Compact Power: Review of Five Low-Profile PSUs from Seasonic and Enhance

The versatility of compact power supply units is overwhelming: SFX12V (in several different implementations), TFX12V, CFX12V, LFX12V, FlexATX... Today we will discuss the units from two very popular categories: TFX12V units are often used in compact system cases, while FlexATX power supplies are also a popular choice for U1 servers.

by Dmitry Vasiliev
03/31/2013 | 12:12 AM

There are a whole lot of different types of compact power supplies: SFX12V (in multiple versions varying in size and component layout), TFX12V, CFX12V, LFX12V, FlexATX... It would be next to impossible to collect all of them in one review and hardly necessary too since they are not interchangeable, so our today’s tests will be concerned with only two varieties. TFX12V PSUs are a popular choice for compact computers whereas FlexATX PSUs can be found in 1U servers, besides desktop PCs.


It must be noted that the PSUs we are about to test cannot be compared directly. Seasonic’s products are newer and certified for the 80 PLUS Gold standard whereas the Enhance ones are older and only comply with the 80 PLUS Bronze or even just the basic 80 PLUS standard.

Anyway, we don't often have to deal with such form-factors but they are important indeed considering the growing popularity of compact computers. That’s why the difference in class doesn’t prevent us from discussing them all in a single review.

Testing Methodology

The following article offers a detailed description of our testing methodology and equipment and a brief explanation of what the specified and tested parameters of power supplies mean: X-bit Labs Presents: Power Supply Units Testing Methodology. If you feel overwhelmed with the numbers and terms this review abounds in, refer to the Methodology.

You can also go to our Cases/PSU section to check out reviews of all other PSU models we have tested in our labs.

We will mark the actual power consumption of three system configurations (discussed in our article PC Power Consumption: How Many Watts Do We Need?) in the cross-load diagrams. This will help you see if the tested PSU can meet the requirements of a real-life PC.

Testing Particupants

Seasonic SS-300M1U and SS-350M1U

These PSUs are designed for mini 1U servers as is indicated by their model names. However, they are also compatible with the FlexATX standard (namely, Low-profile Power Supply #2).

Recalling compact computer cases we tested, the Cooler Master Elite 100 won't accommodate a PSU of that length (the HDD rack will get in the way): a shorter PSU is needed, even though the mounting holes coincide. Such short PSUs are available too, although are not described in the FlexATX specs. As a matter of fact, Seasonic markets its shorter models (with a length of 150 mm) as FlexATX whereas its 190mm-long PSUs are positioned as ATX12V v2.31/EPS12V.

There are computer cases like the Delux DLC-MS126 which come with 190mm PSUs. So, one of these Seasonic models can be used to replace the Delux’s bundled PSU (which is reported to be very noisy).

These PSUs, like the rest of products covered in this review, came to us without any packaging, so we won’t be able to describe their accessories. Let's get right to the PSUs themselves.

Exterior Design

It’s hard to invent anything extraordinary in terms of exterior design when it comes to this form-factor. The rear end of this PSU may only be different from same-class products in the shape of the punched-out grid over the 40mm fan.

The other end of the case is somewhat more original. The power cables are detachable, which is unusual for this form-factor (we'll discuss the cable system in more detail shortly). There are square vents in the butt end and two rows of oval ones in the top panel of the case.

Circuit Design

The 300 and 350W models are expectedly very much alike in their interior design.

They differ in electrolytic capacitors installed at the output. The junior model has capacitors from United Chemi-Con and Rubycon there.

The higher-wattage model has Rubycon capacitors only (at least where we can read their marking).

The component density is very high, just as you can expect from a compact PSU that is supposed to deliver 300-350 watts of power, so we can't examine the components easily.

Anyway, we can see that these PSUs feature dedicated voltage regulation, the card with small DC-DC converter chokes being located above the output capacitors.

There’s a large daughter card that goes along the side of the case and is connected to the abovementioned voltage regulator card with a cable.

The standby source is based on an Infineon ICE2QR4765 chip which is employed in latest full-size ATX PSUs from Seasonic as well.

The mains connector and filtering circuitry are screened as is typical of Seasonic PSUs.

Cables and Connectors

The Seasonic SS-300M1U and SS-350M1U PSUs are equipped with the same selection of cables and connectors:

The cable system of these PSUs is quite original:

The whole bunch of cables is connected to the PSU with two connectors, as you can see.

The selection of component connectors is sufficient enough for a server PSU. As for desktop applications, the 350W model would benefit from a dedicated power connector for a PCIe graphics card if it were to be used in a gaming computer.



The Seasonic SS-300M1U and SS-350M1U have similar specifications except for the overall wattage and a slight difference in the load capacity of their +3.3V and +5V rails. They can deliver nearly all of their output power via the +12V rail whereas the load capacity of the other rails is rather low (70-80 watts, which is more than enough for modern computers).

These PSUs comply with the 80 PLUS Gold efficiency standard.

UPS Compatibility

Working together with our APC SmartUPS SC 620, the SS-300M1U was stable at its full load of 300 watts when powered by the mains and could switch to the UPS’s batteries at the same load, too.

The SS-350M1U was also stable at its full 350 watts when powered by the mains. It could only switch to the UPS’s batteries at loads up to 315 watts, though.

Cross-Load Voltage Stability

The junior model is quite stable, keeping its +12V and +5V voltages within 2% of the required levels. The +3.3V voltage is no more than 3% off.

The 350W model is even better in this test. Its +12V voltage is almost always within 1% of the required level. The other voltages are comparable to those of the 300W model.

Output Voltage Ripple

The PSUs are close to each other in terms of high-frequency output voltage ripple.

Both PSUs meet the industry standard requirements here.

It’s different at the double mains frequency:

The 300W unit has some voltage ripple on the +12V rail only, but it is not strong.

The higher-wattage unit is close to the permissible limits on the +5V and +12V rails. The voltage ripple is weak on the +3.3V rail.

Temperature and Noise

The PSUs are both cooled by a 40x40x20mm ADDA AD0412XB-C71GP fan. We couldn’t find its specs but the closest model, AD0412XB-C73GP(P), has a rated speed of 10,000 RPM at 0.24 amperes whereas the AD0412XB-C71GP consumes up to 0.3 amperes.

Unfortunately, we couldn’t measure the speed of the fan with our optical tachometer due to the configuration of the vent grid and the small size of the fan itself, so we have to limit ourselves to our subjective impressions.

Well, the fan didn't actually work at all at loads up to 140-150 watts as explained on the nearby sticker. Then, it starts up at a quiet speed, becomes audible at loads about 250 watts, and gets real noisy at 300 watts. The 350W model is definitely noisier at full load than any ATX PSU we've recently tested in our labs.

We wouldn’t consider this as a serious downside, though, because such high loads may only occur in a compact gaming computer with discrete graphics.

Efficiency and Power Factor

The SS-300M1U was 87.6%, 91.9% and 91.5% efficient at reference loads of 20%, 50% and 100%, respectively. The peak efficiency of 92.7% was observed at a load of 141 watts.

As for the SS-350M1U, it was 90.1%, 91.5% and 90.4% efficient at reference loads of 20%, 50% and 100%, respectively. The peak efficiency of 92.2% was observed at a load of 100 watts.

The PSUs meet the 80 PLUS Gold requirements but the higher-wattage model is inferior throughout the entire load range except at low loads (where our measurement accuracy is lower, too).

The power factor is up to 99% with either PSU at high load, just as promised by the manufacturer.

Standby Source

The standby source works blamelessly in each model, so we only show you the senior model's graph.

Seasonic SS-300TGW

This PSU is designed in the TFX12V form-factor (Thin Form Factor with 12V Connector) which is optimized for computer cases 9 to 15 liters large. That’s not the smallest, but quite widespread, type of compact computer enclosures.

Compared to the above-discussed PSUs, this form-factor is larger, allowing to decrease the component density or boost the output power. Besides, the Seasonic SS-300TGW has an 80mm fan which is more efficient and less noisy than the high-speed 40mm buzzers.

Exterior Design

The Seasonic SS-300TGW has a perfectly ordinary appearance for its class. It has no unusual features like detachable cables or additional vent holes.

In this view we can see a vent grid in the PSU case that serves to exhaust the hot air. Like the above-discussed models, this one has no On/Off switch.

Circuit Design

Although this PSU is designed in a rather roomy form-factor, we can see the same platform inside as in the above-discussed Mini 1U products. The only exception is that the cables are not detachable. So, Seasonic has got an efficient platform with power specs suitable for compact computers and uses it in PSUs of different form-factors without much modification.

Thanks to the roomier case, the filtering components near the mains connector are not as close as to each other as in the previous products.

