Over-voltage and under-voltage protection circuit

Abstract

The invention provides an overvoltage and undervoltage protection circuit, and relates to the technical field of overvoltage and undervoltage protection. The under-voltage control sub-circuit and the overvoltage control sub-circuit respectively monitor the voltage of a target area, when an under-voltage or overvoltage condition is detected, the corresponding protection sub-circuit is activated, and the under-voltage protection sub-circuit realizes protection by connecting a first pin of a chip to an external low level, so that the output power is reduced or the output is completely closed; according to the overvoltage protection circuit, the internal logic of a control chip is utilized, accurate under-voltage protection can be achieved without complex ADC conversion, the overvoltage protection sub-circuit achieves protection by cutting off connection between a second pin and an external high level, the pins return to a low level state due to the action of an internal pull-down resistor by cutting off connection between the external high level, and the overvoltage protection sub-circuit achieves overvoltage protection by cutting off the external high level connection. As a high-digit ADC (Analog to Digital Converter) does not need to be used, quantization errors and nonlinear errors related to the ADC are eliminated, higher precision is kept, the cost is reduced, and the balance between the precision and the cost is realized.

Description

Technical Field

[0001] The present application relates to the technical field of over-voltage and under-voltage protection, and in particular to an over-voltage and under-voltage protection circuit. Background Art

[0002] In electronic devices, power management is a vital link. In order to protect electronic devices from voltage fluctuations, over-voltage 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 avoiding damage to the equipment.

[0003] At present, the over-voltage and under-voltage protection circuits of related technologies are usually implemented using a single-chip microcomputer or a comparator. In single-chip microcomputer applications, voltage information is collected through an analog-to-digital converter (ADC), and then judgment and control are performed based on a preset threshold. The comparator application compares the collected voltage with a reference voltage to achieve the over-voltage and under-voltage protection function. These solutions require corresponding peripheral components to support the normal operation of the circuit.

[0004] However, when using a single-chip microcomputer, different ADC bits will lead to different degrees of temperature control errors. For example, the error of an 8-bit single-chip microcomputer can reach 39mV (1 / 2 8 ), while the error of a 12-bit microcontroller is about 9.6mV (1 / 2 12 ), although increasing the number of ADC bits can improve accuracy, it will also increase cost. Therefore, an over-voltage and under-voltage protection circuit that maintains a balance between accuracy and cost is needed. Summary of the invention

[0005] The present application provides an over-voltage and under-voltage protection circuit, which is used to improve detection accuracy while maintaining cost.

[0006] In a first aspect, the present application provides an over-voltage and under-voltage protection circuit, including: an under-voltage protection circuit and an over-voltage protection circuit; The undervoltage protection circuit includes an undervoltage control subcircuit and an undervoltage protection subcircuit; The reference end of the undervoltage control subcircuit is connected to the target area, the input end is connected to the external high level, and the output end is connected to the detection end of the undervoltage protection subcircuit; 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, introduce the external high level from the input end and output it from the output end; The input end of the undervoltage protection subcircuit is connected to the first pin of the chip, and the output end is connected to the external low level, and is used to connect the first pin to the external low level when the detection end detects the external high level, and the level requirement of the first pin is greater than the external low level; The overvoltage protection circuit includes an overvoltage control subcircuit and an overvoltage protection subcircuit; The reference end of the overvoltage control subcircuit is connected to the target area, the input end is connected to the external high level, and the output end is connected to the detection end of the overvoltage protection subcircuit, so as 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 end switches from outputting the external high level to outputting the preset control voltage; The input end of the overvoltage protection subcircuit is connected to an external high level, and the output end is connected to the second pin of the chip, which is used to cut off the connection between the second pin and the external high level when the detection end detects a preset control voltage, wherein the level requirement of the second pin is greater than that of the first pin.

[0007] By adopting the above technical solution, 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 will be activated. The undervoltage protection subcircuit realizes protection by connecting the first pin of the chip to the external low level, reducing the output power or completely shutting down the output. The internal logic of the control chip is utilized to realize accurate undervoltage protection without complex ADC conversion. The overvoltage protection subcircuit realizes protection by cutting off the connection between the second pin and the external high level. By cutting off the external high level connection, these pins will return to the low level state due to the action of the internal pull-down resistor, so that the chip stops working. Since a high-bit ADC is not required, the quantization error and nonlinear error associated with the ADC are eliminated. At the same time, the key control pins of the chip are directly operated instead of through a complex analog-to-digital conversion process. This direct control can reduce intermediate links and reduce the possibility of error accumulation. Therefore, the solution reduces costs while maintaining high accuracy, achieving a balance between accuracy and cost.

[0008] In combination with some embodiments of the first aspect, in some embodiments, the undervoltage protection circuit further includes an undervoltage difference adjustable subcircuit; The detection end of the undervoltage hysteresis adjustable subcircuit is connected to the output end of the undervoltage control subcircuit, and the input end is interconnected with the reference end and the target area of ​​the undervoltage control subcircuit; when the detection end detects an external high level, a feedback network is formed between the reference end and the target area of ​​the undervoltage control subcircuit, so that the voltage obtained by the detection end of the undervoltage protection subcircuit is reduced.

[0009] 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 end and the target area of ​​the undervoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection end of the undervoltage protection subcircuit, which can prevent the frequent switching of the protection circuit caused by repeated fluctuations of the voltage near the critical point. Specifically, when the voltage recovers from the undervoltage state, it needs to reach a higher threshold to release the protection state, which avoids the frequent switching phenomenon that may occur during the slow recovery of the voltage.

[0010] In combination with some embodiments of the first aspect, in some embodiments, the undervoltage protection circuit further includes an undervoltage compensation subcircuit; The input end of the undervoltage compensation subcircuit is interconnected with the reference end and the target area of ​​the undervoltage control subcircuit, and the output end of the undervoltage compensation subcircuit is interconnected with the input end and the output end of the undervoltage control subcircuit, so as to slow down the voltage rising speed when the input end voltage of the undervoltage control subcircuit increases, and slow down the voltage falling speed when the output end voltage of the undervoltage control subcircuit decreases.

[0011] By adopting the above technical solution, by connecting with the input and output ends of the undervoltage control subcircuit, it plays a buffering role when the voltage changes. When the input voltage of the undervoltage control subcircuit increases, the undervoltage compensation subcircuit will slow down the voltage rise speed; when the output voltage decreases, it will slow down the voltage drop speed, 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.

[0012] In combination with some embodiments of the first aspect, in some embodiments, the undervoltage protection circuit further includes a rectifier and filter subcircuit; The reference end of the undervoltage control subcircuit is connected to the target area through the rectification and filtering subcircuit, and the reference end of the overvoltage control subcircuit is connected to the target area through the rectification and filtering subcircuit; it is used to rectify and filter the voltage of the target area and then input it into the reference end of the undervoltage control subcircuit and the reference end of the overvoltage control subcircuit respectively.

