Abstract: A combined charging circuit for a rechargeable battery and supply circuit has a battery for supplying power to an output supply and an adaptor to provide from a mains supply power at a voltage greater than the fully charged voltage of the battery, both to supply power to the output in place of the battery and to charge the battery. A buck convertor acts as switching charger for the battery and comprises a rectifier across the battery, and an inductor and an electronic switch in series with on another and with the supply from the battery to the output supply, the switch acting as the switching element of the switching charger when the adaptor is powered from the mains and as a low ON resistance power switch when the battery is supplying power to the output supply.