An intrinsically safe power supply intelligent protection circuit

Abstract

The invention discloses an intrinsically safe power supply intelligent protection circuit, comprising: a voltage stabilization and reference voltage module, which outputs a fixed reference voltage and an operating voltage; a current signal sensing module, which outputs a current detection voltage; an overcurrent signal detection module, which comprises a voltage hysteresis comparator, which determines whether a load circuit is overcurrent by comparing the fixed reference voltage and the current detection voltage, and outputs a first control signal; a short-circuit monitoring control module, which comprises a first voltage comparator and a voltage divider circuit, which outputs a variable reference voltage, and the first voltage comparator compares the variable reference voltage and the short-circuit voltage to output a second control signal; a simple OR gate circuit module, which outputs a switch signal by judging the high and low of the input first control signal and the second control signal; a contactless switch module, which controls the connection of the switch according to the switch signal, and a fault indication and short-circuit self-recovery module, which indicates the circuit working state and automatically restores power supply after the fault is eliminated.

Description

Technical Field

[0001] The present application relates to the technical field of power management in an intrinsically safe environment, and in particular to an intrinsically safe power supply intelligent protection circuit. Background Art

[0002] Intrinsically safe power supply (hereinafter referred to as intrinsically safe power supply) is one of the electrical equipments that are very necessary for use in explosive gas or dust environment. It can provide power for other intrinsically safe equipment to ensure the normal operation of these equipments. Since the intrinsically safe power supply works in the dangerous environment of explosive gas, it has many special requirements compared with the ordinary power supply. The most important one is to limit the energy released under the fault condition to a very small range, that is, to limit the discharge voltage, current and time when the circuit fails. In the specific circuit implementation, there are voltage limiting circuit, current limiting circuit, overcurrent protection circuit, overvoltage protection circuit, etc. Some equipment requires automatic power restoration after the fault is eliminated.

[0003] The core of intrinsically safe power supply is protection circuit. The commonly used power supply protection method is: add an overcurrent resistor in series to the power supply circuit, detect the current on it, and take the voltage drop on the resistor. When a short circuit fault occurs in the power supply, the current increases, and the voltage drop on the resistor in the power supply circuit string increases. After comparison by the input detection circuit, the controller is reversed, so that the field effect switch tube in the power supply circuit is switched from on to off, and the power supply of the fault circuit is cut off, thereby realizing short circuit protection. There are great shortcomings in the above method: First, the action range of the comparative potential working point will narrow with the change of input voltage. After the action voltage of the detection point is adjusted, if the input voltage and current are changed at this time, it will affect the original working point of the detector, and the detector will malfunction or not operate when the voltage changes greatly. Second, there must be a detection resistor or inductor in the circuit. The detector is sensitive and easy to adjust with a large resistance value, but the resistance value will increase due to heat and there will be a voltage drop, which will make the voltage at the load end lower. For this reason, the voltage at the input end can only be increased. If inductance detection is used, its volume is large and the cost is high. Third, the action range is too narrow when a fault occurs, because it is determined by the ratio of the detector input voltage. It is not easy to act when the ratio is large, and it is easy to malfunction when the ratio is small, which makes the stability and anti-interference ability worse. Fourth, the load capacity is small after the fault is eliminated. When the load is larger, it is not easy to start and stop the power supply, especially when the load is not easy to start automatically. Therefore, it cannot work normally when the current load is large, which brings great trouble to debugging. Fifth, in order to solve the above four shortcomings, only a more complex circuit structure can be added, which increases the production cost and greatly increases the failure rate of the whole machine. Summary of the invention

[0004] The purpose of the present invention is to provide an intrinsically safe power supply intelligent protection circuit to solve the problems raised in the above background technology. The technical solution is as follows:

[0005] An intrinsically safe power supply intelligent protection circuit, comprising:

[0006] The voltage stabilization and reference voltage module includes a voltage stabilization diode and a reference voltage circuit. The voltage stabilization diode provides a working voltage for the current signal sensing module. The reference voltage circuit outputs a fixed reference voltage and a short-circuit voltage to the overcurrent signal detection module and the short-circuit monitoring control module respectively.

