Self-recovery cut-off type over-current protection circuit in flame-proof and intrinsic safety type power supply

Abstract

The utility model relates to a self-recovery cut-off type over-current protection circuit in an explosion-proof and intrinsic safety type power supply. The self-recovery cut-off type over-current protection circuit comprises a current sampling resistor R1, a current limiting resistor R2, a current detection circuit, a bistable trigger circuit, a switching circuit and a voltage recovery detection circuit, the current detection circuit is connected in parallel with the resistor R1, and outputs a detection signal to the first input end of the bistable trigger circuit according to the magnitude of the current flowing through the resistor R1; the output end of the bistable trigger circuit is connected with the control end of the switching circuit; the switching circuit is connected in parallel with the resistor R2; the first input end of the voltage recovery detection circuit is connected with one end, connected with a load, of the resistor R2, the second input end of the voltage recovery detection circuit is connected with the output end of the bistable trigger circuit, and the output end of the voltage recovery detection circuit is connected with the second input end of the bistable trigger circuit. According to the scheme, the bistable trigger circuit is utilized to realize the functions of'locking 'and'automatic recovery', and the problem that a common cut-off type protection circuit needs to be manually reset is solved.

Description

Technical Field

[0001] The utility model relates to the technical field of mine power supply equipment, in particular to a self-recovery cut-off overcurrent protection circuit in a flameproof and intrinsically safe power supply. Background Art

[0002] In the design of explosion-proof and intrinsically safe power supply for mining, the cut-off overcurrent protection circuit is a commonly used power protection circuit, which is usually composed of a current detection circuit and a switch circuit. When the output current is too large or the load is short-circuited, the current detection circuit outputs a valid signal, closes the switch circuit and cuts off the current. After the current is cut off, the current detection circuit cannot detect the current and returns to normal, causing the switch circuit to turn on again. Therefore, before the fault is eliminated, the "off" and "on" processes are repeated over and over again, forming "oscillation".

[0003] In order to eliminate "oscillation", the cut-off overcurrent protection circuit usually needs to be equipped with a "locking" circuit to prevent the "oscillation" phenomenon from occurring. However, after the overcurrent fault is eliminated, the "locking" circuit needs to be manually released to restore the normal working state of the power supply. Utility Model Content

[0004] The utility model aims at the technical problems existing in the prior art and provides an overcurrent protection circuit capable of automatically restoring and cutting off. When the overcurrent fault is eliminated, the power supply can be automatically restored to a normal working state without manual restoration.

[0005] The technical solution of the utility model to solve the above technical problems is as follows:

[0006] A self-recovery cut-off overcurrent protection circuit in a flameproof and intrinsically safe power supply, comprising a current sampling resistor R1, a current limiting resistor R2, a current detection circuit, a bistable trigger circuit, a switch circuit, a voltage recovery detection circuit and a voltage stabilizing source;

[0007] One end of the current sampling resistor R1 is connected to the power supply, and the other end is connected to one end of the current limiting resistor R2; the other end of the current limiting resistor R2 is connected to the load;

[0008] The current detection circuit is connected in parallel with the current sampling resistor R1, and the current detection circuit outputs a high level or low level detection signal to the first input terminal of the bistable trigger circuit according to the magnitude of the current flowing through the current sampling resistor R1;

[0009] The output end of the bistable trigger circuit is connected to the control end of the switch circuit; the switch circuit is connected in parallel with the current limiting resistor R2;

[0010] The first input end of the voltage recovery detection circuit is connected to the other end of the current limiting resistor R2, the second input end of the voltage recovery detection circuit is connected to the output end of the bistable trigger circuit, and the output end of the voltage recovery detection circuit is connected to the second input end of the bistable trigger circuit;

[0011] The input end of the voltage stabilizing source is connected to a power supply, and the output end of the voltage stabilizing source outputs a working voltage to the bistable trigger circuit and the voltage recovery detection circuit.

[0012] Furthermore, the current detection circuit is implemented based on the AD8214ARMZ chip, the 1# pin of the AD8214ARMZ chip is connected to the power supply, the 2# pin is connected to one end of the current sampling resistor R1 through the capacitor C1, the 8# pin is connected to the other end of the current sampling resistor R1, the 5# pin outputs the detection signal, the resistor R3 is connected in series with the variable resistor RP1 and then connected in parallel with the capacitor C1, and the two ends of the resistor R5 are respectively connected to the 3# pin of the AD8214ARMZ chip and the variable resistor RP1.

