Voltage Regulators and Coil Whine - what are the causes and how to really eliminate it

General

Now, when I write about voltage regulators here, one or the other may now interject: »Didn't you say that it has to rotate, vibrate, or otherwise move a bit for annoying noise to arise? Nothing moves inside a voltage regulator!. So such a part CAN'T emit any annoying noises by itself!« Yes, I had written that and at first glance (and perhaps also on the second and on sleepy Sunday mornings possibly also on a third) it probably is the case all parts of such a voltage regulator are soldered into forced rigidity onto a circuit board to endure its dreary existence. But if you look at this a bit more closely, then something moves there nevertheless. And these somethings can — at least if one has at least a bit of bad luck — be really quite annoying.

But first things first! What is it that is moving? Where are those noises coming from? And most importantly: How do you turn it off?

At this point, a short insertion on the topic of voltage regulators. If you are less interested in understanding the cause and origin of the noise, but only in how to fix it, you can skip the next section and turn to possible possible 'countermeasures' further down the page. For all others, let me allow to digress for a bit and try to bring the matter a bit closer. I will keep it on the level of a technically interested layman. OK, let's get started.

The Cause

In our modern computers, there are quite a few of these voltage regulators installed, whose job it is to convert the voltage of the switching power supply (e.g., from the approximate 12V DC voltage), to the working voltage(s) (1.2V, 3.3V, 5V, …) needed for the individual components on a circuit board, e.g. your GPU. Most of these devices actually perform their work silently, and that is when the currents flowing through them are relatively low. Unfortunately, this isn't always the case, because some PC components require enormous currents and therefore the best known and unfortunately also the loudest representatives are found on modern high-performance graphics cards. The loudest representatives of those VRMs are found on modern high-performance graphics cards, where these noisy things are often found in large numbers.

Somewhat simplified, the core of such a voltage converter consists of an coil, a capacitor, an electrical switch (MOSFET) and a actuator for that switch (a PWM controller on the gate pin of the MOSFET), which then lets current flow to, and — after the build-up of the induced magnetic field — through the coil. Now, such a current is always accompanied by a magnetic field. And in a magnetic field, a force acts on the wires a current flows through: the so-called Lorentz force. But this force is not constant, but of course is changing with the same rhythm with which the magnetic field in the coil builds up and dissipates. And unfortunately, this often happens in a frequency range that is perceptible by the human ear, and then manifests itself in a more or less annoying whine, the so-called coil whine. What you hear exactly are the coil windings excited by this Lorentz force, which scrape and rub against each other (and also against the coil housing). Depending on the load of the voltage transformer, the whine can have a different amplitude (which determines the volume level of the noise) and whistles in different pitches (depending on the frequency of the PWM signal).

The Remedy

Now that we know how the noise is generated, we can consider how to get it under control most efficiently.

Of course, the simplest (but in most instances probably unsuitable) solution is to eliminate the flow of current through the coil ⇒ turn your computer off and spend your time on the patio, in the park or garden. No current, no Lorentz force, and no whining. This works, but who can (and wants) to spend that much time outdoors and away from his PC? So, no, there must be another way.

So, what do we really have to do if our PC has a graphics card installed that spoils our game sessions with that annoying coil whine? Fortunately, there are a few things that we can do in order to address the problem and if not completely eliminate so at least strongly to reduce the annoying noise. Often, the coil whine is loudest when the graphics card renders a very high number of frames. Unless you have an uber-mega-monster PC — or are playing a game with no graphics requirements whatsoever — then this occurs most often in menu screens, where the graphics card can easily render several hundred frames per second. As long as this FPS number lies well over that of the monitor, then the only 'benefit' of these additional frames is an increased power consumption. And with that also a clearly perceptible coil whine. The obvious remedy here is therefore to limit the number of frames to what is necessary and reasonable depending on the intended use. How many FPS you should aim for depends on your specific monitor model, its refresh rate and the supported technologies (G-Sync/FreeSync). For instance: to drive a 144Hz G-Sync monitor with more than 144 Hz rarely makes sense and therefore a good possibility to get rid of coil whine is to use a FPS limiter to cap the number of frames to a value below the monitor refresh rate — in the mentioned example e.g. to 140 or 141 Hz. Ideally, the FPS limiter that you should use is the one that the respective game already comes with. Only if this is not possible, you can also fall back on an external limiter, e.g. by using external tools like, in the case of an AMD graphics cards, the AMD 'Frame Rate Target Control' tool, the tool included with MSI Afterburner, namely 'Rivatuner Statistics Server' or by setting the corresponding entry in the Nvidia control panel. When using this approach, you have to make sure to never! use two limiters simultaneously! If you can set a limit in the game, then only use this and disable all other limiters.

With an FPS limit alone, you can in most cases already significantly reduce the problem of coil whine. But another approach, and one that is not quite as obvious, is to reduce the noise-causing friction of the coil windings directly. Since we cannot reduce the current and thus the force with which the coil windings are excited, and since the frequency of the PWM signal is determined by the design and cannot be changed, the only thing that we can do is to dampen the windings themselves. At this point, however, let me start with a warning: What I describe on the rest of this section is something that has proven itself well in practice, but where I must must point out that this kind of tampering can damage your hardware and I can not accept any liability for it.

So, what is it about and what else can be done about this coil whine? As mentioned several times, the noise is caused by the coils' windings rubbing against each other and against the coil housing, and that's exactly where you can reduce the noise, namely by making it more difficult for the coil windings to move by giving them no or less space to do so. At this point I want to strongly advise against experimenting with hot glue, because it does little or nothing (apart from destroying your graphics card). The means you can use to restrict a coil winding's freedom of movement are other coil windings. And you can achieve this by making them take up more space. As it turns out, the coil whine is a temperature dependent phenomenon. The warmer a coil is, the more space the windings need and the less they can move and rub against each other. Now, the only means to influence the temperature of these coils is to reduce their cooling specifically and moderately so that they become somewhat warmer, take up more room and and thus get quieter. This works quite well in practice, but of course one must not overdo it and also here it depends on the respective graphics card, how to best achieve this modification, because there are of course components in the immediate vicinity of these coils that would possibly resent a reduction in cooling and you therefore have to check in each individual case if and how this approach can be implemented.

Date published: 16.06.2021

Contents

Author: Udo Rietschel

Written by Udo Rietschel

Udo is one of the two founders of Argotronic UG (haftungsbeschränkt). He is writing software since he got his hands on his first computer (a ZX Spectrum 48k back in 1988, while living in the GDR; a country that does not even exist anymore -- much like his ZX Spectrum).
Today, he is working as a software engineer, creating software for autonomous vehicles as well as Argus Monitor, which is — in his (biased) view — the best fan control software for Windows.