Corsair TX950W Power Supply Review
By Gabriel Torres on October 23, 2009


Introduction

Hardware Secrets Golden Award

The latest power supply from Corsair, TX950W, is a single-rail power supply featuring a DC-DC converter on its secondary, which is the preferred design to achieve high-efficiency nowadays. Differently from models from HX series, TX950W does not have a modular cabling system. Let’s see whether this is a good power supply or not.

TX950W, like other members from TX series, is manufactured by CWT, but other TX models do not use DC-DC converters on the secondary and thus achieve lower efficiency. CWT is also the manufacturer behind models from 750 W and up from Corsair HX series (also using DC-DC converters on the secondary), but other members from HX series are manufactured by Seasonic.

Corsair TX950W power supply
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Figure 1: Corsair TX950W power supply.

Corsair TX950W power supply
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Figure 2: Corsair TX950W power supply.

Corsair TX950W isn’t a long power supply, being 6 19/64” (160 mm) deep, using a 140 mm fan on its bottom and featuring active PFC, of course. As mentioned TX950W doesn’t have a modular cabling, and all cables have a nylon protection that comes from inside the unit.

This power supply comes with the following cables:

The cable configuration from TX950W is perfect for a 950 W product: all cables are very long (23 5/8” or 60 cm between the power supply housing and the first connector on the cable; 5 7/8” or 15 cm between connectors), allowing you to easily install it inside a full-tower case; six video card connectors using individual cables, allowing you to have up to three high-end video cards inside your PC; and a terrific number of SATA and peripheral power connectors.

Since it is a 950 W product, it would be even better if it came with eight video card power connectors in order to allow you to install up to four high-end video cards. On the other hand, since this unit does not feature a modular cabling system and most users won’t have four video cards, these extra cables would be hanging inside the case, blocking airflow.

All cables use 18 AWG wires, except the wires on the main motherboard cable, where the wires are thicker (16 AWG), which is great.

Corsair TX950W power supply
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Figure 3: Cables.

Now let’s take an in-depth look inside this power supply.

A Look Inside The Corsair TX950W

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. The first thing that caught our attention was that all capacitors used are Japanese from Chemi-Con and the secondary filtering stage uses some solid capacitors.

Corsair TX950W power supply
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Figure 4: Overall look.

Corsair TX950W power supply
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Figure 5: Overall look.

Corsair TX950W power supply
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Figure 6: Overall look.

Transient Filtering Stage

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.

On this power supply this stage is flawless: it has one ferrite coil, one X capacitor and four Y capacitors more than the minimum required.

Corsair TX950W power supply
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Figure 7: Transient filtering stage (part 1).

Corsair TX950W power supply
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Figure 8: Transient filtering stage (part 2).

In the next page we will have a more detailed discussion about the components used in the Corsair TX950W.

Primary Analysis

On this page we will take an in-depth look at the primary stage of Corsair TX950W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two GBU1506 rectifying bridges connected in parallel. Each bridge supports up to 15 A at 100° C, if a heatsink is used, which is the case. So in theory you would be able to pull up to 3,450 W from the power grid; assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning them. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply.

Corsair TX950W power supply
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Figure 9: Rectifying bridges.

The active PFC circuit uses two SPW35N60C3 power MOSFET transistors. Each MOSFET is capable of delivering up to 34.6 A at 25° C or 21.9 A at 100° C in continuous mode (note the difference temperature makes) or 103.8 A in pulse mode at 25° C. These transistors present a 100 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistors will waste less power and the power supply will achieve a higher efficiency.

Corsair TX950W power supply
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Figure 10: Active PFC transistors.

The electrolytic capacitor in charge of filtering the output from the active PFC circuit is Japanese from Chemi-Con and is labeled at 105° C. This is good for two reasons, first, Japanese capacitors do not leak; and second, usually manufacturers use 85° C capacitors here, so it is good to see a manufacturer using a capacitor with a higher temperature rating.

In the switching section, two SPW20N60C3 power MOSFET transistors are used on the traditional two-transistor forward configuration. Each transistor supports up to 20.7 A at 25° C or 13.1 A at 100° C (note the difference temperature makes) or 62.1 A in pulse mode at 25° C, presenting an RDS(on) of 190 mΩ.

Corsair TX950W power supply
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Figure 11: Switching transistors.

