Sparkle Power's 250W ATX12V 80 Plus SPI250EP

Power
Viewing page 4 of 5 pages. Previous 1 2 3 4 5 Next

TESTING

For a fuller understanding of ATX power supplies, please read the reference article Power Supply Fundamentals & Recommended Units. Those who seek source materials can find Intel's various PSU design guides at Form Factors.

For a complete rundown of testing equipment and procedures, please refer to SPCR's PSU Test Platform V.4. The testing system is a close simulation of a moderate airflow mid-tower PC optimized for low noise.

In the test rig, the ambient temperature of the PSU varies proportionately with its output load, which is exactly the way it is in a real PC environment. But there is the added benefit of a high power load tester which allows incremental load testing all the way to full power for any non-industrial PC power supply. Both fan noise and voltage are measured at various standard loads. It is, in general, a very demanding test, as the operating ambient temperature of the PSU often reaches >40°C at full power. This is impossible to achieve with an open test bench setup.

The 120mm fan responsible for "case airflow" is deliberately run at a steady low level (6~7V) when the system is run at lowloads. When the test loads become greater, the 120mm fan is turned up to a higher speed, but one that doesn't affect the noise level of the overall system. Anyone who is running a system that draws 400W or more would definitely want more than 20CFM of airflow through their case, and at this point, the noise level of the exhaust fan is typically not the greatest concern.

Great effort has been made to devise as realistic an operating environment for the PSU as possible, but the thermal and noise results obtained here still cannot be considered absolute. There are too many variables in PCs and too many possible combinations of components for any single test environment to provide infallible results. And there is always the bugaboo of sample variance. These results are akin to a resume, a few detailed photographs, and some short sound bites of someone you've never met. You'll probably get a pretty good overall representation, but it is not quite the same as an extended meeting in person.

SPCR's high fidelity sound recording system was used to create MP3 sound files of this PSU. As with the setup for recording fans, the position of the mic was 3" from the exhaust vent at a 45° angle, outside the airflow turbulence area. The photo below shows the setup (a different PSU is being recorded). All other noise sources in the room were turned off while making the sound recordings.

INTERPRETING TEMPERATURE DATA

It important to keep in mind that fan speed varies with temperature, not output load. A power supply generates more heat as output increases, but is not the only the only factor that affects fan speed. Ambient temperature and case airflow have almost as much effect. Our test rig represents a challenging thermal situation for a power supply: A large portion of the heat generated inside the case must be exhausted through the power supply, which causes a corresponding increase in fan speed.

When examining thermal data, the most important indicator of cooling efficiency is the difference between intake and exhaust. Because the heat generated in the PSU loader by the output of the PSU is always the same for a given power level, the intake temperature should be roughly the same between different tests. The only external variable is the ambient room temperature. The temperature of the exhaust air from the PSU is affected by several factors:

  • Intake temperature (determined by ambient temperature and power output level)
  • Efficiency of the PSU (how much heat it generates while producing the required output)
  • The effectiveness of the PSU's cooling system, which is comprised of:
    • Overall mechanical and airflow design
    • Size, shape and overall surface area of heatsinks
    • Fan(s) and fan speed control circuit

The thermal rise in the power supply is really the only indicator we have about all of the above. This is why the intake temperature is important: It represents the ambient temperature around the power supply itself. Subtracting the intake temperature from the exhaust temperature gives a reasonable gauge of the effectiveness of the power supply's cooling system. This is the only temperature number that is comparable between different reviews, as it is unaffected by the ambient temperature.

TEST RESULTS

Ambient conditions during testing were 21°C and 19 dBA. AC input was 120V, 60Hz.

OUTPUT, VOLTAGE REGULATION & EFFICIENCY: Sparkle Power SPI250EP
DC Output Voltage (V) + Current (A)
Total DC Output
AC Input
Calculated Efficiency
+12V1
+12V2
+5V
+3.3V
-12V
+5VSB
12.35
0.98
12.35
5.18
0.97
3.34
0.1
0.1
18.8
28.0
67.2%
12.35
12.35
1.68
5.16
0.98
3.34
0.94
0.1
0.3
31.8
41.5
76.0%
12.32
0.97
12.32
1.68
5.16
0.99
3.34
-
0.1
0.3
40.5
51.7
78.3%
12.32
1.92
12.32
1.71
5.15
1.95
3.33
1.73
0.2
0.5
65.5
80.3
81.5%
12.32
1.88
12.32
3.27
5.14
1.96
3.33
2.55
0.4
0.9
90.6
109
83.4%
12.21
3.78
12.21
4.95
5.09
3.56
3.35
3.63
0.6
1.5
151.4
183
82.7%
12.15
6.51
12.15
5.02
5.01
5.35
3.24
4.85
0.6
2.0
199.7
241
82.9%
12.06
6.64
12.06
8.51
5.98
6.16
3.24
5.50
0.78
2.4
251.2
306
82.1%
+12V Ripple (peak-to-peak): 54mV @ 90W to 84mV @ 251W (max)
+5V Ripple (peak-to-peak): 22mV @ 150W to 28mV @ 251W
+3.3V Ripple (peak-to-peak): 15mV @ 90W 21mV @ 251 (max)
NOTE: The current and voltage for -12V and +5VSB lines is not measured but based on switch settings of the DBS-2100 PS Loader. It is a tiny portion of the total, and potential errors arising from inaccuracies on these lines is <1W.

