Overvoltage turn-off circuit

Abstract

The invention relates to the technical field of overvoltage turn-off, in particular to an overvoltage turn-off circuit which comprises a voltage division module, a voltage stabilization detection module, a switch control module and an MOS transistor Q1, the voltage division module comprises a resistor R1 and a resistor R2, the resistor R1 and the resistor R2 are connected in series, and when external input voltage is larger than a set protection point, the switch control module is switched on or off. The difference value between the voltage obtained by the resistor R1 and the resistor R2 and the external input voltage B + is larger than the starting condition of the voltage-regulator tube D1, at the moment, the external input voltage B + is input to the cathode of the voltage-regulator tube through the resistor R5, the voltage-regulator tube D1 is conducted at the moment, and therefore the voltage difference is generated between the emitting electrode E and the base electrode B of the triode Q2 to enable the triode Q2 to be conducted. When the MOS tube Q1 is turned off, the collector voltage of the triode Q2 is approximately equal to the external input voltage B + voltage, and the voltage drop between the source S and the grid G of the MOS tube Q1 disappears, so that the MOS tube is turned off, and the equipment is protected.

Description

Technical Field

[0001] The present invention relates to the technical field of turn-off overvoltage, and particularly to an overvoltage turn-off circuit. Background Art

[0002] During the use of industrial vehicles, due to harness jitter, vehicle plugging and unplugging, etc., the battery power supply circuit is prone to generate spike voltages, and this voltage is likely to exceed the allowable voltage range of the equipment. The traditional method is to absorb and filter through TVS tubes, varistors, capacitors, etc. However, when the duration of the input spike voltage is too long, it is easy to cause damage to the protection circuit.

[0003] Chinese Patent with application number CN202311421381.6 discloses a turn-off overvoltage suppression circuit for a switching device. The circuit includes: an inductor, a switching device, a transformer, and a power supply; the power supply is connected to the first port of the primary side winding of the transformer, and the power supply is used to provide a DC signal to the transformer; the first end of the switching device is connected to the second port of the primary side winding of the transformer, the second end of the switching device is connected to one end of the inductor, and the other end of the inductor is grounded; the switching device is used to convert the DC signal into an AC signal and output it from the secondary side winding of the transformer.

[0004] The main purpose of the overvoltage turn-off circuit is to detect the external input voltage. When the input voltage is greater than the set voltage threshold, the input of the external voltage is cut off, thereby protecting the equipment from high-voltage damage. In electric forklifts, when the vehicle harness jitters, hot-plugs, climbs a heavy load, or the emergency reverse button is pressed, a relatively high voltage is easily generated. This voltage is likely to cause harm to the equipment through the power supply circuit of the equipment. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an overvoltage turn-off circuit.

[0006] An overvoltage turn-off circuit of the present invention includes a voltage division module, a voltage stabilization detection module, a switch control module, and a MOS transistor Q1; The voltage division module includes a resistor R1 and a resistor R2. The resistor R1 and the resistor R2 are connected in series, and the resistor R1 and the resistor R2 are connected between an external input voltage (B+) and the ground. The resistor R1 and the resistor R2 are used to divide the input voltage. The voltage stabilization detection module includes a zener diode D1 and a resistor R5. The anode of the zener diode D1 is connected to the voltage division point of the voltage division module, and the cathode of the zener diode D1 is connected to the external input voltage (B+) through the resistor R5. The switch control module includes a triode Q2. The base of the triode Q2 is connected to the cathode of the zener diode D1, the emitter of the triode Q2 is grounded, and the collector of the triode Q2 is connected to the gate of the MOS transistor Q1. The source of the MOS transistor Q1 is connected to an external input voltage (B+), and the drain of the MOS transistor Q1 is connected to a backend device.

[0007] The external input voltage B+ is divided by resistors R1 and R2, and the divided voltage serves as the anode of the voltage regulator diode D1. The voltage protection point is set by resistors R1, R2, and the voltage regulator diode D1. When the external input voltage is greater than the set protection point, the difference between the voltage divided by resistors R1 and R2 and the external input voltage B+ is greater than the turn-on condition of the voltage regulator diode D1. At this time, the external input voltage B+ is input to the cathode of the voltage regulator diode through resistor R5. Then, the voltage regulator diode D1 conducts, generating a voltage difference between the emitter E and the base B of the triode Q2, causing the triode Q2 to conduct. The collector voltage of the triode Q2 is approximately equal to the external input voltage B+. At this time, the voltage drop between the source S and the gate G of the MOS transistor Q1 disappears, turning off the MOS transistor. D2 is a voltage regulator diode. To ensure that there is a sufficient voltage difference between the GS of the MOS transistor Q1 when the overvoltage protection point is not reached, the normal turn-on of the MOS transistor is guaranteed.

