ON Semiconductor has unveiled a GreenPoint reference design for CRT-TV power supplies that consumes standby power of under a watt.
This energy-efficient 160 W reference design addresses all functional blocks of the power supply and meets international regulations for low standby power dissipation, says the company.
"We developed, built and fully tested this CRT-TV power supply reference design to further demonstrate ON Semiconductor's ability to help deliver industry-leading power efficient consumer products to the market," said Andy Williams, vice president of ON Semiconductor's Power Conversion Division. "When developing this design - and all our GreenPoint power solutions - we worked closely with our worldwide customers to assure the creation of effective solutions that directly address present and future power needs. We plan to continue to deliver 'green' solutions that ease the design burden on our customers for power supplies that are more and more efficient."
Reference design
To achieve the breakthrough performance, the CRT-TV GreenPoint reference design utilises a number of ON Semiconductor's advanced power management devices and draws from the company's industry-leading discrete component portfolio.
The enabling device for the reference design is the company's newly-introduced NCP1337, an enhanced PWM (pulse width modulation) current-mode controller that eases the design of free running quasi-resonant power supplies such as those found in CRT-TVs. It combines a true current-mode modulator and a demagnetisation 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 the compliance with EMI conducted emission standards, the lowest limit being 150 kHz.
By monitoring the feedback pin activity, this controller enters ripple mode as soon as the power demand falls below a pre-determined level. The standby power of a 160 W CRT TV can be reduced to less than 1 W. Because restart is softened by an internal soft-start and the frequency cannot fall below 25 kHz, no audible noise is emitted.
The NCP1337 features an efficient protective circuitry that, in the presence of an overcurrent 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 known as 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 an overvoltage protection on the VCC. An internal 4 ms soft-start eliminates the traditional startup stress.
The NCP1337 comes in both SOIC-7 and PDIP-7 package, and is ideal for use in CRT-TV power supplies, notebook AC-DC adapters, offline battery chargers, other consumer electronics such as DVD players and set-top boxes, and any power supply where efficiency and low EMI signature are needed.
GreenPoint reference designs are available at www.onsemi.com for a CRT-TV power supply, an ATX power supply, an LCD-TV power supply and a notebook adapter.
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