Improving the light-load efficiency of VRMs using parallel inductors

With increasing emphasis on energy and efficiency, a major concern for Voltage Regulator Modules (VRMs) is their operation during light-loads. VRMs are usually optimized at one load level, which is in the 50 - 100% range. Therefore operating at load levels significantly lower than this produces inefficient operation, resulting in reduced battery life (in laptops) or increased electricity costs. This work proposes switching off one or more parallel inductors according to the load level, thus eliminating associated inductor core loss and significantly reducing connected MOSFET losses. Using this technique it is shown that an improvement of up to 17% in efficiency is achieved at 10% of full-load for a typical VRM solution.