Relay circuit

• US 20070268640A1
• Filed: 05/16/2007
• Published: 11/22/2007
• Est. Priority Date: 05/16/2006
• Status: Active Grant

• Current Assignee: Penny and Giles Controls Limited (Curtiss-Wright Corporation)
• Original Assignee: PG Drives Technology Incorporated
• Inventors: Brereton, Richard Peter, Hamilton, Duncan, Rees, Daniel Robert
• Granted Patent: US 7,593,198 B2
• Time in Patent Office: Days
• US Class Current: 361/62
• CPC Class Codes: A61G 5/04 motor-driven A61G5/06 takes precedence; motor-operated rests A61G5/12; for vehicles with handlebars, equipped with three or more wheels B62K5/003, B62K5/023
• CPC Class Codes: H02H 7/222 for switches

Abstract

A switching circuit for connecting a power source to a load is described. The circuit comprises a first relay and at least one second relay in parallel arrangement with the first relay. The switching circuit is arranged such that in the event of a fault condition occurring that requires the disconnection of the power source from the load, the at least one second relay opens while the first relay remains closed. In this manner, a reliable disconnection of the load from the switching circuit is achieved.

Claims

1. A switching circuit for connecting a power source to a load, the circuit comprising a first relay and at least one second relay in parallel arrangement with said first relay, the switching circuit arranged such that in the event of a fault condition occurring that requires the disconnection of the power source from the load, said at least one second relay opens while the first relay remains closed.

2. A switching circuit as claimed in claim 1, wherein said at least one second relay opens before the first relay.

3. A switching circuit as claimed in claim 2, wherein a current sensitive circuit breaker is placed in series arrangement with said first relay, such that if said first relay does not open, said current sensitive circuit breaker can open the circuit.

4. A switching circuit as claimed in claim 1, wherein said circuit further comprises a timing circuit to open said at least one second relay before said first relay.

5. A switching circuit as claimed in claim 3, wherein said current sensitive circuit breaker comprises a fuse.

6. A switching circuit as claimed in claim 1, wherein said first and second relays comprise respective coils that are powered using a pulse width modulated signal.

7. A switching circuit as claimed in claim 1, said circuit further comprising a capacitor that is charged before said first relay closes, in order to reduce the voltage drop across said first relay to prevent arcing.

8. A switching circuit as claimed in claim 7, wherein said capacitor is charged using a pre-charge circuit.

9. A switching circuit as claimed in claim 6, wherein said timing circuit comprises a first diode and a second diode, wherein the first diode is connected across the coil of said at least one second relay to the power source, and the second diode is connected across the coil of said first relay, to ensure that said at least one second relay opens before said first relay.

10. A powered vehicle controller comprising a switching circuit as claimed in claim 1.

11. A method of isolating an electrical load from a power source using a switching circuit arranged between the power source and the load, the switching circuit comprising a first relay and at least one second relay in parallel arrangement with said first relay, said method comprising the steps of opening said at least one second relay while said first relay remains closed, in the event of a fault condition occurring.

12. A method of isolating an electrical load as claimed in claim 11, wherein said method comprises causing a current sensitive circuit breaker arranged in series arrangement with said first relay, to open in the event that said first relay does not open.