Patent ID: 6107875
Filing Date: 2000-08-22
Classification: H03F

Abstract:
A closed loop class D amplifier comprising:an integrator having a plurality of inputs including an audio input, an audio feedback input, and a digital feedback input;a comparator for receiving the output of the integrator and generating a series of pulses, each pulse corresponding to one of two states of the comparator and having a width proportional to the slope of the output of the integrator, and a variable frequency;a driver circuit for receiving the pulse output of the comparator and generating gate drive signals proportional in duration to the width of the pulses;a bridge circuit comprising two or more MOSFETs, each MOSFET having its gate coupled to one of the gate drive signals;a low pass filter coupled to the output of the bridge for converting the bridge output into a power signal representative of the audio input signal;means for sensing the output state of the comparator and the time that the comparator has been in said output state; andmeans coupled to the input of the integrator for selectively adding or removing current to the integrator in order to reduce the gain of the amplifier and maintain the switching frequency of the comparator above the frequency of the audio input.