The NCL30188 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 device is specifically intended for very compact,space efficient designs.