Showing items related by title, author, creator and subject.

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  Development of Monolithic Switched-Capacitor Power Converters for Self-Powered Microsystems

  Ma, Dongsheng Brian; Su, Ling; Ma, Dongsheng Brian; Rozenblit, Jerzy W.; Wang, Meiling Janet; Abedinpour, Siamak (The University of Arizona., 2009)

  Modern electronics continues to push past boundaries of integration and functional density toward elusive, completely autonomous, self-powered microsystems. As systems continue to shrink, however, less energy is available on board, leading to short device lifetimes (run-time or battery life). Extended battery life is particularly advantageous in the systems with limited accessibility, such as biomedical implants and structure-embedded micro-sensors. The power management process usually requires compact and efficient power converters to be embedded in these microsystems. This dissertation introduces switched-capacitor (SC) power converter designs that make all these techniques realizable on silicon.Four different integrated SC power converters with multiple control schemes are designed here to provide low-power high-efficient power sources. First, a monolithic step-down power converter with subthreshold z-domain digital pulse-width modulation (DPWM) controller is proposed for ultra-low power microsystems. The subthreshold design significantly reduces the power dissipation in the controller. Second, an efficient monolithic master-slave complementary power converter with a feedback controller that purely operates in subthreshold operation region is discussed to tailor for the aforementioned ultra-low power applications. Third, we introduce an efficient monolithic step-down SC power stage with multiple-gain control and on-chip capacitor sizing for self-powered microsystems. The multiple-gain control helps the converter to constantly maintain high efficiency over a large input/output range. The size-adjustable pumping capacitors allow the output voltage to be regulated at different desired levels, with a constant 50% duty ratio. The monolithic implementations in these three integrated CMOS power converters effectively suppress noise and glitches caused by parasitic components due to bonding, packaging and PCB wiring. Fourth, an efficient step-up and step-down SC power converter with multiple-gain closed-loop controller is presented. The measurements and simulation results in these four power converters demonstrate the techniques proposed in this research. The approaches presented in this dissertation are evidently viable for realizing compact and high efficient SC power converters, contributing to next generation power-efficient microsystems designs.
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  A Power Combiner for Step Level High Power UHF Solid State Transmitters

  Rose, B. E.; Hughes Aircraft Company (International Foundation for Telemetering, 1969-09)

  A combining network is described which satisfies the requirements of low loss, compact size and input port selection capability. This power combiner, which follows a basic network scheme suggested by E. J. Wilkinson, uses helical wound quarter wave lines for impedance matching, relays for switching inputs in or out, and thick film resistors in the isolation network. The combiner was designed for a UHF solid-state transmitter for a communications satellite. The power level is in excess of 300 watts. From 8 to 16 inputs, from coherently driven power amplifiers, can be selected by command. This step level feature provides a very useful means to achieve maximum utilization of prime power as well as an improvement in reliability through redundancy. Design equations are given for the units. The results of a computer study of losses due to unequal input phases and amplitudes are presented. The equivalent circuit of the network, including parasitics, is described and the compensating elements are discussed. Tests have been made on the completed flight unit, and these results are plotted and discussed.
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  Beta function quintessence cosmological parameters and fundamental constants – I. Power and inverse power law dark energy potentials

  Thompson, Rodger I; Univ Arizona, Steward Observ (OXFORD UNIV PRESS, 2018-07)

  This investigation explores using the beta function formalism to calculate analytic solutions for the observable parameters in rolling scalar field cosmologies. The beta function in this case is the derivative of the scalar phi with respect to the natural log of the scale factor alpha, beta(phi) = d phi/d ln(a) Once the beta function is specified, modulo a boundary condition, the evolution of the scalar phi as a function of the scale factor is completely determined. A rolling scalar field cosmology is defined by its action which can contain a range of physically motivated dark energy potentials. The beta function is chosen so that the associated 'beta potential' is an accurate, but not exact, representation of the appropriate dark energy model potential. The basic concept is that the action with the beta potential is so similar to the action with the model potential that solutions using the beta action are accurate representations of solutions using the model action. The beta function provides an extra equation to calculate analytic functions of the cosmologies parameters as a function of the scale factor that are not calculable using only the model action. As an example, this investigation uses a quintessence cosmology to demonstrate the method for power and inverse power law dark energy potentials. An interesting result of the investigation is that the Hubble parameter H is almost completely insensitive to the power of the potentials and that A cold dark matter is part of the family of quintessence cosmology power-law potentials with a power of zero.