FSP Aurum CM Gold 750 W Power Supply Review
By Gabriel Torres on June 16, 2011


Introduction

In the beginning of this year, FSP launched its 80 Plus Gold power supply series, dubbed Aurum Gold series (which is a redundant name, by the way, since Aurum means “Gold” in Latin; calling something “Gold Gold” makes no sense). With models ranging from 400 W to 700 W, this series surprised everybody with its incredible low price, thanks to the unusual electronic architecture used. FSP is now launching another series based on the same design, featuring a modular cabling system and offered in 550 W, 650 W and 750 W versions. The first version won’t be available in North America, but the other two should arrive in the North American market by the end of this month. Let’s see if the 750 W model is a good buy.

FSP Aurum CM Gold 750 W power supply
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Figure 1: FSP Aurum CM Gold 750 W power supply

FSP Aurum CM Gold 750 W power supply
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Figure 2: FSP Aurum CM Gold 750 W power supply

The FSP Aurum CM Gold 750 W is 6.3” (160 mm) deep, with a 120 mm fluid dynamic bearing fan (Protechnic Electric MGA12012HF-A25, 2,400 rpm, 84.8 cfm, 37 dBA) on its bottom part.

This unit has a modular cabling system with five connectors (one for a video card power cable and four for SATA and peripheral power cables). Three cables are permanently attached to the power supply. This power supply comes with the following cables:

All wires are 18 AWG, which is the correct gauge to be used.

The cable configuration is very good for a 750 W product.

FSP Aurum CM Gold 750 W power supply
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Figure 3: Cables

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

A Look Inside the FSP Aurum CM Gold 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. As already mentioned, the Aurum CM Gold 750 W uses the same platform as the original Aurum Gold series.

FSP Aurum CM Gold 750 W power supply
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Figure 4: Top view

FSP Aurum CM Gold 750 W power supply
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Figure 5: Front quarter view

FSP Aurum CM Gold 750 W power supply
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Figure 6: Rear quarter view

FSP Aurum CM Gold 750 W power supply
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Figure 7: 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 this power supply, this stage has one X capacitor and two Y capacitors more than the minimum required. It doesn’t have an MOV, but FSP explained to us that the custom integrated circuit used in the primary can somehow remove spikes coming from the power grid. Since there is no datasheet available for this component, we can’t confirm this information.

FSP Aurum CM Gold 750 W power supply
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Figure 8: Transient filtering stage (part 1)

FSP Aurum CM Gold 750 W power supply
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Figure 9: Transient filtering stage (part 2)

On the next page we will have a more detailed discussion about the components used in the FSP Aurum CM Gold 750 W.

Primary Analysis

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

This power supply uses one GBU15L06 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 15 A at 115° C, so in theory, you would be able to pull up to 1,725 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out. Of course, we are only talking about this component, and the real limit will depend on all the other components in this power supply. The Aurum Gold 700 W uses a similar bridge here.

FSP Aurum CM Gold 750 W power supply
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Figure 10: Rectifying bridge

The active PFC circuit uses two IPB60R165CP MOSFETs, which are capable of delivering up to 21 A at 25° C or 13 A at 100° C in continuous mode (note the difference temperature makes), or up to 61 A in pulse mode at 25° C, each. These transistors present a 165 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. These are the same transistors used in the FSP Aurum Gold 700 W.

The capacitor used to filter the output of the active PFC circuit is Japanese, from Rubycon, and labeled at 105° C.

In the switching section, FSP decided to use a very unique design, called active clamp reset forward, and it seems that FSP put a lot of effort in developing this design. The switching transistor is an SPA17N80C3 MOSFET, which is capable of delivering up to 17 A at 25° C or 11 A at 100° C in continuous mode (note the difference temperature makes), or up to 51 A at 25° C in pulse mode. This transistor presents a 290 mΩ RDS(on). A second transistor (resetting transistor) is used to turn off the switching transistor and is controlled from the secondary side. The transistor used for this function is an FQPF3N80C. This is exactly the same configuration used in the FSP Aurum Gold 700 W.

FSP Aurum CM Gold 750 W power supply
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Figure 11: Switching transistor, resetting transistor, active PFC diode and active PFC transistors

The primary is managed by a custom-made PFC/PWM controller called FSP6600. Since this is a custom integrated circuit, no datasheet is available for it.

FSP Aurum CM Gold 750 W power supply
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Figure 12: Active PFC/PWM combo controller

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

Secondary Analysis

This power supply uses a synchronous design in its secondary, meaning that the diodes were replaced with transistors in order to increase efficiency.

The +12 V output is rectified using two IRLB3036 MOSFETs, each one capable of handling up to 270 A at 25° C or up to 190 A at 100° C in continuous mode, or up to 1,100 A at 25° C in pulse mode. This translates into a maximum theoretical current of 271 A at 100° C or 3,257 W! These are the same transistors used in the Aurum Gold 700 W.

FSP Aurum CM Gold 750 W power supply
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Figure 13: +12 V transistors

The +5 V and +3.3 V outputs share the same circuitry and are rectified by two IPD031N03L MOSFETs – 90 A at 100° C in continuous mode and 400 A at 25° C in pulse mode, 3.1 mΩ RDS(on) – and two IPD050N03L MOSFETs. The four transistors are located on the solder side of the printed circuit board.

FSP Aurum CM Gold 750 W power supply
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Figure 14: The +5 V and +3.3 V transistors

The secondary transistors are controlled by an FSP6601, another proprietary chip from FSP.

