Fractal Design Edison M Series 750W Power Supply Review

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Transient Response Tests

Advanced Transient Response Tests

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

In these tests, we monitor the response of the PSU in two different scenarios. First, a transient load (10A at +12V, 5A at 5V, 5A at 3.3V and 0.5A at 5VSB) is applied to the PSU for 200ms while it works at 20-percent load. In the second scenario, the PSU is hit by the same transient load while operating at 50-percent load. In both tests, we use our oscilloscope to measure the voltage drops caused by the transient load. The voltages should remain within the ATX specification's regulation limits.

These tests are crucial because they simulate the transient loads a PSU is likely to handle (such as booting a RAID array or an instant 100-percent load of CPU/GPUs). We call these tests "Advanced Transient Response Tests," and they are designed to be tough to master.   

Advanced Transient Response at 20 Percent

VoltageBeforeAfterChangePass/Fail
12V 12.232V12.122V0.90%Pass
5V5.089V5.012V1.51%Pass
3.3V3.353V3.194V4.74%Pass
5VSB5.004V4.978V0.52%Pass

Advanced Transient Response at 50 Percent

VoltageBeforeAfterChangePass/Fail
12V 12.172V12.061V0.91%Pass
5V5.071V4.990V1.60%Pass
3.3V3.322V3.170V4.58%Pass
5VSB4.970V4.929V0.82%Pass
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The 5V and 5VSB rails do pretty well in our tests, but we would have liked to see lower deviations at +12V, which managed to stay within one percent in both tests. Things didn’t go well for the 3.3V rail, though. It exceeded 4.5 percent deviation on both tests and took last place in the corresponding comparison chart.

Below are the oscilloscope screenshots we took during Advanced Transient Response Testing.

Transient Response At 20-Percent Load

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Transient Response At 50-Percent Load

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Turn-On Transient Tests

In the next set of tests, we measure the response of the PSU in simpler scenarios of transient load: during the power-on phase of the PSU.

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For the first measurement, we turn off the PSU, dial in the maximum current the 5VSB can output and then switch on the PSU. In the second test, we dial the maximum load +12V can handle and start the PSU while it's in standby mode. In the last test, while the PSU is completely switched off (we cut off the power or switch the PSU off by flipping its on/off switch), we dial the maximum load the +12V rail can handle before switching the PSU on from the loader and restoring the power. The ATX specifications state that recorded spikes on all rails should not exceed 10 percent of their nominal values (+10 percent for 12V is 13.2V, and 5.5V for 5V).

Aris Mpitziopoulos
Aris Mpitziopoulos

Aris Mpitziopoulos is a Contributing Editor at Tom's Hardware US, covering PSUs.
12 Comments Comment from the forums
  • maxwellmelon
    there are several issues with there testing. first power good signal is not a good base for testing as its simple to "Cheat" the 16ms hold up.how about actually watching power good vs output voltages also. also the thermal camera scall changes every time how about using a fix scale as modifying scales leads to making things show hot that are not really that hot.
    Reply
  • Aris_Mp
    First of all I measure AC loss to PWR_OK hold-up time since it is much easier to show it in my graphs and explain it. For me it is as easy to measure "AC loss to PWR_OK hold-up time" plus "PWR_OK inactive to DC loss delay" but I prefer it the way I do it.

    Also where do you base this? That the PG signal is simple to cheat and the manufacturers actually do this? From the moment the mainboards take seriously into account PG if this was the case then most likely there would be huge problems with lots of them. According to the ATX spec PG is de-asserted to a low state when any of the main rails falls out of 5% v. reg. Simply as that.

    It just gives room for 1 ms till the PG signal sees the change at least in the ATX spec.

    As for the thermal camera how it can show things hotter than it is? The scale is for this reason and from the moment the camera sees something from a different angle and a different region the scale is changing automatically. Nothing I can do about it. This is why I provide also actual temperature readings on all IR images.


    Reply
  • PaulBags
    A quick opinion on the edison vs similar range seasonic own brand would be nice. Is it a new design, or an exact rebrand of a seasonic design? Quality of components vs?
    Reply
  • Aris_Mp
    This is based on the same platform with the Seasonic G series and I state this in the "look inside" page. I haven't tested the G750 so far but I believe that since they are based on the same platform performance will be similar. Seasonic might used Enesol polymer caps (something that they usually do in their G units) instead of Chemi-Cons that Fractal chose, but both cap brands are very good so don't expect to see any real performance difference on them (although I prefer Chemi-Cons).

    So the design is nothing new and this is a Seasonic rebrand with minor differences at the internals (most likely the caps selection as I stated above).
    Reply
  • Aris_Mp
    Forgot to mention that besides caps the cooling fan is also different since on all Seasonic G units that I have tested so far have an ADDA double-ball bearing fan while the Edison PSU uses an FDB fan. However lately I noticed that many Seasonic units use Hong Hua FDB fans instead of ADDA double-ball bearing ones, so it is possible that this change might have affected the new bunches of G units.
    Reply
  • redgarl
    The Newton Series is much better.
    Reply
  • Sakkura
    You say that you'd prefer if the unit was fully modular, but I don't really see the point.

    The fixed cables are the ones that will always be in use for any system using a 750W power supply, so the ability to disconnect those cables would not be beneficial. In fact it would lead to higher cost and also an extra point of failure and a slight loss of efficiency since a connector can never quite match an uninterrupted cable.
    Reply
  • Aris_Mp
    fully modular cables provide easier installation and cable management. Also you can easily change them with longer/shorter ones if you like or replace them in case there is a problem with them or simply you want something fancier.

    Loss of efficiency isn't a reason any more, on the contrary with bus bars or thick cables transferring power to the modular PCB energy losses can be minimized. In addition no cables block the secondary side caps, something that besides increasing their lifetime also allows for more relaxed fan profiles and better airflow inside the chassis.

    Also the cost of a semi-modular to fully modular isn't high and in a 750 W PSU that costs 140 bucks already the cost reason doesn't stand (for fully modular design).
    Reply
  • Sakkura
    15924995 said:
    fully modular cables provide easier installation and cable management. Also you can easily change them with longer/shorter ones if you like or replace them in case there is a problem with them or simply you want something fancier.
    No they don't. The connector on the power supply end adds complexity and reduces cable flexibility.

    You cannot easily change them because other cables are often incompatible - there is no common standard for modular PSU cables. Using incompatible cables can be downright dangerous. Here is a cautionary tale.
    Reply
  • Aris_Mp
    I didn't say that you can change them with anything, did I? Also it is common sense that every manufacturer uses their one design on modular cables. Thing is that with modular PSUs you can get an extra cable kit since most manufacturers sell one for their PSUs (e.g. Corsair, EVGA).

    Also I still cannot understand how the connector on the PSU end adds complexity and reduces cable flexibility! Cable flexibility depends on the gauges' thickness and not on the cables modularity design (or not).

    Anyway I believe I made my opinion clear on why I prefer fully-modular PSUs.
    Reply