[0013] By adopting the above technical solution, the rectifier filter subcircuit is located between the target area and the reference end of the undervoltage control subcircuit and the overvoltage control subcircuit, ensuring that only positive voltage is transmitted, avoiding potential damage to the circuit caused by negative voltage. Secondly, the filtering function can smooth voltage fluctuations and filter out high-frequency noise and transient interference. The processed voltage signal is more stable and reliable, providing an accurate reference voltage for the undervoltage and overvoltage control subcircuits, reducing false triggering and improving detection accuracy.

[0014] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes a voltage stabilization subcircuit; The input end of the voltage stabilization subcircuit is interconnected with the output end of the overvoltage protection subcircuit 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.

[0015] By adopting the above technical solution, the voltage stabilizing subcircuit is connected to the output end of the overvoltage protection subcircuit and the second pin of the chip, and plays a key role in normal working state (that is, when the voltage in the target area is not higher than the preset overvoltage protection voltage), and the voltage stabilizing subcircuit stabilizes the voltage received by the second pin at a preset stable voltage value. It ensures that the second pin of the chip obtains stable power supply within the normal working range, and improves the working efficiency and life of the chip.

[0016] In combination with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes an overvoltage difference adjustable subcircuit; The detection end and input end of the overvoltage hysteresis adjustable subcircuit are interconnected with the output end of the overvoltage control subcircuit, and the output end is interconnected with the reference end and target area of ​​the overvoltage control subcircuit; when the detection end detects a preset voltage, a feedback network is formed between the reference end and the target area of ​​the overvoltage control subcircuit, so that the voltage obtained by the detection end of the overvoltage protection subcircuit is reduced.

[0017] 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 end and the target area of ​​the overvoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection end of the overvoltage protection subcircuit, thereby preventing the protection circuit from switching frequently 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 value to release the protection state, which avoids the frequent switching phenomenon that may occur during the slow decline of voltage.

[0018] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes an overvoltage compensation subcircuit; The input end of the overvoltage compensation subcircuit is interconnected with the reference end and the target area of ​​the overvoltage control subcircuit, and the output end of the overvoltage compensation subcircuit is interconnected with the input end and the output end of the overvoltage control subcircuit, so as to slow down the voltage rising speed when the voltage at the input end of the overvoltage control subcircuit increases, and slow down the voltage falling speed when the voltage at the output end of the overvoltage control subcircuit decreases.

[0019] By adopting the above technical solution, the overvoltage compensation subcircuit is connected to the input and output ends of the overvoltage control subcircuit, and plays a buffering role when the voltage changes. When the input voltage of the overvoltage control subcircuit increases, the overvoltage compensation subcircuit will slow down the voltage rise rate; when the output voltage decreases, it will slow down the voltage drop rate, making the voltage change smoother, which not only avoids the voltage jump problem at the critical point, but also improves the response speed of the circuit near the overvoltage point.

[0020] In a second aspect, the present application provides an over-voltage and under-voltage protection circuit, including: a three-terminal adjustable shunt parallel regulator Q1, a voltage regulator D5, a transistor Q2, a three-terminal adjustable shunt parallel regulator Q6, a voltage regulator D7, a transistor Q4, and a transistor Q5; The reference end of the three-terminal adjustable shunt shunt regulator Q1 is connected to the target area, the input end is connected to the cathode of the voltage regulator tube D5, and the external high level is interconnected, and the output end is grounded; The output end of the voltage regulator D5 is connected to the base of the transistor Q2; The sending stage of transistor Q2 is connected to the first pin, and the collector stage is grounded; The reference end of the three-terminal adjustable shunt shunt regulator Q6 is connected to the target area, the input end is connected to the cathode of the voltage regulator tube D7, and the external high level is interconnected, and the output end is grounded; The output end of the voltage regulator tube D7 is connected to the base of the Darlington tube composed of the transistor Q4 and the transistor Q5; The sending stage of the Darlington tube is connected to the external high level, and the collector stage of the Darlington tube is connected to the second pin.

[0021] In a third aspect, the present application provides an over-voltage and under-voltage protection circuit, including: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a rectifier diode D1, a rectifier diode D2, a rectifier diode D3, a rectifier diode D4, a rectifier diode D6, a zener diode D5, a zener diode D7, a zener diode D8, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a three-terminal adjustable shunt parallel regulator Q1, a three-terminal adjustable shunt parallel regulator Q6, a transistor Q2, a transistor Q3, a transistor Q4, a transistor Q5, and a MOS tube Q7; The anode of the rectifier diode D1 and the anode of the rectifier diode D3 are both connected to the target area, the cathode of the rectifier diode D1 and the cathode of the rectifier diode D3 are both grounded through the capacitor C2, and are connected to the anode of the rectifier diode D4 through the resistor R1, the resistor R2, and the resistor R3 connected in series in sequence; The cathode of the rectifier diode D4 is interconnected with the first end of the resistor R7, the first end of the capacitor C3, and the first end of the resistor R13; The second end of the resistor R7 is interconnected with the first end of the resistor R9, the first end of the resistor R10, the first end of the capacitor C4, the first end of the capacitor C1, and the reference end of the three-terminal adjustable shunt shunt regulator Q1; An input end of a three-terminal adjustable shunt shunt regulator Q1, a second end of a capacitor C1, a first end of a resistor R4, and a cathode of a voltage regulator D5 are interconnected, and an output end of the three-terminal adjustable shunt shunt regulator Q1 is grounded; The second end of the resistor R4 is connected to the cathode of the rectifier diode D2; The anode of the rectifier diode D2 is connected to the external high level; The anode of the voltage regulator tube D5 is connected to the first end of the resistor R5; The second end of the resistor R5 is interconnected with the first end of the resistor R8, the base of the transistor Q2, and the base of the transistor Q3; 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; The emitter of the transistor Q3 is connected to the second end of the resistor R10, and the collector of the transistor Q3 is grounded; The second end of the resistor R13 is connected to the first end of the resistor R16, the first end of the resistor R17, the first end of the capacitor C5, the first end of the capacitor C6, and the reference end of the three-terminal adjustable shunt shunt regulator Q6; The second end of the resistor R16 and the second end of the capacitor C6 are grounded; The input end of the three-terminal adjustable shunt shunt regulator Q6 is interconnected with the second end of the capacitor C5, the first end of the resistor R12, and the cathode of the voltage regulator D7; the output end of the three-terminal adjustable shunt shunt regulator Q6 is grounded; The second end of the resistor R12 is connected to the cathode of the rectifier diode D6; The anode of the rectifier diode D6 is connected to the external high level; The anode of the voltage regulator tube D7 is connected to the first end of the resistor R14; The second end of the resistor R14 is connected to the base of the Darlington transistor composed of the transistor Q4 and the transistor Q5 and the first end of the resistor R15; The emitter of the Darlington tube is connected to the external high level through the resistor R11, and the collector of the transistor Q4 is interconnected with the first end of the capacitor C7, the second end of the resistor R15, the first end of the resistor R18, the cathode of the voltage regulator tube D8, and the second pin of the chip; The second end of the capacitor C7, the anode of the voltage regulator tube D8 and the gate of the MOS tube Q7 are connected; The source of the MOS tube Q7 is connected to the second end of the resistor R17; The second end of the resistor R18 is grounded through the resistor R19; the second end of the resistor R18 is connected to the drain of the MOS tube Q7.

