ASUS Atlas A-45GA 450 W Power Supply Review
By Gabriel Torres on June 23, 2010


Introduction

Although this unit is already discontinued by the manufacturer, we are always curious about the performance of low-end power supplies, just for fun. Let’s see what the ASUS Atlas A-45GA is, and whether you should be worried or not if you own one.

This power supply is manufactured by Delta Electronics and it is in fact a renamed GPS-450AP-100.

ASUS Atlas A-45GA 450 W power supply
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Figure 1: ASUS Atlas A-45GA 450 W power supply

ASUS Atlas A-45GA 450 W power supply
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Figure 2: ASUS Atlas A-45GA 450 W power supply

The ASUS Atlas A-45GA 450 W is 5 ½” (140 mm) deep, using a 120 mm fan on its bottom. The fan used is a Yate Loon D12SH-12(F).

This unit features a PFC circuit.

No modular cabling system is provided and only the main motherboard cable has a nylon protection that comes from inside the power supply housing. All cables use 18 AWG wires, which is the correct gauge to be used, except the +3.3 V (orange) wires of the main motherboard cable, which are thicker (16 AWG). The cables included are:

This configuration is adequate for a low-end PC.

ASUS Atlas A-45GA 450 W power supply
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Figure 3: Cables

Now let’s take an in-depth look inside this power supply.

A Look Inside The ASUS A-45GA 450 W

We decided to disassemble this power supply to see how it looks inside, what design is used, 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.

This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.

ASUS Atlas A-45GA 450 W power supply
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Figure 4: Overall look

ASUS Atlas A-45GA 450 W power supply
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Figure 5: Overall look

ASUS Atlas A-45GA 450 W power supply
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Figure 6: Overall look

ASUS Atlas A-45GA 450 W power supply
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Figure 7: 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 four Y capacitors and one ferrite coil more than required (plus an X capacitor after the rectifying bridges), however it doesn’t have an MOV, which is the component in charge of removing spikes coming from the power grid.

ASUS Atlas A-45GA 450 W power supply
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Figure 8: Transient filtering stage (part 1)

ASUS Atlas A-45GA 450 W power supply
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Figure 9: Transient filtering stage (part 2)

Primary Analysis

On this page we will take an in-depth look at the primary stage of the ASUS Atlas A-45GA 450 W. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.

This power supply uses two T6KB80 rectifying bridges on its primary, but they are not attached to a heatsink. We couldn’t find the datasheets for these components, but we can safely assume that each one supports up to 6 A, so in theory, you would be able to pull up to 1,380 W from the power grid. Assuming 80% efficiency, the bridges would allow this unit to deliver up to 1,104 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.

ASUS Atlas A-45GA 450 W power supply
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Figure 10: Rectifying bridges

Two SPW20N60C3 power MOSFETs are used on the active PFC circuit, each one capable of delivering up to 20.7 A at 25° C or 13.1 A at 100° C in continuous mode (note the difference temperature makes) or up to 62.1 A at 25° C in pulse mode. These transistors present a maximum resistance of 190 mΩ when turned on, a characteristic called RDS(on). This number indicates the amount of power that is wasted, so the lower this number the better, as less power will be wasted, thus increasing efficiency.

The electrolytic capacitor used to filter the output from the active PFC circuit is from Samxon and labeled at 85° C.

On the switching section ASUS A-45GA uses another two SPW20N60C3 transistors in the traditional two-transistor forward configuration. The specs from these components were already published above.

ASUS Atlas A-45GA 450 W power supply
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Figure 11: One of the active PFC transistors and switching transistors

Instead of using an active PFC/PWM combo controller, the reviewed power supply uses two separated circuits, a UCC3818 active PFC controller and a UC3845B PWM controller.

ASUS Atlas A-45GA 450 W power supply
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Figure 12: Active PFC controller

ASUS Atlas A-45GA 450 W power supply
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Figure 13: PWM controller

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

Secondary Analysis

The secondary heatsink has five Schottky rectifiers attached to it, plus an LM7912 voltage regulator in charge of regulating the -12 V output.

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. Just as an exercise, we can assume a typical duty cycle of 30%.

The +12 V output is generated by two STPS20H100CT Schottky rectifiers connected in parallel, each one capable of handling up to 20 A (10 A per internal diode at 160° C, 0.88 V maximum voltage drop), giving us a maximum theoretical current of 29 A or 343 W for the +12 V output.

