Silly errors in design or A vendor gets embarrased

I'm taking a break from cleaning my mother's house (she fell and broke
her hip so I have been here the last few days), so I thought I'd relate
the latest vendor embarrasment.

One of my products is basically a very rugged XDA with 5.7" QVGA TFT
and I'm moving to LED backlighting (from CCFL) for a number of reasons
and a vendor came in with their latest and greatest offering.

Great price; ~£58 in 1k qtys for the TFT, controller (standard 33 way
FFC interface) and LED backlights, _but_ the designers bring out only a
single power pair for the LEDs, which are arranged as 3 parallel
strings of 7 series white LEDs, and no control circuitry. That price is
nearly half the closest competition, incidentally.

This, of course, can easily lead to current hogging above hotspots, and
did so *even on their own demo unit*. One end of the display was
noticeably brighter than the rest of the screen, probably because the
processor and/or power supply for the unit sits in that area. One might
have expected their on demo unit to be 'tweaked' for such things, at
least. The rep went quite pink when I opinted it out ;)

I explained to the rep that the best way is to bring out all 3 series
power separately (as Kyocera does) so they can all be separately
regulated to ensure equal current (and therefore equal light) from each
chain. Of course, with each string being separately powered (A and K)
it's pretty simple to do balancing if the strings aren't that well
matched.

I won't name the vendor (yet) as they are not in production and I'll
see if they bring out a 6 wire power interface for the LEDs. Gotta give
them a chance to rectify it.

I found it amusing that such a basic piece of design was implemented so
crappily.

Cheers

PeteS [posting via google for a few days]

.

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