Providing back-up for 5V to 12V dc devices, up to 12W (1A), such as CCTV cameras or single door locks when powered from a 12V dc supply. It additionally provides over voltage, overload/short circuit and lightning/surge protection to the load device. The device has auto-sensing of input voltage in the range of 5V, 7.5V, 9V and 12V and provides a matching battery backed output.