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Computer power supply
Sunday, 12 November 2006

Computer systems in general and personal computer systems in particular have attained widespread use. The basic structure of a computer system includes one or more processing units which are connected to various peripheral devices, including input/output (I/O) devices such as a display monitor, keyboard, mouse, and a permanent storage device or hard disk, and a memory device (such as random access memory or RAM) that is used by the processing units to carry out program instructions. A typical computer system has a chassis that supports and encases a number of components of the computer system. The primary electrical interconnect component of a computer system is a backplane circuit board, such as a motherboard, that serves as a platform to which other components of the computer system may be connected. A motherboard primarily connects to one interior surface of the chassis in a plane parallel to the plane of the one interior surface. The motherboard typically has a number of sockets, slots, and plugs with which other circuit boards with components and other components with plugs may be connected to form electrical, and in some cases, mechanical connections between the circuit boards and components and the motherboard. One or more cooling fans are provided in such computer cabinets for circulating air and for changing air within the computer cabinet for maintaining the temperature within the cabinet within an acceptable temperature range. Desktop and small computer systems today all have integrated DC power supplies built into them. These supplies are designed to accept AC line voltage and convert it into various line-isolated, DC outputs required by the computer hardware. A general computer mainframe is installed with a power supply for supplying a steady and reliable voltage to the mainframe. The typical computer power supply is secured inside a chassis with the use of conventional screws, which require tools for installation and removal.

The personal computer requires an input of electrical power for energizing circuitry within the computer. Typically, the electrical input is derived from an alternating current (AC) voltage source typically referred to as house power. A desktop computer includes an internal power supply module disposed inside a housing of a main computer module for supplying power to a plurality of electronic devices that are mounted in the housing. Computer systems, such as personal computers and computer servers, use switching power supplies to transform the voltage value of local electrical power to an operational voltage. A switching power supply transforms the local electrical power and provides the computer system with a proper operational voltage. A switching power supply in a computer system converts the locally supplied alternating current (AC) power (usually 100-250 V) to a direct current (DC) power at a low voltage usable by the computer. The electrical power used in a computer system is a direct current with a voltage usually under 12 Volts. A switching power supply also distributes electrical power to the subsystems of the computer requiring different voltage levels, such as a CD-ROM drive, a floppy disk drive, a hard disk drive or a fan. Electrical and control signals are provided from the power supply  to power planes in a motherboard through a plurality of wires connected to a plurality of pins in an electrical connector, which mates with a corresponding electrical connector on the surface of the motherboard. A personal computer system will likely include one or a plurality of peripheral devices that are coupled to the system processor and that perform specialized functions. The power supply system for a personal computer are required to provide power to increasingly more peripherals, such as modem-facsimile, CD-ROM drives, printers, scanners, hard-disk drives, USB flash drives, etc. The power supply of a notebook computer includes a DC (direct current) power supply output unit outputting DC voltage supplied by either a battery source or an AC source. Notebook computer users do not have access to alternate current power supply when using their notebook computers in an outdoor environment, and they can use the power supply from the battery or a battery charger that supplies the necessary electric power. Since the power supply receives alternating current electrical power and converts the alternating current to direct current for operating the various electrical components, safety regulations require that the power supply be completely enclosed in a case to prevent access to potentially harmful high voltages.

The computer power supply is a vital part in computer operating system and any abnormality in it may interrupt the operation process. AC commercial power is used as a primary power source for computers and other data processing equipment that in turn use stored program and solid state technology. These circuits are generally very sensitive to input power variations from a desired standard waveform. However, commercial AC power waveforms are subject to many variations due to the demands of other users on the power line and other factors. Uninterruptible power supply (UPS) are used in a variety of different environments in which an interruption of power due to the variations or loss of the primary power source is unacceptable. An UPS serves to keep a computer operating by supplying power thereto when the power supply from the commercial power is stopped, for example, a power failure or breaker trip due to overload occurs. An UPS uses an inverter to convert a direct current (DC) from a battery into an alternating current (AC). As computer systems have increasingly been used, power consumption has increased accordingly. In this regard, a power management function has been employed in the computer system in order to minimize power consumption. Besides the working state and the power-off states, many modem personal computers implement power-saving states defined in the advanced configuration and power interface (ACPI) specification. According to the ACPI, a power management state in a computer system is roughly classified into six steps of sleeping states S0 through S5. The state S0 denotes a normal state (full power on), the states S1 through S4 denote standby states where power consumption of the computer system is stepwise reduced, and the state S5 denotes a soft-off state in which power of the whole system is cut off (full power off). The International Energy Star standard defines that a computer must comprise a function capable of activating the low-power mode and deep sleep mode of a display. The low-power mode is the first low-power state which is automatically activated after the computer does not operate for the first predetermined time. The deep sleep mode is the second low-power state which is automatically activated when the computer does not operate for the second predetermined time.


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