Overcurrent protection circuit and device
Through the combination of resistive sampling circuit, transistor self-locking circuit and MOS tube control circuit, the MOS tube disconnection is controlled by transistor conduction voltage, which solves the problem of traditional overcurrent protection being susceptible to signal interference, and improves the reliability of overcurrent protection and accuracy.
Patent Information
- Application Number
- CN202323368000.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-11
- Publication Date
- 2024-12-10
- Estimated Expiration
- 2033-12-11
AI Technical Summary
The traditional overcurrent protection method is easily disturbed by signal, resulting in low reliability of overcurrent protection.
The overcurrent protection circuit including a resistive sampling circuit, a transistor self-locking circuit and a MOS tube control circuit is adopted. The self-locking voltage is generated by the transistor conduction voltage, and the MOS tube is controlled to be disconnected, thereby achieving overcurrent protection of the external load circuit.
Improves the reliability of overcurrent protection, avoids signal interference, reduces maintenance costs and improves protection accuracy.
Smart Images
Figure CN222147148U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of overcurrent protection, in particular to an overcurrent protection circuit and a device. Background Art
[0002] With the development of society, electrical equipment is being used more and more in daily life. While users hope to ensure the normal operation of electrical equipment, they also pay attention to the protection of electrical equipment. The common protection method for electrical equipment is overcurrent protection, which also puts higher requirements on the overcurrent protection of electrical equipment.
[0003] The traditional overcurrent protection method is to control the on and off of the switch by using resistor sampling to realize overcurrent detection for the comparator circuit. This overcurrent protection method has a great defect that the comparator circuit is easily susceptible to signal interference. Therefore, a new overcurrent protection method is urgently needed to improve the reliability of overcurrent protection. Utility Model Content
[0004] The main purpose of the utility model is to propose an overcurrent protection circuit and a device, aiming at the problem of how to improve the reliability of overcurrent protection.
[0005] To achieve the above object, the utility model provides an overcurrent protection circuit, which includes a resistor sampling circuit, a transistor self-locking circuit, a MOS tube control circuit and a power conversion circuit;
[0006] The MOS tube control circuit is respectively connected to the resistance sampling circuit, the triode self-locking circuit and the power conversion circuit, the resistance sampling circuit is connected to the triode self-locking circuit, and the MOS tube control circuit is connected to the external load circuit;
[0007] Among them, the resistance sampling circuit is used to output the transistor conduction voltage when the external load circuit is overcurrent, the transistor self-locking circuit is used to generate a self-locking voltage based on the transistor conduction voltage, and the MOS tube control circuit is used to perform overcurrent protection on the external load circuit based on the self-locking voltage.
[0008] Optionally, the MOS tube control circuit includes an N-type MOS tube, the drain of the N-type MOS tube is connected to the external load circuit, the source of the N-type MOS tube is connected to the resistance sampling circuit, and the gate of the N-type MOS tube is connected to the transistor self-locking circuit and the power conversion circuit.
[0009] Optionally, the resistance sampling circuit includes at least one sampling resistor and a first resistor, the first end of the sampling resistor is respectively connected to the source of the N-type MOS tube and the first end of the first resistor, the second end of the sampling resistor is connected to the system power ground, and the second end of the first resistor is connected to the transistor self-locking circuit.
[0010] Optionally, the overcurrent protection circuit further includes a first power supply and a second power supply, the first power supply is connected to the transistor self-locking circuit and the power conversion circuit respectively, and the second power supply is connected to the power conversion circuit.
[0011] Optionally, the overcurrent protection circuit further includes a side branch circuit, and the side branch circuit includes a second resistor, a third resistor and a fourth resistor;
[0012] The first power supply is respectively connected to the first end of the second resistor and the first end of the third resistor, the transistor self-locking circuit is respectively connected to the second end of the second resistor and the second end of the third resistor, the first end of the fourth resistor is respectively connected to the gate of the N-type MOS tube, the transistor self-locking circuit and the power conversion circuit, and the second end of the fourth resistor is connected to the system power ground.
[0013] Optionally, the transistor self-locking circuit includes an NPN transistor and a diode, the emitter of the NPN transistor is connected to the system power ground, the base of the NPN transistor is connected to the second end of the first resistor, the collector of the NPN transistor is respectively connected to the cathode of the diode and the second end of the second resistor, and the anode of the diode is respectively connected to the gate of the N-type MOS tube and the first end of the fourth resistor.
