Re: Current-driving a powerful IR-illuminator array

On Fri, 31 Mar 2006 16:03:02 +0200, Jacques
<jacquesNOT.fournier@xxxxxxxxxxxxxxx> wrote:

Put the 40 LEDs in serie, so you only need one power supply, say
60..80V, with one resistor-in-serie (a few watts) and a MOSFET to switch
ON and OFF.

Jacques

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BW wrote:
Hi! I want to drive a fairly powerful IR-illuminator array using
high-efficiency IR-LED's (Agilent HSDL-4230 to be specific), which can
support continous currents of 100 mA and peak currents of up to 500 mA.
I want perhaps 40 of these.. and essentially I want to flash them all
in sync to an electronic camera shutter of around 1 ms width, with a
duty-cycle of perhaps 1-to-30. Now when googling around for suitable
circuits, most refer to relatively small power demands, with LEDs that
use a current of only a tenth of this.. both with resistors and with
MAX-circuits etc.

Would it be crazy to try to get the right current by the old
resistor-in-series trick ? Obviously running 20 amps continously
through some resistors would be crazy but here the duty-cycle is so
high that on average the current is only 20/30 amps..

Is there a better way of say switching the LED array with some
darlington transistors and having an additional circuit that monitors
the current and adjusts the current into the transistors to regulate ?

Regards,
Bjorn


--
John Fields
Professional Circuit Designer
.

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