Abstract: A CRT protective circuit capable of eliminating spots during a mode conversion operation includes a microprocessor for generating a mute signal according to externally-provided horizontal and vertical sync signals, and a high voltage generating section for generating a high voltage according to an operation of a flyback transformer. A first switching section is switched according to the mute signal for supplying the high voltage of the high voltage generating section to a grid terminal, and a high voltage dropping section divides the output voltage of the high voltage generating section according to the switching status of the first switching section and supplies the dividing voltage to the grid terminal to control brightness of the spots.

Abstract: A spot removing circuit for a display device is disclosed. The spot removing circuit comprises a rectifying and smoothing portion for rectifying and smoothing the voltage outputted from a flyback transformer, a capacitor for charging a voltage supplied from a power supply and discharging the charged voltage when the power supply switch is turned off, and a grid control portion for supplying a grid terminal with the voltage outputted from the rectifying and smoothing portion when a power supply switch is turned on and for supplying the grid terminal with the voltage discharged from the capacitor plus the output voltage from the rectifying and smoothing portion when the power supply switch is turned off so that a spot can be prevented from appearing on a display screen when the power supply switch of the display device is turned off.