Can LEDs be dimmed?
The forward current is proportional to the light output of an LED over a large operating range, so dimming can be achieved with reductions in the forward current.
Because LEDs can be rapidly switched on and off with no harmful effects, dimming can also be accomplished using a method called pulse width modulation. By adjusting the relative duration of the pulse and the time between pulses, the apparent intensity of the LED can be dimmed. This must be done with high enough frequency (hundreds of thousands of modulations per second) that the LED appears to be continuously lighted, or else the rapid flickering will be distracting. This technique can be easily implemented electronically using direct digital control.