[0014] Optionally, the transistor self-locking circuit also includes a PNP transistor, the collector of the PNP transistor is connected to the second end of the first resistor, the base of the PNP transistor is connected to the collector of the NPN transistor, and the emitter of the PNP transistor is connected to the second end of the third resistor.
[0015] Optionally, the power conversion circuit includes a power conversion chip, a capacitor and an output circuit, and the power conversion chip includes at least a first pin, a second pin, a third pin, a fourth pin and a fifth pin;
[0016] The first pin is connected to the third pin and then to the system power ground, the second pin is connected to the second power supply, the fourth pin is connected to the output circuit, the fifth pin is respectively connected to the first power supply and the first end of the capacitor, and the second end of the capacitor is connected to the system power ground.
[0017] Optionally, the output circuit includes at least one output resistor, a first end of the output resistor is connected to the fourth pin, and a second end of the output resistor is connected to a first end of the fourth resistor.
[0018] In addition, the present application also provides an overcurrent protection device, which includes the overcurrent protection circuit as described above.
[0019] The present application provides an overcurrent protection circuit, which includes a resistor sampling circuit, a transistor self-locking circuit, a MOS tube control circuit and a power conversion circuit; the MOS tube control circuit is respectively connected to the resistor sampling circuit, the transistor self-locking circuit and the power conversion circuit, the resistor sampling circuit is connected to the transistor self-locking circuit, and the MOS tube control circuit is connected to an external load circuit; wherein the resistor sampling circuit is used to output a transistor conduction voltage when the external load circuit has an overcurrent, the transistor self-locking circuit is used to generate a self-locking voltage based on the transistor conduction voltage, and the MOS tube control circuit is used to perform overcurrent protection on the external load circuit based on the self-locking voltage. When the external load circuit has an overcurrent, the resistor sampling circuit outputs the transistor conduction voltage, and then the transistor conduction voltage is used to control the transistor self-locking circuit to generate a self-locking voltage, and finally the self-locking voltage controls the MOS tube control circuit to self-lock (disconnect), and then the external load circuit is protected from overcurrent, thereby avoiding the comparator circuit in the prior art being easily interfered by signals, thereby causing the overcurrent protection reliability to be low. This overcurrent protection circuit can generate a self-locking voltage by controlling the transistor self-locking circuit when there is an overcurrent, and finally the self-locking voltage controls the MOS tube control circuit to self-lock (disconnect), and then the external load circuit is protected from overcurrent, thereby improving the reliability of the overcurrent protection. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] Figure 1 It is a structural schematic diagram of the overcurrent protection circuit of the utility model;
[0021] Figure 2 It is another structural schematic diagram of the overcurrent protection circuit of the utility model;
[0022] Figure 3 A circuit connection diagram of an overcurrent protection circuit of the utility model;
[0023] Figure 4 This is a schematic diagram of the working process of the overcurrent protection circuit of the utility model;
[0024] Figure 5 The figure is a schematic diagram of a scenario of the overcurrent protection circuit of the utility model.
[0025] Description of Figure Numbers:
[0026]
[0027]
[0028] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION
[0029] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.
[0030] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.
[0031] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.
[0032] In this application, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.
[0033] In addition, in this application, descriptions such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In addition, the technical solutions between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this application.
[0034] The utility model provides an overcurrent protection circuit, referring to Figure 1A schematic diagram of the structure of an overcurrent protection circuit, the overcurrent protection circuit includes a resistor sampling circuit 20, a transistor self-locking circuit 30, a MOS tube control circuit 10 and a power conversion circuit 40;
[0035] The MOS tube control circuit 10 is connected to the resistance sampling circuit 20, the transistor self-locking circuit 30 and the power conversion circuit 40 respectively, the resistance sampling circuit 20 is connected to the transistor self-locking circuit 30, and the MOS tube control circuit 10 is connected to the external load circuit 200;
[0036] Among them, the resistance sampling circuit 20 is used to output the transistor conduction voltage when the external load circuit 200 is overcurrent, the transistor self-locking circuit 30 is used to generate a self-locking voltage based on the transistor conduction voltage, and the MOS tube control circuit 10 is used to perform overcurrent protection on the external load circuit 200 based on the self-locking voltage.
[0037] With the development of electrical equipment, the demand for overcurrent protection of electrical equipment has become more and more important. Commonly used hardware overcurrent protection circuit designs generally include the following two methods:
[0038] Method 1: Use fuses directly to protect the circuit;
[0039] Method 2: Use resistor sampling to implement overcurrent detection for the comparator circuit to control the on and off of the switch.
