Gejian Semi SiC MOSFETs

Gejian SiC MOSFETs offer several key advantages over silicon IGBTs: First, significantly lower switching losses due to the absence of tail current during turn-off, enabling operation at much higher switching frequencies (100kHz+ vs 20kHz for IGBTs). Second, lower conduction losses at light loads due to the resistive output characteristic compared to the fixed voltage drop of IGBTs. Third, better thermal performance with higher thermal conductivity of SiC material, allowing higher operating temperatures (200°C vs 175°C for IGBTs). Fourth, smaller device size for equivalent current ratings, enabling more compact power converter designs. Fifth, higher breakdown voltage capability, with Gejian offering devices up to 1700V. These advantages make SiC MOSFETs ideal for applications where efficiency, size, and weight are critical.

Choose SiC MOSFETs for high-frequency (>50kHz) or high-efficiency applications. Use IGBTs for cost-sensitive, lower frequency applications.

Gejian SiC MOSFETs require different gate drive voltages compared to silicon IGBTs. The recommended turn-on gate voltage is +15V to +20V, with +18V being optimal for most devices. This higher voltage ensures the device is fully enhanced, minimizing RDS(on). For turn-off, a negative voltage of -3V to -5V is strongly recommended. Unlike IGBTs, SiC MOSFETs have lower threshold voltages (typically 2.5-3.5V), making them more susceptible to false turn-on from Miller capacitance coupling during high dv/dt switching. The negative gate voltage provides noise immunity and prevents unintended conduction. The gate driver must provide fast switching with high peak current capability (2-5A) due to the high dv/dt requirements of SiC devices.

Use +18V turn-on and -3V to -5V turn-off gate drive for SiC MOSFETs. Ensure gate driver has sufficient peak current capability. Contact our FAE team for gate drive design.

Gejian offers SiC MOSFETs in multiple voltage ratings to address different application requirements. The 650V rating is designed for 400V DC bus applications such as EV onboard chargers, DC-DC converters, and industrial power supplies. The 1200V rating is the most versatile, suitable for 800V DC bus EV traction inverters, solar inverters, and industrial drives. The 1700V rating addresses high-voltage applications such as traction systems, medium-voltage drives, and grid-tied inverters. Each voltage rating is optimized for its target applications with appropriate trade-offs between specific on-resistance, switching performance, and cost. The higher voltage ratings enable direct replacement of high-voltage IGBTs with the benefits of SiC technology.

Select voltage rating based on DC bus voltage with appropriate safety margin (typically 70-80% derating). Contact our FAE team for voltage rating recommendations.

The high switching speed of Gejian SiC MOSFETs (dv/dt can exceed 50V/ns) requires careful attention to circuit layout and design. Key considerations include: Minimize stray inductance in the power loop by using short, wide traces and laminated bus structures. Use Kelvin source connection for gate drive to avoid source inductance effects. Implement proper gate resistor selection to control switching speed - typical values are 5-20Ω depending on desired dv/dt. Use isolated gate drivers with high CMTI (Common Mode Transient Immunity) of at least 100kV/μs. Pay attention to PCB layout to minimize coupling between high dv/dt nodes and sensitive circuits. Use proper shielding and grounding techniques to manage EMI. The fast switching can cause voltage overshoots, so snubber circuits or RC dampers may be necessary depending on layout quality.

Minimize stray inductance and use Kelvin source connection. Select gate resistors to control dv/dt. Contact our FAE team for high-speed layout guidelines.

Gejian SiC MOSFETs provide the greatest benefits in applications where high switching frequency, high efficiency, or compact size are critical. Key applications include: EV traction inverters where SiC enables higher efficiency and smaller cooling systems. Onboard chargers and DC-DC converters in EVs where high-frequency operation reduces passive component size. Solar inverters where SiC improves efficiency and power density. High-frequency power supplies (>100kHz) where SiC's low switching losses are essential. Wireless charging systems where high-frequency operation enables compact coil designs. Data center power supplies where efficiency directly impacts operating costs. Motor drives for applications requiring very high dynamic performance. In these applications, the higher cost of SiC devices is offset by savings in cooling systems, passive components, and operating energy costs.

Use SiC MOSFETs for high-frequency, high-efficiency, or size-constrained applications. Contact our FAE team for application-specific recommendations.