U.S. Philips Corporation

U.S. Phillips Corporation

Henricus L Simons

Dirk J Teuling

Jozef J Hulshof

In the market, there is a tendency towards picture tubes with a super flat screen. Due to the flat screen, it is becoming increasingly difficult to meet the even tighter specification on North/South raster distortion (N/S distortion), the tighter specification being caused by a growing importance of text display and high resolution displays. A deflection correction circuit is provided which compensates for a N/S distortion by inducing a correction current (Icv) through a vertical deflection coil (Lv). The correction current (Icv) can be injected in the vertical deflection coil (Lv) via an injection transformer (Ti) coupled in series with the vertical deflection coil (Lv). The injection transformer (Ti) is driven via an output stage (3) by a waveform generator (1,2). The waveform generator (1,2) generates a voltage waveform (M) built up out of substantially straight line sections. The deflection coil (Lv) integrates the voltage waveform (M) into a current waveform (Icv) having substantially parabolic sections. Such an inexpensive and flexible deflection correction circuit can be used to compensate for top/bottom and/or seagull N/S distortion, or for correction of convergence distortions. The deflection correction circuit can be a discrete or an integrated circuit.

Deflection correction

In order to cause scan and/or fly-back voltages (Vsca, Vfly) supplied by a horizontal output stage (1) to vary at a desired rate during a change of state in a horizontal deflection circuit (1, 2, 4), a feedback circuit (4) is provided. This feedback circuit (4) processes the scan and/or fly-back voltages (Vsca, Vfly) to a control voltage (Vco) with which a duty cycle (dc) of a drive signal (Hdr) of a switching element (Tr) in the horizontal output stage (1) is influenced.

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Eindhoven, Netherlands

Henricus L Simons