Athena Power AP-MFATX40P8 400 W Power Supply Review
By Gabriel Torres on February 9, 2012


Introduction

Hardware Secrets Silver Award

The Athena Power AP-MFATX40P8 400 W is a tiny FlexATX power supply measuring 3.2 x 1.7 x 6 inches (80 x 40 x 150 mm), targeted to small form factor (SFF) computers with Mini-ITX motherboards, coming with the 80 Plus Bronze certification. We tested the 350 W version of this power supply, which didn’t pass our tests. Let’s see if the 400 W version is a better product.

At least externally, some improvements were made. The box was redesigned and comes with a QR Code that you can scan with your smartphone, which opens a compatibility table where you can see whether the power supply is compatible with your SFF computer or not. The power supply housing was upgraded to a more appealing nickel look.

Athena Power AP-MFATX40P8 power supply
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Figure 1: Athena Power AP-MFATX40P8 power supply

Athena Power AP-MFATX40P8 power supply
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Figure 2: Athena Power AP-MFATX40P8 power supply

Because of its reduced size, it uses a tiny 40 mm ball bearing fan, a Yate Loon D40BM-12C.

This unit doesn’t have a modular cabling system, and only the main motherboard cable and the EPS12V/ATX12V use nylon sleeves, which don’t come from inside the unit. This power supply comes with the following cables:

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

The cables are extremely short, but this should not be a problem, as this power supply is targeted to small form factor (SFF) systems. Interesting enough, the cable configuration is similar to the one used on the 350 W model; however, the 350 W model uses longer cables.

Athena Power AP-MFATX40P8 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-MFATX40P8

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.

Athena Power AP-MFATX40P8 power supply
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Figure 4: Top view

Athena Power AP-MFATX40P8 power supply
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Figure 5: Front quarter view

Athena Power AP-MFATX40P8 power supply
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Figure 6: Rear quarter view

Athena Power AP-MFATX40P8 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 stage, the Athena Power AP-MFATX40P8 power supply is flawless. It has two Y capacitors and one X capacitor more than the minimum required.

Athena Power AP-MFATX40P8 power supply
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Figure 8: Transient filtering stage (part 1)

Athena Power AP-MFATX40P8 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-MFATX40P8.

Primary Analysis

On this page we will take an in-depth look at the primary stage of the Athena Power AP-MFATX40P8. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one US8K80R rectifying bridge, which is attached to the same heatsink used by one of the switching transistors. This bridge 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 particular component. The real limit will depend on all the components combined in this power supply.

Athena Power AP-MFATX40P8 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 in pulse mode at 25° C. These transistors present a 110 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.

Athena Power AP-MFATX40P8 power supply
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Figure 11: One of the switching transistors, the active PFC diode, and the active PFC transistor

The output of the active PFC circuit is filtered by a 220 µF x 400 V electrolytic capacitor from Yihcon and labeled at 105° C.

In the switching section, two FQPF13N50 MOSFETs are used in the traditional two-transistor forward configuration, supporting up to 13 A at 25° C or 8 A at 100° C in continuous mode, or up to 52 A in pulse mode at 25° C, with an RDS(on) of 480 mΩ.

Athena Power AP-MFATX40P8 power supply
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Figure 12: The other switching transistor

The primary is managed by an omnipresent CM6800 active PFC/PWM controller.

Athena Power AP-MFATX40P8 power supply
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Figure 13: Active PFC/PWM controller

The primary of the 400 W model is identical to the primary of the 350 W model. Let’s now take a look at the secondary of this power supply.

Secondary Analysis

The Athena Power AP-MFATX40P8 uses a regular design in its secondary, with Schottky rectifiers.

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 SBR40U60CT Schottky rectifiers (40 A, 20 A per internal diode at 100° C, 0.60 V maximum voltage drop). This gives us a maximum theoretical current of 57 A or 686 W for the +12 V output. The 350 W model uses similar rectifiers here.

The +5 V output uses one STPS30L45CT Schottky rectifier (30 A, 15 A per internal diode at 135° C, 0.74 V maximum voltage drop). This gives us a maximum theoretical current of 21 A or 107 W for the +5 V output. The 350 W model uses a similar rectifier here.  

The +3.3 V output uses another STPS30L45CT Schottky rectifier. This gives us a maximum theoretical current of 21 A or 71 W for the +3.3 V output. This component is identical to the one used on the 350 W model.

Athena Power AP-MFATX40P8 power supply
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Figure 14: The +5 V and +12 V rectifiers

Athena Power AP-MFATX40P8 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 offers two +12 V channels, correctly matching the number of +12 V rails advertised by the manufacturer.

Athena Power AP-MFATX40P8 power supply
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Figure 16: Monitoring circuit

Some of the electrolytic capacitors that filter the outputs are Japanese, from Sanyo, while others are from Asia’x. They are all labeled at 105° C, as usual.

In summary, both 350 W and 400 W models use similar components; however, the 400 W model uses a revised printed circuit board (revision A1), while the 350 W model uses revision A0.

