IMPROVING THE FREQUENCY-RESPONSE OF CERAMIC DIELECTRICS FOR HIGH-POWER APPLICATIONS IN POWER ELECTRONIC CONVERTERS

High-voltage (1000 V) distributed and lumped ceramic capacitors are un der development for diverse applications in integrated power-electroni cs structures and systems for cost-efficient production. These applica tions range from systems involving new integrated packaging and manufa cturing technologies such as for de-de converters, to optimal power-co mponent designs such as in dissipative RCD turn-off snubber circuits f or high-power transistor or thyristor sv;itch protection. Their design requires an understanding of the interacting ferroelectric, grain-bou ndary, and space-charge mechanisms controlling the high-voltage and lo w-frequency response. This paper relates to an experimental and theore tical study of high-voltage (0 to 1000 VDC) acceptor-doped barium-tita nate BaTiO3 ceramic capacitors, for several possible uses in integrate d power-electronic converters with flat voltage and frequency response up to 1 MHz. The paper includes interpretations, based on experiment, of the inter-dependence of a) ferroelectric-grain, b) -compensation-i nsulator-compensation-semiconductor grain-boundary, and c) Debye space -charge contributions to capacitance, as functions of acceptor doping.