CN111711162A - Short-circuit protection circuit - Google Patents
Short-circuit protection circuit Download PDFInfo
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- CN111711162A CN111711162A CN202010395702.XA CN202010395702A CN111711162A CN 111711162 A CN111711162 A CN 111711162A CN 202010395702 A CN202010395702 A CN 202010395702A CN 111711162 A CN111711162 A CN 111711162A
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/02—Details
- H02H3/04—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned
- H02H3/042—Details with warning or supervision in addition to disconnection, e.g. for indicating that protective apparatus has functioned combined with means for locating the fault
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
- H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
- H02H3/093—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current with timing means
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
- H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
- H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
- H02H9/025—Current limitation using field effect transistors
Abstract
The invention provides a short-circuit protection circuit, relates to the technical field of electric power, and mainly solves the technical problem of short circuit of an electric appliance circuit in normal operation. The invention comprises the following steps: the circuit comprises a circuit voltage, a starting circuit, a state holding circuit, a buffer driving circuit, a double-tube output switch circuit, an overcurrent detection circuit and a state indicating circuit which are connected in sequence; the starting circuit is used for starting the short-circuit protection circuit; the state holding circuit is used for holding a normal passage state or a short-circuit state; the buffer driving circuit is used for enabling the state holding circuit to output enough current to drive the double-tube output switching circuit; the double-tube output switching circuit is used for releasing the short-circuit voltage of the load; the overcurrent detection circuit is used for detecting whether a short-circuit state exists or not; the state indicating circuit is used for displaying whether a short circuit state exists or not through the turning on and off of the indicating lamp. Therefore, the invention has the characteristics of high safety and strong practicability, plays a role of protecting a circuit, and avoids the burning of the circuit and the occurrence of fire.
Description
Technical Field
The invention relates to the technical field of electric power, in particular to a short-circuit protection circuit.
Background
In the case of a short circuit, the two wires of the ac circuit touch each other, and the current does not pass through the electric equipment in the line and directly forms a loop. Because the resistance of the wire is relatively small, if the wire only passes through the loop of the wire, the current can be increased sharply, and is hundreds of times or even tens of thousands of times larger than the normal current. Such a large current is passed through such a thin wire, and the more heat is generated due to the greater resistance of the wire, the temperature of the wire can be raised to thousands of degrees centigrade in an extremely short period of time, which is sufficient to ignite nearby flammable substances, resulting in a fire. The short circuit of the line is caused because the two lines collide with each other due to the aging and cracking of the insulating layer and the loss of the insulating effect caused by the over-long use of the power transmission line; or the 'outer sleeve' of the electric wire is mechanically damaged due to the fact that the electric wire is randomly pulled, and short circuit is caused.
The lead in normal operation is short-circuited suddenly, and along with the extension of short-circuit time, the lead temperature rises sharply to make the short-circuit point near section lead melt and drop, the short-circuit point disconnection drops, simultaneously, produces powerful back electromotive force, and surpasss mains voltage tens times to thousands times surge voltage, still can produce the strong electric arc further heating and melt the wire segment that drops. The instantaneous temperature of the melted wire is increased by more than one hundred times. The wire section is instantly changed into an ultrahigh-temperature spheroid under the action of surface tension, and the ultrahigh-temperature spheroid falls to the ice-cold ground containing moisture and then sparks are splashed enough to ignite surrounding inflammable material. Reducing the short-circuit time can reduce the possibility of melting the wire at the near segment of the short-circuit point. Shortening the short circuit time reduces the incidence of fire. The control loop current off time is critical to reduce the incidence of fire. At present, the traditional fuse and circuit breaker structure can not cut off the loop current quickly within the action time.
Therefore, a short-circuit protection circuit is needed.
Disclosure of Invention
One of the purposes of the invention is to provide a short-circuit protection circuit, which solves the technical problem of short circuit of an electric appliance circuit in normal operation in the prior art. Advantageous effects can be achieved in preferred embodiments of the present invention, as described in detail below.
In order to achieve the purpose, the invention provides the following technical scheme:
the invention provides a short-circuit protection circuit, comprising: the circuit comprises a circuit voltage, a starting circuit, a state holding circuit, a buffer driving circuit, a double-tube output switch circuit, an overcurrent detection circuit and a state indicating circuit which are connected in sequence;
the starting circuit is used for starting the short-circuit protection circuit;
the state holding circuit is used for holding a normal access state or a short-circuit state;
the buffer driving circuit is used for accelerating the high-low level conversion time to output a totem-pole, so that the state holding circuit can output enough current to drive the double-tube output switching circuit;
the double-tube output switching circuit is used for releasing the short-circuit voltage of the load;
the overcurrent detection circuit is used for detecting whether a short-circuit state exists or not, and if the short-circuit state exists, the output current of the overcurrent detection circuit is reduced;
and the state indicating circuit is used for displaying whether a short-circuit state exists in the short-circuit protection circuit or not through the on-off of an indicator lamp.
