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Design of monolithic power converters with fast reference-tracking

Authors Wu, Ying
Issue Date 2009
Summary For system-level advantages such as power reduction and linearity improvement, emerging applications such as dynamic-voltage-scaled (DVS) systems and supply-modulated power amplifiers (PAs) require dynamic power supplies providing fast reference-tracking. Conventional power supplies are mainly designed for providing fixed output rather than fast-changing output; and this research aims at bridging this gap through both theoretical studies and specific IC design examples. First, the dynamics of reference-tracking in switching converters is analyzed in both large-signal and small-signal perspectives. Loop-gains and reference-to-output transfer functions are derived and verified by a modified Matlab-based simulator. The different behaviors between reference-tracking and load transient are clarified. Common fix-frequency control schemes including voltage-mode control, current-mode control and V2-control are studied and the latter is found to be inherently slow in reference-tracking. Feed-forward control is employed to improve the reference-tracking of V2-control by 10 times. The undershoot and overshoot of output voltage and inductor current in the resulting reference-tracking are analyzed in time-domain; and a control scheme with adaptive control voltage is proposed. Specific circuits are designed for this controller and are verified by a prototype chip, in which a near-optimal reference-tracking is measured for different output voltages and step-size. For low-output-ripple applications, a Pseudo-Type III compensated Buck converter is proposed. It has fast load transient as the conventional Type III approach; while the area and power consumption of the controller is saved by more than 70%. The proposed converter has slow reference-tracking, which can be greatly improved by feed-forward control. A two-phase switching amplifier and a wideband linear amplifier with low output impedance is proposed as a PA supply to raise its static efficiency and lower its output ripple. Feed-forward bandpass filter, two-phase ramp-generator, and adaptive dead-time control are proposed to enhance the dynamic efficiency. Measurement results show successful tracking of a full-swing 4MHz rectified sine wave.
Note Thesis (Ph.D.)--Hong Kong University of Science and Technology, 2009
Language English
Format Thesis
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