 

OTHER DATA SUMMARY: Sparkle Power SPI250EP
DC Output (W)
18.8
31.8
40.5
65.5
90.6
151.4
199.7
251.2
Intake Temp (°C)
21
21
21
22
22
23
23
24
Exhaust Temp (°C)
23
23
23
23
26
29
31
31
Temp Rise (°C)
2
2
2
1
4
6
8
7
Fan Voltage (V)
6.2
6.2
6.5
7.1
7.1
8.0
11.0
11.9
SPL (dBA@1m)
19
19
20
21
21
22
27
28
Power Factor
0.97
0.98
0.99
0.99
1.00
1.00
0.99
1.00
AC Power in Standby: 0.3W / 0.13 PF
AC Power with No Load, PSU power On: 6.5W / 0.73 PF
NOTE: The ambient room temperature during testing can vary a few degrees from review to review. Please take this into account when comparing PSU test data.

ANALYSIS

1. EFFICIENCY — This is a measure of AC-to-DC conversion efficiency. The ATX12V Power Supply Design Guide recommends 80% efficiency or better at all output power loads. 80% efficiency means that to deliver 80W DC output, a PSU draws 100W AC input, and 20W is lost as heat within the PSU. Higher efficiency is preferred for reduced energy consumption and cooler operation. The latter allows reduced cooling airflow, which translates to lower noise.

Above ~50W, the efficiency of the SPI250EP exceeded 80% all the way to full output. Below 50W, efficiency dropped to 78% by 40W, and to 67% by 20W. The SPI250EP is not quite the equal of its FlexATX 220W brethren.

We began testing at 20W load quite recently, so there are only a handful of PSU samples for this data point. All the tested data is compiled in the table below, ordered by efficiency at 20W. This is simply a point of comparison. Keep in mind that the 20W efficiency measurements are subject to greater error than the ones at higher power because the actual measured numbers are that much smaller (i.e., at 20W, 1W = 5%, while at 40W, 1W = 2.5%).

Low Load Efficiency Comparison
PSU
20W
30W
40W
65W
90W
picoPSU, 80W brick
79.4%
n/a
83.6%
84.8%
84.7%
picoPSU, 120W brick
77.7%
n/a
85.6%
87.1%
87.1%
Sparkle SPI220LE
73.0%
77.7%
80.5%
82.8%
83.8%
Seasonic EcoPower 300
68.0%
73.8%
75.4%
81.1%
82.4%
Sparkle SPI250EP
67.2%
76.0%
78.3%
81.5%
83.4%
Seasonic M12II-430
66.2%
n/a
74.9%
78.6%
81.4%
Enermax Modu82+ 625W
66.1%
n/a
78.4%
80.0%
80.9%
Seasonic S12II-380
65.4%
n/a
76.3%
79.4%
81.5%
Corsair TX650W
62.9%
n/a
70.9%
77.5%
81.9%
Corsair VX450W
61.3%
n/a
72.8%
79.1%
80.1%
NOTE: The highest efficiency reached is not indicated by the 90W column; many models don't reach peak efficiency till > 50% of rated power.

The low power efficiency is not quite the equal of the earlier tested SPI220LE, but at 30W and higher, it gets within 1~2%. Surprisingly, the 625W Enermax Modu82+ matches its efficiency at 40W. This throws the whole argument for lower rated PSUs into question: What's the point if a 625W PSU can match the efficiency of a 250W PSU at a load as low as 40W? Doesn't the efficiency curve apply? The answer to these questions is in the name of the Enermax. Modu82+ refers to the "Bronze" category of 80 Plus that this product is supposed to fall into: It has 82% efficiency at 20% load, not just 80% efficiency. Ergo, if we had a "Bronze" 80 Plus 250W PSU, it would have higher efficiency at 40W than the Modu82+ 625.

However, it's important to note that at 20W load, even a big 10% efficiency difference accounts for only 2W. The 78.4% efficiency of the Sparkle SPI250EP at 40W load compared to the Corsair TX650W's 70.9% is a real difference of 5W.

