To provide a power control apparatus for reducing power, wherein the user can specify a time interval to stop driving a system, such as a computer system, there are provided a system-state detecting unit for detecting the drive state of the system, measuring unit for measuring a drive-stop designation...http://www.google.co.uk/patents/US5809316?utm_source=gb-gplus-sharePatent US5809316 - Power device of an information processing apparatus for adjusting a drive stop time period based upon system activity 
