Short-circuit protection circuit based on N-MOS

Abstract

The invention relates to the technical field of protection circuits, and discloses an N-MOS-based short-circuit protection circuit, which is arranged between a load and a power supply, and comprises an N-MOS tube, a first voltage sampling circuit, an inductor, a second voltage sampling circuit and a control unit, the control unit judges whether short circuit occurs or not based on the MOS tube voltage and the inductor voltage, and comprises the following steps: if a change value of the MOS tube voltage is greater than a preset voltage value in a preset time period, judging whether the inductor voltage tends to be 0 in the preset time period, and if the change value tends to be 0, judging that short circuit occurs, and controlling a grid electrode of the N-MOS tube to turn off the N-MOS tube. According to the invention, the circuit protection precision is improved based on dual signal judgment of MOS tube voltage and inductor voltage.

Description

Technical Field

[0001] The present invention relates to the technical field of protection circuits, and in particular to a short-circuit protection circuit based on N-MOS. Background Art

[0002] As a power conversion device, high-current N-MOS is becoming more and more popular. It has the characteristics of small size, low cost, high operating frequency and large operating current. In devices such as low-voltage motor drivers and low-voltage power supplies with output currents of several hundred amperes, high-current N-MOS handles large currents and may cause short circuits under special working conditions. Once a short circuit occurs, if there is no effective protection measure, the high-current N-MOS device will be damaged, thus affecting the normal operation of the entire circuit system. Therefore, a short-circuit protection circuit is essential for high-current N-MOS.

[0003] In the past, short-circuit protection circuits usually use resistors to sample the current flowing through N-MOS for short-circuit detection, but resistors will produce large power losses in large currents and have low monitoring efficiency. For example, using Hall to sample the current flowing through N-MOS can sample large currents with low losses, but the sampling speed is slow and the cost is high. In addition, the Hall sensor is large and easily interfered, resulting in inaccurate sampling results.

[0004] In summary, the traditional short-circuit protection circuit will have a large power loss and slow response speed during the monitoring process. Moreover, the current-based short-circuit detection usually needs to convert the current into a voltage signal through a sampling resistor or sensor, and then make a judgment after amplification and processing; this process will introduce a certain delay. For short-circuit events, this delay may cause the protection circuit to fail to respond in time, which may easily cause device damage. And the detection based on voltage signals often only focuses on the voltage signal of the N-MOS tube, which is easily interfered by noise and leads to misjudgment. Summary of the invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the problem that the method based on voltage detection of N-MOS tube short circuit in the prior art is easily interfered by noise and prone to misjudgment.

[0006] In order to solve the above technical problems, the present invention provides a short-circuit protection circuit based on N-MOS, which is arranged between a load and a power supply, and includes: An N-MOS tube, the drain of which is connected to one end of the load, and the other end of the load is connected to the positive electrode of the power supply; The first voltage sampling circuit is connected in parallel between the source and the gate of the N-MOS tube to collect the voltage of the MOS tube in real time; An inductor, one end of which is connected to the source of the N-MOS tube, and the other end of which is connected to the negative electrode of the power supply; The second voltage sampling circuit is connected in parallel to both ends of the inductor to collect the inductor voltage in real time; A control unit, whose output end is connected to the gate of the N-MOS tube, and whose input end is connected to the output end of the first voltage sampling circuit and the output end of the second voltage sampling circuit; judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage, comprising: if the change value of the MOS tube voltage is greater than the preset voltage value within the preset time period, judging whether the inductor voltage tends to 0 within the preset time period; if it tends to 0, judging that a short circuit occurs, and controlling the gate of the N-MOS tube to turn off the N-MOS tube.

[0007] Preferably, judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage further includes: If the change value of the MOS tube voltage is not greater than the preset voltage value within the preset time period, it is determined that no short circuit occurs.

[0008] Preferably, judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage further includes: If within a preset time period, the change value of the MOS tube voltage is greater than a preset voltage value, and the inductor voltage does not tend to 0, it is determined that no short circuit occurs.

