Corsair TX850 850W 电源评测

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Under the HoodHere are a few pictures showing the layout and [size=1em]components inside the [size=1em]Corsair TX850W [size=1em]power supply.  The overall layout looks quite good with components neatly organized and plenty of open space for good airflow.

Unlike Corsair’s previous HX520/620 and the VX450 power supplies which were built by [size=1em]Seasonic, the TX series is manufactured by Channel Well Technology (CWT) who was also the OEM for the VX550.  CWT has a good reputation in the industry for producing high output [size=1em]power supplies and the TX850 is based on one of CWT’s most popular platforms.  It will be interesting to see how this particular unit tests out and whether or not Corsair has enabled CWT to engineer out a few of the weaknesses that have plagued this platform in the past.

The primary side features a single, large Nippon Chemi-Con electrolytic capacitor rated for 470uF, 450V, and 105°C.  The secondary side also uses high-quality Nippon Chemi-Con caps for reliable service.  Overall, very good choices for capacitor selection; just what we would expect from Corsair!

Note the use of a plastic guard protecting the cable bundle as it exits thru the back of the power supply.  This is a simple feature that is too often overlooked by the majority of power supply manufacturers.

Load Regulation, Line Regulation and Cross-LoadingDC Output Load Regulation

Of course one of the first things we want to see is how well this PSU can regulate the DC outputs and maintain stable voltages.  To simulate real world and maximum loading conditions, the TX850 PSU was connected to the load testers and [size=1em]supplied with a constant 115 VAC.  In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads.  

The ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances now for the +12V outputs.  I have also included a second table of expanded tolerances (±1% to ±6%) for reference.

The following tables list the DC voltage results at the different loads for the TX850 PSU while operating on 115 VAC, 60 Hz.

The PSU produced excellent load regulation on all of the outputs across a broad range of loads.  This is definitely an area where the Corsair branded CWT 850W PSU shows improvement.  The +3.3V and 5V rails stayed easily within +/-2% of the nominal voltage instead of the recommended +/-5% and the +12V rail stayed within +/-1%, even while delivering over 70A – very impressive.

DC Output Line Regulation

In this test we are interested in seeing how well a PSU can maintain the various output voltages while the AC input line voltage changes.  In the previous Load Regulation test, the AC line voltage was held constant at 115 VAC.  Now we will look at how much the DC outputs change as the load is held constant and the AC line voltage is changed from 120 VAC down to 90 VAC.

The Line Regulation test was performed with the combined DC loads set to 675W.  The AC input voltage to the [size=1em]power supply (via the Extech power analyzer) was adjusted using a Powerstat variable autotransformer.  Virtually no measurable change in the DC outputs; very good.  

Cross-Loading Test

PC switching mode [size=1em]power supplies provide multiple DC output voltages.  Ideally, the total load should be distributed across all the main outputs (+3.3V, +5V, +12V).  This means that the combined +3.3V and +5V load should be proportional to the combined +12V load – as one increases, so should the other.  Unfortunately, this is not always the case, especially in newer PCs that predominately use +12V and may put only minimal loads on the +3.3V and/or +5V rails.  

Cross-loading refers to imbalanced loads.  If a PC pulls 400W on the +12V outputs and only 40W (or less) on the combined 3.3V and +5V outputs, the resulting voltage regulation may suffer.

In the first test we put a heavy load (64A) on the +12V output and a light load on the remaining outputs.  The TX850 PSU had no problem delivering 64A on the combined +12V rails.  Even with this large imbalance, the voltages all stayed well within spec.

In the second test we reversed the cross-load and placed a heavy load (136W) on the +3.3V and +5V outputs with a light load (2A/24W) on the +12V rail.  Once again, the PSU passed this test without problems and all the voltages remained in spec.
AC Ripple and Power FactorAC Ripple and Noise on the DC Outputs

The amount of AC ripple and noise present on the DC outputs was checked using an oscilloscope.  This AC component may be present in the KHz range where most [size=1em]switching power supplies operate or it may be more prevalent at the 60 Hz line frequency.  I adjusted the O-scope time base to look for AC ripple at both low and high frequencies.  

The new ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.

Ideally we would like to see no AC ripple (repetitive) or noise (random) on the DC outputs – the cleaner the better!  But in reality there will always be some present.  I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard.  The following table lists the ripple/noise results during all of the load tests for the main output [size=1em]voltages of interest.

The Corsair TX850 power supply exhibited satisfactory AC ripple suppression across the entire load range, even when delivering 850W.  All measurements stayed within the recommended ATX guidelines but they were not as good as many competing models.  This is an area where the CWT platforms have struggled in the past and it appears to be one area that Corsair was not able to significantly correct.  In reality however, the TX850 should perform very well in real-world operation.  (I typically wouldn’t push an 850W PSU beyond about 600W, which is approximately 70% of the max rated capacity).

Power Factor (PF)

Power factor is defined as the ratio of true power (measured in watts) to apparent power (measured in Volt Amps).  It measures how effectively AC power is being used by a device.  The difference between true power and apparent power is expressed as the power factor and results from the way true power and apparent power are measured.  Ideally we would like to have true power and apparent power equal to one another, which would result in a PF of 1.00 or 100% effective power utilization.

AC [size=1em]Volts x AC Amps = VA (Volt Amp)

Purely Resistive AC Load: VA = Watts (same as DC circuits)
Inductive/Reactive AC Load: VA x PF = Watts

AC Volts x AC Amps x PF = Watts

I measured the AC Power Factor with an Extech power analyzer at both 115 VAC and 240 VAC input voltages.  The TX850 power supply uses Active PFC circuits so as expected; the majority of readings were close to 1.0 at full load.  

Note: A power supply with active PFC is more environmentally friendly (doesn’t pollute the AC transmission grid with harmonics) and will draw less current, but it will not save you money on your monthly electric bill unless you are a commercial user whose bill is based on PF and usage.

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Efficiency, Differential Temperature and NoiseEfficiency

The overall efficiency of a [size=1em]power supply is very important, especially when the power supply is designed to deliver over 800W DC output.  The less waste heat generated the better!  Efficiency is defined by the power output divided by the power input and is usually expressed as a percentage.  If a [size=1em]PSU were a 100% efficient (which none are) 600 watts of [size=1em]AC power going in would result in 600 watts of DC power coming out (with no waste heat to dissipate).  In the real world there are always inefficiencies and power is lost in the form of heat during the conversion process.

The latest revisions to the ATX12V Power Supply Design Guide V 2.2 have continued to increase the efficiency recommendations for PC [size=1em]switching mode [size=1em]power supplies and now lists both required and recommended minimum efficiencies.

I measured the AC power input to the Corsair TX850 PSU with the Extech power analyzer while the total DC load was found by adding all the individual +3.3V, +5V, +12V, -12V and +5VSB loads together.  

The overall efficiency of the TX850 power supply is very good and the efficiency appears to peak around 450W.  Note that efficiency will almost always be higher at the 240 VAC line voltage versus 115 VAC (as the voltage goes up the current goes down, and since line/component loses are proportional to current, less current means lower loses.  

(Courtesy Corsair)

80 Plus Program

There is a growing awareness among users, PC manufacturers and electric utilities regarding the money and natural resources that could be saved by adopting higher efficiency [size=1em]PC power supplies.  One group that is spearheading this movement is the 80 Plus Program, which is supported by the electric utilities industry.  You can learn more about their efforts to promote power supplies with better than 80% efficiency by visiting the 80 Plus Program website.

Note 1: Power Factor ≥0.90 (50% to 100% Load)
      Note 2: Tests conducted at room temperature (25°C)

Earlier last year 80 Plus added three new certifications (Bronze, Silver, and Gold) to help differentiate and acknowledge [size=1em]PSUs that meet even higher efficiency specifications. The Corsair TX850 is certified 80 Plus, which means it should produce up to 80% (or higher) efficiency while delivering between a 20% and 100% load.  

