Heart of a System

When thinking about the heart of a PC, most of you may think that I’m gonna talk about the CPU, which is the well-known “core”. However, that would be too obvious. No. Instead, today I will talk about the Power Supply Unit, or PSU, which is the actual heart of the system, where as the CPU is more like the brain. So, what makes this part so important that it’s got the title of “heart”? The answer is simple, really: It keeps everything running. Without a PSU, or with an inadequate PSU, your PC won’t even run, and a PSU of poor quality can cause fatal problems to your system, as well as giving your components (such as the motherboard) permanent damage! Holy cow, what should we look for to prevent that from happening, then? Well, I’ll get to that in the moment.

The basic specs of a PSU


There’s actually quite a lot to say about PSUs, but here are the three basic specs you should look for:

  • First is the PSU’s capacity, or “wattage”, measured in, you guessed it, watts. Ideally, the PSU’s capacity should be at least 20-30% higher than your PC’s “estimated power consumption”. You can ask a seasoned builder or technician to estimate your build’s power consumption, but once you are more experienced you can most likely estimate that yourself.
  • The next one is the PSU’s efficiency, measured by percents. You can guess a PSU’s efficiency based on its 80 Plus Certification (more on that later), but the best way to know a PSU’s real efficiency is still to read informative reviews.
  • Whether the PSU is modular, semi-modular or non-modular. For modular PSUs, all cables are detached and you can plug the ones you need in the PSU individually. Semi-modular PSUs work largely similar to modular PSUs, but have some essential cables pre-attached and can’t be removed. Non-modular PSUs have all of the cables hardwired into the unit.

The 80 Plus Certification


Basically, the 80 Plus Certification confirms a PSU’s efficiency at different load levels, in different AC input voltages (110V and 230V). There are six levels: Standard, Bronze, Silver, Gold, Platinum and finally Titanium. Here’s the 80 Plus table: 80 Plus Table Also, while this is not technologically true, a PSU’s efficiency also tend to scale with that PSU’s capacity in real life. For example, you’d be hard-pressed to find a Platinum unit in the 600-700W range, but it’s quite easy to find one in the 1000+W range. Ok, so with the two basic specs being done with, what else is there to look at in a PSU?

A look inside


Well, before we get to the more advanced specs, let’s take a look inside a PSU to get an idea what I’ll be talking about. I’ll use the Snow Silent 1050W from Seasonic for this blog post, with images coming from the famous PSU reviewing site Jonnyguru. Well, first, let’s look at the PSU at a whole: Snow Silent 1050W - Inside Looks pretty nice and cluttered, huh? This is a very high-grade PSU though. Unfortunately not every PSU looks like this. Oh, and while we are looking at this picture, I’d like to point out that the three large capacitors at the back are the main filter capacitors. More on that later. Anyway, first, we have the fan. What this does is pretty obvious. Snow Silent 1050W - Fan Some notes on this though: While newer or higher-class PSUs tend to use one single 120mm (or bigger) fan, many older or lower-quality designs use multiple small fans on different sides of the unit instead. Next, we have the most important parts, the filters and rectifiers. The filters will… filter the input current to get rid of the “ripples” and “spikes” in the electricity flow (basically, the sudden changes in power), resulting in a more stable power flow. On the other hand, the rectifiers will convert the AC power (in electricity nets) to DC power, which is needed for the computer to run.

The line filter on the AC plug.
The line filter on the AC plug.
Capacitors (including the main filter caps mentioned above), coils and diodes are regularly used for filtering and rectifying. Though, to be honest, this picture is a bit cluttered so I'm not quite sure which is where.
Capacitors (including the main filter caps mentioned above), coils and diodes are regularly used for filtering and rectifying. Though, to be honest, this picture is a bit cluttered so I’m not quite sure which is where.

Next, we have the switchers, these decide which output rail to use out of the three rails found in PSUs: the 3.3V rail, the 5V rail, and the 12V rail. The 12V rail can be considered the “main” rail where as the other rails can be called “minor rails”, although all three are essential for your computer and are used for different parts.

A Switcher is circled in this picture.
A Switcher is circled in this picture.

Then, we have the heatsinks and the Power Factor Correction (or PFC), which for some reasons are usually built together. The heatsinks in turn are divided into primary heatsinks and secondary heatsinks, though I don’t really understand that part much. The Power Factor Correctors, as their name implies, are supposed to improve the power factor (real power/supposed amount of power fed ratio) of the output current.

The four diodes in this image are power factor correctors. As you can see, they are integrated into a heatsink.
The four diodes in this image are power factor correctors. As you can see, they are integrated into a heatsink.