[0040] The designs of the above two overcurrent protection circuits have at least the following defects. Regarding method one: if a non-recoverable fuse is used, it is easy to be damaged and the maintenance cost is high; if a recoverable fuse is used, the action response is slow and the price is expensive. Regarding method two: if a comparator circuit design is adopted, the signal interference degree must be high, that is, the circuit itself has strong anti-interference ability. Furthermore, based on the shortcomings of the commonly used hardware overcurrent protection circuit, the overcurrent protection circuit of the present application is proposed. On the one hand, it can be realized by using basic components and does not require multiple maintenance. On the other hand, it does not require high anti-interference ability, thereby improving the reliability of overcurrent protection.
[0041] In this embodiment, the overcurrent protection circuit is composed of a resistor sampling circuit 20, a transistor self-locking circuit 30, a MOS tube control circuit 10 and a power conversion circuit 40. Because the MOS tube control circuit 10 is actually connected to the external load circuit 200 to be protected from overcurrent, the external load circuit 200 can be a simple motor control circuit, a lighting circuit, etc. Then, the external load circuit 200 is turned on by the MOS tube control circuit 10 to work (when there is no overcurrent), that is, the switch tube in the MOS tube control circuit 10 and the external load circuit 200 form a normal power supply circuit. On the contrary, when the external load circuit 200 has an overcurrent, the current flows to the resistor sampling circuit 20 through the MOS tube control circuit 10. At this time, because the current received by the resistor sampling circuit 20 reaches the threshold value (user-defined value), the transistor in the transistor self-locking circuit 30 will be turned on, that is, the resistor sampling circuit 20 is in the external When the external load circuit 200 is overcurrent, the transistor conduction voltage is output. The transistor conduction voltage refers to the voltage that drives the transistor to conduct, which is generally 0.7V. Then, after the transistor is turned on, a self-locking voltage is generated, and then based on the self-locking voltage, the switch tube in the MOS tube control circuit 10 is controlled to be turned off, and then the switch tube in the MOS tube control circuit 10 is disconnected from the normal power supply circuit of the external load circuit 200, so as to realize overcurrent protection of the external load circuit 200. The self-locking voltage refers to the voltage that controls the switch tube in the MOS tube control circuit 10 to be turned off, which can refer to a low level. That is, the entire working principle: when the MOS tube is turned on (the external load circuit 200 is working), the current flows through the sampling resistor in the resistance sampling circuit 20. As the current increases, when the current reaches a certain value (overcurrent point), the voltage on the sampling resistor in the resistance sampling circuit 20 causes the transistor to conduct, thereby realizing the circuit self-locking function and preventing overcurrent from damaging other circuit components. As a result, it will not be affected by internal signal interference, thereby improving the reliability of overcurrent protection. In addition, the entire overcurrent protection circuit does not need to replace the fuse or require a longer response time, thereby reducing the cost of use and improving the accuracy of protection.
[0042] For example, refer to Figure 2 , Figure 2This is another structural schematic diagram of the overcurrent protection circuit of the utility model. When the circuit to be overcurrent protected (hereinafter described as the external load circuit 200) does not have an overcurrent phenomenon, the MOS tube control circuit 10 drain output current makes the entire external load circuit 200 work normally. When the external load circuit 200 has an overcurrent (user-defined overcurrent current value), the overcurrent current of the external load circuit 200 is output to the resistor sampling circuit 20, thereby controlling the transistor in the transistor self-locking circuit 30 to be turned on, and the switch tube in the self-locking MOS tube control circuit 10 (disconnecting the switch tube), and then the external load circuit 200 disconnects the line after the overcurrent occurs to protect the external load circuit 200. At this time, the function of the power conversion circuit 40 is to convert the input 3.3V voltage into a 5V voltage, thereby ensuring the normal operation of the entire overcurrent protection circuit, and then the external load circuit 200 is protected from overcurrent by the overcurrent protection circuit to improve the reliability of the overcurrent protection.
