Extending the Supercapacitor-Assisted Low-Dropout Regulator (SCALDO) Technique to a Split-Rail DC-DC Converter Application

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, split-rail 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.