Direct current over / under voltage protection circuit

Abstract

The direct current over-voltage and under-voltage protection circuit monitors the input voltage state through the parallel connection of the under-voltage detection and over-voltage detection modules, the output signals commonly drive the buffer control output module, the output on-off control is realized through the control node, and the overall safety of the system is improved. Moreover, the buffer control module introduces the voltage stabilizing diode and the capacitor to form a buffer delay unit, prevents the output malfunction caused by the sudden change of the load or the power supply noise, and enhances the reliability of the system in the harsh environment such as the industrial grade.

Description

Technical Field

[0001] This utility model relates to the field of protection circuit technology, and in particular to a DC over / under voltage protection circuit. Background Technology

[0002] With the miniaturization of electronic devices and the increasing demands for power supply reliability, various circuit systems are placing higher requirements on the stability of the input voltage. In practical applications, DC power supplies may be affected by external factors, such as power supply fluctuations, reverse polarity, and sudden surges, leading to abnormal undervoltage or overvoltage conditions at the input voltage. This can cause circuit malfunctions, component damage, or even complete system failure. Therefore, designing a protection circuit capable of effectively detecting overvoltage and undervoltage in DC power supplies and achieving accurate and reliable output control is of great significance.

[0003] Existing over- and under-voltage protection schemes mostly use comparator chips, power management chips, or microcontrollers in conjunction with analog-to-digital conversion circuits to complete detection and control. However, such schemes generally have problems such as complex peripheral circuits, high cost, large power consumption, limited size, and weak anti-interference ability, which makes them difficult to promote effectively, especially in scenarios where size and cost are sensitive.

[0004] In summary, the problems existing in the current technology urgently need to be solved. Utility Model Content

[0005] This invention provides a DC over / under voltage protection circuit to overcome the deficiencies in the prior art and realize voltage monitoring and control output.

[0006] This utility model provides a DC over / under voltage protection circuit, including: Input protection module, undervoltage detection module, overvoltage detection module, buffer control output module; The input protection module has its input terminal connected to the output terminal of the DC power supply, and is used for reverse connection protection, overcurrent protection and surge suppression of the input voltage; The undervoltage detection module has its input terminal connected to the output terminal of the input protection module, and is used to determine whether the input voltage is lower than a preset undervoltage threshold. The overvoltage detection module has its input terminal connected to the output terminal of the input protection module, and is used to determine whether the input voltage is higher than a preset overvoltage threshold. The buffer control output module has its input terminal connected to the output terminals of the undervoltage detection module and the overvoltage detection module, and is used to control the output or shutdown of DC voltage according to the output signals of the undervoltage detection module and the overvoltage detection module.

[0007] According to the present invention, a DC over / under voltage protection circuit is provided, wherein the input protection module includes a socket, a first diode, a self-resetting fuse, and a second diode; The socket is a voltage input interface. The first pin of the socket is connected to the positive terminal of the first diode, and the second pin of the socket is connected to the negative terminal of the DC power supply. The negative terminal of the first diode is connected to one end of the resettable fuse; The other end of the self-resetting fuse is connected to one end of the second diode; The other end of the second diode is connected to the negative terminal of the DC power supply, and the second diode is connected in parallel with the DC power supply. in: The first diode is used to prevent damage to the circuit when the power supply is reversed; The self-resetting fuse is used to automatically disconnect when the current exceeds a preset current threshold for overcurrent protection. The second diode is used to suppress external instantaneous high voltage spikes for surge voltage protection.

[0008] According to the present invention, a DC over / under voltage protection circuit is provided, wherein the undervoltage detection module includes resistors R1, R12, R2, R5, and R9, a voltage regulator U2, a PNP transistor Q5, an NPN transistor Q3, and a Zener diode DZ1. The resistor R1 and the resistor R12 are connected in series and then in parallel across the DC power supply. The resistor R12 is connected to the first pin of the voltage regulator U2. The third pin of the voltage regulator U2 is connected to the negative terminal of the power supply, and the second pin is connected to the output terminal of the DC power supply through the resistor R2, and at the same time connected to the base of the PNP transistor Q5 through the resistor R9. The emitter of the PNP transistor Q5 is connected to the DC power supply through the resistor R5, and the collector of the PNP transistor Q5 is connected to the negative terminal of the DC power supply. The emitter of the PNP transistor Q5 is also connected to the base of the NPN transistor Q3 through a reverse-parallel Zener diode DZ1. The emitter of the NPN transistor Q3 is connected to the negative terminal of the DC power supply, and the collector of the PNP transistor Q5 is connected to the control node of the buffer control output module.

