Optimal switch resistances in Switched Capacitor Converters (original) (raw)
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Abstract Switched capacitor converters have become more common in recent years. Crucial to understanding the maximum power throughput and efficiency is a model of the converter's equivalent resistance. A new form for equivalent resistance is derived and discussed in a design context. Quasi-resonant operation is also explored and compared to non-resonant operation. Several capacitor technologies are evaluated and compared
The effect of switching transitions on switched capacitor converters losses
The contribution of the rise and fall times of switches to the losses of Switched Capacitors Converters was evaluated by an approximate analysis applying the equivalent resistance concept. It was found that switch turn-on and turn-off durations increase the equivalent resistance of the converter and, consequently, the losses, except in the case of complete charge/discharge of the flying capacitors within the switching phase. Loss increase is related to the fact that during the current rise/fall state, the instantaneous losses are much higher than when the switch is in a constant 'on' state. Theoretical predictions were validated by full circuit simulations and experimental results. The present study integrates the switching losses into the generic equivalent resistance loss model, enabling the calculation and/or simulation of the total losses in switched capacitor converters.
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The energy-efficiency issue of switched-capacitor converters is still a controversial topic that requires a more in-depth discussion. In this paper, we address the issue by dividing the analysis of the entire efficiency problem into two parts. In the first part, the efficiency of a capacitor-charging RC circuit under different aspects (partial charging, full charging, at zero capacitor voltage, at nonzero capacitor voltage, etc.) will be conducted. The efficiency analysis of a capacitor-discharging RC circuit with a resistor, capacitor, and paralleled resistor-capacitor loads will be covered. A complete evaluation of the overall efficiency is then performed in terms of both the charging and discharging efficiencies. Based on the analysis, some design rules useful for developing highefficiency switched-capacitor converters is suggested. Additionally, it is shown that the belief that quasi-switched-capacitor converters are more lossy than switched-capacitor converters is a common misconception. Index Terms-Charging efficiency, discharging efficiency, flying capacitor, full charging, full discharging, partial charging, partial discharging, quasi-switched-capacitor (QSC) converter, switchedcapacitor (SC) converter. I. INTRODUCTION S WITCHED-CAPACITOR (SC) converters have the advantages of small size, lightweight, and high-power density due to the absence of magnetic components, which make them suitable for use in portable electronics like cellular phones, digital cameras, and MP3 players [1]. With the increasing demand for smaller and lighter power converters, semiconductor companies are introducing new and more advanced types of SC converters in IC packages, such as MAX5008 and LM2758, for commercial applications. Within the research domain of SC converters, energy efficiency is still a frequently discussed and debated issue among researchers [1]-[40]. Careful review of the literature shows that there are still many conflicting viewpoints and inconsistencies.
A new visit to an old problem in switched-capacitor converters
ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems, 2010
The energy-efficiency issue of the switched-capacitor converters is still a highly controversial topic that requires a more in-depth exploration. This paper will address the issue by dissecting the analysis of the entire efficiency problem into two parts. In the first part, the efficiency analysis of charging the capacitor of an RC circuit under different aspects (partial charging, full charging, at zero capacitor voltage, at non-zero capacitor voltage, etc.) will be conducted. In the second part, the efficiency analysis of discharging the capacitor of an RC circuit with resistive and capacitive loads will be covered. A complete evaluation of the overall efficiency is then performed in terms of both the charging and discharging efficiencies of the capacitor. Additionally, it is shown in this paper that the claim that quasi-switched-capacitor converters are more lossy than switched-capacitor converters is a common misconception.
Analysis and Optimization of Switched-Capacitor DC–DC Converters
IEEE Transactions on Power Electronics, 2000
Analysis methods are developed that fully determine a switched-capacitor (SC) dc-dc converter's steady-state performance through evaluation of its output impedance. The simple formulation developed permits optimization of the capacitor sizes to meet a constraint such as a total capacitance or total energy storage limit, and also permits optimization of the switch sizes subject to constraints on total switch conductances or total switch volt-ampere (V-A) products. These optimizations then permit comparison among the switched-capacitor topologies, and comparisons of SC converters with conventional magnetic-based dc-dc converter circuits, in the context of various application settings. Significantly, the performance (based on conduction loss) of a ladder-type converter is found to be superior to that of a conventional boost converter for medium to high conversion ratios.
Analysis, design, and applications of switched-capacitor converters
2016
Nowadays, with the increasing demand for smaller and lighte r power converters in commercial electronics, there is an increasing popularity in b oth the research and the development of switched-capacitor (SC) converters. With the abs ence of inductors and bulky transformers, the power density of SC converters is improve d as compared to traditional switching mode power supplies. Moreover, the possibility o f fabricating an entire SC converter into an integrated circuit (IC) chip has resulted in many companies producing SC converter ICs and many portable electronic products adop ting such ICs. The purpose of the thesis is to summarize the previous resear ch works and report the accomplished works. A literature review is included to summ arize the research efforts of SC converters. Converter topologies, modeling works, co ntrol methodologies, practical applications, and the industrial market development of SC converters are discussed. Limitations of previous works are highlighted and ...
Practical performance analysis of complex switched-capacitor converters
2011
Abstract This paper introduces a new analysis technique for complex switched-capacitor (SC) converters. It uses conventional circuit analysis methods to derive state-space models of each switching mode. Steady-state performance is derived and expressed as an equivalent resistance.
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Fundamental charge vector method analysis is a single parameter optimization technique limited to conduction loss assuming all frequency-dependent switching (parasitic) loss negligible. This paper investigates a generalized structure to design DC-DC SC converters based on conduction and switching loss. A new technique is proposed to find the optimum value of switching frequency and switch size to calculate target load current and output voltage that maximize the efficiency. The analysis is done to identify switching frequency and switch size for two-phase 2:1 series-parallel SC converter for a target load current of 2.67mA implemented on a 22nm technology node. Results show that a minimum of 250MHz switching frequency is required for target efficiency more than 90% and the output voltage greater than 0.85V where the switch size of a unit cell corresponds to 10Ω on-resistance. MATLAB and PSpice simulation tools are used for results and validation.