Further, the start-up circuit includes:
the first resistor, the fourth resistor, the eighth resistor, the first switch, the first capacitor, the second operational amplifier and the F network connection point;
the inverting input end of the second operational amplifier is connected with one end of the fourth resistor and one end of the eighth resistor, the non-inverting input end of the second operational amplifier is connected with one end of the first resistor and one end of the first capacitor, and the output end of the second operational amplifier is used as the output end of the starting circuit;
the other end of the fourth resistor is connected with the circuit voltage; the other end of the eighth resistor and the other end of the first capacitor are both grounded;
one end of the first switch is connected with the other end of the first resistor, the other end of the first switch is connected with a network connection point F, and the first switch is the input end of the starting circuit.
Further, the state holding circuit includes:
a sixth resistor, a first operational amplifier;
the inverting input end of the first operational amplifier is connected with one end of the fourth resistor and one end of the eighth resistor, the non-inverting input end of the first operational amplifier is connected with one end of the sixth resistor, the output end of the first operational amplifier is connected with the other end of the sixth resistor, the positive power supply end of the first operational amplifier is connected with circuit voltage, and the negative power supply end of the first operational amplifier is grounded; and the output end of the first operational amplifier is the output end of the state holding circuit;
the other end of the fourth resistor is connected with the circuit voltage; the other end of the eighth resistor is grounded;
the input end of the state holding circuit is the non-inverting input end of the first operational amplifier.
Further, the buffer driving circuit includes:
the first resistor, the twelfth resistor, the thirteenth resistor, the first triode, the second capacitor, the fourth capacitor and the fourth operational amplifier;
the inverting input end of the fourth operational amplifier is connected with one end of the fourth resistor and one end of the eighth resistor, the non-inverting input end of the fourth operational amplifier is connected with one end of the eleventh resistor, one end of the twelfth resistor and one end of the second capacitor, and the output end of the fourth operational amplifier is connected with the other end of the twelfth resistor and one end of the thirteenth resistor;
the other end of the fourth resistor is connected with the circuit voltage; the other end of the eighth resistor is grounded; the other end of the second capacitor is grounded;
a collector of the second triode is connected with the circuit voltage, a base of the second triode is connected with the other end of the thirteenth resistor and the base of the first triode, and an emitter of the second triode is connected with an emitter of the first triode and a network connection point A; the collector of the first triode is grounded;
one end of the fourth capacitor is connected with the circuit voltage, and the other end of the fourth capacitor is grounded;
the other end of the eleventh resistor is an input end of the buffer driving circuit; and the emission electrode of the second triode is the output end of the buffer driving circuit.
Further, the dual-transistor output switching circuit includes:
the circuit comprises an eighteenth resistor, a nineteenth resistor, a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a second diode, a fourth diode, a fifth diode, a sixth diode, a first voltage dependent resistor, a second voltage dependent resistor, a fifth field effect transistor and a seventh field effect transistor;
the input end of the double-tube output switching circuit is connected with one end of the nineteenth resistor, one end of the twenty-second resistor, the cathode of the second diode and the cathode of the fifth diode;
the drain electrode of the fifth field effect transistor is connected with one end of the twenty-fourth resistor and one end of the second piezoresistor, the grid electrode of the fifth field effect transistor is connected with the other end of the twenty-second resistor, the anode of the fifth diode, one end of the twenty-third resistor and the cathode of the sixth diode, and the source electrode of the fifth field effect transistor is grounded;
the other end of the twenty-third resistor, the anode of the sixth diode and the other end of the second piezoresistor are all grounded;
the source electrode of the seventh field effect transistor is connected with the source electrode of the fifth field effect transistor, the grid electrode of the seventh field effect transistor is connected with the other end of the nineteenth resistor, the anode of the second diode, one end of the eighteenth resistor and the cathode of the fourth diode, and the drain electrode of the seventh field effect transistor is connected with one end of the first piezoresistor;
the other end of the eighteenth resistor is connected with the other end of the twenty-third resistor; the positive electrode of the fourth diode is connected with the positive electrode of the sixth diode; the other end of the first piezoresistor is connected with the other end of the second piezoresistor;
the other end of the twenty-fourth resistor is connected with a network connection point D, and the other end of the twenty-fourth resistor is the output end of the double-tube output switch circuit.
