Research and application of SiC _ MOSFETs in DC-DC circuit of new energy electric vehicle

In recent years, with the continuous optimization and improvement of power devices, various types of devices such as SiC _ MOSFETs, IGBTs, and Si _ MOSFETs have emerged in the market. Although the datasheets for these devices provide detailed descriptions of their device structures and electrical characteristics, there is a relative scarcity of specific application scenarios and corresponding simulation experimental data. This paper aims to comprehensively review recent research on the device structures and electrical characteristics of SiC _ MOSFETs, IGBTs, and Si _ MOSFETs. Additionally, we intend to conduct a systematic classification and comparative analysis to evaluate their performance in practical circuit applications. Furthermore, we have utilized MATLAB and Simulink to construct a representative simulation model of a DC-DC Buck-Boost circuit for new energy electric vehicles. Common SiC _ MOSFETs, IGBTs, and Si _ MOSFETs available in the market have been selected, and their parameters have been configured to match those in the simulation circuit. This approach enables us to explore the performance of these components in real-world circuit applications. Subsequently, the performance of these simulated circuits has been rigorously examined in practical scenarios. This comprehensive analysis provides a deeper understanding of the advantages of SiC _ MOSFETs compared to the other two devices and their potential contribution to the future development of electric vehicle technology. We anticipate that this research will drive advancements in electric vehicle technology and contribute to the realization of sustainable mobility.


Introduction
In recent years, the global emphasis on environmental concerns and sustainable energy has become a focal point on national agendas worldwide, propelling the rapid growth of the New Energy Electric Vehicle (NEEV) sector.NEEVs are recognized as integral components of sustainable mobility, offering the potential to reduce emissions, environmental impact, and energy consumption compared to traditional fuel-powered vehicles.Despite substantial progress in the new energy-electric vehicle domain, persistent technical challenges and opportunities for improvement demand attention.
The crucial role of DC-DC circuits within the electrical systems of new energy electric vehicles cannot be overstated.These circuits are responsible for rectifying incoming 220 V alternating current and converting it into the specific DC voltage required by other components in the vehicle system.Within these DC-DC circuits, power devices play a critical and indispensable role in determining the stability and efficiency of the circuit.Hence, they are crucial and irreplaceable in the functionality of DC-DC circuits.
In recent years, researchers have made significant advancements in the study and optimization of silicon carbide metal-oxide-semiconductor field-effect transistors (SiC _ MOSFETs).They have Figure 1 shows the Si _ MOSFET IGBT and SiC _ MOSFET transistor structures, which are based on the findings in [1][2][3][4][5].Contrasting colours have been used to better distinguish these three power devices and the models in the references have been optimised.From Figure 1, it can be found that in terms of crystal structure, the main differences between these three come from epi and sub, which are the epitaxial and substrate differences of the semiconductor devices.Epitaxial refers to the new semiconductor thin layer formed on the substrate, which is constructed from three components: p-type, quantum well, and n-type.The substrate is a wafer made of semi-conducting single-crystal material.epi and sub of Si _ MOSFET are Si n-epi and Si n + sub, respectively, while epi and sub of IGBT are Si n-epi and Si p + sub, respectively, and epi and sub of SiC _ MOSFET are Sic n-epi and Sic n + sub, respectively.It can be seen that their differences come from the types of materials and doping methods used for epi and sub, and the differences in transistor structures lead to the differences in their electrical characteristics.Currently, silicon (Si) power device technology is quite mature.In applications below 600 V, silicon metal oxide semiconductor field effect transistors (Si _ MOSFETs) dominate.In the market for high-voltage applications from 0.6 to 6.5 kV, the silicon super junction MOSFET (Si Super Junction _ MOSFET) has become the main choice.However, the further development of silicon devices is somewhat limited by the natural characteristics of the material.As a silicon-based insulated gate bipolar transistor (Si-based IGBT), it currently has a maximum voltage tolerance of 6.5 kV and can only be operated in an operating environment of less than 175°C.The Si-based IGBT can be used in a wide range of applications.In addition, it employs a bipolar conduction method, which further reduces its switching rate, thus affecting its popularity for high-power high-speed applications [3].However, in contrast, Silicon Carbide (SiC) material possesses a larger forbidden bandwidth, higher melting point, and stronger thermal conductivity, which enables it to operate stably at high temperatures.In addition, the critical breakdown field strength of SiC is about seven times that of silicon, giving SiC better voltage resistance.SiC also has a higher electron saturation mobility, which gives SiC MOSFET devices a higher operating frequency [6].Therefore, in conclusion, the electrical characteristics of Si _ MOSFET IGBT and SiC _ MOSFET are different in terms of voltage withstand performance, internal gate resistance, Vd-Id characteristics, and operating frequency.
