Corsair VX450W Power Supply Review
By Gabriel Torres on March 26, 2008
Corsair is a traditional memory manufacturer they gained a lot of respect in the industry with their power supplies – we reviewed HX620W and TX750W and they are terrific products. But how the entry-level series from Corsair, dubbed VX, performs? Today we will take the most inexpensive power supply from Corsair, VX450W, and completely disassemble it and see if it can really deliver its labeled power.
As you can see, this power supply uses a big 120 mm ball bearing fan on its bottom (the power supply is upside down on Figures 1 and 2) and a big mesh on the rear side where traditionally we have an 80 mm fan. We like this design as it provides not only a better airflow but the power supply produces less noise, as the fan can rotate at a lower speed in order to produce the same airflow as an 80 mm fan.
This power supply has active PFC, a feature not usually found on entry-level power supplies. PFC provides a better usage of the power grid and allows Corsair to sell this product in Europe (read more about PFC on our Power Supply Tutorial). As for efficiency, Corsair says that this product’s efficiency is somewhere between 80% and 85%. Of course we will measure this to see if what the manufacturer claim is true. Keep in mind that more expensive power supplies have an efficiency of at least 80%. The higher the efficiency the better – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills.
The main motherboard cable uses a 20/24-pin connector and this power supply has one EPS12V connector that can be split into two ATX12V connectors.
This power supply comes with five peripheral power cables: one auxiliary power cable for video cards with one 6-pin connector attached, two cables containing three standard peripheral power connectors and one floppy disk drive connector each and two cables with three SATA power connectors each.
This power supply provides more connectors that Average Joe will ever need and it is great to see an entry-level power supply with so many power connectors, especially because the entry-level power supplies we reviewed recently have far less connectors (usually four peripheral power connectors and two or four SATA power connectors). The number of plugs should please all mainstream users and even more demanding users.
The only thing we didn’t like is that this power supply comes with only one video card power connector so users building an SLI or CrossFire system will need to use a power adapter with one of the cards. Zalman ZM360B-APS is rated at a lower power range and comes with two of them.
On this power supply +12 V and ground wires on the main motherboard cable, video card power cable and EPS12V/ATX12V are 18 AWG, but all other wires are 20 AWG (i.e. thinner). We’d like to see all wires 18 AWG.
On the aesthetic side Corsair used nylon sleeving on all cables, coming from inside the power supply housing.
This power supply is manufactured by Seasonic. It looks like a Seasonic from SII-12 series (SS-xxxSB) but we couldn’t confirm this. Also Seasonic doesn’t carry any 450 W model, so it seems that this model is manufactured exclusively for Corsair. After opening this power supply we found out that internally it is identical to Antec Earthwatts 500 W, but using better electrolytic capacitors.
Now let’s take an in-depth look inside this power supply.
We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our Anatomy of Switching Power Supplies tutorial to understand how a power supply works and to compare this power supply to others.
This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.
As we mentioned, internally this power is identical to Antec Earthwatts 500 W, but using better electrolytic capacitors.
As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.
This power supply is impeccable, bringing one extra X capacitor and one extra ferrite coil on this stage, plus two additional Y capacitors and one additional X capacitor after the rectifying bridge.
In the next page we will have a more detailed discussion about the components used in the VX450W.
We were very curious to check what components were chosen for the power section of this power supply and also how they were set together, i.e., the design used. We were willing to see if the components could really deliver the power announced by Corsair.
From all the specs provided on the databook of each component, we are more interested on the maximum continuous current parameter, given in ampères or amps for short. To find the maximum theoretical power capacity of the component in watts we need just to use the formula P = V x I, where P is power in watts, V is the voltage in volts and I is the current in ampères.
We also need to know under which temperature the component manufacturer measured the component maximum current (this piece of information is also found on the component databook). The higher the temperature, the lower current semiconductors can deliver. Currents given at temperatures lower than 50° C are no good, as temperatures below that don’t reflect the power supply real working conditions.
Keep in mind that this doesn’t mean that the power supply will deliver the maximum current rated for each component as the maximum power the power supply can deliver depends on other components used – like the transformer, coils, the PCB layout, the wire gauge and even the width of the printed circuit board traces – not only on the specs of the main components we are going to analyze.
For a better understanding of what we are talking here, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one GBU806 rectifying bridge in its primary stage, which can deliver up to 8 A (rated at 100° C). This bridge is attached to the same heatsink where the switching transistors are located. This is more than adequate rating for a 450 W power supply. The reason why is that at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.
On the active PFC circuit two FQH18N50V2 power MOSFET transistors are used, each one capable of handling up to 20 A at 25° C or 12.7 A at 100° C in continuous mode, or up to 80 A at 25° C in pulse mode. These transistors are located on a separated heatsink, together with the active PFC diode.
