Development of Converters in NTT

This paper discribes power converters used and in the research phase in NTT. Nowadays, almost all converters are semiconductor converters. Since they are efficient, small and reliable, they are used in many telecommunication systems. Recent progress in the telecommunication systems enhances the requirement for further converter development. Studies on converters have been continued to minimize size, obtain high reliability, save energy and reduce cost. Small DC-DC converter, high frequency ferroresonant DC-DC converter and compact PWM inverter, which have been studied, are introduced.