pin, COMP compensation pin, and other pins with high and low levels.

[0087] It should be explained that the second pin is usually designed to be active high. When these pins are high, the chip works normally; when they are low, the chip stops working. The chip usually has pull-down resistors inside to ensure that these pins are in a low-level state by default when there is no external signal input, thus putting the chip in a safe non-working state.

[0088] As can be seen, the undervoltage control subcircuit and the overvoltage control subcircuit monitor the voltage of the target area respectively. When undervoltage or overvoltage is detected, the corresponding protection subcircuit is activated. The undervoltage protection subcircuit achieves protection by connecting the chip's first pin to an external low level, reducing output power or completely shutting down the output. It utilizes the internal logic of the control chip to achieve accurate undervoltage protection without complex ADC conversion. The overvoltage protection subcircuit achieves protection by disconnecting the second pin from an external high level. By disconnecting the external high-level connection, these pins will return to a low level due to the internal pull-down resistor, thus stopping the chip from working. Since a high-bit ADC is not required, quantization and nonlinearity errors associated with the ADC are eliminated. At the same time, it directly operates the chip's key control pins instead of through a complex analog-to-digital conversion process. This direct control reduces intermediate links and the possibility of error accumulation. Therefore, this scheme maintains high accuracy while reducing costs, achieving a balance between accuracy and cost.

[0089] In some embodiments, the undervoltage protection circuit further includes an undervoltage differential adjustable sub-circuit;

[0090] The detection terminal of the undervoltage hysteresis adjustable sub-circuit is connected to the output terminal of the undervoltage control sub-circuit, and the input terminal is interconnected with the reference terminal and the target area of ​​the undervoltage control sub-circuit. It is used to form a feedback network between the reference terminal and the target area of ​​the undervoltage control sub-circuit when the detection terminal detects an external high level, so that the voltage obtained by the detection terminal of the undervoltage protection sub-circuit is reduced.

[0091] When the undervoltage control subcircuit detects undervoltage and outputs a high-level signal, the undervoltage hysteresis adjustable subcircuit is activated. It forms a feedback network between the reference terminal of the undervoltage control subcircuit and the target region. This feedback network reduces the voltage value sensed by the undervoltage control subcircuit. The purpose of this is to ensure that even if the actual voltage rises slightly, the undervoltage protection will not be immediately triggered. Undervoltage protection will only be released when the actual voltage increases significantly, exceeding the set hysteresis value.

[0092] In some specific embodiments, an operational amplifier with low bias current is selected; the non-inverting input of the operational amplifier is connected to the target region; the inverting input of the operational amplifier is connected to the reference terminal of the undervoltage control subcircuit through a resistor; a feedback resistor is connected between the output terminal and the inverting input terminal of the operational amplifier; a small resistor controlled by a MOSFET switch is connected in parallel with the feedback resistor; the gate of the MOSFET is connected to the output terminal of the undervoltage control subcircuit, and when undervoltage is detected, the MOSFET turns on, changing the gain of the feedback network, thereby reducing the voltage sensed by the undervoltage control subcircuit.

[0093] In some embodiments, a suitable NPN transistor and several resistors R are selected; a resistor A is connected between the target region and the reference terminal of the undervoltage control subcircuit; a series circuit is connected in parallel across resistor A, consisting of the collector-emitter channel of the transistor and another resistor B connected in series; the base of the transistor is connected to the output terminal of the undervoltage control subcircuit through a current-limiting resistor; the values ​​of resistors A and B are selected according to the required hysteresis value. When undervoltage is detected, the transistor conducts, causing resistor B to be connected in parallel with resistor A, forming a voltage divider network, thereby reducing the voltage sensed by the undervoltage control subcircuit and achieving hysteresis regulation.

