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Is it possible to build a system w/ all digital VRMs?
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Author:  Lower_The_Volume [ Thu May 02, 2013 9:32 pm ]
Post subject:  Is it possible to build a system w/ all digital VRMs?

Hi,

Fan noise is easy enough to manage, but capacitor squeal is what really drives me crazy.

I've been looking into motherboards that use only digital VRM, so far some eVGA FTW or Classified boards are the only ones I've been able to find. I think they're made by EPoX.

I haven't been able to find any video cards that use it either. ATi did for a while use volterra digital VRMs but stopped for some reason.

Gigabyte has advertised solid capacitors for a long time now in their ultra durable line, but I still get high frequency noise coming from their boards.

Then there's the power supply, which seems impossible to avoid capacitors & coils. I've been subscribing to the idea that if I buy a grossly overpowered high quality PSU (like Seasonic X Series or Platinum 800ish Watt) and use it in a lower powered underclocked system the frequency of the coils would be low enough to avoid any sonic vibrations. This is pure hypothesis though.

Does anybody have knowledge of any components I can use to attain my goal?

Author:  Vicotnik [ Fri May 03, 2013 11:31 am ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

Is it really the capacitors that makes the noise? I thought it was coils and such. Anyhow, it's my experience that low power stuff whine less than high power stuff, so luckily I've had little problem with whining components.

Author:  faugusztin [ Fri May 03, 2013 1:15 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

Capacitors don't make any noise (except "boom" when they blow up). The noise you are talking about are from coils. And no, you can't avoid them.

Author:  MattHelm [ Fri May 03, 2013 2:38 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

First, the digital part of VRM is what makes the noise. If you make a analog Voltage regulator module, you would get no noise from the power supply. Of course the furnace squirrel cage fan would be a bit noisy.

Author:  Lower_The_Volume [ Fri May 03, 2013 10:05 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

Vicotnik wrote:
Is it really the capacitors that makes the noise? I thought it was coils and such. Anyhow, it's my experience that low power stuff whine less than high power stuff, so luckily I've had little problem with whining components.


faugusztin wrote:
Capacitors don't make any noise (except "boom" when they blow up). The noise you are talking about are from coils. And no, you can't avoid them.


My understanding was that the capacitors had harmonic vibration. In the folding community, some people who have been especially tortured by nVIDIA's squealing / whining caps used nail polish or silicon to attempt and reduce the squeal.

https://theovalich.wordpress.com/2008/1 ... squealing/

http://www.overclock.net/t/476207/squealing-capacitors

Maybe it is the inductors as well. I know when I power off my PC I can literally hear the capacitors drain as the squealing slowly quiets.

Asus has recently made chokes for their higher end cards that are set in concrete. I've never had an opportunity to hear one to see if it actually makes a difference though.

http://www.bjorn3d.com/wp-content/uploa ... design.jpg

MattHelm wrote:
First, the digital part of VRM is what makes the noise. If you make a analog Voltage regulator module, you would get no noise from the power supply. Of course the furnace squirrel cage fan would be a bit noisy.

I should have said Solid-State instead of Digital. It wouldn't let me though as the title didn't offer enough characters.

e.g. http://www.irf.com/whats-new/nr111201.html & http://www.vishay.com/power-ics/integrated-drmos/

Author:  xan_user [ Sun May 05, 2013 4:49 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

faugusztin wrote:
Capacitors don't make any noise (except "boom" when they blow up). The noise you are talking about are from coils. And no, you can't avoid them.

hmm. the ones in my gateway monitor sure did squeal really loud, till i replaced them....

Author:  Mr Evil [ Thu May 09, 2013 2:06 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

faugusztin wrote:
Capacitors don't make any noise (except "boom" when they blow up). The noise you are talking about are from coils. And no, you can't avoid them.

They can make noise, due to electrostriction.


MattHelm wrote:
First, the digital part of VRM is what makes the noise. If you make a analog Voltage regulator module, you would get no noise from the power supply. Of course the furnace squirrel cage fan would be a bit noisy.

You're thinking of switch-mode vs linear. Switch-mode regulators are not inherently digital. People think of them as digital only because they output pulses which look like digital 1s and 0s.

Author:  QUIET! [ Sun May 12, 2013 4:31 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

For people who don't know, transistors are kind of like dimmer switches and that region between all the way on and all the way off is called the linear region.

Like a dimmer switch set at half on, a transistor at half on will generate a lot of heat. That's not efficient so (step down) switch mode power supplies work by turning switches all the way on or all the way off which creates a whole lot less waste heat. When that switch is on it is allowing charge to flow in to a capacitor and adjusting the on duty cycle of that switch is how voltage is regulated, when more current is drawn, output voltage sags and duty cycle increases to compensate, when load is reduced, output voltage raises and duty cycle gets reduced.

The circuit that senses the voltage is nearly always an analog circuit because the alternative is a high speed ADC (switched capacitor is one type) and that is a lot more complex than a comparator, not tremendously accurate and then you need more circuitry to do something with the digital output.

There are always a lot of analog blocks like a bandgap reference, oscillator and others.

A power supply with a lot of digital circuitry can be done but that's mostly if you want to do some weird control tricks like changing the switching frequency, low power states and whatnot.

The part where it gets fuzzy is that a lot of those tricks can be done with analog circuits too and at the same time, every analog integrated switch mode power supply will have "digital logic" control circuitry; nands, nors, inverters, aois, transmission gates, dlatch, etc.

The "analog" dc-dc stuff I worked on was not what you would see supplying lots of current on a motherboard or video card but they are close enough to make comparisons.

I never did "digital" dc-dc because it didn't make business sense, too much r&d, wafers more expensive and no convincing use case.

Some companies make a name for them self by leveraging technology to add a lot of features to simple products like power supplies. Others strip away the bs and deliver on performance and cost.

Author:  Vicotnik [ Sun May 12, 2013 11:58 pm ]
Post subject:  Re: Is it possible to build a system w/ all digital VRMs?

Thank you QUIET! :) Interesting post.

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