XFX PRO 750 W Black Edition Full Modular Power Supply Review
By Gabriel Torres on December 21, 2012


Introduction

Hardware Secrets Golden Award

XFX is releasing a new series of power supplies with the 80 Plus Gold certification and a fully modular cabling system, with 750 W, 850 W, 1,050 W, and 1,250 W versions, dubbed the PRO Black Edition Full Modular. Be aware that the name “PRO Black Edition” has already been used by XFX for an 80 Plus Bronze power supply series, and the new series has the “Full Modular” words added to its name. (The new models have the letters “BEF” added at the end of their part numbers.) Wouldn’t it be simpler to just use a different name? Anyway, let’s see if the 750 W version deserves our recommendation.

The new XFX PRO Black Edition Full Modular series power supplies are rebranded Seasonic X-Series KM3 units. The latest models within Corsair’s AX series are also based on the same platform.

XFX Pro 750w Black Edition
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Figure 1: XFX PRO 750 W Black Edition Full Modular power supply

XFX Pro 750w Black Edition
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Figure 2: XFX PRO 750 W Black Edition Full Modular power supply

The XFX PRO 750 W Black Edition Full Modular is 6.3” (160 mm) deep. It uses a 120 mm ball-bearing fan on its bottom (ADDA AD1212MB-A70GL; models from Seasonic and Corsair based on the same platform use a fan from Sanyo Denki). The power supply has a “hybrid/normal” switch that allows you to configure the fan to turn on only when the power supply load reaches 30% of the unit’s labeled wattage (i.e., 195 W), so the power supply won’t make any noise when the computer doesn’t demand a lot of power. Under the “hybrid” mode, between 30% and 50% load, the fan will spin at a lower speed, generating lower noise than usual.

XFX Pro 750w Black Edition
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Figure 3: Fan

The modular cabling system from this power supply has 13 connectors: two for the main motherboard power connector, six for video card and ATX12V/EPS12V connectors, and five for peripheral and SATA connectors. This power supply comes with the following cables:

All wires are 18 AWG, which is the minimum recommended gauge.

The number of connectors is adequate for a 750 W power supply, allowing you to install up to two high-end video cards that require two auxiliary power connectors each. This is the same cable configuration found on the Seasonic X-Series KM3 650 W.

XFX Pro 750w Black Edition
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Figure 4: Cables

Let’s now take an in-depth look inside this power supply.

A Look Inside the XFX PRO 750 W Black Edition Full Modular

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.            

On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used.

XFX Pro 750w Black Edition
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Figure 5: Top view

XFX Pro 750w Black Edition
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Figure 6: Front quarter view

XFX Pro 750w Black Edition
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Figure 7: Rear quarter view

XFX Pro 750w Black Edition
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Figure 8: The printed circuit board

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.

In the transient filtering stage, this power supply is flawless.

XFX Pro 750w Black Edition
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Figure 9: Transient filtering stage (part 1)

XFX Pro 750w Black Edition
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Figure 10: Transient filtering stage (part 2)

On the next page, we will have a more detailed discussion about the components used in the XFX PRO 750 W Black Edition Full Modular.

Primary Analysis

On this page, we will take an in-depth look at the primary stage of the XFX PRO 750 W Black Edition Full Modular. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.         

This power supply uses two GBJ1506 rectifying bridges, which are attached to an individual heatsink. Each bridge supports up to 15 A at 100° C. In theory, you would be able to pull up to 3,450 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 2,760 W without burning themselves out (or 3,105 W at 90% efficiency). Of course, we are only talking about these particular components. The real limit will depend on all the components combined in this power supply. These are the same components used on the Seasonic X-Series KM3 650 W and the Corsair AX760.  

XFX Pro 750w Black Edition
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Figure 11: Rectifying bridges

The active PFC circuit uses two IPP50R250CP MOSFETs, each one supporting up to 13 A at 25° C or 9 A at 100° C in continuous mode (note the difference temperature makes), or 31 A at 25° C in pulse mode. These transistors present a 250 mΩ maximum resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency. The Seasonic X-Series KM3 650 W and the Corsair AX760 use slightly different models here, with a little lower current limit.

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Figure 12: The active PFC diode and transistors

The active PFC circuit is controlled by an NCP1654 integrated circuit.  

XFX Pro 750w Black Edition
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Figure 13: Active PFC controller

The output of the active PFC circuit is filtered by two 270 μF x 420 V Japanese electrolytic capacitors, from Hitachi, labeled at 105° C. These capacitors are connected in parallel and are the equivalent of a single 540 μF x 420 V capacitor. The Seasonic X-Series KM3 650 W uses two 220 μF x 420 V capacitors, and the Corsair AX760 uses two 330 μF x 420 V capacitors here.

XFX Pro 750w Black Edition
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Figure 14: Capacitors

In the switching section, four IPP50R399CP MOSFETs are employed using a full-bridge, resonant configuration. Each transistor supports up to 9 A at 25° C or 6 A at 100° C in continuous mode or up to 20 A at 25° C in pulse mode, with a maximum RDS(on) of 399 mΩ. These are the same transistors used in the Seasonic X-Series KM3 650 W. The Corsair AX760 uses more powerful transistors here.  

