ASUS Atlas A-45GA 450 W Power Supply Review

[nextpage title=”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.

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

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:

• Main motherboard cable with a 20/24-pin connector, 17” (43 cm) long
• One cable with one ATX12V connector, 17” (43 cm) long
• One cable with one six-pin connector for video cards, 17 3/8” (44 cm) long
• Two cables with two SATA power connectors each, 17 3/8” (44 cm) to the first connector, 5 7/8” (15 cm) between connectors
• One cable with three standard peripheral power connectors, 17 3/8” (44 cm) to the first connector, 5 ½” (140 mm) between connectors
• Two cables with two standard peripheral power connectors and one floppy disk drive power connector each, 17 3/8” (44 cm) to the first connector, 5 ½” (140 mm) between connectors
• One cable with a three-pin fan power connector for you to monitor the speed of the power supply fan through monitoring software, if this connector is installed on the motherboard

This configuration is adequate for a low-end PC.

Figure 3: Cables

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

[nextpage title=”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.

Figure 4: Overall look

Figure 5: Overall look

Figure 6: Overall look

Figure 7: Printed circuit board

[nextpage title=”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.

Figure 8: Transient filtering stage (part 1)

Figure 9: Transient filtering stage (part 2)

[nextpage title=”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.

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 (no
te 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.

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.

Figure 12: Active PFC controller

Figure 13: PWM controller

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

[nextpage title=”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.

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.

Figure 15: Monitoring circuit

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

[nextpage title=”Power Distribution”]

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

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.

Figure 17: Current sensors

The two groups are divided like this:

• +12V1 (solid yellow wire): Main motherboard cable, SATA power cables, and peripheral power cable
• +12V2 (yellow with black stripe wire): ATX12V connector and video card power connector

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.

[nextpage title=”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 po
wer 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.

Figure 18: +12VA input from load tester at 365.6 W (39.2 mV)

Figure 19: +12VB input from load tester at 365.6 W (38.4 mV)

Figure 20: +5V rail with power supply delivering 365.6 W (13.4 mV)

Figure 21: +3.3 V rail with power supply delivering 365.6 W (12.8 mV)

[nextpage title=”Main Specifications”]

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

• ATX12V 2.2
• Nominal labeled power: 450 W
• Measured maximum power: 365.6 W at 46.2° C
• Labeled efficiency: Information not available
• Measured efficiency: Between 74.1% and 77.5%, at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: No
• Motherboard Power Connectors: One 20/24-pin connector and one ATX12V connector
• Video Card Power Connectors: One six-pin connector
• SATA Power Connectors: Four on two cables
• Peripheral Power Connectors: Seven on three cables
• Floppy Disk Drive Power Connectors: Two on two cables
• Protections: Over voltage (OVP), over power (OPP), short-circuit (SCP), and no-load (NLO)
• Warranty: Information not available
• Real Model: Delta GPS-450AP-100
• More Information: https://www.asus.com
• Average price in the US: Product not available in the US market anymore.

[nextpage title=”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.