A system and method for high speed failure detection of a to247 packaged silicon carbide device

Abstract

The application discloses a high-speed fault detection system and method for a TO247 packaged silicon carbide device. The detection system comprises a TO247 packaged SiC MOSFET chip, a TMR current sensor and a fault detection unit. The TMR current sensor comprises a first TMR bridge arm, a second TMR bridge arm and an operational amplifier, the first TMR bridge arm and the second TMR bridge arm are symmetrical about a central axis. The left copper foil connected with the drain of the SiC MOSFET chip and the right copper foil connected with the source of the chip are also symmetrical about the central axis. The two TMR bridge arms comprise four TMR resistors R1-R4, forming a bridge structure. The operational amplifier is connected with the bridge structure. The TMR current sensor is connected with the fault detection unit, the obtained sampling current is input into the fault detection unit, and whether the SiC MOSFET chip has a short circuit fault is judged. The application adopts the TMR current sensor to shield the interference of external magnetic fields, and realizes the fast short circuit protection of the TO247 packaged SiC MOSFET.

Description

Technical Field

[0001] This invention belongs to the field of short-circuit and overcurrent protection technology, and relates to a high-speed fault detection system and method for silicon carbide devices in a TO247 package. Background Technology

[0002] Reliable short-circuit and overcurrent protection is crucial for the reliability of power electronic devices. Compared to Si IGBTs, SiC MOSFETs have a much faster short-circuit current rise rate and higher peak value, and a shorter short-circuit withstand time, requiring short-circuit fault detection and protection (current dropping to zero) to be completed within 3μs. The desaturation technology widely used in Si IGBTs is unsuitable for short-circuit and overcurrent protection of SiC MOSFETs, firstly because it cannot balance diagnostic speed and accuracy, and secondly because it cannot adapt to the significant temperature-dependent changes in the on-state voltage drop of SiC MOSFETs. Therefore, there is an urgent need to research reliable and fast short-circuit and overcurrent protection technologies for SiC MOSFETs to facilitate their large-scale application.

[0003] Researchers at home and abroad have proposed a variety of solutions for short-circuit and overcurrent protection of SiC MOSFETs, most of which directly obtain the current information flowing through the SiC MOSFET.

[0004] The simplest method for detecting current is to use Ohm's law to convert the current into a voltage signal. Inserting a sampling resistor into the power circuit of a SiC MOSFET allows obtaining the current information. However, this method is unsuitable for high-voltage, high-power applications due to issues such as losses, measurement noise, and large loop inductance. To overcome these drawbacks, a small portion of the SiC MOSFET chip can be dedicated to current sensing, a technique known as SenseFET technology. Mitsubishi Electric's FMF800DX-24A SiC MOSFET module utilizes this technology. Figure 1 The image shows the power chip and its equivalent circuit diagram, with the current i flowing through the Sense electrode. sense With the main circuit current i d Proportional, using resistance to convert i sense The signal is converted to a voltage signal for short-circuit and overcurrent protection. The sense electrode in the chip is isolated from the source electrode, reducing interference from the main power circuit to the current measurement. However, this method is not universal; most SiC MOSFET chips do not integrate a sense electrode, and such senseFET modules are also relatively expensive.

[0005] Faraday's law of electromagnetic induction can also be used to measure electric current. A typical method is as follows: Figure 2 As shown, an RC integrator circuit is used to integrate the L of the Kelvin inductor. k di / dt information is converted into voltage v c, will v c Short-circuit faults can be identified by comparing the signal to a threshold. Tennessee State University and Virginia Tech's CPES have used this circuit to achieve short-circuit fault detection and protection within 170 ns (discrete components) and 1.1 μs (1200V / 325A module), respectively. This method has a simple circuit, does not require a high-speed operational amplifier (low cost), and provides fast protection. However, it cannot be used for overcurrent protection; it is clearly only effective at high frequencies. The detection time for slowly changing overcurrent faults will be significantly longer, or even undetectable. Furthermore, the signal detection circuit of this method is not physically isolated from the main power circuit, making it easy for switching spikes to be transmitted to the current detection circuit, leading to false diagnoses.