[0094] As can be seen, when the undervoltage control subcircuit detects undervoltage and outputs a high level, the undervoltage hysteresis adjustable subcircuit will form a feedback network between the reference terminal and the target area of ​​the undervoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection terminal of the undervoltage protection subcircuit, which can prevent the protection circuit from frequently switching when the voltage fluctuates repeatedly near the critical point. Specifically, when the voltage recovers from the undervoltage state, it needs to reach a relatively high threshold before the protection state can be released. This avoids the frequent switching phenomenon that may occur during the slow voltage recovery process.

[0095] In some embodiments, the undervoltage protection circuit further includes an undervoltage compensation sub-circuit;

[0096] The input terminal of the undervoltage compensation sub-circuit is interconnected with the reference terminal and target area of ​​the undervoltage control sub-circuit, and the output terminal of the undervoltage compensation sub-circuit is interconnected with the input terminal and output terminal of the undervoltage control sub-circuit. This is used to slow down the rate of voltage rise when the input voltage of the undervoltage control sub-circuit increases, and to slow down the rate of voltage drop when the output voltage of the undervoltage control sub-circuit decreases.

[0097] When the voltage in the target area begins to rise, the undervoltage compensation sub-circuit affects the input of the undervoltage control sub-circuit through its output, slowing down the rate of voltage rise at the input. This delay prevents false triggering of the undervoltage protection due to momentary voltage fluctuations. Similarly, when the output voltage of the undervoltage control sub-circuit begins to fall, the undervoltage compensation sub-circuit also slows down the rate of voltage drop at its output, preventing immediate triggering of undervoltage protection due to temporary small voltage drops, thereby improving stability and anti-interference capability. The presence of the undervoltage compensation sub-circuit gives the undervoltage protection circuit a certain degree of "inertia," allowing it to better adapt to voltage fluctuations in the actual working environment and reducing the occurrence of malfunctions.

[0098] In some specific embodiments, an operational amplifier with high input impedance is selected; the operational amplifier is configured as a voltage follower with its non-inverting input connected to the target region; an RC low-pass filter network is connected between the output of the operational amplifier and the input of the undervoltage control sub-circuit; resistor and capacitor values ​​are selected so that the time constant of the RC network can effectively smooth voltage fluctuations; a Zener diode is connected in parallel at the output of the RC network to limit the voltage variation range. This effectively mitigates rapid voltage changes and provides a more stable reference signal for undervoltage control.

[0099] In some specific embodiments, a capacitor of suitable capacitance is selected, with one end connected to the input of the undervoltage control subcircuit and the other end grounded. A small resistor is connected in series between the capacitor and the target area to limit the charging and discharging current. A diode is connected between the junction of the resistor and capacitor and the output of the undervoltage control subcircuit, with the anode of the diode facing the capacitor. The capacitance is adjusted as required to obtain the desired voltage change response characteristics. A large-value discharge resistor is connected in parallel across the capacitor to slowly release the charge on the capacitor. This simple design utilizes the charging and discharging characteristics of the capacitor to naturally slow down the rate of voltage change, providing basic undervoltage compensation functionality.

[0100] As can be seen, by connecting to the input and output terminals of the undervoltage control sub-circuit, it plays a buffering role when the voltage changes. When the input voltage of the undervoltage control sub-circuit increases, the undervoltage compensation sub-circuit slows down the rate of voltage rise; when the output voltage decreases, it slows down the rate of voltage fall, making the voltage change smoother. This not only avoids the voltage jump problem at the critical point, but also improves the response speed of the circuit near the undervoltage point.

[0101] In some embodiments, the undervoltage protection circuit further includes a rectifier filter sub-circuit;

[0102] The reference terminal of the undervoltage control sub-circuit is connected to the target area through the rectifier and filter sub-circuit, and the reference terminal of the overvoltage control sub-circuit is also connected to the target area through the rectifier and filter sub-circuit; this is used to rectify and filter the voltage of the target area and then input it to the reference terminals of the undervoltage control sub-circuit and the overvoltage control sub-circuit, respectively.

