High voltage switch for compact bidirectional dc-dc converter driving dielectric electroactive polymer actuators

Driving DEAs requires time-varying high voltage power supplies, up to 18kV for 200um polymer layers. HV amplifiers are commonly used but bulky and expensive. Designing embedded actuators requires compact and efficient powersupplies. Furthermore, only a little part of the electrical energy delivered to the DEA is converted to mechanical energy. The major part is stored in the capacitance of the actuator and needs to be recollected to maximise the system's efficiency. Low cost integrated bidirectional DC-DC converters (ex. Flyback) have been proven reliable to drive DEAs at voltages up to 2,5kV. To design a reversible converter with an output voltage up to 18kV, a high voltage switch is needed. Yet, the maximum breakdown voltage for a MOSFET with current ratings inferior to 200mA is 4,5kV. Our simulation and experimental work demonstrate a reliable driving circuit for triggering two series connected MOSFETs. A wide voltage switching range is achieved (0 to 8kV) with a 200mA current rating. Using the Transformer Gate Driver topology, galvanic insulation and synchronisation of each gate driver is ensured. To gain an equal distribution of the bus voltage over the MOSFETs, mastering the parasitic capacitances is mandatory. A design method has been developed to compensate these parasites and ensure the reliability of the device. The architecture of the high voltage switch is N-scalable and a switching range from 0 to 18kV could be achieved when stacking five MOSFETs in series.