[0022] One or more technical solutions provided in the embodiments of the present application have at least the following technical effects or advantages: 1. 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 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 uses the internal logic of the control chip to 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. At the same time, the key control pins of the chip are directly operated instead of through a complex analog-to-digital conversion process. This direct control can reduce intermediate links and reduce the possibility of error accumulation. Therefore, this solution reduces costs while maintaining high accuracy, achieving a balance between accuracy and cost.

[0023] 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 end and the target area of ​​the undervoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained at the detection end of the undervoltage protection subcircuit, which can prevent the frequent switching of the protection circuit caused by repeated fluctuations of the voltage near the critical point. Specifically, when the voltage recovers from the undervoltage state, it needs to reach a higher threshold to release the protection state, which avoids the frequent switching phenomenon that may occur during the slow recovery of the voltage.

[0024] 3. By connecting to the input and output of the undervoltage control subcircuit, it plays a buffering role when the voltage changes. When the input voltage of the undervoltage control subcircuit increases, the undervoltage compensation subcircuit will slow down the voltage rise speed; when the output voltage decreases, it will slow down the voltage drop speed, making the voltage change smoother, which not only avoids the voltage jump problem at the critical point, but also improves the response speed of the circuit near the undervoltage point. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a circuit diagram of an over-voltage and under-voltage protection circuit in an embodiment of the present application; Figure 2 This is another circuit diagram of the over-voltage and under-voltage protection circuit in the embodiment of the present application; DETAILED DESCRIPTION The terms used in the following embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to be used as limitations to the present application. As used in the specification and appended claims of the present application, the singular expressions "one", "one", "said", "above", "the" and "this" are intended to also include plural expressions, unless there is a clear indication to the contrary in the context. It should also be understood that the term "and / or" used in the present application refers to and includes any or all possible combinations of one or more listed items.

[0026] In the following, the terms "first" and "second" are used for descriptive purposes only and are not to be understood as suggesting or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features, and in the description of the embodiments of the present application, unless otherwise specified, "plurality" means two or more.

[0027] refer to Figure 1 , Figure 1 This is a circuit diagram of an over-voltage and under-voltage protection circuit in an embodiment of the present application; In a first aspect, the present application provides an over-voltage and under-voltage protection circuit, including: an under-voltage protection circuit and an over-voltage protection circuit; This circuit achieves bidirectional protection against voltage anomalies by integrating undervoltage and overvoltage protection mechanisms. The undervoltage protection circuit is responsible for monitoring and responding to low voltage conditions to prevent the chip from malfunctioning or being damaged due to insufficient voltage. The overvoltage protection circuit is responsible for monitoring and responding to high voltage conditions to avoid damage to the chip due to excessive voltage.

[0028] The undervoltage protection circuit includes an undervoltage control subcircuit and an undervoltage protection subcircuit; The reference end of the undervoltage control subcircuit is connected to the target area, the input end is connected to the external high level, and the output end is connected to the detection end of the undervoltage protection subcircuit; 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, introduce the external high level from the input end and output it from the output end; The target area is the monitoring point of the circuit that needs to be protected.

[0029] The undervoltage control subcircuit collects the voltage of the target area in real time through its reference terminal, and compares this voltage with the preset undervoltage protection voltage set internally. When it is detected that the voltage of the target area is lower than the preset undervoltage protection voltage, the undervoltage control subcircuit activates its internal switch or logic circuit and introduces an external high-level signal from the input terminal; In some specific embodiments, the inverting input terminal of the operational amplifier is connected to a reference voltage source as a preset undervoltage protection voltage; the non-inverting input terminal is connected to the target area for collecting real-time voltage; the output terminal 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, and the emitter or source is used as the output terminal; when the voltage of the target area is lower than the preset value, the operational amplifier outputs a high level, turning on the transistor or MOSFET and transmitting the high level signal to the output terminal.

[0030] In other specific embodiments, a three-terminal adjustable shunt shunt regulator, such as TL431, is selected; the cathode K terminal of the regulator is connected to the positive pole of the power supply through a current limiting resistor, and the anode A terminal of the regulator is connected to a low potential (for example, ground); the reference terminal R terminal of the regulator is connected to the target area for collecting real-time voltage; a simple voltage divider circuit is designed to reduce the voltage of the target area to a range acceptable to the regulator (usually 0-2.5V); and a pull-up resistor is added to the K terminal to provide a high-level output in a high-impedance state. The working principle of the circuit is as follows: when the voltage at the reference terminal R is greater than 2.5V (i.e. the voltage in the target area is normal), the operational amplifier inside the voltage regulator outputs a low level, so that the base voltage of the internal transistor is high. At this time, the collector junction and the emitter junction of the internal transistor are turned on, which is equivalent to the cathode K terminal and the anode A terminal being turned on. The voltage at the K terminal is lower than 2.5V, and the output is a low level; when the voltage at the reference terminal R is less than 2.5V (i.e. undervoltage occurs), the operational amplifier inside the voltage regulator outputs a high level, so that the base voltage of the internal transistor is low. At this time, the collector junction and the emitter junction of the internal transistor are both reverse biased, the transistor is cut off, and the internal diode in parallel is also in the cut-off state. In this case, the voltage between the K terminal and the A terminal is equal to the power supply voltage, the K terminal is in a high impedance state, and a high level output is obtained through the pull-up resistor, indicating that an undervoltage condition occurs.

[0031] In this way, under different circumstances, the K terminal of the three-terminal adjustable shunt shunt regulator can output a clear high-level or low-level signal; the stability is high, the difference in output level is obvious, the value is very stable, it is not affected by external factors, and it hardly fluctuates.

[0032] The input end of the undervoltage protection subcircuit is connected to the first pin of the chip, and the output end is connected to the external low level, and is used to connect the first pin to the external low level when the detection end detects the external high level, and the level requirement of the first pin is greater than the external low level; 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 end (i.e., the detection end of the undervoltage protection subcircuit). After receiving this high-level signal, the undervoltage protection subcircuit will immediately change its internal state and switch the input end originally connected to the first pin of the chip to the output end 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 being protected.

