Current-balancing controller requirements of automotive multi-phase converters with coupled inductors

Voltage perturbations at the input of automotive multi-phase converters with coupled inductors can lead to significant equalizing currents in the converter and perhaps to core saturation and system failure, if adequate balancing control is not adapted. Analyses have been performed to predict the equalizing currents in the coupled inductors dependent on the input perturbations and dependent on the design of the coupled inductor. Results of these analyses demonstrate the need of a current-balancing controller and show that the required performance of the controller and the current measurement devices is heavily dependent on the coupled inductor design. A full size automotive prototype converter with four interleaved phases and coupled inductors has been built and tested. Measurements with the four-phase prototype converter are in close correlation with theoretical predictions from the analyses.