Phoenix, Ariz.—ON Semiconductor's fifth GreenPoint reference design, for 60-watt power adapters used for LCD TVs, monitors, and notebooks, addresses the often tedious challenges inherent in meeting standby and active mode energy efficiency regulations for a wide range of consumer applications.
"The new 60 watt power adapter reference design joins our previously announced 90 watt GreenPoint notebook adapter design...to address applications where high efficiency and adapter size are crucial at an optimal cost," said Andy Williams, senior vice president of the Automotive and Power Supply Group.
The blueprint addresses all functional blocks of the power adapter and achieves low standby power and compliance with CEC, Energy Star and European Code of Conduct (COC) requirements. It delivers 88 percent energy efficiency. It further conserves energy in standby mode—the mode in which power adapters typically spend the most time—standby current is less than 250 milliwatts. That level represents a improvement over competing designs by a factor of three, according to the company.
The enabling device for the reference design is the new NCP1337, an enhanced PWM current-mode controller. It combines a true current-mode modulator and a demagnetization detector that ensures full borderline/critical conduction mode in any load/line. The device eliminates the need for an external signal by providing internal transformer core reset detection. Frequency is internally limited to 130 kHz to facilitate compliance with EMI conducted emission standards, the lowest limit being 150 kHz.
The NCP1337 enters ripple mode as soon as the power demand falls below a pre-determined level. Because restart is softened by an internal soft-start and the frequency cannot fall below 25 kHz, there is no audible noise. The controller features an efficient protective circuitry that, in the presence of an over-current condition, disables the output pulses and enters a safe burst mode when trying to restart. Once the default has gone, the device auto-recovers and the power supply resume operation.
Additional features include a bulk voltage monitoring function for brown-out protection, an adjustable overpower compensation that tackles the effect of the input voltage variation on the maximum power a quasi-resonance PSU can deliver, and over-voltage protection. Internal soft-start circuitry eliminates stress on components during start-up.
The NCP1337 is offered in both an SOIC-7 and a PDIP-7 package and priced at $1.04 per unit in 2,500 unit quantities. Supporting devices include the TL431A programmable precision reference, NTP75N06 75-amp, 60-volt MOSFET, MBR160 1-amp, 60-volt Schottky rectifier, 1N4937 1-amp, 600-volt fast-recovery rectifier,
MMSZ13 and MMSZ15 500-mW Zener diodes, MMSD4148 switching diode, and MMBT3904L and MMBT3906L general purpose transistors.
A complete documentation package for the 60-W power adapter is available—including description, block diagram, schematic, bill-of-materials, Gerber images, and evaluation results. To acquire documentation packages, visit the company website and run a keyword search on "GreenPoint."
ON Semiconductor, 1-602-244-6600, www.onsemi.com