Overcurrent self-locking protection circuit and industrial equipment

Abstract

The utility model provides an over-current self-locking protection circuit and industrial equipment. The protection circuit comprises an over-current protection field effect transistor, a self-locking sub-circuit, a temperature compensation sub-circuit and an over-current detection sub-circuit. The self-locking sub-circuit is connected with the grid electrode of the overcurrent protection field effect transistor; the self-locking sub-circuit comprises a first transistor; a grid electrode of the overcurrent protection field effect transistor is used for receiving a driving signal, a source electrode of the overcurrent protection field effect transistor is connected with a base electrode of the first transistor, and a drain electrode of the overcurrent protection field effect transistor is connected with a load; the first end of the over-current detection sub-circuit is grounded, the second end of the over-current detection sub-circuit is connected with the source electrode of the over-current protection field effect transistor and the base electrode of the first transistor, and the over-current detection sub-circuit drives the first transistor to be switched on during over-current; at least one end of the temperature compensation sub-circuit is connected with the first transistor for compensating the temperature drift of the first transistor. According to the utility model, the damage of overcurrent to the circuit can be resisted, and the high-reliability anti-overcurrent performance can still be realized under the condition of temperature change.

Description

TECHNICAL FIELD

[0001] The embodiment of the utility model relates to the field of power electronics, especially relates to a overcurrent lockout protection circuit and industrial equipment. BACKGROUND

[0002] When overcurrent (current exceeds the predetermined maximum value) occurs unexpectedly in the circuit, it is easy to cause the damage of electronic devices in the circuit, and even can cause harm to the personal safety of the operator. The existing overcurrent protection circuit mainly has a triode and thyristor building scheme, or a triode and comparator building scheme.

[0003] The existing overcurrent protection circuit often has overcurrent lockout function, can avoid repeated action when overcurrent occurs, and ensures the safety of the circuit. However, the existing overcurrent protection circuit sets up a triode to realize overcurrent lockout, the temperature characteristic of the triode is poor, the risk of false triggering under temperature change is large, and the reliability of the overcurrent protection circuit is low. UTILITY MODEL CONTENTS

[0004] The embodiment of the utility model provides a overcurrent lockout protection circuit and industrial equipment, to solve the problem that the existing overcurrent protection circuit sets up a triode to realize overcurrent lockout, the temperature characteristic of the triode is poor, the risk of false triggering under temperature change is large, and the reliability of the overcurrent protection circuit is low.

[0005] In order to solve the above technical problems, the utility model is realized as follows:

[0006] Firstly, the utility model embodiment provides a overcurrent lockout protection circuit, including: overcurrent protection field effect tube, self-locking subcircuit, temperature compensation subcircuit, overcurrent detection subcircuit;

[0007] The self-locking subcircuit includes: first transistor;The self-locking subcircuit is connected with the gate of the overcurrent protection field effect tube, and is used to pull down the gate voltage of the overcurrent protection field effect tube when overcurrent occurs;

[0008] The gate of the overcurrent protection field effect tube is used to receive a driving signal, the source of the overcurrent protection field effect tube is connected with the base of the first transistor, and the drain of the overcurrent protection field effect tube is connected with a load;

[0009] The second end of the overcurrent detection subcircuit is connected with the source of the overcurrent protection field effect tube and the base of the first transistor respectively, and the overcurrent detection subcircuit drives the first transistor to be turned on when overcurrent occurs;

[0010] At least one end of the temperature compensation subcircuit is connected with the first transistor, and is used to compensate the temperature drift of the first transistor.

[0011] Optionally, further comprising: a control sub-circuit;

[0012] The control sub-circuit is connected with the gate of the over-current protection field effect tube and the drain of the over-current protection field effect tube respectively, and is used for turning on or turning off the connection between the driving circuit and the gate of the over-current protection field effect tube under the control of the detected voltage of the drain of the over-current protection field effect tube, wherein the driving circuit is used for outputting the driving signal to the gate of the over-current protection field effect tube.

[0013] Optionally, the self-locking sub-circuit further comprises: a second transistor, a first resistor and a second resistor.

[0014] The emitter of the second transistor is connected with the gate of the over-current protection field effect tube, the collector of the second transistor is connected with the first end of the first resistor, the second end of the first resistor is connected with the base of the first transistor and the source of the over-current protection field effect tube respectively, the base of the second transistor is connected with the first end of the second resistor, and the second end of the second resistor is connected with the collector of the first transistor; and the emitter of the first transistor is connected with a ground terminal.

