The Silverstone ST30SF ST45SF SFX Power Supply Review

With the vast selection of advanced ATX PSUs available today, PC users can easily pick one that perfectly suits their budget and needs. When shopping for an SFX PSU however, the options are very limited, as very few companies do market advanced high quality SFX PSUs. Even when the company has a few SFX units available, most of the time these are expensive top-tier models, leaving budget-driven users bewildered.

One of the companies that invests a lot on small form factor systems is SilverStone. The company currently markets dozens of proprietary PC cases, many of which require SFX PSUs. SilverStone is also marketing some of the most advanced SFX PSUs available, such as the 700W SX700-LPT that we reviewed a few months ago and their newly released 800W SX800-LTI with 80Plus Titanium compliance. Outrageously powerful (and expensive) SFX PSUs are not useful to users that want to build simple, compact media or office PCs. Their “SFX extended” form factors make them incompatible with very compact case designs anyway, including many of SilverStone’s own products.

Today we are having a look at the two SFX units that SilverStone is offering for budget-conscious builders, the ST30SF and the ST45SF. Although they are not as grand as the top-tier PSUs we mentioned before, they do have a high power output of 300W and 450W respectively, sufficient for typical media and gaming PCs. They only have an 80Plus Bronze efficiency certification, but what they lack in technology they make up for in price. We should clarify that the units in this review are the latest version, V2.0 for the ST30SF and the V3.0 for the ST45SF, that have been reengineered for improved performance in home and gaming PCs. Most of the differences over their previous versions will be highlighted in the following pages, but the first difference that we should point out is that the new units are rated at 40°C ambient temperature, whereas the previous versions were rated at 50°C.

SilverStone ST30SF Power specifications ( Rated @ 40 °C )
AC INPUT 100 – 240 VAC, 50 – 60 Hz
RAIL +3.3V +5V +12V +5Vsb -12V
MAX OUTPUT 16A 16A 25A 3A 0.3A
90W 300W 15W 3.6W
TOTAL 300W

SilverStone ST45SF Power specifications ( Rated @ 40 °C )
AC INPUT 100 – 240 VAC, 50 – 60 Hz
RAIL +3.3V +5V +12V +5Vsb -12V
MAX OUTPUT 20A 20A 37.5A 3A 0.3A
110W 450W 15W 3.6W
TOTAL 450W

 

Packaging & Bundle

SilverStone supplies their cost-effective SFX PSUs in aesthetically simple, practical cardboard boxes. The artwork on the black boxes is minimal, but SilverStone had every worthwhile bit of information printed on them and they should provide ample shipping protection to the lightweight units.

We expected to find only the absolute minimum of items bundled alongside such units but SilverStone had us surprised. Except from the thorough manual, black mounting screws and the necessary AC cable, the company also supplies an ATX to SFX adapter frame, allowing these SFX units to be installed into ATX compatible cases. This greatly enhances the value of the units, ensuring that they may fit into other cases into the future, as well as their potential market group, as they may be appealing to modders and other people that wish to save some space in their PSU compartment for some reason.

Connector type SilverStone ST30SF SilverStone ST45SF
ATX 24 Pin 1 1
EPS 4+4 Pin 1 1
EPS 8 Pin
PCI-E 6+2 Pin 1
PCI-E 6 Pin 1 1
SATA 3 3
Molex 2 2
Floppy 1 1

External Appearance

The ST30SF and the ST45SF are externally identical, with the only apparent physical difference being the sticker on the side of their chassis. Even when it comes to the cables and connectors, the ST45SF only has one extra 8/6-pin PCIE connector, hinting that SilverStone expects the ST45SF only to be used if the PSU has to power a modern gaming graphics card. The designer’s logic is sound, as the number of drives that can be installed inside a compact chassis that has been designed for SFX PSUs usually is very limited, leaving no other device to require substantial levels of power other than a powerful GPU.

