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Fixed frequency controller targets AC/DC adaptor apps

Posted: 04 Mar 2010     Print Version  Bookmark and Share

Keywords:adapter  controller  fixed-frequency 

ON Semiconductor debuts a range of fixed-frequency, current-mode controller ICs, the NCP1237, NCP1238 and NCP1288 which are available in a choice of frequency options with single or dual level over current thresholds. The standard device has a built-in 65kHz oscillator, with 100kHz and 133kHz versions supplied on request.

They are targeted at AC-DC adapter applications for laptop/notebook computers, LCD displays, printers, and household consumer electronics.

The proprietary Soft−Ski mode utilised by these ICs ramp the peak current gradually during skip mode, reducing the risk of audible noise. This allows additional component savings, along with easing the design and manufacture of the transformer. Combining this with a frequency fold-back function, the new controllers deliver high efficiency levels in light load conditions, while minimising input power during no load conditions.

The Dynamic Self−Supply (DSS) function of the NCP1237 and NCP1238 provide an integrated start-up current source that intelligently handles start-up and line transient events. This simplifies the design of the auxiliary supply, reducing the size of the VCC capacitor. To minimise external component count, the controllers integrate brown-out, over-power compensation and ramp compensation, allowing a compact solution to be designed.

The new fixed-frequency, current-mode controller ICs have an operational temperature range of −40 °C to +125 °C and are offered in a compact SOIC-7 package.

"With utility bills continuing to increase and concerns about the environment growing, it is vital to use electrical power at the greatest possible rates of efficiency," said Christophe Warin, AC-DC business unit manager at ON Semiconductor. "The NCP1237, NCP1238 and NCP1288 are highly integrated solutions that will allow engineers to develop power system designs that maintain strong reliability, have a low bill-of-materials and do not waste energy when the product is in standby mode."

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