[0015] The first transistor is an NPN transistor, and the second transistor is a PNP transistor.

[0016] Optionally, the temperature compensation sub-circuit is connected with the base of the first transistor.

[0017] Optionally, the temperature compensation sub-circuit comprises: a sixth resistor, a tenth resistor and a negative temperature coefficient thermistor (NTC) resistor.

[0018] The temperature compensation sub-circuit has a first branch and a second branch in parallel, and the first branch and the second branch are both connected with a ground terminal at one end and connected with the base of the first transistor at the other end.

[0019] The sixth resistor is located on the first branch, and the tenth resistor and the NTC resistor are located on the second branch and are connected in series.

[0020] Optionally, further comprising: a delay circuit.

[0021] The source of the over-current protection field effect tube is connected with the self-locking sub-circuit through the delay circuit.

[0022] Optionally, the delay circuit comprises: a third resistor and a first capacitor.

[0023] The first end of the third resistor is connected with the source of the over-current protection field effect tube, and the second end of the third resistor is connected with the first plate of the first capacitor and the self-locking sub-circuit respectively.

[0024] The second plate of the first capacitor is connected with the self-locking sub-circuit and the ground terminal respectively.

[0025] Optionally, further comprising: a low-pass filter circuit;

[0026] The low-pass filter circuit is connected with the gate of the over-current protection field effect tube and the self-locking sub-circuit respectively.

[0027] Optionally, the low-pass filter circuit comprises: a fifth resistor, a second capacitor;

[0028] The first end of the fifth resistor is connected with the first plate of the second capacitor and the gate of the over-current protection field effect tube respectively, and the second end of the fifth resistor is connected with the second plate of the second capacitor and the self-locking sub-circuit respectively.

[0029] In the second aspect, the utility model embodiment provides an industrial equipment, including the over-current self-locking protection circuit of any one in the first aspect.

[0030] In the utility model embodiment, over-current self-locking protection circuit, include: over-current protection field effect tube, self-locking sub-circuit, temperature compensation sub-circuit, over-current detection sub-circuit;Self-locking sub-circuit includes: first transistor;Self-locking sub-circuit is connected with the gate of over-current protection field effect tube, for when over-current, pull down the gate voltage of over-current protection field effect tube;The gate of over-current protection field effect tube is used for receiving drive signal, and the source of over-current protection field effect tube is connected with the base of first transistor, and the drain of over-current protection field effect tube is connected with load;Over-current detection sub-circuit first end ground, second end is connected with the source of over-current protection field effect tube and the base of first transistor respectively, and over-current detection sub-circuit drives first transistor to turn on when over-current;Temperature compensation sub-circuit at least one end is connected with first transistor, for compensating the temperature drift of first transistor, and the utility model embodiment over-current self-locking protection circuit can resist the harm of over-current to circuit, and by setting temperature compensation sub-circuit, the utility model embodiment over-current self-locking protection circuit still can realize high reliability anti over-current performance under temperature change. BRIEF DESCRIPTION OF DRAWINGS

[0031] Various other advantages and benefits will become apparent to those of ordinary skill in the art upon reading the following detailed description of the preferred embodiments with reference made to the accompanying drawings. The drawings are for purposes of illustration only and are not intended to limit the present utility. The same reference numerals in different drawings denote the same or similar components. In the drawings:

[0032] Figure 1 It is a layout schematic diagram of the utility model embodiment over-current self-locking protection circuit;

[0033] Figure 2The utility model discloses an embodiment of overcurrent self -locking protection circuit's layout schematic diagram of temperature compensation subcircuit.

[0034] Figure 3 It is voltage amplitude - time change schematic diagram. DETAILED DESCRIPTION

[0035] The technical scheme in the embodiments of the utility model will be clearly and completely described below with reference to the drawings in the utility model. Obviously, the described embodiments are part of the embodiments of the utility model and not all the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by the person skilled in the art without creative labor belong to the protection scope of the utility model.

[0036] The terms "first", "second" and the like in the embodiments of the utility model are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchanged under appropriate circumstances so that the embodiments of the utility model can be implemented in an order other than those illustrated or described here, and the objects distinguished by "first", "second" are usually a kind, and the number of objects is not limited, for example, the first object can be one or more. In addition, "or" in the embodiments of the utility model represents at least one of the connected objects. For example, "A or B" covers three schemes, namely, scheme one: including A and not including B; scheme two: including B and not including A; scheme three: including A and B. The character " / " generally represents that the front and rear associated objects are in an "or" relationship.