The DC-DC buck-boost circuit model as shown in the figure below was built using MATLAB and Simulink and the circuit operating states at various stages of the circuit were plotted (below).Figure 2, top right: MOS tubes are in the on state, while MOS tubes are in the off state.At this point, the input and output are connected through the main inductor, resulting in a voltage difference between the two ends of the main inductor equal to the difference between the input and output voltages, i.e.V in -V out .Comparing the magnitude relationship between V out and V in , the main inductor current will appear in the following three different situations: (1) When V in -V out > 0, the main inductor current rises.( 2) When V in -V out = 0, the main inductor current remains constant.(3) When V in -V out < 0, the main inductor current falls.
Figure 2, lower left: MOS tube is S 2 and S 3 in the on state, while the MOS tube is S 1 and S 4 in the off state, at this time the voltage at both ends of the main inductor for the negative direction of the output voltage, that is, -V out , at this time, the main inductor current is a downward trend, the main inductor in the release of energy to the load side.
Figure 2, bottom right: MOS tubes S 2 and S 4 are on, while MOS tubes S 1 and S 3 off, at this point, the voltage across the main inductor is close to zero, and the main inductor current remains essentially unchanged, maintained near the designed -Io value.
In the MATLAB code section, the input parameters are set, including operating frequency, resistance, input voltage, output voltage, a duty cycle of MOS tube S 1 , the inductor current fluctuation interval, capacitor voltage fluctuation coefficient, and S 1 opens S 3 on position ratio.Then the following calculations are performed sequentially: (1) Calculate the MOS tube S 3 delay time ratio, which represents S 3 the ratio of delay time relative to the S 1 (2) Calculate D 2 , i.e., the duty cycle of S 2 , based on the input voltage, output voltage, and duty cycle of S 1 .
( Basic parameter calculation formula is as follows [7]: voltage ripple The Simulink simulation section incorporates fundamental modules such as the DC Voltage Source, Series RLC Branch, Scope, and various other basic components.These components are amalgamated to construct the three primary simulation module sections depicted in Figure 3, Figure 4 and Figure 5, ultimately forming a comprehensive simulation circuit.The common Si _ MOSFET IGBTs and SiC _ MOSFETs available in the market are selected as follows: IRF3205PbF, IRG4PH40UD, and C2M0160120D.According to their reference manuals i.e., (datasheets) as in [8][9][10], their on-resistance, operating frequency, parasitic gate-source capacitance, and parasitic gate-drain capacitance are as Table 1: Based on the typical on-resistance value, operating frequency, parasitic gate-source capacitance, and parasitic gate-drain capacitance values derived from the reference manual, controlling other variables such as the input voltage to remain unchanged, and resetting the corresponding parameters in the code and circuit sections, the resulting Vout specific waveforms are shown below which are Figure 6 to Figure 11:     After comparing the typical on-resistance value, operating frequency, parasitic gate-source capacitance, and parasitic gate-drain capacitance values of common Si _ MOSFET IGBTs and SiC _ MOSFETs of the models: IRF3205PbF, IRG4PH40UD, C2M0160120D, Vout overall figure, and Vout local sampling map.The typical on-resistance value of the C2M0160120D is found to be much smaller than that of the IRG4PH40UD, and close to that of the smallest IRF3205PbF.At the same time, the C2M0160120D has a much higher operating frequency than the IRF3205PbF and IRG4PH40UD, as well as a much smaller parasitic gate-source capacitance and parasitic gate-drain capacitance.According to the Vout overall figure and Vout local sampling map, it can be seen that the C2M0160120D Vout value rises from 0 V to 48 V and stabilises faster, with smaller ripple values (i.e., less fluctuation between peaks and valleys of the Vout image) and a denser Vout image.The C2M0160120D has smaller parasitic capacitance, which allows the voltage and current to change faster when switching between the on and off states, leading to a faster rise in Vout value and the Vout value to rise faster.The C2M0160120Ds have both higher switching speed and lower on-resistance, higher switching speed which means they can switch from the off state to the on state faster, which improves the response time of the circuit.With lower on-resistance, there is less voltage drop in the operating state, which helps to reduce the time for Vout to rise.In addition, lower on-resistance means that the on-state R ds voltage drop is smaller and produces less heat loss thus reducing the energy loss.Finally, the C2M0160120D has a higher switching frequency, which means more sampling points per cycle resulting in a denser image.
