50mOhm series resistor and the rectifier drop, to start. Without a synchronous rectifier, conduction losses really pile up.
Hahahaha, what was that all about 
Yes, yes the best is synchronous rectification , but Ill be very happy with “only” 85% eficiency
It's a (modified) commercial jingle for Wrigley's Doublemint gum.
Great job! Looks like getting it down to 17mm is possible.
Awaiting testing data to see how these perform. Very interesting design.
Now components is in 18mm circle all in 1 side, so 20mm possible, but 17mm … 1 side … hmmm ;)) Boost driver without big coil wont work ;))
Am I the only one who gets the Big Ass Spider reference, or am I just late to the game?
Its impressive that you have got it down to 18mm. Is there a reason you dont want to go double side?
This design could easily fit 17mm if you stuck some of the smaller components on the oppisite side. Just leave the center for positive to solder on a copper stud or small spring.
In time, I think Aundril will be adapted to work with boost. There’s a few members working on it.
Which e-switch flashlight using 17mm driver? Another question. Which e-switch drivers diameter most common and popular and desirable?
Most desirable are currently for 14500/AA size if you ask me.
14500/AA…. Its not a driver size
17 mm is considered the most common, across the board. But I've been seeing 20, 21, 22 mm's pretty often lately. Going smaller, AA size, 15 mm would be the next smaller size, I would consider AA size. But of course there are exceptions to every rule or assumption 
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17mm is probably the most common as Tom E said. The easiet way is to make it as small as you feel comfortable working with then just change the pcb size to accomodate different size lights. That way the driver can fit many lights just by changing the pcb size in the design without having to go thru the process of designing a new layout.
I do not know any popular light with e-switch and 17mm driver. Why go small? Better change host with more space ;)). Tomorrow last hope. I will get FET with same specs only more powerful as is in original Tamagoshi schematics.
On BLF any light can become a host. There is plenty of lights out there that use 14500/AA with e-switch and a lot of 16340 lights also. Its your design, you design it as you see fit.
I have a Ultratac A1 using this driver with a XHP50.2 making 2000 lumens with a 14500 very floody. Its not a e-switch but I could have used a Sofirn SP10S, Thorfire TK05, or a Utorch UT01 for a host if the driver had been eswitch capable.. A XHP35.2 might be interesting in one of these host.
To name one (set), the Sofirn C8F family of lights use a 17 mm driver with e-switch. These lights are simple, powerful, and flexible, even available as a host, as well as triple LED's and singles. I got a few of these lights - outstanding modder's platform.
The C8 popularized the 17 mm size, as well as P60's (power switch), and even bigger lights like the HD2010 (power switch also).
OK, ill do 17mm later … if ill get running this schematic properly at all ;))
Is there temp regulation ? Have you measured the efficiency ?
Looks good. Nice job Quadrupel. A boost driver with good UI is not really available before this that I know of? What are the LED currents of the modes? I’m curious is the FW based on existing FW?
Another niche that needs filling is a linear FET driver with good e-switch UI. I would buy one for my H03.
There is overheat protection, you can set it manually, turn it on or off, but with off there is no turbo mode ;))
I have no proper tools to measure efficiency but should be much better than linear driver have anyway.
You can choose LVP level 3v; 2.5v and 2.2v
For reverse polarity using P-FET but , need to order new PCBs again with 3x3mm FET, because 2x2 is to weak.
The soft is advanced , but its not open source, i can not edit it. I’m just replicating schematic with some improvement in PCB design and trying to use more powerful and cheaper components and its not so simple , because soft is coded for specific hardware and sensitive to any hardware changes; ;))