SiC-MOSFET high-frequency switching current detection circuit based on Rogowski coil

Abstract

The present invention discloses a SiC-MOSFET high-frequency switch current detection circuit based on a Rogowski coil, comprising a Rogowski coil differentiator equivalent circuit, wherein the Rogowski coil differentiator equivalent circuit is connected to a common-phase integration circuit; the output terminal of the common-phase integration circuit is connected to a filter holding circuit; the filter holding circuit comprises a first analog switch, wherein the first analog switch is connected to a second analog switch through a first low-pass filter circuit, and the second analog switch is connected to a subtraction circuit through a follower; and the subtraction circuit is connected to a dual-path comparator. The present invention realizes high-precision and low-delay detection of SiC MOSFET switch current.

Description

Technical Field

[0001] The invention relates to a switch current detection technology for a power electronic device, in particular to a SiC-MOSFET high-frequency switch current detection circuit based on a Rogowski coil. Background Art

[0002] The third generation semiconductor power electronic device SiC-MOSFET is increasingly favored in high efficiency and high power density applications due to its advantages such as high switching frequency and low on-state resistance. Compared with traditional Si IGBT devices, SiCMOSFET chips have smaller area and higher current density. When a short circuit or overcurrent fault occurs, the temperature of the power device rises sharply, causing serious damage to the device. In order to protect the power device from damage, the drive system must have a faster response speed to short circuit or overcurrent faults, and the response time is generally required to be within 10us. Therefore, how to quickly detect the switching current state information of SiC-MOSFET is crucial to responding to short circuit and overcurrent faults of SIC MOSFET.

[0003] The traditional desaturation detection method has achieved good results in overcurrent protection of Si-MOSFET and has been widely integrated in driver modules. However, due to the fact that the desaturation effect of SiC-MOSFET is not obvious and the saturation voltage is greatly affected by temperature, the desaturation detection method is not effective in the application of SiC-MOSFET. In view of the high operating frequency and fast rise of short-circuit current of SiC-MOSFET, the Rogowski coil, which is sensitive to rapidly changing current, has become a new choice for SiC-MOSFET protection. However, it has the inherent defect that the low-frequency gain of the Rogowski coil differentiator is too low, which produces a DC bias. Simply increasing the low-frequency gain of the integration circuit will lead to a decrease in stability. Although improvement measures can be taken (such as CN108414812A), this defect cannot be fundamentally compensated. The reason is that the mutual inductance of the PCB embedded Rogowski coil for SiC-MOSFET switch current measurement is generally at the nH level (the sensor volume is limited). No matter how the circuit is improved, if the DC bias needs to be eliminated, the integration circuit still needs a large amplification factor in the low frequency band, which will cause the error voltage caused by the non-ideal factors of the op amp to be seriously amplified. Therefore, it is difficult to find a compromise solution. After comparing several integration circuits, some literature has concluded that when designing an integration circuit, a trade-off should be made between suppressing low-frequency gain and suppressing DC bias. Therefore, it is difficult to solve the DC bias problem in principle by improving the integration circuit alone. Some scholars have proposed a method of switch reset, but its application is limited when the switching current frequency is low. There is currently no more universal design solution for the parameter optimization design of the Rogowski coil measurement module for SiC-MOSFET. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a SiC-MOSFET high-frequency switching current detection circuit based on a Rogowski coil in view of the shortcomings of the prior art, solve the problem of droop distortion of the existing Rogowski coil current sensor, and realize high-precision and low-delay detection of the SiC MOSFET switching current.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a SiC-MOSFET high-frequency switching current detection circuit based on a Rogowski coil, including a Rogowski coil differentiator equivalent circuit, and the Rogowski coil differentiator equivalent circuit is connected to a common-phase integration circuit; characterized in that the output end of the common-phase integration circuit is connected to a filter holding circuit; the filter holding circuit includes a first analog switch, the first analog switch is connected to a second analog switch through a first low-pass filter circuit, and the second analog switch is connected to a subtraction circuit through a follower; the subtraction circuit is connected to a dual-path comparator; wherein the input end of the first analog switch, the negative input end of the subtraction circuit, and the positive input end of the follower input the original integrated signal output by the common-phase integration circuit; the positive input end of the follower samples the signal; the positive input end of the dual-path comparator inputs a signal obtained after eliminating the DC bias of the original integrated signal; the positive input end of the follower is connected to the positive end of the holding capacitor; the negative end of the holding capacitor is grounded.

