DC-DC converter for gate power supplies with an optimal air transformer

Voltages in medium voltage (MV) systems as for example in MV drives, wind generation and smart grids are in the range of several kV. Hence, switches of medium power systems need gate drive power supplies which consider a galvanic isolation for safety reasons. In this paper a gate supply with a capacitive compensated air transformer for medium voltage systems is presented. This approach not only has the advantage of being capable in isolating almost arbitrarily high voltages but also is a compact, lightweight and cheap solution. The air transformer windings are realized as tracks on a circuit board (PCB). Furthermore, the air transformer has been optimized with respect to efficiency of the gate supply, which results in an optimal value of 85%. The optimization is accomplished by field simulation of the transformer and a circuit calculation to obtain the total losses. The simulation and optimization results are confirmed by a laboratory setup which is designed for an output voltage of 25 V at 100 W.