Improving the End-to-End Efficiency of DC–DC Converters Based on a Supercapacitor-Assisted Low-Dropout Regulator Technique

2015 IEEE Applied Power Electronics Conference and Exposition (APEC)

Steyn-Ross

2015

Self Cite

Supercapacitor-based energy recovery techniques can be coupled with low-dropout regulators to enhance the end to-end efficiency (ETEE) of a linear regulator by multiplication factors such as 1.33, 2 or 3. For example, a 12-to-5 V superca pacitor assisted low-dropout regulator (SCALDO) theoretically achieves 84% ETEE compared to the 42% efficiency of a simple linear regulator. The experimental prototype achieved an approx imate ETEE of 80%. The supercapacitor performs as a lossless voltage-dropper in this SCALDO design, cyclically absorbing energy and releasing to the low-dropout (LDO) regulator at frequencies in the order of few millihertz to a few hundreds of hertz. The reduced-switch SCALDO regulator (R S-SCALDO)is an extension of the basic SCALDO topology that improves current handling capabilities and reducing the number of power switches while combining multiple LDOs with a common output rail. VRMs can be designed with digital potentiometer-assisted voltage identification (VID) feature using the RS-SCALDO. The main focus of this paper is to provide implementation details of an RS-SCALDO circuit to design a low-noise VRM that cycles at extremely low frequencies (e.g. 1 to 500 mHz) and to present the experimental results of a 1.5 V, 5 A proof of concept prototype.

Section: Vpmentioning

confidence: 90%

Section: Vpmentioning

confidence: 99%

An extra-low-frequency RS-SCALDO technique: A new approach to design voltage regulator modules

Wickramasinghe

2015 IEEE Applied Power Electronics Conference and Exposition (APEC)

Steyn-Ross

2015

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“…Fig. 5(b) shows the case of simultaneous discharging of charged SC bank into an identical 12 V LED lamp commencing from 13.5 V to 10 V. A digital controller with suitable ADCs to monitor the resistive loads and SC banks will be able to implement this using a very-low-speed switching scheme similar to the SCALDO technique [13].…”

Section: Proposed New Charging Approachmentioning

confidence: 99%

“…al. to increase the efficiency of linear regulators by inserting a supercapacitor or an array of supercapacitors into the series path of the series pass resistance of a linear regulator [8][9][10][11][12][13]. In this extra low frequency technique, during one phase of the switching cycle, the SC comes in series with the low dropout regulator, by which the end-to-end efficiency is increased by a multiplication factor.…”

Section: Introductionmentioning

confidence: 99%

Supercapacitor energy storage in solar application: A design approach to minimize a fundamental loss issue by partitioning the load and the storage device

2015 IEEE 24th International Symposium on Industrial Electronics (ISIE)

Milani

Round

2015

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When an ideal voltage source is used to replenish an electro-chemical battery with an open circuit voltage of V and a charge of Q coulombs, it stores an energy of QV in the battery, if the charging loop is ideal with no losses. However, if the electro-chemical battery is to be replaced by a capacitor, the energy stored will be ½QV and the loop resistance will dissipate ½QV of energy creating an overall charging efficiency of only 50%. In a solar type application if a supercapacitor (SC) bank replaces a battery, due to its long life and its ability to deliver high power bursts into a load, the designer has to be concerned about this fundamental charging efficiency limitation. However, by splitting the load and the SC bank into two identical halves, and using a series charging scheme where in any given charging process the load and the SC bank comes into series mode, this fundamental loss can be circumvented. The other half of SC bank can deliver energy to the other part of the load.

“…This operation can be maintained and extended to utilize limited DC uninterruptible power supply (UPS) features by modifying the topologies. For instance, paralleling two SCALDOs or RS-SCALDO circuits with considerably larger SC-banks (as in Fig.4(a) and 4(b)) can provide UPS capability to cater for fluctuations and temporary 11 failures in DCµG.…”

Section: Introductionmentioning

confidence: 99%

Supercapacitor-based DC-DC converter technique for DC-microgrids with UPS capability

Wickramasinghe

2015 IEEE First International Conference on DC Microgrids (ICDCM)

Steyn-Ross

2015

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When DC loads are powered by a DC-microgrid (DCµG) based on a renewable source such as a PV system, energy storage becomes mandatory due to fluctuating nature of the source. Localized DC-energy storage within DC-DC converters could address this requirement. A variation of supercapacitorassisted low-dropout regulators (SCALDO) could provide localized energy storage with low-noise and fast transient response. For a generalized SCALDO configuration, end-to-end efficiency is given by ( 1 + k) (v;.eg/Vp) where k equals n or 1 / n, and n is the number of supercapacitors required to step-down an input voltage of v;, to an output regulated voltage of v;.eg· For SCALDO-based converters, (1 + k) is the efficiency improvement factor of a Vp-to-v;.eg standard linear regulator. I. INTRODUCTIO N The rapid development and uptake of electronic appliances requiring DC power has stimulated interest in DC-based power generators [1]. In the last few decades appliances that use renewable DC-energy sources have expanded from a simple solar-powered calculator to an industry-level equipment such as servers in a data center [2]. The fluctuating nature of solar PV and similar DC-energy generation systems motivates use of batteries and supercapacitors for storage [3]-[5].Fig. 1 illustrates a small-scale grid-a DC-microgrid (DCµG) with various DC-components connected via DC-DC converters [2] and a point (point of common coupling (PCC))connects with another microgrid. Due to the proliferation of renewable energy sources with direct DC-outputs, and appliances with electronic power converters, it is both practical and more energy efficient to use DC-DC converters rather than DC-AC and AC-DC converters with their inherent inefficiencies. µGrid dc--dc converter DC power generation system dc--dc converter dc--dc converter DC energy storage ' ' '---Fig. I. DCµG components and its connection with DC-DC convertersThere are three common DC-DC converter design approaches in practical electronic systems: (i) linear regulators, (ii) switched-mode converters with magnetic components (inductors), and (iii) switched-mode converters without magnetic components (switched-capacitors). (i) Linear regulators are simple, low noise and have fast transient response to load and line fluctuation, but they are rather inefficient due to their large dropout voltages (> 1 V). To address this low efficiency issue, a new family of low-dropout regulators (LDO) were introduced in late 1980s; in LDO design the input-to-output differential voltage can be kept very low, typically rv200 m V, to achieve high efficiency. However, the end-to-end efficiency (ETEE) of series linear regulators (Y;egfVp) in wide input-tooutput voltage applications is very low. (ii) Switched-mode regulators have high efficiency, with a theoretical performance of 100% ETEE. But in practice the achieved ETEE is only about 75-90% in general; in addition they emit very high level of RFUEMI and have limited transient response. (iii) Switchedcapacitor converters (SW-CAP) are high-frequency convertors which u...