CN219351275U - Overcurrent and short-circuit protection circuit with current limiting and cutting-off functions - Google Patents
Overcurrent and short-circuit protection circuit with current limiting and cutting-off functions Download PDFInfo
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- CN219351275U CN219351275U CN202223369044.0U CN202223369044U CN219351275U CN 219351275 U CN219351275 U CN 219351275U CN 202223369044 U CN202223369044 U CN 202223369044U CN 219351275 U CN219351275 U CN 219351275U
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Abstract
The utility model discloses an overcurrent and short-circuit protection circuit which is firstly subjected to current limiting and then cutting off, comprising a first resistor, an eighth resistor, a first field effect tube, a fifth field effect tube, a photoelectric coupler and a capacitor, wherein the first resistor and the first field effect tube are connected in series on a circuit loop, the first resistor, the photoelectric coupler, a fourth field effect tube, the fourth resistor and the sixth resistor form a negative feedback circuit, the opening voltage of the fourth field effect tube is lower than the opening voltage of a third field effect tube, and the third resistor and the capacitor form an integrating circuit. The utility model realizes the protection function of firstly limiting current and then cutting off when the circuit is in overcurrent or short circuit, thereby not only avoiding the problem that the normal operation of the circuit is affected because the power supply is cut off due to normal instantaneous overcurrent, but also avoiding the problem that the potential safety hazard is caused because the power supply cannot be cut off due to long-term overcurrent or short circuit.
Description
Technical Field
The present utility model relates to an overcurrent and short-circuit protection circuit, and more particularly, to an overcurrent and short-circuit protection circuit with current limiting and then cutting.
Background
In the power supply system, when the electric equipment is abnormal, the power supply current of the power supply system can be instantaneously or for a long time overflowed, even the load end is directly short-circuited, and safety accidents are caused. In order to solve the problem of safety accidents caused by overcurrent and short circuit, the traditional solution mainly comprises two modes of fuse blowing and current limiting, but the two traditional schemes have the following defects:
the overcurrent protection is carried out by adopting a fuse fusing mode, the power supply is directly cut off by adopting the protection mode, if the fuse fusing speed is high, the normal instantaneous overcurrent can also cause the fuse fusing to cause the system outage, and if the fuse fusing speed is low, the high current in the short circuit can not be fused in time, the protection effect is seriously influenced, so the fuse fusing mode is not suitable for a plurality of systems;
the overcurrent protection is carried out in a current limiting mode, the power supply is not cut off, and even if the equipment end is short-circuited, the power supply is not cut off, so that the power supply system can work in a higher load state for a long time, and besides the power loss is caused, the obvious potential safety hazard exists.
Disclosure of Invention
The present utility model aims to solve the above problems by providing an overcurrent and short-circuit protection circuit which is limited and then cut off.
The utility model realizes the above purpose through the following technical scheme:
an overcurrent and short-circuit protection circuit which is firstly subjected to current limiting and then cutting off comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first field effect tube, a second field effect tube, a third field effect tube, a fourth field effect tube, a fifth field effect tube, a photoelectric coupler and a capacitor, wherein the first field effect tube is a P-channel field effect tube, the second field effect tube-the fifth field effect tube is an N-channel field effect tube, the opening voltage of the fourth field effect tube is lower than the opening voltage of the third field effect tube, the first end of the first resistor, the first end of the second resistor, the first end of the third resistor and the first end of the eighth resistor are connected with the positive electrode of a direct current power supply input end, the second end of the first resistor, the first end of the fourth resistor, the first end of the fifth resistor, the negative electrode of the input end of the photoelectric coupler and the source electrode of the first field effect tube are connected, the second end of the second resistor is connected with the positive electrode of the input end of the photoelectric coupler, the second end of the third resistor, the first end of the capacitor, the grid electrode of the fifth field effect tube, the grid electrode of the second field effect tube and the drain electrode of the third field effect tube are connected, the second end of the eighth resistor is connected with the drain electrode of the fifth field effect tube, the drain electrode of the second field effect tube, the grid electrode of the third field effect tube, the positive electrode of the output end of the photoelectric coupler, the second end of the fifth resistor, the first end of the seventh resistor and the grid electrode of the fourth field effect tube are connected, the second end of the fourth resistor, the first end of the sixth resistor and the grid electrode of the first field effect tube are connected, the drain electrode of the first field effect transistor is used as the positive electrode of the direct current power supply output end, and the source electrode of the fifth field effect transistor, the second end of the capacitor, the source electrode of the second field effect transistor, the source electrode of the third field effect transistor, the negative electrode of the output end of the photoelectric coupler, the second end of the seventh resistor, the source electrode of the fourth field effect transistor and the negative electrode of the direct current power supply input end are connected and used as the negative electrode of the direct current power supply output end.
