SilverStone Strider ST50F 500 W Power Supply Review
By Gabriel Torres on April 25, 2008
SilverStone has several power supply lines ranging from 350 W to 1,200 W and we were very curious to review a product from this manufacturer. For our first review of a SilverStone product, we decided to take a look at a mainstream product, Strider ST50F, which is a 500 W power supply costing only USD 67 at Newegg.com. How this product compares to other units from this power range we reviewed so far? Can it really deliver its rated 500 W? Is this a good product for Average Joe? Let’s see.
As you can see, this power supply uses a big 120 mm brushless fan on its bottom (the power supply is upside down on Figures 1 and 2) and a big mesh on the rear side where on traditional ATX power supplies we have an 80 mm fan. We like this design as it provides not only a better airflow but the power supply produces less noise, as the fan can rotate at a lower speed in order to produce the same airflow as an 80 mm fan.
This power supply has active PFC, a feature that provides a better usage of the power grid and allows SilverStone to sell this product in Europe (read more about PFC on our Power Supply Tutorial). As for efficiency, Silvertone says that this product has a typical 80% efficiency. Of course we will measure this to see if what the manufacturer claim is true. The higher the efficiency the better – an 80% efficiency means that 80% of the power pulled from the power grid will be converted in power on the power supply outputs and only 20% will be wasted. This translates into less consumption from the power grid (as less power needs to be pulled in order to generate the same amount of power on its outputs), meaning lower electricity bills.
The main motherboard cable uses a 20/24-pin connector and this power supply has two ATX12V connectors that together form an EPS12V connector.
This power supply comes with five peripheral power cables: one auxiliary power cable for video cards with two 6-pin connectors attached, one cable containing three standard peripheral power connectors and one floppy disk drive connector, one cable containing three standard peripheral power connectors and two cables with three SATA power connectors each.
The number of power plugs provided by this power supply is more than enough for the average user, with six SATA power plugs and six standard peripheral power plugs. The only thing we didn’t like was that the two 6-pin plugs for video cards were attached to the same cable coming from the power supply. We think it would be better to have them using separated cables coming from inside the unit.
On this power supply all wires are 18 AWG except the wires for -12 V (blue) and power good (grey), which are 24 AWG and probably the thinner wires we’ve seen on a power supply to date. This isn’t exactly a problem as these two outputs don’t pull a lot of current.
On the aesthetic side SilverStone didn’t use any kind of sleeving on the cables, which may have helped reducing the price of this unit.
This power supply is manufactured by FSP and after disassembling it we discovered that it uses the same project as Zalman ZM360B-APS and ZM460B-APS, possibly being identical to Zalman ZM460B-APS (since we haven’t reviewed ZM460B-APS yet we can’t say that for sure). As during our reviews ZM360B-APS proved to be an excellent power supply we were hoping to see good results with this model from SilverStone as well.
Now let’s take an in-depth look inside this power supply.
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.
This page will be an overview, and then in the following pages we will discuss in detail the quality and ratings of the components used.
This power supply uses the same project as Zalman ZM360B-APS and ZM460B-APS power supplies, as you can see comparing Figure 4 to Figure 5.
One interesting thing about this power supply is that it uses its housing as an extension to the secondary heatsink, as you can see in Figure 6. The manufacturer used thermal grease between the secondary heatsink and the power supply housing.
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.
Even though this power supply has two additional Y capacitors on its transient filtering stage and two additional X capacitors and one additional ferrite coil after the rectifying bridge, it doesn’t have a MOV, which is essential to cut spikes coming from the power grid.
The components used here are identical to the ones used on Zalman ZM360B-APS (and possibly on Zalman ZM460B-APS).
In the next page we will have a more detailed discussion about the components used in the Strider ST50F.
We were very curious to check what components were chosen for the power section of this power supply, especially because it uses the same project as Zalman ZM360B-APS and ZM460B-APS.
This power supply uses one GBU806 rectifying bridge in its primary stage, which can deliver up to 8 A (rated at 100° C). This bridge is attached to the same heatsink where the switching transistors are located. Zalman ZM360B-APS uses a GBU606 bridge, which can deliver less current (6 A). We can’t tell about ZM460B-APS as we haven’t reviewed this unit yet. This is more than adequate rating for a 500 W power supply. The reason why is that at 115 V this unit would be able to pull up to 920 W from the power grid; assuming 80% efficiency, the bridge would allow this unit to deliver up to 736 W without burning this component. Of course we are only talking about this component and the real limit will depend on all other components from the power supply.