[0009] Preferably, the first voltage sampling circuit is a differential amplifier, whose in-phase input pin is connected to the drain of the N-MOS tube, the inverting input pin is connected to the source of the N-MOS tube, and the output pin is connected to the input end of the control unit.

[0010] Preferably, the second voltage sampling circuit is a differential amplifier, a non-inverting input pin and an inverting input pin of the differential amplifier are connected in parallel at two ends of the inductor, and an output end of the differential amplifier is connected to an input end of the control unit.

[0011] Preferably, it also includes a body diode, whose anode is connected to the source of the N-MOS tube, and whose cathode is connected to the drain of the N-MOS tube.

[0012] Preferably, it also includes: a current sampling circuit, whose input end is connected to the load, and whose output end is connected to the input end of the control unit, so as to collect the load current value in real time.

[0013] Preferably, the current sampling circuit is a low-side current detection circuit, comprising: A sampling resistor, one end of which is connected to the load and the other end is grounded; The differential amplifier has a non-inverting input pin and an inverting input pin connected in parallel at both ends of the sampling resistor, and an output end connected to an input end of the control unit.

[0014] Preferably, the control unit controls the conduction time of the N-MOS tube based on the load current value, including: If the load current value is within the preset current range, the conduction time of the N-MOS tube is not changed; If the load current value is greater than the preset current range, the conduction time of the N-MOS tube is reduced until the load current value meets the preset current range; If the load current value is less than the preset current range, the conduction time of the N-MOS tube is increased until the load current value meets the preset current range.

[0015] Preferably, a soft start circuit is also included, including: A driving resistor, one end of which is connected to the gate of the N-MOS tube; A MOSFET driver, whose input end is connected to the output end of the control unit, and whose output end is connected to the other end of the driving resistor, so as to drive the N-MOS tube to turn on after a preset time interval after the N-MOS tube is short-circuited and turned off; A driving capacitor has one end connected to the gate of the N-MOS tube and the other end connected to the ground.

[0016] The above technical solution of the present invention has the following beneficial effects compared with the prior art: The N-MOS-based short-circuit protection circuit of the present invention directly collects the voltage of the N-MOS tube and the inductor. Based on the relationship between the current and the voltage, when a short circuit occurs in the circuit and the current in the circuit suddenly changes, the voltage of the N-MOS tube and the inductor also changes accordingly, and then it can be judged whether a short circuit occurs in the circuit based on the change of the N-MOS tube voltage and the inductor voltage; when a short circuit occurs, the detection of the voltage change is much faster than the direct detection of the current change, and the voltage signal is not easily disturbed by devices such as the inductor, and can more accurately reflect the system state, and then can quickly respond to the short circuit situation, turn off the N-MOS tube in time, and avoid device damage; and the dual signal combined judgment effectively avoids the influence of parasitic parameters, is more suitable for high-frequency and high-current scenarios, significantly improves the accuracy of short-circuit detection, and ensures circuit stability and safety. At the same time, the added inductor plays the role of filtering and energy storage in the circuit, can smooth current fluctuations, and improve the stability of the circuit.

