Other Parts Discussed in Thread: UCC28019A,
Hi Everybody,
I am designing a bias supply by UCC28722 which is supplied with a DC voltage ( of a pfc converter using UCC28019A controller ).
The supply voltage is 390 VDC typically which is from 380 to 400 VDC and has a 23.4 V peak to peak ripple. ( ie the minimum voltage equals 380-23.4/2 V ~ 368VDC )
I use the provided excel calculator SLUC529.
In the row 35, the primary peak current of the transformer is calculated by:
Ippk=Pout*2/(Eff*(Vinmin*SQRT(2)*0.6)*Dmax)
I modified the above equation to the bellow one ( to adapt the minimum input voltage ):
=Pout*2/(Eff*(Vinmin*SQRT(2)-Vrip/2)*Dmax) ---> Pout=5W, Eff=0.75, Vinmin= 269VAC ( 380 VDC ), Vrip=23.4, Dmax=0.495
Which results in 73.1 mA peak to peak.
And then the Lpm=31.2 mH.
Also the Nps~77.
Now please consider the TIDA-00355 reference design which is very similar to my application.
The transformer used in the the design is a Lpm=4mH and Nps=10.
Although the tow applications are very similar the designs differ considerably.
Is my design correct and optimum?
Why the reference design differs to my one?
Regards, Ras