ON Semiconductor has designed an open reference design for ATX power supplies. This 255 W version exceeds 80 PLUS Silver, ENERGY STAR? 5.0 and Climate Savers? Computing Initiative Step 3 efficiency standards for desktop PC power supplies. The reference design delivers improved efficiency under real world operating conditions and in a configuration that allows it to be deployed immediately to production. The design provides a blueprint for power supply manufacturers to bring highly-efficient power supplies to market with readily available, cost-effective technology. Achieving a maximum efficiency of 90% at 50% load, and at 230 and 240 V AC, ON Semiconductor's reference design achieves >88% efficiency at 50% load, and 100 and 115 V AC. Efficiency is >85% at 20% and 100% loads with 100, 115, 230 or 240 V AC. The reference design addresses all functional blocks of the ATX power supply, including power factor correction, switch-mode power supply control and regulation, post regulation and standby power.