This paper presents the self-oscillating flyback converter with an integrated flyback-transformer whose auxiliary winding is utilized as the lossless snubber inductor and output-voltage sensing winding. In the conventional flyback converter, the turn-off switching loss caused by high switching frequency leads to low conversion efficiency. The proposed lossless snubber scheme not only reduces the voltage spikes at turn-off interval, but also recycles the energy stored in the leakage inductor to the input source for improving conversion efficiency. Considering further simplification, the lossless snubber inductor and the output-voltage sensing winding can be combined together as a single winding. A prototype circuit of the 15W self-oscillating flyback converter with lossless snubber circuit and output-voltage sensing circuit is built to verify the performances, such as the voltage stress on the switch, the conversion efficiency, and the load regulation.