An apparatus is provided to enable power supply input to be isolated from power supply output. Power is received from a first power signal at a first of a plurality of charge stores. A second power signal is output from a second of the plurality of charge stores. The second power signal is isolated from the first power supply. The first charge store can be charged from the power input whilst isolated from the power output. The second charge store can be discharged to the power output, while isolated from the power input.