Lamp dimmers are disclosed in which, in the course of varying average power supplied to the lamp load, the semiconductor power control devices transition between one and the other of substantially conductive and non-conductive power conditions, the duration of the transition by the ...http://www.google.de/patents/US5672941?utm_source=gb-gplus-sharePatent US5672941 - Inductorless controlled transition light dimmers optimizing output waveforms 
