Simple flyback power supply

[miler74]

Hi everyone,
I'm an electrical engineering student from Poland.
For one of my classes, I've been assigned to design a simple flyback power supply with the following parameters, and then run a simulation of it in LTspice.
Unfortunately, I'm not very experienced in this area of power electronics, and I'm struggling a bit.
Would anyone be willing to help or guide me through the process? I'd really appreciate any support!
Specs:
Input voltage: AC 230V ±20%
Output voltage:  DC 24V
Output power: 50W
Thanks in advance!

[Picuino]

You can start by making a schematic of the power supply and we will correct or help you with the details.

EDIT:
Start with an input voltage rectifier and a capacitor.
Then you will need to choose a transistor (best a mosfet) and a PWM controller (such as the UC3844).
https://www.ti.com/lit/an/slua143/slua143.pdf
https://www.ti.com/lit/ds/symlink/uc3844.pdf

On the transformer secondary (start with a 2:1 transformer ratio to begin with) a diode and a capacitor, followed by an optocoupler and a TL431 to control the output voltage. The optocoupler transistor must feed back into the PWM circuit.
You can also control the output of the secondary to feed the PWM controller circuit (this is less precise, but easier).

[Picuino]

An example flyback converter can be found in the datasheet or in the application notes of the PWM controller circuit.

Transformer:
   Primary: 48 turns
   5V secondary: 4 turns
   12V secondary: 9 turns

[Picuino]

Flyback example design from https://www.ti.com/lit/ds/symlink/uc3844.pdf

[BILLPOD]

Dzien dobry Miler,  Witamy 

[miler74]

Thanks for the quick reply, Picuino — it really helped clarify things for me.
I spoke with the professor who teaches the subject, and he instructed me to first design a real (non-ideal) transformer, then simulate it in LTspice. Based on the results of that simulation, I’m supposed to select the rest of the components. Unfortunately, I have to follow his guidelines strictly — otherwise, I won’t pass the subject.

Cześć BILPOD

[Picuino]

A real transformer is modeled with an ideal transformer with some added elements (resistors and uncoupled inductances in the primary and secondary).
You can also add resistors to model the core losses.

https://en.wikipedia.org/wiki/Transformer#Equivalent_circuit

Did the professor give you some guidance on this?

[miler74]

Today I got some links from my professor that might come in handy:
http://schmidt-walter-schaltnetzteile.de/smps_e/spw_smps_e.html
http://schmidt-walter-schaltnetzteile.de/snt/snt_eng/snteng6a.pdf

[Picuino]

A simulation with a real transformer, in continuous conduction mode.

https://www.picuino.com/circuits/?ctz=CQAgjCBMCmC0AcIDMAGAdGJA2e37xzAE4ssQBWFCkAFiQrjDACgA3EeKpcyDqmxFX5dI5EEPFpyzAO59kPcDRoLeKNkpXdeYZVHzioUFCapixQjDWZhyRY4kiQVkFIm2H0EMKd+nZmvqIxLyQBupyulqKru6K6gAqDuBhUADsOqkq6CZqUiCwYGhIaSXYWGlpmLjwaTRwaVBoWGCQ3EgdrihEdWBk6ETwAbHgRKFuUM7iwxMh4FhUc+oAJvOLY2spjiDL0ABmAIYArgA2AC7MAMabrcELtILgaH4vvmANUDRpGLgoNG1MSo+ehgNLqABO4FaDyhmUeXRMAT6-GC0IE00iaMQnBhEVhWxuqTxI1uyXRxIm6ORuOGGVGvA6ZCWzFWkDpJGQ2BAHN4u0Opwu10Z3LIwqWkl8RCl0plsvszmKRCQ+BoJngY1ajWctLh6V4HIhtD6IqNTI2i0gATFGxoxuZcmFHNtZANOs2bJ05pmdyoJK9AHsoBAsNkQAAPeA+TDgSzw6iwUpB5CSMQJpDMQONJAM8ORlDRkNcNA6cCltPMIA