XFX PRO 750 W Power Supply Review

[nextpage title=”Introduction”]

XFX is releasing their PRO series of power supplies, with single +12 V rail, DC-DC secondary design, and 80 Plus Bronze certification. So far three models were released: 650 W, 750 W, and 850 W. We have already tested the 650 W model, which proved to have a terrific cost/benefit ratio. Let’s see if the 750 W model follows the same path.

Like other power supplies from XFX, members of the Pro series are manufactured by Seasonic.

Figure 1: XFX PRO 750 W power supply

Figure 2: XFX PRO 750 W power supply

Like the PRO 650W, the PRO 750 W is 6.7” (170 mm) deep, with a 135 mm dual ball bearing fan (ADDA ADN512UB-A90) on its bottom part.

The new XFX PRO 750 W doesn’t have a modular cabling system. All cables are protected with nylon sleeves. The power supply comes with the following cables:

• Main motherboard cable with a 20/24-pin connector, 22.4” (57 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 24” (61 cm) long
• Two cables with one six-pin connector for video cards each, 22.8” (58 cm) long
• Two cables with one six/eight-pin connector for video cards each, 22.8” (58 cm) long
• Two cables with four SATA power connectors each, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors
• One cable with four standard peripheral power connectors, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors
• One cable with three standard peripheral power connectors and one floppy disk drive power connector, 15” (38 cm) to the first connector, 5.9” (15 cm) between connectors

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

This is the same cable configuration found on the 650 W model, and is adequate for a 750 W unit.

Figure 3: Cables

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

[nextpage title=”A Look Inside The XFX PRO 750 W”]

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. The printed circuit board used by the PRO 750 W is identical to the one used by the PRO 650 W.

Figure 4: Top view

Figure 5: Front quarter view

Figure 6: Rear quarter view

Figure 7: Printed circuit board

[nextpage title=”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. 

The transient filtering stage of the XFX PRO 750 W is impeccable, coming with all required components plus one extra X capacitor and four extra Y capacitors.

Figure 8: Transient filtering stage (part 1)

Figure 9: Transient filtering stage (part 2)

In the next page we will have a more detailed discussion about the components used in the XFX PRO 750 W.

[nextpage title=”Primary Analysis”]

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

This power supply uses two GBU806 rectifying bridges connected in parallel, attached to an individual heatsink. Each bridge supports up to 8 A at 100° C so, in theory, you would be able to pull up to 1,840 W from a 115 V power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,472 W without burning themselves out. Of course, we are only talking about these components, and the real limit will depend on all the other components in this power supply. The 650 W model uses two 6 A bridges here.

Figure 10: Rectifying bridges

The active PFC circuit uses two SPP24N60C3 MOSFETs, which are capable of delivering up to 24.3 A at 25° C or up to 15.4 A at 100° C (note the difference temperature makes) in continuous mode, or up to 72.9 A in pulse mode at 25° C, each. These transistors p
resent a 160 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. It is interesting to note how, in order to improve thermal dissipation, the manufacturer added a metallic plate between these transistors and the aluminum heatsink (see Figure 11). These transistors are more powerful than the ones used in the 650 W model.

Figure 11: Active PFC transistors

This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board. The XFX PRO 750 W uses one 220 µF x 400 V and one 330 x 400 V capacitors connected in parallel; this is the equivalent of one 550 µF x 400 V capacitor. These capacitors are Japanese, from Rubycon, and labeled at 105° C. The 650 W model uses two 220 µF x 400 V capacitors here.

In the switching section, two SPP20N60C3 MOSFET transistors are used, installed in the two-transistor forward configuration. Each one is capable of delivering up to 20.7 A at 25° C or up to 13.1 A at 100° C (note the difference temperature makes) in continuous mode, or up to 62.1 A in pulse mode at 25° C, each. These transistors present a 190 mΩ RDS(on). These are the same transistors used in the 650 W model.

Figure 12: One of the switching transistors

The primary is controlled by a CM6802 active PFC/PWM combo controller.

Figure 13: Active PFC/PWM combo controller

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

[nextpage title=”Secondary Analysis”]

This power supply uses a DC-DC project in its secondary, meaning that this unit is basically a +12 V power supply. The +5 V and +3.3 V outputs are produced by two smaller switching power supplies connected to the +12 V rail. This design is used to increase efficiency.

The +12 V output make use of five SBR30A50CT Schottky rectifiers, each one capable of handling up to 30 A (15 A per internal diode at 110° C, 0.55 V maximum voltage drop). From the ten available diodes (two per rectifier pack), four are used in the direct rectification and six are used in the “freewheeling” part of the rectification. The 650 W model uses four of these rectifiers.

Figure 14: +12 V rectifiers

As explained, the +5 V and +3.3 V outputs are generated using two DC-DC converters (i.e., two switching power supplies). Usually power supplies using this design have these two converters installed on separate daughterboards, but in the XFX PRO 750 W they are available on the same board, shown in Figures 15 and 16. The two converters are managed by the same PWM chip (APW7159), and use seven APM2556N MOSFET transistors, each one being able to handle up to 160 A at 25° C or 90 A at 100° C with an RDS(on) of only 4.5 mΩ. The DC-DC converter board is identical to the one used in the PRO 650 W.

