Short circuit protection circuit for power devices

Abstract

The utility model provides a kind of short-circuit protection circuit of power device, it is related to switching power supply technical field, short-circuit protection circuit includes: power device, sampling module, protection module;Wherein, the gate of power device is used to connect control module, the source of power switch device is grounded, the drain of power device is used to connect preset power supply;The input end of sampling module connects the drain of power device, the control end of sampling module connects the gate of power device, the output end of sampling module connects the input end of protection module, the output end of protection module connects the gate of power device.Adopting the utility model, the short-circuit tolerance of power device can be promoted, and circuit stability is improved.

Description

Technical Field

[0001] This application relates to the field of switching power supply technology, and more specifically, to a short-circuit protection circuit for a power device. Background Technology

[0002] Power devices are key actuators for implementing PWM (Pulse Width Modulation). In practical applications, short circuits at the output terminal are highly likely to occur due to factors such as the inductive load characteristics of the motor itself, aging wiring, insulation damage, or foreign object intrusion. Once a short circuit occurs, it generates a large instantaneous current far exceeding the rated value of the power switching device. This current can cause the device to overheat and break down in a very short time, or even cause permanent damage, leading to the failure of the entire system, resulting in safety hazards and economic losses.

[0003] To address these issues, existing drive systems typically incorporate short-circuit protection. The most common protection scheme involves connecting a sampling resistor in series in the current loop of the power switching device, and controlling the switching of the power switching device by monitoring the voltage drop across the resistor. However, the current flowing through the sampling resistor from the power switching device incurs significant losses, especially under high-current application conditions. Utility Model Content

[0004] This utility model provides a short-circuit protection circuit for power devices, which can improve the short-circuit withstand capability of power devices and enhance circuit stability.

[0005] In a first aspect, the present invention provides a short-circuit protection circuit for a power device, comprising: a power device, a sampling module, and a protection module; The power device's gate is connected to the control module, its source is grounded, and its drain is connected to a preset power supply. The sampling module's input is connected to the power device's drain, its control terminal is connected to the power device's gate, its output is connected to the protection module's input, and its output is connected to the power device's gate.

[0006] Optionally, the sampling module includes: a sampling tube and a voltage divider unit; The drain of the sampling tube is the input terminal of the sampling module and is used to connect to the drain of the power device. The gate of the sampling tube is the control terminal of the sampling module and is used to connect to the gate of the power device. The source of the sampling tube is grounded through the voltage divider unit, and the voltage divider point of the voltage divider unit is the output terminal of the sampling module, which is used to connect to the input terminal of the protection module.

[0007] Optionally, the sampling tube is an enhanced low-voltage switching device.

[0008] Optionally, the power device is a single semiconductor power device, and the protection module includes: a first protection transistor, the gate of the first protection transistor being the input terminal of the protection module, the drain of the first protection transistor being connected to the gate of the power device, and the source of the first protection transistor being grounded.

[0009] Optionally, the protection module further includes: a second protection transistor and a resistor, wherein the gate of the second protection transistor is connected to the drain of the first protection transistor, the drain of the second protection transistor is grounded, the source of the second protection transistor is also connected to the gate through the resistor, and the source of the second protection transistor is used to connect to the output terminal of the protection module.

[0010] Optionally, the first protection tube is an enhanced switching device.

[0011] Optionally, the power device is any one of the following: silicon metal oxide semiconductor transistor (Si MOSFET), silicon carbide metal oxide semiconductor crystal (SiC MOSFET), and gallium nitride (GaN) power device.

[0012] Optionally, the power device is a cascaded power switching device that encapsulates a main power device and a sampling power device, wherein the main power device and the sampling power device are mirror images of each other; The sampling module includes a voltage divider unit, wherein the source of the sampling power device in the cascaded power switching device is grounded through the voltage divider unit, and the voltage divider point of the voltage divider unit is the output terminal of the sampling module, which is used to connect to the input terminal of the protection module.

[0013] Optionally, the main power device includes a first normally open device and a first power device, and the sampling power device includes a second normally open device and a second power device; Wherein, the drain of the first normally open device and the drain of the second normally open device are connected, the gate of the first normally open device is connected to the gate of the second normally open device, and the first normally open device and the second normally open device are mirror switching devices of each other. The source of the first normally open device is connected to the drain of the first power device, the gate of the first power device is the gate of the main power device, and the source of the first power device is the source of the main power device. The source of the second normally open device is connected to the drain of the second power device, the gate of the second power device is the gate of the sampling power device, and the source of the second power device is the source of the sampling power device used to connect to the voltage divider unit.

[0014] Optionally, the first normally open device and the second normally open device are depletion-type normally open devices, and the first power device and the second power device are enhancement-mode low-voltage field-effect transistors.

