DN05032/D - 24 Vin, 40 Watt, Low Cost, DC-to-DC Converter Design Note

DN05032/D, Design Note describes a very simple, low cost, yet high performance dc-to-dc converter using NCP1251B current mode controller (TSOP6 package) and the NCP431 programmable zener (SOT23 package). The 65 kHz flyback converter design operates in discontinuous conduction mode (DCM) and uses the conventional optocoupler (U2) feedback scheme for the voltage loop. Vcc for the NCP1251 current mode controller is derived directly from the dc input voltage via D2 and R1. The Design Note provides the complete circuit and transformer design details for a 12 volt, 3 amp output version. Other output voltages from 3.3 up to 28 Vdc are easy to implement by modifying the values (or ratings) of R8, R11, R12, C9, D5 and T1 secondary turns