Cause of buzzing or humming noise from AC/DC Power Adapters — Desktop & Wall-Mount｜Why expert assistance is necessary

In fact, many AC/DC Power Adapters — Desktop & Wall-Mount that use switching power supply systems tend to generate a certain amount of noise due to their structure. Simple countermeasures like "adding a different load" or "changing the wiring" are often ineffective, making it essential to identify the root cause from the design stage. This article introduces the main mechanisms behind whining and buzzing noises in AC adapters and the approaches necessary to fundamentally eliminate them.

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

[Introduction] Are You Troubled by Noises Coming from Your AC Adapter?

Have you ever heard a high-pitched "buzzing" or a low "humming" sound from an AC adapter, such as one for a laptop or smartphone charger? This is sometimes called the mosquito noise of an AC adapter. These sounds can be disturbing enough to disrupt sleep or cause concern as a possible sign of malfunction.

This article explains the main causes of abnormal sounds (noise) from AC adapters, as well as measures and safety concerns. For basic information about the internal structure and working principles of AC adapters, please refer to "What Is an AC Adapter?" Here, we focus specifically on sound-related points.

[1. Why Does an AC Adapter Make Buzzing or Humming Noises?]

1-1. Coil Whine

Many AC adapters use a switching power supply system, which converts electricity efficiently using high-frequency signals. Due to the nature of this method, large magnetic field changes occur in the coils and transformers, causing fine vibrations that result in a "buzzing" sound. This phenomenon is commonly referred to as "coil whine."

1-2. Vibration Caused by Circuit Design and Component Selection

Even when using the same switching system, the design and selection of components such as coils, capacitors, and circuit board layout significantly impact the mechanism and volume of noise. If optimization is insufficient due to product quality, cost constraints, or size limitations, the resulting noise can become noticeable and bothersome to end users.

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

In many cases, a combination of factors contributes to the noise, including variations in load current and operation modes, high-frequency noise returning from the connected device, and interference with wiring or grounding. These influences interact in complex ways, so identifying the root cause often requires professional approaches such as actual equipment testing and circuit simulation.

[2. Are Buzzing or Humming Noises Dangerous? Effects on Safety and Reliability]

2-1. Noise Does Not Necessarily Indicate Danger

Minor coil whine and hum produced during normal operation of a switching power supply, especially under specific loads, are not necessarily signs of malfunction. As long as certain standards and quality requirements are met, these vibrations usually do not affect product lifespan.

2-2. Excessive Noise Increases User Concern

On the other hand, excessive noise or fluctuating frequencies that become irritating may increase the risk of customer complaints. The following solutions may help address this issue.

[3. Why “Simple Fixes” Are Not Enough]

3-1. Structural Noise Is Difficult to Eliminate Completely

While switching AC adapters offer advantages like high efficiency and compact size, their fast internal switching inevitably generates noise. Stopgap solutions such as changing wiring or load conditions cannot fully eliminate the root vibrations.

3-2. Redesigning Circuit Constants and Layout Optimization Is Essential

Without thoroughly reviewing component values, circuit board layout design, and implementation methods, there is a limit to how much noise can be reduced. Especially when multiple factors are involved, you need to reconfigure component values and parameters after careful simulation and measurement.

3-3. System-Level Testing with Connected Devices Is Crucial

Noise problems may not stem solely from the AC adapter, but also from interactions with the connected device. In devices with multiple chips and functions, interference across frequency bands can cause unexpected noise. Therefore, comprehensive testing using the actual system is essential to identify complete solutions.

[Summary][Consult Unifive About Noise Problems]

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