On the active PFC circuit two 20N60C3 power MOSFET transistors are used, each one capable of handling up to 20.7 A at 25° C or 13.1 at 100° C in continuous mode, or up to 62.1 A at 25° C in pulse mode. These transistors are located on a separated heatsink, together with the active PFC diode. Zalman ZM360B-APS uses two STP14NK50ZFP, which are capable of handling less current (14 A at 25° C or 7.6 at 100° C in continuous mode, or up to 48 A at 25° C in pulse mode). Once again we can’t tell about ZM460B-APS as we haven’t reviewed this unit yet.
On the switching section this power supply uses two STF21NM50N power MOSFET transistors in two-transistor forward configuration. Each one of these transistors can deliver up to 18 A at 25° C or 11A at 100° C or up to 72 A at 25° C in pulse mode, which is the mode used. Here again the components were upgraded, as Zalman ZM360B-APS uses two FQPF9N50C, which can deliver less current (9 A at 25° C or 5.4 A at 100° C in continuous mode, or up to 36 A at 25° C in pulse mode). Once again we can’t tell about ZM460B-APS as we haven’t reviewed this unit yet. As mentioned, these transistors are located on the same heatsink as the rectifying bridge.
The primary section is controlled by a CM6800 integrated circuit, which is a very popular active PFC and PWM controller combo. It is located on a small printed circuit board attached to the main board.
This power supply has six Schottky rectifiers on its secondary, two for each positive voltage output (+12 V, +5 V and +3.3 V). Zalman ZM360B-APS uses only four rectifiers and we can’t tell about Zalman ZM460B-APS yet, even though we suspect Zalman ZM460B-APS and SilverStone Strider ST50F are identical.
The maximum theoretical current each line can deliver is given by the formula I / (1 - D), where D is the duty cycle used and I is the maximum current supported by the rectifying diode. Just as an exercise, we can assume a typical duty cycle of 30%.
The +12 V output is produced by two MBR2560CT Schottky rectifiers connected in parallel. Since each one supports up to 30 A at 130° C (15 A per internal diode) we have a maximum theoretical current for the +12 V output of 43 A or 514 W [(15 A x 2) / (1 - 0.30)]. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the coil.
The +5 V output is produced by two MBR3045N Schottky rectifiers, supporting up to 30 A at 100° C each (15 A per internal diode). So the maximum theoretical current the +5 V output can deliver is of 43 A or 214 W. Of course the maximum current (and thus power) this line can really deliver will depend on other components, especially the coil, as we mentioned before.
The +3.3 V output is produced by other two MBRP3045N Schottky rectifiers, supporting up to 30 A at 100° C each (15 A per internal diode). So the maximum theoretical current the +3.3 V output can deliver is of 43 A or 141 W. As mentioned the real power this line can deliver depends on other factors.
This power supply uses a PS223 monitoring integrated circuit, which is in charge of the power supply protections, like OCP (over current protection). OCP was really activated, as we will talk about later. This IC also provides over voltage protection (OVP), under voltage protection (UVP) and over temperature protection (OTP), but not over power protection (OPP).
The thermal sensor is located under the secondary heatsink, as you can see in Figure 17 (we took this picture with the heatsink removed). This sensor is used to control the fan speed according to the power supply internal temperature and to shut down the power supply in an overheating situation. As we mentioned, the monitoring IC supports this protection and SilverStone says this unit features this protection. We, however, couldn’t test this feature, as the power supply was always working very cool.
On this power supply all electrolytic capacitors are Taiwanese, from CapXon, with the active PFC capacitor rated at 85° C and the secondary capacitors rated at 105° C.
In Figure 18, you can see the power supply label containing all the power specs.
As you can see this power supply has two +12 V virtual rails. These rails are distributed as following:
One problem with this power supply is the lack of precise information. The power supply label doesn’t mention anything about the maximum combined power we can pull from the two 12 V rails at the same time. On the product box it is written that the maximum combined current for the two rails is of 29 A (which equals 348 W), but on SilverStone website it is written that the maximum combined current for the two rails if of 36 A or 432 W.
We tested OCP circuit and it is really active as we will discuss later.
Now let’s see if this power supply can really deliver 500 W of power.