 

The ST30SF and the ST45SF feature a simple steel chassis that has been sprayed with a typical matte black paint. It is a very smooth paint job but the paint is highly prone to fingermarks. SilverStone placed the sticker with the electrical specifications on the left side of the chassis and small stickers with the unit’s serial number, version, etc., on the right side of the chassis. You can easily tell if the units are the latest or an older version by just looking at their fans: the newer ST30SF V2.0 and the ST45SF V3.0 models have 92 mm fans that barely fit into the body of the PSU, the older versions were using smaller 80 mm fans.

The company logo is once again engraved at the top of the unit, a technique that SilverStone performs on most of their PSU products to date. Despite the very small size of the chassis, the designer managed to find room for a small on/off switch next to the AC cable receptacle. The front of the PSU is plain, with just a hole for the hardwired cables to come out from. The cable arrangement is typical for the price range of these units, with color-coded wires covered in black nylon sleeving.

Internal Design

Whereas the ST30SF and the ST45SF externally are practically twins, there are significant differences on the inside of the units, which was to be expected considering that the ST45SF has 50% greater power output over the ST30SF. The first slight difference is their fan. Both of the simple black 92 mm low profile fans are supplied by Globe and are of the same series, but they are different models, with the ST30SF having a S0921512M and the ST45SF having a S0921512H installed. These fans have a “DURO” bearing engine, which is an enhanced version of a sleeve bearing that has been engineered for longevity. Their difference is that they have different speed ratings, with the former having a maximum speed of 2500 RPM and the latter of 3000 RPM.

A quick look on the inside reveals that both units share the same OEM and are based on the same platform, however there are great differences on the sizing of their components. Regardless of the electronic component sizes, it is worthwhile to mention that the main heatsinks remain identical, hinting that the extra cooling required to dissipate the higher energy losses of the ST45SF will be coming from its more powerful cooling fan. High Power is the OEM behind these two PSUs, a company mostly reputable for their balanced performance-to-cost designs.

The core design of the ST30SF/ST45SF is relatively simple technologically, with the designer obviously striving to deliver reliable, high quality power without caring about maximizing the product’s efficiency. Both units share the same components up to the input conversion bridge, with a filtering stage consisting of four Y capacitors, two X capacitors and two filtering inductors. The only difference here virtually is that the input conversion bridge of the 450W version has its own heatsink whereas the bridge in the 300W version has no heatsink at all.

 

SilverStone ST30SF Internal View

From here on, the design of both units remains the same but the size of the electronic components, both active and passive ones, differs greatly. The most apparent difference is the primary APFC capacitor, with a 180μF/400V capacitor in the ST30SF and a nearly a twice as large 330μF/400V capacitor in the ST45SF. Both are supplied by Japanese companies, Nichicon and Nippon Chemi-Con respectively. The smaller electrolytic capacitors in both units are supplied either by Nippon Chemi-Con or by Teapo, which is a good quality selection of products for cost-efficient PSUs.

 

SilverStone ST45SF Internal View

Two transistors on the primary side of the transformer form an asymmetric half-bridge inversion stage and four transistors on the secondary side form the synchronous rectifier for the 12V output. The 3.3V and 5V outputs are generated by DC-to-DC circuits found on the small vertical PCB. Despite the presence of the DC-to-DC conversion circuits and the synchronous rectifier, these units only reached up to an 80Plus Bronze certification, hinting that we might be dealing with high internal temperatures at higher outputs. 

Cold Test Results

For the testing of PSUs, we are using high precision electronic loads with a maximum power draw of 2700 Watts, a Rigol DS5042M 40 MHz oscilloscope, an Extech 380803 power analyzer, two high precision UNI-T UT-325 digital thermometers, an Extech HD600 SPL meter, a self-designed hotbox and various other bits and parts. For a thorough explanation of our testing methodology and more details on our equipment, please refer to our How We Test PSUs – 2014 Pipeline post.

