Schaltnetzteil mit einer Funktionalität zur Erkennung einer unterbrochenen Rückkopplungsschleife

摘要

The invention relates to a switched mode power supply with the following features: a primary coil (L1) and a switch element (TS) wired in series with the primary coil (L1), for applying a DC voltage (Vg) to the primary coil according to a control signal (AI); a secondary circuit, coupled to the primary coil (L1) with output terminals (AK1, AK2) to provide an output voltage (Vout); a control circuit (IC), for preparation of the control signal (AI), with a feedback signal (Urk) dependent on the output voltage (Vout) supplied to the control circuit; the control circuit (IC) comprises a signal generation circuit (PWM) to create the control signal (AI) and a protection circuit (PUS). Said protection circuit (PUS) has the effect that no control signal (AI) is delivered to the switch element (TS), if the feedback signal (Urk) reaches the value of a first reference signal (U1) after a first period (T3) after starting the control circuit (IC).