On Thu, 14 Jan 2010 16:39:53 -0800, Archimedes' Lever
wrote:

On Thu, 14 Jan 2010 07:16:21 -0800, John Larkin
wrote:

On Thu, 14 Jan 2010 06:53:35 -0600, John Fields
wrote:

On Wed, 13 Jan 2010 19:15:56 -0800, John Larkin
wrote:



If you use 14 volts to run a 3.4 volt LED, with a dissipative system,
the efficiency is always around 24%. Different circuits just move the
heat around.

With pairs of LEDs in series, efficiency becomes 6.8/14 = 48%.

---
Yes, but if one fails shorted the second one will follow soon after if
its If(max) is exceeded, while if one fails open two will go out so
you're trading efficiency for reliability.

JF

Sure, except that LEDs rarely fail.

John

Those used for lighting have a higher failure rate. For a panel, they
will likely never fail.

Just convert the 14V down and waste nothing with a silly dissipative
circuit. Drive each directly, and use a dedicated current limit resistor
on each. Brightness consistency becomes accurately repeatable, and there
are no failure modes that would cause others to fail as a result.

Excuse me, but that makes no sense. A schematic would help.

John