Re: Digital Current Control for LED array

theJackal wrote:
<snip>
The normalized luminance versus current curves for the individual devices is similar in shape across production suggesting that a first-order match of the LEDs by setting the current of each LED for a fixed luminance will result in a "good" match (though not exact) as the current is increased or decreased from the calibration point. The differences of luminance at other proportional current levels and at other thermal operating points are second-order mismatches.

Here you correctly say you set the currents of each LED for a fixed illuminance the below you contradict yourself by saying a parallel or a series connection of LEDs is
fine. A parallel connection sets the Voltage of each LED as fixed and NOT the current.

The radiant power is a function of Photon emission. Photon emission is determined by hole
electron recombination currents in the quasi neutral n and p regions of the Light
emitting diodes.

By feeding each LED with a controllable current, the voltage will be defined by the LED. These constant-current LEDs can be in series or parallel requiring series or shunt regulation, respectively; it's just easier to have series regulators in a parallel configuration. It also makes the proportional control much simpler. 


A series regulator  in a parallel connection IS totally bad. Because you are changing  not
only the voltage and current of 1 LED  but of ALL  the other LEDs . That doesn't happen if
its in a series connection.

"Go easy on the whisky"

theJackal

I am suggesting 7 regulators for 7 LEDs. Of *course* connecting 7 LEDs in parallel directly with one series regulator will not provide a solution. Of *course* connecting 7 LEDs in series with one shunt regulator will not work. If one "LED stage" is defines as an LED and a regulator, 7 "LED stages" can be connected in parallel if the "LED stage is built with a series regulator and 7 "LED stages" can be connected in series if the "LED stage is built with a shunt regulator.

I don't contradict a thing. EACH LED is fed with a controllable current. Separately. Not "all LEDs are fed with A controllable current."
.

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