Patent ID: 7915896

Claim:
A method to identify a defective filament in a fluorescent lamp in a circuit, the method comprising: supplying a voltage to a circuit including one or more fluorescent lamps and an anti-parallel transformer, each fluorescent lamp including two filaments, a primary side of the transformer operatively coupled to a first filament and a secondary side of the transformer operatively coupled to a second filament, the first filament and the second filament drawing a first current flowing through the primary side of the transformer and a second current flowing through the secondary side of the transformer, respectively; monitoring a resistance of the transformer, the resistance being below a threshold as long as the first filament and the second filament are present in the circuit which causes the first current and the second current, respectively, to flow through the primary side and the secondary side of the transformer, respectively; and upon determining that the resistance increases above the threshold, identifying that either the first filament or the second filament is absent from the circuit.