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Compensation for Pulse Delays in Electric Field Active Cancelling

IP.com Disclosure Number: IPCOM000117202D
Original Publication Date: 1996-Jan-01
Included in the Prior Art Database: 2005-Mar-31
Document File: 2 page(s) / 51K

Publishing Venue

IBM

Related People

Beeteson, JS: AUTHOR

Abstract

In active TCO cancelling circuits (TCO is the abbreviated names for the Swedish Confederation of Professional Employees. TCO cancelling circuits reduce electric field emissions from electrical appliances in accordance with TCO standards for electric field emissions), there is a need for very accurate inverting amplification of the EHT voltage variations received by the TCO sensor attached to the CRT glass faceplate.

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Compensation for Pulse Delays in Electric Field Active Cancelling

      In active TCO cancelling circuits (TCO is the abbreviated names
for the Swedish Confederation of Professional Employees.  TCO
cancelling circuits reduce electric field emissions from electrical
appliances in accordance with TCO standards for electric field
emissions), there is a need for very accurate inverting amplification
of the EHT voltage variations received by the TCO sensor attached to
the CRT glass faceplate.

      These signals are very complex, covering a wide dynamic range
and frequency band.  One of the components is a pulse a few
microseconds wide produced by the EHT generating flyback voltage.
The amplification of this pulse inevitably produces a signal delay
(of the order of 0.25 microseconds).  In active cancelling this delay
causes blips at the front and back edges of the cancelled emission
signal.  Thus, both a lower limit is placed on the degree of
cancellation achievable, and there is a need for the highest
bandwidth (and therefore most expensive) amplifiers.  It has been
necessary to use amplifiers with a bandwidth of 20 MHz.

      Described is a way of compensating for this delay, so reducing
the cancelled emission or allowing the use of a wider range of lower
cost amplifiers.

      The EHT pulse is triggered by a logic signal from the control
circuits.  By generating low amplitude pulses of a controlled delay
and shape relative to the trailing edge of the...