Switching Optimization for Class-G Audio Amplifiers with Two Power Supplies

This paper presents a system-level method to decrease the power consumption of integrated audio Class-G amplifiers for mobile phones by using the same implementation of the level detector, but by changing the parameters of the switching algorithm. This method uses an optimization based on a simplified model simulation to quickly find the best power supply switching strategy in order to decrease the losses of the internal Class-AB amplifier. Using a few relevant equations of Class-G on the electrical level and by reducing the number of calculation points, this model can dramatically reduce the calculation time to allow power consumption evaluation in realistic case conditions compared to the currently available tools. This simplified model also evaluates the audio quality reproduction thanks to a psycho-acoustic method. The model has been validated by comparing model results and practical measurements on two industrial circuits. This proposed model is used by an optimizer based on a genetic algorithm associated with a pattern search algorithm to find the best power supply switching strategy for the internal Class-AB amplifier. The optimization results improve life-time performance by saving at least 25% in power consumption for typical use-case (1mW) compared to the industrial circuit studied and without losses in audio quality.

[1]  N. Abouchi,et al.  Improved Class-K amplifier for headset applications , 2010, Proceedings of the 8th IEEE International NEWCAS Conference 2010.

[2]  Milan Petrovic,et al.  Statistical Properties of Music Signals , 2009 .

[3]  Eric Mendenhall.  Computer-Aided Design and Analysis of Class B and Class H Powr Amplifier Output Stages , 1996 .

[4]  F. Raab.  Average Efficiency of Class-G Power Amplifiers , 1986, IEEE Transactions on Consumer Electronics.

[5]  Kalyanmoy Deb,et al.  Muiltiobjective Optimization Using Nondominated Sorting in Genetic Algorithms , 1994, Evolutionary Computation.

[6]  Tohru Sampei,et al.  Highest Efficiency and Super Quality Audio Amplifier using MOS Power FETS in Class G Operation , 1978, IEEE Transactions on Consumer Electronics.

[7]  Thomas Sporer,et al.  PEAQ - The ITU Standard for Objective Measurement of Perceived Audio Quality , 2000 .

[8]  Jeongjin Roh,et al.  Class-D Audio Amplifier Using 1-Bit Fourth-Order Delta-Sigma Modulation , 2008, IEEE Transactions on Circuits and Systems II: Express Briefs.

[9]  Adam D. Downey,et al.  A Class-G/FB Audio Amplifier , 2007, IEEE Transactions on Consumer Electronics.

[10]  Rinaldo Castello,et al.  A Class-G Headphone Amplifier in 65 nm CMOS Technology , 2010, IEEE Journal of Solid-State Circuits.

[11]  El-Ghazali Talbi,et al.  Metaheuristics - From Design to Implementation , 2009 .

[12]  Remy Cellier,et al.  A 0.01%THD, 70dB PSRR Single Ended Class D using variable hysteresis control for headphone amplifiers , 2009, 2009 IEEE International Symposium on Circuits and Systems.

[13]  Robert Michael Lewis,et al.  Pattern Search Algorithms for Bound Constrained Minimization , 1999, SIAM J. Optim..

[14]  Marc Pastre,et al.  High-efficiency dynamic supply CMOS audio power amplifier for low-power applications , 2009, Microelectron. J..

[15]  Rui Seara,et al.  Analysis, Design and Assessment of Class A, B, AB, G and H Audio Power Amplifier Output Stages Based on Matlab Software , 2001 .