Modular Supplies Hush Acoustic Noise

July 31, 2012
Quietest modular power supplies on the market

The 200-W XTA and 400-W XTB chassis in the Excelsys Xgen series exhibit a mere 37.3 dBA of acoustic noise over all load conditions (see the figure). According to the company, they’re the quietest modular power supplies on the market.

Introduced as the quietest modular power supplies available, the XTA and XTB from Excelsys specify an acoustic-noise figure of 37.3 dBA.

Both units carry UL and EN60950 second-edition certifications. Also, the 200-W XNA and 400-W XNB chassis carry UL and EN60601-1 third-edition medical approvals. All four Xgen units feature sleek dimensions, measuring 10.24 by 3.5 by 1.59 in.

Acoustic noise refers to actual physical noise. By comparison, hum from a poorly shielded component or stray radio signals appearing at a supply’s front end or outputs fall into the electrical-noise category.

If a component in the supply vibrates mechanically during operation or if the internal materials of a particular component start shaking or moving around within the component’s casing, the resulting noise is categorically acoustic.

A common source of unwanted acoustic noise, particularly noticeable in audio applications, is power-transformer noise. Winding and core vibrations are the most likely suspects. Loose windings, thin insulating lacquers, and heat are common causes for winding noise. In addition to poor quality, transformer cores can become noisy under normal, semi-unique, or erratic secondary loads.

Other causes for noise in the core include movement of the magnetic walls, shifting or rotating magnetic fields, and mechanical movement in core laminations. Reducing transformer noise is therefore pretty simple: use a quality transformer or, should one be designing a straight-through, high-power high-voltage linear supply, eliminate the transformer entirely.

Eliminating acoustic noise is important for a number of reasons. First, it’s an indication of a poor design and/or the impending failure of said design. Second, it can denigrate signal integrity in critical measurement and medical apps. Third, again in the realm of audio, noise of any kind is downright annoying to all involved.

Regardless of the model, the Xgen modular power supplies are noted for low acoustic and low electrical noise, which poises them for productive use in a bevy of applications including medical, scientific, and broadcast.

The XTA, XTB, XNA, and XNB chassis provide four user-configurable slots, each configurable with as many as eight isolated outputs from 1.5 to 58 V dc. All are fully adjustable and can be arranged in series for higher voltages or in parallel to derive higher output currents.

Other specifications include efficiencies up to 89%, individual control of each output, an auxiliary 5-V dc output, universal 85- to 264-V ac input support, and a comprehensive array of protection features including over-voltage, over-current, short circuit, and over-temperature.

The 200-W XTA and 400-W XTB Xgen chassis are available now with evaluation quantities available from stock. Pricing starts at $694 each in lots of 100 for configured XTB supplies. More specs are available at

The company also offers a plethora of design resources for the entire Xgen family, including a designers’ manual, application notes, and assessment and resolution of safety, environmental, and electromagnetic interference (EMI) issues, as well as a full listing of Halt reports, and whitepapers. All of these materials are accessible via


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