I want to design an AC/DC converter
Output :10W minimum , Voltage can be 12V
Noise Level close to -155dBm/Hz
Board Area should be as small as possible.
can somebody suggest me a good part number to begin with.??
I was considering UCC28610, some evaluatioon boards i ve seen in TI website.
Ive checked the test results of these but none of them mentions about the Conducted Emission test results..Is it available somewhere else,,or these designs focus only on efficiency & not on noise (may be im wrong here)?
Can somebody advice me on selecting a proper device for this application.
Als o I've some basic doubts regarding the UCC28610,
I'm only familiar with flyback topology , so i read about a little bit n got the idea that this converter minimizes the loss by employing valley switching in the primary side with variable frequency & synchronous rectification in the secondary side..
Ive not completely understood the valley switching, what i understand that the converter will switch only when the Vds (or Ids) is minimum thus reducing losses..Can some body help me by pointing out any simple document that a beginner could easily understand .. ( ive checked many in the net..but most are confusing with the waveforms)since i vent been clear with this ..i cant understand the term quasi resonant specified in the datasheet...
Also i did a little search about the Green Mode..I believe its a technology helping to decrease the no load or light load dissipation..
Thanks for any help,
Unfortunately we don't really have the expertise to design an effective EMI input filter for our EVMs. And as EMI compliance is so dependent upon the final layout and specific omponents used in the particular application, knowing that customers will tend to adapt the layout to conform to their individual requirements, it just hasn't been justified (yet) for our EVMs to meet EMI standards. Perhaps this will change in the near future (hopefully) but at this moment the time and effort that would be needed has not been justified.
Quasi-resonant converters help mitigate conducted and radiated noise by switching at the resonant valley which softens the switching action due to the lower voltage switching. Hunting for the valley results in cycle to cycle dithering which spreads out the frequency spectrum. Instead of concentrating the excess energy at a narrow frequency, this same amount of energy is distributed over a wider range. Here's an article that may be helpful: http://www.electronicscomponentsworld.com/articleview~idarticle~71880_357274102102007.html
Quasi-resonant descrbes the soft switching action that results when the converter uses the annoying ringing that is generated by the primary inductance and the parasitic capacitance during the dead time. If the converter can detect when the ringing hits a valley and switches then, the 1/2 Coss x Vds^2 losses are substantially minimzed because the Vds voltage is at its low point...and this is the term that is squared. Its really minimized if the converter is designed to switch at the very first valley as this one is the deepest (the ringing dampens out over subsequent cycles)
Green mode is indeed for light load and no load efficiency. When the controller detects a light load, the switching occurs in bursts of pulses that are at a fixed frequency. The number of pulses in a burst packet increases as the load increases until switching is constant (the long intervals between the pulse packets gets filled in)
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