[nextpage title=”Introduction”]
ASUS is the number on motherboard manufacturer in the world and they’ve been expanding to other business for several years, recently reaching the power supply market. Though ASUS power supplies are not sold in the US, this didn’t prevent us from getting our hands on their 650 W product, which is sold throughout the world. Like the 500 W (P-50GA) model we already reviewed this unit is manufactured by Delta Electronics. Does this power supply carry ASUS high-quality standards? Let’s see.
Figure 1: ASUS U-65GA 650 W power supply.
Figure 2: ASUS U-65GA 650 W power supply.
U-65GA is 6 1/8” (15.5 cm) deep, having a 120 mm fan on its bottom, active PFC and no modular cabling system.
All cables have a nylon protection, but the sleevings don’t come from inside the power supply, as you can see in Figure 2. The cables included on U-65GA are:
- Main motherboard cable with a 24-pin connector (no 20-pin option).
- One EPS12V cable.
- One ATX12V cable.
- One cable with two six/eight-pin auxiliary power connectors for video cards.
- Two SATA power cables with three plugs each.
- Two peripheral power cables with three standard peripheral power plugs and one floppy disk drive power connector each.
This model brings two SATA plugs and one floppy disk drive power connector more than the 500 W model from ASUS (P-50GA).
The cables are somewhat short, having 19” (48 cm) between the power supply housing and the first connector on the cable and 5 7/8” (15 cm) between connectors, on cables with more than one connector. The length of the cables may make it difficult for you to use this power supply inside a full tower case or even on a mid-tower case where the power supply is installed on the bottom of the case.
Almost all wires are 18 AWG. The main motherboard cable uses thicker 16 AWG wires on the +3.3 V outputs, which is always nice to see. This is a step up to the 500 W model, which uses thinner 20 AWG wires on the ATX12V/EPS12V cable.
The number of connectors available is enough for you to build a mainstream PC, but the two video card power connectors available are installed on the same cable, which isn’t the best configuration: it is always better to see them using individual cables.
Figure 3: Cables.
Now let’s take an in-depth look inside this power supply.
[nextpage title=”A Look Inside The U-65GA”]
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.
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.
The first thing we noticed about this power supply is that it does not use the same printed circuit board from the 500 W model (P-50GA), so the 650 W model is not the 500 W model with stronger components.
Figure 4: Overall look.
Figure 5: Overall look.
Figure 6: Overall look.
[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.
This power supply has two X capacitors and four Y capacitors more than the minimum required plus one X capacitor after the rectification bridge, but it doesn’t come with a MOV, which is a sin. This component is in charge of surge protection. We expected it to have one, since it carries the name ASUS.
Figure 7: Transient filtering stage (part 1).
Figure 8: Transient filtering stage (part 2).
In the next page we will have a more detailed discussion about the components used in the ASUS U-65GA.[nextpage title=”Primary Analysis”]
On this page we will take an in-depth look at the primary stage of ASUS U-65GA. For a better understanding, please read our Anatomy of Switching Power Supplies tutorial.
This power supply uses one D25XB60 rectifying bridge in its primary. Each bridge can deliver up to 25 A at 98° C if a heatsink is used (which is the case) or up to 3.5 A at 25° C is a heatsink is not used. So in theory you would be able to pull up to 2,875 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 2,300 W without burning itself out. Talk about overspecification! 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 9: Rec
tifying bridge.
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.
This power supply uses two electrolytic capacitors to filter the output from the active PFC circuit. The use of more than one capacitor here has absolute nothing to do with the “quality” of the power supply, as laypersons may assume (including people without the proper background in electronics doing power supply reviews around the web). Instead of using one big capacitor, manufacturers may choose to use two or more smaller components that will give the same total capacitance, in order to better accommodate space on the printed circuit board, as two or more capacitors with small capacitance are physically smaller than one capacitor with the same total capacitance. U-65GA uses two 270 µF x 450 V capacitors in parallel; this is equivalent of one 540 µF x 450 V capacitor.
These electrolytic capacitors are Chinese, from Aishi and rated at 85° C.
In the switching section, another two SPW20N60C3 power MOSFET transistors are used.
Figure 10: Switching transistor and active PFC diode and transistors. The other switching transistor is located on the other side of the heatsink.
Instead of using one PFC/PWM combo chip, this power supply uses separated controllers. For controlling the active PFC circuit one ICE1PCS02 PFC controller is used, while for controlling the switching transistors one UC3845B PWM controller is used.
Figure 11: PFC/PWM controller.
Although the active PFC and switching transistors are identical to the ones used on the 500 W (P-50GA) model, the PFC controller is different.