[0037] In the technical scheme of the embodiments of the utility model, "connection" or "connection" and similar words are not limited to physical or mechanical connection, but can include electrical connection.

[0038] In addition, the technical features involved in different embodiments of the utility model described below can be combined with each other as long as there is no conflict between them.

[0039] Please see Figure 1 The utility model discloses an embodiment of overcurrent self -locking protection circuit, comprising:

[0040] Overcurrent protection field effect tube Q3, self -locking subcircuit 100 (with dotted line frame selection), temperature compensation subcircuit 200, overcurrent detection subcircuit;

[0041] The self -locking subcircuit includes: first transistor Q2;The gate of overcurrent protection field effect tube Q3 is connected with self -locking subcircuit 100, and is used for pulling down the gate voltage of overcurrent protection field effect tube Q3 when overcurrent;

[0042] The gate of the overcurrent protection field effect tube Q3 is used for receiving a driving signal, the source of the overcurrent protection field effect tube Q3 is connected with the base of the first transistor Q2, and the drain of the overcurrent protection field effect tube Q3 is connected with a load;

[0043] The first end of the overcurrent detection sub-circuit is grounded, the second end is connected with the source of the overcurrent protection field effect tube Q3 and the base of the first transistor Q2 respectively, and the overcurrent detection sub-circuit drives the first transistor Q2 to be turned on when overcurrent occurs;

[0044] The temperature compensation sub-circuit 300 is connected with the first transistor Q2 at least at one end, and is used for compensating the temperature drift of the first transistor Q2.

[0045] Optionally, the overcurrent protection field effect tube Q3 can be a MOS tube in some embodiments of the utility model, and the overcurrent protection field effect tube Q3 can be an NMOS (English full name: N-Metal-Oxide-Semiconductor, Chinese meaning: N-type metal-oxide-semiconductor) transistor in some implementation modes. Of course, it can be understood that the above-mentioned overcurrent protection field effect tube Q3 can also be other possible devices, and the specific determination can be made according to the actual situation, for example: PMOS, junction field effect tube, etc., and the embodiments of the specification are not limited thereto.

[0046] In some embodiments, the self-locking sub-circuit can only include one transistor, or a plurality of transistors can be arranged to realize.

[0047] The first transistor Q2 can be a thyristor or a triode in some embodiments of the utility model. Of course, it can be understood that the above-mentioned first transistor Q2 can also be other possible devices, and the specific determination can be made according to the actual situation, and the embodiments of the specification are not limited thereto.

[0048] Optionally, the overcurrent self-locking protection circuit can further include a driving circuit in some embodiments of the utility model. The driving circuit is connected with the gate of the overcurrent protection field effect tube Q3, the driving circuit amplifies the switching signal after receiving the switching signal and applies the amplified switching signal (driving voltage) to the gate of the overcurrent protection field effect tube Q3, so as to control the gate voltage of the overcurrent protection field effect tube Q3 and control the turn-on or turn-off of the overcurrent protection field effect tube Q3. Specifically, when the driving voltage Vgs is greater than or equal to the turn-on threshold of the overcurrent protection field effect tube Q3, the overcurrent protection field effect tube Q3 is turned on, the load is powered on, and the circuit is normally operated; when the driving voltage Vgs is lower than the turn-on threshold of the overcurrent protection field effect tube Q3, the overcurrent protection field effect tube Q3 is turned off, and the load is disconnected from the circuit.

[0049] It should be noted that the drain of the overcurrent protection field effect tube Q3 is connected with the load, and the function includes:

[0050] 1) Realize current monitoring: The current flowing through the load can be directly monitored. When the load current exceeds the set threshold, the overcurrent detection subcircuit of the overcurrent protection field effect tube Q3 can detect this change and take appropriate protective measures. In the overcurrent protection circuit, field effect tubes are usually used as switches.

[0051] 2) Control current flow: When the drain of the overcurrent protection field effect tube Q3 is connected to the load, the overcurrent protection field effect tube Q3 can be turned on or off by controlling the gate voltage, thereby controlling the current flowing through the load. If the current exceeds the set value, the overcurrent protection field effect tube Q3 will be turned off, thereby cutting off the power supply to the load and preventing the occurrence of overcurrent conditions.