What’s important for our particular purposes, the larger case helped us dismantle the PSU to have a closer look at the compact platform. We just couldn’t do that with the Mini 1U products because we couldn’t reach some mounting screws.


And now we can check out the controller’s chip. It is the half-bridge resonant LLC converter Infineon ICE2HS01G. The 3PCS01 PFC-controller you can see nearby is manufactured by Infineon, too.

Coupled with the Infineon ICE2QR4765 standby controller (the same as we saw in the SS-300M1U and SS-350M1U), we have the same set of controllers as in Seasonic's Gold-certified G series of ATX PSUs.

Like the junior model in the above-discussed pair, the Seasonic SS-300TGW has Rubycon and United Chemi-Con capacitors at the output.

But there’s also a single Teapo capacitor next to the standby source chip.

Cables and Connectors

The Seasonic SS-300TGW is equipped with the following cables and connectors:

Oddly enough, this larger PSU has fewer cables and connectors than its Mini 1U counterpart that has the same wattage rating. To be exact, the SS-300TGW lacks one PATA and one SATA power connector which are present in the SS-300M1U.

Considering that there are compact computer cases that can accommodate more than three drives (including an optical drive), we can’t appreciate this reduction in the number of available power connectors.


The Seasonic SS-300TGW has the same specs as the SS-300M1U, which is no surprise since both have the same platform and wattage.

It complies with the 80 PLUS Gold standard, too.

UPS Compatibility

Working together with the APC SmartUPS SC 620, this PSU was stable at loads up to 300 watts when powered by the mains but could switch to the UPS’s batteries at loads no higher than 285 watts.

Cross-Load Voltage Stability

The Seasonic SS-300TGW is less successful in this test than the previous models that share the same platform, yet each of its voltages remains within 3% of the required level anyway.

Output Voltage Ripple

The output voltage ripple is almost the same as with the SS-300M1U. It is only more or less strong on the +12V rail and always remains far within the permissible limits.

Temperature and Noise

The Seasonic SS-300TGW is cooled by an 80x80x15mm ADDA AD0812MB-D90 fan which has a rated speed of 3500 RPM.

As opposed to the previous PSUs, this model didn’t prevent us from measuring the speed of its fan.

The fan was actually idle until a load of 120 watts. After that, it would turn on for brief periods of time which eventually got longer and longer as the PSU load grew. The fan worked constantly at 50% and higher loads. While working constantly, the fan steadily accelerated from 650 RPM to 1600 RPM. A 120x120x25mm fan would be uncomfortably loud at such a high speed, but the low-profile 80mm fan was barely audible.

The Seasonic SS-300TGW is very quiet throughout the entire load range, being preferable to the same-wattage SS-300M1U whose fan is downright loud at full load.

Efficiency and Power Factor

The Seasonic SS-300TGW is 88.1%, 91.9% and 91.6% efficient at the reference loads of 20%, 50% and 100%. Thus, it meets the 80 PLUS Gold requirements. The peak efficiency of 92.3% was observed at a load of 101 watts.

The power factor was 99.4% at full load.

Standby Source

The standby source copes with its job without a single problem.

Enhance FLEX-0130B

As indicated by its model name, the Enhance FLEX-0130B is designed in the FlexATX form-factor. This product is 150 rather than 190.5 mm long but otherwise meets the FlexATX requirements perfectly.

The photo shows this PSU next to a Seasonic M1U. You can see they are identical in height and width but the Enhance FLEX-0130B is 4 cm shorter.

Exterior Design

There are three rows of oval vents in the top panel whereas the Seasonic M1U units are longer but only have two rows of vents there.

There’s nothing extraordinary at the back: a mains connector and a 40mm fan behind an intricately shaped punched-out grid.

Circuit Design

We’ve noted the high component density of the Seasonic M1U units above, but the Enhance FLEX-0130B is an even more densely packed PSU.

It’s even hard to make out basic features such as whether the PSU has dedicated voltage regulation or not.

With so many chokes all around the PSU, it’s hard to tell which are responsible for voltage regulation and which for A-PFC, for example.

There are three chokes in the photo above (one is sleeved and oriented horizontally) in the output circuitry area but we can’t be sure if all of them are used to regulate voltages or the third choke belongs to some other circuit.

Getting a little ahead of our review, we can tell you that the cross-load tests are indicative of joint regulation of the +5V and +12V voltages.

The mains connector is screened in a simpler way than in the Seasonic PSUs. There is no copper sheet covering it.

