TIDA-010062: switching freq

Hi team,

My customer have a few questions regarding the design:

1. Is it possible to increase the switching frequency of PFC/LLC to reduce magnetic components size? If yes, what could be the maximum frequency for both stages?
2. LLC stage is not very clear.

From design guide line, I read Lr = 19uH and Cr = 66nF

And I can estimate Lm using equation (16) to 300uH

This give approx Ln =  15.79 and Qe_fullload = 0.57, F0 = 140KHz

If I look at schematic, I read Lr = 13H, Lm = 200uH and Cr = 66nF

This give approx Ln =  15.38 and Qe_fullload = 0.47, F0 = 172KHz

If I draw the gain curve for both cases. It intersects only the Mg_min (=0.972) but never the Mg_max(=1.2)

              Is there anything wrong in my calculation?    

              Anyhow, transformer design cannot be the same.

              We need 54V output. Nps = 4?

              To minimize copper loss, I will prefer to go for a 4:1:1 structure, 4 primary turns. meaning a primary inductance in the range of 20~30uH

              This means to increase the switching frequency to 750Hz or more.

              Is that possible?

Thanks,

Connie