12.3 A 2-output step-up/step-down switched-capacitor DC-DC converter with 95.8% peak efficiency and 0.85-to-3.6V input voltage range

Switched-capacitor (SC) DC-DC converters have gained attention based on their ability to offer a low-cost high-efficiency power conversion, and allow a thin and compact module packaging [1]. However, the SC DC-DC converter offers high efficiency only in a limited input/output voltage range, since it is inherently based on a discrete conversion ratio, which is different from an inductor-based DC-DC converter with a continuous conversion ratio. [2,3] proposed implementing multiple conversion ratios with several SC DC-DC units connected in series. However, these lead to a degradation of the efficiency as well as the maximum current capacity, worse for the conversion ratios that have more stages. On the other hand, there is a lack of a step-up and step-down SC topology, which will further expand the input/output voltage range, and enable using different types of power sources (alkaline, lithium-ion battery, etc.), for portable devices. [4] and some commercial products offer both step-up and step-down conversions, but the step-down conversions are limited to a unity conversion ratio. In this paper, we present a step-up/step-down unified topology that covers the input voltage range from 0.85V to 3.6V, and the output voltage range from 0.1V to 1.9V. Moreover, a dual-output topology with a 4-way channel mapping and an on-demand channel sharing control is also proposed, for delivering 2 regulated voltages with good efficiencies and fast transient responses.