Floating Voltage Sensing Based on Ceramic Capacitor Ferroelectric Derating

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.