On the switching section this power supply uses another two FQH18N50V2 power MOSFET transistors in two-transistor forward configuration. As mentioned these transistors are capable of handling up to 20 A at 25° C or 12.7 A at 100° C in continuous mode, or up to 80 A at 25° C in pulse mode each and are located on the same heatsink as the rectifying bridge.
The primary section is controlled by a CM6800 integrated circuit, which is a very popular active PFC and PWM controller combo. It is located on a small printed circuit board attached to the main board.
This power supply uses four Schottky rectifiers on its secondary.
The +12 V output is produced by two SBR30A50CT Schottky rectifiers connected in parallel, which can deliver up to 30 A each (15 A per internal diode, measured at 110° C). The maximum theoretical current the +12 V line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by two 15 A diodes in parallel). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 43 A or 514 W for the +12 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.
The +5 V output is produced by one STPS30L30CT Schottky rectifier, which support up to 30 A (15 A per internal diode, measured at 140° C). The maximum theoretical current the +5 V line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode (which in this case is made by one 15 A diode). Just as an exercise, we can assume a typical duty cycle of 30%. This would give us a maximum theoretical current of 21 A or 107 W for the +5 V output. The maximum current this line can really deliver will depend on other components, in particular the coil used.
The +3.3 V output is produced by another STPS30L30CT Schottky rectifier, which support up to 30 A (15 A per internal diode, measured at 140° C). So the maximum theoretical power the +3.3 V output can deliver is of 71 W.
Even though this power supply has a separated rectifier for the +3.3 V output, this rectifier is connected to the same transformer output as the +5 V line, so the maximum current +5 V and +3.3 V can pull together is limited by the transformer.
This power supply uses a semiconductor thermal sensor, which is very small and installed on the solder side of the printed circuit board, between the transformer and the +12 V rectifiers. This sensor is used to control the fan speed according to the power supply internal temperature.
The secondary is monitored by a HY510N integrated circuit, which is installed on a small daughterboard and provides some of the power supply protections, like under voltage (UVP) and over voltage (OVP).
This power supply only uses Japanese electrolytic capacitors from Chemi-Con, with the active PFC capacitor being rated at 105° C instead of 85° C like on other power supplies. This gives us a hint of the quality of this power supply. Antec EarthWatts 500 W, which is basically the same power supply with a different housing, uses Taiwanese caps.
In Figure 14, you can see the power supply label containing all the power specs.
This power supply uses a single rail design, so there is not much to say here. Antec EarthWatts 500 W, which is basically the same power supply with a different housing, uses a dual-rail design. The difference between the two is only how the OCP (over current protection) circuit is connected. On this power supply this circuit is monitoring all +12 V outputs at the same time, while on the model from Antec this circuit is monitoring two different sets of wires.
Now let’s see if this power supply can really deliver 450 W of power.
We conducted several tests with this power supply, as described in the article Hardware Secrets Power Supply Test Methodology.
First we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load.
Since this power supply has only one rail, we connected all power supply cables to the +12V1 input from our load tester.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (e.g., the +5 V output working at +5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
6 A (72 W)
13 A (156 W)
19 A (228 W)
25.5 A (306 W)
32 A (384 W)
1 A (5 W)
2 A (10 W)
4 A (20 W)
5 A (25 W)
6 A (20 W)
1 A (3.3 W)
2 A (6.6 W)
4 A (13.2 W)
5 A (16.5 W)
6 A (19.8 W)
1 A (5 W)
1 A (5 W)
1.5 A (7.5 W)
2 A (10 W)
2.5 A (12.5 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.8 A (9.6 W)
% Max Load
Ripple and Noise
The results for this power supply were simply unbelievable, especially when we think that this is supposedly an entry-level power supply. After reviewing a lot of lousy low-end power supplies it is a real joy to see an entry-level model that can not only deliver its rated power at 48° C, but also achieve an outstanding efficiency and a very low ripple and noise levels.
Efficiency is definitely one of the highlights of this product. Corsair says this power supply achieves a maximum 85% efficiency, but they are wrong – in a good way. The only time this power supply achieved efficiency BELOW 85% was when we pulled 450 W from it (84.3%). On all other tests efficiency varied between 86% and 88%. Amazing. Just to put things into perspective other entry-level power supplies can’t even reach 80% efficiency, and the ones that can they don’t reach 85%.
Voltage regulation during all our tests (including the overload tests we will present in the next page) was outstanding, with all outputs within 3% of their nominal voltages – ATX specification defines that all outputs must be within 5% of their nominal voltages – except on -12 V, which was between -11.14 V and -11.42 V, depending on the load pattern. These numbers, however, are still inside the 10% margin that is set by the ATX spec for this output. Of course we always want to see values closer to the nominal voltage.