[0033] The overvoltage protection circuit includes an overvoltage control subcircuit and an overvoltage protection subcircuit; The reference end of the overvoltage control subcircuit is connected to the target area, the input end is connected to the external high level, and the output end is connected to the detection end of the overvoltage protection subcircuit, so as 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 end switches from outputting the external high level to outputting the preset control voltage; It should be noted that the principles and steps of the overvoltage control subcircuit are the same as those of the undervoltage control subcircuit. The relevant principles and steps can be used for reference, but the specific settings are different. The preset overvoltage protection voltage is higher than the preset undervoltage protection voltage, which will not be repeated here.

[0034] The input end of the overvoltage protection subcircuit is connected to an external high level, and the output end is connected to the second pin of the chip, which is used to cut off the connection between the second pin and the external high level when the detection end detects a preset control voltage, wherein the level requirement of the second pin is greater than that of the first pin.

[0035] It should be noted that the principles and steps of the overvoltage protection subcircuit are the same as those of the undervoltage protection subcircuit, and the relevant principles and steps can be used for reference.

[0036] The first pin is the chip dimming pin, enable pin, COMP compensation pin and other pins with high and low levels; the first pin is the control chip PWM pin, enable pin, COMP compensation pin and other pins with high and low levels.

[0037] It needs to be explained that the second pin is usually designed to be valid at a high level. When these pins are at a high level, the chip works normally; when at a low level, the chip stops working. There are usually pull-down resistors inside the chip to ensure that when there is no external signal input, these pins default to a low level state, thereby putting the chip in a safe non-working state.

[0038] It can be seen that 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 will be activated. The undervoltage protection subcircuit realizes protection by connecting the first pin of the chip to the external low level, 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 realizes protection by cutting off the connection between the second pin and the external high level. By cutting off the external high-level connection, these pins will return to the low-level state due to the action of the internal pull-down resistor, so that the chip stops working. Since there is no need to use a high-bit ADC, the quantization error and nonlinear error associated with the ADC are eliminated. At the same time, the key control pins of the chip are directly operated instead of through a complex analog-to-digital conversion process. This direct control can reduce the intermediate links and reduce the possibility of error accumulation. Therefore, this solution reduces the cost while maintaining high accuracy, achieving a balance between accuracy and cost.

[0039] In some embodiments, the undervoltage protection circuit further includes an undervoltage difference adjustable subcircuit; The detection end of the undervoltage hysteresis adjustable subcircuit is connected to the output end of the undervoltage control subcircuit, and the input end is interconnected with the reference end and the target area of ​​the undervoltage control subcircuit; when the detection end detects an external high level, a feedback network is formed between the reference end and the target area of ​​the undervoltage control subcircuit, so that the voltage obtained by the detection end of the undervoltage protection subcircuit is reduced.

[0040] 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 end of the undervoltage control subcircuit and the target area. The function of this feedback network is to reduce the voltage value sensed by the undervoltage control subcircuit. The purpose of this is to ensure that even if the actual voltage rises slightly, it will not immediately trigger the release of the undervoltage protection. Only when the actual voltage increases significantly and exceeds the set hysteresis value, the undervoltage protection will be released.

[0041] In some specific embodiments, an operational amplifier with a low bias current is selected; the non-inverting input of the operational amplifier is connected to the target area; 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 and the inverting input of the operational amplifier; a small resistor controlled by a MOSFET switch is connected in parallel to the feedback resistor; the gate of the MOSFET is connected to the output of the undervoltage control subcircuit, and when undervoltage is detected, the MOSFET is turned on, changing the gain of the feedback network, thereby reducing the voltage sensed by the undervoltage control subcircuit.

[0042] In some embodiments, an appropriate NPN transistor and several resistors R are selected; a resistor A is connected between the target area and the reference end of the undervoltage control subcircuit; a series circuit is connected in parallel at both ends of resistor A, and the series circuit is formed by the collector-emitter channel of the transistor and another resistor B in series; the base of the transistor is connected to the output end of the undervoltage control subcircuit through a current limiting resistor; and the resistance values ​​of resistor A and resistor B are selected according to the required hysteresis value. When undervoltage is detected, the transistor is turned on, so that resistor B is connected in parallel with resistor A to form a voltage divider network, thereby reducing the voltage sensed by the undervoltage control subcircuit and achieving hysteresis regulation.

[0043] It can be seen that 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 end and the target area of ​​the undervoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained at the detection end of the undervoltage protection subcircuit, which can prevent the frequent switching of the protection circuit caused by repeated fluctuations of the voltage near the critical point. Specifically, when the voltage recovers from the undervoltage state, it needs to reach a higher threshold to release the protection state, which avoids the frequent switching phenomenon that may occur during the slow recovery of the voltage.

[0044] In some embodiments, the undervoltage protection circuit further includes an undervoltage compensation subcircuit; The input end of the undervoltage compensation subcircuit is interconnected with the reference end and the target area of ​​the undervoltage control subcircuit, and the output end of the undervoltage compensation subcircuit is interconnected with the input end and the output end of the undervoltage control subcircuit, so as to slow down the voltage rising speed when the input end voltage of the undervoltage control subcircuit increases, and slow down the voltage falling speed when the output end voltage of the undervoltage control subcircuit decreases.

[0045] When the voltage in the target area begins to rise, the undervoltage compensation subcircuit exerts an influence on the input end of the undervoltage control subcircuit through its output end, so that the rising speed of the input voltage slows down. This delaying effect can prevent the release of the undervoltage protection from being falsely triggered due to instantaneous voltage fluctuations. Similarly, when the output voltage of the undervoltage control subcircuit begins to drop, the undervoltage compensation subcircuit will also slow down the falling speed of the output voltage through its output end, which can avoid the immediate triggering of the undervoltage protection due to a temporary small voltage drop, thereby improving the stability and anti-interference ability. The existence of the undervoltage compensation subcircuit makes the undervoltage protection circuit have a certain "inertia", which can better adapt to the voltage fluctuations in the actual working environment and reduce the occurrence of false operations.

[0046] In some specific embodiments, an operational amplifier with high input impedance is selected; the operational amplifier is configured as a voltage follower, and its non-inverting input terminal is connected to the target area; an RC low-pass filter network is connected between the output terminal of the operational amplifier and the input terminal of the undervoltage control subcircuit; the resistance and capacitance values ​​are selected so that the time constant of the RC network can effectively smooth the voltage fluctuation; a Zener diode is connected in parallel to the output terminal of the RC network to limit the voltage variation range. This can effectively slow down the rapid change of voltage and provide a more stable reference signal for undervoltage control.

