One of the basic measures of any ATX power supply is the unit’s overall physical weight. This may seem rather simplistic but it generally holds that more industrial grade components and larger heatsinks equal a better PSU. The following graph illustrates how the Zalman ZM600-HP PSU compares to some other popular power supplies.
(click to enlarge)
The overall size of the ZM600-HP is typical for a 600W PSU and the depth of the chassis is slightly longer (165mm) than a standard, low-power ATX PSU (140mm).
DC Output Voltage Load Regulation
To simulate real world and maximum loading conditions, the ZM600-HP PSU was connected to the load tester, supplied with 115 VAC, and allowed to burn-in for 24 hours before voltage readings were taken. In this test we are interested in seeing how well a PSU can maintain the various output voltages while operating under different loads. The DC output voltages were measured with a FLUKE digital multimeter.
The new ATX12V V2.2 tolerance for voltages states how much each output (rail) is allowed to fluctuate and has tighter tolerances for the +12V outputs.
The following table lists the DC voltage results at different loads for the ZM600-HP PSU while operating on 115 VAC, 60 Hz.
The Zalman PSU produced excellent voltage regulation on all of the outputs across a broad range of loads; even when delivering up to 600 watts of DC power. All major outputs stayed within Â±3% and the +12V rails were particularly strong, which is very good!
AC Ripple (electrical noise) on DC Outputs
The amount of AC ripple present on the outputs was checked using an oscilloscope. This AC component may be present in the KHz range where most switching power supplies operate or it may be more prevalent at the 60 Hz line frequency. I adjusted the O-scope time base to look for AC ripple at both low and high frequencies.
The new ATX12V V2.2 specification for DC output noise/ripple is defined in the ATX12V Power Supply Design Guide.
Ideally we would like to see no AC noise on the DC outputs — the cleaner the better! But in reality there will always be some present. I measured the amplitude of the AC signal (in millivolts, peak-to-peak) to see how well the power supply complied with the ATX standard. The following table lists the ripple/noise results during all of the load tests for the seven main output voltages of interest.
The ZM600-HP power supply exhibited very good AC ripple suppression across the entire load range. Of course as the load increased, so did the magnitude of the AC ripple, but that’s normal. All values stayed within the recommended limits, even at the maximum rated output — again, very good!