Systems and methods of driving a light source, such as a light emitting diode (LED), while minimizing power consumption. Different techniques can be implemented in circuits that eliminate the traditional need for a sense resistor. By eliminating the sense resistor, a LED driving circuit's efficiency can be improved by up to and exceeding 30%. A pulse-width modulator can be used to control current flow in a buck, boost, or buck-boost circuits. Many of the configurations discussed eliminate the need for a sense resistor, which needlessly dissipates power. Others use a sense resistor minimally compared to traditional LED driving circuits.