Sensorless Current Sharing Analysis and Scheme for Multiphase Converters

Current sharing control in multiphase converters is essential for stable and safe operation under variable conditions or applications. In conventional current sharing schemes, this requires the sensing and processing on each phase current through a current sharing/balancing controller, which adds complexity, size, and cost to the converter design. In most cases, conventional schemes are usually based on achieving a pre-set current sharing ratio between phases (usually equal current value among different phases), assuming that the phase design is known (or symmetric in the case of equal sharing ratio), which may not result in the optimum efficiency. The accuracy of achieving the pre-set current sharing ratio is sensitive to the current sensing accuracy in all phases, which requires careful and tedious calibration of sensing circuitries. In this paper, theoretical analysis results are presented to derive a sensor less current sharing method. The analysis is further expanded to reveal the boundary conditions that result in not achieving the desired current sharing ratio. The presented method is described and verified with experimental results from a proof of concept prototype based on digital controller implementation.