| 摘要 |
A switched-mode power supply includes a transformer (T) with a primary winding (Lp), a secondary winding (Ls), and an auxiliary winding (La). A series arrangement of the primary winding (Lp) and a controllable switching element (S1) receives an input voltage (Vi). A drive circuit (1) supplies a drive signal to a control input of the controllable switching element (S1) for periodically switching the controllable switching element (S1) on and off. The secondary winding (Ls) supplies a DC output voltage (Vout) to a load (Z) via a rectifier element (D). The DC output voltage (Vout) is stabilized by averaging (21), during a certain period of time, information (Im;Id) related to feedback information (Va;Icon) supplied by the auxiliary winding (La). The certain period of time is obtained by detecting when the feedback information (Va;Icon) is larger than a certain reference value (Vref;Iref2) which is selected in such a way that a substantial part of both the leading and trailing edges of the feedback information (Va;Icon) do not occur within the certain period of time. |
