Abstract: The invention provides a power conversion device operable in a discontinuous conduction mode under the control of a switch. During operation in the discontinuous conduction mode, an oscillating voltage exists across the switch means prior to a turn-on of the switch means. The power conversion the device comprises a switching controller arranged to ensure that turn-on of the switch occurs at a minimum of the oscillating voltage. The power conversion device also comprises a timer arranged to provide a controlled time period following a first turn-on of the switching means, during which a second turn-on of the switching means can not occur. Such an arrangement is advantageous in that a low power level of operation of the device and a short conduction time of the switch means does not lead to an undesirable increase in switching frequency. Consequently, a reduction in a parasitic capacitance of the switch will be rewarded by an increase in efficiency.