Antec CP-850: Unique PSU with Top Performance

TEST RESULTS

Ambient conditions during testing were 24°C and 11 dBA. AC input was 118~122V, 60Hz. .

ANALYSIS

1. EFFICIENCY — This is a measure of AC-to-DC conversion efficiency. The ATX12V v2.2 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. It allows reduced cooling airflow, which translates to lower noise.

Our CP-850 sample clearly met 80 Plus requirements. The 80% efficiency point was reached before 90W, which is low and very good for a PSU rated for 850W; 80 Plus only calls for 80% efficiency at 20% of capacity load, or 170W in this case. A broad efficiency peak of 83~85% was reached between 200W~500W, above which it fell off a bit. Our sample's failure to maintain 80% efficiency at full load is by now a well-known consequence of SPCR's torture chamber hot box, which subjects the PSU to an extreme level of heat. In contrast, 80 Plus tests PSUs in normal room temperature, under which conditions the 80 Plus tested sample reached 80.91% efficiency at full load.

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 maintained within ±5%.

All the output lines were rock solid stable under all load conditions. The biggest variation was +0.1V on the 12V line at very load load. This represents +0.8%. The virtual absence of any drop in voltage below target at full load on all three main DC lines was most impressive.

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 100s of kHz). 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 was vanishingly low on all the lines. At low loads at the start of testing, the 12V ripple actually did not often rise above 10 mV, and the lower voltage output lines stayed well in single digits. Only at extreme loads did some peaks reach above 20 mV on the 12V line. The maximum peaks seen for the +5V and +3.3V lines were in the teens. This is exceptionally low ripple noise.

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 a smaller, cheaper UPS backup; they are priced according to their VA (volt-ampere) rating. PF on our sample was close to the theroretical perfection of 1.0 at virtually all loads.

5. LOW LOAD PERFORMANCE is significant mainly to minimize energy waste and with system that demand very low power; the latter can cause some PSUs not to start. Standby power was very low with 0.4W draw. The unit powered up with no load, drawing 9.4W, suggesting it has a built-in loader to prevent low loads from causing trouble.

6. CROSSLOAD TEST - Basically the load on the 12V line was maximized while the load on all the other lines was minimized. Voltage regulation on all the lines remained excellent, and ripple stayed extremely low. There were no other changes.

7. 240 VAC INPUT - The power supply was set to 700W load with 120VAC through the hefty variac in the lab. The variac was then dialed 10V lower every 5 minutes. This is to check the stability of the PSU under brownout conditions where the AC line voltage drops from the 110~120V norm. Most power supplies achieve higher efficiency with higher AC input voltage. SPCR's lab is equipped with a 240VAC line, which was used to check power supply efficiency for the benefit of those who live in 240VAC mains regions.

There were no surprises here. Our sample's efficiency improved by nearly 3% at the higher VAC, and dropped a little less than 1% for each 10VAC drop. Voltage regulation and ripple were unchanged.