Power Supply Unit (PSU)

Power Supply Unit (PSU)Apor_Solera_Yutiu

It converts main AC to low-voltage regulated DC power for the internalcomponents of a computer.

Voltage of the PSUVoltage of the PSUThe PSU normally supplies +3.3 V, +5 V, and +12 V to the system. These voltages are often called rails, referring to the fact that although there are multiple wires carrying a specific voltage, they are normally tied to a single rail (or tap) in the PSU.Multiple wires are used because, if all of the current were carried over a single wire, the wire and the terminals, connectors, and even the traces on the circuit boards would all have to be extremely large and thick to handle the load. Instead, it is cheaper and more efficient to spread the load out among multiple smaller and thinner wires.

The digital electronic components and circuits in the system (motherboard, adapter cards, and disk drive logic boards) typically use the +3.3 V or +5 V power, and the motors (disk drive motors and any fans) use the +12 V power. In addition, voltage regulators on the motherboard or in other components convert these standard voltages to others as necessary.5Voltage Rail Usage in a PCRail

Devices Powered

+3.3 V

Chipsets, some DIMMs, PCI/AGP/PCIe cards, miscellaneous chips

+5 VDisk drive logic, low-voltage motors, SIMMs, PCI/AGP/ISA cards, voltage+12 V

Motors, high-output voltage regulators, AGP/PCIe cardsSIMM = Single Inline Memory ModuleDIMM = Dual Inline Memory ModulePCI = Peripheral Component InterconnectPCIe = PCI ExpressAGP = Accellerated Graphics PortISA = Industry Standard ArchitectureProblems with the PSUProblems with the PSU'Blue Screen of Death' (BSoD). This is due to cheap PSUs not being able to supply sufficient power to the components.Dust build-up. Symptoms are usually intermittent, and include unexpected reboots, startup failures, USB device failures, and hard-disk or memory errors.Insufficient supply of power.

Graphics card upgrades can be one of the biggest causes of PSU problems as they can draw a large amount of power. 8Other Problems Any power-on or system startup failures or lockups Spontaneous rebooting or intermittent lockups during normal operation Intermittent parity check or other memory-type errors Hard disk and fan simultaneously failing to spin (no +12 V) Overheating due to fan failure Small brownouts that cause the system to reset Electric shocks felt on the system case or connectors Slight static discharges that disrupt system operation Erratic recognition of bus-powered USB peripheralsDiagnosing a Failed PC Power SupplyMake sure that everything is plugged in.Hit the power button.Look at when your computer boots up.Check for beeps.Observe any computer failures.Check the fan in your computer.It's entirely possible that a cord could just slip out from the outlet while you're working. If power is present to the monitor and other peripherals, yet there is no power to your computer, there is likely something wrong with your power supply.The most obvious clue is that the system will do absolutely nothing when you hit the power button. If there is no sound and no monitor activity of any kind, the power supply has probably died. While this can also be caused by a faulty switch, it is usually the result of a burned-out power supply. Noticeable changes in how long it takes for your computer to boot up and shutdown, as well as spontaneous rebooting, could be a sign that something is wrong. If the system makes rapid, short beeps repeatedly and does not boot when you try to get it to, this could be linked to the power supply.If there are system startup failures or lockups, memory errors, HDD file system corruption or USB power issues, this is often directly related to your power supply.If the fan in your computer is failing to spin, it could lead to overheating and smoke in the system, all of which can cause a failed power supply. 10Importance of Surge Protection and Battery BackupImportance of Surge Protection and Battery BackupPower surges occur when something boosts the electrical charge at some point in the power lines. This causes an increase in the electrical potential energy, which can increase the current flowing to your wall outlet.Power surges, if high enough, can cause wear and tear on electronic devices, or in severe cases even destroy them.

Surge ProtectionThe surge protector detects excess voltage and divert the extra electricity into the grounding wire.This is why all surge protectors will have a grounding pin (the third prong on a plug) and all surge protectors must be plugged into a properly grounded outlet for them to work as intended.13Sources of Power SurgesThe most familiar source is probably lightning, though it's actually one of the least common causes.

The main culprit of electrical surges? Electrical devices that require lots of power to operate. the voltage of lightning is so great that most surge protectors wont be able to withstand their power. During a lightning storm, the only way to be absolutely sure that your devices wont be surged is to unplug them.

Depending on the wiring of your home, you may notice at times that your lights flicker when powerful devices turn on and off, e.g. your air conditioner. When these devices are switched on, they demand a lot of electricity, which puts a lot of strain on the grid and can cause surges.

14Battery BackupSurge protectors cover only one of the two common types of damaging power conditions, while an uninterruptible power supply can cover both.Aside from surges, it is heavily advised you DO NOT lose power while using your PC.Why is preventing your computer from losing power important? There are several reasons:

15Battery BackupA sudden power loss can corrupt your Windows installation, resulting in the computer refusing to boot up again without a visit to the repair shop.Brownouts and power losses can weaken the internal components of your computer or damage them outright, again resulting in a trip to the repair shop.If your computer shuts down unexpectedly while youre using it youll lose any unsaved work, which can be a huge loss if youve been working on an important project for an hour or two.As you can see, running your computer on wall power alone is extremely risky just because of the problems associated with power drops and outages.

16Battery BackupSurge protectors cover only one of the two common types of damaging power conditions, while an uninterruptible power supply can cover both.Uninterruptible power supplies (UPS), or battery backups, have a battery built in that can help bolster your voltage supply during under-voltage scenarios, as well as cut your electronics off from outlet power during a surge or spike.

17Referenceshttp://en.wikipedia.org/wiki/Power_supply_unit_%28computer%29http://www.tomshardware.com/reviews/power-supply-specifications-atx-reference,3061-2.htmlhttp://www.pcadvisor.co.uk/how-to/pc-components/3432554/problems-with-pc-heres-how-check-your-power-supply/http://electronics.howstuffworks.com/everyday-tech/surge-protector3.htmhttp://www.makeuseof.com/tag/do-you-really-need-a-surge-protector/http://www.tomshardware.com/reviews/power-supply-protection-calculate-consumption,3066-5.htmlhttp://arstechnica.com/gadgets/2011/05/video-ask-ars-why-should-i-get-a-battery-backup-and-how-do-i-pick-one/