after all your valuable help i decided to go with LM3404HV for controlling brightness by my UNO ...
but i need your help again.. 
i have read that data sheets of LM3404hv
first one was manual and second one was Evaluation Board...
in Evaluation board paper a table and schematic and its parts was presented and of course a part for changing current ... in addition i found a online calculator for that ic ...But the problem is parts i found in that calculator is totally different from what i saw in evaluation paper...
as you know i have a string of 10*1w led
Vf = 3.5
I = 300mA
i planned to buy a new voltage supply 48V 1A...
please help me for right pars and design..
again thanks to all