What issues are caused by noise?

We propose the following as a countermeasure against issues caused by noise..

About noise suppression of AC adapters

How can UNIFIVE disable AC adapter radio noise for customers? We have been asked a lot of questions.

Even concerning noise, there are various regulatory requirements that much be taken into consideration such as the effects of communication system noise and acoustic system noise.

We would like to mention an example of a special kind of acoustic system noise (beat noise).

Beat noise is noise generated in an oblique striped pattern when receiving an image from analog television signals (such as waving noise, disturbing sine wave, etc.).

In other words, when connecting more than two devices, such as a large speaker or a guitar amp on the stage of a concert, before the sound can be made (at the time of silence), howling such as howling from the speaker or a kind of noise like tinnitus can be produced.

In such an event, the noise generated from the power source flows to the speaker, and the sound of the noise is offensive to the ear. Normally, it is thought that the ground (GND) of the AC adapter and the ground of the signal connection form a loop connection. Countermeasures against this can cause insufficient gain and interference between carrier waves is often difficult to deal with.

UNIFIVE is currently developing custom solutions for customers related to audio equipment, and is adopting the following design improvements to solve this problem.

①  Separate the ground connection between the primary side and the secondary side of the AC adapter.

② Ferrite beads are added to the internal ceramic capacitor of the AC adapter.

③ Devices connected to the pin of the AC adapter internal transformer.

For the connection to the transformer core with a connection lead line (black), the connection to the transformer was changed from pin 1 to pin 2.

With the above improvements, we also compared and measured waveform diagrams.

In response to this countermeasure, when the level (peak value) is low with a waveform close to the SIN wave, the low frequency audio noise decreases.

The output specification with the measures as described above is 13V/4A. This is the item used for a guitar amp.

UNIFIVE has plenty of experience with customers relating to audio equipment. Therefore, the type of AC adapter varies according to customer specifications, as well as according to the design philosophy of sound IEC 60065 safety standards, the improvement of acoustic noise 6–12 dB, parts selection used to realize long lifespan, the outlet of electrostatic discharge, and UNIFIVE’s customs designs, such as responding to demands for metal pin corrosion, and improving beat noise, etc.

Acoustic equipment, both portable and electronic guitars and amplifiers, string and percussion instruments, and pianos, and other audio-related equipment are being digitized. Therefore, this trend is demanding high-quality sound, and the value-added function of products is also increasing. This also pertains to the design of the power supplies. We have analyzed these inquiries because we want to match the diversification of needs which is increasing year by year. Especially for Japan’s electrical products that require high quality. Our company continues to evolve and we are pursuing every day to how to best answer our customers’ requests.

From now on, we will adhere to the new technical standards, such as IEC 62368. In addition, due to the Tokyo Olympic Games being held in 2020, the variety of possible situations for UNIFIVE’s AC adapter use is diverse, with possible implementation in infrastructure development (of stations, ward offices, libraries, hospitals, etc.) and its related installation of sound equipment, including IoT-related equipment (surveillance audio equipment, etc.), as well as that of other industries (robots, voice advertisements, signboards, etc.) Therefore, our lineup will be vital and will bring a richness to peoples’ lives.

UNIFIVE will thoroughly assess what we can respond to your product requirements, so if you have any request, we would be pleased to hear from you.