| 摘要 |
A switched mode power supply (SMPS) as commonly used in consumer devices as television receivers, video recorders and audio equipment, is operated alternatively in a normal operating mode or in a standby mode with reduced or switched off operating voltages. Furthermore such a SMPS usually is provided with a protection circuit for the event of a short-circuit or an overloading or any other failure. Such a SMPS with a standby circuit and a protection circuit often exhibits a high complexity with a high number of components also reducing the reliability of the SMPS. It is an object to decrease the complexity and the number of components needed and thereby to improve the reliability of the SMPS. The switched mode power supply comprises a power switching transistor in series with the primary winding of a transformer and a further transistor (TP025) arranged at the primary side of the power supply, and further a standby control circuit arranged at the secondary side and coupled to said further transistor (TP025) for switching to stand-by mode in response to a standby switching signal (Us). The SMPS is further provided with a protection circuit (4) having an output terminal (b) coupled to the standby control circuit for actuating also said transistor (TP025) in the event of a fault and having a control input terminal (a) connected to different output voltages (UB2) which are generated by the switched mode power supply unit. <IMAGE> |
