Bus-voltage ripple optimization method for automotive multiphase DC/DC-converters

Phase interleaving is a well known technique to increase output power, power density, and efficiency of DC/DC-converters. If the n-phase converter is ideal (symmetrical), the first n-1 harmonics of the ripple are canceled in the bus-capacitors and the cut-off frequency of the EMI-filters can be increased. But tolerances of real components and control circuit can seriously limit this theoretical benefit. Tolerances of phase-shift, storage inductors and phase-current sensors are investigated to determine the causes of an unsymmetrical converter system. In order to ensure near ideal ripple cancellation despite high phase-current sensor tolerances, an approach using closed-loop control of the 1st harmonic is introduced and tested experimentally. This approach significantly improves the current balancing performance of an automotive two-phase converter.

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