[0006] The present invention first integrates the signal output by the Rogowski coil differentiator through a common-phase integration circuit. To solve the problem of DC bias, the present invention offsets the output signal bias through a filter holding circuit to achieve DC gain compensation. It also has strong stability, and finally achieves low-distortion and low-delay restoration of the current waveform, and outputs an overcurrent protection signal in time through a comparator. The present invention solves the problem of droop distortion of the existing Rogowski coil current sensor, can accurately and low-delay measure the SiC-MOSFET switch current, and outputs an overcurrent signal in time, ensuring that the protection of the SiC-MOSFET is quickly activated when overcurrent occurs.

[0007] When U PWM =0 and U last =1 and when, the sampling signal is enabled; wherein, U PWM is the PWM drive signal of SiC-MOSFET. PWM At the falling edge of , the first monostable circuit is triggered, and the second monostable circuit is triggered after a delay of Δt1. At this time, the delay signal U last =1, after delay Δt2, U last =0, ensuring the accuracy of DC component sampling time.

[0008] The comparator output terminal is connected to the gate of MOSFET M1; the comparator positive input terminal input is (1 / 2)U PWM_H , UPWM_H is the voltage when the PWM drive signal of SiC-MOSFET is at a high level; the negative input terminal of the comparator is connected to the output terminal of the second low-pass filter; the input of the second low-pass filter is U PWM .

[0009] One end of the delay capacitor is connected in series with the drain of M1, and the source of M1 is connected to the negative end of the capacitor of the second monostable circuit; When t2 is on, the MOSFET switch is turned on, extending the time Δt2; otherwise, the MOSFET switch is turned off, so that the sampling time is appropriately extended when the SiC-MOSFET is turned off for a long time, thereby improving the sampling accuracy.

[0010] The negative input terminal of the dual comparator inputs the threshold value U thr ; Among them, I thr is the protection threshold of the measured current; M is the mutual inductance of the Rogowski coil; R1 and C1 are the input resistance and capacitance of the in-phase integration circuit, respectively, so that an overcurrent signal is issued when the measured current exceeds the protection threshold.

[0011] Among them, l1 is the inner diameter of the Rogowski coil, c is the turn spacing, and l2 is the outer diameter of the Rogowski coil. This formula describes the functional relationship between mutual inductance and inner diameter. It is convenient to use MATLAB and other software to obtain the maximum value of mutual inductance M under certain restrictions, thereby increasing the sensitivity of the sensor.

[0012] The calculation formula of the original integrated signal output by the in-phase integration circuit is:

[0013]

[0014] Among them U out_org is the original integrated signal output by the in-phase integration circuit, U in is the output voltage of the Rogowski coil, I is the measured current, R1 and C1 are the resistance and capacitance of the common-phase input terminal of the common-phase integration circuit, R2 is the resistance from the common-phase input terminal to the ground, and R3 and C2 are the feedback resistance and capacitance from the inverting input terminal to the output of the common-phase integration circuit. The introduction of feedback can reduce the low-frequency gain and improve stability.

[0015] Among them, f osc is the switching oscillation frequency of the MOSFET, f sw is the switching frequency. R3, R D The value of can improve the frequency response of the in-phase integrator circuit and enhance stability.

[0016] The calculation formula of the original integrated signal output by the in-phase integration circuit is: Among them, I is the current to be measured; M is the mutual inductance of the Rogowski coil; R1 and C1 are the input resistance and capacitance of the in-phase integration circuit respectively.

[0017] The Rogowski coil differentiator includes four layers of PCB boards; the upper surface of the top PCB board and the lower surface of the bottom PCB board are covered with an outer shielding layer of the same size as the PCB board; through holes are provided on the four layers of PCB boards; the top PCB board and the bottom PCB board are connected by a plurality of winding turns in series, and the plurality of winding turns in series pass through the through holes of the corresponding layers of PCB boards; the return turns on the middle two layers of PCB boards are connected in parallel, and the two return turns are correspondingly wound on the middle two layers of PCB boards through the through holes on the middle two layers of PCB boards; the head end of the winding turn is connected to the end of the two return turns, and the end of the winding turn is connected to the head end of the two return turns. The use of the outer shielding layer can avoid the use of 6-layer boards and buried holes in PCB design, thereby reducing costs.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. The present invention uses the law of electromagnetic induction to establish a mathematical model of the mutual inductance of the Rogowski coil differentiator, takes the maximum mutual inductance under the same size as the optimization goal, calculates the optimal number of turns and inner diameter of the Rogowski coil, and designs a 4-layer PCB shielding structure to improve the anti-interference performance of the differentiator and then according to the coil stray parameters.