[0015] This application provides a short-circuit protection circuit for a power device. By connecting a sampling module and a protection module to the gate of the power device, the input of the sampling module is connected to the drain of the power device, and the output of the sampling module is connected to the input of the protection module. When the control module outputs a signal to turn on the power device, the protection module can clamp the gate voltage of the power device based on the signal acquired by the sampling module. By using such a short-circuit protection circuit for power devices, the inflow current can be clamped within the safe operating area of ​​the power device, significantly improving the short-circuit withstand capability of the power device, increasing the reliability and durability of the circuit, and reducing the risk of damage to the power device. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 A schematic diagram of a short-circuit protection circuit for a power device provided in an embodiment of this utility model; Figure 2 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 3 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 4 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 5 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 6 A diagram showing the variation of operating parameters of the short-circuit protection circuit for the power device provided by this utility model; Figure 7 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 8 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 9A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 10 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model; Figure 11 A schematic diagram of the short-circuit protection circuit for another power device provided in an embodiment of this utility model.

[0018] Explanation of icon numbers: 1. Short circuit protection circuit; 10. Preset power supply; 2. Control module; 3. Power device; 4. Sampling module; 5. Protection module; 31. Main power device; 32. Sampling power device; 41. Voltage divider unit. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0021] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0022] Furthermore, the terms "first," "second," and "third" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0023] In the description of this utility model, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0024] Before providing a detailed explanation of this disclosure, let us first introduce the application scenarios of this disclosure.

[0025] When a short circuit occurs, a huge amount of energy surges into the power device, subjecting it to high voltage and large current. Short circuit protection can be achieved by detecting the voltage across an external resistor. Once a short circuit event is confirmed, the circuit can be protected by shutting down the power device. For power devices, the magnitude of their saturation current and their short-circuit withstand capability are negatively correlated. To improve short-circuit withstand capability, it is often necessary to limit the saturation current of the power device.

[0026] Based on this, this application proposes a short-circuit protection circuit for power devices. The gate of the power device is connected to a sampling module and a protection module. The input terminal of the sampling module is connected to the drain of the power device, and the output terminal of the sampling module is connected to the input terminal of the protection module. When the control module outputs a signal to turn on the power device, the protection module can clamp the gate voltage of the power device based on the signal collected by the sampling module. This significantly improves the short-circuit withstand capability of the power device, increases the reliability and durability of the circuit, and reduces the risk of damage to the power device.

[0027] The following explanation, in conjunction with the accompanying drawings, uses several embodiments to illustrate the concepts. Figure 1 This is a schematic diagram of a short-circuit protection circuit for a power device provided in this application. Figure 1 As shown, the short-circuit protection circuit 1 of the power device includes: power device 3, sampling module 4, and protection module 5.

[0028] The gate of the power device 3 is used to connect to the control module 2. Optionally, the power device 3 is composed of one or more metal-oxide-semiconductor field-effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), wide-bandgap semiconductor devices (silicon carbide MOSFETs and gallium nitride GaN power devices), or junction field-effect transistors (JEFTs). This embodiment does not impose any limitations on this.

[0029] Optionally, the control module 2 is a microcontroller unit (MCU), such as an STM32 series microcontroller, or a dedicated driver chip; this application does not impose any restrictions on this. When the control module 2 is operating normally, it outputs a PWM drive signal to the gate of the power device 3. When the PWM drive signal is high, the gate capacitor is rapidly charged until it reaches the power device's turn-on threshold voltage, at which point the power device begins to conduct; when the PWM drive signal is low, the gate charge is rapidly removed, thereby turning off the power device. Simultaneously, the source of the power device 3 is grounded, forming a reference point for current and signal; the drain of the power device 3 is connected to the positive terminal of the preset power supply 10, enabling it to control the on / off state of the entire circuit. The preset power supply 10 provides stable DC power; optionally, the preset power supply can be a switching power supply, a linear regulated power supply, or a battery (such as a lead-acid battery, lithium-ion battery, or nickel-metal hydride battery), etc.; this utility model does not impose any specific restrictions on this.

[0030] Meanwhile, the input terminal of sampling module 4 is connected to the drain of power device 3 to collect the drain voltage of power device 3; the control terminal of sampling module 4 is connected to the gate of power device 3, enabling sampling module 4 to perform real-time cross-comparison of gate voltage and drain voltage, thereby achieving faster fault diagnosis of power device 3. The output terminal of sampling module 4 is connected to the input terminal of protection module 5, thereby outputting the real-time collected electrical parameters to protection module 5, facilitating judgment by protection module 5 based on the signals.

[0031] The output terminal of the protection module 5 is connected to the gate of the power device 3. If the current flowing into the power device 3 is too large, the protection module 5 will clamp the gate voltage of the power device 3 within a certain range after making a determination, thereby realizing short-circuit protection for the power device 3, improving the short-circuit withstand capability of the power device, and enhancing the stability and reliability of the circuit system.

