Design of Series Active Linear Filter for High-voltage Pulse Power Supply of Gyrotron Cathode

As the most reliable high-power terahertz source, the gyrotron requires a high stability of the operating frequency to fulfill the requirements of some scientific studies. The cathode voltage of the gyrotron is an important factor directly affecting the operating frequency. To enhance the poor ripple and accuracy of the high-voltage pulse power supply (HVPPS) currently in use, this paper proposes a series linear filter with high-voltage isolation based on the MOSFET. When operating in the active region, the MOSFET can be regarded as a variable resistor to compensate the ripple of HVPPS. Additionally, for precise control and high voltage isolation, the control system scheme with high-precision acquisition and control, cascade feedback strategy and fiber optic isolation is introduced. Furthermore, a small-signal model of the linear filter circuit is constructed and analyzed. Finally, the effectiveness of the linear filter circuit in voltage ripple suppression is verified by experimental results with a voltage ripple from 0.5% to 0.07% an accuracy from 0.4% to 0.015%, and great repeatability at 20 kV/0.5 A.