US Patent 9531156 Endoscopic light source

A light source assembly includes multiple light emitters having output that are focused and mixed onto a optical fiber leading to an endoscope or other device. The emitters can be LEDs or solid state lasers that emit different colors. A driver circuit controls the relative output intensities of the light emitters so as to produce a desired light spectrum. A driver circuit includes a buck topology connected to a controller that provides current mode control. Pulse width modulation of the buck current is provided by a semiconductor switch across a solid state laser. A second order filter, formed by the an external inductor and the output capacitance of the buck topology, minimizes AC current ripple to the laser.