[0008] Further, when the external input voltage (B+) exceeds the preset protection point, the voltage regulator diode D1 conducts, driving the triode Q2 to conduct, causing the voltage difference between the gate and the source of the MOS transistor Q1 to disappear, thereby turning off the MOS transistor Q1 and cutting off the path between the external input voltage (B+) and the backend device.

[0009] Further, it also includes a voltage regulator diode D2. The anode of the voltage regulator diode D2 is grounded, and the cathode of the voltage regulator diode D2 is connected to the gate of the MOS transistor Q1. The voltage regulator diode D2 is used to maintain the voltage difference between the gate and the source of the MOS transistor Q1 when the overvoltage protection point is not reached, ensuring the normal turn-on of the MOS transistor Q1.

[0010] Further, the triode Q2 is an NPN-type triode, and the MOS transistor Q1 is a P-channel MOS transistor.

[0011] Further, the resistance ratio of resistors R1 and R2 in the voltage division module is determined according to a preset protection voltage threshold. The preset protection voltage threshold satisfies the following formula: V 保护点 =V D1+B+ ×(R2 / R1 + R2), where V D1 is the breakdown voltage of the voltage regulator diode D1.

[0012] Further, the resistance value range of the resistor R5 is 1 kΩ to 10 kΩ, and the resistor R5 is used to limit the current flowing through the voltage regulator diode D1.

[0013] Further, the breakdown voltage range of the voltage stabilizing diode D1 is 5V to 30V, and the specific value of the breakdown voltage of the voltage stabilizing diode D1 is adjusted according to the maximum allowable input voltage of the backend device.

[0014] Further, the breakdown voltage of the voltage stabilizing diode D2 is less than the turn-on threshold voltage of the MOS transistor Q1 to ensure that the MOS transistor is fully turned on under normal voltage.

[0015] Further, this overvoltage shutdown circuit is applied to the power supply circuit of industrial vehicles to suppress the instantaneous overvoltage generated due to harness jitter or plugging and unplugging operations.

[0016] The beneficial effects of the present invention compared with the prior art are as follows: By detecting the external input voltage, when the input voltage is greater than the set voltage threshold, the input of the external voltage is cut off, thereby protecting the device from damage caused by high voltage, and further effectively suppressing the instantaneous overvoltage generated due to harness jitter, plugging and unplugging operations, and heavy-load climbing. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is the schematic diagram of the overvoltage shutdown circuit of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0019] The overvoltage shutdown circuit of the present invention can effectively suppress the instantaneous overvoltage generated due to harness jitter, plugging and unplugging operations, and heavy-load climbing.

[0020] During vehicle driving, if the harness in the vehicle jitters, it will cause poor contact of the power cord, and poor contact of the power cord will cause voltage spikes.

[0021] When the power cord is plugged and unplugged, plugging and unplugging the power interface with electricity easily causes instantaneous high voltage.

[0022] During the process of the vehicle climbing with heavy load, the change of the motor power will cause the fluctuation of the power supply.

[0023] As Figure 1 shown, the present invention provides an overvoltage shutdown circuit, including a voltage division module, a voltage stabilization detection module, a switch control module, and a MOS transistor Q1.

[0024] The voltage division module includes a resistor R1 and a resistor R2. The resistor R1 and the resistor R2 are connected in series. The resistor R1 and the resistor R2 are connected between the external input voltage (B+) and the ground, and the resistor R1 and the resistor R2 are used for voltage division of the input voltage.

[0025] The voltage stabilization detection module includes a voltage stabilizing diode D1 and a resistor R5. The anode of the voltage stabilizing diode D1 is connected to the voltage dividing point of the voltage dividing module, and the cathode of the voltage stabilizing diode D1 is connected to the external input voltage (B+) through the resistor R5.

