SilverStone ST45SF-G Power Supply Review

[nextpage title=”Introduction”]

SilverStone offers two SFX12V power supplies, the ST45SF, which comes with the 80 Plus Bronze certification, and the ST45SF-G, which comes with the 80 Plus Gold certification. Both are rated at 450 W. Let’s see if the ST45SF-G is a good pick.

Figure 1: SilverStone ST45SF-G power supply

Figure 2: SilverStone ST45SF-G power supply

The SilverStone ST45SF-G is only 3.9” (100 mm) deep, using a slim 80 mm ball-bearing fan on its bottom (Young Lin Tech DFB801512H).

Figure 3: Fan

The cabling system is fully modular, meaning that even the main motherboard cable is detachable. This system has five connectors: one for the main motherboard cable, one for the ATX12V/EPS12V cable, one for the video card cable (blue connector), and two for SATA and peripheral cables. This power supply comes with the following cables:

• Main motherboard cable with a 20/24-pin connector, 12.6” (32 cm) long
• One cable with two ATX12V connectors that together form an EPS12V connector, 16.5” (42 cm) long
• One cable with one six-pin connector and one six/eight-pin connector for video cards, 16.5” (42 cm) to the first connector, 5.9” (15 cm) between connectors
• One cable with three SATA power connectors, 12.6” (32 cm) to the first connector, 7.9” (20 cm) between the first two connectors and 5.9” (15 cm) between the second and third connectors
• One cable with two standard peripheral power connectors and one floppy disk drive power connector, 12.6” (32 cm) to the first connector, 7.9” (20 cm) between connectors

All other wires are 18 AWG, which is the correct gauge to be used.

The number of connectors is perfect for a 450 W power supply. In fact, it comes with two connectors for video cards, a feature not usually found on power supplies below 500 W.

Figure 4: Cables

Let’s now take an in-depth look inside this power supply.[nextpage title=”A Look Inside the SilverStone ST45SF-G”]

We decided to disassemble this power supply to see what it looks like inside, how it is designed, and what components are used. Please read our “Anatomy of Switching Power Supplies” tutorial to understand how a power supply works and to compare this power supply to others.  

On this page we will have an overall look, and then in the following pages we will discuss in detail the quality and ratings of the components used.

Figure 5: Top view

Figure 6: Front quarter view

Figure 7: Rear quarter view

Figure 8: The printed circuit board

[nextpage title=”Transient Filtering Stage”]

As we have mentioned in other articles and reviews, the first place we look when opening a power supply for a hint about its quality, is its filtering stage. The recommended components for this stage are two ferrite coils, two ceramic capacitors (Y capacitors, usually blue), one metalized polyester capacitor (X capacitor), and one MOV (Metal-Oxide Varistor). Very low-end power supplies use fewer components, usually removing the MOV and the first coil.

In the transient filtering stage, this power supply is flawless, with one X capacitor and two Y capacitors more than the minimum required.

Figure 9: Transient filtering stage (part 1)

Figure 10: Transient filtering stage (part 2)

On the next page, we will have a more detailed discussion about the components used in the SilverStone ST45SF-G.

[nextpage title=”Primary Analysis”]

On this page, we will take an in-depth look at the primary stage of the SilverStone ST45SF-G. For a better understanding, please read our “Anatomy of Switching Power Supplies” tutorial.

This power supply uses one GBU1006 rectifying bridge, which is attached to an individual heatsink. This bridge supports up to 10 A at 100° C. In theory, you would be able to pull up to 1,150 W from a 115 V power grid. Assuming 80% efficiency, the bridge would allow this unit to deliver up to 1,380 W without burning itself out (or 1,553 W at 90% efficiency). Of course, we are only talking about this particular component. The real limit will depend on all the components combined in this power supply.

Figure 11: Rectifying bridge

The active PFC circuit uses one
IPW50R140CP MOSFETs, which supports up to 23 A at 25° C or 15 A at 100° C in continuous mode (note the difference temperature makes), or 56 A at 25° C in pulse mode. This transistor presents a 140 mΩ maximum resistance when turned on, a characteristic called RDS(on). The lower the number the better, meaning that the transistor will waste less power, and the power supply will have a higher efficiency.