Taking the common four-switching tube Buck-Boost circuit in new energy electric vehicles as an example, the SiC _ MOSFET (C2M0160120D) shows obvious advantages in on-resistance, operating frequency, parasitic capacitance, etc., compared with the Si _ MOSFET (IRF3205PbF) and IGBT (IRG4PH40UD), and these characteristics help improve circuit performance and efficiency.It is very important to choose a power device that suits the needs of a specific application, and SiC _ MOSFETs may be an ideal choice for high-frequency and high-efficiency circuit design.It is believed that SiC _ MOSFETs will have a very broad prospect and application in the future when the DC-DC circuits of new energy electric vehicles are constantly being improved.
Through a comprehensive analysis of the performance characteristics of power devices such as SiC MOSFET, IGBT, and Si MOSFET in DC-DC Buck-Boost circuits used in New Energy Electric Vehicles (NEEV), valuable insights into their potential impact on future electric vehicle technology have been obtained.Our research indicates that taking C2M0160120D as an example, SiC MOSFET offers significant advantages over Si MOSFET and IGBT in terms of on-state resistance, operating frequency, and parasitic capacitance.These features contribute to faster response times, reduced energy losses, and improved overall circuit efficiency.SiC MOSFETs are particularly suitable for high-frequency and high-efficiency circuit designs.Choosing the right power devices is crucial for optimizing the performance of DC-DC circuits in new energy vehicles, and SiC MOSFETs present a promising option for such applications.As the demand for sustainable transportation continues to grow, this study provides valuable data for engineers and researchers to enhance electric vehicle technology.

Conclusion
However, it's important to acknowledge that this research has certain limitations, such as its focus on specific types of circuits and a limited set of power devices.It would be preferable to develop practical PCB test models in the future.Future research can explore a wider range of circuit configurations and power devices to provide a more comprehensive understanding of their performance in various applications.
In summary, SiC MOSFETs have the potential to shape the future of electric vehicle technology by improving circuit efficiency and overall performance.This research lays the foundation for further developments in the field and contributes to achieving sustainable transportation.

Figure 2 .
Figure 2. Diagram of four operating states of Buck-Boost.