[0007] A current signal sensing module, the positive and negative electrodes of which are connected in series to a load circuit powered by a power supply, and the current signal sensing module outputs a current detection voltage proportional to the current of the load circuit; an overcurrent signal detection module, including a voltage hysteresis comparator, the positive and negative input terminals of the voltage hysteresis comparator respectively input the current detection voltage and a fixed reference voltage, and judge whether the load circuit is overcurrent by comparing the fixed reference voltage and the current detection voltage, and output a corresponding first control signal; the output terminal of the voltage hysteresis comparator is electrically connected to the first input terminal of the simple OR gate circuit module;

[0008] A short-circuit monitoring control module comprises a first voltage comparator, a second voltage comparator and a voltage divider circuit, wherein the voltage divider circuit outputs a variable reference voltage, the variable reference voltage and the short-circuit voltage are respectively input to the positive and negative ends of the first voltage comparator, and the variable reference voltage and the short-circuit voltage are compared, and a second control signal is output, the output end of the first voltage comparator is electrically connected to the second input end of the simple OR gate circuit module; the short-circuit voltage and the variable reference voltage are respectively input to the positive and negative ends of the second voltage comparator, and the reference voltage and the second divided voltage are compared, and a third control signal is output, and the output end of the second voltage comparator is connected to the gate G of the NMOS tube switch;

[0009] A simple OR gate circuit module outputs a switch signal by judging the level of the input first control signal and the second control signal, and the output end of the simple OR gate circuit module is connected to the PMOS switch gate G of the contactless switch module;

[0010] The contactless switch module controls the connection state of the switch according to the input switch signal; the contactless switch module is electrically connected to the fault indication and short circuit automatic recovery module. When the PMOS tube switch of the contactless switch module is turned off, the load circuit is powered off, and the fault indication and short circuit automatic recovery module is started at the same time, and the fault indicator light of the fault indication and short circuit automatic recovery module is on.

[0011] Preferably, when the load circuit operates normally, the fixed reference voltage is greater than the current detection voltage, and the first control signal output by the voltage hysteresis comparator is a low level. When the load circuit is overcurrent, the fixed reference voltage is less than the current detection voltage, and the first control signal output by the voltage hysteresis comparator is a high level.

[0012] Preferably, when there is no short-circuit fault in the load circuit, the short-circuit voltage is greater than the variable reference voltage, the second control signal is at a low level, the third control signal is at a high level, and the NMOS tube switch is turned on; when a short-circuit fault occurs in the load circuit, the short-circuit voltage is less than the variable reference voltage, the second control signal is at a high level, the third control signal is at a low level, and the NMOS tube switch is turned off.

[0013] Preferably, in the simple OR gate circuit module, when the first input terminal and the second input terminal are both at a low level, the output switch signal is a low level; in the simple OR gate circuit module, when at least one of the first input terminal and the second input terminal is at a high level, the output switch signal is a high level.

[0014] Preferably, when the switch signal is at a low level, the PMOS tube switch of the contactless switch module is closed, the load circuit is open, and the fault indication and short-circuit automatic recovery modules connected to the contactless switch module are in an open-circuit state; when the switch signal is at a low level or a high level, the PMOS tube switch of the contactless switch module is disconnected, the load circuit is open, and the contactless switch module simultaneously starts the fault indication and short-circuit automatic recovery modules.

[0015] Preferably, the fault indication and short-circuit automatic recovery module includes a fault indicator light, a current limiting diode, a series inductor and an interconnected circuit. When the load circuit is open, the fault indication and short-circuit automatic recovery module stops working. When the load circuit is open, the fault indicator light turns on and the current limiting diode starts working to provide monitoring current for load circuit fault troubleshooting.