Figure 12: The active PFC diode and the active PFC transistor

The active PFC circuit is managed by a CM6502 active PFC controller.

The output of the active PFC circuit is filtered by one 330 µF x 450 V Japanese electrolytic capacitor from Panasonic, labeled at 105° C.

Figure 13: Capacitor

In the switching section, two STP20NM50FD MOSFETs are employed using a resonant configuration. Each transistor supports up to 20 A at 25° C or 14 A at 100° C in continuous mode or up to 80 A at 25° C in pulse mode, with a maximum RDS(on) of 250 mΩ.

Figure 14: Switching transistors

The switching transistors are controlled by a CM6901 controller. 

Figure 15: Resonant controller (left) and active PFC controller (right)

Let’s now take a look at the secondary of this power supply.

[nextpage title=”Secondary Analysis”]

As one would expect in a high-efficiency power supply, the SilverStone ST45SF-G uses a synchronous design, where the Schottky rectifiers are replaced with MOSFETs. Also, the reviewed product uses a DC-DC design in its secondary. This means that the power supply is basically a +12 V unit, with the +5 V and +3.3 V outputs produced by two smaller power supplies connected to the main +12 V rail. Both designs are used to increase efficiency.

The +12 V output uses two IRLB3034PbF MOSFETs, each one supporting up to 343 A at 25° C or 243 A at 100° C in continuous mode, or up to 1,372 A at 25° C in pulse mode, with a maximum RDS(on) of 1.7 mΩ.

Figure 16: The +12 V transistors

As explained, the +5 V and +3.3 V outputs are produced by two DC-DC converters, which are situated on individual printed circuit boards located in the secondary section of the power supply. Each converter is controlled by an APW7073 integrated circuit and uses one CSD86350Q5D MOSFET. This transistor supports up to 40 A at 25° C in continuous mode and up to 120 A at 25° C in pulse mode, with a maximum RDS(on) of 2.7 mΩ.

Figure 17: One of the DC-DC converters

Figure 18: One of the DC-DC converters

The outputs of the power supply are monitored by a PS223 integrated circuit, which supports over voltage (OVP), under voltage (UVP), over current (OCP), and over temperature (OTP) protections. There are two +12 V over current channels, but the manufacturer decided to use only one of them, therefore resulting in this unit having a single +12 V rail configuration.

Figure 19: Monitoring circuit

The electrolytic capacitors available in the secondary are also Japanese, from Chemi-Con and Rubycon, and labeled at 105° C, as usual.

Figure 20: Capacitors

[nextpage title=”Power Distribution”]

In Figure 21, you can see the power supply label containing all the power specs.

Figure 21: Power supply label

As you can see, there is only one +12 V rail, so there is not much to talk about here.

Let’s see how much power this unit can really deliver. [nextpage title=”Load Tests”]

We conducted several tests with this power supply, as described in the article, “Hardware Secrets Power Supply Test Methodology.”  

First, we tested this power supply with five different load patterns, trying to pull around 20%, 40%, 60%, 80%, and 100% of its labeled maximum capacity (actual percentage used listed under “% Max Load”), watching the behavior of the reviewed unit under each load. In the table below, we list the load patterns we used and the results for each load.

If you add all the powers listed for each test, you may find a different value than what is posted under “Total” below. Since each output can have a slight variation (e.g., the +5 V output working at 5.10 V), the actual total amount of power being delivered is slightly different than the calculated value. In the “Total” row, we are using the real amount of power being delivered, as measured by our load tester.

The +12VA and +12VB inputs listed below are the two +12 V independent inputs from our load tester. During this test, the +12VA and +12VB inputs were connected to the power supply’s single +1
2 V rail. (The +12VB input was connected to the power supply EPS12V connector.)