The +5 V output is generated by two STPS4045CW Schottky rectifiers connected in parallel, each one capable of handling up to 40 A (20 A per internal diode at 145° C, 0.94 V maximum voltage drop), giving us a maximum theoretical current of 57 A or 286 W.

The +3.3 V output is generated by another STPS4045CW Schottky rectifier, giving us a maximum theoretical current of 29 A or 94 W for this output.

Note how the +5 V rectifiers are more powerful than the +12 V rectifiers, a typical configuration used by power supplies based on old projects. Nowadays power supplies must have a greater current limit on the +12 V rail, since the components that most pull current (and power) in the computer, the CPU and the video cards, are attached to this output.

ASUS Atlas A-45GA 450 W power supply
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Figure 14: -12 V voltage regulator, +3.3 V, +5 V and +12 V rectifiers

This power supply uses a monitoring integrated circuit called a DWA105, which we couldn’t find any information about, so we can’t comment on what protections this unit really has. An LM339 voltage comparator is also used.

ASUS Atlas A-45GA 450 W power supply
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Figure 15: Monitoring circuit

Electrolytic capacitors from the secondary are from Ltec and labeled at 105° C.

Power Distribution

In Figure 16, you can see the power supply label containing all the power specs.

ASUS Atlas A-45GA 450 W power supply
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Figure 16: Power supply label

As you can see, according to the label this unit has two +12 V rails. The +12 V wires are really divided in two groups and we could clearly see a “shunt” (current sensor) connected to each one of them (see Figure 17), but since we couldn’t get the datasheet of the monitoring integrated circuit, we can’t say with 100% confidence if this power supply really has over current protection (OCP) monitoring each rail.

ASUS Atlas A-45GA 450 W power supply
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Figure 17: Current sensors

The two groups are divided like this:

This distribution is awful, because it puts the two components that pull most of the computer current/power (the CPU and the video card) on the same rail. This is another evidence that this power supply uses an obsolete design.

Now let’s see if this power supply can really deliver 450 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 how the reviewed unit behaved 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 power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (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. On 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 +12V2 rails, while +12VB was connected to the power supply +12V2 rail (ATX12V connector).

Input

Test 1

Test 2

Test 3

Test 4

Test 5

+12VA

3 A (36 W)

3.5 A (42 W)

4.5 A (54 W)

5.5 A (66 W)

6.25 A (75 W)

+12VB

2.5 A (30 W)

3.25 A (39 W)

4 A (48 W)

5 A (60 W)

6 A (72 W)

+5V

1 A (5 W)

1 A (5 W)

1.5 A (7.5 A)

1.5 A (7.5 A)

2 A (10 W)

+3.3 V

1 A (5 W)

1 A (5 W)

1.5 A (4.95 W)

1.5 A (4.95 W)

2 A (6.6 W)

+5VSB

1 A (5 W)

1 A (5 W)

1 A (5 W)

1 A (5 W)

1 A (5 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

90.7 W

99.8 W

124.5 W

147.9 W

172.6 W

% Max Load

20.2%

22.2%

27.7%

32.9%

38.4%

Room Temp.

46.1° C

44.3° C

43.6° C

42.5° C

42.3° C

PSU Temp.

48.0° C

47.3° C

47.0° C

47.0° C

47.1° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

122.4 W

132.4 W

162.8 W

192.0 W

223.4 W

Efficiency

74.1%

75.4%

76.5%

77.0%

77.3%

AC Voltage

113.4 V

113.5 V

113.1 V

113.5 V

114.0 V

Power Factor

0.960

0.962

0.966

0.968

0.970

Final Result

Pass

Pass

Pass

Pass

Pass


Input

Test 6

Test 7

Test 8

Test 9

Test 10

+12VA

7.5 A (90 W)

8.25 A (99 W)

9.25 A (111 W)

10 A (120 W)

11 A (132 W)

+12VB

7 A (84 W)

8 A (96 W)

9 A (108 W)

10 A (120 W)

11 A (132 W)

+5V

2 A (10 W)

2.5 A (12.5 W)

2.5 A (12.5 W)

3 A (15 W)

3 A (15 W)

+3.3 V

2 A (6.6 W)

2.5 A (8.25 W)

2.5 A (8.25 W)

3 A (9.9 W)

3 A (9.9 W)

+5VSB

1 A (5 W)

1 A (5 W)

1 A (5 W)

1 A (5 W)

1 A (5 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

199.4 W

223.5 W

246.5 W

271.1 W

295.4 W

% Max Load

44.3%

49.7%

54.8%

60.2%

65.6%

Room Temp.

