The subject application provides a power converter with lossless current sensing capability. The power converter comprises: a transformer, a primary switch for conducting or blocking a current flowing in a primary winding of the transformer, a controller configured to generate a first control signal through a first control node to control the primary switch; and a current sensing circuit configured for sensing a current flowing in the primary winding. The current sensing circuit comprises a current sensing switch that is configured to be normally open and has a gate length smaller than a gate length of the primary switch. A relatively simple current sensing circuit is achieved and the overall power efficiency is improved.