[0017] The voltage sampling circuit of the present invention is implemented based on a differential amplifier, and can quickly and accurately detect the voltage changes of an N-MOS tube and an inductor, meeting the requirements of real-time, low loss and low cost for short-circuit protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to make the content of the present invention more clearly understood, the present invention is further described in detail below according to specific embodiments of the present invention in conjunction with the accompanying drawings, wherein: Figure 1 It is a structural diagram of a short-circuit protection circuit based on N-MOS provided by the present invention; Figure 2 It is a connection diagram of N-MOS short-circuit protection circuit; Figure 3 This is a connection diagram of a short-circuit protection circuit based on N-MOS; Figure 4 It is a curve diagram showing the relationship between the inductance and the current. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0020] Reference Figure 1 As shown, the structure diagram of the short-circuit protection circuit based on N-MOS of the present invention; the short-circuit protection circuit based on N-MOS is arranged between the load and the power supply, and the specific structure includes: An N-MOS tube, the drain of which is connected to one end of the load, and the other end of the load is connected to the positive electrode of the power supply; The first voltage sampling circuit is connected in parallel between the source and the gate of the N-MOS tube to collect the voltage of the MOS tube in real time; An inductor, one end of which is connected to the source of the N-MOS tube, and the other end of which is connected to the negative electrode of the power supply; The second voltage sampling circuit is connected in parallel to both ends of the inductor to collect the inductor voltage in real time; A control unit, whose output end is connected to the gate of the N-MOS tube, and whose input end is connected to the output end of the first voltage sampling circuit and the output end of the second voltage sampling circuit; judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage, comprising: if the change value of the MOS tube voltage is greater than the preset voltage value within the preset time period, judging whether the inductor voltage tends to 0 within the preset time period; if it tends to 0, judging that a short circuit occurs, and controlling the gate of the N-MOS tube to turn off the N-MOS tube.

[0021] The present invention collects MOS tube voltage and inductor voltage in real time through a first voltage sampling circuit and a second voltage sampling circuit to comprehensively monitor the circuit state; the dual judgment mechanism of MOS tube voltage and inductor voltage improves the judgment accuracy of circuit short circuit conditions, and at the same time, the preset voltage value can be flexibly adjusted to make the protection circuit suitable for different scenarios and load requirements.

[0022] Specifically, the control unit regulates the N-MOS tube based on the MOS tube voltage and the inductor voltage collected by the first sampling voltage and the second sampling voltage, specifically including: Determine whether the change value of the MOS tube voltage is greater than the preset voltage value within the preset time period: If it is not greater than, it is determined that no short circuit occurs; If it is greater than, determine whether the inductor voltage tends to 0 within the preset time period: If it does not tend to 0, it is determined that no short circuit occurs; If it approaches 0, it is determined that a short circuit occurs and the gate of the N-MOS tube is controlled to turn off the N-MOS tube.

[0023] In the embodiment of the present invention, the first voltage sampling circuit is a differential amplifier, whose in-phase input pin is connected to the drain of the N-MOS tube, the reverse input pin is connected to the source of the N-MOS tube, and the output pin is connected to the input end of the control unit.

[0024] In the embodiment of the present invention, the second voltage sampling circuit is a differential amplifier, whose in-phase input pin and inverting input pin are connected in parallel at both ends of the inductor, and whose output end is connected to the input end of the control unit.

[0025] The voltage sampling circuit of the present invention is realized based on a differential amplifier, and can quickly and accurately detect the voltage changes of the N-MOS tube and the inductor, meeting the requirements of real-time, low loss and low cost of short-circuit protection. In addition, the differential amplifier has a high input impedance, has little impact on the circuit under test, and can effectively suppress common-mode noise, thereby improving the accuracy of voltage sampling.

[0026] Specifically, the voltage sampling circuit of this embodiment can also use an operational amplifier, such as TLV9001, which is a single-channel low-voltage operational amplifier. After using a resistor divider to attenuate the signal to the input range of TLV9001, it is output through a voltage follower. After the voltage signal of the MOS tube and the inductor is divided by the resistor, it is connected to the in-phase input terminal of TLV9001, and the inverting input terminal is directly connected to the output terminal to form negative feedback. At the same time, the output terminal is connected to the input terminal of the control unit, and the collected MOS tube voltage and inductor voltage are sent to the control unit.

[0027] Specifically, it also includes a body diode, an anode of which is connected to the source of the N-MOS tube, and a cathode of which is connected to the drain of the N-MOS tube.

[0028] Reference Figure 2 As shown, it is a connection relationship diagram of the N-MOS short-circuit protection circuit; based on the above embodiment, the embodiment of the present invention also includes: a current sampling circuit, whose input end is connected to the load, and whose output end is connected to the input end of the control unit, to collect the load current value in real time.

