Automotive Powertrain DC/DC Converter with 25kW/dm(exp3) by using SiC Diodes

In this paper a 100kW buck-boost DC/DC converter for use in the powertrains of hybrid cars is presented. Since size and weight of the converter are of essential importance for this application, a target size of 4 liter was defined, resulting in a benchmark power density of 25kW/dm(exp 3). Currently available silicon carbide Schottky diodes allow switching frequencies of up to 100kHz when combined with ultrafast 600V IGBTs. This switching frequency, however, is not sufficient to realize the necessary size reduction. A polyphase approach has been chosen therefore. Twelve phases shift the fundamental frequency of the input and output ripple voltage above one megahertz, resulting in a great size reduction of the passive components. The converter operates with a coolant temperature of up to 85deg C without derating. An overview of the converter design is given as well as loss and efficiency calculations.