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Two Channel Vertical Deflection Amplifier

IP.com Disclosure Number: IPCOM000052281D
Original Publication Date: 1981-May-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 2 page(s) / 52K

Publishing Venue

IBM

Related People

Ainscow, F: AUTHOR

Abstract

In a color CRT display, the vertical deflection has two functions: raster generation and north-south (n-s) pincushion correction. By frequency dividing the signal into two channels, power dissipation is reduced since the load presented by the deflection coil is largely inductive.

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Two Channel Vertical Deflection Amplifier

In a color CRT display, the vertical deflection has two functions: raster generation and north-south (n-s) pincushion correction. By frequency dividing the signal into two channels, power dissipation is reduced since the load presented by the deflection coil is largely inductive.

The raster generation signal is a low frequency signal, but large currents are needed, typically about +/-1.6 A. The n-s pincushion correction signal is a high frequency signal which requires high voltage, typically +/-22 V to drive a relatively small current in the deflection coil inductance. These requirements can be met with an amplifier running from +/-25 V voltage supplies dissipating about 20 watts, nominally.

The composite vertical deflection signal is shown in Fig. 1. It comprises a ramp waveform, running at field rate (about 60 Hz) plus a superimposed, parabolic, pincushion correction signal, having its fundamental at line rate (about 20 kHz). The spectrum of this signal is shown in Fig. 2.

Fig. 3 shows a two-channel amplifier in which the output signal from operational amplifier 1 is split by a crossover filter constituted by inductors 2 and 3 and capacitors 4 and 5 and operating in the unused band of the signal spectrum. The split signals are fed to a high-band amplifier 6 and a low-band amplifier 7. The outputs of the amplifiers are recombined by means of a matched crossover filter constituted by capacitor 8 and inductor 9. Negative f...