GROUND FAULT DETECTION BASED ON CAPACITIVE SENSING

摘要

A ground fault detection system based on capacitive sensing suitable for use in detecting a ground fault condition in electronic equipment (such as a PCBA) with a circuit ground electrically isolated from an isolation ground (such as chassis ground). The capacitive sensing system includes a capacitive sensor capacitively coupled to the system isolation ground, and a capacitance/data converter that captures sensor capacitance measurements for conversion to sensor data representative of a ground short. In one embodiment, the capacitive sensor includes a sensor electrode capacitively coupled to the system isolation ground by one of projected capacitance and a floating capacitor (such as 33 pf), and the CDC unit further includes sensor excitation circuitry configured to drive the sensor electrode, such that a sensor capacitance (projected or floating capacitance) is representative of an electrical condition of the system isolation ground. For sensing by projected capacitance, the capacitive sensor can include a driven shield.

主权项

1. A ground fault detection system based on capacitive sensing, suitable for use in detecting a ground fault condition in electronic equipment including a circuit ground electrically isolated from an isolation ground, where the ground fault condition occurs when the circuit ground shorts to the system isolation ground, comprising:
a capacitive sensor capacitively coupled to the system isolation ground, such that a sensor capacitance of the sensor capacitor is representative of an electrical condition of the system isolation ground; and a capacitance-to-data conversion (CDC) unit coupled to the capacitive sensor, and referenced to the circuit ground, and configured to capture sensor capacitance measurements for conversion into corresponding sensor data, including:
capacitance acquisition circuitry configured to acquire measurements of sensor capacitance for the sensor electrode; anddata conversion circuitry configured to convert the sensor capacitance into sensor data representative of the electrical condition of the system isolation ground, including an isolated condition in which the circuit ground is isolated from the system isolation ground, and a ground fault condition in which the circuit ground shorts to the system isolation ground.