Large numbers of tantalum capacitors and aluminum electrolytic capacitors have conventionally been used in electronic equipment, but are now being replaced with ceramic capacitors for reasons such as product downsizing and reliability issues.
As electronic equipment becomes more multifunctional and quiet, the “acoustic noise” caused by ceramic capacitors, which was not formerly noticeable, has become a major design issue in the power circuits of various devices, such as laptop computers, mobile phones (smart phones), DSCs, and flat-screen TVs.
Acoustic noise caused by the capacitors used in the battery line can be an issue for a laptop computer.
When the operating mode is changed, such as sleep mode or camera start-up, the internal operation of the laptop computer changes, so the level of the acoustic noise and how it is heard also changes, based on the operating mode.
In this report, we introduce the mechanisms by which capacitors produce acoustic noise and methods for evaluating and suppressing acoustic noise in the battery line of a laptop computer.