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The traditional inductor-based buck converter has been the default design for switched-mode voltage regulators for decades. Switched capacitor (SC) dc-dc converters, on the other hand, have traditionally been used in low-power (<;10 mW) and low conversion ratio (<;4:1) applications where neither regulation nor efficiency is critical. This study encompasses the complete successful design, fabrication, and test of a CMOS-based SC dc-dc converter, addressing the ubiquitous 12-1.5 V boardmounted point-of-load application. In particular, the circuit developed in this study attains higher efficiency (92% peak, and >80% over a load range of 5 mA to 1 A) than surveyed competitive buck converters, while requiring less board area and less costly passive components. The topology and controller enable a wide input range of 7.5-13.5 V. Controls based on feedback and feedforward provide tight regulation under worst case line and load step conditions. This study shows that the SC converter can outperform the buck converter, and thus, the scope of SC converter application can and should be expanded.
Date of Publication: Sept. 2013