[0029] Specifically, the current sampling circuit is a low-side current detection circuit, including: A sampling resistor, one end of which is connected to the load and the other end is grounded; The differential amplifier has a non-inverting input pin and an inverting input pin connected in parallel at both ends of the sampling resistor, and an output end connected to an input end of the control unit.

[0030] Specifically, the control unit controls the conduction time of the N-MOS tube based on the load current value, including: If the load current value is within the preset current range, the conduction time of the N-MOS tube is not changed; If the load current value is greater than the preset current range, the conduction time of the N-MOS tube is reduced until the load current value meets the preset current range; If the load current value is less than the preset current range, the conduction time of the N-MOS tube is increased until the load current value meets the preset current range.

[0031] Based on the above embodiment, the embodiment of the present invention further includes a soft start circuit, including: A driving resistor, one end of which is connected to the gate of the N-MOS tube; A MOSFET driver, whose input end is connected to the output end of the control unit, and whose output end is connected to the other end of the driving resistor, so as to drive the N-MOS tube to turn on after a preset time interval after the N-MOS tube is short-circuited and turned off; A driving capacitor has one end connected to the gate of the N-MOS tube and the other end connected to the ground.

[0032] Among them, the MOSFET driver provides sufficient driving current and controls the rising speed of the gate voltage through the RC circuit. The current charges the driving capacitor C through the driving resistor R, so that the gate voltage of the N-MOS tube gradually rises, and the N-MOS tube slowly turns on to achieve soft start.

[0033] Reference Figure 3 As shown, it is a connection diagram of the short-circuit protection circuit based on N-MOS; the current sampling circuit can collect the load current value in real time and provide accurate current information for the control unit, so that the control unit can dynamically adjust the conduction time of the N-MOS tube according to the real-time load current value, realize accurate current control, improve the stability and efficiency of the circuit, and further enhance the performance and applicability of the short-circuit protection circuit based on N-MOS; at the same time, combined with the soft start circuit, after the fault is eliminated, the N-MOS tube can be slowly turned on.

[0034] The N-MOS-based short-circuit protection circuit of the present invention directly collects the voltage of the N-MOS tube and the inductor. Based on the relationship between the passing current and the voltage, when a short circuit occurs in the circuit or the current in the circuit suddenly changes, the voltage of the N-MOS tube and the inductor also changes accordingly, and then it can be judged whether a short circuit occurs in the circuit based on the changes in the N-MOS tube voltage and the inductor voltage; when a short circuit occurs, the detection of voltage changes is much faster than directly detecting current changes, and the voltage signal is not easily interfered by devices such as the inductor, and can more accurately reflect the system state, and then can quickly respond to the short circuit situation, and turn off the N-MOS tube in time to avoid device damage; and the dual signal combined judgment effectively avoids the influence of parasitic parameters, is more suitable for high-frequency and high-current scenarios, significantly improves the accuracy of short-circuit detection, and ensures circuit stability and safety.

[0035] In this embodiment, during the conduction process of the N-MOS tube, the energy borne by the N-MOS tube is expressed as: ;in, Represents the voltage between the drain and source of the N-MOS tube. Represents the current flowing between the drain and source of the N-MOS tube. Indicates the conduction time of the N-MOS tube.

[0036] After the N-MOS tube is turned on, the MOS works in the saturation region, the on-current is the set value, and the voltage is the saturation voltage drop, which is very small; the energy borne by the N-MOS tube is far less than the rated value and can work safely.

[0037] After the N-MOS tube is short-circuited, the on-current changes drastically, with the amplitude exceeding the rated value by several times or even dozens of times; at the same time, the voltage also changes drastically, from the original very small on-saturation voltage drop to several times or even dozens of times larger; this may cause the energy borne by the N-MOS tube to exceed the rated value of the N-MOS tube, and the N-MOS tube will be damaged.