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	3 A (36 W)	6 A (72 W)	9 A (108 W)	12.5 A (150 W)	15.5 A (186 W)
+12VB	3 A (36 W)	6 A (72 W)	9 A (108 W)	12.5 A (150 W)	15 A (180 W)
+5 V	1 A (5 W)	2 A (10 W)	4 A (20 W)	6 A (30 W)	8 A (40 W)
+3.3 V	1 A (3.3 W)	2 A (6.6 W)	4 A (13.2 W)	6 A (19.8 W)	8 A (26.4 W)
+5VSB	1 A (5 W)	1.5 A (7.5 W)	2 A (10 W)	2.5 A (12.5 W)	3 A (15 W)
-12 V	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)	0.5 A (6 W)
Total	91.7 W	172.2 W	260.2 W	361.4 W	449.8 W
% Max Load	20.4%	38.3%	57.8%	80.3%	100.0%
Room Temp.	43.6° C	43.2° C	42.8° C	43.2° C	45.4° C
PSU Temp.	47.8° C	46.7° C	46.2° C	46.5° C	49.8° C
Voltage Regulation	Pass	Pass	Pass	Pass	Pass
Ripple and Noise	Pass	Pass	Pass	Pass	Pass
AC Power	106.0 W	192.5 W	291.0 W	414.2 W	525.3 W
Efficiency	86.5%	89.5%	89.4%	87.3%	85.6%
AC Voltage	117.2 V	116.8 V	115.4 V	114.6 V	113.9 V
Power Factor	0.969	0.970	0.978	0.986	0.989
Final Result	Pass	Pass	Pass	Pass	Pass

The 80 Plus Gold certification guarantees minimum efficiencies of 87% at 20% load, 90% at 50% load, and 87% at 100% load. In our tests, the SilverStone ST45SF-G presented 86.5% efficiency at 20% load. We didn’t test this power supply at 50% load, but considering that we saw 89.5% efficiency at 40% load and 89.4% efficiency at 60% load, we can assume that this unit is able to achieve 90% efficiency at 50% load. At full load, we saw 85.6% efficiency, which is below the minimum advertised by the 80 Plus Gold certification. We tested two samples of this power supply, and with the other sample, efficiency at full load was at 84.9 percent. Keep in mind that we tested this power supply between 42° C and 45° C, while the 80 Plus tests are conducted at 23° C, and efficiency drops as temperature increases.

Voltage regulation varied a bit between the two samples we tested. With one of the samples, all positive voltages were within 3% of their nominal values, which is what we want to see. With the second sample, however, voltages were sometimes outside this tighter range but still inside the allowed margin. See table below. The ATX12V specification states that positive voltages must be within 5% of their nominal values, and negative voltages must be within 10% of their nominal values.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	≤ 3%	≤ 3%	≤ 3%	≤ 3%	≤ 3%
+12VB	≤ 3%	≤ 3%	≤ 3%	≤ 3%	≤ 3%
+5 V	≤ 3%	≤ 3%	≤ 3%	≤ 3%	≤ 3%
+3.3 V	≤ 3%	≤ 3%	≤ 3%	+3.18 V	+3.14 V
+5VSB	≤ 3%	≤ 3%	≤ 3%	+4.82 V	+4.78 V
-12 V	-11.24 V	-11.34 V	-11.47 V	≤ 3%	≤ 3%

Let’s discuss the ripple and noise levels on the next page.

[nextpage title=”Ripple and Noise Tests”]

Voltages at the power supply outputs must be as “clean” as possible, with no noise or oscillation (also known as “ripple”). The maximum ripple and noise levels allowed are 120 mV for +12 V and -12 V outputs, and 50 mV for +5 V, +3.3 V and +5VSB outputs. All values are peak-to-peak figures. We consider a power supply as being top-notch if it can produce half or less of the maximum allowed ripple and noise levels.

The reason why we tested two samples of the SilverStone ST45SF-G was because the first sample we received provided ripple and noise levels above the maximum allowed at the +3.3 V output. Wondering if we received a defective product, we asked the manufacturer for a second sample, which passed our tests, as you can see below.

