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

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DD-24AX V220-2
130W DC/DC power supply
Sample Supplier

This 130W computer power supply is not a standard ATX12V power supply. It is a DC/DC converter, much like the picoPSU, requiring a source of DC current to generate the various voltage lines required for a computer. The nominal required input is 24VDC, which must be provided by an AC/DC adapter. The only use for a DC/DC converter like this a few years ago would have been in a digital kiosk, signage, security, cash register or other such limited, industrial embedded computing applications. Today, with the diminishing power requirements of computing components, this modest DC/DC adapter can actually power a full-function desktop, media / file server, office computers or even a light gaming machine.

The maker of the DD-24AX 130W DC-to-DC power module is Winmate, a Taiwan-based company whose core business is developing LCD application products, digital signage solutions, and embedded systems integrating GPS, wireless, and touch screen technology. The company does not sell direct to consumers. An engineer in Canada with an interest in such power products for himself obtained a deal for 600 DD-24AX units in order to go into business offering it in the SPCR forums and on eBay for silence-focused DIY PC enthusiasts all over the world. His forum ID is Electrodacus. All of the specifications about the DD-24AX V220-2 came from Electrodacus, but they originated from Winmate.

The 130W DC/DC converter atop a 180W AC/24VDC adapter supplied by Electrodacus for use in this review.


Why not stay with the tried-and-true ATX12V PSU? Here's a summary of the advantages of using a DC/DC converter with an AC/DC adapter over a conventional ATX12V power supply. A key point is that the advantages are greatest at lower power.

High Efficiency at Lower Power

Like all machinery, every power supply achieves best efficiency over a certain range, usually at 40~80% of full capacity. With most ATX12V power supplies rated at a minimum of ~400W these days, there's not much hope for them to achieve their maximum efficiency with systems that pull under 50W at idle and barely 100W at maximum load. The majority of mini-ITX PCs fall into this category as do many efficiency-optimized micro-ATX systems designed for use as media PCs or file servers.

Even modestly priced DC/DC converters offer very high efficiency, often 90% or higher, and AC/DC adapters of 60W~150W that achieve 90% efficiency are not uncommon. Such a combination for a PC with modest power demand can often draw less power than conventional ATX12V PSUs, even those rated for 80 Plus. Why? Because the vast majority of high effiency ATX12V PSUs are rated for 500W or higher; at 40W, many struggle to make 70% efficiency and barely reach 75% at 65W. In contrast, an efficient DC/DC converter can be used with an efficient AC/DC adapter of just the right power rating to achieve ~80% and better efficiency throughout the actual power range of the low power computer.

Electrodocus offers a comparison of AC power consumption between an SFX PSU and the DD-24AX with a 150W adapter, both driving the same low-power optimized quad-core Intel Q8400S system. The comparison favors the DD-24AX by 8~13W depending on mode. More on this later in our own testing and analysis.

Small Size for Greater Flexibility

A low power DC/DC converter is usually quite small, and because it generates little heat, there is a lot of flexibility in installation. It will go into the smallest of microATX cases, and even into very small mini-ITX cases. This is a big advantage as PC users continue to downsize.

Less Heat, No Noise

The icing on the cake with the converter + adapter approach is lower heat in the PC and zero noise from the power adapter. Half of the heat generated in the AC-to-DC converstion is outside, in the external adapter. The DC/DC converters usually don't require a fan for cooling, and most AC/DC adapters are also passively cooled.

The cost of the converter + adapter approach is quite favorable for low power, say under 120W, but as the power requirement goes up, the price gets considerably higher. A good 200W AC/DC adapter is often quite pricey, perhaps double that of a good 400W ATX12V PSU. At >150W loads, the cooling requirement becomes greater, and if an additional fan must be used to cool the DC/DC converter, then the advantage pass quickly to the standard ATX12V PSU.


The DC/DC board came in a small, well-packed, plain cardboard carton with standard shipping accessories. The black cable is an input extension.

Winmate DD-24AX V220-2 General Specifications
ITEM Our Comment
Nominal Input: 24VDC 18V~28V allowable, 8A~5A
Total Output: 130WDC
Enough for lots of systems
Ripple And Noise
5V: Less than 100mV
3.3V: Less than 66mV
12V: 120mV
-12V: 200mV
Seems high for some lines. Normal ATX12V requirements are 50mV for the 5V & 3.3V lines, and 120mV for the 12V line.
Line Regulation
Less than 2.5% at rated load with 10% change in input voltage
Pretty good.
Protection from short circuits (SCP) and over current (OCP)
Good, but not quite as complete as some ATX12V power supplies.
Efficiency: 88% Excellent... but at what loads?
RoHS Compliant. (Lead free)
Required for sale in the EU.
Weight: 114 grams
Size: 154 x 45 x 25.6 mm
It's very small and light.

Winmate DD-24AX V220-2 Output Specifications
DC Input
18V~28V, 8A~5A
DC Output
Operating conditions: 0~50°C, 0 to 10,000' altitude, 10~90% humidity

The 0~50°C operating temperature is a pleasant surprise. Fanless operation should be perfectly fine as long as the converter is not being red-lined and there's a touch of airflow.

12V LINE CAPACITY: In case it's not clear, note that the maxmimum output spec of the 12VDC line is 120W, exactly the same as the maximum combined output for all the lines with the exception of the 5Vsb line. This means that the 5V, 3.3V and -12V lines all are obtained via DC/DC conversion from the 12VDC line. At idle or low loads, none of this is particularly important, but it might be good to know when the PC is highly stressed. Most of the demand will be on the 12VDC line. So if there is a lot of current demand on the 5V and 3.3V lines, there will be less current available for the CPU or GPU, the big current demanders on the 12V line.

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