Abstract: An electrical power supply circuit for converting alternating circuit power into a direct current output comprises a transformer and rectifier, a filter capacitor across the output terminals and a phase control switching device and a non-saturating inductor in the primary circuit. The circuit arrangement reduces the volt-time integral of the transformer and allows its core to be made of a smaller size, in comparison to the transformer cores of previously known power supplies, without danger of saturation. Other advantages such as low RFI, reduced transformer wire size and overload current protection are obtained. A commutator circuit may also be provided for turning off the phase control switching device before the end of the associated half cycle of input voltage to further reduce the transformer volt-time integral and to accordingly allow a further reduction in its core size.