UCC28950: Some problem relate to transient output peak current using UCC28950.

Hello Kyeongmin

Can you tell me what the two plots show please?.

Can you also provide a plot of the voltage at the SS/EN pin during this event.

I think that the controller is entering hiccup mode during the over current event. It is possible to increase the time delay before entering hiccup mode by increasing the capacitor at the SS/EN pin - this will also increase the soft start time. You can also use a pull up resistor from SS/EN to VREF to increase the time needed to enter hiccup mode. These options are explained in the document at.

/cfs-file/__key/communityserver-discussions-components-files/196/UCC2895x-Hiccup-prevention.docx

Please let me know how you get on.

Regards
Colin

Thank you for reply.

I want to reduce output peak current.  I just wonder what relationship is between increasing OFF TIME and peak current ?

Can you tell me what the two plots show please?.
--> yellow one is output voltage , green one is output current

Can you also provide a plot of the voltage at the SS/EN pin during this event.
--> Sure , let me check after get customer set.

Let me check our circuit as you recommend as well.

This is our circuit of around ss/en pin.

Could you plz tell us any advice. thank you

Hello Kyeongmin

Thanks for identifying the two plots. So the customer product is connected and there is a large inrush current at that time. Is there a way to reduce the amplitude of this current and is this the expected level of current. There would also be a possibility that there is a spark as the customer unit is connected and this could cause long term damage.

Please explain the function of the opto-coupler in the circuit above.

I think that something is pulling the SS/EN pin low and that this is stopping the controller from switching. That is why I'd be interested to see the waveform at SS/EN.

Regards

Colin