[0009] According to the present invention, a DC over / under voltage protection circuit is provided, wherein the overvoltage detection module includes resistors R3, R13, R4, and R8, a voltage regulator U1, and a PNP transistor Q2. The resistor R3 and the resistor R13 are connected in series and then in parallel across the DC power supply. The resistor R13 is connected to the first pin of the voltage regulator U1. The third pin of the voltage regulator U1 is connected to the negative terminal of the DC power supply; The second pin of the voltage regulator U1 is connected to the DC power supply through the resistor R4, and is connected to the base of the PNP transistor Q2 through the resistor R8; The emitter of the PNP transistor Q2 is connected to the control node of the buffer control output module, and the collector is connected to the negative terminal of the power supply.

[0010] According to the DC over / under voltage protection circuit provided by this utility model, the buffer control output module includes a control node, a Zener diode DZ2, a capacitor EC3, resistors R6, R7, and R10, a transistor Q4, and a P-type field-effect transistor Q1, wherein: One end of the resistor R6 is connected to the DC power supply, and the other end, together with the negative terminal of the Zener diode DZ2 and the positive terminal of the capacitor EC3, is connected to the control node. The negative terminal of the capacitor EC3 is connected to the negative terminal of the DC power supply, and the positive terminal of the Zener diode DZ2 is connected to the base of the transistor Q4. The emitter of transistor Q4 is connected to the negative terminal of the DC power supply, and the collector of transistor Q4 is connected to the gate of P-type field-effect transistor Q1 through resistor R10. The source of the P-type field-effect transistor Q1 is connected to the DC power supply, and its drain is the output terminal. The drain is also grounded through the filter capacitor EC1. One end of the resistor R7 is connected to the DC power supply, and the other end is connected to the gate of the P-type field-effect transistor Q1.

[0011] According to the DC over / under voltage protection circuit provided by this utility model, the control node of the buffer control output module is jointly determined by the output signal of the undervoltage detection module and the output signal of the overvoltage detection module; When the output signal of the undervoltage detection module or the output signal of the overvoltage detection module is low, the voltage of the control node is pulled low to shut off the output.

[0012] According to the DC over / under voltage protection circuit provided by this utility model, both voltage regulator U1 and voltage regulator U2 are TL431 precision voltage regulator chips.

[0013] According to the DC over / under voltage protection circuit provided by this utility model, the buffer control output module is provided with a filter delay capacitor EC3, which is used to provide voltage buffer when the input voltage changes.

[0014] According to the DC over / under voltage protection circuit provided by this utility model, the P-type field-effect transistor Q1 is an enhancement-mode MOSFET device, and its gate drive voltage is controlled by a voltage-limiting divider network to improve the stability and response speed of the conduction control.

[0015] According to the DC over / under voltage protection circuit provided by this utility model, the first diode of the input protection module is a Schottky diode to reduce the forward voltage drop.

[0016] The DC over / under voltage protection circuit provided by this utility model monitors the input voltage status through parallel connection of undervoltage and overvoltage detection modules. The output signals jointly drive the buffer control output module, and the output on / off control is realized through the control node, thereby improving the overall system safety. Furthermore, the buffer control module incorporates a Zener diode and a capacitor to form a buffer delay unit, preventing output malfunctions caused by sudden load changes or power supply noise, and enhancing the system's reliability in harsh environments such as industrial settings. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this utility model. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the DC over / under voltage protection circuit provided by this utility model; Figure 2 This is a circuit diagram of the input protection module provided by this utility model; Figure 3 This is a circuit diagram of the undervoltage detection module provided by this utility model; Figure 4 This is a circuit diagram of the overvoltage detection module provided by this utility model; Figure 5 This is a circuit diagram of the buffer control output module provided by this utility model; Figure 6 This is a circuit diagram of the DC over / under voltage protection circuit provided by this utility model. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this utility model.

