Zenith Electronics Corporation

Zenith Radio Corporation

Lloyd E Matthews

Philip J Nowaczyk

Gregory J Beaumont

A compensation circuit for maintainng a CRT vertical raster size substantially constant with beam current changes includes a sensing resistor connected in series with the high voltage winding. The sensing resistor develops an input bias for a compensation transistor that has its output circuit connected across the vertical size control. Increases in beam current are reflected in increases in current in the high voltage winding which cause the compensation transistor to conduct more heavily and supply more current to the vertical size control. The size control is part of the discharge circuit of the vertical timing capacitor and the increased current from the transistor reduces the discharge time of the timing capacitor. Consequently the peak to peak voltage of the vertical current ramp is decreased.

Beam current compensated vertical size control

A regulator for compensating for the IR drop of a rectifier coupled between the secondary winding of a transformer and a load circuit includes a pass transistor connected between the load circuit and the rectifier. A DC reference voltage is developed by a circuit connected across the secondary winding that is not subject to current fluctuations. A differential amplifier is supplied with the reference voltage as one input and the load voltage as another input. The output of the differential amplifier controls the conductivity of the pass transistor. A current limiting transistor is included in the base circuit of the pass transistor and, in turn, is controlled by another differential amplifier supplied with potentials representative of the IR drop across the rectifier. A shut down transistor is provided for cutting of the pass transistor in the event the load circuit voltage drops below a predetermined level.

Regulator with rectifier IR drop compensation

Disclosed is a vertical drive circuit for a cathode ray tube in a video display in which sawtooth current waveform corrections for the deflection yoke are made by means of an S-correction feedback loop featuring DC-coupling and low frequency filtering. The amplified correction signal is transmitted to a push-pull type output stage for driving the deflection yoke. Power consumption is reduced and operation made more efficient by an approximate doubling of the retrace voltage applied to the push-pull output stage during retrace by means of a discharging capacitor network.

Vertical drive circuit for video display

Disclosed is an SCR-analogue, dual coupled transistor vertical oscillator for synching the vertical sweep in a video display with vertical synchronization input signals. Capable of stable, free-running oscillation at two, variable DC levels, the coupled transistor configuration in combination with a capacitor generates a precisely defined sawtooth voltage waveform for controlling vertical sweep and flyback. This combination provides an inexpensive, flexible means for synchronizing sweep drive circuitry operating at various DC coupled levels with a wide range of synchronization input signals.

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Berwyn, IL, United States of America

Lloyd E Matthews