Modulation and System Techniques in PWM and SDM Switching Amplifiers

Continuous- and discrete-time switching audio power amplifiers are studied both with and without feedback. Pulse-width modulation (PWM) and sigma-delta modulation (SDM) amplifier configurations are simulated and their interrelationship is described using linear phase modulation (LPM) and linear frequency modulation (LFM). Distortion generation encountered when applying negative feedback to PWM is demonstrated and strategies to improve linearity are presented. Recent innovations in SDM coding and output-stage topologies using pulse-shaping techniques are reviewed with emphasis on stable, low-distortion operation, especially under high-level signal excitation. A simplified low-latency variant of predictive SDM with step back is introduced, which together with dynamic compression of the state variables extends stable operation to a modulation depth of unity, thus allowing SDM to compete with PWM power amplifiers in terms of peak signal capability.

[1]  Malcolm J. Hawksford,et al.  System measurement and identification using pseudorandom filtered noise and music sequences , 2005 .

[2]  Richard H. Small Constant-Voltage Crossover Network Design , 1971 .

[3]  L. Risbo Σ-Δ Modulators - Stability Analysis and Optimization , 1995 .

[4]  Karsten Agersted Nielsen High-Fidelity PWM-Based Amplifier Concept for Active Loudspeaker Systems with Very Low Energy Consumption , 1997 .

[5]  Mark Sandler,et al.  Digital Power Amplification Using Sigma-Delta Modulation and Bit Flipping , 1997 .

[6]  Malcolm J. Hawksford Parametrically Controlled Noise Shaping in Variable State-Step-Back Pseudo-Trellis SDM , 2003 .

[7]  John Mourjopoulos,et al.  Analytic Derivation of Audio PWM Signals and Spectra , 1998 .

[8]  Malcolm J. Hawksford Dynamic Model-Based Linearization of Quantized Pulse-Width Modulation for Applications in Digital-to-Analog Conversion and Digital Power Amplifier Systems , 1992 .

[9]  Malcolm J. Hawksford Time-Quantized Frequency Modulation, Time-Domain Dither, Dispersive Codes, and Parametrically Controlled Noise Shaping in SDM , 2004 .

[10]  P.J.A. Naus,et al.  A CMOS Stereo 16 Bit D/A Converter for Digital Audio , 1986, ESSCIRC '86: Twelfth European Solid-State Circuits Conference.

[11]  M. Hawksford Unified theory of digital modulation , 1974 .

[12]  W. Marshall Leach Loudspeaker Driver Phase Response: The Neglected Factor in Crossover Network Design , 1980 .

[13]  James A. S. Angus Tree Based Lookahead Sigma Delta Modulators , 2003 .

[14]  Malcolm J. Hawksford,et al.  Application of delta-modulation to television systems , 1972 .

[15]  Yoshizumi Inazawa,et al.  Super Audio CD Format , 1998 .

[16]  Malcolm J. Hawksford,et al.  Digital Audio Power Amplifier for DSD Data Streams , 2004 .