[0020] 2. The present invention takes high bandwidth and flat output gain as optimization goals, designs a conditioning circuit, calculates the steady-state bias during the device off time through sampling, filtering and holding circuits, and finally uses a subtraction circuit to eliminate the bias, thereby achieving high-precision, low-delay detection of SiCMOSFET switching current. The present invention is of great significance for accurate detection of high-frequency switching current and rapid overcurrent protection of SiC-MOSFET. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the Rogowski coil differentiator according to an embodiment of the present invention.

[0022] Figure 2 The present invention is a cascade circuit diagram of a Rogowski coil differentiator and a same-direction integration circuit according to an embodiment of the present invention.

[0023] Figure 3 It is a timing diagram of a bias sampling signal and a circuit diagram of a bias sampling signal generation circuit according to an embodiment of the present invention.

[0024] Figure 4 It is a circuit diagram of a sampling-filtering-holding circuit according to an embodiment of the present invention.

[0025] Figure 5It is a comparison diagram of the drain current waveform of the lower bridge arm SiC-MOSFET in the BUCK converter measured by the Rogowski coil current sensor of the embodiment of the present invention and the commercial Rogowski coil current sensor TRCP0300. DETAILED DESCRIPTION

[0026] The embodiment of the present invention establishes a mathematical model of the mutual inductance of the Rogowski coil differentiator, determines the optimal number of turns and inner diameter of the Rogowski coil according to the constraint conditions, designs a low-cost 4-layer PCB Rogowski coil, integrates the signal output by the differentiator using a common-phase integration circuit, offsets the output signal bias through a bias sampling circuit and a subtraction circuit, and realizes low-distortion and low-delay restoration of the current waveform and timely output of the overcurrent protection signal.

[0027] Based on the basic structure of the Rogowski coil differentiator and the law of electromagnetic induction, the magnetic flux of the rectangular wire turns at any position of the coil is established as a function of the distance from the measured current-carrying conductor and the coil height, as shown below:

[0028]

[0029] Where φ1 is the magnetic flux of the wire turns, I is the current to be measured, l1 is the inner diameter of the coil, l2 is the outer diameter of the coil, taking the maximum value, l3 is the horizontal distance from the wire turns to the axis of the conductor to be measured, h is the height of the coil, taking the conventional value of the PCB thickness, and μ0 is the magnetic permeability of the vacuum. To obtain the mutual inductance of the coil, first accumulate the magnetic flux of all the wire turns to obtain the coil flux, and then divide it by the conductor current, as shown below:

[0030]

[0031] Where Ψ is the total flux of the coil, n is the number of coil turns, c is the turn spacing, and the minimum value is taken. There is the following constraint relationship between the number of turns and the inner diameter:

[0032]

[0033] Thus, the mutual inductance M of the coil is obtained as a single variable function of the inner diameter l1 of the coil:

[0034]

[0035] For safety and electromagnetic interference prevention, l1>r+d is required, where r is the maximum radius of the current-carrying conductor and d is the safe distance between the inner side of the coil and the conductor under different voltages. Under the constraint of l1>r+d, find the maximum value M of the function M=f(l1) maxAs the optimal mutual inductance, l1 and n are the optimal number of turns and the optimal inner diameter. Among them, r is the maximum radius of the conductor to be measured, and d is the safe distance from the conductor to the inside of the coil under different voltage levels, so as to obtain the optimal inner diameter and number of turns, and design a 4-layer PCB Rogowski coil according to these parameters. A single-sided copper-clad plate of the same size as the PCB is covered on the upper and lower layers of the 4-layer PCB Rogowski coil as the outer shielding layer, and fixed with nylon screws.

