Abstract: A focus voltage correction circuit for cathode ray tubes is disclosed in which a flyback pulse is generated by switching a supply voltage to be applied to a primary side of a flyback transformer, and the flyback pulse being is rectified and smoothed so as to develop a focus voltage in cathode ray tubes. A correction voltage capable of minimizing an error in the focus voltage to be caused by an error in the supply voltage is superimposed on the flyback pulse. In addition, the focus voltage correction circuit for cathode ray tubes may be provided with a device for regulating the correction voltage such that the focus voltage regulation can be performed.

Abstract: A voltage supply circuit for cathode ray tubes in which a horizontal drive pulse is supplied to a flyback transformer and a flyback pulse to be derived from the flyback transformer is supplied as a cathode voltage, a grid voltage and an anode voltage for a cathode ray tube, to provide a focus voltage regulation circuit for cathode ray tubes is disclosed wherein the flyback pulse to be derived from a part of the flyback transformer is rectified to obtain a direct current voltage which is in turn varied for application as a cathode voltage and/or a grid voltage or superimpose onto the anode voltage so that a potential difference between the cathode voltage, the grid voltage and the anode voltage is variably and relatively regulated.