Patent ID: 8116056
Filing Date: 2012-02-14
Classification: H02H

Abstract:
1. A backup circuit in a circuit breaker capable of microcontroller-based fault detection, the backup circuit tripping the circuit breaker in response to the microcontroller being unresponsive, comprising: a power supply that produces a regulated direct current (DC) voltage derived from an alternating current (AC) line input to which the circuit breaker is connected; a timing circuit powered by the power supply and electrically coupled to an electronic switching device that causes the circuit breaker to trip in response to the electronic switching device being turned on; and a microcontroller having a first pin coupled to the timing circuit and a second pin coupled to the electronic switching device, wherein the first pin is configurable as a high-impedance input or as an output, wherein the first pin is coupled to a node between a resistor and a grounded capacitor in the timing circuit, the node being coupled to a gate of the electronic switching device, and wherein a voltage develops at the node sufficient to cause the gate of the electronic switching device to turn on unless the microcontroller pulls the first pin to a logic low output state.