[0016] Preferably, when the overcurrent or short-circuit fault of the load circuit is eliminated, the current detection voltage returns to normal, the fixed reference voltage is greater than the current detection voltage, and the first control signal output by the voltage hysteresis comparator is low level; the short-circuit voltage returns to normal, the short-circuit voltage is greater than the variable reference voltage, and the second control signal is low level, and then the simple OR gate circuit module outputs a low level, the PMOS tube switch of the contactless switch module is closed, the load circuit is restored to the path, the fault indication and short-circuit automatic recovery modules stop working, and the fault indicator light goes out.

[0017] Preferably, when the load circuit is in an initial state or a normal working state, the PMOS switch of the contactless switch module is closed.

[0018] Preferably, when the NMOS switch is turned off, the load of the voltage divider circuit increases and the variable reference voltage increases.

[0019] Preferably, the short-circuit monitoring control module may be one or more, providing multiple intrinsically safe power supply protections in series or parallel.

[0020] The beneficial effects of the solution provided by the embodiment of the present application are:

[0021] In the embodiment of the present application, an intrinsically safe power supply intelligent protection circuit is provided. The protection circuit does not have a high-power resistor, and is less likely to generate heat and cause safety hazards. It only monitors the voltage of the load circuit when it is running to allow the comparator to output different levels, and finally realizes the closing and disconnection of the load circuit through the different reactions of the contactless switch to the high and low levels, thereby realizing the protection of the intrinsically safe power supply. At the same time, the contactless switch controls the load circuit to automatically resume work after the fault is eliminated, saving time. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The drawings in the specification, which constitute a part of the present application, are used to provide further understanding of the present application. The illustrative embodiments of the present application and their descriptions are used to explain the present application and do not constitute improper limitations on the present application.

[0023] in:

[0024] Figure 1 It is a basic principle diagram of an intrinsically safe power supply intelligent protection circuit provided in an embodiment of the present application;

[0025] Figure 2 It is a schematic diagram of a dual protection circuit of an intrinsically safe power supply provided in an embodiment of the present application. DETAILED DESCRIPTION

[0026] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present application includes such modifications and variations within the scope of the appended claims and their equivalents.

[0027] The present application embodiment provides an intrinsically safe power supply intelligent protection circuit, combined with Figure 1 As shown,

[0028] An intrinsically safe power supply intelligent protection circuit, comprising:

[0029] The voltage stabilization and reference voltage module includes a voltage stabilization diode and a reference voltage circuit. The voltage stabilization diode provides an operating voltage for the current signal sensing module. The reference voltage circuit provides a fixed reference voltage to the overcurrent signal detection module and the short-circuit monitoring control module, and provides a variable reference voltage to the short-circuit monitoring control module.

[0030] A current signal sensing module, the positive and negative electrodes of which are connected in series to a load circuit powered by a power supply, and the current signal sensing module outputs a current detection voltage proportional to the current of the load circuit;

[0031] The overcurrent signal detection module includes a voltage hysteresis comparator, the positive and negative input terminals of the voltage hysteresis comparator are respectively input with a current detection voltage and a fixed reference voltage, and the module determines whether the load circuit is overcurrent by comparing the fixed reference voltage and the current detection voltage, and outputs a corresponding first control signal; the output terminal of the voltage hysteresis comparator is electrically connected to the first input terminal of the simple OR gate circuit module;

[0032] A short-circuit monitoring control module comprises a first voltage comparator, a second voltage comparator and a voltage divider circuit, wherein the voltage divider circuit outputs a variable reference voltage, the variable reference voltage and the short-circuit voltage are respectively input to the positive and negative ends of the first voltage comparator, and the variable reference voltage and the short-circuit voltage are compared to output a second control signal, the output end of the first voltage comparator is electrically connected to the second input end of the simple OR gate circuit module; the short-circuit voltage and the variable reference voltage are respectively input to the positive and negative ends of the second voltage comparator, and the reference voltage and the second divided voltage are compared to output a third control signal, and the output end of the second voltage comparator is connected to the gate G of the NMOS tube switch;

[0033] A simple OR gate circuit module outputs a switch signal by judging the level of the input first control signal and the second control signal, and the output end of the simple OR gate circuit module is connected to the PMOS switch gate G of the contactless switch module;

[0034] The contactless switch module controls the connection state of the switch according to the input switch signal; the contactless switch module is electrically connected to the fault indication and short circuit automatic recovery module. When the PMOS tube switch of the contactless switch module is turned off, the load circuit is powered off, and the fault indication and short circuit automatic recovery module is started at the same time, and the fault indicator light of the fault indication and short circuit automatic recovery module is on.