Spending a little more money up front to purchase a high efficiency power supply may very well pay for itself over the lifetime of the PC, especially when you are using this much power… :)

Differential Temperature and Noise Levels

To simulate real world operation the TX850 power supply was mounted in a modified mid tower case (Lian Li PC60) during testing.  Some of the warm exhaust air from the PSU under test is recirculated back into the case, which allows the internal case air temperature to increase with load, just like it would in a real PC.  The internal case air temperature is allowed to increase up to 40ºC and then held constant from then on at 40ºC.  

The differential temperature across the power supply was calculated by subtracting the internal case air temperature (T in) from the temperature of the warm exhaust air flowing out the back of the power supply (T out).  

Thermocouples were placed at the air inlet and exhaust outlet. The ambient room air temperature was 23ºC (74ºF) +/- 0.5ºC during testing.

T out = temperature of air exhausting from power supply
T in = temperature of air entering power supply
Delta T = T out - T in

Sound pressure level readings were taken 3’ away from the rear of the case in an otherwise quiet room.  The ambient noise level was ~28 dBA.  

Below 500W output and 30°C inlet air temperature, the Corsair TX850 PSU is relatively quiet.  Temperatures continue to build as the load increases and at the higher loads the cooling fan is speeding up to where it becomes very noticeable but not obnoxious.  Even though this power supply is very efficient, it still has to dissipate approximately 170 watts of heat at max load and the higher exhaust temperatures reflect that.  

Note: I was not able to take SPL readings at the maximum load due to all the programmable DC load cooling fans running.   

(Courtesy Corsair)
Final Thoughts and ConclusionsThe [size=1em]Corsair TX850W [size=1em]power supply delivers solid outputs, with excellent voltage regulation and good efficiency.  Under normal operating conditions (below 600W load) the TX850W is relatively quiet.  The TX850W comes fitted with hard-wired cables that can support dual, high-end video cards.  And let’s not forget active PFC, universal [size=1em]AC input and Corsair’s 5-year warranty!

Overall, most higher-capacity Channel Well Technology built [size=1em]power supplies have proven to be excellent but they have a weakness, which is higher levels of AC ripple on the DC outputs.  While still well within spec, the TX850W continues to exhibit relatively high levels of AC ripple, especially at max load.  In reality however, the TX850 should perform very well in real-world operation.  I typically wouldn’t push an 850W [size=1em]PSU beyond about 600W (which is approximately 70% of the max rated capacity) and at that level the TX850 performs very well.

The Corsair TX850W power supply is currently available and can be found selling for around $129.99 USD.  That is a very competitive price for a strong [size=1em]850W power supply.

Strengths:
•    Up to 850W DC output
•    Solid, stable voltages with excellent voltage regulation
•    Relatively quiet during normal operation (below 600W output)
•    Very good build quality with high quality components
•    Good efficiency along with Active PFC (80 Plus certified)
•    Single +12V output up to 70A (840W)
•    Black mesh sleeved cables
•    Four PCI-E connectors for dual [size=1em]graphic card support
•    Competitive pricing
•    Backed by a 5-year warranty

Weaknesses:
•    Relatively high levels of AC ripple on the DC outputs at max load
•    May be noisy for some at higher loads (above 600W and 30°C)

nfsking2

米不起这个东西，只能帮顶
有时间帮你翻译了~

Travis

PCPer的噪音测试并不是消声室内做的，不能以通常的“25dBA以下为静音”标准去衡量。

Travis

我不知道你有没有在开放环境内用分贝计测量噪音的经验
31dBA很可能已经是他们屋子里本底噪声的下限了

helene

这个网站的测试偏重输出性能，静音不够专业

roger243

老产品了。只不过大陆一直没有上～

毛毛叉

效率粉不错

Travis

10# Elwin

但是他们是在测试环境里有六台电子负载机的前提下做的
电子负载那个风扇啥声音我就不说了……

在评价电源测试的噪音测试之前最好对每个网站的测试平台是啥样子有个了解。
我不是臆断，而是如果他们真的为了噪音测试像Anandtech那样弄了个隔音箱，他们一定会交代。
而且……
http://www.extech.com/instrument/products/400_450/407738.html

如果他们有打算在静音间里做噪音测试，一定不会买Extech 407738这种量程下限也不过25dB的手持式噪音计。