what basics should i have to understand the content of this video ?

I have some math basics but when those are tied to real time applications things get too deep and confusing.

what level of maths or what type of maths should I learn and also what branch of electronics should I master in order to understand this video ?

I guess You need no special grades in Math to understand the function.
But You have to need some experiences with inductors.
In this video are only declared the basics.
There is nothing about core saturation and power losses by the core and the windings.
One importent fact was not sayed explicid:
The maximum duty cycle primary only can be 50%, otherwise the core go into saturation.
And You have to use a suitable core material.

In princip he said You'll store the input power into the magnetic field of the core.
When the magnetic field break down at opening the primary switch, it generate an output current at the secondary side of the Transformer. That's it.

In real Flyback converters the Output voltage would be supervised and steers the Duty cycle at the primary winding.
That works with an Opto Coupler or an seperate winding with diode and capacitator.
Because the load of a real power supply is mostly not constant.
So the duty cycle at the primary had to be changed.

In actual fly back converter circuits would be used IC's for steering the primary side switching transistor.
At lower power applications the switch could be included into the IC.
There is included a start up circuit for soft startup and some security features too.

wkrug said:

I guess You need no special grades in Math to understand the function.
But You have to need some experiences with inductors.

Click to expand...

Thanks mate.

Can you list a good book to get acquainted with switch mode inductors ?

The basic principle is the same for any inductor.
(Even just wire rather than a coil, though that only usually has any significant effect at extremely high frequencies).

When you apply power to an inductor - any type, a solenoid or relay coil as well as a transformer etc. - it takes time for the current to build up and a magnetic field is formed around the coil.

If you disconnect the supply to the inductor, the current tries to continue flowing as the magnetic field collapses.
That can cause an extremely high [reverse] voltage to be produced across the inductor, if there is no circuit path to carry it.
Edit - found an example waveform of an inductor switch off: https://s19539.pcdn.co/wp-content/uploads/2017/04/voltage.jpg

In many cases it's a nuisance - with a relay or solenoid switched by a transistor, the voltage spike can destroy the transistor; or with a switching contact, it causes arcing and burning.
A "flywheel diode" or snubber circuit is normally used to allow the stored energy to be dissipated safely.

With a switching power supply, the stored energy can be routed to where it is needed, either from a single inductor or a second winding on an inductor, as with a transformer secondary winding.

This is the simplest circuit I can find: https://encrypted-tbn0.gstatic.com/...xNy8UtPHLozJ1Z3Xe9i2HaryAlZ82EvTPBzDuHA2SGKTj

The IC switches pulses of power through the inductor. When the IC output switches off, the current in the inductor tries to maintain and the left hand side goes negative relative to ground, so the current passes through the diode and adds some charge to the capacitor each time.

This gives more details of the operation using a similar circuit (a different IC in the same family) and some of the maths involved: