| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve a problem that the conventional power amplification device achieves reduction in power consumption by changing power supply voltage according to a signal level to be amplified, the circuit is complicated and cost increases, moreover, a voice delays, and a synchronization shift arises when it is used in a home theater system. Ž<P>SOLUTION: The reduction in power consumption and avoidance of the voice delay can be achieved by composing the device with: a volume which adjusts a sound volume of an input signal of a power amplification circuit for a low frequency band and a power amplification device for a middle-high frequency band; a volume control circuit which outputs a volume position detection signal while controlling the volume; a signal level detection circuit which detects an amplitude of an output signal of the power amplification circuit for the low frequency band; a voltage variable power supply circuit which supplies power to the power amplification circuit of the low band frequency and the power amplification device for the middle-high frequency band; a power supply voltage control circuit which controls voltage of the voltage variable power supply circuit based on the detection result of the signal level detection circuit and the volume position detection signal output from the volume control circuit. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž
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