Causes of buzzing and humming sounds from AC/DC Power Adapters — Desktop & Wall-Mount | Why expert resolution is necessary

In fact, many AC/DC power adapters — desktop & wall-mount — that adopt a switching power supply system tend to generate a certain level of noise due to their structure. Simple countermeasures such as "applying a different load" or "changing the wiring" are often insufficient, making it essential to investigate the root cause from the design stage. This article introduces the main mechanisms behind the buzzing and humming sounds of AC adapters, and the fundamental approaches necessary to eliminate them.

Causes and Solutions for Buzzing or Humming Sounds from AC Adapters | Is It Safe?

[Prologue] Are You Troubled by Sounds Coming from AC/DC Power Adapters — Desktop & Wall-Mount?

Do you ever hear a high-pitched “buzz” or low “hum” coming from chargers for your laptop or smartphone, like AC/DC Power Adapters — Desktop & Wall-Mount? These are often called "mosquito noises" from AC/DC Power Adapters — Desktop & Wall-Mount.
Many users find them distracting or wonder, “Is this sound a sign of a malfunction?”

This article explains the main causes, safety concerns, and countermeasures for the unusual noises (buzzing or humming) that can be heard from AC adapters. For basic information on the internal structure and mechanism of AC adapters, please refer to “What Is an AC Adapter?” Here, we focus specifically on sound-related issues.

[1. Why Do AC/DC Power Adapters — Desktop & Wall-Mount Make Buzzing or Humming Sounds?]

1-1. Coil Whine

Most AC/DC Power Adapters — Desktop & Wall-Mount use a switch-mode power supply. This method efficiently converts current using high-frequency electrical signals. Due to the nature of this method, strong changes in magnetic fields occur in coils and transformers, causing tiny vibrations that can be heard as a “buzzing” noise. This is commonly referred to as “coil whine.”

1-2. Vibration Factors from Circuit Design or Component Selection

Even when using the same switching method, the mechanism and volume of noise produced can vary greatly depending on design choices like coils, capacitors, and PCB layout. Without thorough optimization for target costs, performance, and size constraints, noticeable noise may result.

1-3. Noise from the Connected Device & Combined Factors

Changes in load current and operating modes, backflowing high-frequency noise from the connected device, wiring, and grounding issues — all these factors often interact in complex ways. Isolating the main cause typically requires professional approaches such as actual device testing and circuit simulations.

[2. Are Buzzing or Humming Sounds Dangerous? What About Safety and Reliability?]

2-1. Noise Doesn’t Necessarily Mean Danger

Minor coil whine or humming under specific loads — or mosquito sounds that occur during normal operation of switching power supplies — are not necessarily signs of failure. In most cases, if the product meets certain quality and regulatory standards, these vibrations do not impact product lifespan.

2-2. Loud Noise Can Lead to Customer Concerns

However, if the noise is loud or fluctuates in frequency in a disturbing way, it may increase the risk of product complaints from users. To address this issue, several strategies are available.

[3. Why Is It Difficult to Solve with “Quick Fixes”?]

3-1. Fundamental Noise from Structure Is Hard to Eliminate

AC/DC Power Adapters — Desktop & Wall-Mount using switching methods offer high efficiency and compact size, but high-speed switching internally inevitably creates noise. Simple methods like changing cables or loads cannot fully suppress the root cause of vibrations.

3-2. Component Recalibration and Layout Optimization Are Essential

Without reviewing components such as coils and capacitors, as well as layout and implementation methods, noise reduction has its limits. Especially when multiple factors are involved, simulations and measurements are required to recalibrate component values and parameters.

3-3. Testing with the Connected Device Is Crucial

Noise may not stem solely from the AC/DC Power Adapter — Desktop & Wall-Mount, but also from how it interacts with the connected device. Devices with multiple chips and functions may trigger unusual noise due to frequency interference. Therefore, complete solutions are difficult without combined system testing.

[Summary][Consult Unifive for Noise Issues]

If you're struggling with noises from your AC adapter or want to reduce product complaints, feel free to consult us.