kernal_task taking too much cpu

kernal_task in acitivity Monitory occupying more cpu usage. It happens when i am connecting my machine to to extended monitory(My LED TV) with playing videos in VLC. It goes to 500% and more .It slows down the entire machine. Even the video getting struck in VLC. When I disconnect from external monitor it goes down and getting normal. I'vd updated to Mojave, but still i'm getting this issues.

Thanks,

Ayyappan