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ON Semiconductor today introduced the GreenPoint(tm) reference design for CRT TV power supplies, which provides less than 1 watt (W) of standby power. This energy-efficient 160 W reference design addresses all functional blocks of the power supply and meets international low standby power specifications.

For breakthrough performance, the new CRT TV GreenPoint reference design features ON Semiconductor's advanced power management devices and the company's industry-leading line of discrete components.

The leading device in the reference design is the new NCP1337, an enhanced pulse width modulation (PWM) current mode controller designed to operate a free running quasi-resonant power supply, including CRT TV power supplies. It combines a true current mode modulator with a demagnetization detector to ensure a complete boundary/critical conduction mode on any load/line. The device provides internal demagnetization detection of the internal transformer core and does not require any external signals. The internal frequency limit is 130 kHz and is compliant with EMI conductive emission standards with a minimum limit of 150 kHz.

This controller enters the ripple mode by monitoring the feedback pin as long as the power requirement is lower than the preset level. The standby power consumption of the 160 W CRT TV is reduced to less than 1 W, and the no-load energy consumption of the adapter can meet the most stringent requirements. Since the restart is softened by the internal soft start, the frequency cannot be lower than 25 kHz, so there is no noise.

The NCP1337 also features an efficient protection circuit that, in the event of an overcurrent condition, attempts to restart, shuts down the output pulse and enters safe burst mode. Once the fault disappears, the device automatically recovers and the power supply resumes operation.

Other features include an overall voltage detection function called input brown-out protection. This is an adjustable overload compensation that can handle the effects of input voltage variations on the highest power provided by the quasi-resonant power supply, as well as overvoltage protection on Vcc. An internal 4 millisecond (ms) soft start eliminates the traditional starting stress.

The NCP1337 is suitable for use in CRT TVs, LCD TVs, PDP TVs, notebook AC-DC adapters, offline battery chargers, DVD players and set-top boxes, and other consumer electronics that require high energy efficiency and low EMI.

The device is available in SOIC-7 and PDIP-7 packages and is priced at $1.04 per unit in 2,500 units.

Other devices in the reference design include:

* TL431 - three-terminal programmable shunt regulator diode.
* MC78L05 - a low-cost, easy-to-use positive voltage regulator for applications requiring up to 100 milliamps (mA) of regulated power.
* MUR420 and MUR460 - 200 volt (V) and 600 V 4 amp (A) ultra-fast SWITCHMODE (tm) power rectifiers.
* BS108 - 200 V 250 mA small signal, logic level MOSFET.
* BC547 - NPN silicon amplifier transistor.

A complete documentation package for CRT TV power supplies including instructions, circuit diagrams, bill of materials, Gerber diagrams and evaluation results is available at with product specifications and other support information.

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