Design an ultra-wide input range, logic-bias power supply
This power supply is a 12 volt, 12 watt nominal output, wide range AC input supply designed around the NCP1271 current mode controller in a DCM flyback topology. It is intended for low power logic bias applications (up to 15 watts) in industrial equipment. The circuit includes current limiting, an input EMI filter, a simple resistor (R1) inrush limiter, and optocoupled voltage feedback using a simple TL431 programmable zener error amplifier (U3). The dc bulk input capacitor (C3) is rated to manage continuous operation at 40 Vac input, yet handle the high dc bulk voltage when operated at 300 Vac. An input EMI composed of C1, C2, L1 and C8 is also included.