| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent an output transistor from causing thermal breakage due to temperature rise, and to prevent a power supply voltage that is supplied to an amplifier circuit from switched to a low voltage, resulting in distortion of audio signal. <P>SOLUTION: When the voltage from a second power supply circuit 3 is a first threshold value or higher and the level of an output signal of an amplifier circuit 6 is a second threshold value or higher, a voltage switching part 4 is controlled so that a normal voltage is outputted from a secondary winding 1B of a transformer 1. When the voltage from the second power supply circuit 3 is less than the first threshold value, or the output signal of the amplification circuit 6 is less than the second threshold value, the voltage switching part 4 is controlled so that a low voltage is outputted from the secondary winding 1B of the transformer 1. <P>COPYRIGHT: (C)2008,JPO&INPIT |