Further, the over-current detection circuit includes:
a ninth resistor, a tenth resistor, a thirteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a third diode, a fifth capacitor, and a third operational amplifier;
one end of the thirteenth resistor is an input end of the over-current detection circuit, and the other end of the thirteenth resistor is respectively connected with the base electrode of the first triode and the base electrode of the second triode; the collector of the second triode is connected with the circuit voltage, and the emitter of the second triode is connected with the emitter of the first triode; a collector of the first triode is connected with one end of the twenty-third resistor, an anode of the sixth diode, a source of the fifth field effect transistor, one end of the second piezoresistor, one end of the fifteenth resistor, one end of the fifth capacitor and one end of the ninth resistor, and is grounded;
the grid electrode of the fifth field effect transistor is connected with the cathode of the sixth diode, the other end of the twenty-third resistor, the anode of the fifth diode and one end of the twenty-second resistor, and the drain electrode of the fifth field effect transistor is connected with the other end of the second piezoresistor and one end of the twenty-fourth resistor;
the other end of the twenty-second resistor is connected with an emitting electrode of the second triode, a negative electrode of the fifth diode, one end of the seventeenth resistor and a network connection point A; the other end of the twenty-fourth resistor is connected with a network connection point D;
the non-inverting input end of the third operational amplifier is connected with the other end of the ninth resistor and one end of the tenth resistor, the inverting input end of the third operational amplifier is connected with the other end of the fifth capacitor, the other end of the fifteenth resistor and one end of the sixteenth resistor, and the output end of the third operational amplifier is the output end of the over-current detection circuit;
the other end of the sixteenth resistor is connected with the anode of the third diode and the other end of the seventeenth resistor; the cathode of the third diode is connected with the other end of the twenty-fourth resistor; the tenth resistor is connected to the circuit voltage.
Further, the status indication circuit includes:
the device comprises a twentieth resistor, a twenty-first resistor, an eighth triode and a first LED lamp;
one end of the thirteenth resistor is an input end of the state indicating circuit, and the other end of the thirteenth resistor is respectively connected with the base electrode of the first triode and the base electrode of the second triode; a collector of the second triode is connected with the circuit voltage, and an emitter of the second triode is connected with an emitter of the first triode, one end of a twenty-first resistor and a network connection point A; the collector of the first triode is grounded;
a base electrode of the eighth triode is connected with the other end of the twenty-first resistor, an emitting electrode of the eighth triode is connected with a collector electrode of the first triode, and a collector electrode of the eighth triode is connected with the other end of the nineteenth resistor, a negative electrode of the first LED lamp and a network connection point F;
the positive electrode of the first LED lamp is connected with the other end of the nineteenth resistor and one end of the twentieth resistor; the other end of the twentieth resistor is connected with the circuit voltage.
Further, the method also comprises the following steps: the input end of the switch type power supply circuit is connected with a mains supply, and the output end of the switch type power supply circuit is connected with the input end of the starting circuit, wherein the output end of the switch type power supply circuit outputs circuit voltage.
Further, the input end of the switch-type power supply circuit is a network connection point B.
Further, the drain electrode of the seventh field effect transistor is also connected with the input end of an alternating current load.
The short-circuit protection circuit provided by the invention at least has the following beneficial technical effects:
according to the invention, through the circuit voltage, the starting circuit, the state holding circuit, the buffer driving circuit, the double-tube output switch circuit, the overcurrent detection circuit and the state indication circuit which are connected in sequence, the loop current in short circuit is quickly cut off, the voltage current of short circuit in a load is led out, the short circuit protection function is realized, and the occurrence of fire accidents is reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
FIG. 1 is a schematic diagram of a short-circuit protection circuit according to the present invention;
FIG. 2 is a schematic circuit diagram of a short circuit protection circuit of the present invention;
FIG. 3 is a circuit schematic of the start-up circuit of the present invention;
FIG. 4 is a circuit schematic of the state holding circuit of the present invention;
FIG. 5 is a circuit schematic of the buffer driver circuit of the present invention;
FIG. 6 is a circuit schematic of a dual-output switching circuit of the present invention;
FIG. 7 is a circuit schematic of the over current detection circuit of the present invention;
FIG. 8 is a circuit schematic of the status indication circuit of the present invention;
FIG. 9 is a circuit schematic of the switching mode power supply circuit of the present invention;
FIG. 10 is a schematic structural diagram of another embodiment of the present invention;
fig. 11 is a circuit schematic of another embodiment of the present invention.
In the figure, 1-a switch type power supply circuit, 2-a starting circuit, 3-a state holding circuit, 4-a buffer driving circuit, 5-a double-tube output switch circuit, 6-an overcurrent detection circuit and 7-a state indicating circuit are arranged.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
Referring to fig. 1 and 2, the present invention is a short-circuit protection circuit, which is composed of a circuit voltage, a starting circuit 2, a state holding circuit 3, a buffer driving circuit 4, a double-tube output switch circuit 5, an overcurrent detection circuit 6 and a state indication circuit 7, which are connected in sequence;
the starting circuit is used for starting the short-circuit protection circuit;
the state holding circuit is used for holding a normal access state or a short-circuit state;
the buffer driving circuit is used for accelerating the high-low level conversion time to output a totem-pole, so that the state holding circuit can output enough current to drive the double-tube output switching circuit;
the double-tube output switching circuit is used for releasing the short-circuit voltage of the load;
the overcurrent detection circuit is used for detecting whether a short-circuit state exists or not, and if the short-circuit state exists, the output current of the overcurrent detection circuit is reduced;
and the state indicating circuit is used for displaying whether a short-circuit state exists in the short-circuit protection circuit or not through the on-off of an indicator lamp.