[0052] 3) Reduce power consumption: By connecting the overcurrent protection field effect tube Q3 to the load, the overcurrent protection field effect tube Q3 can work in a low power consumption state under normal working conditions. When the current is normal, the overcurrent protection field effect tube Q3 is in the on state, with almost no voltage drop, so the power consumption is low.

[0053] 4) Realize fast response: The switching speed of the overcurrent protection field effect tube Q3 is very fast, which can quickly cut off the current in the moment of current overload, thereby protecting the load and other circuit components. This fast response feature makes the overcurrent protection field effect tube Q3 able to effectively prevent damage.

[0054] 5) Simplify circuit design: The design of connecting the overcurrent protection field effect tube Q3 drain to the load simplifies the circuit, reduces additional components and complex control logic. In many applications, this design can effectively realize the overcurrent protection function.

[0055] 6) Improve reliability: By directly connecting the drain of the overcurrent protection field effect tube Q3 to the load, the reliability of the circuit can be improved. Any overcurrent condition can be quickly detected and responded to, reducing potential damage to the load.

[0056] In the embodiment of the utility model, the first transistor Q2 is a thyristor, and the first transistor Q2 is accurately selected, and the conduction of the first transistor Q2 is taken as the trigger condition of triggering the self-locking subcircuit 100 to pull down the gate voltage of the overcurrent protection field effect tube Q3. Specifically, after accurate selection, the conduction voltage of the first transistor Q2 is less than the voltage of the source of the overcurrent protection field effect tube Q3 when overcurrent occurs, and greater than the voltage of the source of the overcurrent protection field effect tube Q3 when the circuit normally operates, so that the trigger condition when overcurrent occurs is set.

[0057] In some embodiments of the utility model, the overcurrent detection subcircuit can be a circuit for pulling up the voltage of the base of the first transistor Q2 to the on voltage of the first transistor Q2 when overcurrent occurs. The overcurrent detection subcircuit can include: a fourth resistor R4, and the source of the overcurrent protection field effect transistor Q3 is connected to the ground through the fourth resistor R4. When overcurrent occurs, the current flowing through the overcurrent protection field effect transistor Q3 increases, the current flowing through the fourth resistor R4 increases, and the voltage drop of the fourth resistor R4 increases. When the voltage drop of the fourth resistor R4 is greater than the on voltage of the first transistor Q2 in the self-locking subcircuit 100, the first transistor Q2 is turned on, the self-locking subcircuit 100 is activated, the gate voltage of the overcurrent protection field effect transistor Q3 is pulled down, the overcurrent protection field effect transistor Q3 is turned off, and the load is disconnected from the circuit, thereby realizing overcurrent protection. Of course, it can be understood that the overcurrent detection subcircuit can also include other possible devices, such as another resistor, a capacitor, etc. in series. In addition, the overcurrent detection subcircuit can also use other devices that can produce corresponding voltage changes with the current change of the overcurrent protection field effect transistor Q3. The embodiments of the present application do not limit this.

[0058] It should be noted that the specific layout of the self-locking subcircuit 100 can be designed according to actual conditions. The setting of other electronic devices in the self-locking subcircuit 100 except the first transistor Q2 is not limited in the embodiments of the present application. Those skilled in the art can make many forms of self-locking subcircuit 100 without departing from the scope of the present application, which is within the scope of protection of the present application.

[0059] In practical applications, temperature changes can interfere with electronic devices in the self-locking subcircuit 100, especially transistors. Specifically, transistors exhibit negative temperature characteristics, that is, the on threshold decreases with increasing temperature, and the circuit operating current cannot be accurately set, which has the risk of misoperation at high temperatures. Therefore, the temperature rise easily causes the transistors in the self-locking subcircuit 100 to conduct at a low gate voltage, that is, the trigger voltage of the self-locking subcircuit 100 is reduced, and the self-locking subcircuit 100 can also act when the circuit is running normally, and the probability of mis-triggering of the self-locking subcircuit 100 is greatly increased.

[0060] Therefore, in the embodiments of the present application, at least one end of the temperature compensation subcircuit 300 is connected to the first transistor Q2, and the temperature compensation subcircuit 300 is used to compensate or adjust the voltage applied to the self-locking subcircuit 100 to compensate for the temperature drift of the first transistor Q2, thereby effectively reducing the probability of mis-triggering of the self-locking subcircuit 100 and ensuring safe and stable operation.