Now let’s take a look at the secondary of this power supply.[nextpage title=”Secondary Analysis”]
ASUS U-65GA uses four Schottky rectifiers on the secondary, plus an LM7912 voltage regulator to regulate 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 produced by two S60SC6M Schottky rectifiers (60 A, 30 A per internal diode at 118° C, 0.67 V voltage drop) connected in parallel, giving us a maximum theoretical current of 86 A or 1,029 W for the +12 V output. Talk about overspecification!
The +5 V output is produced by one STPS40L45CW Schottky rectifier (40 A, 20 A per internal diode at 130° C, maximum forward voltage of 0.49 V). This gives us a maximum theoretical current of 29 A or 143 W for the +5 V output.
The +3.3 V output is produced by another STPS40L45CW Schottky rectifier, giving us a maximum theoretical current of 29 A or 94 W for the +3.3 V output.
Figure 12: -12 V voltage regulator and rectifiers.
Instead of using a monitoring integrated circuit this power supply implements a discrete solution, so we couldn’t check what protections this power supply really has. The daughterboard located on the secondary is in charge of providing the protections, controlling the fan, generating the power good signal and turning the power supply on and off.
Figure 13: Secondary daughterboard.
Some electrolytic capacitors from the secondary are Japanese from Rubycon and Chemi-Con, but not all; some are from Ltec and CapXon. They are all labeled at 105° C, as usual.
[nextpage title=”Power Distribution”]
In Figure 14, you can see the power supply label containing all the power specs.
Figure 14: Power supply label.
This power supply has three rails, distributed like this:
- +12V1 (solid yellow wire): Main motherboard, SATA and peripheral power connectors.
- +12V2 (yellow wire with black stripe): ATX12V/EPS12V connectors.
- +12V3 (solid yellow wire): Video card power connectors.
This distribution is perfect, as it separates the CPU (ATX12V/EPS12V), the video card and all the rest on different rails.
Now let’s see if this power supply can really deliver 650 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 power being delivered, as measured by our load tester.
The +12V1 and +12V2 inputs listed below are the two +12 V independent inputs from our load tester and during all tests the +12V1 input was connected to the power supply +12V1 and +12V3
rails while the +12V2 input was connected to the power supply +12V2 rail.
| Input | Test 1 | Test 2 | Test 3 | Test 4 | Test 5 |
| +12V1 | 5 A (60 W) | 10 A (120 W) | 15 A (180 W) | 16 A (192 W) | 18 A (216 W) |
| +12V2 | 5 A (60 W) | 10 A (120 W) | 15 A (180 W) | 16 A (192 W) | 18 A (216 W) |
| +5V | 1 A (5 W) | 2 A (10 W) | 4 A (20 W) | 16 A (80 W) | 25 A (125 W) |
| +3.3 V | 1 A (3.3 W) | 2 A (6.6 W) | 4 A (13.2 W) | 16 A (52.8 W) | 25 A (82.5 W) |
| +5VSB | 1 A (5 W) | 1 A (5 W) | 1.5 A (7.5 W) | 2 A (10 W) | 2.5 A (12.5 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 | 140.2 W | 269.0 W | 396.0 W | 531.9 W | 653.8 W |
| % Max Load | 21.6% | 41.4% | 60.9% | 81.8% | 100.6% |
| Room Temp. | 44.6° C | 44.8° C | 45.9° C | 48.6° C | 49.4° C |
| PSU Temp. | 47.3° C | 47.2° C | 47.6° C | 49.7° C | 57.1° C |
| Voltage Stability | Pass | Pass | Pass | Pass | Pass |
| Ripple and Noise | Pass | Pass | Pass | Pass | Pass |
| AC Power | 167.7 W | 314.7 W | 468.3 W | 661.0 W | 863.0 W |
| Efficiency | 83.6% | 85.5% | 84.6% | 80.5% | 75.8% |
| AC Voltage | 112.9 V | 111.0 V | 109.7 V | 109.0 V | 104.9 V |
| Power Factor | 0.990 | 0.996 | 0.997 | 0.997 | 0.998 |
| Final Result | Pass | Pass | Pass | Pass | Pass |
ASUS U-65G would not turn on if we tried to pull more than 18 A from each +12 V input from our load tester. With the over current protection configured so tight, we had to use a different load pattern for tests four and five from what we usually use. We like to test power supplies pulling more current/power from its +12 V outputs, since this reflects a modern PC (as the video card and the CPU, which are the components that most consume power in the computer, are fed from these outputs). But due to this limitation, we had to increase a lot current on +5 V and +3.3 V outputs in order to achieve the desired power.
The reviewed power supply could really deliver 650 W at 49° C, but with the limitation explained above.
With the 500 W power supply from ASUS we had a problem where the unit could not deliver efficiency above 80% in most scenarios. With U-65GA, however, you will see efficiency below 80% only when you try to pull its full labeled power. If you pull between 40% and 60% (260 W and 390 W) from its labeled power, you will achieve an excellent efficiency of 85%. At 20% load (130 W) efficiency is still very good, at 83.6%. At 80% load (520 W) efficiency drops to 81.8%, but still above the 80% mark.
