SOUND SOURCE DRIVING CIRCUIT AND VOLUME CONTROL METHOD

摘要

PROBLEM TO BE SOLVED: To freely control the volume of a sound like a beep tone for operation confirmation by a simple and inexpensive method. SOLUTION: The level of a reference voltage (DC component) for limiting the amplitude itself of a speaker driving AC signal (or the height of a pulse) is determined on the basis of a voltage provided by averaging a pulse width modulation(PWM) signal by using a smoothing circuit.