[0061] In the present embodiment, at least one end of the temperature compensation subcircuit 300 is connected to the first transistor Q2.

[0062] It should be noted that the connection can be that at least one end of the temperature compensation sub-circuit 300 is directly connected to the first transistor Q2 to form an electrical connection, or can be connected to the first transistor Q2 through a relay of a circuit or an electronic component, wherein the circuit or the electronic component can be determined according to actual conditions, and the embodiment of the present application does not limit the same.

[0063] In the embodiment, the temperature compensation sub-circuit 300 can use a temperature sensor (for example, a thermocouple or an RTD (Resistance Temperature Detector)) to monitor the temperature in real time, and compensate the temperature drift of the first transistor Q2 through feedback control.

[0064] In the embodiment of the present application, the overcurrent self-locking protection circuit can include: an overcurrent protection field effect transistor Q3, a self-locking sub-circuit 100, a temperature compensation sub-circuit 200, and an overcurrent detection sub-circuit; the self-locking sub-circuit includes: a first transistor Q2; the self-locking sub-circuit 100 is connected to the gate of the overcurrent protection field effect transistor Q3, and is used to pull down the gate voltage of the overcurrent protection field effect transistor Q3 when overcurrent occurs; the gate of the overcurrent protection field effect transistor Q3 is used to receive a driving signal, the source of the overcurrent protection field effect transistor Q3 is connected to the base of the first transistor Q2, and the drain of the overcurrent protection field effect transistor Q3 is connected to a load; the overcurrent detection sub-circuit has a first end connected to ground and a second end connected to the source of the overcurrent protection field effect transistor Q3 and the base of the first transistor Q2, respectively, and drives the first transistor Q2 to be turned on when overcurrent occurs; at least one end of the temperature compensation sub-circuit 300 is connected to the first transistor Q2, and is used to compensate the temperature drift of the first transistor Q2. The overcurrent self-locking protection circuit in the embodiment of the present application can resist the damage of overcurrent to the circuit, and through the temperature compensation sub-circuit 300, the overcurrent self-locking protection circuit in the embodiment of the present application can still achieve high-reliability overcurrent resistance performance under temperature change.

[0065] Optionally, in some embodiments of the present application, the overcurrent self-locking protection circuit can further include: a control sub-circuit;

[0066] The control sub-circuit is respectively connected to the gate of the overcurrent protection field effect transistor Q3 and the drain of the overcurrent protection field effect transistor Q3, and is used to turn on or turn off the connection between a driving circuit and the gate of the overcurrent protection field effect transistor Q3 under the control of the detected voltage of the drain of the overcurrent protection field effect transistor Q3, and the driving circuit is used to output the driving signal (i.e., a driving voltage Vgs) to the gate of the overcurrent protection field effect transistor Q3.

[0067] Please refer to Figure 1 as shown, Figure 1The feedback signal Vgs_F of the over-current protection field effect transistor Q3 obtained by the control sub-circuit is a voltage of a drain of the detected over-current protection field effect transistor Q3.

[0068] Please further refer to Figure 3 As shown in the figure, the feedback signal Vgs_F of the over-current protection field effect transistor Q3 is logically identical to the driving voltage Vgs output by the driving circuit to the over-current protection field effect transistor Q3 when the circuit is normally running. In this case, the control sub-circuit turns on the connection between the driving circuit and the gate of the over-current protection field effect transistor Q3, the gate voltage of the over-current protection field effect transistor Q3 is greater than or equal to the turn-on threshold of the over-current protection field effect transistor Q3, the over-current protection field effect transistor Q3 is turned on, the load is powered on, and the circuit is normally running.

[0069] In the embodiment, when the load current Iload suddenly increases (i.e. over-current occurs), the self-locking sub-circuit 100 acts, pulls down the gate voltage of the over-current protection field effect transistor Q3, the over-current protection field effect transistor Q3 is turned off, and the load current Iload is zero. In this case, the feedback signal Vgs_F becomes low, while the driving voltage Vgs output by the driving circuit to the over-current protection field effect transistor Q3 is still high, and the feedback signal Vgs_F is logically opposite to the driving voltage Vgs. The logically opposite feedback signal Vgs_F and the driving voltage Vgs trigger the control sub-circuit to act, turn off the connection between the driving circuit and the gate of the over-current protection field effect transistor Q3, and stop the driving circuit from outputting the driving voltage Vgs.