[0032] To ensure system safety and reliability, power device 3 should operate within its safe operating area. To enable its conduction, the gate voltage must be within the saturation region; to disable it, the gate voltage must be below the threshold voltage. In one possible implementation, if power device 3 operates within its safe operating area (i.e., the current is low), a specific sampling range can be set so that sampling module 4 does not collect electrical parameters and subsequently does not transmit them to protection module 5. In other words, both sampling module 4 and protection module 5 are inactive, reducing losses and lowering costs.

[0033] In this embodiment, by connecting the gate of the power device to the sampling module and the protection module, when the control module outputs a signal to turn on the power device, the protection module can quickly intervene in the gate voltage of the power device during short-circuit transients based on the signal collected by the sampling module, so that the power device operates within the safe operating area, which significantly improves the short-circuit withstand capability of the power device, increases the reliability and durability of the circuit, and reduces the risk of damage to the power device. Based on the short-circuit protection circuit of the power device provided in the above embodiments, in one possible implementation, the embodiments of this application may also provide an example of the implementation of the short-circuit protection circuit of the power device. Figure 2 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 2 As shown, the sampling module 4 includes: a sampling tube Q1 and a voltage divider unit 41; the drain of the sampling tube Q1 is the input terminal of the sampling module 4, used to connect to the drain of the power device 3, and the gate of the sampling tube Q1 is the control terminal of the sampling module 4, used to connect to the gate of the power device 3; the source of the sampling tube Q1 is grounded through the voltage divider unit 41, and the voltage divider point of the voltage divider unit 41 is the output terminal of the sampling module 4, used to connect to the input terminal of the protection module 5.

[0034] The sampling tube Q1 is a controlled electronic switch, which can optionally be one of MOSFET, IGBT or JFET, and this embodiment does not limit it.

[0035] Optionally, the voltage divider unit 41 can be composed of a fixed resistor or an adjustable resistor, and this embodiment does not limit this.

[0036] In this embodiment, the gates of sampling transistor Q1 and power device 3 are connected in parallel. Since their gate voltages are exactly the same, when a high-level signal is input to control module 2, sampling transistor Q1 and power device 3 will conduct simultaneously, forming a current mirror. Compared with traditional series sampling resistors, current mirror sampling consumes very little power, thereby avoiding current loss caused by the sampling resistor. In this embodiment, the specific type of sampling transistor Q1 is not limited; it can be the same type as power device 3, or it can be other switching devices capable of signal sampling.

[0037] Meanwhile, since the drain voltage of power device 3 may be very high, in order to reduce the processing difficulty of subsequent circuits, a voltage divider unit 41 is connected after the sampling tube Q1. The electrical parameters of the voltage divider unit 41 are used as the input to the protection module 5. With this setting, the voltage sampled directly can be attenuated by a certain proportion, thereby reaching the safe operating range of the protection module 5, effectively preventing the subsequent circuit from being damaged by overvoltage, and improving the reliability of the circuit.

[0038] In this embodiment, a sampling module is constructed by introducing a sampling tube and a voltage divider unit. This allows the sampling tube to proportionally replicate the current of the power device, enabling sampling and measurement of the power device. This eliminates the inherent loss problem of traditional sampling resistors, and significantly improves the efficiency of the entire circuit, especially under high current conditions. Simultaneously, the signal sampled by the sampling tube is further divided by the voltage divider unit, forming an electrical barrier to prevent high voltage surges from damaging subsequent circuits, thus increasing the reliability and safety of the circuit.

[0039] In the above Figure 2 Based on the provided embodiments, the sampling transistor Q1 may optionally be an enhancement-mode low-voltage switching device. Enhancement-mode devices are turned off at zero gate voltage and require a positive gate voltage to turn on. This allows the power device 3 and the sampling transistor Q1 to turn on synchronously when the control module 2 outputs a PWM drive signal, greatly simplifying the design and reducing costs. Simultaneously, low-voltage devices employ low on-resistance in their design, resulting in a very small voltage drop when they are conducting for sampling, thus reducing sampling power consumption. Furthermore, low-voltage devices have smaller parasitic capacitance and faster switching speeds, enabling real-time and accurate sampling of the current.

[0040] In this embodiment, an enhanced low-voltage switching device is used as the sampling transistor Q1, which simplifies the circuit design, significantly reduces the power consumption of the sampling link, improves the overall efficiency, and also enhances the response speed of the sampling module, thereby enabling more efficient and faster sampling.

[0041] In the above Figure 1 Based on the provided short-circuit protection circuit for the power device, in one possible implementation, embodiments of this application may also provide an example of an implementation of the short-circuit protection circuit for the power device. Figure 3 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of the utility model. (See diagram below.) Figure 3 As shown, the protection module 5 includes: a first protection transistor Q2, the gate of the first protection transistor Q2 is the input terminal of the protection module 5, the drain of the first protection transistor Q2 is used to connect to the gate of the power device 3, and the source of the first protection transistor Q2 is grounded.

[0042] Optionally, power device 3 is a single semiconductor power device. That is, in this embodiment, power device 3 is a single semiconductor power device such as MOSFET, IGBT, GaN, SiC MOSFET, JFET, etc., and this embodiment does not impose any restrictions on it.