[0047] In some specific embodiments, a capacitor with a suitable capacitance is selected, one end of which is connected to the input end of the undervoltage control subcircuit and the other end is grounded; a small resistor is connected in series between the capacitor and the target area to limit the charge and discharge current; a diode is connected between the connection point of the resistor and the capacitor and the output end of the undervoltage control subcircuit, with the positive pole of the diode facing the capacitor; the capacitance of the capacitor is adjusted as required to obtain the ideal voltage change response characteristics; a large-resistance discharge resistor is connected in parallel at both ends of the capacitor to slowly release the charge on the capacitor. This simple design uses the charge and discharge characteristics of the capacitor to naturally slow down the voltage change speed and provide a basic undervoltage compensation function.

[0048] It can be seen that by connecting to the input and output ends of the undervoltage control subcircuit, it plays a buffering role when the voltage changes. When the input voltage of the undervoltage control subcircuit increases, the undervoltage compensation subcircuit will slow down the voltage rise rate; when the output voltage decreases, it will slow down the voltage drop rate, making the voltage change smoother, which not only avoids the voltage jump problem at the critical point, but also improves the response speed of the circuit near the undervoltage point.

[0049] In some embodiments, the undervoltage protection circuit further includes a rectifier and filter subcircuit; The reference end of the undervoltage control subcircuit is connected to the target area through the rectification and filtering subcircuit, and the reference end of the overvoltage control subcircuit is connected to the target area through the rectification and filtering subcircuit; it is used to rectify and filter the voltage of the target area and then input it into the reference end of the undervoltage control subcircuit and the reference end of the overvoltage control subcircuit respectively.

[0050] The rectifier and filter subcircuit first receives a voltage signal from the target area that may contain an AC component or noise, and converts the AC voltage into a unidirectional pulsating DC voltage through a rectifier circuit, such as a diode bridge rectifier. Subsequently, the filter circuit (usually including capacitors and inductors) smoothes these pulsations and reduces the ripple component in the voltage. The voltage signal after rectification and filtering becomes more stable and smooth, which helps to improve the working accuracy and reliability of the undervoltage control subcircuit and the overvoltage control subcircuit. The output of the rectifier and filter subcircuit is connected to the reference end of the undervoltage control subcircuit and the overvoltage control subcircuit, respectively, to provide these two subcircuits with processed and reliable voltage reference signals, which can effectively reduce the impact of power supply fluctuations and electromagnetic interference on the voltage protection function and improve the overall anti-interference ability and working stability.

[0051] In some specific embodiments, four rectifier diodes of the same specification are selected to form a full-wave bridge rectifier circuit; the AC input end of the bridge rectifier circuit is connected to the target area; a large-capacity electrolytic capacitor is connected in parallel to the DC output end 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 to the output end of the LC filter circuit to filter out high-frequency noise; the filtered output is connected to the reference end of the undervoltage control subcircuit and the overvoltage control subcircuit respectively; In some specific embodiments, a fast recovery rectifier diode is selected, with its positive electrode connected to the target area and its negative electrode as the output end; a large-capacity electrolytic capacitor is connected in parallel to the output end of the diode for main filtering; when selecting the capacitance of the electrolytic capacitor, the load current and the allowable ripple voltage are considered to ensure sufficient filtering effect; a small-capacity ceramic capacitor is connected in parallel to both ends of the electrolytic capacitor to filter out high-frequency noise; if needed, 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 end is connected to the reference end of the undervoltage control subcircuit and the overvoltage control subcircuit respectively.

[0052] It can be seen that the rectifier filter subcircuit is located between the target area and the reference end of the undervoltage control subcircuit and the overvoltage control subcircuit, ensuring that only positive voltage is transmitted, avoiding potential damage to the circuit caused by negative voltage. Secondly, the filtering function can smooth voltage fluctuations and filter out high-frequency noise and transient interference. The processed voltage signal is more stable and reliable, providing an accurate reference voltage for the undervoltage and overvoltage control subcircuits, reducing false triggering and improving detection accuracy.

[0053] In conjunction with some embodiments of the first aspect, in some embodiments, the overvoltage protection circuit further includes a voltage stabilization subcircuit; The input end of the voltage stabilization subcircuit is interconnected with the output end of the overvoltage protection subcircuit 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.

[0054] It can be seen that the voltage stabilization subcircuit is connected to the output end of the overvoltage protection subcircuit and the second pin of the chip, and plays a key role in normal working state (that is, when the voltage in the target area is not higher than the preset overvoltage protection voltage). The voltage stabilization subcircuit stabilizes the voltage received by the second pin at a preset stable voltage value. This ensures that the second pin of the chip obtains stable power supply within the normal working range, and improves the working efficiency and life of the chip.

[0055] In some embodiments, the overvoltage protection circuit further includes an overvoltage difference adjustable subcircuit; The detection end and input end of the overvoltage hysteresis adjustable subcircuit are interconnected with the output end of the overvoltage control subcircuit, and the output end is interconnected with the reference end and target area of ​​the overvoltage control subcircuit; when the detection end detects a preset voltage, a feedback network is formed between the reference end and the target area of ​​the overvoltage control subcircuit, so that the voltage obtained by the detection end of the overvoltage protection subcircuit is reduced.

[0056] It should be noted that the overvoltage hysteresis adjustable sub-circuit is similar to the undervoltage hysteresis adjustable sub-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.

[0057] It can be seen that when the overvoltage control subcircuit detects overvoltage and outputs a preset voltage, the overvoltage hysteresis adjustable subcircuit forms a feedback network between the reference end and the target area of ​​the overvoltage control subcircuit. The function of this feedback network is to reduce the voltage obtained by the detection end of the overvoltage protection subcircuit, thereby preventing the protection circuit from switching frequently 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 to release the protection state, which avoids the frequent switching phenomenon that may occur during the slow decline of voltage.

[0058] In some embodiments, the overvoltage protection circuit further includes an overvoltage compensation subcircuit; The input end of the overvoltage compensation subcircuit is interconnected with the reference end and the target area of ​​the overvoltage control subcircuit, and the output end of the overvoltage compensation subcircuit is interconnected with the input end and the output end of the overvoltage control subcircuit, so as to slow down the voltage rising speed when the voltage at the input end of the overvoltage control subcircuit increases, and slow down the voltage falling speed when the voltage at the output end of the overvoltage control subcircuit decreases.

[0059] 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.

[0060] By adopting the above technical solution, the overvoltage compensation subcircuit is connected to the input and output ends of the overvoltage control subcircuit, and plays a buffering role when the voltage changes. When the input voltage of the overvoltage control subcircuit increases, the overvoltage compensation subcircuit will slow down the voltage rise rate; when the output voltage decreases, it will slow down the voltage drop rate, making the voltage change smoother, which not only avoids the voltage jump problem at the critical point, but also improves the response speed of the circuit near the overvoltage point.