There are Su’scon capacitors at the output. Don't be confused by the coloring which makes them similar to United Chemi-Con components.

Cables and Connectors

The Enhance FLEX-0130B is equipped with the following cables and connectors:

The selection of cables isn’t good for a modern PSU since there is only one SATA power connector here. You won’t be able to power a configuration with one HDD and one optical drive without adapters. The cables are long enough for compact computer cases, though.


The specifications aren’t impressive. The Enhance FLEX-0130B can only yield 250 out of its full 300 watts via the most important +12V rail. The relatively high load capacity of the other rails is good but hardly really necessary for modern PCs.

The efficiency isn’t high, either. The basic 80 PLUS certification is not even a mainstream feature anymore, at least for full-size ATX products.

UPS Compatibility

Working together with our APC SmartUPS SC 620, this PSU was stable when powered by the mains up to its full load of 300 watts. It could switch to the UPS's batteries at loads up to 255 watts.

By the way, since we're testing low-wattage PSUs today, we check out their UPS compatibility at loads lower than those we usually use for full-size ATX PSUs, i.e. down to 280 watts.

Cross-Load Voltage Stability

The diagram is indicative of joint voltage regulation, but the PSU is good enough in the typical load range: the single reference PC configuration that meets the PSU’s wattage is in the green zone.

It is only at unrealistically misbalanced load combinations (high load on the +3.3V and +5V rails and low load on the +12V rail) that the voltages may go out of the permissible limits.

The results are very good for a PSU without dedicated voltage regulation. It is in the typical load range that the voltages are the most stable.

Output Voltage Ripple

The high-frequency ripple is noticeable on every power rail, especially on the +5V and +12V rails, but always stays within the permissible limits.

We can see a similar picture at the double mains frequency.

Temperature and Noise

The PSU is cooled by a 40x40x20mm ADDA AD0412XB-C51 fan. As opposed to the ADDA fans in Seasonic's M1U products, it has 5 rather than 7 blades and a rated speed of 8500 RPM.

Like with Seasonic’s Mini 1U series, the configuration of the fan grid and the small size of the fan prevented us from measuring the speed. Subjectively, the Enhance FLEX-0130B is noisier than the above-discussed Seasonic PSUs, becoming audible at a load of 100 watts, uncomfortable at 150 watts and downright loud at 250 watts and higher. So, this model can hardly be recommended for people who prefer silent computers.

Efficiency and Power Factor

The Enhance FLEX-0130B is 80.5%, 83.6% and 82.7% efficient at loads of 20%, 50%, and 100%. That's enough for the basic 80 PLUS requirements but falls short of the 80 PLUS Bronze standard. The peak efficiency of 84.8% was observed at a load of 230 watts.

The power factor was almost as high as 99% at full load.

Standby Source

There’s nothing wrong with the standby source of this PSU.

Enhance ENP-7025E

At 250 watts, this PSU has the lowest wattage rating in this review since the others are rated for 300 to 350 watts. That’s enough for compact PCs, however, as many of them come bundled with 200W or lower PSUs.

The form-factor is TFX12V, just like Seasonic’s SS-300TGW.

Exterior Design

Compact form-factors leave but little room for designer’s imagination, so the exterior is similar to Seasonic’s SS-300TGW. We can only note additional vent holes in the panel with cables and a different design of the top panel (it is a single whole with the sides of the case).

There are even fewer differences at the back. The vent grid is just smaller compared to the Seasonic SS-300TGW.

Circuit Design

The main PCB is shorter than the case, so we can suspect the same hardware platform as in the shortened FlexATX PSU.

However, the interior design is much different from the above-discussed FLEX-0130B. The component density isn’t high and we can easily examine this model.

Particularly, we can see that the Enhance ENP-7025E lacks dedicated voltage regulation. We’ve noted this with the previous Enhance, too.

The mains connector is screened in the same way as in the lower-wattage unit from Enhance, but the connector itself is farther away from the main PCB due to the different component layout. Hopefully, this will have a positive effect on voltage ripple.

The standby source is based on an STR-A6069 chip (the end of its marking is covered with protective glue).

The PWM & PFC controller is based on a Champion Micro CM6806AC chip that resides on a dedicated upright daughter card.

The chip is unusually small compared to other controllers such as the widespread CM6800.

The PSU has electrolytic capacitors from Teapo and Su’scon at its output.

