Highly reliable power-supply system for fiber-optic subscriber network systems

NTT (Japan) has developed a highly reliable, small, high-efficiency and high-power-factor power supply system for fiber-optic subscriber network systems. The power supply system is composed of a rectifier block, a ringer block, a common circuit block, and other components. Every block is implemented as a PWB (printed wiring board) package and is removable from the power subrack for easy maintenance. The power stage of the rectifier is a flyback power converter that uses a magnetic switch to correct the power factor and convert from 100 V AC to regulated 48 V DC in only one stage. Furthermore, the system can control battery charge voltage when temperature varies and it can evaluate battery capacity. The efficiency of the rectifier is 90.8% at full load and the power factor is 0.97. The volume of the power supply is 60% of the conventional power supply.