[0020] To address the problems in the existing technology, this utility model proposes a DC over / under voltage protection circuit to achieve voltage monitoring and control output. The DC over / under voltage protection circuit is described below, as follows: Figure 1 As shown, including but not limited to the following modules: Input protection module, undervoltage detection module, overvoltage detection module, and buffer control output module; The input protection module has its input terminal connected to the output terminal of the DC power supply, and is used for reverse connection protection, overcurrent protection and surge suppression of the input voltage; The undervoltage detection module has its input terminal connected to the output terminal of the input protection module, and is used to determine whether the input voltage is lower than a preset undervoltage threshold. The overvoltage detection module has its input terminal connected to the output terminal of the input protection module, and is used to determine whether the input voltage is higher than a preset overvoltage threshold. The buffer control output module has its input terminal connected to the output terminals of the undervoltage detection module and the overvoltage detection module, and is used to control the output or shutdown of DC voltage according to the output signals of the undervoltage detection module and the overvoltage detection module.

[0021] The input protection module is used to provide reverse polarity protection, overcurrent protection, and surge voltage suppression when a DC power input voltage is connected to the circuit. The module includes: a socket J1, serving as the DC voltage input interface, with its first pin connected to the positive terminal and its second pin connected to the negative terminal; a diode D2, with its positive terminal connected to the first pin of socket J1 and its negative terminal connected to a resettable fuse F1; the other end of the resettable fuse F1 is connected to one end of a TVS diode D1, and the other end of the TVS diode is connected to the negative terminal of the power supply.

[0022] Among them: diode D2 is used to prevent the input power supply polarity from being reversed; self-resetting fuse F1 is used to automatically disconnect the circuit in case of overcurrent; TVS diode D1 is connected in parallel with the input power supply to absorb high-energy surges and suppress peak voltages.

[0023] The above structure enables multiple protections for the input voltage, improving overall stability and reliability.

[0024] The undervoltage detection module is used to determine whether the input voltage is lower than the set undervoltage threshold. Its core component is the TL431 precision voltage regulator U2. This module mainly includes: Resistors R1 and R12 are connected in series and then in parallel across the input power supply VI. R12 intermediate node is connected to pin 1 (reference terminal) of TL431. Pin 3 of the TL431 is connected to the negative power supply, and pin 2 is connected to VI through resistor R2, and at the same time connected to the base of the PNP transistor Q5 through resistor R9. The emitter of Q5 is connected to VI through resistor R5, and the collector is connected to the negative terminal of the power supply. The emitter of Q5 is also connected in reverse parallel to the base of NPN transistor Q3 through Zener diode DZ1; The emitter of Q3 is grounded, and the collector is connected to the control node K of the buffer control output module.

[0025] Its working principle is as follows: By adjusting the ratio of the voltage divider resistors R1 and R12, the voltage at the R12 terminal is 2.5V when VI = VImin (undervoltage threshold). When the input voltage is lower than VImin, TL431 is not turned on, its pin 2 remains at a high level, PNP transistor Q5 is cut off, Zener diode DZ1 is turned on, and driver Q3 is turned on, pulling point K low. When the input voltage is higher than VImin, TL431 is turned on, PNP transistor Q5 is turned on, DZ1 is not turned on, Q3 is turned off, and the voltage at point K remains high.

[0026] The overvoltage detection module has a similar structure to the undervoltage detection module, also using the TL431 voltage regulator U1 as its core to determine whether the input voltage exceeds the overvoltage threshold. This module includes: Resistors R3 and R13 are connected in series and then in parallel to the input voltage VI; Connect the midpoint of R13 to pin 1 of TL431; Pin 3 of the TL431 is grounded, and pin 2 is connected to VI through resistor R4, and at the same time connected to the base of PNP transistor Q2 through resistor R8. The emitter of Q2 is connected to point K of the buffer control output module, and the collector is grounded.

[0027] The working principle is as follows: When the input voltage is less than VImax, TL431 is not turned on, Q2 is cut off, and point K remains at a high level. When the input voltage is higher than VImax, TL431 turns on, the voltage at pin 2 drops, driving Q2 to turn on, and point K is pulled down to about 0.3V.

