Combined charging & supply circuit

摘要

A combined charging circuit for a rechargeable battery and supply circuit has a battery 22 for supplying power to an output supply VOUT and an adaptor (not shown) to provide from a mains supply power at a voltage VADAPT greater than the fully charged voltage of the battery VBAT, both to supply power to the output in place of the battery and to charge the battery. A buck convertor 32 acts as switching charger for the battery and comprises a rectifier 34 across the battery, and an inductor 36 and an electronic switch 39, e.g. a FET, in series with one 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. Heat dissipation is therefore low. The output supply VOUT may be fed to buck and boost converters for supplying the required 5 and 12v DC outputs for a portable personal computer.