An AC-DC converter, power supply board and display apparatus is disclosed. The AC-DC converter comprises: an AC-DC converting circuit; a transformer, whose primary coil has a first terminal coupled to a positive output terminal of the AC-DC converting circuit, and second terminal connected to a load; a voltage monitoring circuit, whose input terminal is coupled to the first terminal of the secondary coil, and second terminal of the secondary coil connected to a ground; and a control circuit, whose input terminal is coupled to an output terminal of the voltage monitoring circuit, and output terminal coupled to the AC-DC converting circuit; wherein the voltage monitoring circuit outputs a control voltage when a voltage outputted by the first terminal of the secondary coil of the transformer exceeds a first threshold; the control circuit controls the AC-DC converting circuit to stop providing power supply when the control voltage exceeds a second threshold.