[0013] Furthermore, the bistable trigger circuit is implemented based on the LMC555CM chip, the 4# and 8# pins of the LMC555CM chip are connected to a voltage regulator, the 3# pin is connected to the base of the NPN transistor V4 through a resistor R16, the collector of the NPN transistor V4 serves as the output end of the bistable trigger circuit, the 2# pin of the LMC555CM chip is connected to the collector of the NPN transistor V7 and the voltage regulator, respectively, the base of the NPN transistor V7 serves as the first output end of the bistable trigger circuit. The input end is connected to the output of the current detection circuit, the 6# pin of the LMC555CM chip is connected to the collector of the PNP transistor V3, the emitter of the PNP transistor V3 is connected to the voltage regulator, the base of the PNP transistor V3 is connected to the voltage regulator through the resistor R11, the base of the PNP transistor V3 is also connected to the collector of the NPN transistor V6 through the resistor R17, and the base of the NPN transistor V6 is connected to the output end of the voltage recovery detection circuit as the second input end of the bistable trigger circuit.

[0014] Furthermore, the switching circuit includes a switching tube V1 and an NPN transistor V2, the source of the switching tube V1 is connected to one end of the current limiting resistor R2 close to the power supply, the drain of the switching tube V1 is connected to one end of the current limiting resistor R2 close to the load, the gate of the switching tube V1 is connected to the collector of the NPN transistor V2 via the resistor R7, and the base of the NPN transistor V2 is connected to the output end of the bistable trigger circuit as the control end of the switching circuit.

[0015] Furthermore, the voltage recovery detection circuit includes a comparator and an NPN transistor V5, the positive input end of the comparator serving as the first input end of the voltage recovery detection circuit is connected to the end of the current limiting resistor R2 close to the load through a resistor R13, the positive input end of the comparator is also connected to the collector of the NPN transistor V5, the base of the NPN transistor V5 serving as the second input end of the voltage recovery detection circuit is connected to the output end of the bistable trigger circuit, the output end of the comparator serving as the output end of the voltage recovery detection circuit is connected to the second input end of the bistable trigger circuit, and the negative input end of the comparator is connected to a voltage stabilizing source.

[0016] Furthermore, the voltage stabilizing source is implemented based on a 78L05 chip, the input end of the 78L05 chip is connected to a power supply, and outputs a working voltage to the bistable trigger circuit and the voltage recovery detection circuit.

[0017] The beneficial effects of the utility model are as follows: the solution utilizes LMC555CM to form a bistable trigger circuit to realize the "locking" and "automatic recovery" functions, thereby solving the problem that the commonly used current-cutoff protection circuit needs to be manually reset. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A structural principle block diagram of a self-recovery cut-off overcurrent protection circuit in a flameproof and intrinsically safe power supply provided by an embodiment of the utility model;

[0019] Figure 2 A schematic diagram of a self-recovery cutoff overcurrent protection circuit in a flameproof and intrinsically safe power supply provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of this application.

[0021] In the description of this application, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, "plurality" means two or more, unless otherwise clearly and specifically defined.

[0022] like Figure 1As shown, the embodiment of the utility model provides a self-recovery cut-off overcurrent protection circuit in a flameproof and intrinsically safe power supply, including a current sampling resistor R1, a current limiting resistor R2, a current detection circuit, a bistable trigger circuit, a switch circuit, a voltage recovery detection circuit and a voltage stabilizing source;

[0023] One end of the current sampling resistor R1 is connected to the power supply, and the other end is connected to one end of the current limiting resistor R2; the other end of the current limiting resistor R2 is connected to the load;

[0024] The current detection circuit is connected in parallel with the current sampling resistor R1, and the current detection circuit outputs a high level or low level detection signal to the first input terminal of the bistable trigger circuit according to the magnitude of the current flowing through the current sampling resistor R1;

[0025] The output end of the bistable trigger circuit is connected to the control end of the switch circuit; the switch circuit is connected in parallel with the current limiting resistor R2;

[0026] The first input end of the voltage recovery detection circuit is connected to the other end of the current limiting resistor R2, the second input end of the voltage recovery detection circuit is connected to the output end of the bistable trigger circuit, and the output end of the voltage recovery detection circuit is connected to the second input end of the bistable trigger circuit;

[0027] The input end of the voltage stabilizing source is connected to a power supply, and the output end of the voltage stabilizing source outputs a working voltage to the bistable trigger circuit and the voltage recovery detection circuit.

[0028] Figure 2 A schematic diagram of a flameproof and intrinsically safe power supply self-recovery cutoff overcurrent protection circuit provided by the embodiment of the utility model, specifically, as Figure 2 As shown, the current detection circuit is implemented based on the AD8214ARMZ chip, the 1# pin of the AD8214ARMZ chip is connected to the power supply, the 2# pin is connected to one end of the current sampling resistor R1 through the capacitor C1, the 8# pin is connected to the other end of the current sampling resistor R1, the 5# pin outputs the detection signal, the resistor R3 is connected in series with the variable resistor RP1 and then connected in parallel with the capacitor C1, and the two ends of the resistor R5 are respectively connected to the 3# pin of the AD8214ARMZ chip and the variable resistor RP1.