This power supply uses the famous CM6800 active PFC/PWM combo controller.

Corsair TX950W power supply
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Figure 12: Active PFC/PWM combo controller.

Now let’s take a look at the secondary of this power supply.

Secondary Analysis

This power supply uses a synchronous design on its secondary, meaning that instead of using Schottky rectifiers it uses MOSFET transistors. These transistors generate the +12 V output. The +5 V and +3.3 V outputs are generated through DC-DC converters connected to the +12 V output. These DC-DC converters are located in two daughterboards present on the secondary.

TX950W has five IPA057N08N3 MOSFETs, each one capable of delivering up to 60 A at 25° C or up to 43 A at 100° C in continuous mode, or up to 240 A at 25° C in pulse mode, presenting an RDS(on) of only 5.7 mΩ, which is terrific (a low RDS(on) means that lower power is wasted and thus efficiency is higher).

Corsair TX950W power supply
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Figure 13: Transistors in charge of the rectification.

Each DC-DC converter uses solid aluminum caps and one APW7073 controller and four STD60N3LH5 MOSFETs, each one able to handle up to 48 A at 25° C or 42.8 A at 100° C in continuous mode, or up to 192 A at 25° C at pulse mode with an RDS(on) of only 8 mΩ.

Corsair TX950W power supply
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Figure 14: One of the DC-DC converters.

Corsair TX950W power supply
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Figure 15: One of the DC-DC converters.

This power supply uses a PS229 monitoring integrated circuit, which is in charge of the power supply protections. Unfortunately the manufacturer from this component does not publish the datasheet for this integrated circuit, so we couldn’t check what protections it really supports.

Corsair TX950W power supply
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Figure 16: Monitoring circuit.

Electrolytic capacitors from the secondary are also Japanese, from Chemi-Con and labeled at 105° C, with some of them being solid.

Power Distribution

In Figure 17, you can see the power supply label containing all the power specs.

Corsair TX950W power supply
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Figure 17: Power supply label.

This power supply uses a single-rail design, so there is not much to talk about here.

Now let’s see if this power supply can really deliver 950 W.

Load Tests

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.

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.

The +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester. During this test both were connected to the single +12 V rail from this power supply.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12V1

7 A (84 W)

14 A (168 W)

21 A (252 W)

28 A (336 W)

32 A (384 W)

+12V2

7 A (84 W)

14 A (168 W)

21 A (252 W)

28 A (336 W)

32 A (384 W)

+5V

2 A (10 W)

4 A (20 W)

6 A (30 W)

8 A (40 W)

19 A (95 W)

+3.3 V

2 A (6.6 W)

4 A (13.2 W)

6 A (19.8 W)

8 A (26.4 W)

19 A (62.7 W)

+5VSB

1 A (5 W)

2 A (10 W)

2 A (10 W)

3 A (15 W)

3 A (15 W)

-12 V

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

Total

197.7 W

388.8 W

579.1 W

762.8 W

945.8 W

% Max Load

20.8%

40.9%

61.0%

80.3%

99.6%

Room Temp.

45.5° C

46.5° C

48.2° C

48.2° C

48.6° C

PSU Temp.

48.4° C

51.1° C

52.0° C

53.8° C

55.3° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

225.4 W

437.4 W

652.0 W

885.0 W

1145.0 W

Efficiency

87.7%

88.9%

88.8%

86.2%

82.6%

AC Voltage

113.7 V

112.2 V

110.3 V

107.0 V

102.6 V

Power Factor

0.983

0.993

0.996

0.997

0.998

Final Result

Pass

Pass

Pass

Pass

Pass

 

Corsair TX950W can really deliver 950 W at almost 50° C.

Efficiency was very high in all load patterns (between 86% and 88.9%, as you can see on the table above) except during test five, where it dropped to 82.6%. Keeping high efficiency at a high load like 950 W is not an easy task.

There is one important detail to keep in mind. For the test five we were limited by our load tester and we could not pull more current from its +12 V inputs as we’d like to (we had to pull more current from +3.3 V and +5 V than we usually do in order to achieve 950 W), and this different pattern may have contributed to this lower efficiency.

