ocaholic - PSUs > XFX ProSeries 1250W PSU Review

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Preview

Page 2 - Preview

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Delivery and Specifications

Delivery
Cable	Length
1 x ATX 20+4 pin	60 cm
2 x EPS/ATX 12V 8 & 4+4 pin	65 cm
8 x PCI-E 6+2 pin	60 cm
1x2 + 3x3 SATA	55, 90 cm
1x2 + 2x3 Molex + 1 x 2 Floppy	55, 90 cm

The delivery of the P1-1250-BEFX is adequate. Since PSUs with this kind of output power are often used for PCs with five or more graphics cards, it would have been nice if XFX added another pair of PCI-E 6+2 Pin cables, which can be connected to the EPS/ATX 12V 8Pin connector.

The design is based on one single 12V rail with a whopping 104A. However this 12V rail is then splitted into four rails for distribution. The four rails are then OCP protected induvidually. In our opinion it is good that the manufacturer splitted the rail (for security reasons) but it would been even better if XFX mentions it somewhere in the descriptions.
Aditionally we think, that the four Rails are too heavily OCP protected. Even with normal usage (within the specs) it could be that this device goes into OCP status (for example: a 45A Rail providing four PCIe 8Pin - with two Radeon HD 6990 cards on them this rail would go OCP). It's very sad that XFX does not provide the correct information at this point.

Specifications (according to XFX)
Voltage	Current	Power
+ 3.3 V	25 A	150 Watt	1'250 Watt (Total)
+ 5.0 V	25 A	150 Watt
+ 12 V	104 A	1'248 Watt
- 12 V	0.5 A	6 Watt
+ 5 Vsb	3.0 A	15 Watt

This PSU is based on one 12V rail that offers 104A. However this rail is split internally into four separate rails.
How the power has been split on the different rails can be seen in the following table:

Specifications (reality)
Voltage	Current	Power
+ 3.3 V	25 A	150 Watt	1'250 Watt (Total)
+ 5.0 V	25 A	150 Watt
+ 12 V1	30 A	1'248 Watt
+ 12 V2	30 A
+ 12 V3	45 A
+ 12 V4	45 A
- 12 V	0.5 A	6 Watt
+ 5 Vsb	3.0 A	15 Watt

The Rails are connected to the connectors as follows:

12V1 - 30A
- 24Pin ATX
- 2x EPS/ATX 12V 8Pin
12V2 - 30A
- 2x PCI-E 6+2 Pin
12V3 - 45A
- 4x PCI-E 6+2 Pin
12V4 - 45A
- Molex
- SATA
- 2x PCI-E 6+2 Pin

The manufacturer has done this in quite an odd way. We understand that a single rail with 104A is potentially dangerous. However we would like to see an optimized rail distribution as well as a more useful OCP protection per rail. 4 x 55A or similar would make sense in our opinion.

The P1-1250-BEFX has been 80Plus Gold certified. This means, that the efficiency of this PSU should be above 87% at 20% load, above 90% at 50% load and above 87% at 100% load.
Feature-list:

80Plus Gold
OVP, UVP, OCP, SCP, OPP, OTP
Dimensions (W x H x D): 150 mm x 86 mm x 190 mm
135 millimeter fan
Semipassive fan (below 20% load)
Warranty: 5 Years
Price: 250 CHF

Page 3 - Delivery / Specs

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A Look Inside

The first hint for a high Quality PSU can be seen when taking a first look at its chassis. With this product you get a nice design and a high quality case.
XFX decided to not follow Seasonic's design this time regarding the fan and went for a Protechnic Electric 135mm Fan instead. Right at the Input there is a YO15T1 (250V, 15A, CX = 0.1uF, CY= 3300pF*2, Commom Mode (CM choke) = 2*0.3uH) from Yunpen Electronic. At the PCB the transient filtering stage continues with two X, four Y, a CM amd DM choke and four MOV (Metal-Oxid-Varistor). Aditionally there is a NTC Tremistor for inrush curent limitation. A mechanical relais shorts the NTC Termistor for normal operation. The transient filtering stage is well done. We have not seen many PSUs with such extensive input filtering.

