Probably the kind used for 220 VAC is too much for your aplication.
The reason is, we are talking about a power transformer, it is designed
to handle a lot of power and consequently it is bulky(big). But in essence
a balun is just a device which transform +V (referenced to ground) into
+V/2 and -V/2 referenced to a common point ( the center tap in the case
of transformer). It is just like transforming from single ended to
diferential (just another name for the same). It is just like differential
op-amp, the same concept.......