Slope compensation for NCP1239 Flyback controller

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cupoftea

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Hi,
For the NCP1239 offline flyback controller, from the block diagram of the NCP1239 datasheet on page 4, it appears that the slope compensation acts on the error voltage, and so it is not necessary to make the current sense resistors lower in value so as to "make room" for the slope compensation?

(In other words, (and supposing the "over power protection" [OPP] feature is not used) the sense resistor should literally be

Peak Primary current at Max load, Minimum Vin / 0.8V
?

NCP1239 datasheet
 

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slope comp implies CCM at 45% on time or greater - this is a great way to make a noisy power supply.

Sticking to DCM or CrCM requires no slope comp, and gives a far quieter power supply
 
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Thanks, yes indeed, though our customer has pre purchased many thousands of transformers, which we must use, and we will be in CCM at USA mains.
Indeed we dont have to reduce sense resistor value as slope comp is subbed from the error voltage.
 

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