Randy James Gass

US Patent:

20100123990, May 20, 2010

Filed:

Nov 14, 2008

Appl. No.:

12/270997

Inventors:

Randy Gass - Cedar Rapids IA, US
Issa Drame - Cedar Rapids IA, US

Assignee:

SQUARE D COMPANY - Palatine IL

International Classification:

H02H 3/00

US Classification:

361 98, 361 94

Abstract:

A circuit breaker capable of microcontroller-based fault detection having a backup circuit for causing the circuit breaker to trip in response to a microcontroller fault, including a timing circuit powered by a power supply and a microcontroller. The timing circuit is electrically coupled to an SCR that causes the circuit breaker to trip. The timing circuit includes a BJT coupled to the gate of the SCR. The microcontroller has a first output coupled to the timing circuit and a second output coupled to the SCR. The first output is coupled to a node between a resistor and a grounded capacitor in the timing circuit, and the node is coupled to a gate of the SCR and to a base of the transistor. A voltage develops at the node sufficient to cause the gate of the SCR to turn on unless the microcontroller pulls the first high-impedance output to a logic low state.