Noise and ripple was another highlight of this product. Corsair VX450W produces very little noise level, far below the maximum admissible. When we were pulling 450 W from it noise level at +12 V was 29.8 mV, at +5 V was 19.2 mV and at +3.3 V was 13.2 mV, as you can see on the screenshots below (just to remember, the maximum allowed values are 120 mV for +12 V and 50 mV for +5 V and +3.3 V; all these values are peak-to-peak values). We were really impressed by these results.
Now let’s see if we could pull more power from this product.
We were really curious to see how much power this unit could really deliver, because by the project used we suspected it could deliver far more than what was labeled – especially because we had already reviewed Antec EarthWatts 500 W, which uses the same design, and it is not only labeled at 500 W but could deliver up to 577 W.
We tried to see not only the maximum power we could extract from this power supply with it still working inside its specs, but also if all its protections are working correctly. As you know by now, power supplies usually burn when we try pulling more than it is capable of handling if it doesn’t feature overload protection (OLP or OPP; these two acronyms mean the same thing).
Since we were already pulling from the +12 V output almost the maximum our load tester can deliver to this output – 33 amps – we removed the power supply EPS12V connector from +12V1 input and installed it on the +12V2 input from our load tester. Then starting from pattern number five described in the previous page we started increasing current until the power supply turned off. We figured out that if we pulled more than 44 A (528 W) from +12 V (22 A from the motherboard, video card and peripheral cables and 22 A from EPS12V) the power supply wouldn’t turn on. Phew, we were really cold sweating expecting the worst – that this power supply would explode. But since it shut down, we could testify that overload protection was in action, which is terrific.
Then we increased current on +5 V and +3.3 V to see if we could pull even more. Under the current configuration if we pulled more than 7 A from these rails the power supply would shut automatically down.
With this maximum configuration (44 A from +12 V, 7 A from +5 V and 7 A from +3.3 V – i.e., a total of 596 W!) the power supply would turn on and work for around 30 seconds, after that the power supply would shut down due to overload. Isn’t that great to have a power supply with overload protection in action? You can do whatever you want and it doesn’t explode!
We decreased two amps from the +12 V output and we could make our 450 W power supply to work stable at 570 W at 48° C and with 81% efficiency! Holy cow! You can see the summary for this test in the table below.
20 A (240 W)
20 A (240 W)
7 A (35 W)
7 A (23.1 W)
2.5 A (12.5 W)
0.8 A (9.6 W)
% Max Load
Under this test all outputs were within specs and noise level was still very low, 47 mV at +12V1, 58.2 mV at +12V2, 19.2 mV at +5 V and 13.2 mV at +3.3 V. Astonishing.
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines. It seems that over current protection (OCP) is configured with a value far above what is written on the label, as we could pull up to 44 A from the +12 V rail, while the label says the limit is 33 A.
Over load protection (OLP a.k.a. OPP) was in action, shutting down the unit if we pulled more than it could handle, preventing it from burning.When the power supply fan is running slowly it is really quiet, but as soon as it starts spinning at its full speed noise level becomes somewhat high.
Corsair VX450W power supply specs include:
* Researched at Shopping.com on the day we published this review.
If we could summarize this power supply in just one word it would be “wow!.” Together with Antec EarthWatts 500 W this is the best power supply up to 500 W we have ever seen, bringing the best cost/benefit ratio for the average user building a mainstream PC with a good video card, graduating Summa Cum Laude in our tests. You will bring home a relatively inexpensive power supply that even though is sold as being a 450 W unit can deliver up to 570 W at 48° C – in fact Corsair could have easily labeled this power supply as a 500 W unit, but they preferred to stay on the safe side.
This product has a higher price tag than other entry-level power supplies up to 450 W we have recently reviewed, but it is not more expensive. How is that possible? Since it can maintain efficiency above 85% even though you will initially pay a higher price to bring this product home the savings you will have on you electricity bill will compensate the buy in just a few months, especially if you keep your computer turned on for several hours a day.
Comparing Corsair VX450W to other entry-level power supplies we have reviewed recently (the exception goes to Zalman ZM360B-APS) is like comparing the old VW Beetle to the new one. This model from Corsair brings an updated design with active PFC, higher efficiency, lower noise level and the ability to deliver far more than its labeled power and also more cables: six peripheral power cables against four and six SATA power cables cables against four or even two.
As we mentioned, this product is identical to Antec EarthWatts 500 W, but using better capacitors – it was really good to see Japanese capacitors on an entry-level product –, a better-looking housing (black vs. standard grey), a better cooling system (120 mm fan vs. 80 mm fan) and more power plugs (six peripheral power plugs vs. three; six SATA power plugs vs. three). But Antec EarthWatts has as a big advantage coming with two video card power cables. In fact this is the only problem with this product from Corsair: if you want to use two video cards in SLI or CrossFire modes you will need to use an adapter to convert a standard peripheral power plug into a 6-pin auxiliary video card power plug. Being in fact a 570 W product, it can easily feed two video cards.