Galvanic isolated auxiliary power supply with high power density and efficiency

Current isolated DC/DC converters with wide input and output voltage ranges achieve power densities from 2 kW/dm 3 to 5 kW/dm(3). In this paper, a galvanic isolated 500 W auxiliary power supply with a power density of 9.2 kW/dm(3) and peak efficiency of up to 96.1 % is presented. In the first chapter, suitable fields of application, like electrical or hybrid cars and DC-grids, are mentioned. In the second chapter, basic considerations of the converter's electrical design are presented. The topology of the half bridge with center taped synchronous rectifier is shown. In the third chapter, the assembly concept is presented, by taking cost and manufacturability into account. In order to achieve these design targets, a complete planar assembled power part with PCB integrated transformer and output inductance was chosen. The converter's mechanical design is described. In the fourth chapter, the cooling concept is discussed. The realization is shown by means of the power stage's PCB design. The main components of the power stage are thermally characterized. The verification of the chosen cooling concept is carried out with thermal measurements. It is shown that all components are operating in their permanent allowed temperature ranges. In the last chapter, the DC/DC converter is characterized. It is shown that with different transformer designs the efficiency curve can be matched to the load profile of the desired application. With this optimization the average system efficiency can be significantly improved. Furthermore the utilization of the 500 W DC/DC converter in a 3 kW DC/DC converter system, to further improve the converter system's part load efficiency, is investigated. The ideal load distribution between the two converters or rewording phases is calculated and the achievable system efficiency is diagrammed. At light load conditions, like power safe modes, up to 25 % efficiency gains were realized.