| 摘要 |
<P>PROBLEM TO BE SOLVED: To suitably control a power-supply voltage to an amplifier. <P>SOLUTION: A main amplifier 4 amplifies an audio signal S1. A power-supply circuit 2 supplies a positive power-supply voltage CPVDD to an upper-side power-supply line of the amplifier and supplies a negative power-supply voltage CPVSS to a lower-side power-supply line. A voltage detection section 32 generates a voltage detection signal S21 that is asserted when the amplitude of an audio signal S2 amplified by the amplifier is larger than a predetermined threshold value. A current detection section 34 generates a current detection signal S22 that is asserted when a load current IL flowing through an output stage of the main amplifier 4 is larger than a predetermined threshold current ITH. A voltage control section 30 reduces the absolute values of the positive and negative power-supply voltages generated by the power-supply circuit 2 when the voltage detection signal S21 is negated. Moreover, the voltage control section 30 increases the absolute values of the positive and negative power-supply voltages generated by the power-supply circuit 2 when the voltage detection signal S21 is asserted or the current detection signal S22 is asserted. <P>COPYRIGHT: (C)2013,JPO&INPIT |