[0103] The rectifier-filter sub-circuit first receives a voltage signal from the target area that may contain AC components or noise. Through a rectifier circuit, such as a diode bridge rectifier, the AC voltage is converted into a unidirectional pulsating DC voltage. Subsequently, a filter circuit (typically including capacitors and inductors) smooths these pulsations, reducing the ripple component in the voltage. The voltage signal after rectification and filtering becomes more stable and smooth, which helps improve the operating accuracy and reliability of the undervoltage control and overvoltage control sub-circuits. The output of the rectifier-filter sub-circuit is connected to the reference terminals of the undervoltage control and overvoltage control sub-circuits, respectively, providing these two sub-circuits with processed and reliable voltage reference signals. This effectively reduces the impact of power supply fluctuations and electromagnetic interference on the voltage protection function, improving the overall anti-interference capability and operational stability.

[0104] In some specific embodiments, four rectifier diodes of the same specification are selected to form a full-wave bridge rectifier circuit; the AC input terminal of the bridge rectifier circuit is connected to the target area; a large-capacity electrolytic capacitor is connected in parallel at the DC output terminal of the bridge rectifier circuit for preliminary filtering; an inductor is connected in series after the electrolytic capacitor to form an LC filter circuit; a small-capacity ceramic capacitor is connected in parallel at the output terminal of the LC filter circuit to filter out high-frequency noise; the filtered output is connected to the reference terminals of the undervoltage control subcircuit and the overvoltage control subcircuit, respectively.

[0105] In some specific embodiments, a fast recovery rectifier diode is selected, with its positive terminal connected to the target area and its negative terminal serving as the output terminal. A large-capacity electrolytic capacitor is connected in parallel with the output terminal of the diode for primary filtering. When selecting the capacitance value of the electrolytic capacitor, the load current and allowable ripple voltage are considered to ensure sufficient filtering effect. A small-capacity ceramic capacitor is connected in parallel across the electrolytic capacitor to filter out high-frequency noise. If necessary, a medium-capacity tantalum capacitor can be added between the electrolytic capacitor and the ceramic capacitor to further improve the filtering effect. The filtered output terminal is connected to the reference terminals of the undervoltage control subcircuit and the overvoltage control subcircuit, respectively.

[0106] As can be seen, the rectifier-filter sub-circuit is located between the target area and the reference terminals of the undervoltage control sub-circuit and the overvoltage control sub-circuit, ensuring that only positive voltage is transmitted and avoiding potential damage to the circuit caused by negative voltage. Secondly, the filtering function smooths voltage fluctuations and filters out high-frequency noise and transient interference, resulting in a more stable and reliable voltage signal. This provides an accurate reference voltage for the undervoltage and overvoltage control sub-circuits, reducing false triggering and improving detection accuracy.

[0107] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes a voltage regulator sub-circuit;

[0108] The input terminal of the voltage regulator sub-circuit is interconnected with the output terminal and the second pin of the overvoltage protection sub-circuit. This is used to stabilize the voltage received by the second pin to a preset stable voltage when the voltage in the target area is not higher than the preset overvoltage protection voltage.

[0109] As can be seen, the output terminals of the voltage regulator sub-circuit and the overvoltage protection sub-circuit are connected to the second pin of the chip. Under normal operating conditions (i.e., when the voltage in the target area does not exceed the preset overvoltage protection voltage), the voltage regulator sub-circuit stabilizes the voltage received by the second pin at the preset stable voltage value. This ensures that the second pin of the chip receives a stable power supply within the normal operating range, improving the chip's efficiency and lifespan.

[0110] In some embodiments, the overvoltage protection circuit further includes an overvoltage differential adjustable sub-circuit;

[0111] The detection terminal and input terminal of the overvoltage hysteresis adjustable sub-circuit are interconnected with the output terminal of the overvoltage control sub-circuit, and the output terminal is interconnected with the reference terminal and target area of ​​the overvoltage control sub-circuit. This is used to form a feedback network between the reference terminal and the target area of ​​the overvoltage control sub-circuit when a preset voltage is detected at the detection terminal, so that the voltage obtained by the detection terminal of the overvoltage protection sub-circuit is reduced.

