1. Field of the Invention
This invention relates to a circuit arrangement for producing high voltages by means of a voltage multiplier, e.g. of the Cockcroft-Walton type, that is fed from an alternating current source.
2. Description of the Related Technology
It is known per se to provide high-voltages e.g. for discharge tubes, including X-ray tubes, by means of voltage multipliers of the kind concerned.
In the case of X-ray tubes it is generally desired to earth the anode because this makes it easier to obtain the necessary dispersion of heat from the anode. In order to avoid extremely high potentials in relation to earth, it is a frequently chosen solution, however, to supply the anode and cathode of the X-ray tube from high-voltage sources of opposite polarities each at half of the full anode-cathode voltage of the tube.
In either case, the filament of the tube will attain a high voltage relative to earth and due to the fact that the magnitude of the filament current determining the intensity of the X-radiation shall, moreover, generally be adjustable, certain difficulties arise, in particular as regards fulfilment of the demands for insulation, whereby the means for supplying and controlling the filament current become excessively voluminous and heavy, meaning a considerable increase of the total volume and weight of the X-ray tube. This is particularly inadvantageous in case of mobile X-ray devices for radiological tests of materials.
This applies also to other parts of the tube, e.g. a bias grid, the voltage of which deviates by only a small amount from the cathode voltage of the tube.
Similar problems occur also in other devices than X-ray tubes, which are supplied from a circuit arrangement of the type in question, and where it is desirable to produce small amplitude voltages lying at the voltage level of the high voltage.