I assume this is an offline design.
i can have a frequency between 29Khz to 200Khz
You're referring to a range of possible frequencies you want to try, right? You're going to have a fixed frequency during operating and try different frequencies. Isn't that right? Or do you intend to alter the frequency during the circuit operation on-the-fly?
You should keep in mind skin effect of the wires when you're winding the transformer. So, there knowing the frequency is important since skin effect depends on the frequency.
I also assume you're designing a flyback converter. Is that right?
You need to tell us more, like minimum input voltage, maximum input voltage, maximum duty cycle, etc.
In Marty Brown's "Power Supply Cookbook", all required calculation methods and formula are given. You should see if you can get hold of that book. I've found it to be an excellent book.
By the way, which controller are you using? Is it a UC384X?
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