Figure 15: The +5 V and +3.3 V DC-DC converter

Figure 16: The +5 V and +3.3 V DC-DC converter

The secondary is monitored by a PS223 integrated circuit, which supports over voltage protection (OVP), under voltage protection (UVP), over current protection (OCP), and over temperature protection (OTP). This integrated circuit has four OCP channels (+3.3 V, +5V and two +12 V), but the manufacturer decided to use only one of the +12 V channels, making this a single-rail power supply.

Figure 17: Monitoring circuit

All electrolytic capacitors used in the secondary are also Japanese, from Chemi-Con, and labeled at 105° C.

[nextpage title=”Power Distribution”]

In Figure 18, you can see the power supply label containing all the power specs.

Figure 18: Power supply label

Since this unit has a single +12 V rail, there is not much to talk about here.

Let’s now see if this power supply can really deliver 750 W.

[nextpage title=”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 our tests, the +12VA and +12VB input were connected to the power supply single +12 V rail (the EPS12V connector was installed on the +12VB input of our load tester).

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	5 A (60 W)	11 A (132 W)	16 A (192 W)	22 A (264 W)	27 A (324 W)
+12VB	5 A (60 W)	10 A (120 W)	16 A (192 W)	21 A (252 W)	27 A (324 W)
+5V	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)	10 A (50 W)
+3.3 V	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	8 A (26.4 W)	10 A (33 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	149.1 W	313.1 W	452.3 W	614.8 W	751.1 W
% Max Load	19.9%	41.7%	60.3%	82.0%	100.1%
Room Temp.	45.5° C	45.3° C	46.9° C	45.5° C	48.8° C
PSU Temp.	44.8° C	45.3° C	46.3° C	48.5° C	49.9° C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	176.7 W	363.4 W	529.8 W	732.0 W	919.0 W
Efficiency	84.4%	86.2%	85.4%	84.0%	81.7%
AC Voltage	113.4 V	111.5 V	107.6 V	105.2 V	103.0 V
Power Factor	0.979	0.989	0.994	0.997	0.997
Final Result	Pass	Pass	Pass	Pass	Pass

The XFX PRO 750 W passed our test with flying colors, being able to deliver its labeled wattage at high temperatures.

Efficiency was very good, between 81.7% and 86.2%. The 80 Plus Bronze certification requires a minimum 82% efficiency at light (20%) and full loads, and this unit presented 81.7% efficiency at full load. This happens because the 80 Plus tests are conducted at 23° C, while ours were done between 45° C and 49° C, and efficiency drops with temperature. But this value was close enough of the advertised efficiency.

Voltage regulation was superb, with all voltages within 3% of their nominal values, including the -12 V output. The ATX12V specification allows voltages to be up to 5% from their nominal values (10% for the -12 V output). Therefore this power supply presents voltages closer to their nominal values than necessary all the time.

Noise and ripple levels were always extremely low. Below you can see the results for the power supply outputs during test number five. The maximum allowed is 120 mV for the +12 V and -12 V outputs, and 50 mV for the +5 V, +3.3 V, and +5VSB outputs. All values are peak-to-peak figures.

Figure 19: +12VA input from load tester during test five at 751.1 W (23.6 mV)

Figure 20: +12VB input from load tester during test five at 751.1 W (36.8 mV)

Figure 21: +5V rail during test five at 751.1 W (10.6 mV)

Figure 22: +3.3 V rail during test five at 751.1 W (12.2 mV)

Let’s see if we can pull even more from the XFX PRO 750 W.

[nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. We couldn’t pull more than that because the power supply shut down, showing that its protections are working just fine.

Input	Overload Test
+12VA	33 A (396 W)
+12VB	33 A (396 W)
+5V	14 A (70 W)
+3.3 V	14 A (46.2 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	931.2 W
% Max Load	124.2%
Room Temp.	47.4° C
PSU Temp.	50.2° C
AC Power	1,168 W
Efficiency	79.7%
AC Voltage	102.2 V
Power Factor	0.998

[nextpage title=”Main Specifications”]

The specs of the XFX PRO 750 W include:

• Standards: ATX12V and EPS12V (exact versions not informed)
• Nominal labeled power: 750 W
• Measured maximum power: 931.2 W at 47.4° C ambient
• Labeled efficiency: Up to 85%, 80 Plus Bronze certification
• Measured efficiency: Between 81.7% and 86.2% at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: No
• Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector
• Video Card Power Connectors: Two six-pin connectors and two six/eight-pin connectors on separate cables
• SATA Power Connectors: Eight on two cables
• Peripheral Power Connectors: Seven on two cables
• Floppy Disk Drive Power Connectors: One
• Protections (as listed by the manufacturer): Over power (OPP), over voltage (OVP), over current (OCP), over temperature (OTP), and short-circuit (SCP)
• Are the above protections really available? Yes, under voltage protection (UVP) present but not listed by the manufacturer
• Warranty: Five years
• Real Manufacturer: Seasonic
• More Information: https://www.xfxforce.com
• Average Price in the US*: USD 120.00 (USD 100 after a mail-in rebate)

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

[nextpage title=”Conclusions”]

The XFX PRO 750 W is a decent power supply, clearly targeted to users that want good 750 W unit at an affordable price. It passed our tests with flying colors, with good efficiency, outstanding voltage regulation, ultra-low noise and ripple levels, and good cable configuration.

Pay attention because you will need to apply for a mail-in
rebate to make this unit cost you USD 100, which is a terrific price for what this unit offers.