Testing – DC Output Voltage Load Regulation
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To
simulate real world operation, each power supply was connected to the 300 watt
load tester, supplied with 115 VAC, and allowed to burn-in for at least 24 hrs
before voltage readings were taken. In
this test we are interested in seeing how well a PSU can maintain the various
output voltages while under a moderately heavy load. The DC output voltages were measured with a
FLUKE digital multimeter at the ATX connector.
The ambient air temperature during testing was 24ºC (75ºF) +/- 1ºC.
The
ATX tolerance for voltages states how much each output (rail) is allowed to
fluctuate. Most power supply
manufactures try to hold tolerances tighter than this minimum specification,
typically 5% instead of 10% and 1~3% instead of 5%.
The
following table lists the DC voltage regulation results for our 300 watt load
tests. Values in red are out of
tolerance.
As
you can see, nearly all of the DC outputs were held within the ATX
specification while operating under a 300 watt combined load. The only two exceptions were the Enermax and
Raidmax units. Even these were on the
less critical -5V and -12V outputs and were only off by 0.05V. All of the other power supplies exhibited
excellent output regulation.
Of
particular interest are the three main power rails (+3.3V, +5V and +12V) and
the 5VSB line. Maintaining these outputs
at optimum levels is important to the reliable operation of any PC. If you push components (overclock/over-volt)
then they become even more critical.