Winmate DD-24AX DC-DC Module for Silent, Efficient Power

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For a fuller understanding of ATX power supplies, please read the reference article Power Supply Fundamentals. 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 V4.1. The testing system is a close simulation of a moderate airflow mid-tower PC optimized for low noise.

Acoustic measurements are now performed in our anechoic chamber with ambient level of 11 dBA or lower, with a PC-based spectrum analyzer comprised of SpectraPLUS software with ACO Pacific microphone and M-Audio digital audio interfaces. In this review. no acoustic testing was necessary; the product under review is silent.

The usual practice of putting the PSU in the airflow path of the heat generated by the "components" in the simulated PC case had to be abandoned for this PSU test. The DC/DC converter was plugged into the PSU tester as shown below, and the power adapter was placed on the floor.

Winmate DD-24AX V220-2 ready for testing.

Testing a DC/DC converter is not like testing a standard ATX12V power supply. It is only half of the power supply, the other half being the AC/DC power adapter used with the converter. Changing the power adapter changes the end results.

Hence, testing was done twice, with two different AC/DC adapters. One was a no-name 24VDC 180W unit supplied by Electrodacus for use in this review. It was simply the only unit he had on hand at the time, not an item offered, sold or recommended. The second is a 120W FSP unit that happened to be in the lab, model FSP120-AAB. The FSP Group web site did not have complete specifications but the number of approvals and certifications on the unit are evidence of higher quality. A web search turned up this model (and slight variants with different output plugs) priced at $30~55, including some items described as "refurbished".

Keep in mind that if you want to achieve the maximum power output capability of the Winmate DD-24AX, the power adapter must supply at least 150W output, preferably higher, to allow some headroom. The Windmate will lose 12% of the input power — 88% efficiency, remember? Hence, in theory, the 120W FSP120-AAB is safe only for ~106W output from the Winmate.

This is the AC/DC adapter provided by Electrodacus for use during our testing: Rated for 24V, 7.5A output (180W), with 100~240VAC, max, 2.9A input. Electrodacus was not confident of its quality; it was simply the only adapter he had available at the time.

This is a 19VDC 6.32A (120W) adapter from FSP Group which happened to be in the SPCR lab. Its quality is assuredly better than the adapter above.

AC/DC Adapter Specifications
Generic 24VDC 180W
90~264 VAC, 47~63 Hz
100~240 VAC, 50/60 Hz
19VDC, 6.32A
24VDC, 7.5A
Temperature range
Operating: 0 ~40°C
Storage: 20~60°C
Humidity range
Operating 20% ~ 80% RH
Strorage 10% ~ 90% RH
> 86%

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