[0026] The switch control module includes a triode Q2. The base of the triode Q2 is connected to the cathode of the voltage stabilizing diode D1, the emitter of the triode Q2 is grounded, and the collector of the triode Q2 is connected to the gate of the MOS transistor Q1. The triode Q2 is an NPN type triode, and the MOS transistor Q1 is a P-channel MOS transistor.

[0027] The overvoltage shutdown circuit of the present invention further includes a voltage stabilizing diode D2. The anode of the voltage stabilizing diode D2 is grounded, and the cathode of the voltage stabilizing diode D2 is connected to the gate of the MOS transistor Q1. The voltage stabilizing diode D2 is used to maintain the voltage difference between the gate and the source of the MOS transistor Q1 when the overvoltage protection point is not reached, ensuring that the MOS transistor Q1 is normally turned on.

[0028] The source of the MOS transistor Q1 is connected to the external input voltage (B+), and the drain of the MOS transistor Q1 is connected to the backend device.

[0029] In the normal voltage state, the resistance ratio of the resistor R1 and the resistor R2 in the voltage dividing module is determined according to the preset protection voltage threshold. The preset protection voltage threshold satisfies the following formula: V 保护点 =V D1+B+ ×(R2 / R1 + R2), where V D1 is the breakdown voltage of the voltage stabilizing diode D1. When the input voltage is less than the protection point, the voltage dividing module is provided with a protection threshold, and the voltage division ratio of the resistor R1 and the resistor R2 is R2 / (R1 + R2) × V B+ . When the external input voltage does not exceed the protection point, the voltage V 分压 at the voltage dividing point is less than the breakdown voltage V D1 of the voltage stabilizing diode D1, and the voltage stabilizing diode D1 is in the cut-off state.

[0030] At this time, the breakdown voltage V D2 of the voltage stabilizing diode D2 is less than the turn-on threshold voltage V GS（th） of the MOS transistor Q1, the voltage stabilizing diode D2 conducts, the gate (G) is grounded through the voltage stabilizing diode D2, and the voltage difference V GS between the gate and the source (S) = V B+ - V D2 , thereby ensuring that the MOS transistor Q1 is fully turned on, and the external voltage can be normally transmitted to the backend device.

[0031] When the external input voltage (B+) exceeds the preset protection point, the voltage stabilizing diode D1 conducts and drives the triode Q2 to conduct, so that the voltage difference between the gate and the source of the MOS transistor Q1 disappears, thereby turning off the MOS transistor Q1 and cutting off the path of the external input voltage (B+) to the backend device.

[0032] The resistance value range of resistor R5 is from 1 kΩ to 10 kΩ, and resistor R5 is used to limit the current flowing through zener diode D1.

[0033] The breakdown voltage range of zener diode D1 is from 5 V to 30 V, and the specific value of the breakdown voltage of zener diode D1 is adjusted according to the maximum allowable input voltage of the backend device.

[0034] The breakdown voltage of zener diode D2 is less than the turn-on threshold voltage of MOS transistor Q1 to ensure that MOS transistor Q1 is fully turned on under normal voltage.

[0035] In the overvoltage state, when the external input voltage exceeds the protection point, the voltage at the voltage division point V 分压 is greater than V D1 , zener diode D1 breaks down and conducts. At this time, the external input voltage B+ is applied to the cathode of zener diode D1 through resistor R5 to form a current path.

[0036] After zener diode D1 conducts, the voltage at the base (B) of transistor Q2 is pulled up to be close to the external input voltage B+, the emitter (E) of transistor Q2 is grounded, and when the voltage difference V BE between the base and the emitter is greater than the conduction threshold, transistor Q2 is saturated and conducts.

[0037] After transistor Q2 conducts, the voltage at the collector (C) of transistor Q2 is pulled down to be close to the ground potential, resulting in the voltage difference V GS between the gate (G) and the source (S) of MOS transistor Q1 approaching zero, and MOS transistor turns off, cutting off the path of the external input voltage B+ to the backend device, realizing overvoltage protection.

