A Novel Aluminum Electrolytic Capacitor Suitable for High-frequency Power Converters

Abstract

Aluminum electrolytic capacitors have high capacitance and high volumetric efficiency. Electrolytic capacitors with high rated voltage (> 300 V), however, show large reduction of capacitance in high frequency regions, which is attributable to the long tunnel pit structure of anode foils. To demonstrate the effect of the structure, equivalent circuit simulations focusing on voltage transient phenomena concerning the tunnel pit length were performed. In addition, effective capacitance measurements under current pulse operation were carried out with prototype capacitors with different tunnel length. The test results demonstrated the feasibility of a new concept electrolytic capacitor for high frequency applications. The new concept can provide an advantage in helping in downsizing and increment of ripple current capability at high frequency. The performance of the proposed capacitors utilizing an anode foil with appropriate structure was evaluated. As a result of the high frequency ripple current operation tests, it was found that approximately 30% increase in ripple current capability at high frequency when the capacitor size is held constant, and approximately 25% reduction in capacitor volume when high-frequency capacitance and ripple current capability are held constant can be achieved.