Athena Power AP-MFATX35 350 W Power Supply Review
By Gabriel Torres on May 18, 2011


Introduction

The Athena Power AP-MFATX35 measures only 3.2" x 1.7" x 6" (80 x 40 x 150 mm) (W x H x D), being targeted to small form factor (SFF) computers with Mini-ITX motherboards. Rated at 350 W, is has the 80 Plus Bronze certification, which promises at least 82% efficiency. Let’s see if this product is a good option.

Athena Power AP-MFATX35 power supply
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Figure 1: Athena Power AP-MFATX35 power supply

Athena Power AP-MFATX35 power supply
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Figure 2: Athena Power AP-MFATX35 power supply

Because of its reduced size, it uses a tiny 40 mm fan, a Sunon KDE1204PKVX-A with MagLev bearing.

The cables are permanently attached to the power supply, and they don’t have nylon sleeves. 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 outstanding for a 350 W product since it comes with two power connectors for video cards, a feature not usually found on power supplies in this power range. One strange thing about this unit, however, is that it still has the -5 V output (white wire), which was removed from the ATX12V specification in January of 2002.

Athena Power AP-MFATX35 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 Athena Power AP-MFATX35

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.

In 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.

Athena Power AP-MFATX35 power supply
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Figure 4: Top view

Athena Power AP-MFATX35 power supply
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Figure 5: Front quarter view

Athena Power AP-MFATX35 power supply
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Figure 6: Rear quarter view

Athena Power AP-MFATX35 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 is flawless. It has two Y capacitors more than the minimum required.

Athena Power AP-MFATX35 power supply
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Figure 8: Transient filtering stage (part 1)

Athena Power AP-MFATX35 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 Athena Power AP-MFATX35 .

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Athena Power AP-MFATX35. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses one US8K80R rectifying bridge in its primary, which is attached to the same heatsink used by one of the switching transistors. This component supports up to 8 A at 108° C, so in theory, you would be able to pull up to 920 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 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.

Athena Power AP-MFATX35 power supply
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Figure 10: Rectifying bridge

The active PFC circuit uses one SPW32N50C3 MOSFET, which supports up to 32 A at 25° C or 20 A at 100° C in continuous mode (note the difference temperature makes), or up to 96 A at 25° C in pulse mode. This transistor presents a 110 mΩ resistance when turned on, a characteristic called RDS(on). The lower this number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Athena Power AP-MFATX35 power supply
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Figure 11: One of the switching transistors, the active PFC diode, and the active PFC transistor

The electrolytic capacitor that filters the output of the active PFC circuit is from Yihcon and is labeled at 105° C.

In the switching section, two FQPF13N50C MOSFETs are used in the traditional two-transistor forward configuration, each supporting up to 13 A at 25° C or 8 A at 100° C in continuous mode, or up to 52 A at 25° C in pulse mode, with an RDS(on) of 480 mΩ.

Athena Power AP-MFATX35 power supply
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Figure 12: The other switching transistor

The primary is controlled by the popular CM6800 active PFC/PWM combo controller.

Athena Power AP-MFATX35 power supply
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Figure 13: Active PFC/PWM combo controller

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

Secondary Analysis

The maximum theoretical current each line can deliver is given by the formula I / (1 - D) where D is the duty cycle used and I is the maximum current supported by the rectifying diode. As an exercise, we can assume a duty cycle of 30 percent.

The +12 V output uses two SBL40L60CT Schottky rectifiers (40 A, 20 A per internal diode at 90°, 0.60 V maximum voltage drop), giving us a maximum theoretical current of 57 A or 686 W for this output.

The +5 V output uses one S30C45CM Schottky rectifier (30 A, 15 A per internal diode at 125° C, 0.55 V maximum voltage drop), giving us a maximum theoretical current of 21 A or 107 W for this output.

The +3.3 V output uses one STPS30L45CT Schottky rectifier (30 A, 15 A per internal diode at 135° C, 0.74 V maximum voltage drop), giving us a maximum theoretical current of 21 A or 71 W for this output.

Athena Power AP-MFATX35 power supply
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Figure 14: The +5 V and +12 V rectifiers

Athena Power AP-MFATX35 power supply
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Figure 15: The +3.3 V rectifier

This power supply uses a PS223 monitoring integrated circuit, which supports over voltage (OVP), under voltage (UVP), over current (OCP), and over temperature (OTP) protections. This chip has four OCP channels, one for +3.3 V, one for +5 V, and two for +12 V, correctly matching the number of +12 V rails advertised by the power supply manufacturer (two).

Athena Power AP-MFATX35 power supply
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Figure 16: Monitoring circuit

The electrolytic capacitors available in the secondary are Japanese, from Rubycon, and labeled at 105° C.