2. VOLTAGE REGULATION refers to how stable the output voltages are under various load conditions. The ATX12V Power Supply Design Guide calls for the +12, +5V and +3.3V lines to be maintain within ±5%. VR in the SPI250EP sample was excellent. There was no significant sag on any of the lines, especially the all-important 12V line, even up to the rated output.

3. AC RIPPLE refers to unwanted "noise" artifacts in the DC output of a switching power supply. It's usually very high in frequency (in the order of kilohertz or megahertz). The peak-to-peak value is measured. The ATX12V Guide allows up to 120mV (peak-to-peak) of AC ripple on the +12V line and 50mV on the +5V and +3.3V lines. Ripple in the SPI250EP stayed well within the 1% allowed by ATX12V on all voltage lines at all loads.

4. POWER FACTOR is ideal when it measures 1.0. In the most practical sense, PF is a measure of how "difficult" it is for the electric utility to deliver the AC power into your power supply. High PF reduces the AC current draw, which reduces stress on the electric wiring in your home (and elsewhere up the line). It also means you can do with smaller, cheaper UPS backup; they are priced according to their VA (volt-ampere) rating. PF on this sample was close to perfect across all loads, as is the norm for most power supplies with active PF correction circuitry.

5. AC INPUT VOLTAGE TESTS

Low VAC: This is to check the stability of the PSU under brownout conditions where the AC line voltage drops from the 110~120V norm. The unit was pushed down to 100VAC without any problems. DC output voltage regulation remained unchanged from that achieved at 120VAC.

LOW VAC TEST: Sparkle SPI250EP @ 200W load
VAC
AC Power Input
Efficiency
242
234W
85.5%
120
241W
82.9%
110
242W
82.6%
100
244W
82.0%

240 VAC Input: Most power supplies achieve higher efficiency with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, used to check power supply efficiency for the benefit of those who live in 240VAC mains regions. The 240VAC efficiency advantage measured 2.6 percentage points higher at 200W load.

6. LOW LOAD TESTING revealed no problems starting at low loads. The power draw at standby was a super low 0.3W, and power consumption with no load was very good at 6.5W.

7. TEMPERATURE & COOLING

Cooling was excellent, with the temperature rise through the PSU staying in single digits even at full load. Given the high efficiency and modest output power, this result is not a surprise. It's far superior to the FlexATX SPI220LE, which is hampered by a tiny fan, high component density (airflow impedance) and small form factor.

8. FAN, FAN CONTROLLER and NOISE

The acoustics are surprisingly good. The noise at turn-on is low enough that the quality of the sound isn't much of a factor. It's somewhat tonal but at 19 dBA@1m, it's a very low level that's probably inaudible in most environments. The noise of the PC it's in or the room ambient itself would probably swamp it. From up close, you can hear both fan and electronic noise, the latter a bit higher in level than other PSUs tested recently. The electronic noise is a bit of high frequency squealing that never quite disappears until the fan speeds up considerably at higher loads, when the turbulence noise covers it up. It might be bothersome if you have very sensitive hearing, very quiet components and a super low ambient.

The classic ball-bearing fan clicking / buzzing is mostly absent here; hopefully, this is not just a case of a lucky sample. Even at full load, with the feed voltage just uner 12V, the measured SPL was only 28 dBA@1m. which is the actual specification of the fan by itself. In all these years of PSU testing, this is the first time that the measured SPL of a PSU has not been many decibels higher than the stated SPL for its fan.

The fan controller appears to have a linear temperature-to-voltage curve, as with most SPI and FSP power supplies reviewed in the past. That is, any temperature increase causes a corresponding proportionate increase in fan voltage. But because the power output is so modest and the efficiency high, the PSU remains pretty quiet till over 150W load.

The fan controller is somewhat sensitive, with sudden changes in load causing fairly quick changes up or down in fan speed. This effect is not that audible, however, and certainly much better than the earlier SPI220LE.

The high starting voltage of 6.2V to the fan is quite useful for the modder considering a fan swap. Most 12VDC 80x25mm fans will start easily with that voltage. A swap for a smoother, quieter fan in combination with a fresh air intake duct (or a case with a dedicated PSU chamber such as the Antec P180-182-190, Fusion, NSK3480 or Mini P180 — though cables are too short for these cases) would make the SPI250EP a "silent" power supply. Basically any 80mm 12VDC fan rated close to 0.1A would work; the point would be to use one smoother and quieter than the stock fan.



Previous 1 2 3 4 5 Next

Power - Article Index
Help support this site, buy from one of our affiliate retailers!
Search: