Dear sanks
Hi
Why not an SMPS ? for example a simple flyback converter . ( in current mode topology ) . it's out put current can't exceed from authorized value .
BTW : what do you mean by constant current ? are you referring to a current source ? or just limited current ?
Best Wishes
Goldsmith
Do you know of the common trick of using a three-terminal voltage regulator as a constant current source?
The circuit, below, maintains its design voltage across the series R. By a suitable choice of the regulator's voltage and the value of R you can set the current to whatever you like up to the regulator's maximum value.