[0036] Determine the inner diameter, outer diameter, height, and number of turns of the coil, and design a 4-layer PCB Rogowski coil. The coil includes two parts: a winding wire and a return wire. The winding wire is a plurality of turns in series (the winding direction of the plurality of turns is the same), and the return wire is two identical square turns in parallel. The winding wire and the return wire are connected in series. When current is passed through the inner conductor of the coil (i.e., the current-carrying conductor 11 to be measured), the winding wire can generate a voltage proportional to the differential of its current, thereby realizing the function of a differentiator; and when current is passed through the outer conductor of the coil, the return wire will induce a voltage opposite to the winding direction, thereby reducing external interference. The winding wire is arranged on the first and fourth layers of PCB boards (i.e., the top PCB board 1 and the bottom PCB board 2). The winding wires of the first and fourth layers are connected by through-holes instead of the buried hole connection commonly used in the prior art, thereby reducing costs. A plurality of through holes 5 are provided on the first and fourth layers. The winding wire 6 is wound from a through hole of the first layer, passes through a through hole at a corresponding position of the fourth layer, and then wound to the remaining through holes at corresponding positions of the first layer. Similarly, the winding wire has a head end and a tail end. The two parallel turns 7 of the return wire are arranged on the two middle layers (i.e., the second PCB board 3 and the third PCB board 4), respectively. The side length of the parallel turns is (l1+l2) / 2, and the start end of the parallel turns is connected to the tail end of the winding wire. The head end of the winding wire and the tail end of the return wire constitute the two output ends of the Rogowski coil.

[0037] In order to weaken the electromagnetic interference caused by the instantaneous potential jump of the measured conductor during high-frequency switching, the following design is adopted for the outer shielding layer. The outer shielding layer 8 is two single-sided copper-clad PCB boards, which are fixed to the upper surface of the first layer PCB board and the lower surface of the second layer PCB board with nylon screws (fixing holes 9 are provided on the outer shielding layer, and fixing holes 10 are provided on the PCB board at the corresponding position to facilitate the fixing of the nylon screws), and the lead wire is connected to the source of the SiC-MOSFET. In practical applications, the distance between the outer shielding layer and the coil can be adjusted to achieve a balance between the shielding strength and the coil bandwidth.

[0038] In order to restore the measured current, the output signal of the Rogowski coil differentiator is connected to the input of the in-phase integration circuit. The transfer function of the integration circuit is as follows:

[0039]

[0040]

[0041] Among them U out_org is the original integrated signal output by the in-phase integration circuit, U in is the output voltage of the Rogowski coil, I is the measured current, R1 and C1 are the resistance and capacitance of the in-phase input terminal of the integration circuit, R2 is the resistance from the in-phase input terminal to the ground, and R3 and C2 are the feedback resistance and capacitance from the inverting input terminal to the output. S ,C S ,L S The resistance, self-inductance and stray capacitance of the Rogowski coil are measured respectively. In practical applications, these three parameters can be measured by an impedance analyzer. The switching oscillation frequency f of the MOSFET is measured using the Rogowski coil differentiator described in step 1. osc , assuming the switching frequency is f sw , assuming that:

[0042] R1C1=R2C2

[0043]

[0044]

[0045] R D / / R1>>|R S +jω osc L S |

[0046] Under ideal conditions, U out_org The relationship with the measured current can be simplified as follows:

[0047]

[0048] To meet the above conditions, first determine the gain of the integration circuit according to the sensitivity and range requirements. To increase the input impedance of the integrator circuit to meet R without changing the gain D / / R1>>|R S +jω osc L S |, C1=C2, and then according to Determine R1C1. Generally, C1 is taken as a smaller value and R1 is taken as a larger value. Then C1=C2R1=R2. In order to leave a certain margin, take

[0049] In practical applications, due to factors such as capacitor leakage current and op amp offset voltage, U out_org The DC component of U is often not zero, and the deviation of this DC component is called the DC bias of the integrator circuit. Therefore, it is necessary to enable the bias calculation circuit when the SiC-MOSFET is turned off. out_orgSampling and calculating bias. A monostable delay circuit is used to implement this function, as follows: 1 represents a high level and 0 represents a low level. Assume that the signal is the drive signal U of the SiC-MOSFET in each switching cycle. PWM =1 is t0, and the delay from t0 to the steady-state shutdown of SiC-MOSFET is measured and set as Δt1. The time of several current oscillation cycles when SiC-MOSFET is turned off is set as Δt2. Δt2 is the sampling time of each bias calculation. This delay is determined by the delay of the filter in the bias calculation circuit.

[0050] When U is detected PWM The falling edge of triggers the monostable circuit 1, and the delay time is Δt1. After Δt1, the monostable circuit 2 is triggered, and the delay signal U last =1, after delay time Δt2, let U last =0. When U PWM =0 and U last =1 and the bias calculation circuit is enabled, thereby ensuring that the bias calculation is stopped before the SiC-MOSFET is turned on and the calculation result is kept until the next calculation.

