Control circuit on the primary side of an electronic power converter having a transformer without auxiliary winding with a regulation based on the secondary side current flow duration

摘要

The circuit (IC1) has a transformer (T) provided with a primary side winding (L2) and a secondary side winding. A primary side switch (Q2) e.g. FET, switches current through the primary side winding, where the circuit is connectable with a control input of the switch. A starting time of the switch is determined based on a secondary side current flow period. The switch is activated based on the secondary side current flow period in which the current flows through the secondary side winding, such that an output voltage (Vdc out) of a switched-mode power supply is regulated.