Figure 2 ,
Figure2, top left: the MOS tube S 1 and S 4 are in the on state, while the MOS tube S 2 and S 3 are in the off state.At this stage, the input voltage is V in and the current flowing through the inductor is gradually rising, i.e., for energy storage for the main inductor.Figure2, top right: MOS tubes are in the on state, while MOS tubes are in the off state.At this point, the input and output are connected through the main inductor, resulting in a voltage difference between the two ends of the main inductor equal to the difference between the input and output voltages, i.e.V in -V out .Comparing the magnitude relationship between V out and V in , the main inductor current will appear in the following three different situations: (1) When V in -V out > 0, the main inductor current rises.(2) When V in -V out = 0, the main inductor current remains constant.(3) When V in -V out < 0, the main inductor current falls.Figure2, lower left: MOS tube is S 2 and S 3 in the on state, while the MOS tube is S 1 and S 4 in the off state, at this time the voltage at both ends of the main inductor for the negative direction of the output voltage, that is, -V out , at this time, the main inductor current is a downward trend, the main inductor in the release of energy to the load side.Figure2, bottom right: MOS tubes S 2 and S 4 are on, while MOS tubes S 1 and S 3 off, at this point, the voltage across the main inductor is close to zero, and the main inductor current remains essentially unchanged, maintained near the designed -Io value.In the MATLAB code section, the input parameters are set, including operating frequency, resistance, input voltage, output voltage, a duty cycle of MOS tube S 1 , the inductor current fluctuation interval, capacitor voltage fluctuation coefficient, and S 1 opens S 3 on position ratio.Then the following calculations are performed sequentially:(1) Calculate the MOS tube S 3 delay time ratio, which represents S 3 the ratio of delay time relative to the S 1(2) Calculate D 2 , i.e., the duty cycle of S 2 , based on the input voltage, output voltage, and duty cycle of S 1 .(3)Calculate the output current I o , based on the output voltage and resistance.(4) calculate the four time periods T 1 , T 2 , T 3, and T 4 , for subsequent calculations.(5) Introduce symbolic variables, including yb, yc, yd, and L, to represent the current and inductance values in the circuit.(6) Create a system of equations to describe the relationship between each current and inductance in the circuit.(7) Solve systems of equations to obtain specific values for yb, yc, yd, and L. (8) Convert symbolic variable values to double-precision floating-point numbers for subsequent calculations.(9) Calculate the value of Capacitance C. From the solved values and other parameters, derive the value of capacitance.Basic parameter calculation formula is as follows[7]: Figure2, top left: the MOS tube S 1 and S 4 are in the on state, while the MOS tube S 2 and S 3 are in the off state.At this stage, the input voltage is V in and the current flowing through the inductor is gradually rising, i.e., for energy storage for the main inductor.Figure2, top right: MOS tubes are in the on state, while MOS tubes are in the off state.At this point, the input and output are connected through the main inductor, resulting in a voltage difference between the two ends of the main inductor equal to the difference between the input and output voltages, i.e.V in -V out .Comparing the magnitude relationship between V out and V in , the main inductor current will appear in the following three different situations: (1) When V in -V out > 0, the main inductor current rises.(2) When V in -V out = 0, the main inductor current remains constant.(3) When V in -V out < 0, the main inductor current falls.Figure2, lower left: MOS tube is S 2 and S 3 in the on state, while the MOS tube is S 1 and S 4 in the off state, at this time the voltage at both ends of the main inductor for the negative direction of the output voltage, that is, -V out , at this time, the main inductor current is a downward trend, the main inductor in the release of energy to the load side.Figure2, bottom right: MOS tubes S 2 and S 4 are on, while MOS tubes S 1 and S 3 off, at this point, the voltage across the main inductor is close to zero, and the main inductor current remains essentially unchanged, maintained near the designed -Io value.In the MATLAB code section, the input parameters are set, including operating frequency, resistance, input voltage, output voltage, a duty cycle of MOS tube S 1 , the inductor current fluctuation interval, capacitor voltage fluctuation coefficient, and S 1 opens S 3 on position ratio.Then the following calculations are performed sequentially:(1) Calculate the MOS tube S 3 delay time ratio, which represents S 3 the ratio of delay time relative to the S 1(2) Calculate D 2 , i.e., the duty cycle of S 2 , based on the input voltage, output voltage, and duty cycle of S 1 .(3)Calculate the output current I o , based on the output voltage and resistance.(4) calculate the four time periods T 1 , T 2 , T 3, and T 4 , for subsequent calculations.(5) Introduce symbolic variables, including yb, yc, yd, and L, to represent the current and inductance values in the circuit.(6) Create a system of equations to describe the relationship between each current and inductance in the circuit.(7) Solve systems of equations to obtain specific values for yb, yc, yd, and L. (8) Convert symbolic variable values to double-precision floating-point numbers for subsequent calculations.(9) Calculate the value of Capacitance C. From the solved values and other parameters, derive the value of capacitance.Basic parameter calculation formula is as follows[7]:

Table 1 :
relevant parameters of MOSFETs.