Corsair CX750M (2021) Power Supply Review

The Corsair CX750M offers much for its price.

Corsair CX750M (2021)
(Image credit: © Tom's Hardware)

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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 tight at 5V, but not as tight on the other rails. 

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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 dead low. The small bulk cap is the restrictive factor here. 

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 current is high with 230V. This is not the case with 115V input. 

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.

Corsair CX750M

(Image credit: Tom's Hardware)

Leakage current is low. 

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.

Swipe to scroll horizontally
Test 12V 5V 3.3V 5VSB DC/AC (Watts) Efficiency Fan Speed (RPM) PSU Noise (dB[A]) Temps (In/Out) PF/AC Volts
10% 4.396A 1.992A 1.985A 0.995A 74.987 84.682% 955 21.3 40.5°C 0.967
Row 2 - Cell 0 12.145V 5.021V 3.324V 5.025V 88.551 Row 2 - Cell 6 Row 2 - Cell 7 Row 2 - Cell 8 45.65°C 115.13V
20% 9.812A 2.989A 2.983A 1.197A 149.899 88.511% 961 21.4 41.26°C 0.983
Row 4 - Cell 0 12.127V 5.018V 3.318V 5.011V 169.356 Row 4 - Cell 6 Row 4 - Cell 7 Row 4 - Cell 8 46.66°C 115.13V
30% 15.594A 3.49A 3.485A 1.4A 224.888 89.239% 963 21.5 42.1°C 0.987
Row 6 - Cell 0 12.110V 5.014V 3.314V 4.998V 252.006 Row 6 - Cell 6 Row 6 - Cell 7 Row 6 - Cell 8 47.91°C 115.12V
40% 21.399A 3.991A 3.989A 1.604A 299.965 89.127% 964 21.5 42.88°C 0.989
Row 8 - Cell 0 12.093V 5.011V 3.309V 4.986V 336.559 Row 8 - Cell 6 Row 8 - Cell 7 Row 8 - Cell 8 49.01°C 115.12V
50% 26.812A 4.992A 4.995A 1.81A 374.226 88.478% 969 21.7 43.51°C 0.99
Row 10 - Cell 0 12.074V 5.008V 3.303V 4.971V 422.961 Row 10 - Cell 6 Row 10 - Cell 7 Row 10 - Cell 8 50.39°C 115.12V
60% 32.298A 5.994A 6.004A 2A 449.06 87.607% 973 21.8 43.89°C 0.991
Row 12 - Cell 0 12.055V 5.005V 3.298V 4.956V 512.586 Row 12 - Cell 6 Row 12 - Cell 7 Row 12 - Cell 8 51.41°C 115.11V
70% 37.804A 6.997A 7.017A 2.225A 524.076 86.399% 1253 29.6 44.02°C 0.992
Row 14 - Cell 0 12.035V 5.003V 3.292V 4.941V 606.58 Row 14 - Cell 6 Row 14 - Cell 7 Row 14 - Cell 8 52.24°C 115.11V
80% 43.394A 8.001A 8.029A 2.332A 599.283 85.232% 1729 39.4 44.58°C 0.992
Row 16 - Cell 0 12.016V 5V 3.286V 4.928V 703.117 Row 16 - Cell 6 Row 16 - Cell 7 Row 16 - Cell 8 53.67°C 115.11V
90% 49.339A 8.504A 8.528A 2.439A 674.307 83.908% 2104 46.7 44.66°C 0.993
Row 18 - Cell 0 11.995V 4.996V 3.282V 4.917V 803.628 Row 18 - Cell 6 Row 18 - Cell 7 Row 18 - Cell 8 54.26°C 115.1V
100% 55.106A 9.01A 9.059A 3.063A 749.536 82.41% 2362 48.9 45.57°C 0.993
Row 20 - Cell 0 11.974V 4.993V 3.277V 4.896V 909.522 Row 20 - Cell 6 Row 20 - Cell 7 Row 20 - Cell 8 55.66°C 115.09V
110% 60.749A 10.014A 10.171A 3.069A 824.561 80.803% 2358 48.5 46.75°C 0.994
Row 22 - Cell 0 11.955V 4.992V 3.273V 4.886V 1020.459 Row 22 - Cell 6 Row 22 - Cell 7 Row 22 - Cell 8 57.68°C 115.09V
CL1 0.114A 15.542A 15.638A 0A 131.265 81.33% 985 22.2 43.16°C 0.983
Row 24 - Cell 0 12.118V 5.038V 3.299V 5.009V 161.398 Row 24 - Cell 6 Row 24 - Cell 7 Row 24 - Cell 8 50.18°C 115.14V
CL2 0.113A 19.781A 0A 0A 101.375 81.919% 983 22.1 44.21°C 0.979
Row 26 - Cell 0 12.135V 5.055V 3.312V 5.026V 123.75 Row 26 - Cell 6 Row 26 - Cell 7 Row 26 - Cell 8 52.43°C 115.14V
CL3 0.113A 0A 19.932A 0A 67.364 74.448% 962 21.5 44.82°C 0.968
Row 28 - Cell 0 12.135V 5.016V 3.311V 5.025V 90.486 Row 28 - Cell 6 Row 28 - Cell 7 Row 28 - Cell 8 53.88°C 115.14V
CL4 62.516A 0A 0A 0A 749.364 83.173% 2377 50.3 45.63°C 0.993
Row 30 - Cell 0 11.987V 4.992V 3.296V 4.972V 900.984 Row 30 - Cell 6 Row 30 - Cell 7 Row 30 - Cell 8 55.77°C 115.09V

This might be a budget PSU, but it doesn't have a problem operating at high temperatures. It is impressive to see this platform coping with full and 110% load at close to 47 degrees Celsius! Usually, we don't push budget units beyond 40 degrees Celsius. 

