Power Electronics Europe April/May Issue 2022

www.analog.com SIC DRIVERS 23 www.power-mag.com Issue 2 2022 Power Electronics Europe meaning 800 A in 80 ns, type of di/dt can be observed. Indeed, all the intrinsic advantages of the SiC switch would be negated by common- mode noise perturbations, as well as extremely high and destructive voltage overshoot due to ultrafast voltage and current transients (dv/dt and di/dt) generated in a poorly managed power switches environment. Broadly speaking, the SiC switch has a relatively simple function despite the underlying technology—it’s only a 3-terminal device—but it must be carefully interfaced to the systems. Driving SiC devices efficiently The isolated gate driver bridges the signal technology has shown leading common- mode transient immunity (CMTI) with measured performances up to 200 V/ns and beyond. This unlocks the full potential of SiC switching time under safe operation. ADI has advanced digital isolation technology for over 20 years with iCoupler digital isolation ICs. The technology is comprised of a transformer with thick polyimide insulation (see Figure 5). Digital isolators use foundry CMOS processes. Transformers are differential and provide excellent common-mode transient immunity. High performance gate drivers have proven their value in real-world testing with leading SiC MOSFET power switch providers like Wolfspeed. Across key parameters, including short-circuit detection time and total fault clearance time, performance can be achieved down to 300 ns and 800 ns, respectively. For additional safety and protection, test results have demonstrated the adjustable soft shutdown capabilities essential for smooth system operations. Switching energy and electromagnetic compatibility (EMC) can likewise be maximized for improved power performance and EV range. Higher drive capability allows users to have faster edge rates and therefore reduces switching losses. This not only helps with efficiency but also enables board space and cost savings by eliminating the need for external buffers allocated per gate driver. Conversely, under certain conditions, the system may need to switch more slowly to achieve optimal efficiency, or even in stages, which studies have shown can increase efficiency further. An adjustable slew rate is provided to allow users to do this, and the removal of external buffers eliminates further obstacles. Elements in a system It’s important to note that the combined value and performance of the gate driver and SiC switch solution can be completely negated by compromises and/or inefficiencies in the surrounding components. A holistic view of the EV reveals additional opportunities for optimizing drive train power efficiencies, which are critical for exploiting the maximum usable battery capacity while ensuring safe and reliable operations. The quality of the BMS directly impacts the miles per charge an EV can deliver, maximizes the battery’s overall Figure 3: Voltage and current waveforms at turn-on (left) and turn-off (right) Figure 4: The isolated gate driver bridges the signal world (control unit) and the power world (SiC switch) world (control unit) and the power world (SiC switch), se Figure 4. Other than isolation and signal buffering, the driver performs telemetry, protection, and diagnostic functions, making it the key element of the signal chain. The isolated gate driver will take care of setting the best switching sweet spot, ensuring short and accurate propagation delay through the isolation barrier, while providing system and safety isolation, controlling power switch overheating, detecting and protecting against short circuits, and facilitating the insertion of the sub-block drive/switch function in an ASIL D system. The high slew rate transients introduced by the SiC switch can corrupt data transmission across the isolation barrier, however, so measuring and understanding the susceptibility to these transients is critical. iCoupler® ADI proprietary Figure 5: ADI has pioneered advances in digital isolation technology for over 20 years with iCoupler digital isolation ICs