US 5,714,842 A · Automatic cutoff control for a DC coupled CRT video drive

Abstract

The present invention, generally speaking, provides for automatic cutoff control in a DC coupled CRT video drive using a low DC supply voltage and circuitry that is lower in power consumption than conventional circuitry for the comparable video performance. A simple, easy to implement solution is achieved with an extremely low component count. Cutoff control response is fast, allowing discontinuous operation of auto cutoff control. In one embodiment of the invention, a cutoff control signal is applied to individual CRT G1 terminals. Fast response cutoff control drive is realized using an IC current source and a single transistor current-to-voltage (CTV) converter. Supply voltage variations on the video driver are clamped via a clamping device to the negative supply voltage of the G1 CTV converter.

Claims7

Dependent claims

Apparatus comprising:

a video amplifier connected to a first voltage source for producing a video out-put signal;
DC coupling means for, during operation, applying said video output signal to a cathode of a CRT;
bias means connected to a second voltage source for producing a negative voltage;
means for, during operation, applying said negative voltage to a cutoff-control grid of a CRT;
and
regulating means, including a zener diode, connected between said bias means and said first voltage source for causing variations in said first voltage source to be reflected in a level of said negative voltage so as to reduce beam current variations during operation of said CRT.

3 more elements

Dependencies are inferred from the claim text.

Automatic cutoff control for a DC coupled CRT video drive

Life of this patent

Automatic cutoff control for a DC coupled CRT video drive

Life of this patent

Abstract

Claims7