[0006] The Rogowski coil is also a classic current detection method based on Faraday's law. The basic working principle of the Rogowski coil is as follows: Figure 3 As shown, the induction section is typically a ring-shaped structure containing hundreds of hollow coils. A charged conductor passes through this ring structure and forms a mutual inductance with it. The conductor current i d A voltage v is induced in the ring structure. r v r After integration, the current i can be obtained. d The AC component. Virginia Tech's CPES (Conductivity, Engineering, and Science) fabricated an integrated Rogowski coil using a multi-layer PCB. They employed an operational amplifier-based integrator circuit to increase bandwidth and added an additional shielding layer to reduce the impact of SiC MOSFET common-mode noise (dv / dt) on current sensing. This enabled them to detect SiC MOSFET short-circuit faults within 470 ns and softly turn them off. However, this method is costly. The operational amplifiers within the integrator typically have internal bias voltages and currents, which can cause output drift or even saturation. Solving this problem requires high-performance operational amplifiers, correction circuits, and reset switches, all of which increase the cost of the Rogowski coil. Commercial Rogowski coil sensors from LEM typically cost over $100. Furthermore, Rogowski coils cannot measure DC or low-frequency currents, making accurate overcurrent fault protection difficult.

[0007] Magnetic field sensors are components that convert static and dynamic magnetic fields into electrical signals, measuring both DC and AC components of current. Hall sensors are most widely used in power electronics; open-loop Hall sensors typically incorporate a magnetic core. d The generated magnetic field. Due to the hysteresis loss and skin effect of the magnetic core, the response speed of an open-loop Hall is generally slow. The response time of a commercially available open-loop Hall in the 100-ampere range (t...) r These are generally in the microsecond range, such as LEM HTFS 400-P / SP7(400A)t. r =3.5μs, Allegro ACS773(200A)t r=2.5μs. Due to its slow response speed, the open-loop Hall sensor is unsuitable for short-circuit protection of SiC MOSFETs. Furthermore, the linearity and bias voltage of the open-loop Hall sensor are significantly affected by temperature. Closed-loop Hall sensors can greatly improve dynamic response and reduce temperature drift, but they are bulky, expensive, and unsuitable for short-circuit and overcurrent protection of SiC MOSFETs.

[0008] The TO247 is the most commonly used package for single SiC MOSFETs, as shown in Figure 4. Major SiC device manufacturers such as Cree and Infineon all use this package. The TO247 package has a simple structure, containing only one SiC MOSFET chip, resulting in lower cost. It is used in low-power applications, typically ranging from several kW to tens of kW. This type of package requires a low-cost but extremely fast fault detection system and method. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a short-circuit fault detection system and method for a TO247 packaged SiC MOSFET. The system uses a TMR current sensor to shield the interference of external magnetic fields in order to achieve fast short-circuit protection for the TO247 packaged SiC MOSFET.

[0010] Therefore, the present invention adopts the following technical solution: a high-speed fault detection system for silicon carbide devices in a TO247 package, comprising a TO247 packaged SiC MOSFET chip, a TMR current sensor and a fault detection unit; the TO247 packaged SiC MOSFET chip is mounted on a PCB board.

[0011] The TMR current sensor includes a first TMR bridge arm, a second TMR bridge arm, and an operational amplifier. The first TMR bridge arm and the second TMR bridge arm are respectively placed on the left copper foil and the right copper foil on the PCB board. The first TMR bridge arm and the second TMR bridge arm are symmetrical about the central axis. The left copper foil connecting the drain of the SiC MOSFET chip and the right copper foil connecting the source of the chip are also symmetrical about the central axis.

[0012] The two TMR bridge arms contain a total of four TMR resistors R1-R4, forming a bridge structure;

[0013] The operational amplifier is connected to the bridge structure to amplify the voltage difference of the bridge structure. The amplified voltage difference is proportional to the current flowing through the SiC MOSFET chip.

[0014] The TMR current sensor is connected to the fault detection unit and inputs the obtained sampling current into the fault detection unit to determine whether the SiC MOSFET chip has a short circuit fault.