[0038] In this embodiment, the voltage applied across the inductor is expressed as: ;in, Indicates the inductance of the inductor. Represents the change in current flowing through the inductor, Indicates the amount of change over time. Figure 4 As shown, this is a curve chart showing the relationship between the inductance and current of the inductor. Usually, the current flowing through the inductor is less than the rated value of the inductor, and the inductance is a constant. If the current flowing through the inductor is much greater than the rated value of the inductor, the inductor is saturated, and the greater the current, the smaller the inductance.

[0039] This embodiment uses the fact that after a high-current N-MOS tube is short-circuited, the current flowing through the inductor is much greater than its rated value. At this time, the inductor is saturated and the inductance decreases to almost zero, that is, the voltage loaded on both ends of the inductor is almost 0. The current flowing through the N-MOS becomes larger (with a large amplitude), the N-MOS becomes oversaturated, and the voltage between the drain and the source also becomes larger (with a large amplitude). The control unit controls the on and off of the N-MOS tube by comparing the inductor voltage and the high-current N-MOS tube voltage under normal working conditions and after a short circuit occurs, so as to ensure the normal operation of the system.

[0040] Specifically, the specific connection relationship of the N-MOS short-circuit protection circuit of this embodiment is as follows: the positive electrode of the power supply is connected to the load, one end of the load is connected to the drain of the N-MOS, the anode of the internal diode and one end of the first voltage sampling circuit; the gate of the N-MOS is connected to the control unit; the source of the N-MOS and the cathode of the internal diode are connected to one end of the inductor L, and are connected to one end of the first voltage sampling circuit and one end of the second voltage sampling circuit at the same time; the other end of the first voltage sampling circuit is connected to the control unit, and the other end of the second voltage sampling circuit is connected to the control unit; the other end of the inductor L is connected to the negative electrode of the power supply, one end of the load is connected to the feedback circuit, and the other end of the feedback circuit is connected to the control unit; the power supply + and the power supply - provide energy for the system, the load is a resistor and various power conversion units, which consume energy, the first voltage sampling circuit is for sampling the voltage between the drain and source of the N-MOS Z, and the second current sampling circuit samples the voltage across the inductor L; the feedback circuit samples the changes in the load and various work instructions, and the control unit is the core of the system, sampling, judging, and outputting instructions to the N-MOS.

[0041] When the circuit is in normal working state, the control unit outputs a driving waveform according to the feedback circuit, the N-MOS is turned on, and the current I flowing through the N-MOS is within the current rating of the N-MOS. According to the characteristics of the N-MOS, the voltage drop VZ across the drain and source of the N-MOS is very small, and VZ is the voltage drop of the N-MOS when it is saturated and turned on. The first voltage sampling circuit feeds back to the control unit VF1, and the current I flowing through the inductor is within the rated value of the inductor current, satisfying The second voltage sampling circuit samples the voltage VL and feeds it back to the control unit VF2. At this time, the control unit determines that the system is normal based on VF1 and VF2, outputs a driving waveform, turns on the N-MOS, and the system works.

[0042] Specifically, the feedback circuit is a current sampling circuit that samples the current of the load. The control unit compares the sampled value with the set value of the control unit. If the sampled value is greater than the set value, the on-time of the MOS is reduced. If the sampled value is less than the set value, the on-time of the MOS is increased.

[0043] When the system is disturbed or the load is in an abnormal state, the current flowing through the N-MOS exceeds several times or even dozens of times the rated value. That is, after the N-MOS is short-circuited, the N-MOS current I flowing through it becomes larger (several times or even dozens of times the rated value), and the voltage VZ between the drain and source also increases (with a large amplitude). Under normal working conditions, the amplitude is very small, which is the on-state voltage drop of the N-MOS.

