Magnetically-controlled electronic ballasts with isolated output: The variable transformer solution

New advances on magnetically-controlled electronic ballasts can grant the ability to dim the lamp and simultaneously guarantee output electrical isolation. By means of a variable transformer, whose model is presented, this new technique is developed and experimentally verified. In addition, a simple method for the large signal characterization of the transformer is described. A FH 14W/840 Osram lamp was chosen to validate this new technique and experimental results clearly show its adequate behaviour.