31.6 A SIDO/DISO VCF-Step-Reconfigurable Continuously Scalable-Conversion-Ratio SC Converter Achieving 91.4%/92.6% Peak Efficiency and Almost-lossless Channel Switching

In an energy harvesting (EH) system for the internet of things (IoT), the input voltage V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> may vary within a wide range, e.g., from 0.3 to 1.8V from a solar cell, while the battery voltage V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BAT</inf> and output voltage V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OUT</inf> are usually higher than V <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> . Figure 31.6.1 shows a dual-mode DC-DC converter for EH interface: Single-Input-Dual-Output (SIDO) and Dual-Input-Single-Output (DISO). In SIDO, the converter delivers power from source to both load and battery as POUT< PIN. Once POUT> PIN, the converter is in DISO mode, delivering both source and battery power to the load. A switched-capacitor (SC) converter is favorable for low-power EH interfaces. Previous works have used two-stage schemes [1, 2], i.e., not converting P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">IN</inf> directly to P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">OUT</inf> or P <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">BAT</inf> . This could isolate inputs or outputs, however, is not area efficient. In [3] and [4] a series multiplexer MUX for channel selection is employed, but the loss from MUX is considerable.