[0043] The present embodiment provides an overcurrent protection circuit, which includes a resistor sampling circuit, a transistor self-locking circuit, a MOS tube control circuit and a power conversion circuit; the MOS tube control circuit is respectively connected to the resistor sampling circuit, the transistor self-locking circuit and the power conversion circuit, the resistor sampling circuit is connected to the transistor self-locking circuit, and the MOS tube control circuit is connected to an external load circuit; wherein the resistor sampling circuit is used to output a transistor conduction voltage when the external load circuit is overcurrent, the transistor self-locking circuit is used to generate a self-locking voltage based on the transistor conduction voltage, and the MOS tube control circuit is used to perform overcurrent protection on the external load circuit based on the self-locking voltage. When the external load circuit has an overcurrent, the resistor sampling circuit outputs the transistor conduction voltage, and then the transistor conduction voltage is used to control the transistor self-locking circuit to generate a self-locking voltage, and finally the self-locking voltage controls the MOS tube control circuit to self-lock (disconnect), and then the external load circuit is protected from overcurrent, thereby avoiding the comparator circuit in the prior art being easily interfered by signals, thereby causing the overcurrent protection reliability to be low. This overcurrent protection circuit can generate a self-locking voltage by controlling the transistor self-locking circuit when there is an overcurrent, and finally the self-locking voltage controls the MOS tube control circuit to self-lock (disconnect), and then the external load circuit is protected from overcurrent, thereby improving the reliability of the overcurrent protection.
[0044] Further, in another embodiment of the overcurrent protection circuit of the present application, referring to Figure 3 , Figure 4The MOS tube control circuit 10 includes an N-type MOS tube M, the drain of the N-type MOS tube M is connected to the external load circuit 200, the source of the N-type MOS tube M is connected to the resistance sampling circuit 20, and the gate of the N-type MOS tube M is connected to the transistor self-locking circuit 30 and the power conversion circuit 40.
[0045] Specifically, the resistance sampling circuit 20 includes at least one sampling resistor RX and a first resistor R1, the first end of the sampling resistor RX is respectively connected to the source of the N-type MOS tube M and the first end of the first resistor R1, the second end of the sampling resistor RX is connected to the system power ground, and the second end of the first resistor R1 is connected to the transistor self-locking circuit 30.
[0046] In this embodiment, the N-type MOS tube M in the MOS tube control circuit 10 is used to control whether the external load circuit 200 performs normal operation. For example, when there is no overcurrent, the N-type MOS tube M is closed, and the external load circuit 200 forms a normal power supply circuit to work. When there is overcurrent, the N-type MOS tube M is disconnected, and the normal power supply circuit of the external load circuit 200 is disconnected and stops working, that is, DO3 in the figure connects the external load circuit 200. When the entire external load circuit 200 starts to work, the current of the external load circuit 200 will be detected all the time, and the current of the external load circuit 200 will flow to the sampling resistor RX through the drain of the N-type MOS tube M and the source of the N-type MOS tube M. The sampling resistor RX can be a larger resistor or a plurality of small resistors in parallel. Since the other end of the sampling resistor RX is grounded, it can be determined whether the current at this time is overcurrent based on the sampling resistor RX, and then after determining that the current is overcurrent, the transistor self-locking circuit 30 is driven to control the N-type MOS tube M to turn off, thereby protecting the external load circuit 200 for overcurrent protection, so as to achieve overcurrent protection of the external load circuit 200.
[0047] Furthermore, in another embodiment of the overcurrent protection circuit of the present application, the overcurrent protection circuit also includes a first power supply DO1 and a second power supply DO2, the first power supply DO1 is respectively connected to the transistor self-locking circuit 30 and the power conversion circuit 40, and the second power supply DO2 is connected to the power conversion circuit 40.
[0048] Specifically, the overcurrent protection circuit further includes a side branch circuit, and the side branch circuit includes a second resistor R2, a third resistor R3 and a fourth resistor R4;
[0049] The first power supply DO1 is respectively connected to the first end of the second resistor R2 and the first end of the third resistor R3, the transistor self-locking circuit 30 is respectively connected to the second end of the second resistor R2 and the second end of the third resistor R3, the first end of the fourth resistor R4 is respectively connected to the gate M of the N-type MOS tube, the transistor self-locking circuit 30 and the power conversion circuit 40, and the second end of the fourth resistor R4 is connected to the system power ground.
[0050] Specifically, the transistor self-locking circuit 30 includes an NPN transistor Q1 and a diode D1, the emitter of the NPN transistor Q1 is connected to the system power ground, the base of the NPN transistor Q1 is connected to the second end of the first resistor R1, the collector of the NPN transistor Q1 is respectively connected to the cathode of the diode D1 and the second end of the second resistor R2, and the anode of the diode D1 is respectively connected to the gate of the N-type MOS tube M and the first end of the fourth resistor R4.
