[SOLVED] want to convert CV smps to CC also

sir i am studying SMPS develop a smps with 12 v now want to convert it to 300 mA current. so i want to know what are the methods to do this operation. i tried it with BC 547 and 1 sense resister but as temp rises (resister) current decrease. help me please

Hello my friend
Can you give me more explanation about your clear purpose?
Best Wishes
Goldsmith

at output of smps i connect tl 431 for voltage regulation. now i want to add the circuit which will control the current flow. when load is more then it has to give same current but decrease the voltage

Again Hi
It is very simple. but it depends on your schematic. anywhere , you have two main way : 1- hiccup method. 2- off current . and hiccup is better way.
you should get some sample from current and compare it with a voltage ( current reference ) and then the result of this comparison , should cut your PWM signal.
For better help , you should attach your schematic.
Best Regards
Goldsmith

here is my schematic.

So as i understood , you are using a continuous fly back converter . at first step , for limiting , you can use current mode ICs , those have current limiters at the primary of the transformer . anywhere , you should use a series resistor , with your primary , and get the voltage across that and do comparing between that and a low value DC voltage , and when the voltage across the current sense resistor become higher than the current reference voltage , thus your comparator or opamp can give a positive voltage to you , that you can give this voltage to your feed back pin , thus , the IC , will think that the out put voltage is high and will try to cut the voltage . and with this fast action , the current will be constant ( at your desired current ) as well as .
Good luck
Goldsmith

but i dont want to use current limiter at primary side want to used it at secondary side

If you limit the current of primary , naturally the current of secondary will limit.
Respectfully
Goldsmith

---------- Post added at 16:16 ---------- Previous post was at 16:15 ----------

Don't forget the relationship between the primary current and secondary current.