[0028] The buffer control output module is used to control the output switching based on the voltage at point K, and has a buffer delay function to prevent false triggering. This module includes: Resistor R6, capacitor EC3 and Zener diode DZ2 form a K-point buffer circuit. R6 is connected to VI, and the other end is connected to the negative terminal of DZ2 and the positive terminal of EC3. The common point of the three is point K. The positive terminal of DZ2 is connected to the base of transistor Q4, the emitter of Q4 is grounded, and the collector is connected to the gate of P-type MOSFET Q1 through resistor R10. The source of Q1 is connected to the input voltage VI, the drain is the voltage output terminal VO, and the drain is also grounded through the filter capacitor EC1. Resistor R7 is connected between the gates of VI and Q1.

[0029] Its working logic is as follows: When the voltage at point K rises and exceeds the threshold of Zener diode DZ2 (e.g., 5.1V), DZ2 turns on, driving Q4 to turn on. After Q4 is turned on, the gate of MOSFET Q1 is pulled low to form a negative voltage, Q1 is turned on, and the output terminal VO obtains the input voltage. When the voltage at point K is pulled low by the preceding stage, DZ2 is cut off, Q4 is not turned on, the gate of Q1 is pulled up to VI by R7, Q1 is cut off, and VO is de-energized.

[0030] In summary, this invention achieves reliable control of the output voltage through bidirectional overvoltage and undervoltage detection of the input voltage, combined with a buffer drive. It has advantages such as simple structure, high precision, fast response, and strong anti-interference.

[0031] As a further optional embodiment, the input protection module includes a socket, a first diode, a resettable fuse, and a second diode; The socket is a voltage input interface. The first pin of the socket is connected to the positive terminal of the first diode, and the second pin of the socket is connected to the negative terminal of the DC power supply. The negative terminal of the first diode is connected to one end of the resettable fuse; The other end of the self-resetting fuse is connected to one end of the second diode; The other end of the second diode is connected to the negative terminal of the DC power supply, and the second diode is connected in parallel with the DC power supply. in: The first diode is used to prevent damage to the circuit when the power supply is reversed; The self-resetting fuse is used to automatically disconnect when the current exceeds a preset current threshold for overcurrent protection. The second diode is used to suppress external instantaneous high voltage spikes for surge voltage protection.

[0032] In further alternative implementations, such as Figure 2 As shown, the input protection module includes a socket J1, a first diode D2, a resettable fuse F1, and a second diode D1 (a TVS diode). Wherein: Socket J1 serves as a voltage input interface, with its first pin connected to the positive terminal of the first diode D2 and its second pin connected to the negative terminal of the DC power supply. The negative terminal of the first diode D2 is connected to one end of the resettable fuse F1; The other end of the resettable fuse F1 is connected to one end of the second diode D1; The other end of the second diode D1 is connected to the negative terminal of the DC power supply.

[0033] The second diode D1 (TVS transistor) is connected in parallel with the input power supply VI.

[0034] In this embodiment: The first diode D2 is used to provide reverse polarity protection to prevent circuit damage caused by the user connecting the power supply in the wrong direction; The self-resetting fuse F1 will automatically disconnect when the circuit input current exceeds a set threshold, thereby achieving overcurrent protection; TVS diode D1 (second diode) is used to absorb instantaneous high voltage spikes at the input terminal, effectively suppressing the impact of surge voltage on subsequent circuits.

[0035] With the above structure, the input protection module can achieve multi-level protection of input voltage, provide stable and reliable operating voltage for subsequent circuits, and improve the safety and anti-interference capability of the entire system.

[0036] As a further optional embodiment, the undervoltage detection module includes resistors R1, R12, R2, R5, and R9, a voltage regulator U2, a PNP transistor Q5, an NPN transistor Q3, and a Zener diode DZ1. The resistor R1 and the resistor R12 are connected in series and then in parallel across the DC power supply. The resistor R12 is connected to the first pin of the voltage regulator U2. The third pin of the voltage regulator U2 is connected to the negative terminal of the power supply, and the second pin is connected to the output terminal of the DC power supply through the resistor R2, and at the same time connected to the base of the PNP transistor Q5 through the resistor R9. The emitter of the PNP transistor Q5 is connected to the DC power supply through the resistor R5, and the collector of the PNP transistor Q5 is connected to the negative terminal of the DC power supply. The emitter of the PNP transistor Q5 is also connected to the base of the NPN transistor Q3 through a reverse-parallel Zener diode DZ1. The emitter of the NPN transistor Q3 is connected to the negative terminal of the DC power supply, and the collector of the PNP transistor Q5 is connected to the control node of the buffer control output module.