[0035] like Figure 1 As shown, the voltage stabilization and reference voltage module includes a voltage stabilizing diode and a reference circuit including resistors R3 and R4. The voltage stabilizing diode provides the working voltage VDD for the current signal sensing module, and the reference circuit outputs a fixed reference voltage Uref. The value of the output fixed reference voltage Uref is adjusted by adjusting the ratio of R3 and R4. The value of Uref is positioned as the threshold of overcurrent signal detection.

[0036] The current signal sensing module, whose positive and negative electrodes are connected in series with the positive and negative electrodes of the load circuit powered by the power supply, is composed of a precise, low-bias linear current sensor and a capacitor, and can output a corresponding current detection voltage Vo proportional to the AC or DC current of the load circuit. The value of Vo changes with the change of the current in the load circuit. When the load circuit is overcurrent, the value of Vo increases.

[0037] The overcurrent signal detection module includes a voltage hysteresis comparator and a resistor connected in series. The positive and negative electrodes of the voltage hysteresis comparator are respectively connected to the current detection voltage Vo and the fixed reference voltage Uref, and the current detection voltage Vo and the fixed reference voltage Uref are judged, and the corresponding control signal Ugi is output. The output end of the voltage hysteresis comparator is connected to an input end of a simple OR gate circuit module. When the value of Vo exceeds the value of Uref, that is, the set threshold, the control signal Ugi will change.

[0038] The short-circuit monitoring control module includes two voltage comparators and a voltage divider circuit. The variable reference voltage Urth is obtained through the voltage divider circuit. The variable reference voltage Urth is connected to the positive input terminal + of the first comparator and the inverting input terminal - of the second comparator through a resistor. The short-circuit voltage ShortTest is connected to the inverting input terminal - of the first comparator and the positive input terminal + of the second comparator through a resistor, and the variable reference voltage and the short-circuit voltage are compared. The first comparator outputs a corresponding control signal Ugv, and the output terminal is electrically connected to one of the input terminals of the simple OR gate circuit module. The second voltage comparator outputs a corresponding control signal Uge, and the output terminal is connected to the gate G of the NMOS tube switch, and the NMOS tube switch is controlled to be turned on and off according to the control signal Uge.

[0039] The simple OR gate circuit module includes a double diode, a resistor and a power supply GND. The OR gate circuit performs an "OR" operation on the second control signal Ugv output by the short-circuit monitoring control module and the first control signal Ugi output by the overcurrent signal detection module. When Ugv and Ugi are both low level, the switch signal output by the simple OR gate circuit module is low level. When either Ugv or Ugi is high level, the switch signal output by the simple OR gate circuit module is high level. The output end of the simple OR gate circuit module is connected to the PMOS switch gate G of the contactless switch module. The contactless switch module is electrically connected to the fault indication and short circuit automatic recovery module. By judging the switch signal, the connection and cutoff of the PMOS tube switch of the contactless switch module are selected, thereby controlling the connection and cutoff of the load circuit. When the PMOS tube switch of the contactless switch module is cut off, the load circuit is powered off, and the fault indication and short circuit automatic recovery module are started at the same time, and the fault indicator light of the fault indication and short circuit automatic recovery module is on.

