Patent ID: 9118291
Filing Date: 2015-08-25
Classification: H03F,H03G

Abstract:
1. A voltage supply circuit, comprising: a voltage amplifier, having a power terminal, wherein the voltage amplifier receives an operation power and outputs a gain voltage to drive an output device through the power terminal; and a power selecting circuit, receiving a plurality of supply voltages, wherein the power selecting circuit selects one of the supply voltages according to a volume level of an audio signal and supplies the selected supply voltage to the power terminal of the voltage amplifier as the operation power, wherein the power selecting circuit comprises: a volume detecting circuit, wherein the volume detecting circuit outputs a control signal according to the volume level of the audio signal; and an analog multiplexer, coupled to the supply voltages and the volume detecting circuit, wherein the analog multiplexer receives the control signal from the volume detecting circuit and supplies one of the supply voltages to the voltage amplifier according to the control signal.