FSP Aurum CM Gold 750 W power supply
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Figure 15: Synchronous controller

The secondary is monitored by a WT7579 integrated circuit, which is manufactured exclusively for FSP. This chip supports over voltage (OVP), under voltage (UVP), overcurrent (OCP), and over temperature (OTP) protections. There are four +12 V over current protection (OCP) channels, matching the number of +12 V rails advertised by the manufacturer.

FSP Aurum CM Gold 750 W power supply
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Figure 16: Monitoring circuit

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

In summary, the Aurum CM Gold 750 W is internally identical to the Aurum Gold 700 W.

Power Distribution

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

FSP Aurum CM Gold 750 W power supply
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Figure 17: Power supply label

As you can see, the manufacturer lists this unit as having four +12 V rails. Analyzing the circuit, we could clearly see four “shunts” (current sensors), matching the number of rails advertised by the manufacturer. See Figure 18.

FSP Aurum CM Gold 750 W power supply
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Figure 18: Shunts

The available +12 V rails are distributed like this:

This distribution is perfect, as it separates the CPU and the video card power cables on individual rails. However, if you have only one video card with two power connectors, we recommend that you use one connector from each available cable instead of using the two power connectors available on one of the cables.

Let’s now see if this power supply can really deliver 750 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 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 input was connected to the power supply +12V1 and +12V3 rails, while the +12VB input was connected to the power supply +12V2 rail.

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)

+5 V

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

149.3 W

299.5 W

446.8 W

591.6 W

748.4 W

% Max Load

19.9%

39.9%

59.6%

78.9%

99.8%

Room Temp.

45.4° C

45.0° C

46.8° C

47.7° C

46.9° C

PSU Temp.

47.8° C

48.2° C

49.4° C

50.4° C

51.7° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

165.7 W

330.2 W

498.5 W

674.0 W

868.0 W

Efficiency

90.1%

90.7%

89.6%

87.8%

86.2%

AC Voltage

116.2 V

114.5 V

112.9 V

110.4 V

109.1 V

Power Factor

0.984

0.996

0.998

0.999

0.999

Final Result

Pass

Pass

Pass

Pass

Pass

The FSP Aurum CM Gold 750 W can really deliver its labeled wattage.

Efficiency was extremely high when we pulled between 20% and 60% of the labeled wattage (i.e., between 150 W and 450 W), ranging from 89.6% to 90.7%. At 80% load (600 W), efficiency dropped to 87.8%, still very high. And at full load (750 W), efficiency dropped to 86.2%, a little bit below the 87% minimum promised by the 80 Plus Gold certification. As we always must explain, tests for the 80 Plus certification are conducted at a room temperature of only 23° C, and we test power supplies above 45° C. (Efficiency drops with temperature.)

Voltage regulation was excellent, with all voltages within 3% of their nominal values, except for the -12 V output. (The -12 V output was inside the proper range.) This means that the positive voltages were closer to their nominal values than required by the ATX12V specification, which says positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.

Noise and ripple levels were always below the maximum allowed, but a little too high at the +12 V outputs when the unit was delivering 750 W for us to consider this unit as “flawless.” Below, you can see the results for the power supply outputs during test number five. The maximum allowed is 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.

FSP Aurum CM Gold 750 W power supply
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Figure 19: +12VA input from load tester during test five at 748.4 W (68.4 mV)

FSP Aurum CM Gold 750 W power supply
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Figure 20: +12VB input from load tester during test five at 748.4 W (81.2 mV)

FSP Aurum CM Gold 750 W power supply
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Figure 21: +5V rail during test five at 748.4 W (36.4 mV)

FSP Aurum CM Gold 750 W power supply
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Figure 22: +3.3 V rail during test five at 748.4 W (29.6 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. We couldn’t pull more than that because the power supply shut down, showing that its protections were working well.

Input

Overload Test

+12VA

30 A (360 W)

+12VB

30 A (360 W)

+5 V

12 A (60 W)

+3.3 V

12 A (39.6 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

836.4 W

% Max Load

111.5%

Room Temp.

44.8° C

PSU Temp.

48.1° C

AC Power

1,000 W

Efficiency

82.6%

AC Voltage

107.9 V

Power Factor

0.999

Main Specifications

The main specifications for the FSP Aurum CM Gold 750 W power supply include:

Conclusions

In this review, we discovered that the new FSP Aurum CM Gold 750 W is internally virtually identical to the FSP Aurum Gold 700 W. The only difference between the two is the addition of the modular cabling system on the CM version. (There are two small technical differences: The use of a bigger active PFC coil and more efficient rectifying bridge in the CM Gold 750 W.)

The performance of the FSP Aurum CM Gold 750 W was inside our expectations, with very high efficiency between 86.2% and 90.7%, voltages closer to their nominal values than necessary (i.e., 3% voltage regulation), and noise and ripple levels inside specifications, although we’d like to see them lower when we pulled 750 W from the unit.

 FSP told us that the reviewed power supply will arrive on the market with a suggested price of USD 180, which is a bit steep when we consider that the Aurum Gold 700 W is currently sold for USD 125. We know that online stores rarely sell computer components at their suggested prices. A fair price for this unit, in our opinion, is USD 150. If it arrives for more than that, you have two better options if you want to buy an 80 Plus Gold power supply: The FSP Aurum Gold 700 W, if you want to save money and don’t mind not having a modular cabling system, or the Sentey Golden Steel Power 850 W, which is labeled at 850 W, costs USD 160, and also comes with a modular cabling system.

Therefore, we will have to wait until this product reaches the market and we know its actual price to know if it deserves our recommendation.

Originally at http://www.hardwaresecrets.com/article/FSP-Aurum-CM-Gold-750-W-Power-Supply-Review/1313


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