The NCL30085 is an AC-DC power factor corrected flyback controller targeting isolated and non−isolated buck-boost/SEPIC constant current LED drivers. The controller operates in a quasi−resonant mode to provide optimal efficiency. Thanks to a novel control method, the device is able to tightly regulate a constant LED current from the primary side. This removes the need for secondary side feedback circuitry, biasing and an optocoupler. The device is highly integrated with a minimum number of external components. A robust suite of safety protection is built in to simplify the design. This controller has integrated 3 step log dimming which allows an LED bulb or luminaire to be dimming from a standard wall switch.In addition to steps of 70% and 25% which are similar to a traditional 3 way lamp, one additional step of 5% current is included to support deep dimming applications.