YOUR GUIDE TO COMPUTER POWER SUPPLIES:

TYPES, REVIEWS, SCHEMATICS, REPAIR GUIDES, AND OTHER INFORMATION

Power supply

unit (PSU) is a device that converts the input AC voltage to the DC voltages needed by a personal computer. Since the introduction of IBM PC/XT there have been about a dozen different PC types (such as AT, Baby AT, LPX, ATX, BTX, SFX, PS3, WTX, TFX, LFX, CFX, EPS) that differ by their structure, form factors, connectors and volt/amp ratings. The output rating of a modern computer power supply ranges anywhere from 185 W to two kilowatt. PSU over 400W are used mainly for Extreme Gaming & Media Entertainment PC, SLI support, as well as servers and industrial PCs.

Today's standard desktop PC PSU produces the following DC voltages: +5V, +3.3V, +12V1, +12V2, -12V and a standby 5V. Additional "point of load" DC-DC converters step down 12V to the CPU core voltage and other low voltages needed for motherboard components. All outputs should have a separate current limit to meet 240VA safety requirements of EN 60950, although in practice 12V rails usually have a combined current limit. To support PCI Express requirements in the new systems, the old 2x10 main power connector has been replaced by a 2x12 connector. An extra cable with 2x2 power connector is used for the second 12V rail that supports the processor's voltage regulator. There are also peripheral, floppy drive, and serial ATA connectors. The PSU for high-end discrete graphics cards have an additional 2x3 or 2x4 connector to supply extra power to a graphics card that require more than 75 Watts of total power. Older motherboards also used an aux power connector for 5V and 3.3V rails. For more info see PC PSU connectors and pinouts.

Power supplies for computers utilize switching mode technology. Most of today's models are ENERGY STAR® compliant. In the past it just meant they consumed <10% of rated power in standby mode. However in active mode the efficiency of cheap computer power supplies used to be 65-70%. Several years ago was introduced an electric utility-funded incentive program called 80 PLUS® that requires PC and server power supplies to demonstrate efficiency >80% at 20% to 100% of rated load and Power Factor >0.9 at rated load. The updated ENERGY STAR Computer Specification (Version 4.0) sets similar requirements for internal PSU.

Here you will find schematic diagrams, reviews, pinouts, specifications, and other useful information for repair and electronic projects.

YOUR GUIDE TO LAPTOP BATTERIES AND CHARGERS

COMPUTERS POWER SUPPLY BASICS

COMPUTER POWER SUPPLY SCHEMATICS & WIRING DIAGRAMS

PC POWER SUPPLY TYPES, STANDARDS, PINOUTS

Fundamentals of PC PSU: how they work,
specifications, noise

Comparison of PSU form factors and connectors

What Power Supply do I need

COMPUTER'S POWER SUPPLIES REVIEWS, TESTS and SELECTION

Intel's list of tested models

PC PSU testing methodology and block diagram

Inadequate and Deceptive product labeling: comparison of 21 PSUs

Review of eight SLI and/or Crossfire approved PSU's 550-750 W

ONLINE LEARNING AND DEGREES

How to connect a 20-pin PSU to a 24-pin motherboard and vice versa

DTK 200W ATX power supply schematic and theory of operation

300W ATX switching power supply: annotated schematic

ATX 250W PC SMPS with active PFC- annotated schematic and pinout

250W modified PC power supply circuit with synchronous rectifiers

Adding a second PSU- a guide for hobbyists

Design procedure and circuit diagram of 180 W SMPS for SFX case

300 W 80 PLUS® ATX SMPS reference design

FIND A COMPUTER POWER SUPPLY BY SPEC

Power Supply Design Guide 1.1 for Desktop Form Factors- combined requirements for the ATX, CFX, LFX, TFX, SFX and Flex ATX

OLD FORM-FACTOR SPECIFIC STANDARDS:

ATX12V v2.2- supports current and future I/O, processor technology and PCI Express®

SFX12V v3.1- for microATX and FlexATX

CFX12V v1.1- small form factor, BTX support

TFX12V v2.01 - for "thin" microATX and FlexATX

LFX12V V1.0 - for BTX support; ultra small form factor systems

EPS12V rev.2 - large ATX for entry server systems and industrial PC

PROBLEMS AND
REPAIR

Don't try to repair a PSU unless you are an adult, understand electronics and know how to deal safely with high voltage

PC PSU troubleshooting and repair

Test and troubleshoot laptop power supply

Safety quiz

Replacing a computer power supply

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