Browse Prior Art Database

System to Determine the Mode of Conducted Noise

IP.com Disclosure Number: IPCOM000036140D
Original Publication Date: 1989-Sep-01
Included in the Prior Art Database: 2005-Jan-28
Document File: 3 page(s) / 48K

Publishing Venue

IBM

Related People

Price, LA: AUTHOR

Abstract

To provide an IBM product that can meet the FCC and other national requirements in the most efficient manner the EMC engineer must be able to provide a power line filter that is designed for the problem at hand.

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System to Determine the Mode of Conducted Noise

To provide an IBM product that can meet the FCC and other national requirements in the most efficient manner the EMC engineer must be able to provide a power line filter that is designed for the problem at hand.

The use of switching power supplies (regulators) is almost universal in the computer industry. The cost and efficiency advantages of this technology are numerous. However, not without problems, i.e.: conducted RF energy (noise).

Almost every nation has adopted EMC regulations that govern the amount of conducted RF noise that is permitted for electronic equipment. The nature of operation of switching power supplies cause them to produce large amounts of conducted RF energy. In order to control the conducted noise and comply with regulations it is usually necessary to incorporate some type of power line filter. In addition to providing for RF noise the design must also consider the ground current "green wire."

In order to provide an efficient power line filter, that meets the ground current requirements, it is necessary to fully understand the characteristics of the conducted noise that is to be attenuated. To do this we must know the amount of common-mode and differential-mode noise current. Because these noise currents are frequency dependent, the type of noise current at each frequency must be determined for each phase.

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The system herein disclosed can measure the conducted RF noise current from a single or multi-phase power system. It will determine the mode of noise current vs. frequency. With this information the most efficient and cost effective power line filter can be used to meet the requirements.

The major component is the pick-up system, shown in Fig. 1. It is comprised of a stabilization network (C1, C2, and L) for each phase and ground. All trans...