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High Intensity LED Drive Solutions 15

One of the questions that comes up is how would you dim the LED? There are a couple of ways that we could consider doing the dimming for the LED. The simplest way to dim an LED drive would be to change the current through the LED, which does change the intensity of the output. However, it has a couple of disadvantages. First, it is a very non-linear transfer function between intensity and current, and secondly, you get a color shift in the output light of the LED. A better way to dim the LED is to do a low frequency, pulse width modulation of the constant current drive. By choosing a PWM frequency around 100 hertz, this would be above the visible range that you would detect with the eye, but you could dim the LED by putting a 100 hertz PWM and controlling the constant current drive with that 100 hertz PWM. This can easily be accomplished with the boards that we have by modulating the feedback from the sense resistor and controlling the board in that way.

PTM Published on: 2011-11-03