Efficiency
SilverStone ST30SFSilverStone ST45SF

Despite having only an 80Plus Bronze efficiency certification and that we were testing them with a room temperature lower than the standard 25 °C that the testing guidelines dictate, both units failed to achieve even that level of efficiency with a 230VAC input. The maximum efficiency of both units at 50% load is just shy of the 88% figure that they had to reach in order to comply with the certification standards. The platform received its certification rating with an input of 110VAC though, where the efficiency standard dictates a minimum of 85% efficiency at 50% load, not 88%. Even though all switching PSUs are less efficient with an input of 110VAC, it is very much likely that the platform does meet the qualification ratings, even if only barely. Regardless, both the ST30SF and the ST45SF display relatively stable energy conversion efficiency, with an average of 86.1% and 86.3% respectively (within their nominal operational range – 20% to 100% of the unit's capacity). The efficiency plummets at lower loads, diving all the way down to almost 70% at just 5% load.

Power Losses
SilverStone ST30SFSilverStone ST45SF

These two PSUs are an excellent opportunity to showcase how picking an oversized PSU can lead to inferior overall performance. With both units based on the same platform but with a severely different power range, the ST45SF is at a great disadvantage with loads lower than 80-90 Watts, whereas the ST30SF come within its nominal loading range with a load of just 60 Watts. What this means is that the ST30SF is significantly more efficient than the ST45SF with a load of about 80-90 Watts or below. By looking at the graphs, we can see that the ST45SF generates significantly greater losses at very low loads due to inefficient operation, making it hotter and louder than its much less powerful sibling. This is an excellent example of how an unnecessarily oversized PSU can be actually detrimental. 

Intake & Exhaust Air Temperature
SilverStone ST30SFSilverStone ST45SF

 

Heatsink Temperature
SilverStone ST30SFSilverStone ST45SF

From the sound pressure level graphs, we can see that both units reach about the same maximum noise output when operating in room temperature, although the 450W model does so with an output that is 50% greater than the 300W model. The operating temperatures of the ST45SF are however a little higher, hinting a slightly laxer cooling profile.

Sound Pressure Level
SilverStone ST30SFSilverStone ST45SF

 

 

Hot Test Results

As we can see from their performance tables, the ST30SF and the ST45SF both display very good power quality figures for PSUs of their class. The filtering figures of the ST30SF are better, with a maximum ripple of about 42 mV on the 12V line under maximum load. The ST45SF reached up to 64 mV on the 12V line under maximum load, but that was to be expected given its much higher output. If we were to compare the two units on a per-watt basis, the ST45SF does deliver better power quality figures, which is to be expected considering its more capable electronic components. The voltage regulation of both units is almost identical, with an average of about 1.7% on the 3.3V/5V lines and 1.9% on the 12V line.

SilverStone ST30SF Main Output
Load (Watts) 60.95 W 151.64 W 226.57 W 299.92 W
Load (Percent) 20.32% 50.55% 75.52% 99.97%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.31 3.37 3.28 3.35 4.91 3.33 6.55 3.32
5 V 1.31 5.1 3.28 5.08 4.91 5.05 6.55 5.03
12 V 4.09 12.19 10.23 12.12 15.35 12.08 20.47 11.98

 

Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
12V
CL2
3.3V + 5V
3.3V 1.6% 12 10 10 12 10 12
5V 1.5% 8 12 12 16 10 12
12V 1.8% 14 24 28 42 38 20

Even though SilverStone rates the new revision models at 40 °C, they had no problem reaching their maximum power output inside our hotbox. Unexpectedly, their energy conversion efficiency dropped only very slightly as well, with the average nominal load (20-100%) efficiency dropping down to 85.6% and 85.8% for the ST30SF and the ST45SF respectively. We would expect the impact to be much higher considering their design and the very high temperatures, but both units proved us wrong. 