[0043] In one possible implementation, such as Figure 3As shown, power device 3 is an N-channel enhancement-mode MOSFET, whose conduction state is entirely determined by the gate voltage. The source is grounded, and the gate is connected to the control terminal of control module 2, sampling module 4 and the output terminal of protection module 5. The drain is connected to the preset power supply 10 and the input terminal of sampling module 4. With this setting, protection module 5 can quickly clamp the gate voltage of power device 3, creating a safe and reliable circuit environment.

[0044] Optionally, the first protection transistor Q2 can be a bipolar transistor, field-effect transistor, or other semiconductor switching transistor; this embodiment does not impose any restrictions on this.

[0045] For protection module 5, the first protection transistor Q2 clamps the gate voltage of power device 3. Specifically, when control module 2 outputs a PWM drive signal to the gate of the first power device Q5, the gate voltage of power device 3 gradually rises to reach its turn-on voltage. Simultaneously, the gate voltage input to the first protection transistor Q2 reaches its turn-on voltage. Since the drain of the first protection transistor Q2 is connected to the gate of power device 3, the gate voltage of power device 3 is clamped to near the saturation voltage drop of the first protection transistor Q2. At this point, the gate voltage of power device 3 no longer rises and operates within the saturation region, and the current through power device 3 also reaches the saturation current. In other words, as long as the first protection transistor Q2 is on, even if power device 3 is subjected to a large current surge, the circuit state will remain stable, and the gate voltage of power device 3 will continue to be clamped by the first protection transistor Q2.

[0046] In the above Figure 3 Based on the provided short-circuit protection circuit for the power device, in one possible implementation, embodiments of this application may also provide an example of an implementation of the short-circuit protection circuit for the power device. Figure 4 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 4 As shown, the protection module 5 further includes: a second protection transistor Q3 and a resistor R1. The gate of the second protection transistor Q3 is connected to the drain of the first protection transistor Q2. The drain of the second protection transistor Q3 is grounded. The source of the second protection transistor Q3 is also connected to the gate through the resistor R1. The source of the second protection transistor Q3 is used to connect to the output terminal of the protection module 5.

[0047] Optionally, the second protection transistor Q3 can be a semiconductor structure such as a bipolar transistor or a field-effect transistor; this embodiment does not impose any restrictions on this.

[0048] exist Figure 3 In the proposed scheme, the driving section consists only of the first protection transistor Q2, resulting in a relatively slow turn-off speed, which limits the driving capability and switching frequency of the entire circuit. To overcome this deficiency, such as... Figure 4The embodiment shown is optimized by adding a second protection transistor Q3 and a resistor R1 to the first protection transistor Q2, thus forming a composite drive.

[0049] Specifically, in protection module 5, the gate of the first protection transistor Q2 is the input terminal of protection module 5, and the source of the second protection transistor Q3 is the output terminal of protection module 5. When the input voltage is less than the turn-on voltage of the first protection transistor Q2, both the first protection transistor Q2 and the second protection transistor Q3 are turned off. At this time, the base charge of the second protection transistor Q3 can be released through resistor R1, thus eliminating the need for the preceding circuit. This greatly accelerates the turn-off process, reduces switching losses, and allows the circuit to operate at a higher switching frequency, improving the circuit's driving capability. Simultaneously, due to the presence of resistor R1, the base potential of the second protection transistor Q3 can be stabilized in the turn-off state, effectively suppressing base potential fluctuations caused by the external environment, and improving the accuracy and reliability of the circuit. When the input voltage meets the turn-on voltage of the first protection transistor Q2, the first protection transistor Q2 is turned on. Current flows from the drain of the first protection transistor Q2 through the resistor R1, generating a voltage drop. This voltage drop makes the gate voltage of the second protection transistor Q3 less than the source voltage, causing the second protection transistor Q3 to be turned on. Finally, the drain of the second protection transistor Q3 clamps the gate voltage of the power device 3.

[0050] In this embodiment, by combining two switching transistors and one resistor, the driving capability of the protection module is comprehensively improved, and the requirements for the front-end circuit are reduced, thereby improving the overall working efficiency and reliability.

[0051] In the above Figure 3 Based on the provided embodiments, the first protection transistor Q2 may optionally be an enhancement-mode switching device, such as an N-channel enhancement-mode MOSFET or an NPN transistor. This embodiment does not limit this, and the following description will be based on the first protection transistor Q2 being an NPN transistor.

[0052] In the above Figure 3 Based on the provided short-circuit protection circuit for the power device, in one possible implementation, embodiments of this application may also provide an example of an implementation of the short-circuit protection circuit for the power device. Figure 5 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 5 As shown, the first protection transistor Q2 is an NPN transistor. Its base is the input terminal of the protection module 5, its collector is used to connect to the gate of the power device 3, and its emitter is grounded.