Power Distribution

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

Athena Power AP-MFATX35 power supply
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Figure 17: Power supply label

This power supply is sold as having two +12 V rails, which is correct, since this unit has two +12 V over current protection circuits (see previous page), and we could clearly see two “shunts” (current sensors). See Figure 18. Click here to understand more about this subject.

Athena Power AP-MFATX35 power supply
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Figure 18: Shunts

The two +12 V rails are distributed like this:

This distribution is adequate.

How much power can this unit really deliver? Let’s find out.

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 rail, while the +12VB input was connected to the power supply +12V2 rail (EPS12V connector).

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

2 A (24 W)

4.5 A (54 W)

7 A (84 W)

9 A (108 W)

11.25 A (135 W)

+12VB

2 A (24 W)

4.5 A (54 W)

7 A (84 W)

9 A (108 W)

11 A (132 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 A (5 W)

1 A (5 W)

1.5 A (7.5 W)

2 A (10 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

66.2 W

133.3 W

208.8 W

274.8 W

348.4 W

% Max Load

18.9%

38.1%

59.7%

78.5%

99.5%

Room Temp.

42.4° C

41.8° C

41.7° C

44.1° C

45.9° C

PSU Temp.

47.7° C

50.7° C

50.5° C

51.3° C

54.4° C

Voltage Stability

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Fail at +3.3 V

AC Power

83.1 W

158.8 W

248.8 W

331.6 W

428.8 W

Efficiency

79.7%

83.9%

83.9%

82.9%

81.3%

AC Voltage

117.4 V

117.3 V

116.2 V

115.7 V

114.7 V

Power Factor

0.947

0.972

0.984

0.989

0.991

Final Result

Pass

Pass

Pass

Pass

Fail

The Athena Power AP-MFATX35 can really deliver its labeled wattage.

Efficiency was above 82% only when we pulled between 40% and 80% of the unit’s labeled wattage (i.e., between 140 W and 280 W). At light (20%, i.e., 70 W) load, efficiency was a little below 80%. As we always point out, Ecos Consulting, the company behind the 80 Plus certification, tests power supplies at only 23° C, while we test them at higher (and more realistic) temperatures. It is common to see units that passed the 80 Plus certification that wouldn’t pass if Ecos Consulting were using our testing methodology.

Voltage regulation was acceptable, with all voltages within the proper range. The ATX12V specification says that 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 really high with the unit delivering 350 W, with the +3.3 V output presenting a noise level above the maximum allowed. 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.

Athena Power AP-MFATX35 power supply
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Figure 19: +12VA input from load tester during test five at 348.4 W (98.8 mV)

Athena Power AP-MFATX35 power supply
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Figure 20: +12VB input from load tester during test five at 348.4 W (95.2 mV)

Athena Power AP-MFATX35 power supply
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Figure 21: +5 V rail during test five at 348.4 W (46.2 mV)

Athena Power AP-MFATX35 power supply
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Figure 22: +3.3 V rail during test five at 348.4 W (54.6 mV)

Let’s see if we can pull more than 350 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, as the power supply shut down, showing us that its protections were working fine. At this extreme condition, however, noise level at +5 V and +3.3 V outputs were above the maximum allowed, and efficiency dropped below 80 percent.

Input

Overload Test

+12VA

12 A (144 W)

+12VB

12 A (144 W)

+5 V

10 A (50 W)

+3.3 V

10 A (33 W)

+5VSB

2 A (10 W)

-12 V

0.5 A (6 W)

Total

377.9 W

% Max Load

108.0%

Room Temp.

41.0° C

PSU Temp.

50.8° C

AC Power

478.5 W

Efficiency

79.0%

AC Voltage

113.7 V

Power Factor

0.994

Main Specifications

The main specifications for the Athena Power AP-MFATX35 power supply include:

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

Conclusions

We know how hard it is to make a very small power supply. With components cramped in such a small space, there is no space for air to flow. At first, the Athena Power AP-MFATX35 looks like a good FlexATX unit with 80 Plus Bronze certification, but it is a flawed product that must be avoided. It can’t deliver the announced efficiency at high temperatures (at light load efficiency drops below the 80% mark), and the real issue with this unit is its high noise and ripple levels, which surpassed the maximum allowed at +3.3 V when we were pulling 350 W from it. We got two samples of this product, with the same results. In addition, the first sample burned in less than one minute when delivering 350 W, probably due to overheat (the component that burned was one of the +12 V rectifiers). To top it off, we have the price (USD 71), which users will probably find high for a 350 W unit.

Originally at http://www.hardwaresecrets.com/article/Athena-Power-AP-MFATX35-350-W-Power-Supply-Review/1282


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