It is a surface mount IC with 6 legs. It is hard to read the numbers on the package but it looks like X04ND. It should have something to do with driving an N channel FET(HFS13N65U). Circuit full wave rectifies line voltage and then chops it up via MOSFET and transformer. to produce 24 to 40 VDC. Thanks

 

Picture? Schematic? Six legs - could be an opto-isolator. Would need to know the manufacturer and look up their codes. But at best all one can do is guess at this point. Unless someone has experience with that part number.