[0037] In further alternative implementations, such as Figure 3 As shown, the undervoltage detection module includes: resistors R1, R12, R2, R5, and R9; voltage regulator U2 (a TL431 precision reference voltage regulator); PNP transistor Q5; NPN transistor Q3; and Zener diode DZ1.

[0038] Specifically: Resistor R1 and resistor R12 are connected in series and then in parallel between the positive and negative terminals of the input DC power supply; The node of resistor R12 is connected to the first pin (ref) of regulator U2. The third pin (cathode) of voltage regulator U2 is connected to the negative terminal of the power supply; The second pin (anode) of U2 is connected to the positive terminal of the DC power supply through resistor R2, and is also connected to the base of PNP transistor Q5 through resistor R9; The emitter of Q5 is connected to the positive terminal of the DC power supply through resistor R5, and its collector is connected to the negative terminal of the power supply. The emitter of Q5 is also connected to the base of NPN transistor Q3 through Zener diode DZ1 (in reverse parallel); The emitter of Q3 is connected to the negative terminal of the power supply, and the collector is connected to the control node (point K) of the buffer control output module.

[0039] The working principle of this module is as follows: The input voltage is sampled to the reference terminal of the TL431 through a voltage divider network formed by resistors R1 and R12; When the input voltage is lower than the preset undervoltage threshold, the TL431 is in the off state, and its second pin remains at a high level, causing Q5 to be off. When Q5 is off, its emitter voltage increases, the reverse parallel Zener diode DZ1 breaks down, driving Q3 to conduct, which in turn pulls down the voltage at point K. When the input voltage is higher than the undervoltage threshold, TL431 is turned on, its second pin is pulled low, Q5 is turned on, causing DZ1 to turn off, Q3 remains off, and the voltage at point K remains high.

[0040] The circuit structure described above enables accurate judgment of the undervoltage state of the input voltage, and the corresponding level signal is output through the control node K to control the on / off state of the subsequent output. It has the advantages of simple structure, fast response and high accuracy.

[0041] As a further optional embodiment, the overvoltage detection module includes resistors R3, R13, R4, and R8, a voltage regulator U1, and a PNP transistor Q2. The resistor R3 and the resistor R13 are connected in series and then in parallel across the DC power supply. The resistor R13 is connected to the first pin of the voltage regulator U1. The third pin of the voltage regulator U1 is connected to the negative terminal of the DC power supply; The second pin of the voltage regulator U1 is connected to the DC power supply through the resistor R4, and is connected to the base of the PNP transistor Q2 through the resistor R8; The emitter of the PNP transistor Q2 is connected to the control node of the buffer control output module, and the collector is connected to the negative terminal of the power supply.

[0042] In further alternative implementations, such as Figure 4 As shown, the overvoltage detection module includes: resistors R3, R13, R4, and R8, a voltage regulator U1 (preferably a TL431 precision voltage regulator), and a PNP transistor Q2.

[0043] The specific structure is as follows: Resistor R3 and resistor R13 are connected in series and then in parallel between the input terminal and the negative terminal of the DC power supply to sample the input voltage. The connection node of resistor R13 is connected to the first pin (Ref reference terminal) of voltage regulator U1. The third pin (cathode) of voltage regulator U1 is connected to the negative terminal of the power supply; The second pin (anode) of the voltage regulator U1 is connected to the positive terminal of the input power supply through resistor R4, and is also connected to the base of the PNP transistor Q2 through resistor R8; The emitter of Q2 is connected to the control node (K point) of the buffer control output module, and its collector is connected to the negative terminal of the power supply.

[0044] The working principle of this overpressure detection module is as follows: When the input voltage is lower than the preset overvoltage threshold, the voltage divider on resistor R13 is insufficient to turn on U1, the potential of the second pin of U1 remains high, the PNP transistor Q2 is cut off, and point K remains at a high potential. When the input voltage is higher than the set overvoltage action threshold, the voltage divider on resistor R13 causes the reference terminal voltage of U1 to reach 2.5V, U1 turns on, and the potential of its second pin is pulled low. At this time, PNP transistor Q2 is turned on, and control node K is pulled to a low level, thereby enabling the buffer control output module to achieve power-off control.

[0045] With the above circuit structure, the overvoltage detection module can accurately sense whether the input voltage exceeds the allowable range and send a disconnect signal to the output control module in real time, thereby effectively protecting the downstream circuits and ensuring the safety and stability of the system operation.

