PMP8944: Inductor current rating

Hello Sarumathi,

Thank you for your interest in PMP8944.

The Startup VDD current for the controller is 11mA and the operating supply current is 2-3mA. There should not be any concerns about the Aux current rating here until it supplies that 11mA. 

Regards,

Sonal

Hello Sarumathi,

At the point where QMAIN is turned on the voltage on the transformer will be somewhere between the peak positive voltage on the FET (approximately 2 times Vin) and Vin. However, when the FET QMAIN is turned on, the magnetizing current through the primary winding will be flowing from QMAIN into the transformer and will be small in comparison to the load current. The only current that will immediately discharge through the FET QMAIN is the capacitive charge of the QMAIN and QAUX FETs because of primary side leakage inductance. Hence 60mA of the aux winding rating sounds alright to me.

Please refer to section 2.4 of the documentation https://www.ti.com/lit/an/slua535a/slua535a.pdf?ts=1590656074869 for better understanding.

I would also recommend using the Power stage designer tool to calculate your power stage component values.

http://www.ti.com/tool/POWERSTAGE-DESIGNER

I hope this helps.

Regards,

Sonal