Confusion about SMPS wire gauge

I am designing 12W SMPS using NCP1014AP06.

Input- 230VAC ± 15%, 50 Hz
Peak Input current through primary - 410 mA
Primary turns - 418
Primary inductance - 9.55 mH

Secondary turns - 38
Output - 24 V, 0.5 A
PWM frequency - 65 KHz
Duty cycle - 67%
Core selected - EE 19/8/5 (for small size)

Which wire size should I use??
Should I STRICTLY follow the wire size data as per https://www.powerstream.com/Wire_Size.htm ???

According to this data the wire size for primary is AWG 25 & for secondary is AWG 24. If these wire sizes are chosen I need to use bigger core. I have size limitation for the core.

The application note of Fairchild indicates the core size & power requirements. The app. note is attached with other documents.

Can there be any compromise with core size & wire size?????????????????

Please, Help...

You apparently selected wire gauge for the primary winding based on peak current. That's completely wrong. RMS current is the quantity defining the required gauge. It's also not appropriate to calculate wire gauge independent of the core size. You better use a transformer calculator tool, e.g. MDT from EPCOS/TDK, or the values from a trustworthy reference design.

Re: Confusion About SMPS wire gauge

you need to calculate your rms current in the windings and see if its giving too much i^2.R dissipation.
Remember skin effect, though with a flyback of 10w you should be ok with a single wire primary.

treez said:

you need to calculate your rms current in the windings and see if its giving too much i^2.R dissipation.
Remember skin effect, though with a flyback of 10w you should be ok with a single wire primary.

Click to expand...

FvM said:

You apparently selected wire gauge for the primary winding based on peak current. That's completely wrong. RMS current is the quantity defining the required gauge. It's also not appropriate to calculate wire gauge independent of the core size. You better use a transformer calculator tool, e.g. MDT from EPCOS/TDK, or the values from a trustworthy reference design.

Click to expand...

Calculated RMS current is 171 mA.

How to determine the flux density in ferrite core for primary turns calculation in flyback transformer if (flux density) not mentioned in the datasheet??

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Should we choose around 250 mT approximately??

it depends on the ferrite material, but flybacks often go up to 300mT.
rEMEMBER TO GET the graphs on the ferrite datasheet so you can see power loss vs peak to peak flux deviation....at whatever your frequency is....so you can calculate the core loss.