Preferably, in order to facilitate light indication for the overcurrent fault, a light emitting diode is connected between the second end of the eighth resistor and the drain electrode of the fifth field effect transistor, the positive electrode of the light emitting diode is connected with the second end of the eighth resistor, and the negative electrode of the light emitting diode is connected with the drain electrode of the fifth field effect transistor.
Preferably, in order to stabilize the voltage of each field effect transistor, the gate of the first field effect transistor is connected to the positive electrode of the first zener diode, the source of the first field effect transistor is connected to the negative electrode of the first zener diode, the source of the second field effect transistor is connected to the positive electrode of the second zener diode, the gate of the second field effect transistor is connected to the negative electrode of the second zener diode, the source of the third field effect transistor is connected to the positive electrode of the third zener diode, and the gate of the third field effect transistor is connected to the negative electrode of the third zener diode.
The utility model has the beneficial effects that:
the utility model forms a negative feedback circuit by using the first resistor, the photoelectric coupler, the fourth field effect transistor, the fourth resistor and the sixth resistor, and realizes current limiting by adjusting the resistance between the drain source and the source of the first field effect transistor; the characteristic that the opening voltage of the fourth field effect tube is lower than that of the third field effect tube, and the timing function of an integrating circuit formed by the third resistor and the capacitor is started, if the fault is not eliminated in a certain time, the power supply of the main circuit is cut off, the power supply system is protected, the self-locking circuit is started, the power supply of the main circuit is locked in a cut-off state, the purpose of protecting the circuit is achieved, the protection function that the current is limited firstly and then cut off when the circuit is in overcurrent or short circuit is finally realized, the problem that the power supply is cut off immediately when the circuit is in normal instant overcurrent is avoided, and the problem that the potential safety hazard is caused because the power supply cannot be cut off due to short circuit or long-term overcurrent is avoided.
Drawings
Fig. 1 is a circuit diagram of an overcurrent and short-circuit protection circuit of the present utility model that is limited and then cut off.
Detailed Description
The utility model is further described below with reference to the accompanying drawings:
as shown in FIG. 1, the over-current and short-circuit protection circuit of the utility model comprises a first resistor R1-eighth resistor R8, a first field effect transistor Q1-fifth field effect transistor Q5, a photoelectric coupler U1 and a capacitor C1, wherein the first field effect transistor Q1 is a P-channel field effect transistor, the second field effect transistor Q2-fifth field effect transistor Q5 is an N-channel field effect transistor, the opening voltage of the fourth field effect transistor Q4 is lower than the opening voltage of the third field effect transistor Q3, the first end of the first resistor R1, the first end of the second resistor R2, the first end of the third resistor R3, the first end of the eighth resistor R8 are connected with the positive electrode Vi+ of the input end of a direct current power supply, the second end of the first resistor R1, the first end of the fourth resistor R4, the first end of the fifth resistor R5, the negative electrode of the input end of the photoelectric coupler U1 are connected with the source electrode of the first field effect transistor Q1, the second end of the second resistor R2 is connected with the positive electrode of the input end of the photoelectric coupler U1, the second end of the third resistor R3, the first end of the capacitor C1, the grid G of the fifth field effect transistor Q5, the grid G of the second field effect transistor Q2 and the drain D of the third field effect transistor Q3 are connected, the second end of the eighth resistor R8 is connected with the drain D of the fifth field effect transistor Q5, the drain D of the second field effect transistor Q2, the grid G of the third field effect transistor Q3, the positive electrode of the output end of the photoelectric coupler U1, the second end of the fifth resistor R5, the first end of the seventh resistor R7 and the grid G of the fourth field effect transistor Q4 are connected, the second end of the fourth resistor R4, the first end of the sixth resistor R6 and the grid G of the first field effect transistor Q1 are connected, the drain D of the first field effect transistor Q1 serves as the positive electrode vo+ of the direct current power output end, the source S of the fifth field effect transistor Q5, the second end of the capacitor C1 and the source S of the second field effect transistor Q2, the source electrode S of the third field effect transistor Q3, the negative electrode of the output end of the photoelectric coupler U1, the second end of the seventh resistor R7, and the source electrode S of the fourth field effect transistor Q4 are connected with the negative electrode Vi of the direct current power supply input end and serve as the negative electrode Vo of the direct current power supply output end.