This unit is 80 Plus Silver certified, but Corsair decided to label it as an 80 Plus Bronze model because of the ridiculously low temperature Ecos Consulting, the company behind the 80 Plus certification, tests power supplies (23° C, which is impossible to be achieved inside a PC, especially a high-end one that will get a 950 W power supply). Since we test power supplies at a temperature between 45° C and 50° C, this explains why in our reviews efficiency is always lower than the one found on 80 Plus reports (the higher the temperature, the lower efficiency is).

As you can see, in our tests Corsair TX750W would fail on our own way to test for the 80 Plus Silver certification (85% minimum efficiency at full load) but it passes the 80 Plus Bronze certification (82% minimum efficiency at full load). As you can clearly see, Corsair agrees with us and this is not the first time we’ve seen Corsair downgrading an 80 Plus certification because they don’t feel comfortable with the results. In a world full of companies trying to illude consumers, it is amazing to find a company doing the opposite. Kudos to Corsair.

Voltage regulation was very good, with all voltages inside 3% of their nominal values during testes one through four(i.e., voltages were closer to their nominal value than needed, as ATX spec allows voltages to be up to 5% from their nominal values, 10% for -12 V). This includes the -12 V output, which usually doesn’t like to stay within a tolerance this tight. During test five +5 V and +3.3 V outputs were outside this tighter range but still inside the allowed margin (5%), probably due to the different load pattern we had to use, as explained.

And finally we have noise and ripple, which were low all the time. Below you can see the results for test number five. As we always point out, the limits are 120 mV for +12 V and 50 mV for +5 V and +3.3 V and all numbers are peak-to-peak figures.

Corsair TX950W power supply
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Figure 18: +12V1 input from load tester at 945.8 W (60.6 mV).

Corsair TX950W power supply
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Figure 19: +12V2 input from load tester at 945.8 W (55.6 mV).

Corsair TX950W power supply
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Figure 20: +5V rail with power supply delivering 945.8 W (11.8 mV).

Corsair TX950W power supply
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Figure 21: +3.3 V rail with power supply delivering 945.8 W (14.6 mV).

Now let’s see if we could pull more than 950 W from this unit.

Overload Tests

Below you can see the maximum we could pull from this power supply with it still working within specs. If we tried to pull more than that the unit would shut down, showing that one of the power supply protections entered in action.

Input

Maximum

+12V1

32 A (384 W)

+12V2

32 A (384 W)

+5V

25 A (125 W)

+3.3 V

25 A (82.5 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

990.5 W

% Max Load

104.5%

Room Temp.

45.6° C

PSU Temp.

55.1° C

AC Power

1,227 W

Efficiency

80.9%

AC Voltage

102.3 V

Power Factor

0.998

Main Specifications

Corsair TX950W power supply specs include:

* Researched at Newegg.com on the day we published this review.

Conclusions

Corsair TX950W is an excellent 950 W unit, producing a very high efficiency of practically 89% when delivering between 40% and 60% of this labeled load (between 380 W and 570 W). When delivering 950 W, however, efficiency dropped to around 83%.

This unit received from Ecos Consulting the 80 Plus Silver certification, however Corsair decided to downgrade this product to 80 Plus Bronze, since efficiency at full load drops below the 85% mark when the power supply is operating under real-world temperatures. It seems that Corsair, like us, doesn’t agree with the methodology from Ecos Consulting of measuring power supplies at a room temperature of only 23° C, which is impossible to be achieved inside a PC, especially one demanding a 950 W unit. In a market full of companies trying to deceive consumers, it is a blessing to see a company like Corsair going on the opposite direction. So we have to congratulate Corsair for being such an honest company (we think this should be the rule but unfortunately is the exception).

All voltages were within a tighter 3% margin while ATX specification allows a 5% margin, meaning that all voltages – including -12 V – were closer to their nominal values than necessary. The exception was when the unit was delivering 950 W, when +3.3 V and +5 V outputs got out of this tighter margin, but they were still inside the maximum allowed.

Noise and ripple were low at all timess.

The number of cables is perfect for a 950 W unit, with six six/eight-pin connectors for video cards using individual cables, allowing you to install up to three very high-end video cards without the need for adapters, twelve SATA power connectors and nine peripheral power connectors.

And then we have pricing. This unit costs USD 180 at Newegg.com (several other stores are carrying it for only USD 165), which we think is a terrific price for a 950 W power supply with these features and performance.

Originally at http://www.hardwaresecrets.com/article/Corsair-TX950W-Power-Supply-Review/846


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