A switching power supply which detects a power failure within a short period and maintains the DC output voltage (V.sub.O) for a long time. The switching power supply comprises a first voltage control means which controls a switching means (2) by means of a pulse width modulation means (9) which responds to a first voltage comparator means (8) which compares the DC output voltage (V.sub.O) and a reference voltage (V.sub.R); a second voltage control means having a pulse width modulation means working voltage range expansion means (12) which responds to a second voltage comparator means (11) which compares the DC output voltage (V.sub.O) and a second reference voltage (V.sub.RR); wherein further provision is made of a second switching means (16) for connecting a precharged second capacitor (15) in parallel to the first capacitor (1), in response to the second signal successively outputted by the second voltage comparator means (11) in a short period.
Holdover circuitry for an off line switcher, including a DC-to-DC converter, maximizes holdover time, during source voltage failures, by commutating a precharged holdover capacitor to the input of a power factor correcting preregulator. This limits the size of the holdover capacitor required without any loss in holdover time. Reduction in the size of the required holdover capacitor required for a desired holdover time improves volumetric efficiency of the off line switcher. This arrangement further improves efficiency of the DC-to-DC converter and decreases stress on its components by narrowing the input voltage range requirement.
An apparatus, method and article of manufacture are disclosed which provides for auxiliary battery conservation in adapters requiring auxiliary batteries. A power controller selects from one of two or more power sources to provide variable power components with DC power. For instance, power consumption of the transmitter (more specifically the transmit power amplifier) varies with the desired transmit power level. The transmitter can be supplied with DC power from the host device or the auxiliary source or both. The power controller can select the source of DC power (i.e., the host device or the auxiliary battery) or may combine the two power sources to provide necessary power to the transmit power amplifier.