[0040] The intrinsically safe power supply intelligent protection circuit provided by the embodiment of the present application adjusts the output fixed reference voltage and the short-circuit current voltage according to the working condition of the load circuit, so that the level of the comparator output changes, and the corresponding level is output through the judgment of the simple or gate circuit module. The contactless switch module adjusts the conduction condition of the load circuit and the fault indication and the conduction condition of the short-circuit self-recovery module according to the change of the level, so as to achieve the purpose of intelligently protecting the intrinsically safe power supply. This circuit does not rely on sampling circuits and has no complex components. It drives the change of the output level through the change of voltage to achieve the purpose of controlling the load circuit.

[0041] like Figure 1 As shown, when the load circuit works normally, the fixed reference voltage Uref is greater than the current detection voltage Vo, and the first control signal Ugi output by the voltage hysteresis comparator is low level. When the load circuit is overcurrent, the fixed reference voltage Uref is less than the current detection voltage Vo, and the first control signal Ugi output by the voltage hysteresis comparator is high level. For example, the power used for mining lighting is 7.8V. VR1 is a 5V voltage regulator module inside this protection circuit. 5V provides the working voltage for the Hall current sensor, such as ACS712 or CC6904 sensor. The Hall current sensor output Vo of the current signal detection module is 1 / 2 of the sensor working voltage, that is, 2.5V, and the maximum range of the Hall current sensor is 5A; if the limit current of the overcurrent signal detection module is set to 3A, the voltage divider resistor is adjusted to set the fixed reference voltage Uref to 3.5V. When the load circuit works normally, Vo<Uref value, and the control signal Ugi output by the voltage hysteresis comparator is low level. When the load circuit is overcurrent, the Vo value output by the Hall current sensor increases to greater than 3.5V, making Vo>Uref value, and the control signal Ugi output by the voltage hysteresis comparator is high level.

[0042] like Figure 1 As shown, when there is no short-circuit fault in the load circuit, the short-circuit voltage ShortTest is greater than the variable reference voltage Urth, the second control signal Ugv is low level, the third control signal Uge is high level, the NMOS tube switch is turned on, and the load R11 is short-circuited and not connected to the voltage divider circuit; when a short-circuit fault occurs in the load circuit, the short-circuit voltage ShortTest is less than the variable reference voltage Urth, the second control signal Ugv is high level, the third control signal Uge is low level, the NMOS tube switch is turned off, the load R11 is connected to the voltage divider circuit, the load of the voltage divider circuit increases, and the variable reference voltage Urth at the input end rises, thereby keeping the output of the first voltage comparator output stable without state fluctuations, and increasing the anti-interference ability of short-circuit signal detection. The variable reference voltage output is controlled by the on and off of the NMOS tube switch.

[0043] like Figure 1As shown, the simple OR gate circuit module outputs the switch signal Switch by judging the high and low of the control signals Ugi and Ugv. The simple OR gate circuit module performs an "OR" operation. When Ugi and Ugv are both low, the output switch signal Switch is low; when the simple OR gate circuit module has at least one high input of Ugi and Ugv, the output switch signal Switch is high.

[0044] Combination Figure 1 When the switch signal Switch is at a low level, the PMOS switch of the contactless switch module is closed, the load circuit is open, and is in a normal working state. The fault indication and short circuit automatic recovery modules connected to the contactless switch module are in an open circuit state; when the switch signal Switch output by the simple OR gate circuit module is at a high level, the PMOS switch of the contactless switch module is disconnected. To protect the load circuit and power supply, the load circuit is disconnected, and the contactless switch module simultaneously starts the fault indication and short circuit automatic recovery modules.

[0045] like Figure 1 As shown, the fault indication and short-circuit automatic recovery module includes a fault indicator light, a current limiting diode, a series inductor and an interconnected circuit. When the load circuit is open, the fault indication and short-circuit automatic recovery module stops working. When the load circuit is open, the fault indicator light is on and the current limiting diode starts working to provide monitoring current for load circuit fault elimination. The fixed reference voltage Uref and the variable reference voltage Urth are both restored to normal, and the control signals Ugi and Ugv of the overcurrent detection module and the short-circuit monitoring control module output a low level, so that the contactless switch module inputs a low level, the PMOS tube switch of the contactless switch module closes, and the load circuit is restored to a pass, the fault indication and short-circuit automatic recovery module stops working, the fault indicator light is off, and it can work normally, achieving the purpose of automatically restoring power supply.