Moving on, we have the Pulse-Width Modulation Controller, or PWM Controller. This thing controls the fan speed, as well as the PSU’s power output, depending on the workload.

The PWM controller is circled.
The PWM controller is circled.

Finally, we have the modular board. This part contains the plugs for modular PSUs, and sends the current with the suitable output voltage to each cable. Snow Silent 1050W - Modular Board Of course, there are many other parts in the PSU not pictured here too. The most important of which is the Voltage Regulation Modules, or VRM. These chips stabilize the output voltage to make sure it doesn’t fluctuate too much, but they are quite hard to be captured on camera. The protection circuits are very important, too.

The specs of a PSU, part two


Ok, with all of that being said and done, let’s discuss what you should look for in a PSU one more time! This time, I’ll dig deeper into the things that really differentiate PSUs from one another.

  • First of all, brand. Yes, brand. The thing you thought is only important in fashion. For a PSU, brand is very, VERY important, because of good old build quality and materials quality, which are crucial for a part like this. I’ll give you some PSU brands that are worth considering below.
  • For something more technical, you may consider the PSU’s voltage regulation. Normally, you’d like a voltage fluctuation of under 1%, in even the harshest conditions (loaded to the PSU’s rated capacity or preferably more), for a high-grade PSU.
  • Next, you should look at the ripple control. You’d like a voltage ripple of under 120mV for the 12V rail, 80mV for the 5V one and 50mV for the 3.3V one, in a high-grade PSU.
  • Then, you’d like to look at the PSU’s working temperature. A high-grade PSU should be able to keep its rated efficiency (see the 80 Plus section above) at even 50 degrees C.
  • Next, you should check the PSU’s safety measures. Does it have efficient overvoltage protection? Undervoltage protection? Surge protection? Overwattage protection? etc. The very, VERY last thing you’d like to happen is the PSU LITERALLY EXPLODING! That’s the very, VERY worst thing that can happen to your computer, believe me!
  • Afterwards, you should also check the fan. Is the fan of good quality? By the way, if your PSU uses a 120mm fan, which is the norm for computer components today, you can always replace it with some modding!
  • Finally, this may be a minor thing, but you should also check if the PSU uses 100% Japanese capacitors. It may sound nationalist, but Japanese capacitors are widely known to be of very high quality compared to Taiwanese or Chinese capacitors, or pretty much capacitors from any other country.

Ok then. Time to talk about the brands you should choose, I suppose!

Some PSU brands worth considering (note: this part is actually worth looking this time around!)


  • Seasonic is one of the leading Original Electronics Manufacturers (OEMs) today, as well as my personal favorite. Although Seasonic does sell PSUs under their own brand, there are also some very popular companies who distribute Seasonic-based platforms like EVGA and XFX. Corsair is also their occasional customer, though I can only recommend Corsair’s hi-end series, from at least the RM series, preferably the HX series, and up.
  • The second major player is Super Flower. Again, they do sell their PSUs themselves, but EVGA‘s very best PSUs are also from them.
  • While not as strong as the aforementioned two today, FSP is still one of the longest-running OEMs, so if you like those “since 19xx” brands you can consider them. They also make be quiet!‘s top PSUs.
  • Channel Well Technology is also a pretty popular OEM. They make most of Corsair‘s hi-end PSUs (though the very best ones come from Seasonic and Flextronics). They are also capable of making very poor quality products though, if they are asked to, so it’s recommended to buy their PSUs through the aforementioned reputable distributors.
  • If server PSUs or plain-looking PSUs is your thing (though to be honest there’s not much difference between a “server” PSU and a normal desktop PSU…), then Delta may just be your choice. They don’t do as well as Seasonic or Super Flower specs-wise (counting the “advanced specs”, of course), but they may just have the very best build quality here.
  • You may also consult this convenient, well-written PSU Tier List while looking around!
  • Just a side note, but you can also buy some custom cables for your modular PSUs if you like! They are quite expensive, but they are worth it if you are a real enthusiast looking to build a hi-end PC. CableMod is a popular choice.
I mean, aren't they cute?
I mean, aren’t they cute?

Whew, that was another long blog post! And I did all of that near midnight, at that. Well then, I hope after reading this, you’ll care a bit more about your computer’s safety, and make sure you don’t spend just your spare pocket change on the “missing part”, which is usually the PSU! Happy building, and thank you again for supporting me! 🙂

Update: If you still want more information regarding the PSU (since my post is pretty basic), you can do some further reading on this elaborate article by TechPowerUp, if you haven’t already! ^^

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