In this paper, a fuzzy controller for DC-DC converters is proposed in order to obtain good performances that can not be achieved by liner control techniques in the presence of wide parameter variz. tions. The presented approach is general and can he applied to any DC-DC converter topologies. While the conventional method uses error and derivative of error, the proposed controller method uses state variables. Such method is very efficient in case of DC-DC converters and can guaranlee both stable small-signal responses and improved large-signal responses. Application results of boost converter(booster) show control potentialities.