Lian-Li HPC-600 power supply

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 "low" loads. 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.

REAL SYSTEM POWER NEEDS: While our testing loads the PSU to full output (even 600W!) in order to verify the manufacturer's claims, real desktop PCs simply do not require anywhere near this level of power. The most pertinent range of DC output power is between about 65W and 250W, because it is the power range where most systems will be working most of the time. To illustrate this point, we conducted system tests to measure the maximum power draw that an actual system can draw under worst-case conditions. Our most power-hungry Intel 670 (P4-3.8) processor rig with nVidia 6800GT video card drew ~214W DC from the power supply under full load — well within the capabilities of any modern power supply. Please follow the link provided above to see the details. It is true that very elaborate systems with the most power hungry video card today could draw as much as another 60~100W, but the total still remains well under 400W in extrapolations of our real world measurements. As for high end dual video card gaming rigs... well, to be realistic, they have no place in silent computing today.

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 18 dBA. AC input was 117V, 60Hz.

ANALYSIS

1. EFFICIENCY was not what we had hoped, and far from what was claimed. The highest efficiency we saw was some 5 percentage points lower than what Lian Li states. To give Lian Li the benefit of a doubt, we can't claim 100% accuracy for our PSU test system, and almost every brand makes efficiency claims based on the peak achieved with the highest VAC input to make the specs look good. We can expect efficiency to rise by ~3% when running the PSU at 220V, which means peak efficiency would go up to 82%, but this is still not quite the 84% advertised. The overall efficiency curve was far from flat, starting at a low 65% at 40W and reaching the peak of 78.8% at only 200W, which is not even 50% load. Efficiency fell steadily above that level, to just 70% at full power.

2. VOLTAGE REGULATION was quite good under all but maximum load. The 5V line dropped a wee bit more than we'd have liked (to 4.76V) but the odds of anyone actuality reaching such high loads in a real systems is low. Otherwise, VR was very good.

3. RIPPLE was very low, 4-5 times better than the maximum allowed by ATX12V for the important 12V line. On the 5V and 3.3V lines, it was low enough to be virtually nonexistent.

4. POWER FACTOR was excellent at all loads. It was a little low with only 40W of load, but quickly rose after that.

5. LOW LOAD PERFORMANCE

Standby and no-load performance were both very good, with no load coming in at under 10W. The HPC-600 had no trouble starting with no load.

6. LOW AC VOLTAGE PERFORMANCE

The HPC-600 was unfazed by low AC voltage inputs. Ripple stayed well within limits and voltages stayed stable at all times.

7. TEMPERATURE & COOLING

For most systems, the temperature rise of the PSU would be nothing to worry about. The 5 or 6 degree rise is perfectly safe, and shouldn't raise any eyebrows.

At full load however, the exhaust temperature rose to quite an uncomfortable 73°C. This only occurs at maximum load, but it's still enough to cause us to cringe. Good thing that 105°C capacitor is in there.

A word of warning: Due to recent changes in our test bench, thermal results are not perfectly comparable to many of the earlier tests that we have done. Our new test bench uses a larger 120mm fan that is a more realistic simulation of the kinds of low-noise systems in use today. Earlier tests used an 80mm exhaust fan which means the newer PSU cooling data may look a bit better; it may stay cooler to a higher load point.

8. FAN, FAN CONTROLLER and NOISE

The starting speed of the fan was approximately 3.8V. Initially it was a very promising PSU, noise-wise. The sound produced by the Lian Li at low loads is not at all unpleasant.

However, by a modest 150W load, the fan had ramped up substantially, with 7.4V measured across its terminals. The resulting 32dBA@1m speaks for itself, and makes the PSU too loud to be used in a quiet system. Things get worse from here, since at all higher power levels, the fan was spinning at full speed, and noise levels were at 36dBA.

We've seen this kind of early step response in many fan controllers, and unfortunately, it's not what we hope to find.

MP3 SOUND RECORDINGS

Each of these recording have 10 seconds of silence to let you hear the ambient sound of the room, followed by 10 seconds of the product's noise.

• Lian Li HPC-600 at 90W, 21dBA@1m: One meter, One foot (30cm)

No other recordings were made because beyond 90W, it simply got too loud: 32dBA@1m at 150W and 36dBA@1m at 200W

• Seasonic M12-700 at 0~250W, 21 dBA@1m: One meter, One foot (30cm)
• Seasonic M12-700 at 300W, 25 dBA@1m: One meter, One foot (30cm)
• Silverstone Element Plus ST50EF-Plus at 0~200W, 23 dBA@1m: One meter, One foot (30cm)
• Corsair HX500 & 600W at 0~300W, 22 dBA@1m: One meter, One foot (30cm)

CONCLUSIONS

Lian Li has done a curious job with their first entry into the retail PSU market. The HPC-600 has plenty of power output, more features than you can shake a stick at, very good voltage regulation, high power factor, universal VAC input, and excellent ability to deal with low AC voltage conditions (brownouts). The component quality looks good, the fact that even the main ATX cable is detachable may be a help with installation in some cases, and the ATX pass-through connector for combining two PSUs into one is also an intriguing (if poorly documented) feature.

The execution, however, could be improved in some ways. One concern is the thermal characteristics at high load. If the exhaust temperatures are reaching over 70°C at full load, how hot are component getting inside the PSU? Of course, our test setup does not help. Anyone running a system that draws 600W continuously would be well-advised to use more case fans with greater airflow than the single slow speed 120mm Nexus in our test rig.

Secondly, the noise levels could also be improved. The unit's cooling fan starts quietly enough, but quickly ramps up to "too loud" much beyond 100W. This suggests that in actual use, the PSU may ramp up and down in noise with even minor loads. It's not great acoustic behavior. The use of a better fan controller with a more gradual speed / temperature response curve would help quite a bit. Any improvements to the noise levels and aerodynamics due to the dimpled fan blades is up for speculation. We have no way to tell whether it helps.

The efficiency we measured is not up to the level claimed, even when allowing that it was probably a peak obtained with 220VA input. The efficiency seen with 120VAC input at 40~150W, the range in which most computers idle, was rather poor by current standards, dropping as low as 65% and reaching a high of only 76.5%. In the higher ranges, the modest peak of 78.8% was reached surprisingly at below half power, above which efficiency dropped steadily to just 70% at full power.

The fins on the heatsink are quite tightly spaced, which leads us to speculate whether high airflow is required for good cooling. More widely spaced fins with greater surface area, such as those seen in the Seasonic M-12, may be a useful alteration in any future revisions of the HPC series.

The HPC-600 is an interesting product but not up to SPCR standards for acoustics or efficiency, despite its many features, good power and voltage stability.

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Our thanks go to Hampton-Technologies for the Lian Li HPC-600 sample.

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SPCR Articles of Related Interest:
Power Supply Fundamentals & Recommended Units
Power Distribution within Six PCs
SPCR PSU Test Rig V.4
Seasonic S12 Energy Plus 550 and 660
Seasonic M12-700
Ultra X-Pro 600
Corsair HX520 & HX620

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