the present invention discloses a power supply control circuit , the power supply providing an output voltage to an output terminal from an input terminal through a transformer having a primary winding and a secondary winding , the power supply control circuit comprising : a power switch electrically connected with the primary winding ; a switch control circuit controlling the power switch ; and a sensing circuit supplying an output signal to the switch control circuit according to voltage signals obtained from two sides of the primary winding , wherein the sensing circuit includes a setting circuit for deciding the output voltage according to a reference signal . the present invention also relates to a voltage sensing method in the power supply control circuit .