Check your current sense signal: you may have large switching noises. And, it is strange that you only got 280Vdc with FB is not applied. It should have been higher when FB is not applied. On the other hand, the TPS40210 for 500W sounds excessive because the gate drive is not strong enough to efficiently drive the power MOSFETs for that high power. Is 500W a typo or real?

Sir,

To be frank , I needed to Design a boost converter ( Input DC is ~ 18-36VDC & output is ~ 260-300VDC ) . with 500W power.

So, i came across TPS40210 , Where Its can drive upto 300VDC , I got design from WEBENCH® Tools , I was happy, Buyed components designed PCB etc..

But , Couldn't get results..( Full upset )..

Plz suggest me other IC, where i get good results.. Once of my friend said go for LM5121...

( I am in critical position to get results )

The gate drive strength is a different issue, which just says you may not get 500W power. As you only get 280V, it implies a limited duty cycle issues. I am wondering how could you get the webench design? I tried with your input range and 500W load, the Webench could not generate a design. Could you share your webench design file with me?

We also have the LM3478 which is cable of large duty cycle, but its driver may still not supporting 500W unless you employ an external driver. Our other boost controllers like the LM5122/LM5121 have strong driver but the duty cycle may not support that large scale voltage step up. For 500W and such a voltage step up scale, you may consider a full bridge converter. Recommend you look at LM5045/LM5046.