A hybrid bidirectional DC-DC converter for dual-voltage automotive systems

With the increasing power demand of automotive systems, a 42V power system has the trend to coexist with the traditional 14V system in order to decrease the system current stress. In the dual-voltage and dual-battery architecture, a compact, high efficient and bidirectional DC/DC converter is typically needed. In this paper, a hybrid bidirectional DC-DC converter for 42/14V dual-voltage automotive systems is presented. This converter is a hybrid combination of a switched-capacitor converter and an inductor-based converter with low number of components, whose input current ripple and peak charging current are small with the help of the inductor. The nominal duty cycle for the 42/14V system is 0.5, so it will not go to extreme values even if the battery is overcharged to a higher voltage value or is depleted to a lower voltage value, therefore increasing the voltage-gain range and ensuring high efficiency. A comprehensive analysis of steady-state operation, small signal model and component stress is given. A 42/14V prototype rated at 20~120W with a peak efficiency of 97.8% in boost mode and 98.3% in buck mode was built to verify the analyses.