Acoustic Noise L6599

[IStel]

I absolutely do not understand under what conditions and for what reason sometimes during operation of the LLC converter, the power transformer emits audible high-frequency acoustic noise. Some instances work fine, but some make a good audible noise. What is the reason for this noise and how to avoid it?

[jayanth]

Normally As per my knowledge If there is a air gap between windings or between turns, transformers tend to make hum sound.

[Ozone]

Resonance of mechanical components with spectral components of the converter's frequency.

Most susceptible components are coils, with magnetic energy transfer and larger dimensions capable of mechanical oscillations.

Ever experienced clamp-mounted water pipes hum at certain pressure/flow rate ?

Usually some filling compound (epoxy, PU filler) would stop it.