The invention is connected between a power supply and a load, and is started through a starting circuit; then, the invention keeps a stable state under the normal working condition through a state holding circuit and a buffer driving circuit, namely, the double-crown output switching circuit is driven to work normally; then, if the load is in a short-circuit state, the short-circuit voltage and current of the load are released by adopting a double-tube output switch circuit, so that the short-circuit is protected; in addition, the invention can detect whether the load and the invention have short-circuited voltage and current through the overcurrent detection circuit and the state indicating circuit, and can indicate through the indicator light. Therefore, the invention has the characteristics of high safety and strong practicability, protects the short-circuit, releases high-intensity surge voltage excited during short circuit, avoids the occurrence of circuit burning and electronic device destruction, and also avoids fire, explosion and the like caused by short circuit.
Referring to fig. 3, the start-up circuit includes:
a first resistor R1, a fourth resistor R4, an eighth resistor R8, a first switch S1, a first capacitor C1, a second operational amplifier U1B and a network connection point F;
the inverting input end of the second operational amplifier U1B is connected to one end of the fourth resistor R4 and one end of the eighth resistor R8, the non-inverting input end is connected to one end of the first resistor R1 and one end of the first capacitor C1, and the output end is used as the output end of the start-up circuit;
the other end of the fourth resistor R4 is connected with the circuit voltage; the other end of the eighth resistor R8 and the other end of the first capacitor C1 are both grounded;
one end of the first switch S1 is connected to the other end of the first resistor R1, the other end is connected to a network connection point F, and the first switch S1 is the input end of the start circuit.
The start circuit includes R4, R8, R1, C1, and U1B. R4, R8 form the VCC and GND 1/2 supply voltage link U1B6 pin. When the start button S1 is pressed (F is equal to VCC), C1 is charged through R1, and when the charging voltage U1B7 pin is higher than the U1B66 pin, the U1B1 pin outputs high level to drive the action of the post-stage circuit. Point F goes from VCC to low. The start-up circuit completes a start-up process.
Referring to fig. 4, the state holding circuit, on the basis of the start circuit, further includes: a sixth resistor R6, a first operational amplifier U1A;
the inverting input end of the first operational amplifier U1A is connected with one end of the fourth resistor R4 and one end of the eighth resistor R8, the non-inverting input end is connected with one end of the sixth resistor R6, the output end is connected with the other end of the sixth resistor R6, the positive power supply end is connected with circuit voltage, and the negative power supply end is grounded; and the output terminal of the first operational amplifier U1A is the output terminal of the state holding circuit;
the other end of the fourth resistor R4 is connected with the circuit voltage; the other end of the eighth resistor R8 is grounded.
The input terminal of the state holding circuit is the non-inverting input terminal of the first operational amplifier U1A.
The start-up circuit includes R4, R8, R6, and U1A, and R4 and R8 constitute VCC and GND 1/2 power supply voltages and are connected to pin U1A 4. An R6 deep feedback resistor is added between the 5 pins and the 3 pins of the U1A. When a high-level pulse is input into the pin 5, the pin 3 keeps high-level output all the time. When a low level pulse is input into the 5 pins, the 3 pins keep the level output all the time. Thus, state retention is achieved.
Referring to fig. 5, the buffer driving circuit further includes, in addition to the above-mentioned circuit:
an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a first triode Q1, a second triode Q2, a second capacitor C2, a fourth capacitor C4 and a fourth operational amplifier U1D;
an inverting input terminal of the fourth operational amplifier U1D is connected to one end of the fourth resistor R4 and one end of the eighth resistor R8, a non-inverting input terminal thereof is connected to one end of the eleventh resistor R11, one end of the twelfth resistor R12 and one end of the second capacitor C2, and an output terminal thereof is connected to the other end of the twelfth resistor R12 and one end of the thirteenth resistor R13;
the other end of the fourth resistor R4 is connected with the circuit voltage; the other end of the eighth resistor R8 is grounded; the other end of the second capacitor C2 is grounded;
the collector of the second triode Q2 is connected with the circuit voltage, the base is connected with the other end of the thirteenth resistor R13 and the base of the first triode Q1, and the emitter is connected with the emitter of the first triode Q1 and a network connection point A; the collector of the first triode Q1 is grounded;
one end of the fourth capacitor C4 is connected with the circuit voltage, and the other end of the fourth capacitor C4 is grounded;
the other end of the eleventh resistor R11 is an input end of the buffer driving circuit; the emitter of the second transistor Q2 is the output of the buffer driving circuit.