Two GBJ 2506 (25A) are used for rectification. The PFC Booster consists of two IPW60R099CP Mosfets (650V, 0.1Ohm, 31A) and one C3D101060 (600V, 10A, Qc 25nC) SiC Schottky Diode. The APFC is controled by a NCP1654 (54B65) from ON Semiconductor. The NCP1654 has a gate driver performance of 1.5A. This PSU has three APFC capacitors from Nippon Chemi-Con (KMR series; 330uF, 420V, 105C each). Four 60R160C6 (650V, 0.16Ohm, 23.8 A) Mosfets are used on the primary side of the LLC resonance converter, which is controled by a CM6901. The primary side of this PSU is rock solid. Especially the costly transient filtering stage and the high end japanese Nippon Chemi-Con Capacitors are excellent.

On the secondary side eight BSC018N04LS (40V, 1.8mOhm, 100A) Mosfets do the 12V rectification. Those Mosfets are high quality. However the design is basically the same as on XFX's ProSeries and Seasonic X-Series PSU's with lower wattage rating. It seems to us, that the design has been developed for a PSU in the 850W area and is now being upscaled, mainly by the use of better components. In our view this design is to close to the limit of a hardware breakdown. Especially the area between the transformer connection and the first Mosfet is weak. XFX/Seasonic did also not strengthen this area with an additional copper plate. This has the issue of a relatively high electrical and thermal resistance, which results in a high temperature of the Mosfets (especially the one closest to the transformer) at high loads. The Mosfets are additionaly cooled with a thermal pad, that has been connected to the case, which also gets very warm under high load at the area of the Mosfets. In this PSU the +12V is the middle connection and also phisically in the middle, the Mosfets are switching the ground.

We are also not so happy with the 12V distribution after the rectification. The connection to the front PCB with the 3.3 and 5V converters and the connectors is relatively weak. A PS232 is used for the surveillance of the four 12V rails. Those 4 rails are generated with four coils. There is even a fifth coil for the 3.3 and 5V converter supply. What we highly like to see is that the manufacturer makes heavy use of high end japanese Nippon Chemi-Con copacitors on the secondary side. In fact all capacitors we see are from Nippon Chemi-Con with a 105°C rating. Extremely high end. Thank you XFX/Seasonic!

Page 4 - A Look Inside

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Input/Output Power and Efficiency

Page 5 - Input/Output Power and Efficiency

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Result Analysis and Discussion

Efficiency 115V
Load	Pin(W)	Pout(W)	PF	Efficiency
20 %	284.85	251.57	0.9869	88.32 %
50 %	697.55	629.91	0.9970	90.30 %
100 %	1433.5	1257.45	0.9981	87.72 %

The 80Plus Gold certification requirements (87% - 90% - 87%) are surpassed especially at 20% load. The full load efficiency is a bit higher at 230V AC. This is the case with most of todays PSU's and it mainly originates from the reason of lower losses in the AC filtering stage and the PFC at 230V AC. The 230V AC 100% load efficiency is 90.68%.

Output Stability
Load	Rail	Loading(A)	Output(V)
20 %	5V	3.18	5.031
	3.3V	3.18	3.337
	12V1	3.65	12.12
	12V2	3.65	12.10
	12V3	3.65	12.13
	12V4	7.3	12.15
	5VSB	0.53	5.084

50 %	5V	7.96	5.03
	3.3V	7.96	3.333
	12V1	9.16	12.11
	12V2	9.16	12.08
	12V3	9.16	12.14
	12V4	18.32	12.10
	5VSB	1.32	5.041

100 %	5V	15.92	5.025
	3.3V	15.92	3.326
	12V1	18.32	12.08
	12V2	18.32	12.03
	12V3	18.32	12.16
	12V4	36.64	12.09
	5VSB	2.64	4.969

Noise
Load
20 %	Noiseless
50 %	Silent
100 %	Audible

The Voltage Regulation of this PSU is very good. It makes use of a DC-DC topology. This means, that the P1-1250-BEFX is mainly a 12V PSU and then generates its 5 and 3.3V from 12V. This is a modern approach, and since the Load is mainly on 12V it makes a lot of sense. For almost any PSU which makes use of this topology crossload tests do not present a problem.

Noise/Ripple
Voltage	Noise/Ripple Vpp
5V	0.0344
12V	0.0308
-12V	0.0333
3.3V	0.0228
+5VSB	0.0212

The noise values are good. Only the 34mV at 5V are a bit high, but since the 5V ripple performance drastically improves with just little less 5V load, we don't judge this as a negative point.

Page 6 - Result Analysis and Discussion