1. Field of the Invention
This invention relates to a DC high voltage supply system designed to supply a highly efficient and stable DC voltage to a load by providing a high voltage transformer circuit with a feedback control circuit, which transformer circuit is made up, in combination, of a variable magnetic leak transformer (VLT) driven under resonant conditions and a capacitor type multiple boosting circuit, and by controlling the current of the control winding of the VLT by the feedback control circuit.
2. Prior Art
In recent years a combination of a boosting transformer and a capacitor type multiple boosting circuit represented by a Cockcroft-Walton circuit has been in wide use so as to reduce the size and weight of a DC power source unit used for supplying DC high voltage power to an X-ray diagnostic apparatus, an electron microscope, sputtering apparatus and which constitutes a greater part of the volume and weight of both the boosting transformer and the multiple boosting circuit instead of the conventional method in which commercial frequency is boosted by a high voltage transformer and is then rectified.
But according to this combined use of the transformer and the circuit, it often happened that, viewed from the principle of the capacitor type multiple boosting circuit, the diodes used in the capacitor type multiple boosting circuit are damaged by the surge current generated during a sudden increase in load or during initial charging of the capacitor multiple boosting circuit.
Also, it is possible to think of using the capacitor type multiple boosting circuit by connecting large resistors in series with load for preventing the surge current generated in this case; but this way of tackling the problem causes a decrease in voltage regulation and an increase in power loss, with the result that efficiency of the system is greatly reduced.
Furthermore, slowing charging is also employed by providing a soft start circuit for preventing surge current when the power is on but it inevitably results in increased cost of the system because of the circuit being complicated.