[0029] The bistable trigger circuit is implemented based on the LMC555CM chip. The 4# and 8# pins of the LMC555CM chip are connected to a voltage regulator, the 3# pin is connected to the base of the NPN transistor V4 through a resistor R16, and the collector of the NPN transistor V4 serves as the output end of the bistable trigger circuit. The 2# pin of the LMC555CM chip is respectively connected to the collector of the NPN transistor V7 and the voltage regulator, and the base of the NPN transistor V7 serves as the first input of the bistable trigger circuit. The end is connected to the output of the current detection circuit, the 6# pin of the LMC555CM chip is connected to the collector of the PNP transistor V3, the emitter of the PNP transistor V3 is connected to the voltage regulator, the base of the PNP transistor V3 is connected to the voltage regulator through the resistor R11, the base of the PNP transistor V3 is also connected to the collector of the NPN transistor V6 through the resistor R17, and the base of the NPN transistor V6 is connected to the output end of the voltage recovery detection circuit as the second input end of the bistable trigger circuit.

[0030] The switching circuit includes a switching tube V1 and an NPN transistor V2. The source of the switching tube V1 is connected to one end of the current limiting resistor R2 close to the power supply, the drain of the switching tube V1 is connected to one end of the current limiting resistor R2 close to the load, the gate of the switching tube V1 is connected to the collector of the NPN transistor V2 via a resistor R7, and the base of the NPN transistor V2 is connected to the output end of the bistable trigger circuit as the control end of the switching circuit.

[0031] The voltage recovery detection circuit includes a comparator and an NPN transistor V5. The positive input end of the comparator is connected to the end of the current limiting resistor R2 close to the load through a resistor R13 as the first input end of the voltage recovery detection circuit. The positive input end of the comparator is also connected to the collector of the NPN transistor V5. The base of the NPN transistor V5 is connected to the output end of the bistable trigger circuit as the second input end of the voltage recovery detection circuit. The output end of the comparator is connected to the second input end of the bistable trigger circuit as the output end of the voltage recovery detection circuit. The negative input end of the comparator is connected to a voltage stabilizing source.

[0032] The voltage stabilizing source is implemented based on a 78L05 chip, the input end of the 78L05 chip is connected to a power supply, and outputs a working voltage to the bistable trigger circuit and the voltage recovery detection circuit.

[0033] Working principle:

[0034] like Figure 2As shown in the figure, when the power supply is working normally or the load current is less than the rated current, the 5-pin output of N1 (AD8214ARMZ) in the current detection circuit is low level, the 2-pin of N3 (LMC555CM) in the bistable trigger circuit is high level, and the 6-pin of N3 (LMC555CM) is low level. Therefore, the 3-pin output of N3 (LMC555CM) is low level, the collector of transistor V4 is high level, the transistor V2 and the switch tube V1 are turned on, and the whole circuit works normally. At the same time, the transistor V5 is turned on, shielding the input signal of the voltage recovery detection circuit of N4B (LM393M), making it invalid.

[0035] When the load is short-circuited or the load current is greater than the rated current, the 5-pin output of N1 (AD8214ARMZ) in the current detection circuit is high, the 6-pin of N3 (LMC555CM) is low, and the 2-pin of N3 (LMC555CM) is low. At this time, N3 (LMC555CM) is set. Therefore, the 3-pin output of N3 (LMC555M) is high, the collector of transistor V4 is low, the transistor V2 and the switch tube V1 are cut off, and since the resistance value of resistor R2 is much larger than the equivalent on-resistance of the switch tube V1, the entire circuit is in the off state. After that, the entire circuit no longer responds to the output signal of the 5-pin of N1 (AD8214ARMZ), thereby "locking" the circuit and maintaining the switch tube V1 in the off state. At the same time, the transistor V5 is cut off, and the N4B voltage recovery detection circuit is in the normal detection state.

[0036] When the fault is eliminated or the load current is less than the rated current, that is, when the voltage at pin 5 of N4B is greater than the preset value, pin 7 of N4B outputs a high level, transistors V3 and V6 are turned on, and pin 6 of N3 (LMC555CM) is at a high level. At this time, N3 (LMC555CM) is reset. Therefore, pin 3 of N3 (LMC555CM) outputs a low level, the collector of transistor V4 is at a high level, transistor V2 and switch tube V1 are turned on, and the entire circuit "automatically recovers" to work normally. At the same time, transistor V5 is turned on, shielding the input signal of the N4B voltage recovery detection circuit, making it invalid.

[0037] Although the preferred embodiments of the utility model have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications falling within the scope of the utility model.

