HYBRID PULSE-WIDTH MODULATION SIGMA-DELTA MODULATION POWER DIGITAL-TO-ANALOG CONVERTER

A new digital signal processing technique is presented for power digit al-to-analogue converters which offers high linearity and a substantia l reduction in clock frequency compared to conventional pulse width mo dulation converters. The basis of the technique is to group together p ulses from the output of a single bit sigma-delta modulator. A model i s derived which shows that the system output is essentially a pulse wi dth modulated sequence. Noise and distortion are introduced by the pul se grouping but are considerably reduced using noise shaped feedback a round the pulse grouper. Simulation results are presented which valida te the model and indicate the performance of the technique with ideal and nonideal output stages.