Method to control a minimum pulsewidth in a switch mode power supply

A switching mode power converter comprising:

• a transformer having a primary winding coupled to an input supply voltage and a secondary winding;
• a switch coupled in series to the primary winding;
• a controller coupled to the switch, wherein the controller is configured to turn the switch ON and OFF;
• a primary side auxiliary winding magnetically coupled to the secondary winding;
• and
• a threshold voltage detection circuit coupled to the auxiliary winding and to the controller, wherein the threshold voltage detection circuit is configured to compare a voltage across the auxiliary winding to a minimum voltage while the switch is ON and to send a signal to the controller once the voltage across the auxiliary winding reaches the minimum voltage, wherein the minimum voltage is a minimum voltage across the secondary winding to enable energy transfer from a primary side of the transformer to a secondary side of the transformer,
• wherein the controller is configured to switch OFF the switch in response to receiving the signal from the threshold voltage detection circuit such that a minimum energy is stored in the primary winding necessary to enable energy transfer from the primary side of the transformer to the secondary side.