[0051] Specifically, the transistor self-locking circuit 30 also includes a PNP transistor Q2, the collector of the PNP transistor Q2 is connected to the second end of the first resistor R1, the base of the PNP transistor Q2 is connected to the collector of the NPN transistor Q1, and the emitter of the PNP transistor Q2 is connected to the second end of the third resistor R3.
[0052] In this embodiment, when the external load circuit 200 is not overcurrent, the entire transistor self-locking circuit 30 will not be turned on to work. Only when the external load circuit 200 is overcurrent, the voltage across the sampling resistor RX remains unchanged (the overcurrent threshold of the current is set by the user and can be achieved by changing the resistance of the sampling resistor RX). Due to the increase in current, the voltage reaches the transistor turn-on voltage, thereby turning on the NPN transistor Q1, and the collector of the NPN transistor Q1 and the emitter of the NPN transistor Q1 are connected to the ground, thereby making the base of the PNP transistor Q2 and the cathode of the diode D1 low voltage. At this time, the diode D1 is turned on to make the gate of the N-type MOS tube M low level, and then the N-type MOS tube M is turned off to achieve overcurrent protection. The use of the diode here can prevent the first power supply DO1 from driving the N-type MOS tube M. On the other hand, since the base of the PNP-type transistor Q2 is at a low level, the PNP-type transistor Q2 is turned on, so that the base of the NPN-type transistor Q1 is always at a high level, thereby achieving self-locking, that is, the external load circuit 200 will not automatically recover after a short-term overcurrent, thereby causing the N-type MOS tube M to repeat on and off control, thereby avoiding damage to the N-type MOS tube M. At this time, a switch can be connected to the base of the NPN-type transistor Q1 to a low level, so that the user can restore the normal operation of the external load circuit 200 by himself, thereby achieving overcurrent protection while ensuring the service life of components in the overcurrent protection circuit.
[0053] For example, refer to Figure 4 , Figure 4 This is a schematic diagram of the working process of the overcurrent protection circuit of the utility model. By setting the overcurrent threshold in advance (i.e., selecting the sampling resistor value corresponding to different current thresholds), the power is turned on after setting, and the MOS tube turns on the external pull-up output under normal working conditions of the external load circuit 200. When the output is overcurrent, that is, the sampling resistor voltage is ≥0.7V, the overcurrent protection will be triggered, and the transistor will start to act (i.e., the transistor works so that the driving end of the MOS tube, i.e., the gate, is connected to a low level, and the MOS tube is turned off at this time), and finally the circuit self-locks for protection, thereby achieving overcurrent protection. Further, refer to Figure 5 , Figure 5 This is a schematic diagram of a scenario of the overcurrent protection circuit of the utility model. In the case of an N-type MOS tube M, the resistance sampling circuit 20 determines that the external load circuit 200 is overcurrent (the sampling resistor in the resistance sampling circuit 20 reaches the voltage threshold for turning on the transistor, such as 0.7V, and the dotted arrow in the figure is the direction of the control flow), and then controls the transistor self-locking circuit 30 to turn on the transistor, and then controls the MOS tube to be disconnected (the dotted line is the previous state, the solid line is the current state, and the current state is that the MOS tube is disconnected). At this time, the entire external load circuit 200 is disconnected and does not work normally, thereby achieving overcurrent protection for the external load circuit 200.
[0054] Further, in another embodiment of the overcurrent protection circuit of the present application, the power conversion circuit 40 includes a power conversion chip U1, a capacitor C and an output circuit, and the power conversion chip U1 includes at least a first pin, a second pin, a third pin, a fourth pin and a fifth pin;
[0055] The first pin is connected to the third pin and then to the system power ground, the second pin is connected to the second power supply DO2, the fourth pin is connected to the output circuit, the fifth pin is respectively connected to the first power supply DO1 and the first end of the capacitor C, and the second end of the capacitor C is connected to the system power ground.
[0056] Specifically, the output circuit includes at least one output resistor RN, a first end of the output resistor RN is connected to the fourth pin, and a second end of the output resistor RN is connected to a first end of the fourth resistor R4.
[0057] In this embodiment, the function of the power conversion circuit 40 is to provide a driving voltage for the N-type MOS tube M, thereby ensuring the normal operation of the N-type MOS tube M. The function of the output resistor RN is to ensure that the output voltage of the power conversion circuit 40 passes through the power of the transistor self-locking circuit 30, and by selecting two 0603 models of 200 ohms, a larger resistance value can also be directly selected to ensure the normal operation of the transistor self-locking circuit 30 and the N-type MOS tube M, so as to achieve overcurrent protection.
