A ballast in which the drive current frequency is controlled by a voltage-controlled oscillator (VCO) that is capable of precise output frequency control. The VCO frequency is controlled by a microcontroller. The microcontroller may control the VCO frequency in response to various input signals including...http://www.google.es/patents/US7199530?utm_source=gb-gplus-sharePatente US7199530 - Digital ballast
