Patent ID: 7830209

Claim:
An audio amplifier circuit for providing an output signal to an audio transducer, the audio amplifier circuit comprising: a power amplifier having an audio input for receiving an audio input signal, an audio output for providing the output signal, and a pair of power supply rail connections; a charge pump power supply for providing a power supply voltage across the pair of power supply rail connections of the power amplifier and including at least one switching device, wherein the charge pump power supply has a selectable operating mode selectable between a high efficiency operating mode and a high power operating mode, wherein power consumed in charging and discharging a gate of the at least one switching device is lower in the high efficiency operating mode than in the higher power mode; and a control circuit for selecting the operating mode of the charge pump power supply in conformity with an indication of an amplitude of the audio output signal, such that the charge pump power supply operates in a high efficiency operating mode for lower amplitude audio output signals and a high power operating mode for higher amplitude audio output signals.