As shown in fig. 1, preferably, in order to facilitate light indication of the overcurrent fault, a light emitting diode LED1 is connected between the second end of the eighth resistor R8 and the drain D of the fifth field effect transistor Q5, the positive electrode of the light emitting diode LED1 is connected with the second end of the eighth resistor R8, and the negative electrode of the light emitting diode LED1 is connected with the drain D of the fifth field effect transistor Q5; in order to stabilize the voltage of each field effect transistor, a gate electrode G of the first field effect transistor Q1 is connected to an anode of the first voltage stabilizing diode D1, a source electrode S of the first field effect transistor Q1 is connected to a cathode of the first voltage stabilizing diode D1, a source electrode S of the second field effect transistor Q2 is connected to an anode of the second voltage stabilizing diode D2, a gate electrode G of the second field effect transistor Q2 is connected to a cathode of the second voltage stabilizing diode D2, a source electrode S of the third field effect transistor Q3 is connected to an anode of the third voltage stabilizing diode D3, and a gate electrode G of the third field effect transistor Q3 is connected to a cathode of the third voltage stabilizing diode D2.
As shown in fig. 1, the current of the circuit loop is sampled by the sampling resistor, that is, the first resistor R1 and fed back to the photocoupler U1, when the circuit is normal, the photocoupler U1 does not operate, the first fet Q1, the third fet Q3, and the fourth fet Q4 are turned on, and the second fet Q2 and the fifth fet Q5 are turned off.
When the circuit is over-current and increased to a certain value, the diode in the photoelectric coupler U1 is driven to emit light, the triode in the photoelectric coupler U1 is conducted, the grid electrode G of the third field effect tube Q3 and the grid electrode G of the fourth field effect tube Q4 are pulled to a low level (the potential difference between the grid electrode G and the source electrode S of the two field effect tubes is reduced), the third field effect tube Q3 is in an off state, the fourth field effect tube Q4 works in a variable resistance region linear region, the resistor between the drain electrode D and the source electrode S of the fourth field effect tube Q4 and the fourth resistor R4 and the sixth resistor R6 participate in voltage division, the voltage of the grid source electrode G of the first field effect tube Q1 is regulated, the first field effect tube Q1 works in a variable resistance region, the resistance between the drain electrode D and the source electrode S of the first field effect tube Q1 is increased, the current flowing through the first resistor R1 in a main loop is reduced, a negative feedback mechanism is formed, and the balance point of negative feedback is the current limiting value of the system.
If the circuit works in the current limiting state for a long time, the switching-on voltage of the third field effect transistor Q3 is higher than that of the fourth field effect transistor Q4, and the fourth field effect transistor Q4 works in the variable resistance region and the third field effect transistor Q3 is in the cut-off state by selecting the field effect transistor with proper parameters; after the third field effect tube Q3 is cut off, an integrating circuit formed by the third resistor R3 and the capacitor C1 starts to work, a power supply charges the capacitor C1 through the third resistor R3, the voltage on the capacitor C1 is gradually increased, and the potential of the grid electrode G of the second field effect tube Q2 and the fifth field effect tube Q5 connected with the capacitor C1 is continuously increased until the second field effect tube Q2 and the fifth field effect tube Q5 are conducted; after the fifth field effect transistor Q5 is conducted, the light emitting diode LED1 connected in series with the eighth resistor R8 emits light, which indicates that the circuit has faults; after the second field effect tube Q2 is conducted, a self-locking protection mechanism of the circuit is triggered, the voltages of the grid electrodes G of the third field effect tube Q3 and the fourth field effect tube Q4 are directly pulled down, the third field effect tube Q3 and the fourth field effect tube Q4 are cut off, the first field effect tube Q1 on the main loop is cut off due to the cut-off of the fourth field effect tube Q4, the self-locking state is maintained all the time, and the self-locking state can be released only by power failure.
