The small, light-weight and modular Lunar rover must survive several earth days in harsh environment after its moon landing. Its power electronic system with integrated solar generation needs power for its mission and also to stay warm in very cold temperatures of the moon. This paper presents the design of the power electronic system of the Lunar Zebro rover. Two topologies are compared that result from using a 12 V bus and 24 V bus. The design of the DC/DC converters required is presented for CCM and DCM operation. The losses in the DC/DC converters operating in CCM and DCM are calculated for the two bus voltages to determine the mode of operation and bus voltage that results in the highest efficiency. Further, the average power loss during operation of the rover is estimated for both bus voltages. Operating the DC/DC converters in CCM using a 12 V bus results in the lowest losses.