[0061] refer to Figure 2 , Figure 2 This is another circuit diagram of the over-voltage and under-voltage protection circuit in the embodiment of the present application; In a second aspect, the present application provides an over-voltage and under-voltage protection circuit, including: a three-terminal adjustable shunt parallel regulator Q1, a voltage regulator D5, a transistor Q2, a three-terminal adjustable shunt parallel regulator Q6, a voltage regulator D7, a transistor Q4, and a transistor Q5; The reference end of the three-terminal adjustable shunt shunt regulator Q1 is connected to the target area, the input end is connected to the cathode of the voltage regulator tube D5, and the external high level is interconnected, and the output end is grounded; Under normal working conditions, when the voltage in the target area is not less than the preset undervoltage protection voltage of the three-terminal adjustable shunt shunt regulator Q1, the input and output terminals of the three-terminal adjustable shunt shunt regulator Q1 are internally connected. This configuration causes the voltage at the input terminal to be pulled down to a preset low level, which is less than the internal breakdown voltage of the voltage regulator D5. At this time, the voltage regulator D5 remains in the reverse cutoff state.

[0062] When an undervoltage condition occurs, that is, the voltage in the target area drops below the preset undervoltage protection voltage of the three-terminal adjustable shunt shunt regulator Q1, the internal switch of the three-terminal adjustable shunt shunt regulator Q1 is actuated to disconnect the input and output terminals. This causes the voltage at the input terminal to rise to an external high level. This high voltage exceeds the breakdown voltage of the Zener diode D5, causing the Zener diode D5 to enter a reverse breakdown state.

[0063] The output end of the voltage regulator D5 is connected to the base of the transistor Q2; Under normal working conditions: Zener diode D5 is in reverse cut-off state. In this state, the cathode voltage of Zener diode D5 is lower than its breakdown voltage, so Zener diode D5 is not conducting. Since Zener diode D5 is not conducting, its output terminal (anode) voltage is very low, close to zero. This results in insufficient voltage drive for the base of transistor Q2, so transistor Q2 is in cut-off state and is not conducting.

[0064] In the case of undervoltage: the voltage regulator D5 enters the reverse breakdown state. In this state, the voltage regulator D5 starts to conduct.

[0065] The sending stage of transistor Q2 is connected to the first pin, and the collector stage is grounded; Transistor Q2 is configured as a switch circuit. Under normal working conditions, transistor Q2 is in the cut-off state, with high impedance between its emitter and collector, and the first pin remains high. When an undervoltage condition occurs, the base of transistor Q2 is driven by the voltage regulator D5, turning on transistor Q2. After turning on, the emitter voltage of transistor Q2 is close to the collector voltage of its grounded state, effectively pulling the first pin down to near the ground potential.

[0066] The reference end of the three-terminal adjustable shunt shunt regulator Q6 is connected to the target area, the input end is connected to the cathode of the voltage regulator tube D7, and the external high level is interconnected, and the output end is grounded; Under normal working conditions, the voltage in the target area is lower than the preset overvoltage protection voltage of the three-terminal adjustable shunt shunt regulator Q6, and the internal switch of the three-terminal adjustable shunt shunt regulator Q6 is in the off state. At this time, there is a high impedance between its input and output terminals, and the input terminal maintains 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, so that the Zener diode D7 remains in the reverse cut-off state. In the case of overvoltage, the internal switch of the three-terminal adjustable shunt shunt regulator Q6 is closed, and the input and output terminals are turned on, so that the input voltage drops rapidly to a low level close to the ground potential, triggering the subsequent overvoltage protection mechanism.

[0067] The output end of the voltage regulator tube D7 is connected to the base of the Darlington tube composed of the transistor Q4 and the transistor Q5; Under normal working conditions, the voltage regulator D7 is in the on state, and the voltage regulator D7 is maintained at its breakdown voltage, providing a stable driving voltage for 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 of the second pin.

[0068] When an overvoltage occurs, the three-terminal adjustable shunt shunt regulator Q6 is turned on, and the voltage at its input terminal drops rapidly, which causes the voltage difference across the Zener tube D7 to be less than its breakdown voltage, causing the Zener tube D7 to enter a reverse cutoff state. After the Zener tube D7 is cut off, the voltage at its output terminal (anode) drops rapidly, cutting off the driving voltage to the base of the Darlington tube.

[0069] The sending stage of the Darlington tube is connected to the external high level, and the collector stage of the Darlington tube is connected to the second pin.

[0070] Under normal working conditions: the Darlington tube is in the on state, allowing the external high level to pass through the collector-emitter channel of the Darlington tube, providing a stable power supply for the subsequent circuit connected to the second pin.

[0071] In the case of overvoltage, the Darlington tube 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 the subsequent circuits.

[0072] refer to Figure 2 , Figure 2 This is another circuit diagram of the over-voltage and under-voltage protection circuit in the embodiment of the present application; In a third aspect, the present application provides an over-voltage and under-voltage protection circuit, including: a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a resistor R9, a resistor R10, a resistor R11, a resistor R12, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a resistor R17, a resistor R18, a resistor R19, a rectifier diode D1, a rectifier diode D2, a rectifier diode D3, a rectifier diode D4, a rectifier diode D6, a zener diode D5, a zener diode D7, a zener diode D8, a capacitor C1, a capacitor C2, a capacitor C3, a capacitor C4, a capacitor C5, a capacitor C6, a capacitor C7, a three-terminal adjustable shunt parallel regulator Q1, a three-terminal adjustable shunt parallel regulator Q6, a transistor Q2, a transistor Q3, a transistor Q4, a transistor Q5, and a MOS tube Q7; The anode of the rectifier diode D1 and the anode of the rectifier diode D3 are both connected to the target area, the cathode of the rectifier diode D1 and the cathode of the rectifier diode D3 are both grounded through the capacitor C2, and are connected to the anode of the rectifier diode D4 through the resistor R1, the resistor R2, and the resistor R3 connected in series in sequence; The parallel configuration of rectifier diodes D1 and D3 provides bidirectional reverse voltage protection. Regardless of the polarity of the input voltage, there is always a diode that blocks the reverse current, effectively preventing the circuit from being damaged. Capacitor C2 is grounded to form 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 limits the current, but also forms a voltage divider network.

[0073] The cathode of the rectifier diode D4 is interconnected with the first end of the resistor R7, the first end of the capacitor C3, and the first end of the resistor R13; The cathode of the rectifier diode D4 provides a stable positive voltage source, which is distributed to the undervoltage protection circuit (through R7) and the overvoltage protection circuit (through R13) at the same time. 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.

