The paper discusses the application of the object oriented design technique to the development of the software for a digital controlled power converter. After a brief presentation of the basic concepts of object oriented design, the specific topic of the application in power electronics is analysed. Starting from this analysis, a new approach for the design of software in this application is presented and the complete life cycle and relative documentation is described. In order to demonstrate the importance and the power of this methodology the paper discusses a practical experience in the development of the software for the firing control of a twelve pulse cycloconverter. In conclusion practical results and control performance are presented.<<ETX>>