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 how the reviewed unit behaved under each load. In the table below we list the load patterns we used and the results for each load. This was the same configuration we used with other 500 W power supplies we’ve reviewed recently, like Antec EarthWatts 500 W and Enermax Liberty DXX 500 W.
For the 100% load test we used two patterns. On the first one, test number five, we respected the maximum combined limit for the two +12 V rails printed on the power supply box (29 A or 348 W). In order to respect this limit, however, we were testing the power supply with more current on the +5 V and +3.3 V lines than we wanted. So we included a sixth pattern also pulling 500 W from Strider ST50F but pulling more current from +12 V and less current from +5 V and +3.3 V, using the same pattern used on the tests of the two abovementioned power supplies.
If you add all the power listed for each test, you may find a different value than what is posted under “Total” below. Since each output can vary slightly (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. On the “Total” row we are using the real amount of power being delivered, as measured by our load tester.
+12V2 is the second +12V input from our load tester and during our tests we connected the power supply EPS12V connector to it. Keep in mind that the EPS12V connector is half connected to the power supply +12V1 rail and half to the +12V2 rail. The video card auxiliary power plug, which is connected to the power supply +12V2 rail, was connected on the +12V1 input from our load tester.
4 A (48 W)
8 A (96 W)
11 A (132 W)
14 A (168 W)
14.5 A (174 W)
17 A (204 W)
3 A (36 W)
6 A (72 W)
10 A (120 W)
14 A (168 W)
14.5 A (174 W)
17 A (204 W)
1 A (5 W)
2 A (10 W)
4 A (20 W)
6 A (30 W)
16 A (80 W)
9 A (45 W)
1 A (3.3 W)
2 A (6.6 W)
4 A (13.2 W)
6 A (19.8 W)
16 A (52.8 W)
9 A (29.7 W)
1 A (5 W)
1 A (5 W)
1.5 A (7.5 W)
2 A (10 W)
2.5 A (12.5 W)
2.5 A (12.5 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.5 A (6 W)
0.8 A (9.6 W)
0.8 A (9.6 W)
% Max Load
Ripple and Noise
The good news is that this power supply can really deliver 500 W at a room temperature of 50° C on both patterns we used for 100% load (tests five and six).
But, as you know if you read our power supply reviews, power isn’t everything.
This power supply provided an outstanding efficiency above 85% when we pulled up to 60% of the power supply maximum labeled capacity (i.e., up to 300 W) and 84% when we pulled 80% of the power supply official maximum capacity (400 W). But when we pulled 500 W from this power supply we got two results. Using pattern five, where we pulled less power from +12 V and more power from +5 V and +3.3 V, efficiency was at 80.6% – not bad, but could be better, especially when we saw efficiency over 85% on other patterns. But using pattern six, where we pulled more power from +12 V and less power from +5 V and +3.3 V, efficiency increased to 82.1%.
On efficiency this power supply was far better than Enermax Liberty DXX 500 W (which efficiency was between 76.1% and 82.5%), but Antec EarthWatts 500 W and Corsair VX450W (which is the same power supply as Antec EarthWatts 500 W but with a different housing) achieved a little bit better efficiency.
Voltage regulation during all our tests (including the overload tests we will present in the next page) was excellent, with all outputs within 3% of their nominal voltages – ATX specification defines that all outputs must be within 5% of their nominal voltages – except on -12 V, which was between -11.10 V and -11.43 V in all our tests. These numbers, however, are still inside the 10% margin that is set by the ATX spec for this output. Of course we always want to see values closer to the nominal voltage.
This power supply achieved low ripple and noise levels, but Antec EarthWatts 500 W, Corsair VX450W and Enermax Liberty DXX 500 W achieved lower levels here. During our test number five – i.e., with the power supply delivering 500 W – noise level at +12V1 input from our load tester was at 56 mV, noise level at +12V2 input from our load tester was at 46.6 mV, noise level at +5 V was at 23.6 mV and noise level at +3.3 V was at 26.5 mV. With pattern number six the results were similar. Just to remember, all values are peak-to-peak voltages and the maximum allowed set by ATX standard is 120 mV for +12 V and 50 mV for +5 V and +3.3 V.
The noise at -12 V output, however, was at a very high level. It is common for the -12 V output to achieve a noise level far above +12 V output, but so far we haven’t seen anything like this. During patterns one through four, noise level at this output was between 50 mV and 53 mV, but when we were pulling 500 W it jumped to 93.6 mV. This reflects the current increase from 0.5 A to 0.8 A on this output and the use of a very thin 24 AWG wire on this output didn’t make things easy.