[0015] Furthermore, when the magnetic field is in the positive x direction, the resistance of the TMR current sensor increases approximately linearly with the increase of the magnetic field; when the magnetic field is in the negative x direction, the resistance of the TMR current sensor decreases approximately linearly with the increase of the magnetic field.

[0016] Furthermore, the four TMR resistors R1-R4 have the same sensitive direction, which is the positive x-direction.

[0017] Furthermore, current flows into the drain of the SiC MOSFET through the left copper foil, flows out from the source, and flows through the right copper foil; the left and right copper foils generate magnetic fields, with the magnetic field generated by the left copper foil pointing in the negative x direction and the magnetic field generated by the right copper foil pointing in the positive x direction. When the current flows through the TMR current sensor, the resistance values ​​of TMR resistors R1 and R2 decrease, while the resistance values ​​of TMR resistors R3 and R4 increase.

[0018] Furthermore, the first TMR bridge arm and the second TMR bridge arm receive magnetic fields of the same magnitude but opposite directions. Let the first TMR bridge arm receive -B and the second TMR bridge arm receive +B. When there is no magnetic field, the resistance value of the TMR current sensor is set to R. Then, when a magnetic field is present, the resistance values ​​of the TMR resistors R1 to R4 are respectively:

[0019] R1 = R2 = R - kB

[0020] R3 = R4 = R + kB

[0021] Where k is the sensitivity, and the outputs V1 and V2 of the left and right half-bridges are respectively:

[0022]

[0023]

[0024] In the formula, Vcc represents the supply voltage of TMR;

[0025] Therefore, the output of the bridge structure is:

[0026]

[0027] Let the current flowing through the SiC MOSFET be I. According to Ampere's law, let the relationship between the magnetic field B and the current I at the first and second TMR bridge arms be:

[0028]

[0029] Where, μ o Let L be the permeability, and L be the equivalent distance between the first and second TMR bridge arms and the current. Then we obtain:

[0030]

[0031] Assume that the operational amplifier can amplify Δv by N times, then the output of this TMR current sensor is:

[0032] Vo = NΔv = NV CC S·I

[0033] As can be seen from above, the TMR current sensor can measure the current I flowing through the SiC MOSFET.

[0034] Furthermore, assume that the interference magnetic field B1 is a magnetic field in the same direction, which will cause:

[0035] R1 = R2 = R3 = R4 = R + kB1

[0036] Then the output of the bridge structure:

[0037] Δv = V1 - V2 = 0

[0038] Therefore, the interference magnetic field B1 will not be sensed by the TMR current sensor, achieving the shielding of the interference magnetic field.

[0039] Furthermore, the described fault detection unit includes a comparator, a counter, and an isolator connected in series in sequence.

[0040] Furthermore, the count value cnt of the counter is forced to become 0 through the Rst signal.

[0041] Furthermore, the described TMR current sensor is separately encapsulated into a chip or is encapsulated into a chip together with the fault detection unit.

[0042] Another technical solution adopted by the present invention is: a method for high - speed fault detection of a silicon carbide device with a TO247 package, adopting the above - mentioned high - speed fault detection system for silicon carbide devices, which includes:

[0043] First step, use a TMR current sensor to detect the current;

[0044] Second step, the output voltage Vo of the TMR current sensor is calculated to obtain the sampled current I, and compared with the preset threshold current Ith. When I ≤ Ith, the comparator outputs v3 as a low level, and return to the first step; when I > Ith, the comparator outputs v3 as a high level, and enter the third step;

[0045] Third step, when v3 is at a high level, the count value cnt of the counter starts to be calculated. When cnt exceeds N, the output v4 of the counter is set to a high level, and enter the fourth step; if cnt < N and v3 becomes a low level, then cnt will be set to 0, and return to the first step;

[0046] Fourth, the high level of v4 is transmitted to the driver chip through the isolator, forcibly turning off the SiC MOSFET to prevent the SiC MOSFET from being damaged due to overheating.

[0047] The beneficial effects of this invention are as follows: (1) The TMR current sensor is used to shield the interference of external magnetic fields, realizing fast short-circuit protection of SiC MOSFET in TO247 package; (2) The TMR current sensor only needs to be fixed on the PCB, and has no electrical connection with the main power, which is small in size and easy to install; (3) The short-circuit detection time is less than 200ns, which is much faster than the desaturation technology (>500ns); (4) It is a reliable and fast short-circuit and overcurrent protection technology for SiC MOSFET, which helps the large-scale promotion and application of SiC MOSFET. Attached Figure Description

[0048] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0049] Figure 1 Equivalent circuit diagram of a SiC MOSFE chip with integrated current measurement terminals;

[0050] Figure 2 This is a short-circuit detection circuit diagram based on Kelvin inductors;

[0051] Figure 3 This is a short-circuit detection diagram based on an integrated Rogowski coil;

[0052] Figure 4a This is a diagram of the TO247-3 package structure.

[0053] Figure 4b This is a diagram of the TO247-4 package structure.

[0054] Figure 5 This is a schematic diagram of the TO247 soldered onto a PCB board.

[0055] Figure 6 This is a structural diagram of the internal structure of a TMR current sensor according to the present invention (specifically for TO247-4);

[0056] Figure 7 This is a diagram showing the internal structure of another TMR current sensor according to the present invention (specifically for TO247-3);

[0057] Figure 8 This is a flowchart of the short-circuit fault detection process of the present invention;

[0058] Figure 9 This is a timing diagram of the short-circuit fault detection unit of the present invention. Detailed Implementation

[0059] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] TO247 is the most commonly used package for single SiC MOSFETs, such as... Figure 4a and Figure 4b As shown, major SiC device manufacturers such as Cree and Infineon all use this package. The TO247 package has a simple structure, containing only one SiC MOSFET chip, and is relatively inexpensive. It is used in low-power applications, typically for power ratings of several kW to tens of kW. This type of package requires a low-cost but extremely fast fault detection method.

[0061] This embodiment provides a short-circuit fault detection system for a TO247-packaged SiC MOSFET, including a TO247-packaged SiC MOSFET chip, a TMR current sensor, and a fault detection unit. The TO247-packaged SiC MOSFET chip is mounted on a PCB board, as shown below. Figure 5 As shown, 1 represents a TO247 packaged SiC MOSFET, 2 is a pad, 3 is the PCB board, and 4 is the TMR current sensor. 31 is the left copper foil connecting to the drain of the SiC MOSFET. 32 is the right copper foil connecting to the source of the SiC MOSFET. The TMR current sensor only needs to be placed on top of the PCB, has no electrical contact with the main power supply, and is small in size and easy to install.

[0062] Figure 6The internal structure of the TMR current sensor is shown, comprising two TMR bridge arms (TMR1 and TMR2) and one operational amplifier. TMR1 and TMR2 are symmetrical about the central axis; the left copper foil 31 and the right copper foil 32 are also symmetrical about the central axis. The two TMR bridge arms contain a total of four TMR resistors (R1-R4), forming a bridge structure. The upward arrows for R1-R4 indicate that the resistance increases with the magnetic field in the TMR sensing direction (positive x-direction): when the magnetic field is in the positive x-direction, the TMR resistance increases approximately linearly with the increase of the magnetic field; when the magnetic field is in the negative x-direction, the TMR resistance increases but decreases approximately linearly. Magnetic fields in the y or z directions do not cause a change in the TMR resistance. The TMR current sensor also includes an operational amplifier (op-amp), which amplifies the voltage difference (V1-V2) of the TMR bridge structure.

[0063] like Figure 6 As shown, the SiC MOSFET will flow with the current indicated by the arrow when it is turned on or during a short-circuit fault. The current flows into the drain of the SiC MOSFET through the left copper foil 31, exits from the source, and flows through the right copper foil 32. The left copper foil 31 and the right copper foil 32 will generate a magnetic field, and according to the right-hand rule, the direction of the magnetic field is as follows: Figure 6 As shown, the magnetic field generated by the left copper foil 31 points in the negative x-direction, while the magnetic field generated by the right copper foil 32 points in the positive x-direction. Thus, when current flows through the TMR current sensor, the resistances of R1 and R2 decrease, while the resistances of R3 and R4 increase. Figure 6 TMR1 and TMR2 are symmetrical about the central axis, and the left copper foil 31 and right copper foil 32 are also symmetrical about the central axis. Therefore, the magnetic fields received by TMR1 and TMR2 are of the same magnitude but opposite in direction. Let's assume that TMR1 receives -B and TMR2 receives +B. Without a magnetic field, let the resistance of the TMR be R. Then, with a magnetic field, the resistances of R1 to R4 are respectively:

[0064] R1 = R2 = R - kB

[0065] R3 = R4 = R + kB

[0066] Where k is the sensitivity. The outputs V1 and V2 of the left and right half-bridges are respectively:

[0067]

[0068]

[0069] Therefore, the output of the bridge structure can be obtained as follows:

[0070]

[0071] Let the current flowing through the SiC MOSFET be I. According to Ampere's law, let the relationship between the magnetic field B at TMR1 and TMR2 and the current I be:

[0072]

[0073] Where, μ o Let be the permeability, and L be the equivalent distance between TMR1, TMR2 and the current. Therefore, we can obtain:

[0074]

[0075] Assuming the operational amplifier can amplify Δv by a factor of N, then the output of the TMR current sensor is:

[0076] Vo = NΔv = NV CC S·I

[0077] As can be seen, the TMR current sensor can measure the current I flowing through the SiC MOSFET.

[0078] The advantage of this TMR current sensor is that its measurements are unaffected by interfering magnetic fields. The sources of interfering magnetic fields are generally located far from the TMR current sensor, and can be approximated as magnetic fields in the same direction. For example... Figure 6 The interference magnetic field B1 shown will cause

[0079] R1 = R2 = R3 = R4 = R + kB1

[0080] The output of the bridge structure is:

[0081] Δv=V1-V2=0

[0082] Therefore, the interfering magnetic field B1 will not be sensed by the TMR, thus achieving shielding against the interfering magnetic field. The arrangement of this TMR current sensor for the TO247-3 is similar, as follows... Figure 7 As shown.

[0083] use Figure 6 The current measured by the current sensor shown can be used to protect the SiC MOSFET. The short-circuit fault detection flowchart is as follows: Figure 8 As shown, the corresponding timing diagram is as follows: Figure 9 As shown.

[0084] The steps of the short-circuit fault detection process are as follows:

[0085] The first step is to use a TMR current sensor to detect the current;

[0086] In the second step, the output voltage Vo of the TMR current sensor is calculated to obtain the sampled current I, which is compared with the preset threshold current Ith. When I ≤ Ith, the comparator output v3 is at a low level, and it returns to the first step; when I > Ith, the comparator output v3 is at a high level, and it enters the third step;

[0087] In the third step, when v3 is at a high level, the count value cnt of the counter starts to be calculated. When cnt exceeds N, the counter output v4 is set to a high level, and it enters the fourth step; if cnt < N and v3 becomes low level, then cnt will be set to 0, and it returns to the first step;

[0088] In the fourth step, the high level of v4 is transmitted to the driver chip through the isolator to forcibly turn off the SiC MOSFET, avoiding damage to the SiC MOSFET due to overheating.

[0089] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the technical principle of the present invention, several improvements and modifications can be made, and these improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A high-speed fault detection system for silicon carbide devices in a TO247 package, characterized in that, It includes a SiC MOSFET chip in a TO247 package, a TMR current sensor, and a fault detection unit; the SiC MOSFET chip in the TO247 package is mounted on a PCB board; The described TMR current sensor includes a first TMR bridge arm, a second TMR bridge arm, and an operational amplifier. The first TMR bridge arm and the second TMR bridge arm are respectively placed on the left copper foil and the right copper foil of the PCB board, and the first TMR bridge arm and the second TMR bridge arm are symmetrical about the central axis; the left copper foil connected to the drain of the SiC MOSFET chip and the right copper foil connected to the source of the chip are also symmetrical about the central axis; The two TMR bridge arms together include 4 TMR resistors R1 - R4, forming a bridge structure; The described operational amplifier is connected to the bridge structure and is used to amplify the voltage difference of the bridge structure. The amplified voltage difference is proportional to the current flowing through the SiC MOSFET chip; The described TMR current sensor is connected to the described fault detection unit, and inputs the acquired sampled current into the fault detection unit to judge whether there is a short - circuit fault in the SiC MOSFET chip.