[0053] To clearly explain this embodiment, Figure 6 A diagram showing the variation of operating parameters of the short-circuit protection circuit for the power device provided by this utility model. (See diagram for reference.) Figure 6As shown, Vg is the gate voltage of power device 3, Vs is the output voltage of sampling module 4, and Isat is the saturation current of power device 3.

[0054] In one possible implementation, when power device 3 experiences overcurrent, during the t0-t1 phase, control module 2 outputs a PWM drive signal to charge the gate of power device 3. At this time, the gate voltage Vg is less than the turn-on voltage of power device 3, and both power device 3 and sampling module 4 are in the off state. During the t1-t2 phase, the gate voltage Vg reaches the turn-on voltage of power device 3, and power device 3 begins to conduct. The current of power device 3 increases with the rise of gate voltage Vg. At this time, the output Vs of sampling module 4 also increases. When Vs reaches the turn-on voltage of the first protection transistor Q2, the first protection transistor Q2 begins to conduct and clamps Vg. At this time, Vg no longer rises, power device 3 operates in the saturation region, and the current of power device 3 reaches saturation. After t2, the Vg voltage continues to be clamped by the first protection transistor Q2, the current of power device 3 remains unchanged, and the output voltage of sampling module 4 no longer changes.

[0055] In this embodiment, the power device is used as the driver of the protection module by using an enhanced switching device. Since the enhanced device is in the off state when there is no driving voltage at the gate and has a clear threshold voltage, it will only start to conduct when the input voltage exceeds the threshold voltage. This reduces the power consumption of the circuit while achieving precise control and improving the reliability of the circuit.

[0056] In the above Figure 2 Based on the provided embodiments, optionally, the power device 3 is any one of the following: silicon metal-oxide-semiconductor transistors (Si MOSFETs), silicon carbide metal-oxide-semiconductor crystals (SiC MOSFETs), and gallium nitride (GaN) power devices. Optionally, the power device 3 can be an N-channel enhancement-mode MOSFET; this embodiment does not impose any limitation on this.

[0057] To more clearly explain the present invention, based on the above embodiments, in one possible implementation, the present application embodiment may also provide an example of an implementation of a short-circuit protection circuit for a power device. Figure 7 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 7As shown, power device 3 and sampling transistor Q1 are N-channel enhancement-mode MOSFETs, voltage divider unit 41 consists of two resistors, and first protection transistor Q2 is an NPN transistor. In this embodiment, sampling module 4 includes sampling transistor Q1 and voltage divider unit 41, and protection module 5 includes first protection transistor Q2. The base of first protection transistor Q2 serves as the input of protection module 5, and its base voltage is determined by the voltage divider between the two resistors. The collector of first protection transistor Q2 is connected to the gate of power device 3, and the base voltage of first protection transistor Q2 determines the collector voltage, which in turn determines the gate voltage of power device 3. Therefore, the saturation current required by the power device can be obtained by adjusting the two resistors of voltage divider unit 41. Furthermore, since power device 3 and sampling transistor Q1 are both N-channel enhancement-mode MOSFETs, no additional level conversion or isolation circuits are needed to drive these two devices, simplifying the circuit layout and reducing circuit losses. Moreover, due to their consistent switching characteristics, the timing accuracy of sampling is ensured, increasing the efficiency of sampling.

[0058] In this embodiment, the saturation current of the power device can be determined by adjusting the resistance value of the voltage divider unit, and the power device and the sampling tube can be made to be the same type of device, thereby improving the design flexibility and robustness of the circuit.

[0059] To explain this utility model more clearly, Figure 7 Based on this, in one possible implementation, embodiments of this application may also provide an example of an implementation of a short-circuit protection circuit for a power device. Figure 8 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 8As shown, power device 3 and sampling transistor Q1 are N-channel enhancement-mode MOSFETs. The voltage divider unit 41 consists of two resistors. The first protection transistor Q2 is an NPN transistor, and the second protection transistor Q3 is a PNP transistor. In this embodiment, sampling module 4 includes sampling transistor Q1 and voltage divider unit 41, and protection module 5 includes first protection transistor Q2, second protection transistor Q3, and resistor R1. The base of first protection transistor Q2 serves as the input of protection module 5, and its base voltage is determined by the voltage division of the two resistors. Resistor R1 is connected in series between the emitter and base of second protection transistor Q3. The collector of first protection transistor Q2 is connected to the base of second protection transistor Q3. The collector of second protection transistor Q3 and the emitter of first protection transistor Q3 are grounded. The emitter of second protection transistor Q3 serves as the output of protection module 5 and is connected to the gate of power device 3. Therefore, when the first protection transistor Q2 is turned on, its collector current flows out from the base of the second protection transistor Q3 as the base drive current of the second protection transistor Q3; when the base drive current of the second protection transistor Q3 increases, its emitter voltage will also increase. The current input to the base of the first protection transistor Q2 undergoes two layers of amplification, achieving the effect of controlling a "large output" with a small current, simplifying the circuit structure while improving the circuit's driving capability.