The buffer drive circuit is composed of U1D, R12, R13, Q1, and Q2. The R12 is connected across the 11 pin and the 13 pin of the U1D and is used for accelerating the high-low level conversion time, so that the Q1 and the Q2 form totem pole output, namely, enough current is output to drive a double-tube output switching circuit.
Referring to fig. 6, the two-transistor output switch circuit includes, based on the foregoing circuit:
an eighteenth resistor R18, a nineteenth resistor R19, a twenty-second resistor R22, a twenty-third resistor R23, a twenty-fourth resistor R24, a second diode D2, a fourth diode D4, a fifth diode D5, a sixth diode D6, a first piezoresistor RV1, a second piezoresistor RV2, a fifth field effect transistor Q5 and a seventh field effect transistor Q7;
the input end of the double-tube output switch circuit is connected with one end of the nineteenth resistor R19, one end of the twenty-second resistor R22, the cathode of the second diode D2 and the cathode of the fifth diode D5;
the drain of the fifth field-effect transistor Q5 is connected to one end of the twenty-fourth resistor R24 and one end of the second piezoresistor RV2, the gate is connected to the other end of the twenty-second resistor R22, the anode of the fifth diode D5, one end of the twenty-third resistor R23 and the cathode of the sixth diode D6, and the source is grounded;
the other end of the twenty-third resistor R23, the anode of the sixth diode D6 and the other end of the second piezoresistor RV2 are all grounded;
a source electrode of the seventh field-effect transistor Q7 is connected with a source electrode of the fifth field-effect transistor Q5, a grid electrode of the seventh field-effect transistor Q7 is connected with the other end of the nineteenth resistor R19, an anode of the second diode D2, one end of the eighteenth resistor R18 and a cathode of the fourth diode D4, and a drain electrode of the seventh field-effect transistor Q7 is connected with one end of the first piezoresistor RV 1;
the other end of the eighteenth resistor R18 is connected with the other end of the twenty-third resistor R23; the anode of the fourth diode D4 is connected with the anode of the sixth diode D6; the other end of the first piezoresistor RV1 is connected with the other end of the second piezoresistor RV 2;
the other end of the twenty-fourth resistor R24 is connected with a network connection point D, and the other end of the twenty-fourth resistor R24 is the output end of the double-tube output switch circuit.
The drain electrode of the seventh field effect transistor is also connected with the input end of the alternating current load.
The two-transistor output switch circuit includes R18, R19, R22, R23, D2, D5, D4, D6, R24, RV1, RV2, Q5, and Q7.
The network connection point A is a totem pole output end signal formed by the upper-stage buffer driving circuits Q1 and Q2, the signal is sent to the gates of Q5 and Q7 through R19 and R22 to control the simultaneous on and off of the two field effect transistors, and D4 and D6 are voltage stabilizing tubes used for preventing generated surge voltage from breaking down the driving tube at the front stage through Miller capacitors in Q5 and Q7 when the sources and the drains of the two field effect transistors are switched off. D2 and D5 are used for accelerating the turn-off time of Q5 and Q7 switching tubes. RV1, RV2 prevent the Q5, Q7 switching tube from breaking through by too high surge voltage when Q5, Q7 turn off. R24 can be used for short circuit current sampling.
Referring to fig. 7, the over-current detection circuit, based on the foregoing circuit, includes:
a ninth resistor R9, a tenth resistor R10, a thirteenth resistor R13, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, a twenty-second resistor R22, a twenty-third resistor R23, a twenty-fourth resistor R24, a third diode D3, a fifth capacitor C5, and a third operational amplifier U1C;
one end of the thirteenth resistor R13 is an input end of the over-current detection circuit, and the other end of the thirteenth resistor R13 is respectively connected with the base electrode of the first triode Q1 and the base electrode of the second triode Q2; the collector electrode of the second triode Q2 is connected with the circuit voltage, and the emitter electrode of the second triode Q3578 is connected with the emitter electrode of the first triode Q1; a collector of the first triode Q1 is connected to one end of the twenty-third resistor R23, an anode of the sixth diode D6, a source of the fifth field effect Q5, one end of the second voltage dependent resistor RV2, one end of the fifteenth resistor R15, one end of the fifth capacitor C5, and one end of the ninth resistor R9, and is grounded;
the grid electrode of the fifth field effect transistor Q5 is connected with the cathode of the sixth diode D6, the other end of the twenty-third resistor R23, the anode of the fifth diode D5 and one end of the twenty-second resistor R22, and the drain electrode is connected with the other end of the second piezoresistor RV2 and one end of the twenty-fourth resistor R24;
the other end of the twenty-second resistor R22 is connected with the emitter of the second triode Q2, the cathode of a fifth diode D5, one end of a seventeenth resistor R17 and a network connection point A; the other end of the twenty-fourth resistor R24 is connected with a network connection point D;
a non-inverting input end of the third operational amplifier U1C is connected to the other end of the ninth resistor R9 and one end of a tenth resistor R10, an inverting input end of the third operational amplifier U1 is connected to the other end of the fifth capacitor C5, the other end of the fifteenth resistor R15 and one end of a sixteenth resistor R16, and an output end of the third operational amplifier U1C is an output end of the over-current detection circuit;
the other end of the sixteenth resistor R16 is connected with the anode of the third diode D3 and the other end of the seventeenth resistor R17; the cathode of the third diode D3 is connected with the other end of the twenty-fourth resistor R24; the tenth resistor R10 is connected to the circuit voltage.
