Meeting ISDN requirements in a switch mode power converter

The recommendations of Section 9 from CCITT 1.430 include several requirements that make the design of ISDN-compatible power supplies complicated. Solutions to simplify the design task are presented using a new pair of integrated circuits. Specific areas addressed include: providing a highly regulated output voltage while maintaining galvanic isolation; soft starting a power converter with an isolation barrier in the voltage feedback loop; synchronization of an isolated power converter; providing continuous inrush current limit capability; communicating restricted mode and other status information to a secondary-side CPU or controller; handling output overload conditions in a flyback topology; and power consumption budgeting for ISDN restricted mode operation