[0060] In this embodiment, since the input of the protection module starts from the base and the output ends from the emitter, it also has a structure with high input impedance and low output impedance. This is friendly to the front-end circuit, while the switching speed is faster and it can effectively suppress environmental interference. This improves the stability of the circuit and enhances the driving capability of the circuit, providing more efficient short-circuit protection for power devices.

[0061] In the above Figure 1 Based on the provided short-circuit protection circuit for the power device, in one possible implementation, embodiments of this application may also provide an example of an implementation of the short-circuit protection circuit for the power device. Figure 9 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 9 As shown, power device 3 is a cascaded power switching device that encapsulates main power device 31 and sampling power device 32, wherein main power device 31 and sampling power device 32 are mirror images of each other; sampling module 4 includes: voltage divider unit 41, the source of sampling power device 32 in the cascaded power switching device is grounded through voltage divider unit 41, and the voltage divider point of voltage divider unit 41 is the output terminal of sampling module 4, which is used to connect to the input terminal of protection module 5.

[0062] In this embodiment, since the main power device 31 and the sampling power device 32 are mirror images of each other, in one possible implementation, by setting the ratio between the main power device 31 and the sampling power device 32, the subsequent circuit can obtain the real-time current of the main power device without loss by measuring a smaller mirror current. This setting eliminates the power loss of the external sampling resistor, significantly improving circuit efficiency. Simultaneously, since the main power device 31 and the sampling power device 32 are packaged together, they share the same junction temperature. Their threshold voltage, on-resistance, and other key parameters change synchronously with temperature, ensuring sampling stability across the entire operating temperature range and improving the reliability and accuracy of subsequent protection circuits, avoiding false protection or protection failure at high temperatures. Furthermore, since the main power device 31 and the sampling power device 32 also constitute a cascaded power switching device, by placing the main power device 31 on the high-voltage side to bear all the high voltage and placing the sampling power device 32 on the low-voltage side to bear only the low voltage, the source of the sampling power device 32 can be directly and safely grounded. This solves the problem of accurate sampling even when facing a high-voltage platform. The circuit simultaneously obtains the high-voltage withstand capability of the main power device 31 and the accurate sampling efficiency of the sampling power device 32, improving the robustness and reliability of the circuit, as well as the accuracy of subsequent short-circuit protection.

[0063] Furthermore, in this embodiment, by setting a voltage divider unit 41 in the sampling module 4, the electrical parameters of the voltage divider point of the voltage divider unit 41 are used as the input to the protection module 5. With this setting, the voltage sampled directly can be attenuated by a certain proportion, thereby reaching the safe operating range of the protection module 5, effectively preventing the downstream circuit from being damaged due to overvoltage, and improving the reliability of the circuit.

[0064] In this embodiment, by setting a main power device and a sampling power device, which are encapsulated as mirror images of each other and form a cascaded structure, the circuit achieves high-voltage isolation and lossless sampling. Furthermore, the addition of a voltage divider unit reduces the pressure on the downstream protection module, improves the accuracy of the protection module's judgment on the power device, and comprehensively enhances the reliability of the circuit and the short-circuit withstand capability of the power device.

[0065] In the above Figure 9 Based on the provided short-circuit protection circuit for the power device, in one possible implementation, embodiments of this application may also provide an example of an implementation of the short-circuit protection circuit for the power device. Figure 10 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 10As shown, the main power device 31 includes a first normally open device Q4 and a first power device Q5, and the sampling power device 32 includes a second normally open device Q6 and a second power device Q7. The drains of the first normally open device Q4 and the second normally open device Q6 are connected, and the gate of the first normally open device Q4 is connected to the gate of the second normally open device Q6. The first normally open device Q4 and the second normally open device Q6 are mirror switching devices. The source of the first normally open device Q4 is connected to the drain of the first power device Q5, the gate of the first power device Q5 is the gate of the main power device 31, and the source of the first power device Q5 is the source of the main power device 31. The source of the second normally open device Q6 is connected to the drain of the second power device Q7, the gate of the second power device Q7 is the gate of the sampling power device 32, and the source of the second power device Q7 is the source of the sampling power device 32 for connection to the voltage divider unit 41.

[0066] Optionally, the first normally open device Q4 and the second normally open device Q6 are normally open transistors, such as JFET, depletion-mode MOSFET (DMOS), depletion-mode gallium nitride (DGaN), etc. This embodiment does not limit the types of transistors used.

[0067] Optionally, the first power device Q5 and the second power device Q7 are semiconductor power devices such as MOSFET, IGBT, GaN, SiC MOSFET, JFET, etc. This embodiment does not impose any restrictions on them.

[0068] By using normally open devices with a mirror relationship, the gates and drains of the first normally open device Q1 and the second normally open device Q6 are connected together. The source of the first normally open device Q1 is connected to the drain of the first power device Q5 as the input of this pair of mirror transistors, and the source of the second normally open device Q6 is connected to the drain of the second power device Q7 as the output of this pair of mirror transistors. This allows the two normally open transistors to operate as a parallel common source and common gate, providing a stable and shared drain voltage for the power device below.