[0074] The second end of the resistor R7 is interconnected with the first end of the resistor R9, the first end of the resistor R10, the first end of the capacitor C4, the first end of the capacitor C1, and the reference end of the three-terminal adjustable shunt shunt regulator Q1; Resistors R9 and R10 are connected in parallel to form a voltage divider network; capacitor C4 provides a key filtering function; and capacitor C1 performs dynamic compensation.

[0075] An input end of a three-terminal adjustable shunt shunt regulator Q1, a second end of a capacitor C1, a first end of a resistor R4, and a cathode of a voltage regulator D5 are interconnected, and an output end of the three-terminal adjustable shunt shunt regulator Q1 is grounded; Resistor R4 is used to limit the external high-level current; The second end of the resistor R4 is connected to the cathode of the rectifier diode D2; The main function of the rectifier diode D2 is to prevent reverse voltage; The anode of the rectifier diode D2 is connected to the external high level; The anode of the voltage regulator tube D5 is connected to the first end of the resistor R5; Resistor R5 is used to stabilize the output voltage of voltage regulator tube D5; The second end of the resistor R5 is interconnected with the first end of the resistor R8, the base of the transistor Q2, and the base of the transistor Q3; 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 working 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.

[0076] 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; Resistor R6 controls and limits the current flowing to the first pin; The emitter of the transistor Q3 is connected to the second end of the resistor R10, and the collector of the transistor Q3 is grounded; When the cathode of the three-terminal adjustable shunt shunt regulator Q1 outputs a high potential, the transistor Q3 is turned on. Resistor R10 is directly connected in parallel with resistor R9. This configuration allows flexible adjustment of current distribution and voltage division. Transistor Q3 and resistor R10 form a feedback network, which further reduces the voltage of the reference pin of the three-terminal adjustable shunt shunt regulator Q1 when the cathode of the three-terminal adjustable shunt shunt regulator Q1 outputs a high potential. This mechanism ensures that the cathode of the three-terminal adjustable shunt shunt regulator Q1 can continuously output a high potential, realizing the adjustability of the hysteresis. By adjusting the resistance values ​​of resistors R10 and R9, the hysteresis can be precisely controlled to meet different application requirements.

[0077] The second end of the resistor R13 is connected to the first end of the resistor R16, the first end of the resistor R17, the first end of the capacitor C5, the first end of the capacitor C6, and the reference end of the three-terminal adjustable shunt shunt regulator Q6; Resistor R16 and resistor R17 are configured in parallel to form a feedback network. Capacitor C6 plays a filtering role in the circuit, and capacitor C5 is specifically used to achieve the hysteresis function of overvoltage protection.

[0078] The second end of the resistor R16 and the second end of the capacitor C6 are grounded; The input end of the three-terminal adjustable shunt shunt regulator Q6 is interconnected with the second end of the capacitor C5, the first end of the resistor R12, and the cathode of the voltage regulator D7; the output end of the three-terminal adjustable shunt shunt regulator Q6 is grounded; Resistor R12 is used to limit the current or set the voltage of the cathode of the three-terminal adjustable shunt shunt regulator Q6; The second end of the resistor R12 is connected to the cathode of the rectifier diode D6; Rectifier diode D6 is used to protect the circuit from external high-level reverse current.

[0079] The anode of the rectifier diode D6 is connected to the external high level; The anode of the voltage regulator tube D7 is connected to the first end of the resistor R14; Resistor R14 is used to stabilize the voltage of the anode of Zener diode D7.

[0080] The second end of the resistor R14 is connected to the base of the Darlington transistor composed of the transistor Q4 and the transistor Q5 and the first end of the resistor R15; The emitter of the Darlington tube is connected to the external high level through the resistor R11, and the collector of the transistor Q4 is interconnected with the first end of the capacitor C7, the second end of the resistor R15, the first end of the resistor R18, the cathode of the voltage regulator tube D8, and the second pin of the chip; The resistor R11 is used to control the current of the second pin.

[0081] The second end of the capacitor C7, the anode of the voltage regulator tube D8 and the gate of the MOS tube Q7 are connected; The capacitor C7 and the voltage regulator D8 together form a clamping circuit, which cooperates with the voltage regulator D8 to clamp the voltage received by the second pin to a preset stable voltage value, ensuring that the voltage does not exceed the preset stable voltage value; The source of the MOS tube Q7 is connected to the second end of the resistor R17; The second end of the resistor R18 is grounded through the resistor R19; the second end of the resistor R18 is connected to the drain of the MOS tube Q7.

[0082] The resistor R18 controls the current entering the gate of the MOS tube Q7. The resistor R19 is connected between the source of the MOS tube Q7 and the ground, and is used to pull down or set the threshold voltage of Q7.

Claims

1. Over-voltage and under-voltage protection circuit, characterized in that: include: Undervoltage protection circuit and overvoltage protection circuit; The undervoltage protection circuit includes an undervoltage control subcircuit and an undervoltage protection subcircuit; The reference end of the undervoltage control subcircuit is connected to the target area, the input end is connected to the external high level, and the output end is connected to the detection end of the undervoltage protection subcircuit; 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, introduce the external high level from the input end and output it from the output end; The input end of the undervoltage protection subcircuit is connected to the first pin of the chip, and the output end is connected to the external low level, and is used to connect the first pin to the external low level when the detection end detects the external high level, and the level requirement of the first pin is greater than the external low level; The overvoltage protection circuit includes an overvoltage control subcircuit and an overvoltage protection subcircuit; The reference end of the overvoltage control subcircuit is connected to the target area, the input end is connected to an external high level, and the output end is connected to the detection end of the overvoltage protection subcircuit, so as 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 end switches from outputting an external high level to outputting a preset control voltage; The input end of the overvoltage protection subcircuit is connected to an external high level, and the output end is connected to the second pin of the chip, and is used to cut off the connection between the second pin and the external high level when the detection end detects a preset control voltage, wherein the level requirement of the second pin is greater than that of the first pin.

2. The circuit according to claim 1, characterized in that The undervoltage protection circuit also includes an undervoltage difference adjustable subcircuit; The detection end of the undervoltage hysteresis adjustable subcircuit is connected to the output end of the undervoltage control subcircuit, and the input end is interconnected with the reference end of the undervoltage control subcircuit and the target area; When the detection end detects an external high level, a feedback network is formed between the reference end of the undervoltage control subcircuit and the target area, so that the voltage obtained by the detection end of the undervoltage protection subcircuit is reduced.

