Asus TUF Gaming 550W Bronze Power Supply Review

To learn more about our PSU tests and methodology, please check out How We Test Power Supply Units. 

Primary Rails And 5VSB Load Regulation

The following charts show the main rails’ voltage values recorded between a range of 40W up to the PSU’s maximum specified load, along with the deviation (in percent). Tight regulation is an important consideration every time we review a power supply because it facilitates constant voltage levels despite varying loads. 

Tight load regulation also, among other factors, improves the system’s stability, especially under overclocked conditions and, at the same time, it applies less stress to the DC-DC converters that many system components utilize.

Load regulation is decent at 12V and tight on the other rails. The fixed cables help in load regulation because they don’t have the increased resistance of the modular ones. 

Hold-Up Time

Put simply; hold-up time is the amount of time that the system can continue to run without shutting down or rebooting during a power interruption.

The hold-up time is too short. Asus had to use a low-capacity bulk cap to keep the cost low. 

Inrush Current

Inrush current, or switch-on surge, refers to the maximum, instantaneous input current drawn by an electrical device when it is first turned on. A large enough inrush current can cause circuit breakers and fuses to trip. It can also damage switches, relays, and bridge rectifiers. As a result, the lower the inrush current of a PSU, right as it is turned on, the better.

Inrush currents are high. 

Leakage Current

In layman’s terms, leakage current is the unwanted transfer of energy from one circuit to another. In power supplies, it is the current flowing from the primary side to the ground or the chassis, which in the majority of cases is connected to the ground. For measuring leakage current, we use a GW Instek GPT-9904 electrical safety tester instrument.

The leakage current test is conducted at 110% of the DUT’s rated voltage input (so for a 230-240V device, we should conduct the test with 253-264V input). The maximum acceptable limit of a leakage current is 3.5 mA and it is defined by the IEC-60950-1 regulation, ensuring that the current is low and will not harm any person coming in contact with the power supply’s chassis.

Leakage current is far below the 3.5 mA limit. 

10-110% Load Tests

These tests reveal the PSU’s load regulation and efficiency levels under high ambient temperatures. They also show how the fan speed profile behaves under increased operating temperatures.

The PSU doesn’t have a problem delivering full load and even more at high operating temperatures. Efficiency gets a big hit, though. 

20-80W Load Tests

In the following tests, we measure the PSU’s efficiency at loads significantly lower than 10% of its maximum capacity (the lowest load the 80 PLUS standard measures). This is important for representing when a PC is idle with power-saving features turned on.

The fan doesn’t spin at light loads. 

2% or 10W Load Test

From July 2020, the ATX spec requires 70% and higher efficiency with 115V input. The applied load is only 10W for PSUs with 500W and lower capacities, while for stronger units, we dial 2% of their max-rated capacity.

The 60% mark is passed with a 2 % load. 

Efficiency & Power Factor

Next, we plotted a chart showing the PSU’s efficiency at low loads and loads from 10 to 110% of its maximum rated capacity. The higher a PSU’s efficiency, the less energy goes wasted, leading to a reduced carbon footprint and lower electricity bills. The same goes for Power Factor.

The platform is efficient, especially with 230V input, which is why it has a Silver rating in the Cybenetics scheme. 

5VSB Efficiency

The 5VSB rail achieves decent efficiency. 

Power Consumption In Idle And Standby

Vampire power is low with 115V input, but we would like to see below 0.1W with 230V input. 

Fan RPM, Delta Temperature, And Output Noise

All results are obtained between an ambient temperature of 37 to 47 degrees Celsius (98.6 to 116.6 degrees Fahrenheit).

The fan speed profile doesn’t seem aggressive at harsh conditions. 

The following results were obtained at 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit) ambient temperature.       

At normal operating temperatures, close to 30 degrees Celsius, the PSU’s semi-passive operation doesn’t last long if you push hard the minor rails. There is also a region where the fan spins, even with a minimal load on the minor rails. With more than 160W, noise exceeds 25 dBA, and with more than 300W, the 30 dBA mark is passed. Lastly, with higher than 360W noise is within the 35-40 dBA region. 

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Protection Features

Check out our PSUs 101 article to learn more about PSU protection features.

The OCP triggering points are set high on all rails, especially the minor ones. Great Wall ignored setting up the minor rails properly. Who needs so many amps on them? On the contrary, the over power protection is set correctly.

DC Power Sequencing

According to Intel’s most recent Power Supply Design Guide (revision 1.4), the +12V and 5V outputs must be equal to or greater than the 3.3V rail at all times. Unfortunately, Intel doesn’t mention why it is so important to always keep the 3.3V rail’s voltage lower than the levels of the other two outputs.

No problems here since the 3.3V rail is always lower than the other two. 

Cross Load Tests

To generate the following charts, we set our loaders to auto mode through custom-made software before trying more than 25,000 possible load combinations with the +12V, 5V, and 3.3V rails. The deviations in each of the charts below are calculated by taking the nominal values of the rails (12V, 5V, and 3.3V) as point zero. The ambient temperature during testing was between 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit).

Load Regulation Charts

Efficiency Graph

Ripple Graphs

The lower the power supply’s ripple, the more stable the system will be and less stress will also be applied to its components.

Infrared Images

We apply a half-load for 10 minutes with the PSU’s top cover and cooling fan removed before taking photos with a modified Fluke Ti480 PRO camera able to deliver an IR resolution of 640×480 (307,200 pixels).

