Hybrid pulse width modulation/sigma-delta modulation power digital-to-analogue converter

A new digital signal processing technique is presented for power digital-to-analogue converters which offers high linearity and a substantial reduction in clock frequency compared to conventional pulse width modulation converters. The basis of the technique is to group together pulses from the output of a single bit sigma-delta modulator. A model is derived which shows that the system output is essentially a pulse width modulated sequence. Noise and distortion are introduced by the pulse grouping but are considerably reduced using noise shaped feedback around the pulse grouper. Simulation results are presented which validate the model and indicate the performance of the technique with ideal and nonideal output stages.