The overcurrent detection circuit is configured by R17, Q5, R24, D3, R15, R16, C5, R9, R10, and U1C. Q1, Q2 output high level (A point is high level), and the drain is equal to the through GND after Q5 is turned on; namely, when the point A works normally, high level is output, one end of R17 is high level, the other end is connected with the anode of the diode D3 and is connected with R24, and the resistance value of R24 is milliohm and is connected with the drain of Q5, so that the resistance value is equal to the link GND. Therefore, the voltage of the anode (anode) connected with the D3 is less than 0.8V, and the voltage of the pin 8 connected with the U1C is less than 0.2V after the voltage is divided by the R16 and the R15. The 9-pin contact voltage of R9, R10, U1C is assumed to be 0.5V. When the current is too large when the point D (output end) is short-circuited, the voltage at the point D rises rapidly, the connection points of R17, D3 and R24 also rise rapidly, and when the voltage of the pin 8 of U1C is higher than the voltage of the pin 9, the pin 14 changes from high level to low level. Thus, overcurrent detection is completed.
Referring to fig. 8, the status indication circuit, based on the foregoing circuit, includes:
a twentieth resistor R20, a twenty-first resistor R21, an eighth triode Q8 and a first LED lamp LED 1;
one end of the thirteenth resistor R13 is an input end of the state indicating circuit, and the other end is respectively connected with the base electrode of the first triode Q1 and the base electrode of the second triode Q2; the collector of the second triode Q2 is connected with the circuit voltage, and the emitter of the second triode Q2 is connected with the emitter of the first triode Q1, one end of a twenty-first resistor R21 and a network connection point A; the collector of the first triode Q1 is grounded;
a base electrode of the eighth triode Q8 is connected with the other end of the twenty-first resistor R21, an emitter electrode of the eighth triode Q8 is connected with a collector electrode of the first triode Q1, and a collector electrode of the eighth triode Q8 is connected with the other end of the nineteenth resistor R19, a negative electrode of the first LED lamp LED1 and a network connection point F;
the anode of the first LED lamp LED1 is connected with the other end of the nineteenth resistor R19 and one end of the twentieth resistor R20; the other end of the twentieth resistor R20 is connected to the circuit voltage.
The status indicator circuit includes R19, R20, R21, Q8, and an LED1, and when the point a is at a high level, the Q8 turns on the LED1 to light up, and the point F is at a low level. The start-up circuit no longer has an output.
Referring to fig. 9, the present invention further comprises: the input end of the switch type power supply circuit is connected with a mains supply, and the output end of the switch type power supply circuit is connected with the input end of the starting circuit, wherein the output end of the switch type power supply circuit outputs circuit voltage.
The input end of the switch type power supply circuit is a network connection point B.
Referring to fig. 10 and 11, another embodiment of the present invention is a schematic structural diagram and a circuit diagram for practical operation, and the theoretical basis thereof is based on the above embodiment. J2 is the input terminal of the load, and J1 is the output terminal of the load.
The working principle is as follows:
under the normal operation condition, the point A outputs high level, the pin 3 of the inverter U5A outputs low level, the pin 9 of the U5C outputs low level, the pin 10 outputs high level, the pins 12 and 13 of the inverter U5D are both high level, the pin 11 outputs low level, and the rear circuit is conducted. Point D is grounded through Q5 and Q11.
In the case of a short circuit, the voltage at point D rises momentarily (over 12V) and is no longer grounded, and point D outputs a low level through D5, R17 and R15 to the inverting input of U1C. When the point a outputs a low level, the pin 3 of the inverter U5A outputs a high level, and when any pin of the pins 8 and 9 of the U5C is a high level, the U5C outputs a low level, and the following circuits are not turned on. The short-circuit voltage current is grounded through Q7, RV1, Q11 and RV 2.
