Abstract: A power supply device and system for providing power to a portable electronic device. A detachable device includes a rechargeable DC power source, a DC-to-AC inverter, and a primary transformer winding around a first core element. The portable electronic device includes multiple secondary transformer windings around a second core element. The detachable device cooperates with the portable electronic device so as to form a complete power supply circuit for providing AC and/or DC operating voltages to the portable electronic device.

Abstract: The battery charger including a power factor correcting and voltage regulating apparatus having an inductor through which current is modulated by a modulator to obtain an efficient regulation and an efficient power factor correction. According to a first embodiment, the modulator comprises two rectifying elements connected to two controllable high frequency bidirectional switch elements. According to a second embodiment, the modulator comprises a rectifying element connected to a controllable high frequency switch. According to a third embodiment, an efficient battery charger is provided. It comprises an inverter including four controllable high frequency bidirectional switch elements connected in a bridge configuration. According to a fourth embodiment, a two-part battery charger is provided. It has an indicator for indicating quality of the coupling between the two parts thereof. According to a fifth embodiment, a two-part battery charger is provided.