System for the power control of high voltage electron beam generators

System for the power control of high voltage electron beam generators comprising a directly heated cathode and a control electrode associated with the cathode, said system having high voltage isolation transformer means with primary and secondary winding for supplying the control electrode with a control voltage, means preceding the isolation transformer means on the primary side for the generation of square wave pulses symmetrical with the null line, means responsive to the comparison of the actual beam current and a reference value for amplitude modulating the square wave pulses, said isolation transformer means being provided with a tertiary winding on the primary side, said primary winding receiving input from the output of amplifier means having one input connected with the output voltage of the tertiary winding and another input receptive of the modulated square wave pulses and rectifier bridge means connected across the secondary winding.