This unit is 80 Plus-certified, but you need to keep in mind that this organization tests power supplies at 23° C (a temperature that is too low in our opinion), while we tested this power supply at 49.4° C. The higher the temperature, the lower efficiency is.
Voltage regulation was one of the highlights from U-65GA, with all voltages within 3% from their nominal values, i.e., closer to their nominal values than required, as the ATX specification allows voltages to be up to 5% from their nominal values. This includes -12 V, an output that usually doesn’t like to stay so close to its nominal value.
Noise and ripple levels stayed inside the allowed range (up to 120 mV for +12 V and up to 50 mV for +5 V and +3.3 V, peak-to-peak), however higher than we’d like to see.
Figure 15: +12V1 input from load tester at 653.8 W (67.4 mV).
Figure 16: +5V rail with power supply delivering 653.8 W (25.8 mV).
Figure 17: +3.3 V rail with power supply delivering 653.8 W (32.8 mV).
Let’s see if we could pull more than 650 W from the reviewed unit.
[nextpage title=”Overload Tests”]
As you know by now, before overloading a power supply we like to see if the over current protection is active and its trigger point. Do test this we set current at +12V1 at 1 A and increased current on +12V2 until the power supply shut down. This happened when we tried to pull more than 18 A from the +12V2 rail. It was nice to see the OCP circuit configured at a value close to what is printed on the label (16 A).
Then starting from test five we increased current on all outputs until we reached the maximum the power supply could deliver still working inside ATX specs. The result you can see below. If we increased one amp on any output the power supply would shut down.
The main goal of our overload test is to see if the power supply burns or explodes and if its protections are active. Thus ASUS U-65GA passed this test.
Even though ASUS U-65GA has its protections working well, we could only overload this unit 8% from its labeled value, and under this maximum overloading voltages at +5 V and +3.3 V outputs were out of spec. Of course you should not operate this unit above 650 W.
| Input | Maximum |
| +12V1 | 18 A (216 W) |
| +12V2 | 18 A (216 W) |
| +5V | 32 A (160 W) |
| +3.3 V | 32 A (105.6 W) |
| +5VSB | 2.5 A (12.5 W) |
| -12 V | 0.5 A (6 W) |
| Total | 702.0 W |
| % Max Load | 108.0% |
| Room Temp. | 49.1° C |
| PSU Temp. | 58.6° C |
| AC Power | 963.0 W |
| Efficiency | 72.9% |
| AC Voltage | 103.7 V |
| Power Factor | 0.998 |
[nextpage title=”Main Specifications”]
ASUS U-65GA power supply specs include:
- ATX12V 2.2
- Nominal labeled power: 650 W.
- Measured maximum power: 702.0 W at 49.1° C.
- Labeled efficiency: 86% maximum, 80 Plus certified
- Measured efficiency: Between 75.8% and 85.5% at 115 V (nominal, see complete results for actual voltage).
- Active PFC: Yes.
- Modular Cabling System: No.
- Motherboard Power Connectors: One 24-pin connector, one ATX12V connector and one EPS12V connector.
- Video Card Power Connectors: Two six/eight-pin connectors in one cable.
- SATA Power Connectors: Six in two cables.
- Peripheral Power Connectors: Six in two cables.
- Floppy Disk Drive Power Connectors: Two in two cables.
- Protections: Over current (tested and working), over voltage (OVP, not tested), under voltage (UVP, not tested), over power (OPP, not tested), over temperature (OTP), no load (NLO) and short-circuit (SCP, tested and working) protections.
- Warranty: N/A.
- Real Manufacturer: Delta Electronics
- More Information: https://www.asus.com
- Average price in the US: We couldn’t find this product being sold in the USA.
[nextpage title=”Conclusions”]
The good news about ASUS U-65GA is that it is better than the 500 W model (P-50GA) from the same brand (which is a product we don’t recommend), presenting high efficiency (especially if you pull between 40% and 60% from its labeled capacity, i.e., between 260 W and 390 W) and six SATA power connectors. Pulling 650 W from it efficiency drops below 80%, but since most users will not pull 650 W from it this is not a problem.
Voltage regulation was the highlight from U-65GA, with all voltages within 3% from their nominal values, i.e., closer to their nominal values than required, as the ATX specification allows voltages to be up to 5% from their nominal values. This includes -12 V, an output that usually doesn’t like to stay so close to its nominal value.
ASUS U-65GA can really deliver 650 W at 49° C and has its protections working fine, but it isn’t the best 650 W power supply around: ripple and noise although inside specs were higher than competing products and we think it would be better to have the two power connectors for video cards in separated cables.
It is an honest power supply for its price and will present an excellent performance if you put it to work between 260 W and 390 W; because of that we are giving it our Hardware Secrets Bronze Award.
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