Sensorless current estimation and sharing in multiphase buck converters

Virtually, all of the current-sensing methods for power converters presented to date rely on a priori knowledge of circuit parameters to ensure accurate current measurement. Also, the advent of digital control in low-cost high-volume applications - such as voltage regulator modules (VRMs) for computer microprocessors - has added the challenge and cost of analog-to-digital conversion to this task. This paper introduces a parameter-independent, sensorless current-sharing algorithm for multiphase power converters based on gradient estimation via low-frequency perturbation of the per-phase duty cycles, thus eliminating the need for current sensing. Measures of only the input and output voltages are required, so the analog-to-digital converter (ADC) and communication/interfacing overhead is low. The algorithm is demonstrated through both simulation and experimental implementation using a digitally controlled three-phase buck converter.