Help me understand how to control a flyback converter

hi fiends
i am confusing in controling of a flyback converter.my aknowledge about it is low and i have to learn it in one week,i want your help,if possible
best regards

please help me!

what is flyback converter ?can you tell me?what is fountion on it?

Re: please help me!

You could get a book. A good one is: A. I. Pressman "Switching Power Supply Design".
You can try going to the TI website and look for the Unitrode Seminars.
You can also ask me whenever you do not understand something.

Re: please help me!

dear VVV
i am reading pressman,and after your guidance i reffered to IT...,but still i cant undersatand control circuits(voltage-mode? current-mode? compensation circuit?)
in this field this references could not help me.what is your idea in this condition?
in addition i did not any knowledge in flyback and switching power supply but proviously your guidance helped me very much,
THANKS you in advance.

Re: please help me!

Control circuits actually adjust the duty-cycle to maintain the output constant.
The easiest to unerstand is the voltage-mode. Basically you have a reference voltage and you compare the output voltage (divided down with a resistive divider) to that reference. So, for example, if your reference is 5V you could use a divider with a ratio of 2.4:1 to get a 12V output.

The comparison is done by the so-called error amplifier. This is simply a high-gain differential amplifier, which has the reference connected to one of its inputs and the output voltage divider to the other input. The difference beteen the two voltages is amplified and it actually controls the PWM duty-cycle. So you see, when the difference is zero, the output equals your desired value and the duty-cycle is maintained at the level that produces that output.
Should the output increase or decrease, the error amplifier would amplifiy the difference (or error, as it is called) and adjust the duty-cycle accordingly, to bring the output back into regulation.

Try to understand this and then we will talk about current-mode.

please help me!

I will suggest you get this book it will help a lot

Switching Power Supply Design (Second Edition)
http://www.elektrotekno.com/about16356.html

contact me if you need any other ifomation
cheers