Abstract: A class D amplifier uses a summation of two or more PWM output stages to achieve an increased dynamic range and improved linearity for any given clock operating speed. The amplifier accepts a digital data stream as its input, such as from a compact disk, or other compatible media, at a data rate, Fa, that could be 44.1 kHz, 96 kHz, or any other rate appropriate for audio data. In the preferred embodiment, the input audio data resolution, N bits, would be split into two data samples, of J and K.
Internal switching frequency, Fs, switches the PWM with an over sampling factor M, where Fs=M*Fa. The time resolution of the PWM is determined by a precision oscillator that operates at Fc=Fs*(max(J,K)−log2(M)+1).
The J most significant bits would be routed to a power PWM stage operated at a DC voltage of VHI. The K least significant bits are routed to a finesse PWM stage operated at a DC voltage of VLO.
Type:
Grant
Filed:
December 10, 2001
Date of Patent:
July 15, 2003
Inventors:
William Harris Groves, Jr., Arthur Alan Aaron