[0112] It should be noted that the overvoltage hysteresis adjustable circuit is similar to the undervoltage hysteresis adjustable circuit, and the relevant principles and steps are the same. The relevant principles and steps can be referred to, and will not be repeated here.

[0113] As can be seen, when the overvoltage control subcircuit detects overvoltage and outputs a preset voltage, the overvoltage hysteresis adjustable subcircuit forms a feedback network between the reference terminal and the target region of the overvoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection terminal of the overvoltage protection subcircuit, thereby preventing the protection circuit from frequently switching when the voltage fluctuates repeatedly near the critical point. When the voltage drops from the overvoltage state, it needs to drop to a lower threshold before the protection state can be released. This avoids the frequent switching phenomenon that may occur during the slow voltage drop process.

[0114] In some embodiments, the overvoltage protection circuit further includes an overvoltage compensation sub-circuit;

[0115] The input terminal of the overvoltage compensation sub-circuit is interconnected with the reference terminal and target area of ​​the overvoltage control sub-circuit, and the output terminal of the overvoltage compensation sub-circuit is interconnected with the input terminal and output terminal of the overvoltage control sub-circuit. This is used to slow down the rate of voltage rise when the input voltage of the overvoltage control sub-circuit increases, and to slow down the rate of voltage drop when the output voltage of the overvoltage control sub-circuit decreases.

[0116] It should be noted that the overvoltage protection circuit is similar to the undervoltage protection circuit, and the relevant principles and steps are the same. The relevant principles and steps can be referred to, and will not be repeated here.

[0117] By adopting the above technical solution, the overvoltage compensation sub-circuit is connected to the input and output terminals of the overvoltage control sub-circuit, and plays a buffering role when the voltage changes. When the input voltage of the overvoltage control sub-circuit increases, the overvoltage compensation sub-circuit will slow down the rate of voltage rise; when the output voltage decreases, it will slow down the rate of voltage fall, making the voltage change smoother. This not only avoids the problem of voltage jump at the critical point, but also improves the response speed of the circuit near the overvoltage point.

[0118] refer to Figure 2 , Figure 2 This is another circuit diagram of the over / under voltage protection circuit in the embodiments of this application;

[0119] Secondly, this application provides an over / under voltage protection circuit, including: a three-terminal adjustable shunt parallel regulator Q1, a Zener diode D5, a transistor Q2, a three-terminal adjustable shunt parallel regulator Q6, a Zener diode D7, a transistor Q4, and a transistor Q5.

[0120] The reference terminal of the three-terminal adjustable shunt parallel voltage regulator Q1 is connected to the target area, the input terminal is connected to the cathode of the Zener diode D5, and the external high-level signal is connected, while the output terminal is grounded.

[0121] Under normal operating conditions, when the voltage in the target area is not less than the preset undervoltage protection voltage of the three-terminal adjustable shunt parallel regulator Q1, the input and output terminals of the three-terminal adjustable shunt parallel regulator Q1 are internally connected. This configuration pulls the input voltage down to a preset low level, which is less than the internal breakdown voltage of the Zener diode D5. At this time, the Zener diode D5 remains in the reverse cutoff state.

[0122] When an undervoltage condition occurs, i.e., the voltage in the target area drops below the preset undervoltage protection voltage of the three-terminal adjustable shunt parallel regulator Q1, the internal switch of the three-terminal adjustable shunt parallel regulator Q1 activates, disconnecting the input and output terminals. This causes the input voltage to rise to a high external level. This high voltage exceeds the breakdown voltage of the Zener diode D5, causing Zener diode D5 to enter a reverse breakdown state.

