SiC Fuse Brings Flexibility to Circuit Protection in EVs

The availability of SiC technology has already transformed the automotive industry by enabling the design of electric vehicles with faster charging and longer ranges. The material’s ability to switch high voltages very quickly brings better efficiency to power conversion, and with that, better thermal management in smaller packages. It is also a very robust material, both against physical and electrical stress, which makes it possible to be employed in applications other than power conversion.

One such use case is employing SiC devices as a solid-state fuse. As in other areas, such as relays, a solid-state fuse has the potential to react much quicker than a traditional mechanical fuse. It would also be more reliable over time as there is no degradation from mechanical shock, arcing or contact bounce.

Microchip has recently launched a family of SiC-based solid-state fuses that offer those benefits and more. Instead of the fuse triggering at a certain level, the new solid-state fuses can be programmable to trigger on events. The reaction time of the solid-state fuse is between 100 to 500 times faster than traditional fuses, ensuring that other components in the circuit are fully protected. The SiC fuse also offers another advantage - unlike a mechanical device, which either conducts current or not, the solid-state device is very flexible.

Clayton Pillion, vice president of Microchip’s silicon carbide business unit explains, “The silicon carbide E-Fuse gives designers much more freedom in circuit protection designs. It can act like an ordinary fuse and shut off the power to the circuit completely to protect the load, or the gate driver can be used to bring down the gate voltage and throttle the amount of current passing before shutting the circuit down or restoring it. The visual control we have over the gate drivers means it is possible to programme a unique fault profile for each application. Even more sophisticated control is possible using a Microchip microcontroller”.

The E-Fuse family is for DC applications only. There are currently six E-Fuse variants available for 400–800V battery systems with current ratings up to 30 amps. To support development of applications using E-Fuses, the company has also launched an E-Fuse Demonstrator Board, which can detect and interrupt fault currents in microseconds, substantially reducing peak short-circuit currents from tens of kilo-amps to hundreds of amps. This speed makes it possible to prevent a fault event from resulting in a hard failure.

The remote reset feature eliminates design-for-serviceability constraints, as remote resetting is automatically controlled by the system. This also reduces design complexities and enables flexible vehicle packaging to improve BEV/HEV power system distribution. The built in LIN interface enables the configuration of the over-current trip characteristics without the need to modify hardware components. Diagnostic status can also be reported through the LIN bus. The Core Independent Peripherals feature found in Microchip’s PIC microcontrollers allows the fuse to be controlled without the microcontroller being fully powered, providing further energy savings. Companion components on the demonstrator board are automotive-qualified and feature a lower part count and higher reliability over a discrete design. The E-Fuse Demonstrator Board is supported by MPLAB X IDE to enable the rapid development or debugging of software.