| 摘要 |
Switched mode mains power supply unit having a transformer (Tr), which comprises a primary winding (LP) and at least one secondary winding (LS) as well as an auxiliary winding (LH), having a switch (S) controlled by a control circuit (A), by means of which switch the primary winding is connected to an input direct voltage (UE), having, connected downstream of the secondary winding, a rectifier (D1) together with a filtering means (C1) for producing an output direct voltage (UA) and having a regulator means (K1) for producing a first control variable (St1) for the control circuit (A) in dependence upon the deviation of the output voltage from a first set value (URef1), wherein the pulse duty ratio and/or the frequency of the control signal of the controlled switch depends upon the control variable, and also having an auxiliary rectifier (D2; Glr) connected downstream of the auxiliary winding (LH) in order to produce an auxiliary direct voltage (UH) for the control circuit and/or other consumers, having an auxiliary regulator (K2) to produce a second control variable (St2) for the control circuit (A) in dependence upon the deviation of the auxiliary direct voltage (UH) from a second set value (URef2), and having a selector circuit (AS) for priority supply of the control variable of that regulator to the control circuit (A), the actual value of which lies below the associated set value.
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