Power Distribution

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

Athena Power AP-MFATX40P8 power supply
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Figure 17: Power supply label

As you can see, 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-MFATX40P8 power supply
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Figure 18: Shunts

The two +12 V rails are distributed as follows:

This is the typical distribution used by power supplies with two +12 V virtual rails.

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.

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

2.5 A (30 W)

5.5 A (66 W)

8 A (96 W)

10.5 A (126 W)

14 A (168 W)

+12VB

2.5 A (30 W)

5.5 A (66 W)

8 A (96 W)

10.5 A (126 W)

13 A (156 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

77.8 W

153.1 W

235.2 W

312.8 W

398.6 W

% Max Load

19.5%

38.3%

58.8%

78.2%

99.7%

Room Temp.

44.8° C

44.6° C

45.2° C

45.8° C

46.3° C

PSU Temp.

45.9° C

44.9° C

45.3° C

47.6° C

52.8° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

94.6 W

178.8 W

275.5 W

373.1 W

487.3 W

Efficiency

82.2%

85.6%

85.4%

83.8%

81.8%

AC Voltage

116.5 V

115.9 V

114.9 V

113.9 V

112.6 V

Power Factor

0.942

0.969

0.985

0.99

0.993

Final Result

Pass

Pass

Pass

Pass

Pass

The Athena Power AP-MFATX40P8 passed our tests, which really surprised us, since the 350 W model failed them. We are very happy to see that the revision Athena Power did to this unit really fixed the efficiency and noise level issues.

Efficiency was between 81.8% and 85.6% during our tests, virtually matching the values promised by the 80 Plus Bronze certification. Efficiency with the power supply delivering 400 W was a tiny bit below the 82% promised by the 80 Plus Bronze certification, but 81.8% was a good result anyway. As we always explain, the tests done during the 80 Plus certification process are conducted at 23° C, and efficiency drops as we increase temperature. (We test power supplies between 45° C and 50° C.)

Voltage regulation was very good, with all voltages closer to their nominal values than required (three percent regulation), except for the +5 V output at tests one and two (+5.21 V and +5.19 V, respectively) and the -12 V output at test one (-11.41 V). These outputs were still inside the allowed range. 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.

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 Athena Power AP-MFATX40P8 provided 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

20.6 mV

20.8 mV

27.4 mV

49.8 mV

66.6 mV

+12VB

23.8 mV

25.4 mV

31.4 mV

55.6 mV

73.4 mV

+5 V

14.4 mV

16.4 mV

21.6 mV

21.4 mV

24.4 mV

+3.3 V

10.2 mV

11.6 mV

13.6 mV

15.4 mV

18.8 mV

+5VSB

12.2 mV

15.4 mV

19.6 mV

23.4 mV

26.6 mV

-12 V

32.6 mV

35.4 mV

50.4 mV

62.4 mV

79.4 mV

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

Athena Power AP-MFATX40P8 power supply
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Figure 19: +12VA input from load tester during test five at 398.6 W (66.6 mV)

Athena Power AP-MFATX40P8 power supply
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Figure 20: +12VB input from load tester during test five at 398.6 W (73.4 mV)

Athena Power AP-MFATX40P8 power supply
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Figure 21: +5V rail during test five at 398.6 W (24.4 mV)

Athena Power AP-MFATX40P8 power supply
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Figure 22: +3.3 V rail during test five at 398.6 W (18.8 mV)

Let’s see if we can pull more than 400 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, as we couldn’t pull more than shown in the table below, as the power supply would shut down, showing that its protections are present and working fine. During this extreme configuration, noise and ripple levels and voltages were still inside the proper limits.

Input

Overload Test

+12VA

17 A (204 W)

+12VB

17 A (204 W)

+5 V

8 A (40 W)

+3.3 V

8 A (26.4 W)

+5VSB

3 A (15 W)

-12 V

0.5 A (6 W)

Total

478.3 W

% Max Load

119.6%

Room Temp.

48.6° C

PSU Temp.

56.0° C

AC Power

593.4 W

Efficiency

80.6%

AC Voltage

112.6 V

Power Factor

0.994

Main Specifications

The main specifications for the Athena Power AP-MFATX40P8 power supply include:

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

Conclusions

The Athena Power AP-MFATX40P8 presented efficiency between 81.8% and 85.6%, voltages closer to their nominal values than required (three percent regulation) most of the time, and noise and ripple levels around half of the maximum allowed.

We were really happy to see that Athena Power fixed all issues we found with the 350 W version of this power supply.

The only “problem” with this power supply is its price. At around USD 80, it is expensive for a 400 W unit. However, we know how hard it is to build a high-efficiency power supply in a small form factor, as heat will always be the main issue. If you are building a small form factor (SFF) computer that requires a FlexATX power supply, and you are looking for a unit with above average efficiency, the Athena Power AP-MFATX40P8 is certainly a great option if you don’t mind its price. Keep in mind that cheaper FlexATX power supplies out there either don’t have the 80 Plus certification or have the standard (white) one.

Price is the main reason we are giving this unit our “Silver Award” instead of the “Golden.”

Originally at http://www.hardwaresecrets.com/article/Athena-Power-AP-MFATX40P8-400-W-Power-Supply-Review/1486


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