[0051] To improve the sampling accuracy, the sampling time is extended accordingly when the SiC-MOSFET is turned off for a long time. A high-speed, low-power MOSFET M1 is used, and a capacitor is connected in series with the capacitor in the monostable circuit 2 in parallel, so that Δt2 increases appropriately when M1 is turned on. Then, U PWM Perform low-pass filtering to obtain the fundamental component U PWM_LPF , use the comparator to detect whether the following conditions are met:

[0052]

[0053] Among them U PWM_H is the voltage of PWM high level. If the condition is met, M1 is turned on and the delayed sampling time Δt2 is increased, otherwise M1 is turned off.

[0054] In order to calculate and maintain the DC bias in each switching cycle, a sampling-filtering-holding circuit is designed. out_org The high-speed analog switch S1 is connected to the third-order Sallen & Key type active low-pass filter circuit. The selection of the filter cut-off frequency should balance the attenuation multiple of the high-frequency switching current oscillation and the delay of the filter. The output of the filter circuit is connected to a ceramic capacitor with a small leakage current through a high-speed analog switch S2, and then a high input impedance follower is used to connect the capacitor voltage U DC Output, its workflow is as follows:

[0055] When the bias calculation circuit is enabled, open the analog switches S1 and S2 to out_orgWhen the sampling signal is locked, S1 and S2 are closed. Since the analog switch and the follower are both in high impedance state, U DC Then through the subtraction circuit, U out_org with U DC Subtract, and finally achieve the purpose of eliminating the bias. Use two comparators to output overcurrent signals, assuming:

[0056]

[0057] Among them U thr is the comparator threshold, I thr is the protection threshold of the measured current. out >U thr or U out <-U thr When the overcurrent signal U OC Set high, otherwise set low.

[0058] Figure 2 This is a cascade circuit diagram of a Rogowski coil differentiator and a same-direction integration circuit according to an embodiment of the present invention. The specific implementation steps of parameter design are as follows:

[0059] Step 1: Use an impedance analyzer to measure the coil parameter R S, C S, L S

[0060] Step 2: Use the Rogowski coil differentiator to measure the switching oscillation frequency f of the MOSFET osc

[0061] Step 3: Determine the gain of the integration circuit according to the required sensitivity and range

[0062] Step 4: According to Determine the size of R1C1. Generally, C1 is taken as a smaller value and R1 is taken as a larger value. Then R2=R1, C2=C1R

[0063] Step 5: Complete the parameter design of the integrator circuit.

[0064] Figure 3 The following is a sampling signal timing diagram and a sampling signal generation circuit diagram of an embodiment of the present invention. Two monostable circuits 1 (the first monostable circuit) and monostable circuit 2 (the second monostable circuit) are constructed using a monostable chip, and their outputs are U delay and U last, configure the RC parameters so that their delays are Δt1 and Δt2, where Δt1 is the time from the falling edge of the PWM signal to the steady-state shutdown of the SiC-MOSFET, and Δt2 is the sampling time. When the falling edge of the PWM signal arrives, the monostable circuit 1 is triggered, and when the timing of the monostable circuit 1 ends, the monostable circuit 2 is triggered. Use a logic gate circuit so that U PWM and U last Enable sampling signal U sample , for U out_org Sample and calculate the bias. PWM Filter out the switching harmonics and above to get U PWM_LPF , determine whether it is currently in the lower half cycle of the fundamental component of the measured current. If so, increase the RC constant of the monostable circuit 2, thereby increasing Δt2.

[0065] Figure 4 The circuit diagram of the sampling-filtering-holding circuit of the embodiment of the present invention is shown in FIG. 1 . When the sampling signal is enabled, the analog switches 1 and 2 are turned on to filter the original integral signal U out_org Filter and get the DC component U DC Finally, the subtraction circuit is used to offset the bias. When the sampling signal is locked, analog switches 1 and 2 are closed, and the DC component U DC Keep the capacitor C keep superior.

[0066] Figure 5 This is a comparison diagram of the lower bridge arm SiC-MOSFET drain current waveforms in the BUCK converter measured by the Rogowski coil current sensor of the embodiment of the present invention and the commercial Rogowski coil current sensor TRCP0300. It can be seen that the peak value of the measured current is about 20A, and the commercial Rogowski coil current sensor has obvious droop distortion, resulting in inaccurate measurement of the DC component, thereby generating a DC bias of about 4.5A, while the Rogowski coil current sensor of the embodiment of the present invention has almost no droop distortion and has better low-frequency characteristics.