SilverStone ST45SF Main Output
Load (Watts) 91.65 W 228.35 W 338.28 W 449.76 W
Load (Percent) 20.37% 50.74% 75.17% 99.95%
  Amperes Volts Amperes Volts Amperes Volts Amperes Volts
3.3 V 1.69 3.38 4.22 3.37 6.33 3.32 8.44 3.31
5 V 1.69 5.12 4.22 5.09 6.33 5.06 8.44 5.03
12 V 6.33 12.21 15.83 12.17 23.75 12.01 31.66 11.99

 

Line Regulation
(20% to 100% load)
Voltage Ripple (mV)
20% Load 50% Load 75% Load 100% Load CL1
12V
CL2
3.3V + 5V
3.3V 1.65% 16 16 18 18 16 16
5V 1.7% 18 20 20 22 24 20
12V 1.9% 18 26 36 64 68 40

Efficiency
SilverStone ST30SFSilverStone ST45SF

Power Losses
SilverStone ST30SFSilverStone ST45SF

The low impact of the high temperature on the efficiency of the units hints that the active components of both units are significantly oversized for their design and power rating and could, in theory, sustain their power output with an ambient temperature of 50 °C. The operating temperatures however are very high, with the ST30SF reaching temperatures of nearly 92 °C under maximum load and the ST45SF a few degrees higher than that. 

Intake & Exhaust Air Temperature
SilverStone ST30SFSilverStone ST45SF

Heatsink Temperature
SilverStone ST30SFSilverStone ST45SF

Under such operating conditions we can see that the fans of both units shoot up to their maximum speed before the units even reach 50% of their rated maximum power output. The ST45SF reached a maximum sound pressure level of about 56 dB(A), higher than the 52 dB(A) of the ST30SF, due to its more powerful fan. The more powerful fan proved to be more than a necessity, as the ST45SF can barely maintain nominal operating temperatures when heavily loaded. 

Sound Pressure Level
SilverStone ST30SFSilverStone ST45SF

Conclusion

From our review of the ST30SF and the ST45SF, it is apparent that SilverStone designed these units with a very specific purpose – to market reliable SFX PSUs with good power quality at the lowest possible cost. Above all else we have to consider that we are talking about $45 (ST30SF) to $55 (ST45SF) products (after rebate) and we would find it difficult to even recommend ATX PSUs inside this price range. Finding similarly priced SFX PSUs can be a tremendous challenge, meaning that SilverStone has very little competition to worry about in this segment of the market.

We believe that, considering the design requirements and price range of the ST30SF and the ST45SF, the designer did an excellent job. Both of the units are of excellent quality, with a clean design and proven components. The power output quality is very good, with strong regulation and low noise even under very high operating temperatures. Only the energy conversion efficiency is mediocre, with both units barely suggesting that they can justify their already low 80Plus Bronze certification with an input of 110VAC, and marginally failing it with an input of 230VAC.

The compact size of the SFX units paired with the mediocre efficiency result to the undesirable situation of having high thermal losses inside a device with limited cooling capacity, i.e. to poor thermal performance. An ATX unit would have no problem dissipating these thermal losses even without larger heatsinks, by only making use of the sheer airflow that a full size 120 mm fan can provide. This is not an option with SFX units, where the space for both the heatsinks and the fan is very limited. Even the low profile 92 mm fans found in the ST30SF and the ST45SF are considered to be very large for such designs. In summary, the ST30SF and the ST45SF will be reasonably quiet while the system is idling but not when heavily loaded: if you are planning to power a powerful GPU with the ST45SF, it is very likely that it will be louder than the card itself.

Buy SilverStone ST30SF on Amazon.com

Buy SilverStone ST45SF on Amazon.com

In summary, the SilverStone ST30SF and the ST45SF are competitively priced SFX units, designed to offer a low-cost and yet high quality option to users that want to build low-power systems or simply do not care much about acoustics. Even though they can get significantly loud if heavily loaded, their quality and power output are excellent. With their very low retail prices, SilverStone practically has no competition, with the ST30SF and the ST45SF being virtually the only widely available choice for a high quality, low cost SFX PSU. 

SOURCE:http://www.anandtech.com/show/11070/the-silverstone-st30sf-st45sf-sfx-psu-review

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