[0044] Under normal working conditions, the current increment flowing through the inductor is large, and VL is also large. VZ is fed back to the control unit VF1 through the first voltage sampling circuit, and VL is fed back to the control unit VF2 through the second voltage sampling circuit. Under normal working conditions and short circuit conditions, VL and VZ change dramatically, and the feedback signals VF1 and VF2 also change. At this time, the control unit compares VF1 and VF2 to the difference between normal working conditions and short circuits, judges the system abnormality, shuts off the drive waveform, N-MOS shuts off, and the system stops working. At the moment of short circuit, by comparing the large current N-MOS (voltage mutation between drain and source) and inductance (inductance mutation, almost 0), the system makes a judgment on the two feedback signals VF1 and VF2, and reliably shuts off N-MOS to ensure system safety and avoid abnormal interference. The current I flowing through the inductor is much larger than the rated value, the inductor is saturated, the inductance is almost zero, and the voltage VL at both ends of the inductor is also zero.

[0045] The N-MOS-based short-circuit protection circuit provided by the present invention can be applied to high-current occasions such as passenger car chargers and electric welding machines. Passenger car chargers need to handle high voltage and high current when working to ensure fast charging; however, short circuit or overcurrent problems are easily caused by abnormal load, line fault or external interference during high-power transmission; by setting the N-MOS-based short-circuit protection circuit provided by the present invention in the passenger car charger, when a short circuit or overcurrent is detected, the circuit can shut down the N-MOS tube within microseconds, cut off the current path, and prevent the internal components of the charger from being damaged due to overcurrent; after the short-circuit fault is eliminated, the circuit can automatically or manually restore the charging function to avoid charging interruption due to false triggering; and it has strong compatibility and is suitable for a variety of charging protocols and power levels to meet the diverse needs of passenger car chargers. The electric welder will generate extremely high instantaneous current when working, and the load changes frequently, which may easily cause failures due to poor electrode contact or load short circuit. When the short-circuit protection circuit provided by the present invention is used in the electric welder, it has strong impact resistance. By real-time monitoring of the welding current and voltage, the circuit can quickly identify abnormal conditions and immediately shut down the N-MOS tube to protect the core components of the electric welder. When the electric welder is started, the gate voltage of the N-MOS tube is gradually increased through the soft start circuit to avoid the impact of instantaneous large current on the circuit and load, thereby ensuring that the N-MOS tube works stably under high load conditions and extending the service life of the electric welder.

[0046] The N-MOS-based short-circuit protection circuit of the present invention directly collects the voltage of the N-MOS tube and the inductor. Based on the relationship between the current and the voltage, when the circuit is short-circuited and the current in the circuit changes suddenly, the voltage of the N-MOS tube and the inductor also changes accordingly, and then it can be judged whether a short circuit occurs in the circuit based on the change of the N-MOS tube voltage and the inductor voltage; when a short circuit occurs, the detection of the voltage change is much faster than the direct detection of the current change, and the voltage signal is not easily disturbed by devices such as the inductor, and can more accurately reflect the system state, and then can quickly respond to the short circuit situation, turn off the N-MOS tube in time, and avoid device damage; and the dual signal combined judgment effectively avoids the influence of parasitic parameters, is more suitable for high-frequency and high-current scenarios, significantly improves the accuracy of short-circuit detection, and ensures circuit stability and safety. The voltage sampling circuit of the present invention is implemented based on a differential amplifier, can quickly and accurately detect the voltage changes of the N-MOS tube and the inductor, and meet the real-time, low-loss and low-cost requirements of short-circuit protection.

[0047] Those skilled in the art will appreciate that the embodiments of the present application may be provided as methods, systems, or computer program products. Therefore, the present application may adopt the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present application may adopt the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes.

[0048] The present application is described with reference to the flowcharts and / or block diagrams of the methods, devices (systems), and computer program products according to the embodiments of the present application. It should be understood that each process and / or box in the flowchart and / or block diagram, as well as the combination of the processes and / or boxes in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to generate a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0049] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0050] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0051] Obviously, the above embodiments are merely examples for the purpose of clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the present invention.

