The advent of high-power LEDs capable of replacing incandescent bulbs has produced a need for circuits that efficiently match the LEDs to available power sources (such as batteries and car electrical systems). The circuits should also be able to regulate and control the LED light output, despite variations in output voltage from the power source. This application note describes a circuit based on a buck/boost converter controller that regulates current to a white LED, despite an allowed variation of input voltage from 2.7V to 16.5V.