An isolated flyback converter for an LED driver includes a snubber circuit unit connected to the primary side of a transformer; and a snubber voltage detection unit which detects a snubber voltage of the snubber circuit unit and generates a reference voltage proportional to the detected snubber voltage. The textural promoter may be a high-surface area, high-porosity, stable metal oxide support. The crown axial groove is provided in the groove bottom with a tie bar rising therefrom and connecting the circumferentially adjacent two crown blocks each other. A molded body surrounds at least a portion of the leadframe and the dies. An inward shoulder portion is disposed on the inward wall portion. An alternate method comprises applying the porous polymer film without plasma treatment and heat curing the film to form a proper bond.