HIGH-VOLTAGE CAPACITOR VOLTAGE DIVIDER CIRCUIT HAVING A HIGH-VOLTAGE SILICON-ON-INSULATOR (SOI) CAPACITOR

摘要

A high-voltage capacitive voltage divider circuit includes a high-voltage Silicon-On-Insulator (SOI) capacitor connected between a high-voltage terminal and a low-voltage terminal, and a low-voltage SOI capacitor connected between the low-voltage terminal and a common terminal. The voltage divider circuit also includes control circuitry for processing a signal generated at the low-voltage terminal in order to provide voltage-related control of a larger circuit employing the voltage divider circuit. The high-voltage SOI capacitor can include an oxide layer on a substrate, with a thinned drift region on the oxide layer, a thick oxide layer over the thinned drift region, and an electrode layer over the thick oxide layer, with the electrode layer and the thinned drift region forming capacitor plates insulated from each other by the thick oxide layer. The capacitive voltage divider circuit may advantageously form part of a Switched Mode Power Supply (SMPS), in which the high-voltage terminal is an output of a diode bridge rectifier of the SMPS, and a comparator is used to sense a stepped-down voltage at the low-voltage terminal and uses this stepped-down voltage to detect an under-voltage condition in the SMPS.