| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a fixed sound generator and a switching amplifier capable of reducing power consumption when outputting a fixed sound, such as a beep sound, an alarm and the like, from a loudspeaker immediately after power-on, and of preventing an abnormal noise. <P>SOLUTION: When a command signal S1 for generating a fixed sound, such as a beep sound and the like, for the purpose of notifying an operator of an operation state at an operation of an audio device 11 is inputted to a fixed sound controller 2 from a built-in microcomputer 12 of the audio device 11, the fixed sound controller 2 and a fixed sound generation part 4 generate a fixed sound generation signal S8. A voltage variable power supply part 6 adds a voltage component of the signal S8 to a power supply voltage of a power amplification stage 8. A PWM modulator 3 generates a PWM modulation signal S4 having a pulse width depending on a value of an audio signal in an output time period of the audio signal, and generates the PWM modulation signal having a predetermined pulse width in a fixed sound generation time period. The power amplification stage 8 switches the power supply voltage by the PWM modulation signal to amplify a power of the audio signal and/or the fixed sound. <P>COPYRIGHT: (C)2013,JPO&INPIT |
