This chart is the CIE color chart with the Constant Current dimming and PWM dimming, with the Luxeon bins shown:
Here is an exploded view of just the data, note the dimming % is listed, % for PWM is the PWM duty cycle, % for Constant Current is the % of the max current:
In the above chart, take note of the percent where the constant current and PWM dimming split, about 50% for the Constant Current. A person could dim with constant current to 50%, then utilize PWM, to minimize color shift, yet pick up the efficiency increase.
Here is the efficiency difference:
Yet that chart only shows half the story, here is the efficiency gain at each step, I was rather surprised here:
Basicially it all boils down to Current Dimming is alot more efficient than PWM dimming (so you get considerably more run time on down to 0.5% current dimming, but PWM dimming results in less color shift. A combination of the two approaches could sure be interesting indeed.
FYI, the current level this Luxeon was ran at is 380.1 mA = 100% Also, the Luxeon emitter slug had a hole drilled into the side and a type-K thermalcouple inserted, the slug temperature variation over the whole test was a maximum of 2.3 degrees Celcius (yes, a large aircooled heatsink was utilized for this). The same emitter is utilized for all sets of data.