[0058] In addition, the present application also provides an overcurrent protection device, which includes the above-mentioned overcurrent protection circuit.
[0059] The above description is only a preferred embodiment of the present application, and does not limit the patent scope of the present application. All equivalent structural changes made by using the contents of the present application specification and drawings under the inventive concept of the present application, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present application.
Claims
1. An overcurrent protection circuit, characterized in that: The overcurrent protection circuit includes a resistance sampling circuit, a transistor self-locking circuit, a MOS tube control circuit and a power conversion circuit; The MOS tube control circuit is respectively connected to the resistance sampling circuit, the triode self-locking circuit and the power conversion circuit, the resistance sampling circuit is connected to the triode self-locking circuit, and the MOS tube control circuit is connected to the external load circuit; Among them, the resistance sampling circuit is used to output the transistor conduction voltage when the external load circuit is overcurrent, the transistor self-locking circuit is used to generate a self-locking voltage based on the transistor conduction voltage, and the MOS tube control circuit is used to perform overcurrent protection on the external load circuit based on the self-locking voltage.
2. The overcurrent protection circuit as claimed in claim 1, characterized in that: The MOS tube control circuit includes an N-type MOS tube, the drain of the N-type MOS tube is connected to the external load circuit, the source of the N-type MOS tube is connected to the resistance sampling circuit, and the gate of the N-type MOS tube is connected to the transistor self-locking circuit and the power conversion circuit.
3. The overcurrent protection circuit as claimed in claim 2, characterized in that: The resistance sampling circuit includes at least one sampling resistor and a first resistor, the first end of the sampling resistor is respectively connected to the source of the N-type MOS tube and the first end of the first resistor, the second end of the sampling resistor is connected to the system power ground, and the second end of the first resistor is connected to the transistor self-locking circuit.
4. The overcurrent protection circuit as claimed in claim 3, characterized in that: The overcurrent protection circuit also includes a first power supply and a second power supply, wherein the first power supply is connected to the transistor self-locking circuit and the power conversion circuit respectively, and the second power supply is connected to the power conversion circuit.
5. The overcurrent protection circuit as claimed in claim 4, characterized in that: The overcurrent protection circuit further includes a side branch circuit, and the side branch circuit includes a second resistor, a third resistor and a fourth resistor; The first power supply is respectively connected to the first end of the second resistor and the first end of the third resistor, the transistor self-locking circuit is respectively connected to the second end of the second resistor and the second end of the third resistor, the first end of the fourth resistor is respectively connected to the gate of the N-type MOS tube, the transistor self-locking circuit and the power conversion circuit, and the second end of the fourth resistor is connected to the system power ground.
6. The overcurrent protection circuit as claimed in claim 5, characterized in that: The transistor self-locking circuit includes an NPN transistor and a diode, the emitter of the NPN transistor is connected to the system power ground, the base of the NPN transistor is connected to the second end of the first resistor, the collector of the NPN transistor is respectively connected to the cathode of the diode and the second end of the second resistor, and the anode of the diode is respectively connected to the gate of the N-type MOS tube and the first end of the fourth resistor.
7. The overcurrent protection circuit as claimed in claim 6, characterized in that: The transistor self-locking circuit also includes a PNP transistor, the collector of the PNP transistor is connected to the second end of the first resistor, the base of the PNP transistor is connected to the collector of the NPN transistor, and the emitter of the PNP transistor is connected to the second end of the third resistor.
8. The overcurrent protection circuit as claimed in claim 7, characterized in that: The power conversion circuit includes a power conversion chip, a capacitor and an output circuit, and the power conversion chip includes at least a first pin, a second pin, a third pin, a fourth pin and a fifth pin; The first pin is connected to the third pin and then to the system power ground, the second pin is connected to the second power supply, the fourth pin is connected to the output circuit, the fifth pin is respectively connected to the first power supply and the first end of the capacitor, and the second end of the capacitor is connected to the system power ground.
9. The overcurrent protection circuit as claimed in claim 8, characterized in that: The output circuit includes at least one output resistor, a first end of the output resistor is connected to the fourth pin, and a second end of the output resistor is connected to a first end of the fourth resistor.
10. An overcurrent protection device, characterized in that: The overcurrent protection device comprises the overcurrent protection circuit according to any one of claims 1 to 9.