piclist 2002\09\25\170905a >
Thread: 2-tran SMPS 5v reg now 90% efficicient!
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picon face BY : Morgan Olsson email (remove spam text)



Regarding efficiency and other spec i use to be very careful.

It takes much calculations and verifying labs to make a design that performes good in all conditions High/low temp, High/low input volt etc, while also have margins for component variations such as min/max hFE of transistors, ESR of caps, etc.  Maybe some combinations cause stability problems.  Also remember zeners have typically 5% tolerance, add voltage change due to current change due to input voltage change, regulation of input volt, and load, and i guess simple regulators like theese have problems qualifying in a lot of areas.

For instance i guess the Black regulator would drop a little in efficiency if we were to have production quality margins for hFE for instance.  Using some combinations of worst case values is sometimes very tough for a cirquit, such problem i use best to solve with pen and paper, as i can not manufacture worst case variants of all componets... but substituting for other cap values, low hFE transstors etc is one way.

Also note that the relatively bigger inductors in the Black is making slower load pulse reponse and also cost more in component cost and board estate if talking production.

But for hobby use as well as some consumer products i find the Black regulator very nice.

Btw, new cadidates for the switch: BD438 (high gain high current pretty low cost TO126) and also check out Zetex "Matrix" range ZTXnnn IIRC for low voltage drop and very high gain.

Another application idea is to use it in battery charger, then with added precision ref and cirquit for end of charge if used for lead or Lithium.

For NiMH use a PIC as timer, and maybe a ref and A/D for -dV/dt.

See, this really is on toPIC  ;)

/Morgan

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