Isolated low-power multi-output DC-DC converters with heterogeneous loads for an efficient supply of modular power electronics systems

Appropriate isolated supply solutions for recent power converters, such as distributed smartgrid units or modular multilevel converters, have to provide sufficient power reserve, but often suffer from low efficiency at partial load, causing unnecessary large power loss in the converter control unit. Particularly in modular multilevel converters, the power supply does not only affect the overall efficiency in partial-load conditions, but with its input voltage range importantly determines the module capacitor size and thus a major cost factor. This contribution will present a low-power isolated multi-output DC-DC converter with wide input voltage range (4.5 V to 30 V) for the application in power electronics supply. The presented solution includes a design routine for planar transformers, eliminating the need for custom-made wound transformers and cutting down costs with an all-SMD approach. Experimental results show an almost flat efficiency curve above 80% from 0.3 W to 3 W for an input voltage from 10 V to 20 V. The prototype implements 6 heterogeneous outputs rated from 5 V, 100 mA to 15 V, 60 mA and four times 15 V, 20 mA.