onsemi Power Supply Demonstration Evaluation Board Flyback Converter for NCP1251BSN100T1G for Power Supply Demonstration

This evaluation board is a very simple, low cost, yet high performance off-line flyback power supply using ON Semiconductor's NCP1251B controller (TSOP6 package), NDD04N60 D-Pak Mosfet, and the NCP431 programmable zener (SOT23 package). The flyback design operates in discontinuous conduction mode and uses the conventional optocoupler (U2) feedback scheme for the voltage loop and an auxiliary Vcc winding on the flyback transformer to power the NCP1251. The Design Note provides the complete circuit and transformer design details for 5 volt, 4 amp, and 12 volt, 1.8 amp output models.