Supercapacitor-assisted low dropout regulator technique: a new design approach to achieve high-efficiency linear DC–DC converters

Supercapacitor-assisted low dropout regulator technique: a new design approach to achieve high-efficiency linear DC–DC converters

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Approximate efficiency of a linear regulator is given by the ratio of regulated output voltage to input voltage. Higher voltage difference between the input and the output means a lower efficiency due to heavy losses in the series power semiconductor. Supercapacitor-assisted low dropout regulator (SCALDO) is an emerging linear DC–DC converter technique, where a supercapacitor (SC) is used to reduce the voltage drop across the series transistor in a linear regulator where the SC acts as a lossless dropper. The circuit operates at a very low frequency decided by the size of the SC. An efficiency multiplication factor such as 1.33, 2, or 3 is achieved depending on the configuration. This study presents the essentials of its generalised theory, few prototype implementations, and a discussion on SCALDO properties. Typical efficiencies of 12–5 and 5–1.2 V linear regulators are around 42 and 24%, respectively. When SCALDO prototypes are built, the authors achieve respective end-to-end efficiencies of 79–81 and 58–73%. A loss analysis summary and further developments of the novel technique are also provided, in addition to a discussion to indicate that this is not a variation of the switched capacitor converters.


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