Claims

1. A short-circuit protection circuit based on N-MOS, characterized in that: Set between the load and the power supply, including: An N-MOS tube, the drain of which is connected to one end of the load, and the other end of the load is connected to the positive electrode of the power supply; The first voltage sampling circuit is connected in parallel between the source and the gate of the N-MOS tube to collect the voltage of the MOS tube in real time; An inductor, one end of which is connected to the source of the N-MOS tube, and the other end of which is connected to the negative electrode of the power supply; The second voltage sampling circuit is connected in parallel to both ends of the inductor to collect the inductor voltage in real time; A control unit, whose output end is connected to the gate of the N-MOS tube, and whose input end is connected to the output end of the first voltage sampling circuit and the output end of the second voltage sampling circuit; judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage, comprising: if the change value of the MOS tube voltage is greater than the preset voltage value within the preset time period, judging whether the inductor voltage tends to 0 within the preset time period; if it tends to 0, judging that a short circuit occurs, and controlling the gate of the N-MOS tube to turn off the N-MOS tube.

2. The N-MOS-based short-circuit protection circuit according to claim 1, characterized in that: Judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage also includes: If the change value of the MOS tube voltage is not greater than the preset voltage value within the preset time period, it is determined that no short circuit occurs.

3. The N-MOS-based short-circuit protection circuit according to claim 1, characterized in that: Judging whether a short circuit occurs based on the MOS tube voltage and the inductor voltage also includes: If within a preset time period, the change value of the MOS tube voltage is greater than a preset voltage value, and the inductor voltage does not tend to 0, it is determined that no short circuit occurs.

4. The N-MOS-based short-circuit protection circuit according to claim 1, characterized in that: The first voltage sampling circuit is a differential amplifier, whose in-phase input pin is connected to the drain of the N-MOS tube, the reverse input pin is connected to the source of the N-MOS tube, and the output pin is connected to the input end of the control unit.

5. The N-MOS-based short-circuit protection circuit according to claim 1, characterized in that: The second voltage sampling circuit is a differential amplifier, a non-inverting input pin and a reverse input pin of the second voltage sampling circuit are connected in parallel at two ends of the inductor, and an output end of the second voltage sampling circuit is connected to an input end of the control unit.

6. The N-MOS-based short-circuit protection circuit according to claim 1, characterized in that: It also includes a body diode, an anode of which is connected to the source of the N-MOS tube, and a cathode of which is connected to the drain of the N-MOS tube.

7. The N-MOS based short circuit protection circuit according to claim 1, characterized in that: Also includes: The current sampling circuit has an input end connected to the load and an output end connected to the input end of the control unit to collect the load current value in real time.

8. The N-MOS-based short-circuit protection circuit according to claim 7, characterized in that: The current sampling circuit is a low-side current detection circuit, including: A sampling resistor, one end of which is connected to the load and the other end is grounded; The differential amplifier has a non-inverting input pin and an inverting input pin connected in parallel at both ends of the sampling resistor, and an output end connected to an input end of the control unit.

9. The N-MOS-based short-circuit protection circuit according to claim 7, characterized in that: The control unit controls the conduction time of the N-MOS tube based on the load current value, including: If the load current value is within the preset current range, the conduction time of the N-MOS tube is not changed; If the load current value is greater than the preset current range, the conduction time of the N-MOS tube is reduced until the load current value meets the preset current range; If the load current value is less than the preset current range, the conduction time of the N-MOS tube is increased until the load current value meets the preset current range.

10. The N-MOS based short circuit protection circuit according to claim 1, characterized in that: Also included is a soft-start circuit, including: A driving resistor, one end of which is connected to the gate of the N-MOS tube; A MOSFET driver, whose input end is connected to the output end of the control unit, and whose output end is connected to the other end of the driving resistor, so as to drive the N-MOS tube to turn on after a preset time interval after the N-MOS tube is short-circuited and turned off; A driving capacitor has one end connected to the gate of the N-MOS tube and the other end connected to the ground.

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