Computer Motherboard Voltage Regulator Circuit

Everything You Need to Know About Thedesktop or laptop Motherboard Voltage Regulator Circuit

By Gabriel Torres 

Introduction
If you are willing to learn more about motherboard quality you must deeply study the
voltage regulator circuit, which is in charge of taking the voltage provided by the
power supply – namely +12 V – and converting it into the appropriate voltage required
by the CPU, memories, chipset and other circuits present. In this tutorial we will
present an in-depth trip inside the motherboard voltage regulator circuit, showing you
how to identify this circuit, how it works, what the most common projects are and how
to identify good-quality components.

The quality of the voltage regulator circuit is one of the best ways to have an idea
about the overall motherboard quality and life-span for several reasons. A good
voltage regulator won’t have any fluctuations or noise on its outputs, providing the
CPU and other components with a clean and stable voltage, allowing them to work
perfectly. A bad voltage regulator can lead to fluctuations or noise on the voltage that
will lead to malfunctions like the computer crashing, resetting and presenting the
infamous Blue Screen of Death on Microsoft Windows xp or 7.


If this circuit uses low-quality electrolytic capacitors they will leak, swell or even
explode. Frequently when a motherboard dies it is this circuit that goes bad. So having
a good-quality voltage regulator circuit will ensure that you will have a stable system
that will last for years.

Recognizing this circuit is pretty easy. Since it is the only circuit on the motherboard
that uses chokes (a kind of coil), locate the chokes and you will have located the
voltage regulator circuit. Usually this circuit is around the CPU socket, but you will find
some chokes spread on the motherboard, usually near the memory sockets and near
the south bridge chip, as they will be providing the right voltage to these components.

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Figure 1: Voltage regulator circuit.


Before explaining exactly how this circuit works, first let’s get you acquainted with the
main components found on the voltage regulator circuit

Desktop Computer Motherboard Meeting The Components

The main components of a voltage regulator circuit are the already mentioned chokes
(which can be manufactured using two materials, iron or ferrite), transistors and
electrolytic capacitors (good motherboards will provide solid capacitors, which are better).
The transistors used on the voltage regulator circuit are manufactured under a technology
called MOSFET (Metal-Oxide Semiconductor Field Effect Transistor) and many people call
them simply “MOSFET” (some motherboards, in particular the ones from MSI based on
"DrMOS" technology, use integrated circuits instead of transistors). Some motherboards
come with a passive heatsink on top of these transistors to cool them down, which is a
desirable feature. There are other very important components present on this circuit,
especially integrated circuits. You will always find an integrated circuit called “PWM
controller” and in good designs a tiny one called “MOSFET driver.” We will explain what
they do later.



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Figure 2: A close-up on the main voltage regulator circuit.
















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Figure 3: Motherboard with passive heatsink on top of the transistors.

Now let’s talk a little bit more about each component.

As mentioned, you can find two kinds of chokes on the voltage regulator circuit: iron

or ferrite. Ferrite chokes are better as they provide a lower power loss compared to

iron chokes (25% lower, according to Gigabyte), a lower electromagnetic interference

(EMI) and have a better resistance to rust. It is easy to tell them apart: iron chokes

are usually “opened” and you can see a thick copper wire inside, while ferrite chokes

are “closed” and usually have a marking starting with the letter “R” on top. On Figures

4 and 5 we show you the difference between them. There is one exception, though.

There are ferrite chokes that are big, rounded and opened, shown in Figure 6. It is

very easy to identify this kind of ferrite choke, as it is rounded instead of squared.

The voltage regulator circuit will have one choke per “phase” or “channel.” Don’t worry

about this now as we will explain what this is in detail later

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Figure 4: Iron choke.