Current measuring system with earthing detector - includes differential amplifier with positive and negative feedback loops and current measuring resistor in negative loop

摘要

The current detector circuit is designed to detect an abrupt change in voltage distribution, such as may occur during a short circuit to earth. The key component is a differential amplifier with positive feedback and with negative feedback through a current measuring resistor. The latter, and the load impedance may be either on the earth or the reference potential side of the negative feedback path. The current measuring resistor is connected in parallel with a series circuit comprising a second resistor and the emitter-collector path of a transistor. The current measuring resistor may also be connected into a current mirror circuit.