[0070] It should be noted that the determination of the level of the feedback signal Vgs_F and the driving voltage Vgs can be realized by a hardware circuit, for example, a voltage comparator. Of course, it can be understood that an MCU or an FPGA or other types of microprocessors can be used to determine by comparing time, and the specific determination can be determined according to actual conditions, and the embodiment of the present application is not limited in this regard.

[0071] In some embodiments of the utility model, optionally, referring to Figure 1 As shown in the figure, the self-locking sub-circuit 100 can further include a second transistor Q1, a first resistor R1, and a second resistor R2.

[0072] The emitter of the second transistor Q1 is connected with the gate of the over-current protection field effect transistor Q3, the collector of the second transistor Q1 is connected with the first end of the first resistor R1, the second end of the first resistor R1 is connected with the base of the first transistor Q2 and the source of the over-current protection field effect transistor Q3 respectively, the base of the second transistor Q1 is connected with the first end of the second resistor R2, and the second end of the second resistor R2 is connected with the collector of the first transistor Q2; and the emitter of the first transistor Q2 is connected with the ground.

[0073] The first transistor Q2 can be an NPN transistor, and the second transistor Q1 can be a PNP transistor.

[0074] In the embodiment of the utility model, when the voltage of the source of the overcurrent protection field effect tube Q3 is greater than the trigger voltage of the self-locking sub-circuit 100 (that is, overcurrent occurs), the first transistor Q2 in the self-locking sub-circuit 100 is turned on, the second transistor Q1 is turned on, the first resistor R1 and the second resistor R2 are powered on, the first resistor R1 and the second resistor R2 form a voltage division on the gate voltage of the overcurrent protection field effect tube Q3, pull down the gate voltage below the conduction threshold, and turn off the overcurrent protection field effect tube Q3, and the load is disconnected from the circuit.

[0075] The circuit design of the self-locking sub-circuit 100 is simple and efficient, and can effectively ensure the safety of the load under overcurrent condition.

[0076] In some embodiments of the utility model, optionally, as shown in Figure 1 The temperature compensation sub-circuit 200 is connected with the base of the first transistor Q2, can offset the temperature drift effect of the first transistor Q2, ensure the stability of the trigger voltage, reduce the false trigger probability of the self-locking sub-circuit 100, and ensure safe and stable operation.

[0077] In some embodiments of the utility model, as shown in Figure 1 and Figure 2 The temperature compensation sub-circuit 200 can include a sixth resistor R6, a tenth resistor R10 and a negative temperature coefficient thermistor NTC resistor.

[0078] The temperature compensation sub-circuit 200 has a first branch and a second branch in parallel, one end of the first branch and the second branch is connected with the ground terminal, and the other end is connected with the base of the first transistor Q2.

[0079] The sixth resistor R6 is located on the first branch, and the tenth resistor R10 and the NTC resistor are located on the second branch and are connected in series.

[0080] The NTC resistor is used for temperature compensation, the tenth resistor R10 is used for adjusting the actual resistance range of the circuit, avoiding the small resistance of the NTC resistor under high temperature, and the sixth resistor R6 is used for ensuring that the first transistor Q2 (triode) can be reliably turned off when the NTC resistor or the tenth resistor R10 fails, preventing the circuit from malfunctioning.

[0081] The temperature compensation principle is described in detail in the following embodiments:

[0082] The on voltage Vbe of the first transistor Q2 is negative temperature coefficient, and if no compensation is performed, the overcurrent threshold of the circuit will change with temperature. Vbe at 25 DEG C is denoted as Vbe(25 DEG C), and the operating voltage of the first transistor Q2 at different temperatures Temp is:

[0083] Vbe(Temp) = Vbe(25 DEG C) * K;

[0084] When Temp = 25 DEG C, K = 1; when T > 25, K < 1; and when T < 25, K > 1.

