A portable device includes a battery, electronic circuitry, and a peak current provider that provides a peak current to the electronic circuitry. Power is supplied to the portable device by connecting a battery to a peak current provider, charging the peak current provider, and supplying a current from the battery to electronic circuitry of the portable device, when a current required by the electronic circuitry is less than or equal to a preset value, and disconnecting the battery from the peak current provider and supplying a current from the peak current provider to the electronic circuitry, when a current required by the electronic circuitry is greater than the preset value.