Keep an eye on newer DC DC converter ICs which are claiming efficiencies
well above what has traditionally be achieved. Also be aware that these
claims are liable to be under carefully specified conditions :-)

Of especial interest to me are ICs which opertae on as little as a single
flat AA alkaline cell (0.7v) with peak efficiencies of up to 96% claimed.
(!)

eg from Linear Technology.
AFAIK the following all allow 0.7V to 4.2V Vin

LTC3400 95% ThinSOT synchronous boost. Vout = 5V at 300 mA

LTC3440 buck boost. 96% MSOP 3.3V at 600 mA

LTC3405 Synchronous boost 95% Thin SOT 1.8V @ 300 mA

I suspect that the synchronous rectification is the key enabling technology
here.

Several versions available from Digikey. None cheap. From about $US3.50 up
in small quantities.


        RM

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