42.5° C

43.8° C

45.1° C

46.5° C

48.5° C

PSU Temp.

47.4° C

48.0° C

49.0° C

50.2° C

52.1° C

Voltage Regulation

Pass

Pass

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

Pass

Pass

AC Power

257.3 W

290.3 W

321.6 W

355.1 W

386.9 W

Efficiency

77.5%

77.0%

76.6%

76.3%

76.4%

AC Voltage

114.3 V

113.1 V

112.4 V

112.4 V

111.9 V

Power Factor

0.971

0.972

0.973

0.973

0.974

Final Result

Pass

Pass

Pass

Pass

Pass


Input

Test 11

Test 12

Test 13

+12VA

12 A (144 W)

13 A (156 W)

14 A (168 W)

+12VB

11.75 A (141 W)

12.75 A (153 W)

13.5 A (162 W)

+5V

3.5 A (17.5 W)

3.5 A (17.5 W)

4 A (20 W)

+3.3 V

3.5 A (11.55 W)

3.5 A (11.55 W)

4 A (13.2 W)

+5VSB

1 A (5 W)

1 A (5 W)

1 A (5 W)

-12 V

0.5 A (6 W)

0.5 A (6 W)

0.5 A (6 W)

Total

318.3 W

341.0 W

365.6 W

% Max Load

70.7%

75.8%

81.2%

Room Temp.

45.7° C

46.7° C

46.2° C

PSU Temp.

50.3° C

49.3° C

46.7° C

Voltage Regulation

Pass

Pass

Pass

Ripple and Noise

Pass

Pass

Pass

AC Power

421.8 W

453.9 W

489.4 W

Efficiency

75.5%

75.1%

74.7%

AC Voltage

112.2 V

111.5 V

111.8 V

Power Factor

0.975

0.975

0.976

Final Result

Pass

Pass

Pass

The ASUS Atlas A-45GA 450 W can’t deliver its labeled power at high temperatures. The maximum we could pull from it was 365 W. Above that the unit would shut down, meaning that a protection kicked in. At least it won’t burn if you try to pull more than it is capable of delivering.

Efficiency was always below 80% (between 74.1% and 77.5%), proving that the presence of an active PFC circuit has nothing to do with efficiency.

Voltage regulation was the good news about this power supply: all voltages were always within 3% of their nominal values, including the -12 V output. This means that voltages were closer to their nominal values than required, since the ATX12V specification allows a 5% tolerance for the positive voltages and a 10% tolerance for the negative voltages.

Noise and ripple levels are another highlight of the product, always way below the maximum allowed, as you can see in the figures below. As we always point out, the limits are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V and +3.3 V outputs, and all numbers are peak-to-peak figures.

ASUS Atlas A-45GA 450 W power supply
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Figure 18: +12VA input from load tester at 365.6 W (39.2 mV)

ASUS Atlas A-45GA 450 W power supply
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Figure 19: +12VB input from load tester at 365.6 W (38.4 mV)

ASUS Atlas A-45GA 450 W power supply
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Figure 20: +5V rail with power supply delivering 365.6 W (13.4 mV)

ASUS Atlas A-45GA 450 W power supply
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Figure 21: +3.3 V rail with power supply delivering 365.6 W (12.8 mV)

Main Specifications

The ASUS Atlas A-45GA 450 W power supply specs include:

Conclusions

The ASUS Atlas A-45GA 450 W can’t deliver its labeled power. The maximum we could pull from it was 365 W.

On the other hand, voltage regulation was superb, with all voltages closer to their nominal values than required (3% regulation) and with low noise/ripple levels.

Even if this power supply was labeled with its real wattage we wouldn’t be able to recommend it, because its efficiency stayed below 80% all the time.

If you have this power supply you don’t need to worry, because it doesn’t offer any risk of use: as explained, voltages and noise/ripple levels were always within specs, and this unit will shut down if you try to pull more than it is capable of delivering.

Originally at http://www.hardwaresecrets.com/article/ASUS-Atlas-A-45GA-450-W-Power-Supply-Review/1035


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