A leading global supplier of power management solutions, ON Semiconductor unveiled a GreenPoint reference design for CRT-TV power supplies that delivers standby power of less than 1 W. This energy efficient 160 W reference design addresses all functional blocks of the power supply and meets international regulations for low standby power dissipation.
"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. ON Semiconductor plans to continue to deliver 'green' solutions that ease the design burden on our customers for power supplies that are more and more efficient."
The Reference Design
To achieve breakthrough performance, the new CRT-TV GreenPoint reference design utilizes 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 newly introduced NCP1337, an enhanced Pulse Width Modulation (PWM) 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 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 kilohertz (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, while adapter no load consumption can match the most strengthens requirements. 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 Over Voltage Protection on the Vcc. An internal 4.0 millisecond (ms) soft-start eliminates the traditional startup stress.
The NCP1337 is ideal use in power supplies in CRT-TVs, 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.
The device 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:
TL431 – a three-terminal programmable shunt regulator diode.
MC78L05 - an inexpensive, easy-to-use positive voltage regulator suitable for applications that require a regulated supply of up to 100 mA.
MUR420 and MUR460 – 200 volt (V) and 600 V 4 Amp (A) ultrafast SWITCHMODE™ power recitifiers.
BS108 - a 200 V 250 milliamps (mA) small signal, logic level MOSFET.
BC547 – an NPN silicon amplifier transistor.
A complete documentation package for the CRT-TV power supply is available - including description, schematic, bill-of-materials, Gerber images, and evaluation results. These materials are available at www.onsemi.com, as are the product specifications and other supporting information.
GreenPoint is ON Semiconductor’s family of high-efficiency power supply reference designs that meet existing or emerging energy efficiency standards. GreenPoint reference designs include ATX power supply, CRT-TV power supply and the soon-to-be debuted Flat Panel TV power supply. For documentation package for these designs visit www.onsemi.com and do a keyword search of "GreenPoint".
ON Semiconductor is a preferred supplier of power solutions to engineers, purchasing professionals, distributors and contract manufacturers in the computer, cell phone, portable devices, automotive and industrial markets.
For more information, please visit ON Semiconductor’s website at www.onsemi.com.
NCP1337 data sheet