Input	Test 1	Test 2	Test 3	Test 4	Test 5
+12VA	26.8 mV	27.2 mV	36.6 mV	41.4 mV	53.2 mV
+12VB	25.8 mV	26.2 mV	34.4 mV	39.2 mV	51.4 mV
+5 V	14.8 mV	18.2 mV	22.8 mV	28.2 mV	34.4 mV
+3.3 V	10.6 mV	12.8 mV	15.4 mV	20.6 mV	25.4 mV
+5VSB	9.8 mV	12.2 mV	14.0 mV	20.2 mV	22.6 mV
-12 V	29.0 mV	38.2 mV	53.4 mV	89.2 mV	99.8 mV

Below you can see the waveforms of the outputs during test five.

Figure 22: +12VA input from load tester during test five at 449.8 W (53.2 mV)

Figure 23: +12VB input from load tester during test five at 449.8 W (51.4 mV)

Figure 24: +5V rail during test five at 449.8 W (34.4 mV)

Figure 25: +3.3 V rail during test five at 449.8 W (25.4 mV)

Let’s see if we can pull more than 450 W from this unit. [nextpage title=”Overload Tests”]

Below you can see the maximum we could pull from this power supply. The objective of this test is to see if the power supply has its protection circuits working properly. This unit passed this test, since it shut down when we tried to pull more than what is listed below. During this test, noise and ripple
levels at the -12 V output surpassed the maximum allowed, at 142.8 mV, and the +3.3 V output was below the minimum allowed voltage, at +3.12 V.

Input	Overload Test
+12VA	20.5 A (246 W)
+12VB	20.5 A (246 W)
+5 V	9 A (45 W)
+3.3 V	9 A (29.7 W)
+5VSB	3 A (15 W)
-12 V	0.5 A (6 W)
Total	578.4 W
% Max Load	128.5%
Room Temp.	40.4° C
PSU Temp.	42.4° C
AC Power	694.0 W
Efficiency	83.3%
AC Voltage	112.0 V
Power Factor	0.991

[nextpage title=”Main Specifications”]

The main specifications for the SilverStone ST45SF-G power supply include:

• Standards: SFX12V
• Nominal labeled power: 450 W
• Measured maximum power: 578.4 W at 40.4° C
• Labeled efficiency: Between 87% and 90%, 80 Plus Gold certification
• Measured efficiency: Between 85.6% and 89.5%, at 115 V (nominal, see complete results for actual voltage)
• Active PFC: Yes
• Modular Cabling System: Yes
• Motherboard Power Connectors: One 20/24-pin connector and two ATX12V connectors that together form an EPS12V connector
• Video Card Power Connectors: One six-pin connector and one six/eight-pin connector on the same cable
• SATA Power Connectors: Three on one cable
• Peripheral Power Connectors: Two on one cable
• Floppy Disk Drive Power Connectors: One
• Protections (as listed by the manufacturer): Over voltage (OVP), under voltage (UVP), over current (OCP), over power (OPP), short-circuit (SCP), and no-load (NLO) protections
• Are the above protections really available? Yes.
• Warranty: Three years
• More Information: https://www.silverstonetek.com
• Average Price in the U.S.*: USD 100.00

* Researched at Newegg.com on the day we published this review.

[nextpage title=”Conclusions”]

The main highlights of the SilverStone ST45SF-G are its 80 Plus Gold certification and its fully modular cabling system. It costs USD 20 more than its sister, the ST45SF, which comes with the 80 Plus Bronze certification.

The problem with this power supply is its price. We know how difficult it is to make a compact, high-efficiency power supply (due to temperature), and SilverStone will probably have a hard time explaining to users why they should buy this USD 100 unit when there are other SFX12V power supplies (most of them are not as good, by the way) on the market selling for half of that.

If you are building a small form factor (SFF) computer and want a 450 W power supply (which is the maximum wattage you can get from an SFX12V power supply) with the 80 Plus Gold certification, the SilverStone ST45SF-G is your only option.

We are giving this unit our Silver Award instead of the Golden because we had issues with the first sample we received, and efficiency at full load at high temperature was below 87 percent.