| 摘要 |
Run/standby switching including switching to standby upon excessive current loading is provided in a switched mode power supply useful as an auxiliary power supply in a television. A switching controller IC (U1) is coupled between a primary transformer winding (W1) on the rectified raw B<+> (RAW B<+>) input voltage and ground. A switching transistor (Q2) is coupled to the control input of the controller and is biased by the raw B<+> input voltage for pulling down the control input (CNTL). A run/standby control circuit (R5, R6, R7, Q3, Q4, Z3, U3) and an overcurrent protective circuit disable the switching transistor during run mode operation and enable the switching transistor upon an overcurrent fault. The switched-mode power supply is further provided with a quick-reset capability (Q7, R11, R12) to enable the power supply to consistently provide output voltages which are within nominal output voltage levels despite rapidly repeated dislocations in the operational mode of the apparatus. |