[0038] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A self-recovery cut-off overcurrent protection circuit in a flameproof and intrinsically safe power supply, characterized in that: It includes a current sampling resistor R1, a current limiting resistor R2, a current detection circuit, a bistable trigger circuit, a switch circuit, a voltage recovery detection circuit and a voltage stabilizing source; One end of the current sampling resistor R1 is connected to the power supply, and the other end is connected to one end of the current limiting resistor R2; the other end of the current limiting resistor R2 is connected to the load; The current detection circuit is connected in parallel with the current sampling resistor R1, and the current detection circuit outputs a high level or low level detection signal to the first input terminal of the bistable trigger circuit according to the magnitude of the current flowing through the current sampling resistor R1; The output end of the bistable trigger circuit is connected to the control end of the switch circuit; the switch circuit is connected in parallel with the current limiting resistor R2; The first input end of the voltage recovery detection circuit is connected to the other end of the current limiting resistor R2, the second input end of the voltage recovery detection circuit is connected to the output end of the bistable trigger circuit, and the output end of the voltage recovery detection circuit is connected to the second input end of the bistable trigger circuit; The input end of the voltage stabilizing source is connected to a power supply, and the output end of the voltage stabilizing source outputs a working voltage to the bistable trigger circuit and the voltage recovery detection circuit.

2. The self-recovery cut-off overcurrent protection circuit in the flameproof and intrinsically safe power supply according to claim 1 is characterized in that: The current detection circuit is implemented based on the AD8214ARMZ chip. The 1# pin of the AD8214ARMZ chip is connected to the power supply, the 2# pin is connected to one end of the current sampling resistor R1 through the capacitor C1, the 8# pin is connected to the other end of the current sampling resistor R1, the 5# pin outputs the detection signal, the resistor R3 is connected in series with the variable resistor RP1 and then connected in parallel with the capacitor C1, and the two ends of the resistor R5 are respectively connected to the 3# pin of the AD8214ARMZ chip and the variable resistor RP1.

3. The self-recovery cut-off overcurrent protection circuit in the flameproof and intrinsically safe power supply according to claim 1 is characterized in that: The bistable trigger circuit is implemented based on the LMC555CM chip. The 4# and 8# pins of the LMC555CM chip are connected to a voltage regulator, the 3# pin is connected to the base of the NPN transistor V4 through a resistor R16, and the collector of the NPN transistor V4 serves as the output end of the bistable trigger circuit. The 2# pin of the LMC555CM chip is respectively connected to the collector of the NPN transistor V7 and the voltage regulator, and the base of the NPN transistor V7 serves as the first input of the bistable trigger circuit. The end is connected to the output of the current detection circuit, the 6# pin of the LMC555CM chip is connected to the collector of the PNP transistor V3, the emitter of the PNP transistor V3 is connected to the voltage regulator, the base of the PNP transistor V3 is connected to the voltage regulator through the resistor R11, the base of the PNP transistor V3 is also connected to the collector of the NPN transistor V6 through the resistor R17, and the base of the NPN transistor V6 is connected to the output end of the voltage recovery detection circuit as the second input end of the bistable trigger circuit.

4. The self-recovery cut-off overcurrent protection circuit in the flameproof and intrinsically safe power supply according to claim 1 is characterized in that: The switch circuit includes a switch tube V1 and an NPN transistor V2. The source of the switch tube V1 is connected to one end of the current limiting resistor R2 close to the power supply, the drain of the switch tube V1 is connected to one end of the current limiting resistor R2 close to the load, the gate of the switch tube V1 is connected to the collector of the NPN transistor V2 via a resistor R7, and the base of the NPN transistor V2 is connected to the output end of the bistable trigger circuit as the control end of the switch circuit.

5. The self-recovery cut-off overcurrent protection circuit in the flameproof and intrinsically safe power supply according to claim 1 is characterized in that: The voltage recovery detection circuit includes a comparator and an NPN transistor V5. The positive input end of the comparator is connected to the end of the current limiting resistor R2 close to the load through a resistor R13 as the first input end of the voltage recovery detection circuit. The positive input end of the comparator is also connected to the collector of the NPN transistor V5. The base of the NPN transistor V5 is connected to the output end of the bistable trigger circuit as the second input end of the voltage recovery detection circuit. The output end of the comparator is connected to the second input end of the bistable trigger circuit as the output end of the voltage recovery detection circuit. The negative input end of the comparator is connected to a voltage stabilizing source.

6. The self-recovery cut-off overcurrent protection circuit in the flameproof and intrinsically safe power supply according to claim 1 is characterized in that: The voltage stabilizing source is implemented based on a 78L05 chip, the input end of the 78L05 chip is connected to a power supply, and outputs a working voltage to the bistable trigger circuit and the voltage recovery detection circuit.

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