[0123] The output terminal of Zener diode D5 is connected to the base of transistor Q2;

[0124] Under normal operating conditions: Zener diode D5 is in reverse cutoff. In this state, the cathode voltage of Zener diode D5 is lower than its breakdown voltage, therefore Zener diode D5 does not conduct. Because Zener diode D5 is not conducting, its output (anode) voltage is very low, close to zero. This results in insufficient voltage driving the base of transistor Q2, therefore transistor Q2 is in cutoff and does not conduct.

[0125] Under under voltage conditions: Zener diode D5 enters reverse breakdown state. In this state, Zener diode D5 begins to conduct.

[0126] The transmitter stage of transistor Q2 is connected to the first pin, and the collector stage is grounded.

[0127] Transistor Q2 is configured as a switching circuit. Under normal operating conditions, transistor Q2 is in the off state, with a high impedance between its emitter and collector, and pin 1 remains high. In the event of an undervoltage condition, the base of transistor Q2 is driven by Zener diode D5, turning Q2 on. Once on, the emitter voltage of transistor Q2 approaches its grounded collector voltage, effectively pulling pin 1 low to near ground potential.

[0128] The reference terminal of the three-terminal adjustable shunt parallel voltage regulator Q6 is connected to the target area, the input terminal is connected to the cathode of the voltage regulator diode D7, and the external high-level signal is connected, while the output terminal is grounded.

[0129] Under normal operating conditions, the voltage in the target area is lower than the preset overvoltage protection voltage of the three-terminal adjustable shunt parallel regulator Q6, and the internal switch of the three-terminal adjustable shunt parallel regulator Q6 is in the open state. At this time, a high impedance is presented between its input and output terminals, and the input terminal remains in a high-level state connected to the external high level. This high-level voltage is lower than the breakdown voltage of the Zener diode D7, keeping the Zener diode D7 in the reverse cutoff state. Under overvoltage conditions, the internal switch of the three-terminal adjustable shunt parallel regulator Q6 closes, connecting the input and output terminals, causing the input voltage to drop rapidly to a low level close to ground potential, triggering the subsequent overvoltage protection mechanism.

[0130] The output terminal of Zener diode D7 is connected to the base of a Darlington transistor consisting of transistors Q4 and Q5;

[0131] Under normal operating conditions, Zener diode D7 is in the ON state, maintaining its breakdown voltage to provide a stable drive voltage to the base of the Darlington transistor (composed of transistors Q4 and Q5). This stable voltage ensures that the Darlington transistor is in the ON state, allowing current to flow from the emitter to the collector, maintaining the power supply to the second pin.

[0132] When an overvoltage condition occurs, the three-terminal adjustable shunt parallel voltage regulator Q6 turns on, and its input voltage drops rapidly. This causes the voltage difference across Zener diode D7 to fall below its breakdown voltage, causing Zener diode D7 to enter reverse cutoff mode. After Zener diode D7 is cut off, its output (anode) voltage drops rapidly, cutting off the driving voltage to the base of the Darlington transistor.

[0133] The transmitting stage of the Darlington transistor is connected to an external high-level signal, and the collector stage of the Darlington transistor is connected to the second pin.

[0134] Under normal operating conditions: The Darlington transistor is in the on state, allowing a high level from the outside to pass through the collector-emitter channel of the Darlington transistor, providing a stable power supply for the subsequent circuit connected to the second pin.

[0135] Under overvoltage conditions, the Darlington transistor switches from the on state to the off state, cutting off the connection between the second pin and the external high level, and quickly interrupting the power supply to subsequent circuits.

[0136] refer to Figure 2 , Figure 2 This is another circuit diagram of the over / under voltage protection circuit in the embodiments of this application;

[0137] Thirdly, this application provides an over / under voltage protection circuit, including: resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, R15, R16, R17, R18, and R19; rectifier diodes D1, D2, D3, D4, and D6; Zener diodes D5, D7, and D8; capacitors C1, C2, C3, C4, C5, C6, and C7; three-terminal adjustable shunt parallel voltage regulators Q1 and Q6; transistors Q2, Q3, Q4, and Q5; and MOSFET Q7.