[0046] When the load circuit is in the initial state or the normal working state, the PMOS tube switch of the contactless switch module is closed.

[0047] It can be understood that when the load circuit is in the initial state, that is, it is assumed that the voltage and current of the load circuit are normal, which is consistent with the normal working state.

[0048] When the NMOS switch is turned off, the load of the voltage divider circuit increases and the variable reference voltage increases.

[0049] It can be understood that the significance of the existence of the NMOS tube switch is to control the load of the voltage divider circuit. When the NMOS tube switch is turned on, the load R11 is short-circuited. When the NMOS tube switch is turned off, the load R11 is connected to the voltage divider circuit to increase the load of the voltage divider circuit, thereby increasing the variable reference voltage Urth. The control signal Ugv output by the first comparator is more stable, thereby increasing the anti-interference ability.

[0050] The short-circuit monitoring control module can provide multiple short-circuit monitoring protection functions for one or more modules through parallel or series connection.

[0051] It is understandable that in some special intrinsically safe application environments, multiple protection circuits need to be adopted. Since short-circuit sparks are one of the most important risks of power supply and circuits, this application provides a dual protection circuit such as Figure 2 shown.

[0052] like Figure 2 As shown, Figure 2 The schematic diagram of the double protection circuit is shown in Figure 2. The second voltage comparator output terminals Ugv1 and Ugv2 of the two short-circuit monitoring control modules are respectively connected to the No. 2 input terminal of two simple OR gate circuit modules, and the overcurrent monitoring circuit output terminal Ugi is connected to the No. 1 input terminal of two simple OR gate circuit modules; the output terminals Switch1 and Switch2 of the two simple OR gate circuit modules are both connected to a contactless switch, and the double protection circuit is provided with two contactless switch modules. The specific judgment method and working principle are similar to Figure 1 The single protection circuits are the same and will not be described in detail here.

[0053] The dual protection circuit provided in this embodiment adopts dual short-circuit monitoring and control modules to respectively control different contactless switches of the circuits. When any short-circuit monitoring and control level module detects a short-circuit signal, the short-circuit monitoring and control module locks the load circuit and simultaneously starts the fault indication and short-circuit automatic recovery modules. After the fault is eliminated, the load circuit returns to normal, meeting the requirements of multiple protection levels of the intrinsically safe circuit.

[0054] The above are only preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An intrinsically safe power supply intelligent protection circuit, characterized in that: include: A voltage stabilization and reference voltage module, comprising a voltage stabilization diode and a reference voltage circuit, wherein the voltage stabilization diode provides an operating voltage for the current signal sensing module, and the reference voltage circuit provides a fixed reference voltage to the overcurrent signal detection module and a variable reference voltage to the short-circuit monitoring control module; The current signal sensing module has a positive and negative pole connected in series with a load circuit powered by a power supply, and the current signal sensing module outputs a corresponding current detection voltage proportional to the current of the load circuit; the overcurrent signal detection module includes a voltage hysteresis comparator, the positive and negative input terminals of the voltage hysteresis comparator respectively input the current detection voltage and a fixed reference voltage, and judges whether the load circuit is overcurrent by comparing the fixed reference voltage and the current detection voltage, and outputs a corresponding first control signal; the output terminal of the voltage hysteresis comparator is electrically connected to the first input terminal of the simple OR gate circuit module; The short-circuit monitoring control module comprises a first voltage comparator, a second voltage comparator and a voltage divider circuit, wherein the voltage divider circuit outputs a variable reference voltage, the variable reference voltage and the short-circuit voltage are respectively input to the positive and negative ends of the first voltage comparator, and the variable reference voltage and the short-circuit voltage are compared to output a second control signal, the output end of the first voltage comparator is electrically connected to the second input end of the simple OR gate circuit module; the short-circuit voltage and the variable reference voltage are respectively input to the positive and negative ends of the second voltage comparator, and the reference voltage and the second divided voltage are compared to output a third control signal, and the output end of the second voltage comparator is connected to the gate G of the NMOS tube switch; The simple OR gate circuit module outputs a switch signal by judging the level of the first control signal and the second control signal input, and the output end of the simple OR gate circuit module is connected to the PMOS switch gate G of the contactless switch module; The contactless switch module controls the connection state of the switch according to the input switch signal; the contactless switch module is electrically connected to the fault indication and short circuit automatic recovery module, when the PMOS tube switch of the contactless switch module is turned off, the load circuit is powered off, and the fault indication and short circuit automatic recovery module is started at the same time, and the fault indicator light of the fault indication and short circuit automatic recovery module is on; When the load circuit works normally, the fixed reference voltage is greater than the current detection voltage, and the first control signal output by the voltage hysteresis comparator is at a low level; when the load circuit is overcurrent, the fixed reference voltage is less than the current detection voltage, and the first control signal output by the voltage hysteresis comparator is at a high level; When the load circuit has no short-circuit fault, the short-circuit voltage is greater than the variable reference voltage, the second control signal is at a low level, the third control signal is at a high level, and the NMOS tube switch is turned on; when the load circuit has a short-circuit fault, the short-circuit voltage is less than the variable reference voltage, the second control signal is at a high level, the third control signal is at a low level, and the NMOS tube switch is turned off.

