High-voltage eMobility applications are on the rise. Traditionally, fuses are non-re-settable, and sometimes mechanical relays or contactors are used. However, that is now changing. Semiconductor-based re-settable fuses or eFuses are now replacing traditional fuses.
These innovative eFuses represent a significant trend in safeguarding hardware and users in high-voltage and high-power scenarios. Vishay has announced a reference design for an eFuse that can handle high power loads. They have equipped the new eFuse with SIC MOSFETs and a VOA300 optocoupler. The combination can handle up to 40 kW of continuous power load. The design is capable of operating at full power with minimal losses of lower than 30 W without active cooling. The eFuse incorporates important essential features like continuous current monitoring, a preload function, and rapid overcurrent protection.
Vishay has designed the eFuse to manage the safe connection and disconnection of a high-voltage power source. For instance, the eFuse can safely connect or disconnect various vehicle loads safely to and from a high-energy battery pack. The eFuse uses SIC MOSFETS as its primary switches, and these are capable of continuous operation up to 100 Amperes. The user can predefine a current limit. When the current exceeds this limit, the eFuse disconnects the load rapidly from the power source, safeguarding the user and the power source or battery pack. In addition, the presence of a short circuit or an excessive load capacitance during power-up causes the eFuse to initiate an immediate shutdown.
The basic design of the eFuse is in the form of a four-layer, double-sided PCB or printed circuit board of 150 mm x 90 mm. Each layer has thick copper of 70 µm thickness, as against 35 µm for regular PCBs. The board has some connectors extending beyond its edges. The top side of the PCB has all the high-voltage circuitry, control buttons, status LEDs, multiple test points, and connectors. The PCB’s bottom side has the low-voltage control circuitry. It is also possible to control the eFuse remotely via a web browser.
To ensure safety, the user must enable the low-voltage power supply in the first place. They can follow this up by enabling the high-voltage power supply on the input. For input voltages exceeding 50 V, an LED indicator lights up on the board. Vishay has added two sets of six SIC MOSFETS with three connected in parallel in a back-to-back configuration. This ensures the eFuse can handle current flow in both directions. A current-sensing shunt resistor, Vishay WSLP3921, monitors the current flowing to the load. Vishay has positioned the current sensing shunt resistor strategically between the two parallel sets of MOSFETs.
Vishay has incorporated convenient control options in the eFuse. Users can operate the control options via the push buttons on the PCB, or by using the external controller, Vishay MessWeb. Either way unlocks access to an expanded array of features. Alternately, the user can integrate the eFuse seamlessly into a CAN bus-based system. They can do this by using an additional chipset in conjunction with the MessWEB controller. Vishay claims to have successfully tested its reference eFuse design.