[0046] As a further optional embodiment, the buffer control output module includes a control node, a Zener diode DZ2, a capacitor EC3, resistors R6, R7, and R10, a transistor Q4, and a P-type field-effect transistor Q1, wherein: One end of the resistor R6 is connected to the DC power supply, and the other end, together with the negative terminal of the Zener diode DZ2 and the positive terminal of the capacitor EC3, is connected to the control node. The negative terminal of the capacitor EC3 is connected to the negative terminal of the DC power supply, and the positive terminal of the Zener diode DZ2 is connected to the base of the transistor Q4. The emitter of transistor Q4 is connected to the negative terminal of the DC power supply, and the collector of transistor Q4 is connected to the gate of P-type field-effect transistor Q1 through resistor R10. The source of the P-type field-effect transistor Q1 is connected to the DC power supply, and its drain is the output terminal. The drain is also grounded through the filter capacitor EC1. One end of the resistor R7 is connected to the DC power supply, and the other end is connected to the gate of the P-type field-effect transistor Q1.

[0047] In further alternative implementations, such as Figure 5 As shown, the buffer control output module includes: a control node (point K), a Zener diode DZ2, a capacitor EC3, resistors R6, R7, and R10, a transistor Q4, and a P-type field-effect transistor Q1.

[0048] The specific structure is as follows: One end of resistor R6 is connected to the input DC power supply, and the other end is connected to the negative terminal of Zener diode DZ2 and the positive terminal of capacitor EC3, forming control node K. The negative terminal of capacitor EC3 is connected to the negative terminal of the power supply; The positive terminal of the Zener diode DZ2 is connected to the base of the transistor Q4; The emitter of transistor Q4 is connected to the negative terminal of the power supply, and the collector is connected to the gate of P-type field-effect transistor Q1 through resistor R10. The source of Q1 is connected to the input voltage VI, and its drain serves as the voltage output terminal VO. It is also connected to ground (the negative terminal of the power supply) through the filter capacitor EC1. One end of resistor R7 is connected to the input power supply, and the other end is connected to the gate of Q1.

[0049] Its working principle is as follows: Control node K receives level signals from the undervoltage detection module and the overvoltage detection module; When the voltage at point K is higher than the Zener diode DZ2's Zener voltage (e.g., 5.1V), DZ2 turns on, giving the base of Q4 a turn-on voltage. After Q4 turns on, it pulls down the gate voltage of Q1. Under the pull-up effect of resistor R7, Q1 was originally in the off state. After Q4 turned on and pulled down the gate voltage, the P-type field-effect transistor Q1 turned on, and the input voltage was output from its source to the VO terminal through its drain. In addition, the charging and discharging characteristics of capacitor EC3 can achieve a delay buffering effect, avoiding output malfunctions caused by voltage fluctuations; When the voltage at point K is lower than the voltage regulation threshold, DZ2 is cut off, Q4 is also cut off, and the gate of Q1 is pulled up to a high potential through R7, keeping it in the off state and cutting off the output voltage.

[0050] This module effectively achieves reliable control over the output switching through a combination of transistors and MOSFETs, as well as a buffer delay circuit, avoiding instability caused by voltage surges. It is particularly suitable for use in heavy-load or high-reliability applications.

[0051] As a further optional embodiment, such as Figure 6 As shown, the control node of the buffer control output module is jointly determined by the output signal of the undervoltage detection module and the output signal of the overvoltage detection module; When the output signal of the undervoltage detection module or the output signal of the overvoltage detection module is low, the voltage of the control node is pulled low to shut off the output.

[0052] In a further optional embodiment, the voltage of the control node (i.e., point K) of the buffer control output module is jointly determined by the output signals of the undervoltage detection module and the overvoltage detection module.

[0053] Specifically: The output terminals of the undervoltage detection module and the overvoltage detection module are respectively connected to control node K. When the input voltage is within the normal range, the outputs of both modules are high, point K maintains a high voltage, and the buffer control output module is able to conduct normally. When the input voltage is lower than the undervoltage threshold or higher than the overvoltage threshold, any detection module outputs a low-level signal to point K, causing the voltage at point K to be pulled low. Since the voltage at point K is lower than the conduction threshold of the Zener diode DZ2, DZ2 is turned off, and the transistor Q4 cannot conduct. Consequently, the gate of the P-type field-effect transistor Q1 is pulled up to a high level, Q1 is turned off, and the output voltage is cut off.