[0069] Since the main power device 31 and the sampling power device 32 are mirror power devices in this embodiment, and the first normally open device Q4 and the second normally open device Q6 are mirror switching devices, the first power device Q5 and the second power device Q7 are also mirror power devices. These two power devices are responsible for establishing a current replication relationship. After the input current flows into the first power device Q5, a mirror current is generated in the second power device Q7.

[0070] Meanwhile, the first normally open device Q4, the first power device Q5, the second normally open device Q6, and the second power device Q7 constitute a cascaded power switching device. Therefore, the two normally open transistors provide a stable source voltage applied to the drains of the two power devices below. In other words, the drain voltages of the first power device Q5 and the second power device Q7 are exactly the same, eliminating errors. Furthermore, having the same gate voltage allows the image mirroring ratio to reach the theoretically accurate value, enabling high-precision current sampling. For the subsequent circuitry, the signal output from the voltage divider unit 41 of the sampling module 4 to the protection module 5 will also be more accurate, allowing the protection module 5 to more precisely provide short-circuit protection for the power devices.

[0071] In this embodiment, when the control module 2 outputs a PWM drive signal to the gate of the first power device Q5, the current flows out from the drain of the first power device Q5 and into the source of the first normally open device Q4; the first normally open device Q4 transfers the current to the drain, and finally flows into the preset power supply 10; since the first normally open device Q4 and the second normally open device Q6 are mirror images of each other, the second normally open device Q6 transfers the same drain voltage to the source, and then to the drain of the second power device Q7, and finally outputs from the source of the second power device Q7 and transmits it to the voltage divider unit 41.

[0072] Furthermore, since power device 3 encapsulates the first normally open device Q4, the first power device Q5, the second normally open device Q6, and the second power device Q7, the operating junction temperatures of the four devices are almost identical. This consistent temperature ensures that the key parameters such as the threshold voltage and on-resistance of the devices change synchronously with temperature, forming a common-mode variation. This improves the temperature stability and accuracy of the sampling, avoiding drift caused by uneven local heating. Moreover, for circuit design, packaging reduces assembly difficulty, cost, and complexity, and improves circuit integration.

[0073] In this embodiment, by constructing a cascaded structure with a mirror relationship, the sampled current signal is stable and highly accurate, not easily affected by fluctuations in the preceding and following stage circuits, and is effectively isolated and attenuated by the common gate circuit. Furthermore, the cascaded structure splits the voltage, making the circuit more adaptable.

[0074] In the above Figure 10 Based on the provided embodiments, optionally, the first normally open device Q4 and the second normally open device Q6 are depletion-type normally open devices, and the first power device Q5 and the second power device Q7 are enhancement-mode low-voltage field-effect transistors.

[0075] Optionally, the first normally open device Q4 and the second normally open device Q6 can be depletion-type normally open devices such as JFET, DMOS, and DGaN, and this embodiment does not impose any restrictions on them; the first power device Q5 and the second power device Q7 can be enhancement-type low-voltage field-effect transistors such as N-channel or P-channel MOSFETs, and this embodiment does not impose any restrictions on them.

[0076] In this embodiment, the depletion-mode normally open device can enter the saturation operating region at a low drain-source voltage, and its own on-state voltage drop is small; while the enhancement-mode low-voltage MOSFET itself has a low threshold voltage and low on-resistance, requiring a low minimum drive voltage. Therefore, this combination allows the entire cascaded structure to operate normally at a very low power supply voltage, significantly reducing the voltage required for normal circuit operation; furthermore, since the depletion-mode normally open device has extremely high output impedance, the output current is not sensitive to changes in the downstream side, ensuring the stability and accuracy of sampling.

[0077] To more clearly explain the present invention, based on the above embodiments, in one possible implementation, the present application embodiment may also provide an example of an implementation of a short-circuit protection circuit for a power device. Figure 11 A schematic diagram of a short-circuit protection circuit for another power device provided in an embodiment of this utility model. (See diagram below.) Figure 11 As shown, power device 3 includes a first normally open device Q4, a first power device Q5, a second normally open device Q6, and a second power device Q7. The first normally open device Q4 and the first power device Q5 are N-channel JFETs, and the first power device Q5 and the second power device Q6 are N-channel enhancement-mode MOSFETs. Since the first normally open device Q1 and the second normally open device Q6 are mirror switches, the first power device Q5 and the second power device Q7 are also mirror power devices. The four devices together form a cascaded structure. In this embodiment, sampling module 4 includes a voltage divider unit 41, which consists of two resistors. Protection module 5 includes a first protection transistor Q2, a second protection transistor Q3, and a resistor R1. The first protection transistor Q2 is an NPN transistor, and the second protection transistor Q3 is a PNP transistor.

