Design and Create SMPS trans

Hello
i want to design and create a transformer that Pout should be equal 75wat.i have EI2520 core and wire with these diameter
.15 , .10 , .20


i use Current PWM IC and a MOsfet for switching. i want to have a voltage 18V-4A output my frequency is undefined because i can have a frequency between 29Khz to 200Khz
input voltage after rectifier is 320 volt

how can i do that?

I assume this is an offline design.

i can have a frequency between 29Khz to 200Khz

Click to expand...

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?

---------- Post added at 17:06 ---------- Previous post was at 17:03 ----------

Check this link:
**broken link removed**

Hello dear Tahmid
Yep, i want to create a Fix PWM frequency with UC3842 and a flyback converter. until now i only design the pwm circuit and rectified my input voltage and find the peak voltage with Capacitor and diode circuit.min voltage of rectified voltage is 308 to 326 volt.I want to have a 18V-4A output so i use Tl431 and an optocoupler.so could you tell me more in designing?

i want to know how can i find the frequency that my circuit need?calculation of wiring a transformer?

Frequency selection is usually an estimate. You choose a frequency where the gains will be greater than the losses. This could be in the range of 30kHz to 100kHz. Around 50kHz is a good start. Although, depending on the quality of parts used, 100kHz or more could provide more gains.

But you can start with 50kHz.

Wait some time and I'll provide more details.

Thank you very much
i have a question about this sentence

"For the european mains of 230V +/-10% and behind the rectifier and the smoothing (with a voltage ripple of 10%) the input voltage range is between Vin_min = 250V and Vin_max = 360V."

how it say Vin_min = 250V and Vin_max = 360V?

i calculate my input with this statues
input voltage can be 220 to 230 the the dc voltage can be Min=220*1.414 and Max=230*1.414

Thanks

It states +/- 10%. 10% of 230V is 23V.

So, the minimum DC voltage will be (230-23)*√2 = 293V. The maximum DC voltage will be (230+23)*√2 = 358V. So, the range is 293V to 358V.

360VDC is when input voltage is (360/√2) = 255VAC
250VDC is when input voltage is (250/√2) = 177VAC

So, probably the converter was designed for use with mains voltage between 177VAC and 250VAC.

Hope this helps.
Tahmid.