How about Protect The Boss? I watched it after seeing Secret Love (not the same as Secret Love Affair) which is probably one of the heaviest dramas I've ever seen. I had originally dropped Protect The Boss a few months ago after two episodes (and it seems a lot of people have done that too... I don't really remember them but they must've been bad) but it turned out to be one of my favorite dramas! It's definitely a light drama, and the male lead falls crazy in love with the female lead, his secretary. I've rarely seen a character falling in love so fast and so completely in a drama. Even though it's a rom-com, it's everything but a stupid drama, though. All the characters are based on the typical rom-com stereotypes (the hard-working and poor female lead; the chaebol, the perfect handsome and sweet rival, the beautiful and horrible second female lead...) but this drama twists all these formulas - all the characters are extremely human and relatable, without falling into melo. I think a lot of people have problems with the female lead at the beginning, but after the two or three first episodes I realised she was perhaps the most clear-headed characters I had ever come across in a drama. It's romantic in a very real and honest way, and funny without being too silly!
About the two dramas mentioned above (MLFS and IHYV), even though they are two of my favorite dramas, it's true that they have very dramatic parts, and that's not what you're asking for. But the dramatic parts are well balanced with humour and romance (which makes the dramatic parts all the more intense!).
I also second Sungkyunkwan Scandal - the setting is great since it takes place in a university in the Joeseon era. A girl has to disguise herself as a boy since women aren't allowed, and she makes friends, and love complicates it all... The portrayal of the friendship between the 4 main characters in this drama is unforgettable and one of the best I've ever seen, but I must admit the friendship part may be more interesting than the love aspect - there certainly is chemistry between the 2 main leads, but only one kiss? pffff :( It's still one of my top dramas though :)
I also agree with Rooftop Prince - a lot of great humor (probably the funniest of all these dramas), and the romance is good, though in my opinion not as good as the previous ones.
Good luck!