[0138] The anodes of rectifier diodes D1 and D3 are both connected to the target area. The cathodes of rectifier diodes D1 and D3 are both grounded through capacitor C2 and connected to the anode of rectifier diode D4 through resistors R1, R2, and R3 connected in series.

[0139] The parallel configuration of rectifier diodes D1 and D3 provides bidirectional reverse voltage protection. Regardless of the polarity of the input voltage, one of the diodes will always block the reverse current, effectively preventing circuit damage. The grounded capacitor C2 forms a low-pass filter, which can effectively filter out high-frequency noise and transient interference. The series connection of resistors R1, R2, and R3 not only serves as a current limiter but also forms a voltage divider network.

[0140] The cathode of rectifier diode D4 is interconnected with the first terminal of resistor R7, the first terminal of capacitor C3, and the first terminal of resistor R13;

[0141] The cathode of rectifier diode D4 provides a stable positive voltage source, which is simultaneously distributed to the undervoltage protection circuit (through R7) and the overvoltage protection circuit (through R13). Capacitor C3 provides decoupling and filtering functions at this node. R7 controls the current of the undervoltage protection circuit, and R13 controls the current of the overvoltage protection circuit.

[0142] The second terminal of resistor R7 is interconnected with the first terminal of resistor R9, the first terminal of resistor R10, the first terminal of capacitor C4, the first terminal of capacitor C1, and the reference terminal of the three-terminal adjustable shunt parallel regulator Q1.

[0143] Resistors R9 and R10 are connected in parallel to form a voltage divider network; capacitor C4 provides crucial filtering; capacitor C1 performs dynamic compensation.

[0144] The input terminal of the three-terminal adjustable shunt parallel voltage regulator Q1, the second terminal of capacitor C1, the first terminal of resistor R4, and the cathode of Zener diode D5 are interconnected, and the output terminal of the three-terminal adjustable shunt parallel voltage regulator Q1 is grounded.

[0145] Resistor R4 is used to limit the current from a high external voltage level;

[0146] The second end of resistor R4 is connected to the cathode of rectifier diode D2;

[0147] The main function of rectifier diode D2 is to prevent reverse voltage;

[0148] The anode of rectifier diode D2 is connected to a high-level external circuit.

[0149] The anode of Zener diode D5 is connected to the first terminal of resistor R5;

[0150] Resistor R5 is used to stabilize the output voltage of Zener diode D5;

[0151] The second terminal of resistor R5 is interconnected with the first terminal of resistor R8, the base of transistor Q2, and the base of transistor Q3;

[0152] The main function of resistor R8 is to provide a safe discharge path for transistor Q2, while preventing the voltage from transistor Q3 from directly affecting the operating state of transistor Q2, and preventing the voltage signal passing through resistors R9, R10 and transistor Q3 from directly entering the base of transistor Q2.

[0153] The emitter of transistor Q2 is connected to the first pin of the chip through resistor R6, and the collector of transistor Q2 is grounded.

[0154] Resistor R6 controls and limits the current flowing to the first pin;

[0155] The emitter of transistor Q3 is connected to the second terminal of resistor R10, and the collector of transistor Q3 is grounded.

[0156] When the cathode of the three-terminal adjustable shunt parallel regulator Q1 outputs a high potential, the transistor Q3 is turned on. Resistors R10 and R9 are directly connected in parallel, allowing for flexible adjustment of current distribution and voltage division. Transistor Q3 and resistor R10 form a feedback network, further reducing the voltage at the reference pin of the three-terminal adjustable shunt parallel regulator Q1 when the cathode outputs a high potential. This mechanism ensures that the cathode of the three-terminal adjustable shunt parallel regulator Q1 can continuously output a high potential, achieving adjustable hysteresis. By adjusting the values ​​of resistors R10 and R9, the hysteresis can be precisely controlled to adapt to different application requirements.