[0054] It can be seen that the K-point potential enables joint judgment and control of overvoltage and undervoltage abnormal states. Voltage output is only allowed when the input voltage is within the set threshold range, thereby improving the operational safety and robustness of the entire system.

[0055] According to the DC over / under voltage protection circuit provided by this utility model, both voltage regulator U1 and voltage regulator U2 are TL431 precision voltage regulator chips.

[0056] According to the DC over / under voltage protection circuit provided by this utility model, the buffer control output module is provided with a filter delay capacitor EC3, which is used to provide voltage buffer when the input voltage changes.

[0057] According to the DC over / under voltage protection circuit provided by this utility model, the P-type field-effect transistor Q1 is an enhancement-mode MOSFET device, and its gate drive voltage is controlled by a voltage-limiting divider network to improve the stability and response speed of the conduction control.

[0058] According to the DC over / under voltage protection circuit provided by this utility model, the first diode of the input protection module is a Schottky diode to reduce the forward voltage drop.

[0059] In this embodiment, a DC over / under voltage protection circuit includes an input protection module, an undervoltage detection module, an overvoltage detection module, and a buffer control output module. Wherein: The input protection module receives the output of the DC power supply and provides reverse connection protection, overcurrent protection, and surge suppression. Preferably, the first diode is a Schottky diode, which has a low forward voltage drop, helping to reduce energy loss and improve overall efficiency. When the user accidentally reverses the power supply polarity, the Schottky diode can quickly cut off, preventing circuit damage.

[0060] The undervoltage detection module and overvoltage detection module are used to detect whether the input voltage is lower than the undervoltage threshold or higher than the overvoltage threshold, respectively. High-precision threshold settings are achieved using TL431 precision adjustable voltage regulators U2 and U1. The TL431 has good temperature stability and linear adjustment characteristics, and the voltage judgment point can be precisely set through external voltage divider resistors, thereby improving the accuracy and stability of undervoltage and overvoltage detection.

[0061] The buffer control output module is used to control the on / off state of the output based on the output signal from the aforementioned detection module. This module includes a filter delay capacitor EC3, which buffers voltage fluctuations during sudden changes in the power input voltage, delaying the rate of voltage change at control node K, thereby effectively suppressing false triggering caused by interference pulses. This buffering mechanism enhances the system's anti-interference capability.

[0062] Furthermore, the P-type field-effect transistor Q1 used in the buffer control output module is an enhancement-mode MOSFET, and its gate drive voltage is controlled by a voltage divider network. Under normal operating conditions, the control node voltage increases, turning on the transistor and subsequently driving the MOSFET to conduct. By appropriately limiting the gate voltage, the stability of the MOSFET's conduction operation can be effectively improved, avoiding false turn-on or false turn-off due to voltage overshoot or interference.

[0063] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model, and not to limit it. Although this utility model has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this utility model.

Claims

1. A DC over / under voltage protection circuit, characterized in that, include: Input protection module, undervoltage detection module, overvoltage detection module, and buffer control output module; The input protection module has its input terminal connected to the output terminal of the DC power supply, and is used for reverse connection protection, overcurrent protection and surge suppression of the input voltage; The undervoltage detection module has its input terminal connected to the output terminal of the input protection module, and is used to determine whether the input voltage is lower than a preset undervoltage threshold. The overvoltage detection module has its input terminal connected to the output terminal of the input protection module, and is used to determine whether the input voltage is higher than a preset overvoltage threshold. The buffer control output module has its input terminal connected to the output terminals of the undervoltage detection module and the overvoltage detection module, and is used to control the output or shutdown of DC voltage according to the output signals of the undervoltage detection module and the overvoltage detection module.

2. The DC over / under voltage protection circuit according to claim 1, characterized in that, The input protection module includes a socket, a first diode, a resettable fuse, and a second diode. The socket is a voltage input interface. The first pin of the socket is connected to the positive terminal of the first diode, and the second pin of the socket is connected to the negative terminal of the DC power supply. The negative terminal of the first diode is connected to one end of the resettable fuse; The other end of the self-resetting fuse is connected to one end of the second diode; The other end of the second diode is connected to the negative terminal of the DC power supply, and the second diode is connected in parallel with the DC power supply. in: The first diode is used to prevent damage to the circuit when the power supply is reversed; The self-resetting fuse is used to automatically disconnect when the current exceeds a preset current threshold for overcurrent protection. The second diode is used to suppress external instantaneous high voltage spikes for surge voltage protection.

