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Welcome to the jonnyGURU Power Supply eBook
This book is free! No pay wall. No ads. No pop ups. Use it for research, Reddit arguments, cross reference, whatever.
Feel free to quote, copy, link, etc. Just don't deep link images (I pay for the server space) and please always give credit (even if its a simple 'courtesy of jonnyGURU')
This eBook is not meant to be in-depth or complicated. It is meant to be high level and light reading. It is intended for a wide audience. If you're interested in becoming an EE, particularly one that gets into the power supply industry, or just someone that wants to better understand how one of the parts of their computer works, this might be for you. If you're already an EE, you'll he bored to tears.
Also, I'm human, I make mistakes, and I'm not always the sharpest tool in the drawer. So if any one of you find a mistake.. or would like for me to make an addition, please don't hesitate to email me at jonnyguru at yahoo.com.
Speaking of "adding" to this eBook... I consider this eBook a "living document" in the sense that I fully intend to add to it, edit it, move things around, etc. I may add pictures or entire chapters. If you think something seems missing or "too short", be patient. I may be already working on expanding on it!
Jonny "GURU" Gerow
(Last edited 5/31/2026)
Table of Contents:
Introduction
In the Beginning
What is Ripple, Why is it Bad… and How Did it Change my Career Path
What is a Capacitor?
What Makes a Capacitor, “Super”?
The Capacitor Plague
What’s the Deal with Japanese Capacitors?
Capacitor Shelf Life
Can Capacitors Really Be Reformed?
How Did We End Up With Different AC Voltages?
How Does The Input Current and Input Voltage Impact The Power Supply?
The Different Power Cords Needed for AC Power
DC Outputs and Output Voltages
The Importance of Line Filtering
Why Does The Inrush Current Relay Make a Click Noise?
Power Rectification
Why are some power supplies “230V Only” and why can’t I find a 2000W PSU that works in my American home?
Understanding Power Factor
How do we Correct the Power Factor?
Yet Another Choice: Interleaved PFC
Interleaved PFC Can Make Noise at low-loads
The DC Bus and Bulk Capacitor
Why a UPS Without a Pure Sine Output May or May Not Be An Issue
The PWM Stage
Double-Forward vs. LLC vs. Active Clamp
Why Does LLC Sometimes “Click” at low-loads?
The Main Transformer
Secondary Rectification and Filtering
What is Group Regulation?
What is Magnetic Amplification?
Using DC to DC for the Minor Rails
Control & Feedback in an Analog PSU
What Does it Mean When a PSU is “Digital”?
What are “Protections” in a PSU?
Single Versus Multiple +12V Rails
What is an Inductor?
Understanding Inductor Noise, Also Known as “Coil Whine”
Using RTV to Help Silent Inductors
The Difference Between a Rod Core Inductor and a Toroid Coil
Using Sendust as a Ferromagnetic Material for Inductors
Split-Windings as Opposed to Single-Windings
When and where to use soft termination MLCCs
NP0 MLCCs for Current Transformer (CT) and Control Loop Circuits
What is “ATX 3.x” and the Difference Between ATX 3.0 and ATX 3.1
The PCIe 5.0 12VHPWR Connector
The PCIe 5.1 12V-2x6 Connector
The Move From 80MM to 120MM and Larger Fans
What’s Getting Hot Inside the PSU?
Looking at Thermal Reports
Routing Airflow
Disadvantages and Advantages of Cable Modularity
Understanding Cables, Wires, Terminals and Connectors
Springs versus Dimples and Play in the Connectors
Pigtails and Extensions
What is 80 PLUS?
What is Cybenetics?
What is the CQC Efficiency Certification?
Bibliography
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