Optimum Biasing for Parallel Hybrid Switching-Linear Regulators

Hybrid combinations of switching and linear regulators have been proposed for both audio amplifiers and dynamic supply modulators for radio frequency (RF) power amplifiers (PAs). Such topologies may provide benefits in terms of efficiency, dynamic range, and speed of dynamic response compared to pure linear regulators or class-D switching amplifiers. This paper presents a framework for analyzing the bias constraints of switching and linear voltage regulators operated in a parallel-hybrid configuration. Particular emphasis is given to polar and envelope tracking RF power amplifier (RF PA) applications. Ideal expressions are derived for the optimum current contribution of the switching regulator under quasi-static operating conditions. In contrast to previous work, it is shown that the optimum mean current contribution of the switching regulator is not necessarily the dc current to the load. Explicit expressions for theoretical maximum efficiency are derived for envelope waveforms that result from two-tone and sinusoidal amplitude modulation of the RF carrier; IS-95 CDMA and IEEE 802.11a/g wireless LAN envelope waveforms are treated in simulation and experiment. Theoretical predictions are validated with measured results.

[1]  L.E. Larson,et al.  Design of wide-bandwidth envelope-tracking power amplifiers for OFDM applications , 2005, IEEE Transactions on Microwave Theory and Techniques.

[2]  L. Risbo,et al.  A Digital Input Controller for Audio Class-D Amplifiers with 100W 0.004% THD+N and 113dB DR , 2006, 2006 IEEE International Solid State Circuits Conference - Digest of Technical Papers.

[3]  A.V. Peterchev,et al.  A 4-/spl mu/a quiescent-current dual-mode digitally controlled buck converter IC for cellular phone applications , 2004, IEEE Journal of Solid-State Circuits.

[4]  S.R. Sanders,et al.  Power supply rejection for common-source linear RF amplifiers: theory and measurements , 2006, IEEE Radio Frequency Integrated Circuits (RFIC) Symposium, 2006.

[5]  John F. Sevic,et al.  Statistical characterization of RF power amplifier efficiency for CDMA wireless communication systems , 1997, Proceedings of 1997 Wireless Communications Conference.

[6]  Seth R. Sanders,et al.  Converter IC for Cellular Phone Applications , 2004 .

[7]  Robert H. Caverly,et al.  HF, VHF, and UHF systems and technology , 2002 .

[8]  Seth R. Sanders,et al.  Dynamic Power Supply Design for High-Efficiency Wireless Transmitters , 2006 .

[9]  Robert G. Meyer,et al.  Analysis and Design of Analog Integrated Circuits , 1993 .

[10]  A.J.M. van Tuijl,et al.  A power efficient audio amplifier combining switching and linear techniques , 1998, Proceedings of the 24th European Solid-State Circuits Conference.

[11]  Philip T. Krein,et al.  Elements of Power Electronics , 1997 .

[12]  Pallab Midya.  Linear switcher combination with novel feedback , 2000, 2000 IEEE 31st Annual Power Electronics Specialists Conference. Conference Proceedings (Cat. No.00CH37018).

[13]  Nathan O. Sokal,et al.  Near-Optimum Dynamic Regulation of DC-DC Converters Using Feed-Forward of Output Current and Input Voltage with Current-Mode Control , 1986, IEEE Transactions on Power Electronics.

[14]  P. Reynaert,et al.  A 1.75-GHz polar modulated CMOS RF power amplifier for GSM-EDGE , 2005, IEEE Journal of Solid-State Circuits.

[15]  T. Karnik,et al.  Area-efficient linear regulator with ultra-fast load regulation , 2005, IEEE Journal of Solid-State Circuits.

[16]  A.V. Peterchev,et al.  Load-Line Regulation With Estimated Load-Current Feedforward: Application to Microprocessor Voltage Regulators , 2006, IEEE Transactions on Power Electronics.

[17]  E. Alon,et al.  Replica compensated linear regulators for supply-regulated phase-locked loops , 2006, IEEE Journal of Solid-State Circuits.

[18]  E. McCune,et al.  High-efficiency, multi-mode, multi-band terminal power amplifiers , 2005, IEEE Microwave Magazine.

[19]  G.A. Rincon-Mora,et al.  A high-efficiency linear RF power amplifier with a power-tracking dynamically adaptive buck-boost supply , 2004, IEEE Transactions on Microwave Theory and Techniques.

[20]  R. Pullela,et al.  Quad-band GSM/GPRS/EDGE polar loop transmitter , 2004, IEEE Journal of Solid-State Circuits.

[21]  L. Larson,et al.  Envelope tracking power amplifier with pre-distortion linearization for WLAN 802.11g , 2004, 2004 IEEE MTT-S International Microwave Symposium Digest (IEEE Cat. No.04CH37535).

[22]  Philip T. Krein,et al.  High-fidelity PWM inverter for digital audio amplification: Spectral analysis, real-time DSP implementation, and results , 2003 .

[23]  Robert W. Brodersen,et al.  High-efficiency low-voltage dc-dc conversion for portable applications , 1994 .

[24]  J.R. Wells,et al.  Selective harmonic control: a general problem formulation and selected solutions , 2005, IEEE Transactions on Power Electronics.

[25]  Peter M. Asbeck,et al.  High-efficiency power amplifier using dynamic power-supply voltage for CDMA applications , 1999 .

[26]  A.V. Peterchev,et al.  Digital Multimode Buck Converter Control With Loss-Minimizing Synchronous Rectifier Adaptation , 2006, IEEE Transactions on Power Electronics.

[27]  F. Raab,et al.  Power amplifiers and transmitters for RF and microwave , 2002 .

[28]  M. Declercq,et al.  A fast modulator for dynamic supply linear RF power amplifier , 2003, ESSCIRC 2004 - 29th European Solid-State Circuits Conference (IEEE Cat. No.03EX705).

[29]  Eduard Alarcón,et al.  Efficiency optimization in linear-assisted switching power converters for envelope tracking in RF power amplifiers , 2005, 2005 IEEE International Symposium on Circuits and Systems.