Patent ID: 7208887
Filing Date: 2007-04-24
Classification: H05B,Y10S

Abstract:
1. A ballast for a gas discharge lamp comprising: a first circuit portion for providing power to the lamp, the first circuit portion adapted to receive power from an AC main supply for conversion to a form suitable to supply power to the lamp; a second circuit portion for processing data exchanged with a communication link, the second circuit portion having a power supply supplied from the AC main supply, the power supply coupled at the input of the AC main supply to the first circuit portion; a first protection circuit coupled in series with the AC main supply for protecting the first and second circuit portions in the event of an electrical circuit failure leading to an overcurrent condition, the power supply for the second circuit portion being coupled such that it is protected by the first protection circuit; and a second protection circuit disposed in series with the first circuit portion and providing protection only in the event of an electrical failure leading to an overcurrent condition in the first circuit portion, the second protection circuit being adapted such that in the event of an electrical failure in the first circuit portion, the second protection circuit will discontinue the supply of current to the first circuit portion so as to prevent an overcurrent in the first protection circuit that would cause the first protection circuit to interrupt current; thereby allowing the first protection circuit to continue to supply current to the second circuit portion; wherein the second circuit portion further comprises a sensor input portion adapted to receive a sensor input provided from an external sensor, and wherein the second circuit portion includes a communication port for exchanging data with a communications link, and wherein, in the event of an electrical failure in the first circuit portion leading to operation of the second protection circuit, the second circuit portion is adapted to continue receiving power from the power supply, thereby allowing the sensor input to be exchanged with the communication link.