Protect EV Electrical Subsystems with Microchip’s mSiC Technology

October 18, 2023

Sponsored Story

The trend toward higher bus voltages in Battery Electric Vehicle (BEV) and Hybrid EV (HEV) electrical subsystems has created the need for a more robust circuit-protection strategy. Traditional electromechanical solutions raised concerns about reliability and a slow response to overload conditions, prompting designers to consider the faster and more reliable solid-state circuit-breaker (SSCB), or electronic fuse (E-Fuse), approach.

Silicon Carbide (SiC) semiconductors provide an optimal circuit interruption device for E-Fuse solutions to enable quick over-current detection and protection of downstream wiring and sensitive high-voltage loads from high currents events.

One example is Microchip’s SiC-based E-Fuse Demonstrator Board, which is available in six variants for 400V–800V battery systems and current ratings from 10A up to 30A and uses Microchip’s mSiC™ MOSFETs. As much as 500 times faster than electromechanical approaches, the E-Fuse board leverages its high-voltage solid-state design to detect and interrupt fault currents in microseconds instead of in milliseconds. The fast response time substantially reduces peak short-circuit currents from tens of kilo-amps to hundreds of amps, which may prevent a fault event from becoming a hard failure.

Electromechanical vs. Solid-State Circuit Breaker

Unlike electromechanical circuit breakers, E-Fuse has no moving parts, and circuit interruption is not performed using a forced air gap, nor is there arcing or the risk of arc flash, or concerns with degradation of contacts, contact bounce or general mechanical wear. There also is a faster response time during a fault condition, which reduces the let-through current and energy delivered to downstream wiring and loads. Current is limited to safe, manageable levels. E-Fuse can also be programmed and reset on demand.

SiC technology is at the heart of these E-Fuse advancements. It leapfrogs the limitations of silicon technology in such areas as electric breakdown field, thermal conductivity, energy gap and reliability.  Each of these parameters is critical to the success of E-Fuse solutions.

Reliability is particularly important, an E-Fuse needs the SiC MOSFET to recover quickly from avalanche mode. This requires that the SiC MOSFET demonstrates strong immunity to single-event and repetitive unclamped inductive switching (UIS) stress. Microchip’s mSiC MOSFETs have undergone repetitive UIS tests of 100k pulses followed by a time-dependent dielectric breakdown (TDDB) test with no degradation in performance or gate-oxide integrity. Gate-oxide degradation has typically been the Achilles heel of a MOSFET, as devices are generally most stressed under the high electric field produced while in avalanche mode.

Being able to trust mSiC MOSFET reliability in avalanche mode enables E-Fuse solution developers to reduce or eliminate the snubber circuitry that would otherwise be required, and adopt SiC with ease, speed and confidence.  Other benefits of SiC technology’s improved performance, safety and reliability include reduction in the E-Fuse’s downstream wiring conductor sizes and insulation temperature ratings, and simplified designs because there is no manual intervention to reset the device; and there is no need to replace and service the E-Fuse after a fault event. The E-Fuse demonstrator showcases this resettable feature that enables designers to package an E-Fuse in the vehicle without the burden of design-for-serviceability constraints.

OEMs can accelerate development of SiC-based auxiliary applications with the E-Fuse demonstrator because of the built-in Local Interconnect Network (LIN) communication interface. The LIN interface enables configuration of over-current trip characteristics without having to modify hardware components and reports diagnostic status.

Solid-state circuit protection has become increasingly important for systems ranging from EVs and DC fast charging stations to datacenters, microgrids, energy storage systems and solar inverters. With today’s growing focus on system performance, safety and reliability, the use of a SiC-based circuit interruption device like Microchip’s E-Fuse offers an easy-to-implement mSiC solution that drives system-level optimization, minimizes downtime and increases reliability.