XFX Pro 750w Black Edition
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Figure 15: The switching transistors

The switching transistors are controlled by a CM6901 resonant controller, which is physically located on the same printed circuit board as the +12 V transistors.

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Figure 16: Resonant controller

Let’s now take a look at the secondary of this power supply.

Secondary Analysis

As one would expect in a high-efficiency power supply, the XFX PRO 750 W Black Edition Full Modular uses a synchronous design, where the Schottky rectifiers are replaced with MOSFETs. Also, the reviewed product uses a DC-DC design in its secondary. This means that the power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs produced by two smaller power supplies connected to the main +12 V rail. Both designs are used to increase efficiency.

The +12 V output uses four PSMN2R6-40YS MOSFETs, each one supporting up to 100 A at 100° C in continuous mode, or up to 651 A at 25° C in pulse mode, with a maximum RDS(on) of 3.7 mΩ. This is the same configuration used in the Corsair AX760. The Seasonic X-Series KM3 650 W uses only two of these transistors.  

XFX Pro 750w Black Edition
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Figure 17: The +12 V transistors

As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters, which are located on the same printed circuit board as the modular cabling system. The two converters are controlled by the same PWM controller, an APW7159, and each output makes use of three BSC0906NS MOSFETs, each one supporting up to 63 A at 25° C or 50 A at 100° C in continuous mode and up to 252 A at 25° C in pulse mode, with a maximum RDS(on) of 4.5 mΩ. This is exactly the same configuration used in the Corsair AX760 and in the Seasonic X-Series KM3 650 W. 

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Figure 18: The DC-DC converters

XFX Pro 750w Black Edition
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Figure 19: The DC-DC converters

The outputs of the power supply are monitored by a WT7527 integrated circuit, which supports over voltage (OVP), under voltage (UVP), and over current (OCP) protections. There are four OCP channels, one for +3.3 V, one for +5 V, and two for +12 V. The manufacturer, however, decided to use only one of the +12 V channels available, resulting in this unit having a single +12 V rail. 

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Figure 20: Monitoring circuit

This power supply uses a mix of solid and electrolytic capacitors in its secondary. The electrolytic capacitors are also Japanese, from Chemi-Con, and labeled at 105° C, as usual.

XFX Pro 750w Black Edition
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Figure 21: Capacitors

The +5VSB Power Supply

The +5VSB (a.k.a. standby) power supply is independent of the main power supply, since it is on continuously.

The +5VSB power supply uses an ICE2QR4765 integrated circuit, which incorporates the PWM controller and the switching transistor into a single chip.  

XFX Pro 750w Black Edition
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Figure 22: The +5VSB integrated circuit with an integrated switching transistor

The rectification of the +5VSB output is performed by an SBR30A40CT Schottky rectifier, which supports up to 30 A (15 A per internal diode at 110° C, 0.50 V maximum voltage drop).

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Figure 23: The +5VSB rectifier

Power Distribution

In Figure 24, you can see the power supply label containing all the power specs.

XFX Pro 750w Black Edition
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Figure 24: Power supply label

As you can see, this unit has a single +12 V rail configuration.

Let’s find out how much power this unit can deliver.

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 the behavior of the reviewed unit 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 powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (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. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, the +12VA and +12VB inputs were connected to the power supply’s single +12 V rail. (The +12VB input was connected to the power supply EPS12V connector.)

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

5.5 A (66 W)

11.5 A (138 W)

17 A (204 W)

22.5 A (270 W)

27.5 A (330 W)

+12VB

5.5 A (66 W)

11 A (132 W)

16.5 A (198 W)

22 A (264 W)

27.25 A (327 W)

+5 V

1 A (5 W)

2 A (10 W)

4 A (20 W)

6 A (30 W)

8 A (40 W)

+3.3 V

1 A (3.3 W)

2 A (6.6 W)

4 A (13.2 W)

6 A (19.8 W)

8 A (26.4 W)

+5VSB

1 A (5 W)

1.5 A (7.5 W)

2 A (10 W)

2.5 A (12.5 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

152.5 W

302.3 W

453.3 W

603.4 W

748.4 W

% Max Load

20.3%

40.3%

60.4%

80.5%

99.8%

Room Temp.

46.9° C

45.9° C

46.1° C

47.6° C

45.0° C

PSU Temp.

48.7° C

49.0° C

49.5° C

50.4° C

50.0° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

167.7 W

328.9 W

497.2 W

671.0 W

841.0 W

Efficiency

90.9%

91.9%

91.2%

89.9%

89.0%

AC Voltage

118.6 V

117.0 V

115.5 V

113.7 V

112.2 V

Power Factor

0.994

0.989

0.994

0.995

0.996

Final Result

Pass

Pass

Pass

Pass

Pass

The XFX PRO 750 W Black Edition Full Modular presented outstanding efficiency, way above the minimum set by the 80 Plus Gold certification. The 80 Plus Gold certification promises efficiency of at least 87% under light (i.e., 20%) load, 90% under typical (i.e., 50%) load, and 87% under full (i.e., 100%) load. In fact, the results achieved by this power supply would qualify it as an 80 Plus Platinum certification!