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.

Swipe to scroll horizontally
Test 12V 5V 3.3V 5VSB DC/AC (Watts) Efficiency Fan Speed (RPM) PSU Noise (dB[A]) Temps (In/Out) PF/AC Volts
20W 1.220A 0.498A 0.495A 0.198A 19.983 68.678% 946 21.0 37.21°C 0.902
Row 2 - Cell 0 12.158V 5.023V 3.33V 5.048V 29.097 Row 2 - Cell 6 Row 2 - Cell 7 Row 2 - Cell 8 40.32°C 115.14V
40W 2.688A 0.697A 0.694A 0.297A 39.984 79.05% 947 21.0 37.35°C 0.948
Row 4 - Cell 0 12.154V 5.022V 3.328V 5.044V 50.581 Row 4 - Cell 6 Row 4 - Cell 7 Row 4 - Cell 8 40.85°C 115.14V
60W 4.158A 0.896A 0.892A 0.397A 59.984 84.058% 950 21.1 38.6°C 0.963
Row 6 - Cell 0 12.149V 5.021V 3.327V 5.04V 71.36 Row 6 - Cell 6 Row 6 - Cell 7 Row 6 - Cell 8 42.61°C 115.14V
80W 5.623A 1.095A 1.091A 0.496A 79.917 85.755% 953 21.2 39.69°C 0.969
Row 8 - Cell 0 12.145V 5.02V 3.325V 5.035V 93.192 Row 8 - Cell 6 Row 8 - Cell 7 Row 8 - Cell 8 44.29°C 115.13V

At light loads the fan spins at low RPM, keeping noise output equally low. 

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.

Swipe to scroll horizontally
12V 5V 3.3V 5VSB DC/AC (Watts) Efficiency Fan Speed (RPM) PSU Noise (dB[A]) Temps (In/Out) PF/AC Volts
1.047A 0.264A 0.264A 0.051A 15.195 62.928% 909 20.1 21.61°C 0.88
Row 2 - Cell 0 12.158V 5.025V 3.333V 5.054V 24.147 Row 2 - Cell 6 Row 2 - Cell 7 24.1°C 115.14V

Efficiency at super light loads is high enough. 

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.

Efficiency with normal levels is decent, while it could be a bit higher with super-light loads. The PF readings are high, as well. 

5VSB Efficiency

Swipe to scroll horizontally
Test # 5VSB DC/AC (Watts) Efficiency PF/AC Volts
1 0.1A 0.505W 75.862% 0.074
Row 2 - Cell 0 5.056V 0.666W Row 2 - Cell 3 115.12V
2 0.25A 1.262W 78.943% 0.16
Row 4 - Cell 0 5.054V 1.599W Row 4 - Cell 3 115.12V
3 0.55A 2.775W 79.961% 0.27
Row 6 - Cell 0 5.048V 3.47W Row 6 - Cell 3 115.12V
4 1A 5.038W 80.498% 0.348
Row 8 - Cell 0 5.039V 6.259W Row 8 - Cell 3 115.12V
5 1.5A 7.542W 79.361% 0.393
Row 10 - Cell 0 5.029V 9.503W Row 10 - Cell 3 115.12V
6 2.999A 15W 78.064% 0.45
Row 12 - Cell 0 5.002V 19.215W Row 12 - Cell 3 115.12V

The 5VSB rail is efficient. 

Power Consumption In Idle And Standby

Swipe to scroll horizontally
Mode 12V 5V 3.3V 5VSB Watts PF/AC Volts
Idle 12.162V 5.026V 3.336V 5.059V 4.673 0.413
Row 2 - Cell 0 Row 2 - Cell 1 Row 2 - Cell 2 Row 2 - Cell 3 Row 2 - Cell 4 Row 2 - Cell 5 115.1V
Standby Row 3 - Cell 1 Row 3 - Cell 2 Row 3 - Cell 3 Row 3 - Cell 4 0.049 0.005
Row 4 - Cell 0 Row 4 - Cell 1 Row 4 - Cell 2 Row 4 - Cell 3 Row 4 - Cell 4 Row 4 - Cell 5 115.1V

We would like to see below 0.1W vampire power 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).

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

The fan speed profile is not aggressive, at high operating temperatures. Up to 450W loads, the fan rotates at low speeds, so noise output is minimal. 

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

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

At normal operating temperatures, close to 30 degrees Celsius, the PSU is silent with up to 440-450W loads. If you push it with more than 580W, it will exceed 40 dBA, and for a brief part, it goes over 45 dBA. 

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Aris Mpitziopoulos
Contributing Editor

Aris Mpitziopoulos is a contributing editor at Tom's Hardware, covering PSUs.

  • Co BIY
    Another great review!

    Why do you prefer a full modular cable set up to this semi-modular ? At this price point I think semi-modular is "best". One less failure point and greater efficiency. I don't think custom cabling is a consideration for this range. I think Semi-modular should be considered best practice outside of Vanity/RGB/Bling focused lines.

    For appearance sake I do think the exit point of a semi-modular "main cable" of could be made to visually match the other cables without giving up the advantages.
    Reply