LIGHTING DEVICE HAVING A CIRCUIT INCLUDING A PLURALITY OF LGHT EMITTING DIODES, AND METHODS OF CONTROLLING AND CALIBRATING LIGHTING DEVICES

摘要

A lighting device ( 132 ) includes a circuit having a power supply and a plurality of light emitting diodes ( 120 ) connected in series with the power supply. The plurality of light emitting diodes ( 120 ) includes at least two groups of series-connected light emitting diodes, the groups of series-connected light emitting diodes being connected in series. A different optically isolated field effect transistor (U 3 -U 5 ) is connected in parallel with each group of series-connected light emitting diodes, for selectively shunting around the group of series-connected light emitting diodes. A different capacitor (C 8 -C 10 ) can also be connected in parallel with each group of series-connected light emitting diodes. A controller (U 2 ) is connected to a gate of each of the optically isolated field effect transistors (U 3 -U 5 ) for selectively turning the optically isolated field effect transistors (U 3 -U 5 ) on and off. Thus, the controller U 2 is electrically isolated from the power supply by the optically isolated field effect transistors (U 3 -U 5 ). The light emitting diodes ( 120 ) can be driven and controlled using pulse width modulation methods.