Patent ID: 7580532
Filing Date: 2009-08-25
Classification: H03F,H03G,H03M

Abstract:
1. A multi-channel PWM (Pulse Width Modulator) apparatus, comprising: a plurality of pulse width modulators for modulating audio signals into PWM-based multi-channel audio signals; and a gain control unit, connected to the plurality of pulse width modulators, for independently controlling gains of the audio signals received at the plurality of pulse width modulators, wherein the gain control unit independently controls gains of at least a portion of the audio signals to be at different levels according to individual channels, the gain control unit controlling gains of at least the portion of the audio signals so that control of the gain of each of the portion of audio signals is not limited by control of the gain of the other audio signals, wherein the gain control unit comprises: a plurality of gain controllers, each varying a level of a respective audio signal of the multi-channel audio signals received at a corresponding one of the pulse width modulators; a plurality of comparators, each coupled to an output of a corresponding one of the gain controllers, that compare levels of audio signals generated from the gain controllers with a reference level; AGC (Automatic Gain Controller) configured to receive output signals of the comparators for variably controlling the gain controllers according to individual output signals of the comparators; and a plurality of adders that perform addition or subtraction operations based on control signals generated from the AGC and volume control signals for said channels, and independently varying gains for said channels based on results of the addition or subtraction operations, wherein each of the adders receives two input signals being a corresponding volume control signal and a corresponding control signal from the said AGC for a respective one of the channels, and outputs an independent gain control signal to a corresponding one of the gain controllers.