REVIEW: Energy Star power supply reference design uses standard parts

Latest open reference design for 300 watt ATX power supplies reduces losses by 50 percent over existing solutions

INTEL DEVELOPER FORUM, BEIJING—ON Semiconductor unveils 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 this July. The new 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.

"ON Semiconductor has clearly demonstrated that it is both technologically possible and financially feasible to deploy highly efficient ATX power supplies to the market today," said Andrew Fanara, director of ENERGY STAR Product Development at the U.S Environmental Protection Agency. "The availability of this open reference design prior to the effective date of the new ENERGY STAR requirements for ATX power supplies has very positive implications for energy savings in the desktop PC market."

ON Semiconductor's 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 the typical power supplies on the market today that average 70 percent power efficiency. Additionally, ON Semiconductor's ATX reference design meets IEC61000-3-2 power factor requirements.

"ON Semiconductor's 300 W GreenPoint ATX reference design demonstrates our unwavering commitment to deliver innovative, turn-key power solutions for extremely efficient power supplies," said Andy Williams, senior vice president and general manager of ON Semiconductor's Automotive and Power Regulation Group. "We worked closely with worldwide regulatory organizations and our customers to develop this cost-effective ENERGY STAR compliant power supply solution. ON Semiconductor will continue to introduce additional GreenPoint power solutions addressing the global need for power efficiency in both active and standby modes.

The ATX Reference Design

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 utilizes several of ON Semiconductor's newest power management devices and draws from its leading discrete component portfolio to achieve superior efficiency performance.

ON Semiconductor has a complete documentation package for the ATX reference design, including description, schematics, bill-of-materials, Gerber files and evaluation guidelines. The documentation package is available at www.onsemi.com/ATX, as are links to relevant industry information and other supporting information.

Key products in the reference design include:

NCP1653: This compact continuous conduction mode (CCM) power factor correction (PFC) controller makes the choice of incorporating a PFC front-end into an ATX design easy, by reducing part count and providing a robust, cost-effective front-end without range switches. Offered in Pb-free 8-lead SOIC and PDIP packages, the NCP1653 is priced at $0.80 USD in 2,500-unit quantities.

NCP1562: This active-clamp pulse width modulation (PWM) voltage-mode controller has a +/-5% duty cycle limit with a soft-stop to prevent the typical oscillations in the forward active-clamp topology. The device has a dual-mode over-current protection circuit that handles momentary and continuous over-current conditions differently. Offered in Pb-free 16-lead TSSOP and SOIC packages, the NCP1562 is priced at $1.60 USD per unit in 2,500-unit quantities.

NCP1027: 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. Offered in a Pb-free 8-pin PDIP package, the NCP1027 is priced at $0.97 USD per unit in 1,000-unit quantities.

NCP4330: This synchronous post-regulator replaces the mag-amp to provide higher efficiency in the output section of the ATX power supply. Offered in a Pb-free 8-pin SOIC package, the NCP4330 is priced at $0.60 USD per unit in 2,500-unit quantities.

MSR860: This 8 amp (A), 600 V power rectifier features SWITCHMODE soft recovery. Offered in a Pb-free TO-220 package, the MSR860 is priced at $1.07 USD per unit in 50-unit quantities.

For more information, visit http://www.onsemi.com or contact Kelvin Tsiang at Kelvin.Tsiang@onsemi.com.

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