[0078] In this embodiment, when the control module 2 outputs a PWM drive signal to the gate of the first power device Q5, current flows out from the drain of the first power device Q5 and into the source of the first normally open device Q4; the first normally open device Q4 transfers the current to its drain, and finally flows into the preset power supply 10; since the first normally open device Q4 and the second normally open device Q6 are mirror images of each other, the second normally open device Q6 transfers the same drain voltage to its source, and then to the drain of the second power device Q7, and finally outputs from the source of the second power device Q7. The voltage is transmitted to the voltage divider unit 41, and the electrical parameters of the voltage divider unit 41 are used as the input to the first protection transistor Q2. When the input voltage meets the turn-on voltage of the first protection transistor Q2, the first protection transistor Q2 is turned on, and the current flows from the collector of the first protection transistor Q2 through the resistor R1, generating a voltage drop. This voltage drop makes the base voltage of the second protection transistor Q3 less than the emitter voltage, so that the second protection transistor Q3 is turned on. Finally, the emitter of the second protection transistor Q3 clamps the gate voltage of the first power device Q5, thereby achieving short-circuit protection.

[0079] In this embodiment, by constructing a cascaded power device with a mirror relationship and setting a protection module with dual drive, the reliability and robustness of the circuit are comprehensively improved, the short-circuit withstand capability of the power device is significantly enhanced, and the risk of damage to the power device is reduced.

[0080] The above description is merely a preferred embodiment of this utility model and is not intended to limit the scope of this utility model. Various modifications and variations can be made to this utility model by those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of this utility model should be included within the protection scope of this utility model.

Claims

1. A short-circuit protection circuit for a power device, characterized in that, The short-circuit protection circuit includes: a power device, a sampling module, and a protection module; The power device's gate is connected to the control module, its source is grounded, and its drain is connected to a preset power supply. The sampling module's input is connected to the power device's drain, its control terminal is connected to the power device's gate, its output is connected to the protection module's input, and its output is connected to the power device's gate.

2. The short-circuit protection circuit for the power device according to claim 1, characterized in that, The sampling module includes: a sampling tube and a voltage divider unit; The drain of the sampling tube is the input terminal of the sampling module and is used to connect to the drain of the power device. The gate of the sampling tube is the control terminal of the sampling module and is used to connect to the gate of the power device. The source of the sampling tube is grounded through the voltage divider unit, and the voltage divider point of the voltage divider unit is the output terminal of the sampling module, which is used to connect to the input terminal of the protection module.

3. The short-circuit protection circuit for the power device according to claim 2, characterized in that, The sampling tube is an enhanced low-voltage switching device.

4. The short-circuit protection circuit for the power device according to claim 1, characterized in that, The power device is a single semiconductor power device, and the protection module includes: a first protection transistor, the gate of the first protection transistor being the input terminal of the protection module, the drain of the first protection transistor being connected to the gate of the power device, and the source of the first protection transistor being grounded.

5. The short-circuit protection circuit for the power device according to claim 4, characterized in that, The protection module further includes a second protection transistor and a resistor. The gate of the second protection transistor is connected to the drain of the first protection transistor, the drain of the second protection transistor is grounded, and the source of the second protection transistor is also connected to the gate through the resistor. The source of the second protection transistor is used to connect to the output terminal of the protection module.

6. The short-circuit protection circuit for the power device according to claim 4, characterized in that, The first protection tube is an enhanced switching device.

7. The short-circuit protection circuit for the power device according to claim 2, characterized in that, The power device is any one of the following: silicon metal oxide semiconductor transistor (Si MOSFET), silicon carbide metal oxide semiconductor crystal (SiC MOSFET), and gallium nitride (GaN) power device.

8. The short-circuit protection circuit for the power device according to claim 1, characterized in that, The power device is a cascaded power switching device that encapsulates a main power device and a sampling power device, wherein the main power device and the sampling power device are mirror images of each other. The sampling module includes a voltage divider unit, wherein the source of the sampling power device in the cascaded power switching device is grounded through the voltage divider unit, and the voltage divider point of the voltage divider unit is the output terminal of the sampling module, which is used to connect to the input terminal of the protection module.

9. The short-circuit protection circuit for the power device according to claim 8, characterized in that, The main power device includes: a first normally open device and a first power device; the sampling power device includes: a second normally open device and a second power device. Wherein, the drain of the first normally open device and the drain of the second normally open device are connected, the gate of the first normally open device is connected to the gate of the second normally open device, and the first normally open device and the second normally open device are mirror switching devices of each other. The source of the first normally open device is connected to the drain of the first power device, the gate of the first power device is the gate of the main power device, and the source of the first power device is the source of the main power device. The source of the second normally open device is connected to the drain of the second power device, the gate of the second power device is the gate of the sampling power device, and the source of the second power device is the source of the sampling power device used to connect to the voltage divider unit.

10. The short-circuit protection circuit for the power device according to claim 9, characterized in that, The first normally open device and the second normally open device are depletion-type normally open devices, and the first power device and the second power device are enhancement-mode low-voltage field-effect transistors.

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