The above embodiments are only preferred embodiments of the present utility model, and are not limiting to the technical solutions of the present utility model, and any technical solution that can be implemented on the basis of the above embodiments without inventive effort should be considered as falling within the scope of protection of the patent claims of the present utility model.
Claims (3)
1. An overcurrent and short-circuit protection circuit which is firstly limited and then cut off is characterized in that: comprises a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a first field effect tube, a second field effect tube, a third field effect tube, a fourth field effect tube, a fifth field effect tube, a photoelectric coupler and a capacitor, wherein the first field effect tube is a P-channel field effect tube, the second field effect tube-the fifth field effect tube is an N-channel field effect tube, the opening voltage of the fourth field effect tube is lower than the opening voltage of the third field effect tube, the first end of the first resistor, the first end of the second resistor, the first end of the third resistor and the first end of the eighth resistor are connected with the positive electrode of the input end of a direct current power supply, the second end of the first resistor, the first end of the fourth resistor, the first end of the fifth resistor, the negative electrode of the input end of the photoelectric coupler and the source electrode of the first field effect tube are connected, the second end of the second resistor is connected with the positive electrode of the input end of the photoelectric coupler, the second end of the third resistor, the first end of the capacitor, the grid electrode of the fifth field effect tube, the grid electrode of the second field effect tube and the drain electrode of the third field effect tube are connected, the second end of the eighth resistor is connected with the drain electrode of the fifth field effect tube, the drain electrode of the second field effect tube, the grid electrode of the third field effect tube, the positive electrode of the output end of the photoelectric coupler, the second end of the fifth resistor, the first end of the seventh resistor and the grid electrode of the fourth field effect tube are connected, the second end of the fourth resistor, the first end of the sixth resistor and the grid electrode of the first field effect tube are connected, the drain electrode of the first field effect tube is used as the positive electrode of the output end of a direct current power supply, the source electrode of the fifth field effect tube, the second end of the capacitor, the source electrode of the second field effect tube, the source electrode of the third field effect tube, the negative electrode of the output end of the photoelectric coupler, the second end of the seventh resistor, the source electrode of the fourth field effect tube and the negative electrode of the input end of the direct current power supply are connected and serve as the negative electrode of the output end of the direct current power supply.
2. The overcurrent and short-circuit protection circuit of claim 1, wherein: a light emitting diode is connected between the second end of the eighth resistor and the drain electrode of the fifth field effect tube, the positive electrode of the light emitting diode is connected with the second end of the eighth resistor, and the negative electrode of the light emitting diode is connected with the drain electrode of the fifth field effect tube.
3. The overcurrent and short-circuit protection circuit according to claim 1 or 2, wherein: the grid electrode of the first field effect tube is connected with the positive electrode of the first voltage stabilizing diode, the source electrode of the first field effect tube is connected with the negative electrode of the first voltage stabilizing diode, the source electrode of the second field effect tube is connected with the positive electrode of the second voltage stabilizing diode, the grid electrode of the second field effect tube is connected with the negative electrode of the second voltage stabilizing diode, the source electrode of the third field effect tube is connected with the positive electrode of the third voltage stabilizing diode, and the grid electrode of the third field effect tube is connected with the negative electrode of the third voltage stabilizing diode.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223369044.0U CN219351275U (en) | 2022-12-15 | 2022-12-15 | Overcurrent and short-circuit protection circuit with current limiting and cutting-off functions |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202223369044.0U CN219351275U (en) | 2022-12-15 | 2022-12-15 | Overcurrent and short-circuit protection circuit with current limiting and cutting-off functions |
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| Publication Number | Publication Date |
|---|---|
| CN219351275U true CN219351275U (en) | 2023-07-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202223369044.0U Active CN219351275U (en) | 2022-12-15 | 2022-12-15 | Overcurrent and short-circuit protection circuit with current limiting and cutting-off functions |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN219351275U (en) |
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2022
- 2022-12-15 CN CN202223369044.0U patent/CN219351275U/en active Active
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