The C1 is used as a starting delay capacitor, and when the voltage of the C1 exceeds one half VCC voltage, the invention is formally started. When short circuited, U1C outputs a low level, also completely discharging the power in C1. Therefore, C1 plays a protective role.
The U2A and the U5B form a delay circuit and play a role in delaying the load. Then in starting the present invention, let the voltage at point C pull down the voltage through R69, so that the start circuit has enough time to start and operate the present invention normally.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (10)
1. A short-circuit protection circuit, comprising: the circuit comprises a circuit voltage, a starting circuit, a state holding circuit, a buffer driving circuit, a double-tube output switch circuit, an overcurrent detection circuit and a state indicating circuit which are connected in sequence;
the starting circuit is used for starting the short-circuit protection circuit;
the state holding circuit is used for holding a normal access state or a short-circuit state;
the buffer driving circuit is used for accelerating the high-low level conversion time to output a totem-pole, so that the state holding circuit can output enough current to drive the double-tube output switching circuit;
the double-tube output switching circuit is used for releasing the short-circuit voltage of the load;
the overcurrent detection circuit is used for detecting whether a short-circuit state exists or not, and if the short-circuit state exists, the output current of the overcurrent detection circuit is reduced;
and the state indicating circuit is used for displaying whether a short-circuit state exists in the short-circuit protection circuit or not through the on-off of an indicator lamp.
2. The circuit of claim 1, wherein the start-up circuit comprises:
the first resistor, the fourth resistor, the eighth resistor, the first switch, the first capacitor, the second operational amplifier and the F network connection point;
the inverting input end of the second operational amplifier is connected with one end of the fourth resistor and one end of the eighth resistor, the non-inverting input end of the second operational amplifier is connected with one end of the first resistor and one end of the first capacitor, and the output end of the second operational amplifier is used as the output end of the starting circuit;
the other end of the fourth resistor is connected with the circuit voltage; the other end of the eighth resistor and the other end of the first capacitor are both grounded;
one end of the first switch is connected with the other end of the first resistor, the other end of the first switch is connected with a network connection point F, and the first switch is the input end of the starting circuit.
3. The circuit of claim 2, wherein the state retention circuit comprises:
a sixth resistor, a first operational amplifier;
the inverting input end of the first operational amplifier is connected with one end of the fourth resistor and one end of the eighth resistor, the non-inverting input end of the first operational amplifier is connected with one end of the sixth resistor, the output end of the first operational amplifier is connected with the other end of the sixth resistor, the positive power supply end of the first operational amplifier is connected with circuit voltage, and the negative power supply end of the first operational amplifier is grounded; and the output end of the first operational amplifier is the output end of the state holding circuit;
the other end of the fourth resistor is connected with the circuit voltage; the other end of the eighth resistor is grounded;
the input end of the state holding circuit is the non-inverting input end of the first operational amplifier.
4. The circuit of claim 3, wherein the buffer driver circuit comprises:
the first resistor, the twelfth resistor, the thirteenth resistor, the first triode, the second capacitor, the fourth capacitor and the fourth operational amplifier;
the inverting input end of the fourth operational amplifier is connected with one end of the fourth resistor and one end of the eighth resistor, the non-inverting input end of the fourth operational amplifier is connected with one end of the eleventh resistor, one end of the twelfth resistor and one end of the second capacitor, and the output end of the fourth operational amplifier is connected with the other end of the twelfth resistor and one end of the thirteenth resistor;
the other end of the fourth resistor is connected with the circuit voltage; the other end of the eighth resistor is grounded; the other end of the second capacitor is grounded;
a collector of the second triode is connected with the circuit voltage, a base of the second triode is connected with the other end of the thirteenth resistor and the base of the first triode, and an emitter of the second triode is connected with an emitter of the first triode and a network connection point A; the collector of the first triode is grounded;
one end of the fourth capacitor is connected with the circuit voltage, and the other end of the fourth capacitor is grounded;
the other end of the eleventh resistor is an input end of the buffer driving circuit; and the emission electrode of the second triode is the output end of the buffer driving circuit.
