Calibration Method of Equivalent Series Resistance Parameter for Nonintrusive Current Sensors Used in DC–DC Power Electronic Converters

Nonintrusive current sensors process indirect measurements (e.g., voltage) in order to estimate the current flow through an electrical element. Within dc–dc power electronic converters, instead of using an additional current sensor(s), high-frequency inductor currents within the topology can be estimated by measuring inductor terminal voltages using simple low-cost comparators used with digital postprocessing circuits. The figure of merit for such sensors depends upon the accurate identification of sensor transfer function. This transfer function relates inductor terminal voltage to estimated current, and consists of two major parameters, i.e., inductance (
L
) and equivalent series resistance (ESR), of the element. Both the parameters vary with changes in operating conditions, e.g., temperature, and additional trace resistances. Variation of ESR parameter introduces dc offset within the estimated current measurement, and hence an accurate knowledge of ESR is essential for closed-loop stability of dc–dc converters. This letter presents a calibration method of ESR parameter for nonintrusive current sensors used in dc–dc power electronic converter applications. The theory behind the proposed approach, its implementation aspects, and verification are presented in this letter.