Means for controlling the electric current density of a high tension direct current source

Claim 1

A current regulated with high voltage power supply, comprising: a transformer having a low voltage primary winding and a high voltage secondary winding: a current sampling circuit coupled to said secondary winding for providing a first D.C. voltage dependent upon the current flowing through said secondary winding: rectifying and filtering means for coupling said secondary winding to a high voltage load: means for comparing said first voltage with a reference voltage to produce a current control signal at a control terminal thereof which varies in accordance with the difference between said first and reference voltages; a transistor oscillator having at least one power supply terminal and including a resonant circuit having inductive and capacitive elements, the primary winding of said transformer comprising the inductive element of said resonant circuit, said oscillator including a transistor amplifier having an output terminal DC coupled to said resonant circuit and an input terminal coupled to said resonant circuit via a feedback capacitor connected between said input terminal and said power supply terminal, the current through said primary and secondary windings being dependent upon the amplitude of oscillations developed by said oscillator; and a variable transistor power supply circuit including a variable impedance control transistor having two main electrodes coupled in series between a fixed voltage supply terminal and said power supply terminal and a control electrode coupled to said control terminal for varying the supply voltage to said oscillator in accordance with said current control signal to thereby vary the amplitude of said oscillations so as to maintain the current flowing through said secondary winding at a desired value.