We didn’t notice any high temperature spots inside the PSU, during this test session. 

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Advanced Transient Response Tests

For details about our transient response testing, please click here.

In the real world, power supplies are always working with loads that change. It’s of immense importance, then, for the PSU to keep its rails within the ATX specification’s defined ranges. The smaller the deviations, the more stable your PC will be with less stress applied to its components. 

We should note that the ATX spec requires capacitive loading during the transient rests, but in our methodology, we also choose to apply a worst case scenario with no additional capacitance on the rails. 

Advanced Transient Response at 20% – 20ms

Advanced Transient Response at 20% – 10ms

Advanced Transient Response at 20% – 1ms

Advanced Transient Response at 50% – 20ms

Advanced Transient Response at 50% – 10ms

Advanced Transient Response at 50% – 1ms

Transient response is mediocre on all rails but 5VSB, where it doesn’t matter so much. 

Turn-On Transient Tests

In the next set of tests, we measure the PSU’s response in simpler transient load scenarios—during its power-on phase. Ideally, we don’t want to see any voltage overshoots or spikes since those put a lot of stress on the DC-DC converters of installed components.

There is a huge voltage drop in the “PSU OFF To Full 12V” test, showing that something is off with the resonant controller’s programming. 

Power Supply Timing Tests

There are several signals generated by the power supply, which need to be within specified, by the ATX spec, ranges. If they are not, there can be compatibility issues with other system parts, especially mainboards. From year 2020, the PSU’s Power-on time (T1) has to be lower than 150ms and the PWR_OK delay (T3) from 100 to 150ms, to be compatible with the Alternative Sleep Mode.

The PWR_OK delay is within the 100-150ms region, so the PSU supports the alternative sleep mode recommended by the ATX spec.

Ripple Measurements

Ripple represents the AC fluctuations (periodic) and noise (random) found in the PSU’s DC rails. This phenomenon significantly decreases the capacitors’ lifespan because it causes them to run hotter. A 10-degree Celsius increase can cut into a cap’s useful life by 50%. Ripple also plays an important role in overall system stability, especially when overclocking is involved.

The ripple limits, according to the ATX specification, are 120mV (+12V) and 50mV (5V, 3.3V, and 5VSB).

Ripple suppression is good on all major rails. The 5VSB needs a better filtering cap. 

Ripple At Full Load

Ripple At 110% Load

Ripple At Cross-Load 1

Ripple At Cross-Load 4

EMC Pre-Compliance Testing – Average & Quasi-Peak EMI Detector Results

Electromagnetic Compatibility (EMC) is the ability of a device to operate properly in its environment without disrupting the proper operation of other nearby devices.

Electromagnetic Interference (EMI) stands for the electromagnetic energy a device emits, and it can cause problems in other nearby devices if too high. For example, it can cause increased static noise in your headphones or/and speakers.

΅We use TekBox’s EMCview to conduct our EMC pre-compliance testing.

A single spur exceeds the limits of the average and peak EMI detectors. Conducted EMI is low in all other frequencies. 

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Performance Rating

The TUF 550 achieves high performance, but despite its modern platform, is cannot take the lead from the Corsair, XPG, and Thermaltake units that use less advanced platforms, all provided by Channel Well Technology. 

Noise Rating

The graph below depicts the cooling fan’s average noise over the PSU’s operating range, with an ambient temperature between 30 to 32 degrees Celsius (86 to 89.6 degrees Fahrenheit).

Under normal operating temperatures, the average noise output is low for the standards of this category, but the CX550M puts it to shame, along with all other similar spec PSUs. 

Efficiency Rating

The following graph shows the PSU’s average efficiency throughout its operating range with an ambient temperature close to 30 degrees Celsius.

We expected that this platform would achieve first place in this chart. The CX550M is not far behind, though. 

Power Factor Rating

The following graphs show the PSU’s average power factor reading throughout its operating range with an ambient temperature close to 30 degrees Celsius and 115V/230V voltage input. 

The APFC converter does a decent job with 115V but needs tuning for higher PF readings with 230V. 

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Corsair decided to withdraw its popular CX line because it was expensive to make while it addressed budget-oriented users. ASUS saw an opportunity there, grabbed the CX platform from Great Wall, and used it in its TUF Gaming PSUs. 

The problem is that they were forced to use inferior components compared to the CX units to keep the cost down, which affected performance. The cost of electronic parts has hugely increased in the last years, primarily because of the pandemic, so it is not easy to use quality parts in budget PSUs. 

The TUF 550 achieves good overall performance, which could be even higher with more tuning and changes in its design. Great Wall has to proceed with some changes at some point if it wants to keep up with the competition. Although this is the most modern platform in the low-cost category, it still cannot surpass, in overall performance, the less advanced CWT CSB platform used in the XPG Pylon 550, the Corsair CX550M, and the Thermaltake Smart BM2 550. 

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Disclaimer: Aris Mpitziopoulos is Tom’s Hardware’s PSU reviewer. He is also the Chief Testing Engineer of Cybenetics and developed the Cybenetics certification methodologies apart from his role on Tom’s Hardware. Neither Tom’s Hardware nor its parent company, Future PLC, are financially involved with Cybenetics. Aris does not perform the actual certifications for Cybenetics.