3. The DC over / under voltage protection circuit according to claim 1, characterized in that, The undervoltage detection module includes resistors R1, R12, R2, R5, and R9, a voltage regulator U2, a PNP transistor Q5, an NPN transistor Q3, and a Zener diode DZ1. The resistor R1 and the resistor R12 are connected in series and then in parallel across the DC power supply. The resistor R12 is connected to the first pin of the voltage regulator U2. The third pin of the voltage regulator U2 is connected to the negative terminal of the power supply, and the second pin is connected to the output terminal of the DC power supply through the resistor R2, and at the same time connected to the base of the PNP transistor Q5 through the resistor R9. The emitter of the PNP transistor Q5 is connected to the DC power supply through the resistor R5, and the collector of the PNP transistor Q5 is connected to the negative terminal of the DC power supply. The emitter of the PNP transistor Q5 is also connected to the base of the NPN transistor Q3 through a reverse-parallel Zener diode DZ1. The emitter of the NPN transistor Q3 is connected to the negative terminal of the DC power supply, and the collector of the PNP transistor Q5 is connected to the control node of the buffer control output module.

4. The DC over / under voltage protection circuit according to claim 3, characterized in that, The overvoltage detection module includes resistors R3, R13, R4, and R8, a voltage regulator U1, and a PNP transistor Q2. The resistor R3 and the resistor R13 are connected in series and then in parallel across the DC power supply. The resistor R13 is connected to the first pin of the voltage regulator U1. The third pin of the voltage regulator U1 is connected to the negative terminal of the DC power supply; The second pin of the voltage regulator U1 is connected to the DC power supply through the resistor R4, and is connected to the base of the PNP transistor Q2 through the resistor R8; The emitter of the PNP transistor Q2 is connected to the control node of the buffer control output module, and the collector is connected to the negative terminal of the power supply.

5. The DC over / under voltage protection circuit according to claim 1, characterized in that, The buffer control output module includes a control node, a Zener diode DZ2, a capacitor EC3, resistors R6, R7, and R10, a transistor Q4, and a P-type field-effect transistor Q1, wherein: One end of the resistor R6 is connected to the DC power supply, and the other end, together with the negative terminal of the Zener diode DZ2 and the positive terminal of the capacitor EC3, is connected to the control node. The negative terminal of the capacitor EC3 is connected to the negative terminal of the DC power supply, and the positive terminal of the Zener diode DZ2 is connected to the base of the transistor Q4. The emitter of transistor Q4 is connected to the negative terminal of the DC power supply, and the collector of transistor Q4 is connected to the gate of P-type field-effect transistor Q1 through resistor R10. The source of the P-type field-effect transistor Q1 is connected to the DC power supply, and its drain is the output terminal. The drain is also grounded through the filter capacitor EC1. One end of the resistor R7 is connected to the DC power supply, and the other end is connected to the gate of the P-type field-effect transistor Q1.

6. The DC over / under voltage protection circuit according to claim 5, characterized in that, The control node of the buffer control output module is jointly determined by the output signal of the undervoltage detection module and the output signal of the overvoltage detection module; When the output signal of the undervoltage detection module or the output signal of the overvoltage detection module is low, the voltage of the control node is pulled low to shut off the output.

7. The DC over / under voltage protection circuit according to claim 4, characterized in that, Both voltage regulators U1 and U2 are TL431 precision voltage regulator chips.

8. The DC over / under voltage protection circuit according to claim 1, characterized in that, The buffer control output module is equipped with a filter delay capacitor EC3, which is used to provide voltage buffering when the input voltage changes.

9. The DC over / under voltage protection circuit according to claim 5, characterized in that, The P-type field-effect transistor Q1 is an enhancement-mode MOSFET device, and its gate drive voltage is controlled by a voltage-limiting divider network to improve the stability and response speed of the conduction control.

10. The DC over / under voltage protection circuit according to claim 1, characterized in that, The first diode of the input protection module is a Schottky diode to reduce the forward voltage drop.

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