2. A high - speed fault detection system for a silicon carbide device in a TO247 package according to claim 1, wherein, When the magnetic field is in the positive x - direction, the resistance value of the TMR current sensor increases approximately linearly with the increase of the magnetic field; when the magnetic field is in the negative x - direction, the resistance value of the TMR current sensor decreases approximately linearly with the increase of the magnetic field.

3. The high-speed fault detection system for a TO247 packaged silicon carbide device according to claim 1, characterized in that, The sensitive directions of the 4 TMR resistors R1 - R4 are the same, all in the positive x - direction.

4. A high - speed fault detection system for a silicon carbide device in a TO247 package according to claim 1, wherein, The current flows into the drain of the SiC MOSFET through the left copper foil, flows out from the source, and flows through the right copper foil; the left copper foil and the right copper foil generate magnetic fields. The magnetic field generated by the left copper foil points in the negative x - direction, and the magnetic field generated by the right copper foil points in the positive x - direction. When flowing through the TMR current sensor, the resistance values of TMR resistors R1 and R2 decrease, and the resistance values of TMR resistors R3 and R4 increase.

5. A high-speed fault detection system for a TO247 packaged silicon carbide device according to claim 4, characterized in that, The first and second TMR bridge arms receive magnetic fields of the same magnitude but opposite directions. Assume the first TMR bridge arm receives -B and the second TMR bridge arm receives +B. When there is no magnetic field, the resistance value of the TMR current sensor is set to... R When a magnetic field is present, the resistance values ​​of TMR resistors R1~R4 are respectively: Where k is the sensitivity, and the output of the left and right half-bridges. V1 and V2 They are respectively: In the formula, Vcc This indicates the supply voltage of the TMR; Thus, the output of the bridge structure is: Let the current flowing through the SiC MOSFET be... I According to Ampere's law, let the magnetic field B and current at the first TMR bridge arm and the second TMR bridge arm be respectively. I The relationship is: in, Permeability, L Given the equivalent distances between the first and second TMR bridge arms and the current, we obtain: Suppose that the operational amplifier can If the signal is amplified by N times, the output of the TMR current sensor will be: As can be seen from the above, the TMR current sensor can measure the current flowing through the SiC MOSFET. I .

6. A high-speed fault detection system for a TO247 packaged silicon carbide device according to claim 5, characterized in that, Assume that the interference magnetic field B1 is a magnetic field in the same direction, which will cause: Then the output of the bridge structure: Therefore, the interference magnetic field B1 will not be sensed by the TMR current sensor, achieving the shielding of the interference magnetic field.

7. A high-speed fault detection system for a TO247 packaged silicon carbide device according to claim 1, characterized in that, The described fault detection unit includes a comparator, a counter, and an isolator connected in series in sequence.

8. A high-speed fault detection system for a TO247 packaged silicon carbide device according to claim 7, characterized in that, The count value cnt of the counter is forced to be 0 through the Rst signal.

9. A high-speed fault detection system for a TO247 packaged silicon carbide device according to claim 1, characterized in that, The described TMR current sensor is separately packaged into a chip or is packaged together with the fault detection unit into a chip.

10. A high-speed fault detection method for a TO247 packaged silicon carbide device, employing the high-speed fault detection system for silicon carbide devices as described in any one of claims 1-9, characterized in that, It includes: The first step, using a TMR current sensor to detect current; The second step involves calculating the sampling current by taking the output voltage Vo of the TMR current sensor. I Compared with the preset threshold current Ith, when I When ≤Ith, the comparator output v3 is low, returning to step one; when I When >Ith, the comparator outputs v3 as high, and proceeds to the third step; The third step, when v3 is at a high level, the count value cnt of the counter starts to count. When cnt exceeds N, the output v4 of the counter is set to a high level, and it enters the fourth step; if cnt < N and v3 becomes a low level, then cnt will be set to 0 and return to the first step; Fourth, the high level of v4 is transmitted to the driver chip through the isolator, forcibly turning off the SiC MOSFET and preventing the SiC MOSFET from being damaged due to overheating.

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