In one embodiment, an isolated power converter can include: (i) a transformer having a primary winding and a secondary winding; (ii) a secondary rectifier circuit coupled to the secondary winding; (iii) a power switch coupled between an input voltage source and a first terminal of the primary winding, where a second terminal of the primary winding is coupled to ground; (iv) a feedback circuit coupled between the first and second terminals of the primary winding, the feedback circuit being configured to generate a feedback voltage based on a voltage across the primary winding; (v) a control circuit configured to generate a control signal to control the power switch; and (vi) an over voltage protection circuit configured to activate a reset signal when the voltage feedback signal is greater than a threshold value, where the reset signal is configured to reset the control signal when activated.