[0157] The second terminal of resistor R13 is connected to the first terminal of resistor R16, the first terminal of resistor R17, the first terminal of capacitor C5, the first terminal of capacitor C6, and the reference terminal of the three-terminal adjustable shunt parallel regulator Q6.

[0158] Resistors R16 and R17 are connected in parallel to form a feedback network. Capacitor C6 acts as a filter in the circuit, and capacitor C5 is specifically used to implement the hysteresis function for overvoltage protection.

[0159] The second terminal of resistor R16 and the second terminal of capacitor C6 are grounded;

[0160] The input terminal of the three-terminal adjustable shunt parallel voltage regulator Q6 is interconnected with the second terminal of capacitor C5, the first terminal of resistor R12, and the cathode of Zener diode D7; the output terminal of the three-terminal adjustable shunt parallel voltage regulator Q6 is grounded.

[0161] Resistor R12 is used for current limiting or voltage setting of the cathode of the three-terminal adjustable shunt parallel voltage regulator Q6;

[0162] The second terminal of resistor R12 is connected to the cathode of rectifier diode D6;

[0163] The rectifier diode D6 is used to protect the circuit from the reverse current of a high external level.

[0164] The anode of rectifier diode D6 is connected to a high-level external circuit.

[0165] The anode of Zener diode D7 is connected to the first terminal of resistor R14;

[0166] Resistor R14 is used to stabilize the voltage at the anode of Zener diode D7.

[0167] The second end of resistor R14 is connected to the base of the Darlington transistor composed of transistors Q4 and Q5, and the first end of resistor R15.

[0168] The emitter of the Darlington transistor is connected to a high-level external circuit via resistor R11. The collector of transistor Q4 is interconnected with the first terminal of capacitor C7, the second terminal of resistor R15, the first terminal of resistor R18, the cathode of Zener diode D8, and the second pin of the chip.

[0169] Resistor R11 is used to control the current of the second pin.

[0170] The second terminal of capacitor C7, the anode of Zener diode D8, and the gate of MOSFET Q7 are connected;

[0171] Capacitor C7 and Zener diode D8 together form a clamping circuit. Together with Zener diode D8, it clamps the voltage received at the second pin to a preset stable voltage value, ensuring that the voltage will not exceed the preset stable voltage value.

[0172] The second terminal of the source connection resistor R17 of MOSFET Q7;

[0173] The second terminal of resistor R18 is grounded through resistor R19; the second terminal of resistor R18 is connected to the drain of MOSFET Q7.

[0174] Resistor R18 controls the current entering the gate of MOSFET Q7, and resistor R19 is connected between the source of MOSFET Q7 and ground to pull down or set the threshold voltage of Q7.

Claims

1. An over / under voltage protection circuit, characterized in that, include: Undervoltage protection circuit and overvoltage protection circuit; The undervoltage protection circuit includes an undervoltage control sub-circuit and an undervoltage protection sub-circuit; The reference terminal of the undervoltage control sub-circuit is connected to the target area, the input terminal is connected to an external high level, and the output terminal is connected to the detection terminal of the undervoltage protection sub-circuit; it is used to obtain the voltage of the target area, and when the voltage of the target area is lower than the preset undervoltage protection voltage, it introduces an external high level from the input terminal and outputs it from the output terminal. The input terminal of the undervoltage protection sub-circuit is connected to the first pin of the chip, and the output terminal is connected to an external low level. It is used to connect the first pin to an external low level when the detection terminal detects an external high level. The level of the first pin needs to be greater than the external low level. The overvoltage protection circuit includes an overvoltage control sub-circuit and an overvoltage protection sub-circuit; The reference terminal of the overvoltage control sub-circuit is connected to the target area, the input terminal is connected to an external high level, and the output terminal is connected to the detection terminal of the overvoltage protection sub-circuit. It is used to obtain the voltage of the target area, and when the voltage of the target area is higher than the preset overvoltage protection voltage, the output terminal switches from outputting an external high level to outputting a preset control voltage. The input terminal of the overvoltage protection sub-circuit is connected to an external high-level voltage, and the output terminal is connected to the second pin of the chip. It is used to disconnect the connection between the second pin and the external high-level voltage when a preset control voltage is detected at the detection terminal. The voltage level of the second pin is required to be greater than that of the first pin and less than that of the external high-level voltage. A pull-down resistor is provided inside the second pin.

