Power Pack Technology for NTT Digital Local Switching System

This paper describes technologies applied to the power pack for the NTT Digital Local Switching System. To introduce a new physical design into the system, small size, low noise and maintenance free power packs have been required, aiming at setting them in each small sized equipment module, which includes many LSIs. To meet the requirement, the power pack is designed by following advanced technologies. (1) A 200kHz DC-DC converter is used in order to get a thin structure power pack. (2) A large capacitance multi-layer ceramic capacitor, which does not require periodic replacement, is applied to input and output filters in place of an aluminium electrolytic capacitor. (3) A simple filter, whose components are multi-layer ceramic capacitor and common-mode choke coil, is applied to dramatically reduce input and output noises. (4) A high performance power control IC is newly designed to decrease the number of circuit parts. The power packs are superior not only in electrical characteristics but also in equipment design flexibility, maintainability and economization.