US Patent 9241385 Current balancing circuits for light-emitting-diode-based illumination systems

A system including a plurality of switches and a comparator. The plurality of switches is configured to respectively supply a plurality of currents via respective terminals to a plurality of sets of light emitting diodes. The sets of light emitting diodes are configured to respectively output light having wavelengths in a plurality of wavelength ranges in a spectrum of blue light. The comparator is configured to compare a reference voltage to a voltage at one of the terminals of one of the plurality of switches connected to one of the sets of light emitting diodes, and to adjust, based on the comparison, biasing of the plurality of switches to maintain a predetermined ratio of the plurality of currents.