2. The circuit according to claim 1, characterized in that, The undervoltage protection circuit also includes an undervoltage differential adjustable sub-circuit; The detection terminal of the undervoltage hysteresis adjustable sub-circuit is connected to the output terminal of the undervoltage control sub-circuit, and the input terminal is interconnected with the reference terminal of the undervoltage control sub-circuit and the target region. When a high external level is detected at the detection terminal, a feedback network is formed between the reference terminal of the undervoltage control sub-circuit and the target area, thereby reducing the voltage obtained at the detection terminal of the undervoltage protection sub-circuit.

3. The circuit according to claim 1, characterized in that, The undervoltage protection circuit also includes an undervoltage compensation sub-circuit; The input terminal of the undervoltage compensation sub-circuit is interconnected with the reference terminal of the undervoltage control sub-circuit and the target region. The output terminal of the undervoltage compensation sub-circuit is interconnected with the input terminal and the output terminal of the undervoltage control sub-circuit. It is used to slow down the voltage rise rate when the input terminal voltage of the undervoltage control sub-circuit increases, and to slow down the voltage fall rate when the output terminal voltage of the undervoltage control sub-circuit decreases.

4. The circuit according to claim 1, characterized in that, The undervoltage protection circuit also includes a rectifier filter sub-circuit; The reference terminal of the undervoltage control sub-circuit is connected to the target area through the rectifier and filter sub-circuit, and the reference terminal of the overvoltage control sub-circuit is connected to the target area through the rectifier and filter sub-circuit. The voltage of the target area is rectified and filtered, and then input to the reference terminals of the undervoltage control sub-circuit and the overvoltage control sub-circuit, respectively.

5. The circuit according to claim 1, characterized in that, The overvoltage protection circuit also includes a voltage regulator circuit; The input terminal of the voltage regulator sub-circuit is interconnected with the output terminal of the overvoltage protection sub-circuit and the second pin, and is used to stabilize the voltage received by the second pin to a preset stable voltage when the voltage in the target area is not higher than the preset overvoltage protection voltage.

6. The circuit according to claim 1, characterized in that, The overvoltage protection circuit also includes an overvoltage hysteresis adjustable sub-circuit; The detection terminal and input terminal of the overvoltage hysteresis adjustable sub-circuit are interconnected with the output terminal of the overvoltage control sub-circuit, and the output terminal is interconnected with the reference terminal of the overvoltage control sub-circuit and the target area. When a preset voltage is detected at the detection terminal, the reference terminal of the overvoltage control sub-circuit forms a feedback network with the target area, thereby reducing the voltage obtained at the detection terminal of the overvoltage protection sub-circuit.

7. The circuit according to claim 1, characterized in that, The overvoltage protection circuit also includes an overvoltage compensation sub-circuit; The input terminal of the overvoltage compensation sub-circuit is interconnected with the reference terminal of the overvoltage control sub-circuit and the target region. The output terminal of the overvoltage compensation sub-circuit is interconnected with the input terminal and the output terminal of the overvoltage control sub-circuit. It is used to slow down the rate of voltage rise when the input terminal voltage of the overvoltage control sub-circuit increases, and to slow down the rate of voltage drop when the output terminal voltage of the overvoltage control sub-circuit decreases.

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