Silicon Carbide (SiC) Technology Replaces Old Silicon FETs and IGBTs

The high power, high voltage requirements of all types of electric vehicles (EVs), including electric buses and other e-transportation power systems, require higher silicon carbide (SiC) technology to replace older silicon FETs and IGBTs. Safely and efficiently driving these more efficient SiC devices can be achieved using digital rather than analog gate drivers, and many non-automotive or non-vehicle applications will benefit.

Electric vehicle forecasts accelerate

Improved battery technology, reduced battery manufacturing costs, and government targets to reduce CO2 emissions have accelerated the shift to fully electric vehicles. According to Yole Développement, the EV/Hybrid Electric Vehicle (HEV) market will exceed 2 million units by 41 million, with a compound annual growth rate (CAGR) of 2026%. This represents an accelerated transition from gas-guzzling internal combustion engine vehicles to cleaner electric vehicles.

Due to the growth of electric vehicles, Yole predicts that power silicon carbide (SiC) devices in EV/HEV power control and conversion are expected to grow at a CAGR of more than $1 billion in 2025 at a rate of 5%. SiC power devices and improved battery technology can be used in other vehicles such as electric trains, buses, off-road and other electric vehicles, as well as non-vehicle charging and other non-automotive applications that will benefit from the growth of automotive EVs.

Silicon Carbide Power Transformation

As a wide-bandgap material, SiC has strong physical bonds, provides high mechanical, chemical and thermal stability, and can be used at higher junction temperatures than silicon.

One of the design trade-offs is the turn-off time of SiC MOSFET, which is very short. The high di/dt causes severe voltage spikes when the turn-off rate is high. Other challenges include noise, short circuit, overvoltage, and overheating. Although this complicates the design of the gate driver, a well-designed gate driver can further reduce losses and simplify SiC implementation and design-in.

Driving SiC Gates

Traditional analog gate drivers are slow for SiC’s response time requirements and are difficult to modify to get the desired operation and performance. In contrast, digital gate drivers or gate driver cores can address these issues and solve noise, short circuits, overvoltage, overtemperature and other design issues. Microchip’s AgileSwitch® 2ASC-12A2HP is a production-qualified 1200V digital gate driver that allows designers to safely and reliably drive SiC MOSFETs. The driver’s software-configurable Enhanced Switching™ technology provides multiple levels of control and protection to ensure safe and reliable operation.

The gate driver has two independent operating modes that provide efficient normal operation and safe shutdown in the event of a fault, and each mode is configurable. Normal operation can be optimized for best voltage overshoot and switching loss performance. When triggered, fault operation quickly and safely shuts down the device. While sacrificing some switching losses, this process protects the device from catastrophic failure.

Make vs. Buy: An Easy Transition

While many designers feel confident designing silicon IGBT drivers, silicon carbide drivers present issues. For new SiC designs, especially those migrating from IGBT-based converters, the learning curve is sharp, expensive, and long. The Digital Gate Driver Board has design tools available to minimize the learning curve and provide a production-ready solution.

With the Intelligent Configurable Tool (ICT), designers can change control parameters of digital gate drivers without picking up a soldering iron. Debugging system-level issues can be difficult. Using PICT 4 or MPLAB, performance features in the driver can be reconfigured in the application, simplifying design and speeding up development time.

Most analog gate drivers cannot pinpoint the location of a fault. With ICT, new digital gate drivers can. The software tool allows the user to turn faults on or off at various checkpoints to focus on the problem.

More development tools

The gate driver core is compatible with a wide range of Microchip SiC modules using a reference module adapter board and also features an Enhanced Switch Acceleration Development Kit (ASDAK) which includes the gate driver, module adapter board, programming kit and ICT software for SiC MOSFET modules.

Qualified solutions

The production-qualified gate drivers meet stringent transportation industry requirements, including mean time between failures (MTBF), shock and vibration, and temperature cycling.

Towards cleaner, safer, more efficient driving

For e-transportation applications that require high power (20 kW or more) and voltages up to 1.2 kV, SiC devices with digital gate drivers offer efficiency advantages. This means that electric vehicle propulsion, conversion and charging applications in a variety of applications, including buses, trucks, carts, heavy vehicles, trains and their infrastructure, can benefit from this new design approach.