As more xEVs strive to extend their cruising range and reduce on-board battery size, demand for SiC power devices has skyrocketed. Increased main drive inverter efficiencies must account for higher battery voltages while charging times shrink requiring improved SiC devices with reduced ON resistance resistances.
Low ON Resistance
SiC power MOSFETs can be designed with much higher withstand voltage capabilities (up to 900V). As such, they can achieve high efficiencies at lower switching losses resulting in more power delivered to loads while maintaining an impressive short circuit voltage and compact form factor.
Silicon carbide’s higher electric field strength compared to silicon enables this advancement, as well as its thinner drift layer enabling smaller normalized ON resistance per unit area than in conventional planar silicon MOSFETs, providing more efficient switching performance, leading to greater passive component miniaturization and increased device efficiency.
ROHM was the pioneer to mass produce SiC MOSFETs featuring a trench design, and their industry-leading 3rd generation devices reduced ON resistance by 40% and enhanced short circuit withstand time without compromising reliability. Their 4th generation trench MOSFETs also boast 50% lower ON resistance compared to previous generations as well as supporting flexible gate drive voltage Vgs between 15V-18V for further device power savings.
ROHM’s 1200V/4200A SiC Power MOSFETs are essential components in developing next-generation electric vehicles that must be lighter, faster and more environmentally-friendly. In fact, current EVs already employ these devices within their battery systems for improved driving and quicker charging times as well as for motor control on traction inverters/on-board chargers to maximize performance and decrease energy loss.
High-Speed Switching Performance
SiC MOSFETs can reduce power conversion losses significantly by minimizing their on resistance and parasitic capacitance, though this requires striking a balance between lower on resistance and shorter short-circuit withstand time (HBM). ROHM was able to achieve 40% lower ON resistance per unit area than conventional products without compromising HBM by further optimizing its original double trench structure. With its 4-pin package that separates driver source pin from power supply pin, this 4th Generation SiC MOSFET achieves lower switching loss by 50 percent while maintaining high HBM breakdown voltages. As a result, higher switching speeds than planar-type SiC MOSFETs can be reached.
With growing interest in electric vehicles (EVs), there has been an increased need for smaller and lighter electrical systems that improve energy consumption while increasing efficiency to extend driving range. A particular focus has been placed on decreasing the size of main drive inverters to increase conversion efficiency while simultaneously decreasing vehicle weight.
ROHM created its cutting-edge 4th Generation SiC MOSFET to drive technical innovation in next-generation electric vehicles (EVs). It features a double trench structure with wide voltage range to meet various automotive applications such as power supplies and traction inverters. Bare chip samples are now available, with discrete packages being made available by June 2020; 1200V/180A modules will become available later.
Minimal Parasitic Capacitance
Parasitic capacitance in electronic circuits limits current flow, leading to signal degradation. It impacts many aspects of performance including slew rate, current output capability, power dissipation and feedback loop stability – as well as being caused by factors like circuit layout, component selection and PCB design. While it can be caused by several sources such as PCB design or component choice; its presence can also be minimized through factors like short driving loop lengths or devices with short or no wire bonding connections; finally it is also essential that critical nets be carefully routed when possible.
Parasitic capacitance occurs between any two conductors or elements, such as two traces, pads and pins or PCB ground and copper lines. Its effects vary with frequency; at lower frequencies it has minimal effects while at higher frequencies it may impede current flow significantly.
ROHM’s latest 650V 4th Gen SiC MOSFETs can achieve lower resistance without compromising short-circuit withstand time through their innovative design, which uses one dummy/source trench per gate trench, which doubles cell density and further decreases parasitic capacitance. Together with other enhancements, these MOSFETs deliver best-in-class performance at 850V with greater power density and faster switching speed; PGC Consultancy and TechInsights conducted extensive evaluations on these devices to verify their claims; PGC Consultancy provided detailed electrical data analysis while cross-sectional images were provided from PGC Consultancy/TechInsights evaluation of these devices to prove these devices’ claims; both companies provided detailed electrical data and cross-section images for verification.
Low Switching Loss
Rohm SiC MOSFETs boast much lower switching losses compared to conventional Si power devices due to no tail current during operation and compact chip size allowing lower gate charge/capacitance levels. As a result, power loss during switching is substantially decreased, increasing efficiency during power conversion processes while simultaneously eliminating wasteful energy consumption in various equipment.
ROHM has invented a double-trench structure to reduce electric field concentration in its gate section and further decrease ON resistance without compromising short circuit withstand time. This is accomplished using wider gate trenches on both sides of a MOSFET as well as by extending the protective p-n junction deep into its drift region to protect its gate oxide from potential short circuiting events.
As the next generation of electric vehicles (EVs) evolves, their electrical power systems must become ever more efficient and smaller in order to increase cruising range and improve fuel economy. To do this, advanced silicon carbide power devices that can meet higher voltage and current applications will be needed.
ROHM has come out with a groundbreaking series of 1200V 4th Gen SiC MOSFETs specifically tailored for automotive powertrain components like main drive inverters. By reducing on-resistance and increasing saturation current, these MOSFETs allow smaller and lighter systems with enhanced performance.
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