The term power management( PM) is used in computer technology and includes all measures to reduce the power consumption of computers, peripherals and mobile devices. In this context, one also speaks of power-saving operation and power management.
Power management in portable devices
Power management is primarily targeted at mobile computers, at laptops, notebooks, netbooks and handhelds, because it increases the operating time in battery mode; however, it is equally targeted at stationary desktops to save energy.
Energy-saving measures involve the use of power-saving components, such as ultra- low voltage ( ULV) processors, energy-saving modes, such as idle state or sleep mode, or other measures, such as reducing the CPU clock frequency or supply voltage, which is done with Dynamic Voltage Scaling( DVS) and the more effective Adaptive Voltage Scaling( AVS). Other power saving techniques include dynamically adjusting the supply voltage and clock rate to match the workload, which is done with Dynamic Voltage and Frequency Scaling( DVFS) and Demand Based Switching( DBS), temporarily turning off the clock frequency, Clock Gating, and briefly turning off power to unused components, Power Gating.
Power Saving Modes
When a computer is running, only a few components and peripherals are in use at any given time. The components that are not activated for processing and peripheral devices that are not relevant can be switched off or put into standby mode as long as they are not needed. For mobile devices, there are several power saving methods such as Dynamic Voltage and Frequency Scaling (DVFS), Dynamic Process and Temperature Compensation ( DPTC), idle time prediction, which activates power-saving idle modes, or Dynamic Power Management( DMP). In addition, there is also clock frequency gating, clock gating, and supply voltage gating, power gating, as well as Advanced Power Management( APM) and Advanced Configuration and Power Interface( ACPI). For lowering the power consumption of displays, there is the Display Power Management System( DPMS). This method, standardized by the Video Electronics Standards Association( VESA), finds its origin in the high power consumption of displays with cathode ray tubes( CRT).
In mobile devices, the share of static power, which is always needed, is still far below the dynamic power share, but it is increasingly rising as more and more components need to be supplied with power in idle mode. A reduction of the static share increases the time in which the mobile devices can operate in battery mode.