On Mon, Mar 24, 2008 at 3:16 PM, Steve Smith wrote: > I think the topology that does both boost an d buck is Sepic but that is > limited to small currents due to the coupling capacitor... > There are six type of single controlled switch DC/DC converters as proved by some power electronic experts in VT (CPES, last time called VPEC, http://www.cpes.vt.edu/) the 1980s. 1) Buck 2) Boost 3) Buck-boost 4) Cuk 5) SEPIC 6) Zeta Buck-boost and Cuk can do negative step-up and step-down. SEPIC and Zeta can do positve step-up and step-down. BTW, TI has a nice posted on common DC/DC converter topology. http://focus.ti.com/lit/ml/sluw001a/sluw001a.pdf Xiaofan (who has very good theoretical background in Power Electronics yet currently struggling with a simple full-bridge converter) -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist