1. go to control pannel
2. click on power options
3.left hand side click on 4th or 5th point which says " Choose when to turn off the display"
4. bottom left click on " Change advance power setting"
5.click on "Energy management" tab(mine is lenovo so the second tab next to "Advance Settings" says "Lenovo Energy Management"
6. in the middle click on "Energy management Tab"
7. Bottom Right is a circular icon move ur mouse over it which says"Click to change power scheme" Click on it
8. Finally click on "optimize for battery runtime" click apply and then on OK and ur problem is finally sorted.