In addition, in low or no-load situations the PWM (Pulse Width Modulation) used to regulate voltage at the inverter stage will be at a low duty cycle and create a “spikey” output profile which is more prone to causing vibration in coils, and the transformer itself will tend to vibrate as well. The no-load frequency is often low enough to be within the human hearing range.
The internal switching frequency of an SMPS is typically low when unloaded and increases with a load (up to a certain point depending on the design). Most modern AC adapters are switched-mode power supplies. The varying magnetic fields generated by these components can cause them to physically vibrate at high frequency, resulting in a high-pitched noise. These components use electromagnetism to convert AC main power to low-voltage DC power. Most power conversion devices contains coils, such as transformers or inductors. SuperUser contributors DragonLord and Daniel R Hicks have the answer for us. Why do some AC adapters and power supplies make a whining noise? The Answer Why do some AC adapters and power supplies make this whining noise? Why do some not make this noise? Is there anything that I can do to suppress it? This happens most often when they are not connected to a device or otherwise in use, and stop making noise when I connect a device that is not fully charged. However, I often hear a whining noise from some of these power supplies. I have many different AC adapters and power supplies for a variety of devices, ranging from small 5V/1A USB chargers to laptop power adapters and desktop PSUs. SuperUser reader Rishat Muhametshin wants to know why some of his AC adapters and power supplies make a whining noise:
0 kommentar(er)