Let’s discuss voltage regulation on the next page.

Voltage Regulation Tests

The ATX12V specification states that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values. We consider a power supply as “flawless” if it shows voltages within 3% of its nominal values. In the table below, you can see the power supply voltages during our tests and, in the following table, the deviation, in percentage, of their nominal values.

The XFX PRO 750 W Black Edition Full Modular presented outstanding voltage regulation. Seasonic promises 2% voltage regulation for its KM3 platform, but the maximum deviation we saw was 1.20%!

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

+12.12 V

+12.12 V

+12.08 V

+12.06 V

+12.04 V

+12VB

+12.13 V

+12.10 V

+12.05 V

+12.01 V

+11.97 V

+5 V

+5.03 V

+5.02 V

+5.01 V

+5.01 V

+5.00 V

+3.3 V

+3.33 V

+3.31 V

+3.31 V

+3.30 V

+3.30 V

+5VSB

+5.06 V

+5.03 V

+5.00 V

+4.97 V

+4.94 V

-12 V

-11.50 V

-11.63 V

-11.77 V

-11.95 V

-12.11 V


Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

1.00%

1.00%

0.67%

0.50%

0.33%

+12VB

1.08%

0.83%

0.42%

0.08%

-0.25%

+5 V

0.60%

0.40%

0.20%

0.20%

0.00%

+3.3 V

0.91%

0.30%

0.30%

0.00%

0.00%

+5VSB

1.20%

0.60%

0.00%

-0.60%

-1.20%

-12 V

4.35%

3.18%

1.95%

0.42%

-0.91%

Let’s discuss the ripple and noise levels on the next page.

Ripple and Noise Tests

Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed  are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.

The XFX PRO 750 W Black Edition Full Modular provided extremely low ripple and noise levels, as you can see in the table below.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

19.2 mV

22.6 mV

25.8 mV

28.8 mV

34.2 mV

+12VB

19.6 mV

24.6 mV

27.0 mV

32.8 mV

37.0 mV

+5 V

10.4 mV

11.0 mV

12.2 mV

12.4 mV

14.4 mV

+3.3 V

10.2 mV

10.8 mV

12.2 mV

14.4 mV

15.4 mV

+5VSB

12.4 mV

6.6 mV

7.6 mV

8.0 mV

9.6 mV

-12 V

18.6 mV

22.2 mV

22.8 mV

26.8 mV

34.2 mV

Below you can see the waveforms of the outputs during test five.

XFX Pro 750w Black Edition
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Figure 25: +12VA input from load tester during test five at 748.4 W (34.2 mV)

XFX Pro 750w Black Edition
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Figure 26: +12VB input from load tester during test five at 748.4 W (37.0 mV)

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Figure 27: +5V rail during test five at 748.4 W (14.4 mV)

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Figure 28: +3.3 V rail during test five at 748.4 W (15.4 mV)

Let’s see if we can pull more than 750 W from this unit.

Overload Tests

Below you can see the maximum we could pull from this power supply. The objective of this test is to see if the power supply has its protection circuits working properly. This unit passed this test, since it shut down when we tried to pull more than what is listed below. During this test, noise and ripple levels were still extremely low, with all outputs still within their tighter-than-usual range.

Input

Overload Test

+12VA

32 A (384 W)

+12VB

32 A (384 W)

+5 V

20 A (100 W)

+3.3 V

20 A (66 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

951.4 W

% Max Load

126.9%

Room Temp.

48.8° C

PSU Temp.

52.7° C

AC Power

1,128 W

Efficiency

84.3%

AC Voltage

108.6 V

Power Factor

0.997

Main Specifications

The main specifications for the XFX PRO 750 W Black Edition Full Modular power supply include:

Conclusions

The XFX PRO 750 W Black Edition Full Modular is another flawless power supply manufactured by Seasonic, targeted to users who demand only “the best.” Its efficiency surpassed the numbers promised by the 80 Plus Gold certification and, in fact, this unit qualified for the 80 Plus Platinum certification. Noise and ripple levels were very low, and voltage regulation was outstanding, with the main positive voltages (+12 V, +5 V, and +3.3 V) within 1.2% of their nominal values. The ATX12V specification allows a 5% deviation, and we usually consider units with 3% voltage regulation as “flawless.”

Other highlights of the XFX PRO 750 W Black Edition Full Modular include the fully modular cabling system and the semi-passive mode of operation, where you can configure the power supply to turn on its fan only when you pull above 30% of its labeled wattage, and at low speed between 30% and 50% load, thereby making the power supply silent when the computer is not demanding a lot of power.

The price is more than right; the suggested price is lower than that of the Seasonic X-Series KM3 750 W, which this unit is a clone of.

The only constructive criticism we have is regarding the name of this power supply. We think it is really confusing to have power supplies with different characteristics and different levels of 80 Plus certification using the same name.

Originally at http://www.hardwaresecrets.com/article/XFX-PRO-750-W-Black-Edition-Full-Modular-Power-Supply-Review/1695


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