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SIMULTANEOUS EMI, SURGE, AND OVERVOLTAGE PROTECTION CIRCUIT

IP.com Disclosure Number: IPCOM000006288D
Original Publication Date: 1991-Dec-01
Included in the Prior Art Database: 2001-Dec-20
Document File: 1 page(s) / 62K

Publishing Venue

Motorola

Related People

J. M. Dwyer: AUTHOR [+3]

Abstract

Figure 1 illustrates a circuit providing simultaneous EMI, surge, and over-voltage protection circuit 19 which meets three overlapping requirements for secure tele- phone communication equipment. This circuit provides a common lead for protection between multiple signal line pairs without affecting normal circuit operation and can operate without connection to earth ground for use in common mode applications.

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MOTOROLA INC. Technical Developments Volume 14 December 1991

SIMULTANEOUS EMI, SURGE, AND OVERVOLTAGE PROTECTION CIRCUIT

by J. M. Dwyer, B. A. Snodgrass, and A. E. Cook

  Figure 1 illustrates a circuit providing simultaneous EMI, surge, and over-voltage protection circuit 19 which meets three overlapping requirements for secure tele- phone communication equipment. This circuit provides a common lead for protection between multiple signal line pairs without affecting normal circuit operation and can operate without connection to earth ground for use in common mode applications.

  Inductors 12.14 depicted in Figure 1 provide the RF choking to eliminate EM1 from or to the distribution circuit. When parallel signal circuits are employed, each external connection lead is separately filtered.

  The combination of inductors 12, 14 and surge protector 16 provide protection against signal line surges. Inductors 12,14 are selected to be able to dissipate surge energy without catastrophic inductor failure. Surge pro- tector 16 (e.g., a SIDAC) clamps the surge voltage to a level which will not result in harm to the protected equipment. The entire circuit is designed such that both the protector circuit and the protected equipment remain operational following a power surge. When parallel signal circuits are utilized with the common leads connected together, surge protection is provided between any two leads.

  This circuit also disconnects the equipment from the signal line when...