NDLI: A micropower low-distortion digital class-D amplifier based on an algorithmic pulsewidth modulator

Content Provider	IEEE Xplore Digital Library
Author	Bah-Hwee Gwee Chang, J.S. Adrian, V.
Copyright Year	2004
Abstract	A digital Class-D amplifier comprises a pulsewidth modulator (PWM) and an output stage. In this paper, we simplify the time-domain expression for the algorithmic PWM linear interpolation (LI) sampling process and analytically derive its double Fourier series expression. By means of our derivation, we show that the nonlinearities of the LI process are very low, especially given its modest computation complexity and low sampling frequency. In particular, the total-harmonic distortion (THD) /spl ap/0.02% and foldback distortion is -98.4 dB (averaged from modulation indexes M=0.1 to 0.9) for the 4-kHz voiceband bandwidth @1-kHz input, 48-kHz sampling. We also describe a simple hardware for realizing the LI process. We propose a frequency doubler (with small overheads) for the pulse generator for the PWM, thereby reducing the counter clock rate by 2, leading to a substantial /spl sim/47% power dissipation reduction for the Class-D amplifier. By means of computer simulations and on the basis of experimental measurements, we verify our double Fourier series derivation and show the attractive attributes of a Class-D amplifier embodying our simplified LI sampling expression and reduced clock rate pulse generator. We show that our Class-D amplifier design is micropower (/spl sim/60 /spl mu/W @1.1 V and 48-kHz sampling rate, and THD /spl ap/0.03%) and is suitable for practical power-critical portable audio devices, including digital hearing aids.
Sponsorship	IEEE Circuits and Systems Society
Starting Page	2007
Ending Page	2022
Page Count	16
File Size	850419
File Format	PDF
ISSN	15498328
Volume Number	52
Issue Number	10
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2005-10-01
Publisher Place	U.S.A.
Access Restriction	One Nation One Subscription (ONOS)
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Pulse amplifiers Space vector pulse width modulation Digital modulation Pulse modulation Pulse width modulation Sampling methods Fourier series Frequency Pulse generation Clocks sampling process Class-D amplifier digital hearing aids linear interpolation pulse generator pulsewidth modulation (PWM)
Content Type	Text
Resource Type	Article
Subject	Electrical and Electronic Engineering Hardware and Architecture

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