I'm probably about to offer the manufacturer both TL499 and CD40106 
based design and let them choose the one which works out cheapest 
overall. I'll publish versions of them both with a pointer here as 
they may be useful to others. The CD40106 (hex Schmitt inverter) has a 
nasty parts count but the IC is the dearest single part at about 
$US0.15 or less.  The TL499 design uses far less parts but the IC is 
several times dearer. Both give good quiescent current and OK overall 
performance. The CD40106 is probably more efficient due to the full 
CMOS oscillator. Potentially VERY low quiescent  with great care. I 
have also tried various discrete and IC approaches but all are either 
too high quiescent or too dear or too flaky under questionable startup 
conditions or samples not available to me here right now.

> The problem with the low cost SMPS controllers is the
> quiescent current. This was true 5 years ago and is less
> true now. MC34063 is a quite an old product anyway.

Very old. Excellent for higher power levels where leading edge 
effciency is not an issue. Driver stage is not at all nice inside with 
its darlington driver BUT using it to drive a FET removes the 
saturation issue and transforms it. Driving a FET was not something 
the makers ever envisaged "way back then".

> The problem with those nice SMPS controllers from
> Intersil/Maxim/AD/Linear/TI is the relative high cost.

Typically 5 times as much as a MC34063 :-(.

> OnSemi/Fairchild/National/IR may produce some cheaper
> product. There are some new players from Asia whose
> product are less know to the public though.

These I'd be interested in but I need samples here NOW and they also 
need to be available in Taiwan soonish.
Next time round maybe.


                RM 

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