CRT driving circuit

Abstract

A CRT driving circuit includes a cathode control circuit for controlling a cathode voltage of a CRT on the basis of a video signal created by a video circuit, a power supply circuit for creating a power supply voltage for each of the cathode control circuit and the video circuit, a switch circuit provided between the power supply circuit and the cathode control circuit, and a monitor control circuit for on/off controlling the switch circuit and the power supply circuit on the basis of a power-on/off externally inputted signal. In response to the power-on/off signal, when the monitor control circuit switches the switch circuit and the power supply circuit into an off-state, it turns off the power supply circuit later than the switch circuit. Even after a power-switch is turned off, the video signal is supplied to the cathode control circuit so that the cathode control circuit continues its on-state. Thus, the charges left in the CRT while the power-switch is turned off are discharged through the cathode control circuit in the on-state.

Dependencies are inferred from the claim text.