Cables and Connectors

The Enhance ENP-7025E is equipped with the following cables and connectors:

Compared to the higher-wattage Enhance, there is a second SATA instead of one PATA power connector. Thus, the Enhance ENP-7025E allows building a generic configuration with one optical and one hard drive without adapters (if the drives are not far apart from each other as both SATA plugs reside on the same cable).


Like the previous PSU from Enhance, the Enhance ENP-7025E doesn’t detail its electrical specs but, considering that the combined load capacity of the two +12V lines is higher than the PSU’s total output power, we can suspect that it can deliver all of its power via the +12V rail.

Thus, the actual difference between this model and the FLEX-0130B isn’t large since the combined load on the +3.3V and +5V rails can hardly be higher than 40 watts in a real compact PC.

Being able to deliver all of its output power via the +12V rail and limiting the load capacity of the other rails to 80 watts, the Enhance ENP-7025E looks more up-to-date than the FLEX-0130B.

It is certified for the 80 PLUS Bronze standard.

UPS Compatibility

Working together with our APC SmartUPS SC 620, the Enhance ENP-7025E was stable at loads up to 250 watts when powered by the mains but could only switch to the UPS's batteries at loads no higher than 235 watts.

Cross-Load Voltage Stability

It’s similar to the FLEX-0130B model. The +3.3V rail is very stable whereas the jointly regulated +5V and +12V voltages are the closest to the required levels right in the typical load range.

It is only at misbalanced load combinations that the voltages go out of the required ranges, but you can hardly encounter such situations in real-life applications.

Output Voltage Ripple

The output voltage ripple isn’t strong overall, especially on the +12V rail. It is far within the permissible limits on every power rail.

The same goes for the low-frequency voltage ripple.

The Enhance ENP-7025E is actually the best among the five tested PSUs in terms of its output voltage ripple.

Temperature and Noise

Like the other PSUs in this review, the Enhance ENP-7025E is cooled by a fan from ADDA. It is the 80x80x20mm AD0812HB-C70 model with 7 blades and a rated speed of 3010 RPM.

The fan starts out at 1140 RPM and maintains this speed until a load of 100 watts. Then it accelerates smoothly, reaching 2340 RPM at full load. The 80mm fan is quite audible at such a speed, but not particularly irritating.

Take note that the speed of the fan is just enough to keep the temperature at the same level. It is only at near-maximum loads that the temperature grows up a little.

The Enhance ENP-7025E is superior to every model with 40mm fan in terms of acoustic comfort, but noisier than the Seasonic SS-300TGW which has a similar form-factor.

Efficiency and Power Factor

The Enhance ENP-7025E is 83.1%, 86.1% and 84.1% efficient at the reference loads of 20%, 50% and 100%, complying with the 80 PLUS Bronze standard. The peak efficiency of 88.4% was observed at a load of 91 watts.

The power factor is but slightly higher than 98% at high loads, which is worse than average. This parameter isn’t crucial for home PCs, though.

Standby Source

The standby source is blameless.


First of all, we must admit that PSUs with 40mm cooling fans are not an attractive choice for home users even though there are quite a lot of compact cases for desktop PCs with such PSUs.

Seasonic's Gold-certified FlexATX/Mini 1U products leave a good impressive. They are silent at low loads, comfortable enough at medium ones, but become too loud at high loads. Well, if the computer is used for watching video, web surfing or office applications, such PSUs are going to be cooled passively and remain silent all the time. They can only get uncomfortably noisy in a compact gaming system with a rather advanced discrete graphics card.

Having the same form-factor, the Enhance FLEX-0130B is downright unsuitable for home use. It gets too noisy too soon. As for server applications, its efficiency doesn’t look attractive. The lack of acoustic comfort and low efficiency are not compensated by its price, by the way. The Seasonic SS-300M1U costs about the same money but offers much better parameters.

TFX12V PSUs with an 80mm cooling fan are generally better in terms of noisiness. The Enhance, the noisier of the two TFX12V products in this review, is much quieter at loads above 200 watts than the three PSUs with 40mm cooling fans.

As opposed to the Enhance FLEX-0130B, the Enhance ENP-7025E is rather quiet at medium loads and not uncomfortable at high ones. Its electrical parameters and price are good, too.

But it is the Seasonic SS-300TGW that is the best choice for building a compact home computer. Silent at medium and quiet at high loads, it boasts excellent efficiency and high output power (by the standards of compact PSUs). It is slightly more expensive than the Enhance ENP-7025E but is absolutely worth it.