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This paper describes a power supply designed for charging a 6.66 /spl mu/F capacitor to 30 kV in approximately 40 ms. The power supply should be capable of recharging the capacitor several times within a time frame of a few minutes. The primary supply would be a 500 VDC source, which could ultimately be supplied by a thermal battery. The major components of the power supply are a high-power inverter in H-bridge configuration followed by a step-up transformer. The switches for the H-bridge are high power isolated gate bipolar transistors (IGBTs). Control of the circuit is achieved by controlling the IGBTs by pulse width modulation (PWM). A microcontroller is being used to generate the required PWM signals. Use of the microcontroller provides a wide range of control flexibility and will allow for adaptation to the characteristics of the primary DC source. In order to minimize the volume of the transformer and at the same time limit the switching losses in the IGBTs, a switching frequency of 10 kHz was chosen. Circuit simulations show that 30 kV is reached after about 38 ms.