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Corsair CX750F RGB Power Supply Review

The Corsair CX750F brings more RGB lighting to your system.

Corsair CX750F RGB
(Image: © Tom's Hardware)

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 loose on all rails. 

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 lower than 17ms, as expected given the low capacity bulk cap. The power ok signal's hold-up time is low, too, but it is accurate, at least. 

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 at normal levels with 115V, but pretty high with 230V 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 CX750F

(Image credit: Tom's Hardware)

Leakage current is dead low, and this is a good thing. 

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.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])Temps (In/Out)PF/AC Volts
14.385A1.985A1.977A0.996A74.96984.504%69715.840.38°C0.980
12.171V5.038V3.337V5.021V88.71645.20°C115.12V
29.808A2.987A2.976A1.198A150.04588.569%71816.540.69°C0.980
12.148V5.021V3.327V5.008V169.41146.44°C115.12V
315.590A3.494A3.481A1.402A225.05489.582%75819.141.52°C0.979
12.123V5.009V3.319V4.995V251.22848.36°C115.12V
421.398A4.000A3.988A1.606A300.07089.734%83623.241.64°C0.984
12.098V4.998V3.311V4.982V334.40049.15°C115.12V
526.847A5.020A4.997A1.812A374.65389.340%93026.442.36°C0.987
12.074V4.981V3.301V4.968V419.35750.57°C115.12V
632.345A6.047A6.017A2.000A449.51188.634%107530.842.76°C0.986
12.051V4.963V3.291V4.954V507.15751.88°C115.11V
737.898A7.079A7.041A2.228A524.91887.743%124436.943.49°C0.988
12.027V4.946V3.281V4.939V598.24653.37°C115.11V
843.480A8.003A8.071A2.438A599.65586.715%145039.743.64°C0.989
12.001V4.929V3.271V4.924V691.52354.37°C115.11V
949.452A8.650A8.582A2.442A674.76085.655%166543.844.24°C0.991
11.976V4.915V3.263V4.916V787.76255.87°C115.11V
1055.251A9.185A9.130A3.068A749.99084.354%186145.845.69°C0.992
11.950V4.902V3.254V4.891V889.09458.26°C115.11V
1161.694A9.198A9.149A3.072A825.18682.850%211648.746.59°C0.993
11.921V4.895V3.247V4.883V995.99860.42°C115.14V
CL10.102A16.004A15.999A0.000A131.84981.416%118135.442.93°C0.968
12.162V4.877V3.285V5.006V161.94551.24°C115.13V
CL262.522A1.000A0.999A1.000A759.88084.829%183245.546.09°C0.992
11.942V4.994V3.285V4.967V895.78058.31°C115.10V

The PSU can handle tough situations, but expect a big impact on efficiency, at high loads. The fan's noise will also get loud, very loud. 

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.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])PF/AC Volts
11.219A0.494A0.492A0.198A20.00268.944%71816.50.910
12.188V5.058V3.347V5.050V29.012115.13V
22.437A0.990A0.988A0.397A39.99078.890%69715.80.955
12.181V5.051V3.343V5.042V50.691115.13V
33.661A1.487A1.481A0.596A60.01982.955%67816.20.972
12.175V5.044V3.340V5.034V72.351115.12V
44.879A1.986A1.977A0.796A79.96985.238%67716.20.979
12.168V5.038V3.336V5.026V93.819115.12V

Given the low efficiency certifications, on both 80 PLUS and Cybenetics, it scores pretty well with 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.

Test #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])PF/AC Volts
11.048A0.263A0.265A0.050A15.22763.631%479<6.00.877
12.173V5.060V3.346V5.052V23.930115.12V

With over 60% efficiency with a 2% load, it meets the corresponding ATX spec requirement. 

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.

Compared to similar spec PSUs, the CX750F scores well in all areas but super-light loads. The average PF readings are also high, even with 230V input. 

5VSB Efficiency

Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts
10.100A0.50573.615%0.079
5.048V0.686115.12V
20.250A1.26277.662%0.170
5.044V1.625115.12V
30.550A2.77179.149%0.282
5.037V3.501115.12V
41.000A5.02679.740%0.362
5.025V6.303115.12V
51.500A7.52079.392%0.406
5.013V9.472115.12V
63.001A14.93177.012%0.463
4.975V19.388115.12V

The 5VSB rail has decent efficiency.

Power Consumption In Idle And Standby

Mode12V5V3.3V5VSBWattsPF/AC Volts
Idle12.174V5.062V3.346V5.054V6.8930.471
115.1V
Standby0.0570.007
115.1V

Vampire power is low. 

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 increases linearly under harsh operating conditions. Given the PSU's efficiency levels and the applied conditions, we cannot call the fan speed profile aggressive. 

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 average operating temperatures, close to 30 degrees Celsius, the PSU is silent at up to typical loads. The 30 dBA mark is passed with 425W, and the PSU enters the 40-45 dBA zone with 595W. Our take here is that the fan speed profile could be more relaxed under average operating temperatures. 

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Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.