Power Manager
The power manager is responsible for managing power usage for the system. It administers the system-wide power policy and tracks the path of power IRPs through the system.
The power manager requests power operations by sending IRP_MJ_POWER requests to drivers. A request can specify a new power state or can query whether a change in power state is feasible.
When sleep, hibernation, or shut down is required, the power manager requests the appropriate power action by sending an IRP_MJ_POWER request to each leaf node in the device tree. The power manager considers the following:
System activity level
System battery level
Sleep, hibernation, or shut down requests from applications
User actions, such as pressing the power button
Control panel settings
For more information, see Windows Kernel-Mode Power Manager.