Corsair CX650 Power Supply Review

Capable for the mid-range

Corsair CX650 PSU
(Image: © 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, especially at 12V where it matters the most. 

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 much lower than 17ms, which is what the ATX spec recommends. This is a budget-oriented platform, so the bulk caps are small, to save money. Still, we would like to see a longer than 10ms hold-up time. 

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.

Typically, the inrush current is much higher with 230V input. Great Wall should use an NTC thermistor with higher resistance to lower it. 

10-110% Load Tests

These tests reveal the CX650'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 #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])Temps (In/Out)PF/AC Volts
13.608A1.992A1.992A0.996A64.97584.250%102422.4 33.86°C0.972
12.023V5.018V3.313V5.021V77.122 37.24°C115.14V
28.253A2.992A2.991A1.198A130.05288.250%110625.1 34.90°C0.987
12.014V5.014V3.309V5.010V147.367 38.85°C115.13V
313.244A3.493A3.492A1.400A195.05989.301%120827.8 35.33°C0.992
12.006V5.012V3.306V5.000V218.429 40.69°C115.13V
418.245A3.993A3.996A1.604A260.07189.400%125829.0 35.71°C0.992
11.996V5.009V3.303V4.990V290.908 42.25°C115.12V
522.908A4.996A5.002A1.808A325.11288.988%135731.2 36.07°C0.993
11.987V5.005V3.300V4.979V365.345 43.08°C115.12V
627.533A6.000A6.007A2.000A389.56488.420%147134.1 36.63°C0.993
11.979V5.002V3.296V4.968V440.582 44.79°C115.12V
732.230A7.003A7.017A2.220A454.93587.620%160936.4 37.20°C0.993
11.971V4.998V3.293V4.956V519.215 46.58°C115.11V
836.936A8.002A8.027A2.428A520.19986.749%175539.2 37.93°C0.994
11.962V4.994V3.289V4.945V599.657 48.27°C115.11V
942.048A8.517A8.521A2.431A585.15785.829%180839.5 38.77°C0.994
11.954V4.991V3.286V4.939V681.772 50.21°C115.10V
1046.900A9.025A9.046A3.052A649.98684.665%181039.6 39.20°C0.995
11.946V4.988V3.283V4.916V767.715 51.25°C115.10V
1152.355A9.030A9.055A3.056A714.80483.560%181339.7 40.71°C0.995
11.939V4.986V3.281V4.910V855.438 53.58°C115.09V
CL10.102A16.005A16.000A0.000A133.93881.807%1532 35.3 36.65°C0.989
12.009V4.996V3.297V5.025V163.725 43.57°C115.13V
CL254.017A1.000A0.999A1.000A658.98185.327%1812 39.6 39.93°C0.995
11.952V5.001V3.294V4.978V772.300 51.77°C115.10V

The PSU can deliver its full load for a prolonged period at high operating temperatures, close to 41 degrees Celsius. The fan has to work over-hours, though,  at such harsh conditions, to cope with the increased thermal load (117W at full load and 141W at the overload test). 

20-80W Load Tests

In the following tests, we measure the CX650'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 #12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])PF/AC Volts

There is no need for high fan speeds at light loads, although the ambient during our tests was over 32 degrees Celsius. The efficiency levels are entirely satisfactory, as well. 

2% or 10W Load Test

Intel plans on raising the ante at efficiency levels under ultra-light loads. So 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
12V5V3.3V5VSBDC/AC (Watts)EfficiencyFan Speed (RPM)PSU Noise (dB[A])PF/AC Volts

It is nice to see over 60% efficiency in a low-cost platform. 


Next, we plotted a chart showing the CX650’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.

For the standards of this category, the CX650 uses a highly efficient platform. Nonetheless, Cooler Master's MWE Bronze units achieve amazing results in the 2% load test, since their designs are tuned for high efficiency under super-light loads. 

5VSB Efficiency

Swipe to scroll horizontally
Test #5VSBDC/AC (Watts)EfficiencyPF/AC Volts

The 5VSB rail's efficiency is among the highest we have ever measured in this category. 

Power Consumption In Idle And Standby

Swipe to scroll horizontally
Mode12V5V3.3V5VSBWattsPF/AC Volts

The energy levels that the PSU needs in standby are low and this helps the 5VSB rail's efficiency, at super-light loads. 

Fan RPM, Delta Temperature, And Output Noise

All results are obtained between an ambient temperature of 32 to 41 degrees Celsius (89.6 to 105.8 degrees Fahrenheit).

(Image credit: Tom's Hardware)

(Image credit: Tom's Hardware)

The fan speed profile at high operating temperatures has a linear increase until 455W load. At higher loads, the fan has to spin at its full speed to cope with the load. 

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 lower ambient temperatures, there is no difference, as you can see in the charts above, in the fan speed profile. Great Wall could apply a more relaxed profile at lower temperatures, but its engineers preferred to stay on the safe side. There is room for improvement here unless they are too worried about the five-year warranty that Corsair offers to this product.

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Contributing Editor

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

  • mdd1963
    Lots of folks 'poo-poo' some of Corsair's PSU offerings, instead flocking to something w/Gold or Platinum in it'/s title, no matter the 150% price increase, and/or the 430W 'only' capacity...

    I've been happily using a Corsair 600 watt PSU (CX600) which cost me all of $55 or so in Feb 2017 if I recall correctly... ; never a stutter.
  • grmaster
    any specific reason why this platform is so bad at advance transient response at 12v