5. The circuit of claim 4, wherein the dual-tube output switching circuit comprises:
the circuit comprises an eighteenth resistor, a nineteenth resistor, a twenty-second resistor, a twenty-third resistor, a twenty-fourth resistor, a second diode, a fourth diode, a fifth diode, a sixth diode, a first voltage dependent resistor, a second voltage dependent resistor, a fifth field effect transistor and a seventh field effect transistor;
the input end of the double-tube output switching circuit is connected with one end of the nineteenth resistor, one end of the twenty-second resistor, the cathode of the second diode and the cathode of the fifth diode;
the drain electrode of the fifth field effect transistor is connected with one end of the twenty-fourth resistor and one end of the second piezoresistor, the grid electrode of the fifth field effect transistor is connected with the other end of the twenty-second resistor, the anode of the fifth diode, one end of the twenty-third resistor and the cathode of the sixth diode, and the source electrode of the fifth field effect transistor is grounded;
the other end of the twenty-third resistor, the anode of the sixth diode and the other end of the second piezoresistor are all grounded;
the source electrode of the seventh field effect transistor is connected with the source electrode of the fifth field effect transistor, the grid electrode of the seventh field effect transistor is connected with the other end of the nineteenth resistor, the anode of the second diode, one end of the eighteenth resistor and the cathode of the fourth diode, and the drain electrode of the seventh field effect transistor is connected with one end of the first piezoresistor;
the other end of the eighteenth resistor is connected with the other end of the twenty-third resistor; the positive electrode of the fourth diode is connected with the positive electrode of the sixth diode; the other end of the first piezoresistor is connected with the other end of the second piezoresistor;
the other end of the twenty-fourth resistor is connected with a network connection point D, and the other end of the twenty-fourth resistor is the output end of the double-tube output switch circuit.
6. The circuit of claim 5, wherein the over-current detection circuit comprises:
a ninth resistor, a tenth resistor, a thirteenth resistor, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor, a third diode, a fifth capacitor, and a third operational amplifier;
one end of the thirteenth resistor is an input end of the over-current detection circuit, and the other end of the thirteenth resistor is respectively connected with the base electrode of the first triode and the base electrode of the second triode; the collector of the second triode is connected with the circuit voltage, and the emitter of the second triode is connected with the emitter of the first triode; a collector of the first triode is connected with one end of the twenty-third resistor, an anode of the sixth diode, a source of the fifth field effect transistor, one end of the second piezoresistor, one end of the fifteenth resistor, one end of the fifth capacitor and one end of the ninth resistor, and is grounded;
the grid electrode of the fifth field effect transistor is connected with the cathode of the sixth diode, the other end of the twenty-third resistor, the anode of the fifth diode and one end of the twenty-second resistor, and the drain electrode of the fifth field effect transistor is connected with the other end of the second piezoresistor and one end of the twenty-fourth resistor;
the other end of the twenty-second resistor is connected with an emitting electrode of the second triode, a negative electrode of the fifth diode, one end of the seventeenth resistor and a network connection point A; the other end of the twenty-fourth resistor is connected with a network connection point D;
the non-inverting input end of the third operational amplifier is connected with the other end of the ninth resistor and one end of the tenth resistor, the inverting input end of the third operational amplifier is connected with the other end of the fifth capacitor, the other end of the fifteenth resistor and one end of the sixteenth resistor, and the output end of the third operational amplifier is the output end of the over-current detection circuit;
the other end of the sixteenth resistor is connected with the anode of the third diode and the other end of the seventeenth resistor; the cathode of the third diode is connected with the other end of the twenty-fourth resistor; the tenth resistor is connected to the circuit voltage.
7. The circuit of claim 6, wherein the status indication circuit comprises:
the device comprises a twentieth resistor, a twenty-first resistor, an eighth triode and a first LED lamp;
one end of the thirteenth resistor is an input end of the state indicating circuit, and the other end of the thirteenth resistor is respectively connected with the base electrode of the first triode and the base electrode of the second triode; a collector of the second triode is connected with the circuit voltage, and an emitter of the second triode is connected with an emitter of the first triode, one end of a twenty-first resistor and a network connection point A; the collector of the first triode is grounded;
a base electrode of the eighth triode is connected with the other end of the twenty-first resistor, an emitting electrode of the eighth triode is connected with a collector electrode of the first triode, and a collector electrode of the eighth triode is connected with the other end of the nineteenth resistor, a negative electrode of the first LED lamp and a network connection point F;
the positive electrode of the first LED lamp is connected with the other end of the nineteenth resistor and one end of the twentieth resistor; the other end of the twentieth resistor is connected with the circuit voltage.
8. The circuit of claim 1, further comprising: the input end of the switch type power supply circuit is connected with a mains supply, and the output end of the switch type power supply circuit is connected with the input end of the starting circuit, wherein the output end of the switch type power supply circuit outputs circuit voltage.
9. The circuit of claim 8, wherein the input of the switch mode power supply circuit is network connection point B.
10. The circuit of claim 5, wherein the drain of the seventh FET is further connected to an input of an AC load.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202010395702.XA CN111711162B (en) | 2020-05-12 | 2020-05-12 | Short-circuit protection circuit |
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| CN202010395702.XA CN111711162B (en) | 2020-05-12 | 2020-05-12 | Short-circuit protection circuit |
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| CN111711162B CN111711162B (en) | 2022-03-18 |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112909890A (en) * | 2021-01-29 | 2021-06-04 | 张自国 | Direct-current short-circuit protection module of electric vehicle |
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| CN111711162B (en) | 2022-03-18 |
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