All electrical and electronic devices require access to a suitable energy source. In a portable electronic product, such as a cell phone, an energy storage unit drives a complex array of power conversion stages to generate multiple DC voltage rails required. To optimize the overall end-to-end efficiency, these internal power conversions should waste minimal energy and deliver more to the electronic modules. Capacitors are one of the main component families used in electronics, to store and deliver electric charges. Supercapacitors, so called because they provide over a million-fold increase in capacitance relative to a traditional capacitor of the same volume, are enabling a paradigm shift in the design of power electronic converter circuits. Here we show that supercapacitors could function as a lossless voltage-dropping element in the power conversion stages, thereby significantly increasing the power conversion stage efficiency. This approach has numerous secondary benefits: it improves continuity of the supply, suppresses voltage surges, allows the voltage regulation to be electromagnetically silent, and simplifies the design of voltage regulators. The use of supercapacitors allows the development of a novel loss-circumvention theory with applicability to a wide range of supercapacitor-assisted (SCA) techniques. These include low-dropout regulators, transient surge absorbers, LED lighting for DC microgrids, and rapid energy transfer for water heating.
The Supercapacitor-assisted low-dropout (SCALDO) regulator is a unique new DC-DC converter design approach with high end-to-end efficiency (ETEE), where a supercapacitor is used as a lossless voltage dropper in the series path of a linear regulator. This technique, in which the energy recovery happens at a very low frequency (typically in millihertz), with an efficiency multiplication factor in the range of 1.33 to 3, can be used in many different applications. For example, in a 12-5V linear converter where the theoretical maximum efficiency is 41.67%, the SCALDO approach improves it to 83.33%. The SCALDO technique has been extended to multiple useful applications proving its versatility and has been identified as an entirely different approach compared to conventional switched capacitor converters. In this paper, we provide an in-depth discussion on the expansion of the SCALDO technique into a dual-polarity, splitrail DC power supply with high ETEE, high current, high slew-rate capability and other desirable features. It also presents the experimental results for a 12V to ± 5V prototype with steady-state performance, transient response capability, load/line regulation, and loss estimation.
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