[0085] If there is no temperature compensation circuit, the relationship between the operating current Ioc (the current corresponding to the trigger voltage) and Temp is:

[0086] Ioc(Temp) = Vbe(Temp) / R4 * K;

[0087] The temperature compensation sub-circuit 200 can adjust the proportionality coefficient of the voltage drop on the fourth resistor R4 between the b-e (base-emitter) of the first transistor Q2 according to temperature change. The higher the temperature, the smaller the proportionality coefficient, which requires a larger current to trigger the overcurrent protection, thereby offsetting the temperature drift of Vbe, so that Ioc is basically constant in the full temperature range. The temperature compensation circuit introduces a compensation coefficient C in the above formula, and the operating current with the temperature compensation circuit is:

[0088] Ioc(Temp) = Vbe(Temp) / R4 * K * C;

[0089] The temperature compensation coefficient C offsets the temperature drift K of the first transistor Q2 itself, so that Vbe(Temp) * K * C has basically the same product at different temperatures, so that the trigger voltage remains stable at different temperatures.

[0090] In the embodiments of the utility model, the electronic device layout of the temperature compensation sub-circuit 200 is simple and reliable, and the temperature drift effect of the first transistor Q2 can be offset, the trigger voltage is stable, the probability of false triggering of the self-locking sub-circuit 100 is reduced, and safe and stable operation is ensured.

[0091] In some embodiments of the utility model, the overcurrent self-locking protection circuit can further include a delay circuit.

[0092] The source of the overcurrent protection field effect transistor Q3 is connected to the self-locking sub-circuit 100 through the delay circuit.

[0093] The utility model discloses an embodiment through setting up delay circuit control circuit action time, in addition, the setting of delay circuit also prevented the circuit false action caused by external interference or circuit parasitic element existence. Transistor has certain overcurrent resistance ability, therefore only needs overcurrent action experiment in MOS tube capacity range. Through reasonable selection delay circuit parameter, ensure that circuit does not false action under the condition of protecting MOS tube, improve circuit reliability.

[0094] Optionally, in some embodiments of the utility model, referring to Figure 1 The delay circuit can include a third resistor R3 and a first capacitor C1.

[0095] The first end of the third resistor R3 is connected to the source of the overcurrent protection field effect transistor Q3, and the second end of the third resistor R3 is connected to the first plate of the first capacitor C1 and the self-locking sub-circuit 100, respectively.

[0096] The second plate of the first capacitor C1 is connected to the self-locking sub-circuit 100 and the ground terminal, respectively.

[0097] In the embodiment of the utility model, the delay circuit is composed of the third resistor R3 and the first capacitor C1, which is simple and reliable in structure, can effectively reduce the damage risk of the circuit caused by the instantaneous current being too high when overcurrent occurs, and ensures the safety and stability of the circuit.

[0098] Optionally, in some embodiments of the utility model, the temperature compensation sub-circuit 200 can also be a temperature sensing resistor connected in series between the third resistor R3 and the first transistor Q2.

[0099] Optionally, in some embodiments of the utility model, referring to Figure 1 The overcurrent self-locking protection circuit further includes a low-pass filter circuit, and the low-pass filter circuit is connected to the gate of the overcurrent protection field effect transistor Q3 and the self-locking sub-circuit 100, respectively.

[0100] The utility model discloses an embodiment of setting up low-pass filter circuit selectively attenuates high-frequency signal, ensures the stable operation of overcurrent self-locking protection circuit.

[0101] Optionally, in some embodiments of the utility model, referring to Figure 1 The low-pass filter circuit can include a fifth resistor R5 and a second capacitor C2.

[0102] The first end of the fifth resistor R5 is connected to the first plate of the second capacitor C2 and the gate of the overcurrent protection field effect transistor Q3, respectively, and the second end of the fifth resistor R5 is connected to the second plate of the second capacitor C2 and the self-locking sub-circuit 100, respectively.

[0103] It should be noted that the fifth resistor R5 is the pull-up resistor of the second transistor Q1, and the fifth resistor R5 and the second capacitor C2 constitute a low-pass filter circuit to filter out interference.

[0104] In the embodiment of the utility model, the low-pass filter circuit is constituted by the fifth resistor R5 and the second capacitor C2, which is simple and reliable in structure, selectively attenuates high-frequency signals, and ensures stable operation of the overcurrent self-locking protection circuit.

[0105] The embodiment of the utility model provides an industrial equipment, including any kind of overcurrent self-locking protection circuit of the utility model embodiment. Based on the overcurrent self-locking protection circuit of the utility model embodiment, the harm caused by overcurrent to the load is reduced when the load overflows, and the industrial equipment of the utility model embodiment has excellent and high-reliability overcurrent resistance performance, and can be operated stably for a long time.