[0038] The main functions achieved by the present invention are: the external input voltage B+ is divided by resistor R1 and resistor R2, and the divided voltage is used as the anode of zener diode D1, and the voltage protection point is set by resistor R1, resistor R2 and zener diode D1; When the external input voltage is greater than the set protection point, at this time, the difference between the voltage divided by resistor R1 and resistor R2 and the external input voltage B+ is greater than the turn-on condition of zener diode D1. At this time, the external input voltage B+ is input to the cathode of zener diode through resistor R5, then zener diode D1 conducts at this time, thereby generating a voltage difference between the emitter E and the base B of transistor Q2, so that transistor Q2 conducts, then the collector voltage of transistor Q2 is approximately equal to the external input voltage B+, and at this time, the voltage drop between the source S and the gate G of MOS transistor Q1 disappears, so that MOS transistor turns off; D2 is a zener diode. To ensure that there is enough voltage difference between GS of MOS transistor Q1 when the overvoltage protection point is not reached, to ensure the normal turn-on of MOS transistor.

[0039] Example of Key Component Parameter Design: Voltage Divider Module: Set the protection point voltage V 保护点 = 36V, and the breakdown voltage of the zener diode D1 is V D1 = 12V. Then the resistance ratio needs to satisfy: R1 / R2 = V 保护点 / V D1 - 1 = 2. Optionally, R1 = 20 kΩ and R2 = 10 kΩ can be selected.

[0040] Resistor R5: Used to limit the conduction current of D1 and prevent damage due to overcurrent. If the maximum allowable current of D1 is 10 mA, then: R5 ≥ (V B+ - V D1 ) / I D1（max） = (36V - 12V) / 10 mA = 2.4 kΩ. Practically, R5 = 3 kΩ can be selected.

[0041] Zener Diode D2: It is necessary to ensure that V D2 <V. If the turn - on threshold voltage of the MOS transistor Q1 is V GS（th） = 4V, then the breakdown voltage of the zener diode D2 can be selected as 3.3V.

[0042] The MOS transistor needs to be selected according to the maximum load current and breakdown voltage of the backend device.

[0043] For the over - voltage shutdown circuit of the present invention, its installation method, connection method or setting method are all common mechanical methods, and any implementation that can achieve its beneficial effects can be carried out.

[0044] All the technical and scientific terms used in this article have the same meaning as those commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the description of the present invention in this article are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used in this article includes any and all combinations of one or more of the related listed items.

[0045] The above is only the preferred embodiment of the present invention. It should be noted that for those of ordinary skill in the technical field, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. An overvoltage shutdown circuit, characterized in that, It includes a voltage division module, a voltage stabilization detection module, a switch control module, and a MOS transistor Q1; The voltage division module includes a resistor R1 and a resistor R2. The resistor R1 and the resistor R2 are connected in series, and the resistor R1 and the resistor R2 are connected between an external input voltage (B+) and ground; The voltage stabilization detection module includes a zener diode D1 and a resistor R5. The anode of the zener diode D1 is connected to the voltage division point of the voltage division module, and the cathode of the zener diode D1 is connected to the external input voltage (B+) through the resistor R5; The switch control module includes a triode Q2. The base of the triode Q2 is connected to the cathode of the zener diode D1. The emitter of the triode Q2 is grounded, and the collector of the triode Q2 is connected to the gate of the MOS transistor Q1; The source of the MOS transistor Q1 is connected to the external input voltage (B+), and the drain of the MOS transistor Q1 is connected to the backend device; The triode Q2 is an NPN type triode, and the MOS transistor Q1 is a P-channel MOS transistor.

2. The overvoltage shutdown circuit according to claim 1, characterized in that, It further includes a zener diode D2. The anode of the zener diode D2 is grounded, and the cathode of the zener diode D2 is connected to the gate of the MOS transistor Q1.

3. The overvoltage shutdown circuit according to claim 1, characterized in that, The resistance ratio of resistor R1 and resistor R2 in the voltage division module is determined according to a preset protection voltage threshold, and the preset protection voltage threshold satisfies the following formula: V 保护点 =V D1+B+ ×(R2 / (R1 + R2)), where V D1 is the breakdown voltage of the zener diode D1.

4. The overvoltage shutdown circuit according to claim 1, characterized in that, The resistance value range of the resistor R5 is from 1 kΩ to 10 kΩ.

5. The overvoltage shutdown circuit according to claim 1, characterized in that, The breakdown voltage range of the zener diode D1 is from 5 V to 30 V, and the breakdown voltage of the zener diode D1 is adjusted according to the maximum allowable input voltage of the backend device.

6. The overvoltage shutdown circuit according to claim 2, characterized in that, The breakdown voltage of the zener diode D2 is less than the turn-on threshold voltage of the MOS transistor Q1.

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