Floating Voltage Sensing Based on Ceramic Capacitor Ferroelectric Derating

Abstract

This paper presents methods allowing to provide galvanically isolated DC voltage measurement with nearly infinite input impedance. Measurement is based on a ferroelectric effect, creating hysteretic capacitance vs. bias-voltage (C-V) dependence of the ordinary multilayer ceramic capacitors. Voltage measurement is based on AC impedance sensing of a high-density multilayer ceramic capacitor and comparing with ground-referred matched capacitor with corresponding DC bias voltage. Corresponding DC bias voltage is provided by negative impedance converter and a feedback network. Despite finite accuracy (~1%), voltage sensing performed by a capacitor can be advantageous as it allows to implement AC (high-voltage) coupling, and presents nearly ideal infinite input impedance. This can be beneficial in a variety of applications e.g. in power management systems, energy harvesting applications, or scientific instrumentation.