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ATX power supply reference design debuts

Posted: 22 Jun 2007 ?? ?Print Version ?Bookmark and Share

Keywords:Energy Star? ATX reference design? power supplies?

On Semiconductor says it has launched the industry's first open ATX reference design that meets the new Energy Star performance requirements for ATX power supplies used in desktop PCs, scheduled to take effect in July 2007. The reference design delivers efficiency that exceeds the Energy Star requirements under all specified load conditions and provides a blueprint for power supply manufacturers to bring highly efficient power supplies to market with readily available, cost-effective technology, said the company.

The 300W GreenPoint ATX reference design achieves full-load efficiency of 86.5 percent at high-line and 82.5 percent efficiency at 20 percent of load and low-line. This reduces power losses by approximately 50 percent, compared to typical power supplies on the market today that average 70 percent power efficiency, said ON Semiconductor. Moreover, the ATX reference design meets IEC61000-3-2 power factor requirements.

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. The design uses several of ON Semiconductor's newest power management devices.

Key products in the reference design include NCP1653, a compact continuous conduction mode (CCM) PFC controller packaged in Pb-free 8-lead SOIC and PDIP packages and NCP1562, an active-clamp PWM voltage-mode controller with a 5 percent duty cycle limit with a soft-stop to prevent the typical oscillations in the forward active-clamp topology. The device has a dual-mode overcurrent protection circuit that handles momentary and continuous overcurrent conditions differently. It's available in Pb-free 16-lead TSSOP and SOIC packages.

Also included in the reference design is the NCP1027 device offered in a Pb-free 8-pin PDIP package. This high-voltage switcher includes a power MOSFET together with a startup current source, all directly connected to the bulk capacitor. To prevent lethal runaway in low input voltage conditions, an adjustable brown-out circuitry blocks the activity until sufficient input level is reached.

Other devices included in the reference design are NCP4330, a synchronous post-regulator available in a Pb-free 8-pin SOIC package that replaces the mag-amp to provide higher efficiency in the output section of the ATX power supply and MSR860, an 8A, 600V power rectifier which features switchmode soft recovery housed in a Pb-free TO-220 package.

NCP1653 is priced at 80 cents each, NCP1562 is priced at $1.60 each and NCP4330 is priced at 60 cents each in quantities of 2,500. NCP1027 is priced at 97 cents each in quantities of 1,000 while MSR860 is priced at $1.07 each in 50-unit quantities.

- Gina Roos

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