Patent ID: 7368883

Claim:
An apparatus for fluorescent lamp comprising: a power source producing an alternating voltage with two terminals; a fluorescent lamp with filaments fitted to its first and second terminal pairs and these lamp terminal pairs are coupled to said terminals of said power source; a first voltage source coupled to said lamp first terminal pair and drives a current through said filament fitted to this first terminal pair; a second voltage source coupled to said lamp second terminal pair which drives a current through said filament fitted to this second terminal pair; a transformer having at least three windings magnetically coupled together, a first winding coupled in series with said first voltage source which detects current flow through this first voltage source, a second winding coupled in series with said second voltage source which detects current through this second voltage source, a third winding with two terminals, whereby these three windings are magnetically coupled and constructed in a way such that said third winding produces a current related to difference between the current in said second winding and the current in said first winding; a signal conditioning circuit coupled to terminals of said third winding of said transformer which accepts current in this third winding and produces a command signal which inhibits said power source when current in this third winding exceeds a preset level.