News Center

ON Semiconductor Delivers Latest GreenPoint™ ATX Reference Design that Exceeds 80 PLUS® Silver Efficiency Standards for Desktop Computers

Latest open reference design for 255 watt ATX power supplies achieves 85 percent efficiency for broad range of real world operating conditions

ON Semiconductor, a leading global supplier of high performance, energy efficient, silicon solutions today released its latest open reference design for ATX power supplies. This 255 watt (W) version exceeds 80 PLUS Silver, ENERGY STARR 5.0, and Climate SaversR Computing Initiative Step 3 efficiency standards for desktop PC power supplies. The new 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 percent at 50 percent load, and at 230 and 240 Vac, ON Semiconductor's reference design achieves greater than 88 percent efficiency at 50 percent load, and 100 and 115 Vac. Efficiency is greater than 85 percent at 20 percent and 100 percent loads, with 100, 115, 230, or 240 Vac. All efficiency measurements were obtained at the end of a 41 cm (16 in) cable, ensuring the design can be used ‘as is' in all standard desktop PC configurations. Additionally, ON Semiconductor's ATX reference design meets IEC 61000-3-2 power factor requirements for power factor greater than 0.95 at 100, 115, 230, and 240 Vac.
"Our customers have indicated that while efficiency standards are important, real-world operating conditions - such as extended input voltage range and practical cable length - are equally important to actually deploy power supplies in end equipment," said Bill Schromm, senior vice president and general manager of ON Semiconductor's Computing and Consumer Group.  "In addition to ensuring compliance with the relevant global efficiency standards, we also addressed the real-world operating conditions that challenge our customers in their designs."

"ON Semiconductor has steadily increased the performance of its ATX reference designs, since it became the first semiconductor company to achieve an 80 PLUS certified open reference design in 2005", said Jason Boehlke, channel manager for Ecos Consulting and the 80 PLUS program. "The latest reference design from ON Semiconductor achieved the 80 PLUS Silver performance levels in a configuration that can be readily installed in production of desktop PCs." 

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, schematic s, bill-of-materials, Gerber files, and evaluation guidelines. The documentation package is available at, as are links to relevant industry information and other supporting information.

Key products in the reference design include:
  • NCP1654 Continuous Conduction Mode (CCM) Power Factor Controller: Ideal solution for CCM PFC applications, such as ATX power supplies. This device enables the inclusion of a PFC front-end into an ATX power supply by simplifying the design through integration and providing a robust, cost-effective front-end without range switches.
  • NCP1396 Resonant Mode Controller with High and Low Side Drivers: Integrated resonant tank solution, i.e., the leakage inductance of transformer acts as resonant inductance.  
  • NCP1027 65 kHz PWM Controller featuring 700 V MOSFET: Adjustable ramp compensation feature allows deep CCM operation, optimizing efficiency at full load. Skip mode operation optimizes light load efficiency. 
  • NCP4302 Synchronous Rectification Controller: Highly Integrated Secondary Side Controller simplifies the implementation of synchronous rectification (SR) in switchmode power supplies, improving the overall system efficiency by 2 percent to 4 percent. In addition to the SR control, the device incorporates an accurate shunt regulator with TL431 functionality, reducing board space and system cost. 
  • NCP1587 Synchronous Buck Controller: Built in non-overlap timing control prevents cross conduction of rectification MOSFETs. 
  • MBR20L45 L-Series, 20 A, 45 V, Dual Schottky Rectifier: Low forward voltage drop minimizes power loss. 
  • NTD4809N Single N-Channel, 30 V, 58 A, Power MOSFET: Low RDS(ON) minimizes conduction losses; low capacitance minimizes driver losses; optimized gate charge minimizes switching losses.