2. An intrinsically safe power supply intelligent protection circuit as claimed in claim 1, characterized in that: For the simple OR gate circuit module, when both the first input terminal and the second input terminal are at a low level, the switch signal output is at a low level; for the simple OR gate circuit module, when at least one of the first input terminal and the second input terminal is at a high level, the switch signal output is at a high level.

3. An intrinsically safe power supply intelligent protection circuit as claimed in claim 2, characterized in that: When the switch signal is at a low level, the PMOS tube switch of the contactless switch module is closed, the load circuit is open, and the fault indication and short circuit automatic recovery modules connected to the contactless switch module are in an open circuit state; when the switch signal is at a high level, the PMOS tube switch of the contactless switch module is disconnected, the load circuit is open, and the contactless switch module simultaneously starts the fault indication and short circuit automatic recovery modules.

4. An intrinsically safe power supply intelligent protection circuit as claimed in claim 3, characterized in that: The fault indication and short-circuit automatic recovery module includes a fault indicator light, a current limiting diode, a series inductor and an interconnected circuit. When the load circuit is open, the fault indication and short-circuit automatic recovery module stops working. When the load circuit is open, the fault indicator light turns on and the current limiting diode starts working to provide a monitoring current for troubleshooting the load circuit.

5. An intrinsically safe power supply intelligent protection circuit as claimed in claim 4, characterized in that: When the overcurrent or short circuit fault of the load circuit is eliminated, the current detection voltage returns to normal, the fixed reference voltage is greater than the current detection voltage, and the first control signal output by the voltage hysteresis comparator is low level; the short circuit voltage returns to normal, the short circuit voltage is greater than the variable reference voltage, the second control signal is low level, and then the simple OR gate circuit module outputs a low level, the PMOS tube switch of the contactless switch module is closed, the load circuit is restored to a pass, the fault indication and short circuit automatic recovery module stop working, and the fault indicator light goes out.

6. The intrinsically safe power supply intelligent protection circuit according to claim 1, characterized in that: When the load circuit is in an initial state or a normal working state, the PMOS switch of the contactless switch module is closed.

7. The intrinsically safe power supply intelligent protection circuit according to claim 1, characterized in that: When the NMOS switch is turned off, the variable reference voltage increases; when the NMOS switch is turned on, the variable reference voltage decreases.

8. The intrinsically safe power supply intelligent protection circuit according to claim 1, characterized in that: The short-circuit monitoring control module is one or more modules connected in series or in parallel to provide multiple short-circuit monitoring protection operations.

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