Date: 03/02/2009

Reference design for 255 watt ATX PC power supply

Wondering how to get the ready circuit diagram built out of latest semiconductor devices, which can be used to produce ATX switching power supply for a PC. ON Semiconductor has addressed this need by announcing reference design for this purpose.
ON Semiconductor has released a new switch mode power supply (SMPS) reference design for ATX power supplies used to power desktop computers. This 255 watt version exceeds 80 PLUS Silver, ENERGY STAR 5.0, and Climate Savers Computing Initiative Step 3 efficiency standards for desktop PC power supply.
The new reference design offers better power efficiency under real world operating conditions, and can be deployed immediately for production.

Some of the features of the reference design are:

1. Achieving a maximum efficiency of 90 percent at 50 percent load with input voltage of 230 to 240 Vac, and achieves greater than 88 percent efficiency at 50 percent load with input voltage of 100 to 115 Vac.
2. The 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.
3. 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.
4. 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.

Key products in the reference design include:

1. NCP1654 Continuous Conduction Mode (CCM) Power Factor Controller: This device enables the inclusion of a PFC front-end into an ATX power supply. The NCP1654 is priced at $0.66 in 2,500-unit quantities, in SOIC-8 packages.
2. 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. The NCP1396 is priced at $0.85 in 2,500-unit quantities, in SOIC-8 packages.
3. NCP1027 65 kHz PWM Controller featuring 700 V MOSFET: Adjustable ramp compensation feature allows deep CCM operation. Skip mode operation optimizes light load efficiency. The NCP1027 is priced at $0.97 per unit in 1,000-unit quantities, in PDIP-7 packages.
4. NCP4302 Synchronous Rectification Controller: Integrated Secondary Side Controller simplifies the implementation of synchronous rectification in switchmode power supplies. In addition to the SR control, the device incorporates an accurate shunt regulator with TL431 functionality, reducing board space and system cost. The NCP4302 is priced at $0.74 per unit in 2,500-unit quantities, in SOIC-8 packages.
5. NCP1587 Synchronous Buck Controller: Built in non-overlap timing control prevents cross conduction of rectification MOSFETs. The NCP1587 is priced at $0.33 per unit in 2,500-unit quantities, in SOIC-8 packages.
6. MBR20L45 L-Series, 20 A, 45 V, Dual Schottky Rectifier: Low forward voltage drop minimizes power loss. The MBR20L45 is priced at $0.60 per unit in 50-unit quantities, in TO-220 packages.
7. NTD4809N Single N-Channel, 30 V, 58 A, Power MOSFET: The NTD4809N is priced at $0.19 per unit in 2,500-unit quantities, in DPAK and IPAK packages.

Demonstrations: ON Semiconductor will demonstrate the reference design at APEC in Washington, D.C., February 16-18, and IIC in Shenzhen, China, February 26-27.

For more information, visit http://www.onsemi.com