This reference document describes a built--and--tested, GreenPoint® solution for a 40 W (40 W nominal power, 50 W peak power) set--top box (STB) power supply. This document presents the results of various secondary rectification and regulation techniques thatwere used to find the highest practical efficiency scheme for a four--output, 40 watt set top box power supply. The power supply design is built around ON Semiconductor’s NCP1308 Current--Mode controller, on the primary side, using free running quasi--resonance operation. The secondary side offers four outputs (+5 V, --5 V, 3.3 V and 12 V). The +5 V output is the main channel with the closed PWMloop while the 3.3 Voutput is derived by using the NCP1587 in a buck (step--down) DC--DC topology with synchronous rectification. The 12Voutput is derived from+5 V by stacking the 12 V secondary winding onto the 5 V winding.