A cheap, current-regulated Luxeon Star driver design

Power dissipated in the current programming resistor is a consideration at these load currents: P = 1.25V * 0.32 A = 400mW, so a 1/2W resistor is required for the 320 mA design. Power dissipated in the regulator will be dependent on the value of Vin, so be aware that a heatsink will likely be necessary to cool the regulator depending on your input and load voltages.

Input voltage is a consideration. The voltage drop across the load has to be less than Vin minus about three volts. The three volt drop is made up of the internal voltage drop across the regulator circuitry, plus the drop across the current programming resistor.

What this means in practice is that this design is perfectly suited to drive several Luxeon Star LEDs in series as long as you can provide a DC input voltage high enough to overcome the forward voltage drop of the series combination plus the three volt drop for the driver.


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