[0106] The embodiments of the utility model are described above in combination with the drawings, but the utility model is not limited to the specific embodiments described above, and the specific embodiments described above are only illustrative but not restrictive, and those skilled in the art can make many forms under the inspiration of the utility model without departing from the scope of the utility model and the protection scope of the claims, which all belong to the protection scope of the utility model.

Claims

1. An overcurrent self-locking protection circuit, characterized in that, include: Overcurrent protection MOSFET, self-locking sub-circuit, temperature compensation sub-circuit, overcurrent detection sub-circuit; The self-locking circuit includes: a first transistor; the self-locking circuit is connected to the gate of the overcurrent protection field-effect transistor and is used to pull down the gate voltage of the overcurrent protection field-effect transistor during overcurrent. The gate of the overcurrent protection field-effect transistor is used to receive the drive signal, the source of the overcurrent protection field-effect transistor is connected to the base of the first transistor, and the drain of the overcurrent protection field-effect transistor is connected to the load. The first terminal of the overcurrent detection sub-circuit is grounded, and the second terminal is connected to the source of the overcurrent protection field-effect transistor and the base of the first transistor, respectively. When there is an overcurrent, the overcurrent detection sub-circuit drives the first transistor to conduct. At least one end of the temperature compensation sub-circuit is connected to the first transistor to compensate for the temperature drift of the first transistor.

2. The overcurrent self-locking protection circuit according to claim 1, characterized in that, Also includes: Control sub-circuit; The control sub-circuit is connected to the gate and drain of the overcurrent protection field-effect transistor, respectively, and is used to turn on or off the connection between the drive circuit and the gate of the overcurrent protection field-effect transistor under the control of the detected voltage at the drain of the overcurrent protection field-effect transistor. The drive circuit is used to output the drive signal to the gate of the overcurrent protection field-effect transistor.

3. The overcurrent self-locking protection circuit according to claim 1, characterized in that, The self-locking sub-circuit further includes: a second transistor, a first resistor, and a second resistor; The emitter of the second transistor is connected to the gate of the overcurrent protection field-effect transistor, the collector of the second transistor is connected to the first end of the first resistor, the second end of the first resistor is connected to the base of the first transistor and the source of the overcurrent protection field-effect transistor, the base of the second transistor is connected to the first end of the second resistor, and the second end of the second resistor is connected to the collector of the first transistor; the emitter of the first transistor is connected to the ground terminal. The first transistor is an NPN transistor, and the second transistor is a PNP transistor.

4. The overcurrent self-locking protection circuit according to claim 1, characterized in that, The temperature compensation sub-circuit is connected to the base of the first transistor.

5. The overcurrent self-locking protection circuit according to claim 4, characterized in that, The temperature compensation sub-circuit includes: a sixth resistor, a tenth resistor, and a negative temperature coefficient thermistor (NTC resistor); The temperature compensation sub-circuit has a first branch and a second branch connected in parallel. One end of the first branch and the second branch are connected to the ground terminal, and the other end is connected to the base of the first transistor. The sixth resistor is located on the first branch, and the tenth resistor and the NTC resistor are located on the second branch and connected in series.

6. The overcurrent self-locking protection circuit according to claim 1, characterized in that, Also includes: Delay circuit; The source of the overcurrent protection field-effect transistor is connected to the self-locking sub-circuit through the delay circuit.

7. The overcurrent self-locking protection circuit according to claim 6, characterized in that, The delay circuit includes: a third resistor and a first capacitor; The first end of the third resistor is connected to the source of the overcurrent protection field-effect transistor, and the second end of the third resistor is connected to the first plate of the first capacitor and the self-locking sub-circuit, respectively. The second plate of the first capacitor is connected to the self-locking sub-circuit and the ground terminal, respectively.

8. The overcurrent self-locking protection circuit according to claim 1, characterized in that, Also includes: Low-pass filter circuit; The low-pass filter circuit is connected to the gate of the overcurrent protection field-effect transistor and the self-locking sub-circuit, respectively.

9. The overcurrent self-locking protection circuit according to claim 8, characterized in that, The low-pass filter circuit includes: a fifth resistor and a second capacitor; The first end of the fifth resistor is connected to the first plate of the second capacitor and the gate of the overcurrent protection field-effect transistor, respectively, and the second end of the fifth resistor is connected to the second plate of the second capacitor and the self-locking circuit, respectively.

10. An industrial device, characterized in that, Includes the overcurrent self-locking protection circuit as described in any one of claims 1 to 9.

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