Claims

1. A SiC-MOSFET high-frequency switch current detection circuit based on a Rogowski coil, comprising a Rogowski coil differentiator equivalent circuit, wherein the Rogowski coil differentiator equivalent circuit is connected to an in-phase integration circuit; characterized in that: The output end of the in-phase integration circuit is connected to the filter holding circuit; the filter holding circuit includes a first analog switch, the first analog switch is connected to the second analog switch through a first low-pass filter circuit, and the second analog switch is connected to the subtraction circuit through a follower; the subtraction circuit is connected to a dual comparator; wherein the input end of the first analog switch, the negative input end of the subtraction circuit, and the positive input end of the follower input the original integrated signal output by the in-phase integration circuit; the positive input end of the follower also inputs a sampling signal; the positive input end of the dual comparator inputs a signal obtained after eliminating the DC bias of the original integrated signal; the positive input end of the follower is connected to the positive end of the holding capacitor; the negative end of the holding capacitor is grounded; When U PWM =0 and U last =1 and when, the sampling signal is enabled; wherein, U PWM is the PWM drive signal of SiC-MOSFET. PWM At the falling edge of , the first monostable circuit is triggered, and the second monostable circuit is triggered after a delay of Δt1. At this time, the delay signal U last =1, after delay Δt2, U last =0; One end of the delay capacitor is connected in series with the drain of the field effect tube, and the source of the field effect tube is connected to the negative end of the capacitor of the second monostable circuit; the gate of the field effect tube is connected to the output end of the comparator; the positive input end of the comparator is input with 0.5U PWM_H , U PWM_H is the voltage when the PWM drive signal of SiC-MOSFET is at a high level; the negative input terminal of the comparator is connected to the output terminal of the second low-pass filter; the input of the second low-pass filter is U PWM ; The negative input terminal of the dual comparator inputs the threshold value U thr ; Among them, I thr is the protection threshold of the measured current; M is the mutual inductance of the Rogowski coil; R1 and C1 are the input resistance and capacitance of the in-phase integration circuit respectively.

2. The SiC-MOSFET high-frequency switching current detection circuit based on the Rogowski coil according to claim 1, characterized in that: when When , the field effect tube is turned on and the time Δt2 is extended; otherwise, the field effect tube is turned off.

3. The SiC-MOSFET high-frequency switching current detection circuit based on the Rogowski coil according to claim 1, characterized in that: in, l1 is the inner diameter of the Rogowski coil, c is the turn spacing, and l2 is the outer diameter of the Rogowski coil.

4. The SiC-MOSFET high-frequency switching current detection circuit based on the Rogowski coil according to claim 1, characterized in that: The calculation formula of the original integrated signal output by the in-phase integration circuit is: Among them U out_org is the original integrated signal output by the in-phase integration circuit, U in is the output voltage of the Rogowski coil differentiator, I is the measured current, R1 and C1 are the resistance and capacitance of the common-phase input terminal of the common-phase integration circuit, R2 is the resistance from the common-phase input terminal to the ground, R3 and C2 are the feedback resistance and capacitance from the inverting input terminal to the output of the common-phase integration circuit, R D is the attenuation resistance in the equivalent circuit of the Rogowski coil differentiator, and s is the independent variable in the complex frequency domain.

5. The SiC-MOSFET high-frequency switching current detection circuit based on the Rogowski coil according to claim 4, characterized in that: Among them, f osc is the switching oscillation frequency of the MOSFET, f sw is the switching frequency.

6. The SiC-MOSFET high-frequency switch current detection circuit based on the Rogowski coil according to claim 1, characterized in that: The calculation formula of the original integrated signal output by the in-phase integration circuit is: Among them, I is the current to be measured; M is the mutual inductance of the Rogowski coil; R1 and C1 are the input resistance and capacitance of the in-phase integration circuit respectively.

7. The SiC-MOSFET high-frequency switch current detection circuit based on the Rogowski coil according to claim 1, characterized in that: The Rogowski coil differentiator comprises four layers of PCB boards; the upper surface of the top PCB board and the lower surface of the bottom PCB board are both covered with an outer shielding layer having the same size as the PCB board; through holes are provided on the four layers of PCB boards; the top PCB board and the bottom PCB board are connected by a plurality of winding turns in series, and The multiple series-connected winding turns pass through the through holes of the corresponding layers of PCB boards; the return turns on the middle two layers of PCB boards are connected in parallel, and the two return turns are correspondingly wound on the middle two layers of PCB boards through the through holes on the middle two layers of PCB boards; the head end of the winding turn is connected to the end of the two return turns, and the end of the winding turn is connected to the head end of the two return turns.

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