Silicon carbide controlled current limiter, current limitation strategies, foreseen applications and benefits

The expansion of electricity networks (distribution of energy, telecommunication), strongly contributed to increase the risks of appearance of defects, such as surge or overload. This multiplicity and complexity of electric networks, the need to have reliable systems favoured the development of serial protection devices. Fuse solution allows an efficient and total protection but requires to replace an element in case of failure. Therefore, other solutions have been investigated. Complex systems have been developed, all based on serial compensation, such as supra-conductor material, GTO MOV combination... Indeed, because of the strong energy appearance during a short circuit, it is necessary to limit and to dissipate the energy of the short circuit, under high bias. This constraint leads to a feasibility study of a current limiter in 4H silicon carbide (4H-SiC). A VJFET structure was retained focusing on a nominal current of I(N) = 1 A and a nominal voltage of V(N) = 690 V. The device was optimised, taking into account SiC excellent physical properties. The VJFET was designed checking the trade-off between a low on-resistance value, high voltage capability and the. highest gate transconductance value. A first batch of component was made, validating the bidirectional limitation function in both current and voltage mode, (V(MAX) = 970 V). The efficiency of the protection was validated, demonstrating the capacity of a component to react very quickly (t < 1 mu s). Using such a device is very suitable in several applications (protection against short circuit, transient over current...) as it will allow to reduce transient phenomena and thus increase the efficiency and lifetime of the whole system.