Seasonic Focus SGX 650W SFX-L PSU Review: Reliable Power, Tiny Form Factor

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Protection Features, DC Power Sequencing, Cross-Load Tests and Infrared Images

Protection Features

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

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Protection Features
OCP12V: 67.4A (124.81%), 11.924V 5V: 27.9A (139.5%), 5.003V 3.3V: 26.2A (131%), 3.318V 5VSB: 6.4A (213.33%), 5.018V
OPP824.5W (126.85%)
OTP✓ (172°C @ 12V Heat Sink)
SCP12V: ✓ 5V: ✓ 3.3V: ✓ 5VSB: ✓ -12V: ✓
PWR_OKProper Operation
SIPSurge: MOV Inrush: NTC Thermistor & Bypass Relay

The OCP triggering points at +12V and 3.3V rails are properly set. At 5V, the OCP's threshold is higher than required, while at 5VSB, it is just crazy high. Nonetheless, we didn't notice any large voltage drops or excess ripple. All the rest protection features are present and work well.

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.

The PSU passes these tests with success, since the 3.3V rail is always lower than the rest 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°C (86°F) and 32°C (89.6°F).

Load Regulation Charts

Efficiency Chart

The Seasonic Focus SGX 650W has its best efficiency with loads, ranging from 150W to around 380W load at +12V, with the load on the minor rails staying below 65W.

Ripple Charts

The lower the power supply's ripple the more stable the system will be and less stress will be also 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 FLIR E4 camera able to deliver an IR resolution of 320x240 (76,800 pixels).

The temperatures at the internals stay at low enough levels, even in the DC-DC converters which usually are the hottest parts inside a power supply, under increased loads on the minor rails.

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Contributing Editor

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