The present disclosure is directed to a high power factor quasi resonant converter. The converter converts an AC power line input to a DC output to power a load, generally a string of LEDs. The power input is fed into a transformer being controlled by a power switch. The power switch is driven by a controller having a shaping circuit. The shaping circuit uses a current generator, switched resistor and capacitor to produce a sinusoidal reference voltage signal. The controller drives the power switch based on the voltage reference signal, resulting in a sinusoidal input current in a primary winding of the transformer, resulting in high power factor and low total harmonic distortion for the converter.