I found MPowerSaver (Monitor Power Saver), an useful tool that help you to turn off your computer when you lock your computer. MPowerSaver is a portable freeware program, so you don't have to install the program but only download and store in your local hard disk, then double-click and run it.
The Basics Of MpowerSaver
General Options
1) Automatically Turn off the monitor when user lock down their system (Win +L)
2) Automatically Turn off the monitor with screen saver starts. (Click check box to activate)
3) Automatically Lock and Turn off the monitor when system is in inactive mode. (Set time to activate)
4) Automatically Turn off the monitor when system is in inactive mode. (Set time to activate)Advance Features
Auto Sleep/Hibernate, Standby, Restart or Shut Down your computer on a daily or weekly basis.
Daily basis
For example, let’s say you want to set your computer to shutdown in fifteen minutes. First select
the Action Settings (Sleep/Hibernate, Standby, Restart or Shut down), then set the time and date. Once
that is complete you must click the (Start) check box and click (OK) button.Weekly basis
For example, let’s say you want to set your computer to shutdown every day at 11:00:00 PM.
First select the Action Settings (Sleep/Hibernate, Standby, Restart or Shut down), then set the time.
Once that is complete you must click the (Shut down Computer on selected days) check box
and select the days (Sun, Mon, Tue.Wed, Thu, Fri, Sat) you want to shutdown your computer,
and click the (Start) check box and click (OK) button.
Link : Monitor Power Saver