Computer Power Supply

All electronic systems and equipment regardless of their size or function have one thing in common: they all need a power supply unit (PSU) that converts input voltage into a voltage or voltages suitable for their circuits. The most common type of today`s PSU is the switch mode power supply (SMPS). There is a wide variety of SMPS topologies and th
Computer Power Supply - schematic

eir practical implementations used by PSU manufacturers. However they all use the same basic concepts. This page explains the principals of operation of a switching mode power supply and reviews its main parts and functions. This tutorial can be useful for system integrators, hobbyists, and those who are not necessarily experts in power electronics. This is a conceptual circuit diagram of the power train of a typical ATX computer power supply unit. This schematic does not show the control circuitry, that`s why you see all MOSFET gates and transistor bases are open. For clarity, the parts responsible for miscellaneous auxiliary functions, such as current limit, fan control, and OV protection, which are not essential for learning the basic concepts of the power conversion, are not shown as well. For a complete schematic, see for example this annotated diagram of an ATX power supply. Note that unlike generators that convert energy stored in various fuels into electricity, PSUs convert electric energy from one form to another. The AC input receptacle in a PC is an IEC 320 type or equivalent. The fuse "F" is followed by an EMI filter. The filter is normally consists of a combination of differential mode and common mode chokes and capacitors. Its main purpose is to reduce the conducted radio frequency noise emitted from the power supply back into the input line to comply with regulatory requirements. Reducing conducted noise also...

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