A persistent problem in X-ray high voltage generators is the protocol for operating and protecting the filaments of very expensive X-ray tubes. In general, the operating current of the X-ray tube, and hence the quantity of X-ray flux generated, is controlled by the temperature of the tube filament. The higher the temperature, the more electrons are available for acceleration by the high voltage potential between the cathode and anode of the X-ray tube. The quantity of electrons per second is equivalent to the tube current as measured in milliamperes.
The filament temperature is controlled by varying the current supplied to the filament, generally measured in amperes. The higher the current, the higher the temperature and the more X-rays are produced.
Complicating the issue is the fact that the cathode and filament are usually at a very high negative potential with respect to ground potential, where the control electronics are located. This requires some sort of isolation through which the power to the filament is supplied. In the present invention this isolation is provided by a specially designed filament transformer.