3. The circuit according to claim 1, characterized in that The undervoltage protection circuit also includes an undervoltage compensation subcircuit; The input end of the undervoltage compensation subcircuit is interconnected with the reference end of the undervoltage control subcircuit and the target area, and the output end of the undervoltage compensation subcircuit is interconnected with the input end and the output end of the undervoltage control subcircuit, and is used to slow down the voltage rising speed when the input end voltage of the undervoltage control subcircuit increases, and slow down the voltage falling speed when the output end voltage of the undervoltage control subcircuit decreases.

4. The circuit according to claim 1, characterized in that The undervoltage protection circuit also includes a rectifier and filter subcircuit; The reference end of the undervoltage control subcircuit is connected to the target area through the rectification and filtering subcircuit, and the reference end of the overvoltage control subcircuit is connected to the target area through the rectification and filtering subcircuit; It is used to rectify and filter the voltage of the target area and then input the voltage to the reference end of the undervoltage control subcircuit and the reference end of the overvoltage control subcircuit respectively.

5. The circuit according to claim 1, characterized in that The overvoltage protection circuit also includes a voltage stabilization subcircuit; The input end of the voltage stabilization subcircuit is interconnected with the output end of the overvoltage protection subcircuit 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 difference adjustable subcircuit; The detection terminal and the input terminal of the overvoltage hysteresis adjustable subcircuit are interconnected with the output terminal of the overvoltage control subcircuit, and the output terminal is interconnected with the reference terminal of the overvoltage control subcircuit and the target area; When a preset voltage is detected at the detection end, a feedback network is formed between the reference end of the overvoltage control subcircuit and the target area, so that the voltage obtained by the detection end of the overvoltage protection subcircuit is reduced.

7. The circuit according to claim 1, characterized in that The overvoltage protection circuit also includes an overvoltage compensation subcircuit; The input end of the overvoltage compensation subcircuit is interconnected with the reference end of the overvoltage control subcircuit and the target area, and the output end of the overvoltage compensation subcircuit is interconnected with the input end and the output end of the overvoltage control subcircuit, and is used to slow down the voltage rising speed when the input end voltage of the overvoltage control subcircuit increases, and to slow down the voltage falling speed when the output end voltage of the overvoltage control subcircuit decreases.

8. Over-voltage and under-voltage protection circuit, characterized in that: include: Three-terminal adjustable shunt shunt regulator Q1, voltage regulator D5, transistor Q2, three-terminal adjustable shunt shunt regulator Q6, voltage regulator D7, transistor Q4, transistor Q5; The reference end of the three-terminal adjustable shunt shunt regulator Q1 is connected to the target area, the input end is connected to the cathode of the voltage regulator tube D5 and the external high level, and the output end is grounded; The output end of the voltage regulator tube D5 is connected to the base of the transistor Q2; The transmitting stage of the transistor Q2 is connected to the first pin, and the collector stage is grounded; The reference end of the three-terminal adjustable shunt shunt regulator Q6 is connected to the target area, the input end is connected to the cathode of the voltage regulator tube D7, and the external high level is interconnected, and the output end is grounded; The output end of the voltage regulator tube D7 is connected to the base of the Darlington tube composed of the transistor Q4 and the transistor Q5; The sending stage of the Darlington tube is connected to an external high level, and the collector stage of the Darlington tube is connected to the second pin.

9. Over-voltage and under-voltage protection circuit, characterized in that: include: Resistor R1, resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R17, resistor R18, resistor R19, rectifier diode D1, rectifier diode D2, rectifier diode D3, rectifier diode D4, rectifier diode D6, voltage regulator D5, voltage regulator D7, voltage regulator D8, capacitor C1, capacitor C2, capacitor C3, capacitor C4, capacitor C5, capacitor C6, capacitor C7, three-terminal adjustable shunt parallel regulator Q1, three-terminal adjustable shunt parallel regulator Q6, transistor Q2, transistor Q3, transistor Q4, transistor Q5, MOS tube Q7; The anode of the rectifier diode D1 and the anode of the rectifier diode D3 are both connected to the target area, the cathode of the rectifier diode D1 and the cathode of the rectifier diode D3 are both grounded through the capacitor C2, and are connected to the anode of the rectifier diode D4 through the resistor R1, the resistor R2, and the resistor R3 connected in series in sequence; The cathode of the rectifier diode D4 is interconnected with the first end of the resistor R7, the first end of the capacitor C3, and the first end of the resistor R13; The second end of the resistor R7 is interconnected with the first end of the resistor R9, the first end of the resistor R10, the first end of the capacitor C4, the first end of the capacitor C1, and the reference end of the three-terminal adjustable shunt shunt regulator Q1; The input end of the three-terminal adjustable shunt shunt regulator Q1, the second end of the capacitor C1, the first end of the resistor R4, and the cathode of the voltage regulator D5 are interconnected, and the output end of the three-terminal adjustable shunt shunt regulator Q1 is grounded; The second end of the resistor R4 is connected to the cathode of the rectifier diode D2; The anode of the rectifier diode D2 is connected to an external high level; The anode of the voltage regulator tube D5 is connected to the first end of the resistor R5; The second end of the resistor R5 is interconnected with the first end of the resistor R8, the base of the transistor Q2, and the base of the transistor Q3; The emitter of the transistor Q2 is connected to the first pin of the chip through the resistor R6, and the collector of the transistor Q2 is grounded; The emitter of the transistor Q3 is connected to the second end of the resistor R10, and the collector of the transistor Q3 is grounded; The second end of the resistor R13 is connected to the first end of the resistor R16, the first end of the resistor R17, the first end of the capacitor C5, the first end of the capacitor C6, and the reference end of the three-terminal adjustable shunt shunt regulator Q6; The second end of the resistor R16 and the second end of the capacitor C6 are grounded; The input end of the three-terminal adjustable shunt shunt regulator Q6 is interconnected with the second end of the capacitor C5, the first end of the resistor R12, and the cathode of the voltage regulator D7; the output end of the three-terminal adjustable shunt shunt regulator Q6 is grounded; The second end of the resistor R12 is connected to the cathode of the rectifier diode D6; The anode of the rectifier diode D6 is connected to an external high level; The anode of the voltage regulator tube D7 is connected to the first end of the resistor R14; The second end of the resistor R14 is connected to the base of the Darlington transistor composed of the transistor Q4 and the transistor Q5 and the first end of the resistor R15; The emitter of the Darlington tube is connected to an external high level through the resistor R11, and the collector of the transistor Q4 is interconnected with the first end of the capacitor C7, the second end of the resistor R15, the first end of the resistor R18, the cathode of the voltage regulator tube D8, and the second pin of the chip; The second end of the capacitor C7, the anode of the voltage regulator tube D8 and the gate of the MOS tube Q7 are connected; The source of the MOS tube Q7 is connected to the second end of the resistor R17; The second end of the resistor R18 is grounded through the resistor R19; the second end of the resistor R18 is connected to the drain of the MOS transistor Q7.

Images