Magnetically-controlled dimming technique with isolated output

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, the model of which is presented, this new technique is developed and experimentally verified. In addition, a simple method for the large signal characterisation of the transformer is described. An FH 14W/840 Osram lamp was chosen to validate this new technique and experimental results clearly show its adequate behaviour.