CONTROLLER derivation

Rakesh,

I would first suggest that the UC2854A is a better choise thatnthe UC2854. It limits the crossover distortion because teh the Iac pin voltage is near zero.

if you look at the design notes for the UC2854a you will see SLUS196A which you can use as a reference (also known as DN-66) I woul dalso make use of the UC3855a

http://www.ti.com/general/docs/lit/getliterature.tsp?literatureNumber=slua146a&fileType=pdf which goes through the design of the PFC power stage and a significant portionof th econverter but it does not have teh smae current monitoring mechanism so that portion is not directly usable. This is a complex design for this IC and it is not suggested for the inexperienced designer.

There are other designexamples in the UCC3817 that could help understnad teh subject but there are no directly applicable design examples for teh UC3854 and UC3854A ICs.

Regards,

John

I got these papers but in that paprer the design for current controller, one equation is their for gain gain= (Vo*Sense resistor)/(sL*Vpp) How this equation is derived in any where we can find this , i require the deivation and iam using 3854B  in my project.

Rakesh,

I'm not certain I can tell you where the best place is to get the definition r derivation for the formula but that same formula is in SLUA146A page 26 and shown being used on page 27 as they solve for the current gain at the desired current gain crossover point of 10 kHz withan effective current sense resitance of 0.1 ohm.

It is also in SEM1000 Which is attached to this response. This references a paper in SEM600 (1988) High Power Factor Preregulation for the Off-Line Power Supplies. (page 6-9) .  It also references SEM700 (1990) Optimizing the Design of the High Power factor Switching Preregulator which might also prove a good reference in your design work.

Regards,

John