Now let’s see if we could pull more power from this product.
As usual we pushed this power supply over its official limits to see what happens.
First we tried to see if over current protection was active and at what level. To test this we installed only the cables from the +12V1 virtual rail to the +12V1 input from our load tester. This included the main motherboard power cable, the two peripheral power cables and one of the ATX12V cables. Then we started increasing current at +12V1 until the power supply would shut down. This happened when we pulled more than 20 A, so over current protection (OCP) was active and set to shut down the power supply if we pulled more than 20 A from any +12V rail. This is great, because according to the power supply label each +12 V has a limit of 18 A, so OCP was configured really close to what was printed on the label. Several power supplies on the market have the OCP circuit configured with a value that is so high that it probably will never enter in action, so the power supply isn’t really protected.
Our next move was to discover what was the maximum amount of power this unit can deliver still working inside its specs.
Starting from pattern number six (see previous page) we increased current on both +12 V inputs from our load tester to 19 A. Above that the power supply would shut down.
We know that this power supply does not feature over load protection (OPP or OLP; both acronyms mean the same thing) because the monitor chip used on this unit doesn’t have this protection.
So basically overload protection for this power supply is being made a well adjusted OCP circuit. We knew that we would burn the +5 V or +3.3 V rectifiers if we tried to overload them. This is an unrealistic scenario, as on an overloaded computer the overloading will occur on the +12 V lines, due to power-hungry video cards and CPUs.
We were conservative on our overload tests this time, since we had already figured out that we could pull a maximum of 38 A (456 W) from the +12 V outputs. So we increased current on +5 V and +3.3 V to 15 A each. We think that this already represents a good overloading. Under this scenario we had the results presented in the table below.
19 A (228 W)
19 A (228 W)
15 A (75 W)
15 A (49.5 W)
2.5 A (12.5 W)
0.8 A (9.6 W)
% Max Load
At this scenario noise and ripple were at the same noise level presented in the previous page.
We could pull even more current from +5 V and +3.3 V outputs (20 A each, for a total 641.4 W and pulling 823 W from the wall, 78% efficiency) but at this scenario the power supply silently died. After opening the power supply we tested all the main semiconductors and none of them were burned and we couldn't find out which component burned.
Short circuit protection (SCP) worked fine for both +5 V and +12 V lines.
The fan used on this power supply is really quiet, even when the power supply was hot and delivering 500 W.
Silverstone Stride ST50F power supply specs include:
* Researched at Newegg.com on the day we published this review.
SilverStone Strider ST50F provides one of the best cost/benefit ratios for users looking for a good mainstream 500 W power supply. First, it can truly deliver 500 W at 50° C, which is outstanding. Second, the number of power plugs this unit has is more than a mainstream user will ever need: two 6-pin auxiliary power plugs for video cards, six SATA power plugs and six peripheral power plugs. And the third highlight from this power supply is its efficiency, above 85% if you pull up to 300 W, 84% if you pull 400 W and 80% or 82% if you pull 500 W, depending on the load pattern. And fourth we could make this power supply to deliver up to 598.5 W.
Compared to other 500 W power supplies we have reviewed recently, Antec EathWatts 500 W and Corsair VX450 W (which is the same power supply as this model from Antec but with a different housing) are better products because they provide a little higher efficiency, have overloading protection up and running, and provide a lower level of noise and ripple.
On the other hand, SilverStone Strider ST50F is a better product than Enermax Liberty DXX 500 W, which, amazingly enough, is more expensive than the reviewed product.
When you compare prices, this unit is unbeatable: it costs only USD 67 at Newegg.com, while Antec EarthWatts 500 W costs USD 90, Corsair VX450W costs USD 75 and Enermax Liberty DXX 500 W costs USD 100. It is also cheaper than Zalman ZM460B-APS (USD 85 at the same store), a power supply that uses the same project as the reviewed unit and we suspect that they might be identical (we will review this power supply from Zalman very soon to see if this is true or not).
The only problems we can see with this power supply is the lack of a MOV on the transient filtering stage and the lack of an overload protection circuit, and that is the only reason we are giving it our “Silver Award” seal instead of our “Golden Award.” But, like we said, this is a terrific product.