By "line filter" I meant a series inductance followed by some shunt capacitance, which will filter off the 25kHz PWM signal from the driver.
It's possible that the leakage inductance of the transformer may effectively act as the inductor, so simply adding a capacitor on the secondary side would complete the filter. Depends greatly on the specific transformer though, caution is advised.
Also you will need to be careful that the duty cycle on the two half bridges is balanced very precisely, otherwise you will end up dumping lots of DC current into the primary.