Using system fuzzy logic as control technology have been used on low load dc-dc converter with combined parallel compiled dc-dc converter can obtain big load. With existance of differrence of component parameter and each parallel compiled converter can obtained different current and voltage output. Function of controller for to do adjustment so that current which is applied to load by each converter can be obtained difference error as small as possible or same. The object of research is developing design of large signal dc-dc converter which is combined with using FLC so that obtain better performance. To get better performance have been made plant model and simulation with CDE method. The more systematic system and design is needed to overcome bigger load on dc-dc converter so that parallel compiled current master slave control system on dc-dc converter with using fuzzy logic controller is used. Result of research showed that error or difference of current which is applied to load can handled by fuzzy logic controller. Technic of current and voltage controller co to do adjustment current and voltage distribution equally to load. Distribution of iL1 iL2 and output voltage Vo on dc-dc converter with load 2 25 until 7 875 and voltage 100 until 120 volt load current beetwen 12 until 48 % relatif error Vo 0 4% until 0 9%.