Protection and Supervision of DC-DC Converters for Electronic Telephone Switching Systems

Power conversion equipment in electronic switching systems require protection against faults that may cause damage to the equipment. The most severe faults which must be protected against are those that would cause an electrical fire. Basic protection techniques such as fusing and current limiting are well known and widely utilized. Enhanced protection is provided by an automatic shutdown technique which monitors the outputs of a converter for both high and low conditions and causes a shutdown in the event of a fault. Typical fault conditions and the protection provided by the automatic shutdown circuit are analyzed. Supervision of DC-DC converters in electronic telephone switching systems is required to implement local power control zones and to achieve configuration control. A power supervision circuit is described which provides a flexible means of linking independent converters in common local power control zones. The manual and system interfaces which contribute to configuration control are also described.