Richteralan

[center]Powering Your PC: Truths and Misconceptions
A Guide To Power Supplies[/center]

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A power supply performs the following functions:

• Rectification: Convert the incoming AC line voltage to DC voltage.
  
• Voltage Transformation: Supply the correct DC voltage level(s).
  
• Filtering: Smooth the ripple of the rectified voltage.
  
• Regulation: Control the output voltage level to a constant value irrespective of line, load and temperature changes.
  
• Isolation: Separate electrically the output from the input voltage source.
  
• Protection: Prevent damaging voltage surges from reaching the output; provide back-up power or shut down during a blown-out.
  

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Power Factor:

• Power Factor Correction (PFC) has become a hot topic, especially in European countries which PFC is required for power supplies above a certain power rating.
  Without getting all technical, Power Factor (PF) simply has to do with Actual Power vs. Apparent Power in an AC circuit.
  As we all know AC stands for "Alternating Current", which is the type of power that we all get from the power company, though it may differ in voltage and frequency.

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Power Supply Efficiency:

• A power supply\'s efficiency rating is determined by the ratio of AC power going in to the DC power going out.
  Generally this comparison is done using Watts as a common unit of measurement. Anything less than 100% efficiency is dissipated wastefully as heat.
  In reality no power supply will be 100% efficient, that\'s just a fact of life, however you can (and should) avoid power supplies with very low efficiency ratings.

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5毫子

Good Article
however, there are quite a lot of stuff I dun really understand.......