| 摘要 |
A DC/DC voltage converter having mains power supply isolation for input voltages (UE) having an extremely large variation range contains a switching transistor (T3) in whose collector circuit there is located a transformer (Ü) having primary, secondary and auxiliary windings (1,2; 6,7,8; 3,4), and in whose emitter circuit there is located an emitter resistor (RE) on which a voltage (UE) is picked off which is proportional to the current (i). It furthermore contains a control-pulse circuit (ST) having a first circuit (IC1), which is connected as a voltage-controlled multivibrator and supplies triggering signals via a first differentiating element (C4, D4) to a second circuit (IC2) which is connected as a triggerable comparator. The comparator (IC2) compares the voltage dropped on the emitter resistor (RE) with a fixed reference voltage (Uref). The voltage produced in the auxiliary winding (3, 4) is used to control the frequency of the voltage-controlled multivibrator (IC1) as a function of the load on the output of the transformer (Ü) and, in addition, to produce an auxiliary voltage (UH) as the voltage supply for the control-pulse circuit (ST). While the DC/DC voltage converter is being switched on, the auxiliary voltage (UH) is produced via a separate starting circuit (AS) which operates only until the flyback converter is oscillating. <IMAGE>
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