Quiet power up and power down of closed loop digital PWM modulators

摘要

A switching audio amplifier circuit drives a switching audio amplifier stage using a digital PWM signal from an audio source. A PWM duty ratio modifier modifies an edge timing of the digital PWM signal to produce a modified digital PWM signal. A mode switch switches between the digital PWM signal and the modified digital PWM signal in a way that masks audible noise such as clicks and pops at power-up and power-down of the switching audio amplifier. An integrating error amplifier compares a difference between the digital PWM signal and an amplified PWM signal and integrates the difference to control the edge timing modified by the PWM duty ratio modifier. A mode controller can apply an offset signal to the integrating error amplifier and can control the switching of the mode switch.