Circuit to provide protection against burning of the fluorescent layer of a visual display unit

摘要

The protection circuit always protects the fluorescent layer of a visual display unit against burning when the image spot on the screen does not move within a specific time. For this purpose, the brightness signal (h) is passed through an attenuating element (S) before it is passed to the display device of the visual display unit, which attenuating element (S) can be controlled by the output signal (q) from a comparator (KV) which monitors the level of a signal m which is formed from the two deflection signals X(t) and Y(t) using the formula m = (Vx<2> + Vy<2>)<1/2> where Vx = dX/dt and Vy = dY/dt, in a computer (R). <IMAGE>