I googled MHJ+TSSOP and most results pointed in the direction of a switching voltage regulator, so I wasn't surprised at your reply. But that's about as specific as I can be.
All the results were almost exclusively on Chinese websites. Your SMPS is it "made in China"?
I don't know if it was made in China or not. It's probably a good guess.
I Googled the same thing and see the "MHJ" in the part number on many Chinese sites. But I didn't see "MHJ" as the top mark. So I'm no closer. Did you see something I didn't?
How can I find a seemingly random IC from the top mark? Between NXP's and Fairchild's websites, and a couple other top mark listing sites, I can often figure out discrete components. But as for ICs... what to do?
Perhaps the part marked "252" is an IC which is why I'm having trouble IDing it??