Simple Setup for Characterization of Voltage Dependent Capacitors at High-Voltage DC Bias

The voltage dependency of capacitors can be significant for the design of EMC filters, DC link structures and similar. In power electronics, knowing the change of capacitance over wide biasing ranges up to kV is of high importance. Several academic works are available describing self-built biasing structures (bias tee) for high voltage and/or current DC bias during impedance measurement, but often enough such works cannot be easily and quickly replicated. This paper describes the use of a commercially available 1000 V bias tee for capacitance extraction using a vector network analyzer (VNA). Necessary procedures, like setup calibration, are described in detail and the accuracy of the approach is analyzed. The device under test is a Ceralink ceramic capacitor. A thin film capacitor with no voltage dependency is used as reference.