That quote was also useful for calculating efficiency of a linear driver. If I apply the formula for user case the efficiency is less great. If I usually ran a SST40 @ 250lm it would itself use ca. 2.75V. (see Luminus SST-40, a N4 BA bin tested)
Using the formula, I get an efficiency of 1/2 * (2,75/4,2 + 2,75/2,9 [if I use the battery slightly below 3v]) = 80%.
I read somewhere that the efficiency of switching drivers runs between 75-85% but also that Simon Mao claimed 95% for his 8A buck driver. Perhaps I should hold off until an equivalent 4A driver for C8+ shhould trickle down. Could that happen?
What I really would like to know now, is how Simon’s C8+ SST40 driver —also with an 8A mode (and 1.5A mode; said to be a regulated FET driver)— compares with that of say a regular M21A or a C8G?