LM5022: Efficiency way off, much lower than expected based on webench design.

Hi Chis,

Thanks for reaching out with your question and for using the LM5022 in your design.

Can you please post the WEBENCH design and the schematic that matches your design? This will allow me to double check the components of the design. It sounds like something might be populated incorrectly. I would suggest taking a look at the RT pin resistor value.

Thanks,

Garrett

WBDesign36.pdf

6622.Sheet1.pdf

Hi Garrett,  Webdesign and my design attached.  I have already identified a few shortcomings.  One the input diode is a problem so that has been removed currently.  Also, there is a shortage if input capacitance compared to the webench.  I have tried adding to that with no effect on efficiency.  (It does help some under heavy load with low input voltage).

I checked the switching frequency and it is 195KHz which is close to the 204KHz design target.

Hey Garrett, any update on this ?

With TI separating from Avnet, I have a hard time getting any technical support.  Was hopeful I could use this forum.

Chris,

Is the MOSFET and the inductor on your board the same as the WEBENCH design? 

With the one the input removed, how much does the efficiency increase? 

Looking through your schematic I don't see anything that stands out as incorrect.

-Garrett