Specifics of the X7R capacitors application in the high frequency inverters

Abstract

The high energy density X7R multilayer ceramic capacitors are widely used in the power electronic circuitries. Those capacitors are characterized by high nominal capacitance, voltage and low equivalent series resistance ESR. The latter may become critical in case of the high current, high frequency application and may cause a temperature rise significantly exceeding one estimated using ESR value from the datasheet. This behavior may be traced to the induced piezoelectric effect and resulting electromechanical resonances and losses. This article presents test results correcting X7R capacitance dependency on the bias voltage and multiple resonance dependency of ESR on the frequency and DC bias which may be useful for mitigating the excessive heating of the capacitors.