Inductor noise in switching power supply

[CJ]

I have a Buck regulator switching around 1MHz. The load current
sometimes pulses up and down at a few hundred HZ and this causes an
audible buzz coming from the inductor.

What really causes the inductor to buzz? Does the wire move and bang
against the core when the current thru the inductor goes up and down?

The inductor is shielded so I can't actually see the windings. Are
there any ways to eliminate this buzzing noise?

Thanks,
CJ

 

[Uwe Bonnes]

I have a Buck regulator switching around 1MHz. The load current
sometimes pulses up and down at a few hundred HZ and this causes an
audible buzz coming from the inductor.

What really causes the inductor to buzz? Does the wire move and bang
against the core when the current thru the inductor goes up and down?

The inductor is shielded so I can't actually see the windings. Are
there any ways to eliminate this buzzing noise?

Rethink the compensation of your circuit. If you don't have a oscillating
load, it seems the feedback loop of the regulator is unstable for your
load. Another idea might be that you have light load and the switcher goes
into tickle mode. You give to few hints to help you more exact...

 

[colin]

I have a Buck regulator switching around 1MHz. The load current
sometimes pulses up and down at a few hundred HZ and this causes an
audible buzz coming from the inductor.

What really causes the inductor to buzz? Does the wire move and bang
against the core when the current thru the inductor goes up and down?

The inductor is shielded so I can't actually see the windings. Are
there any ways to eliminate this buzzing noise?

the noise is cuased by the magnetic atraction
cuasing the magnetic materials to flex,
it doesnt help if theres any loosenes.

this problem usualy only becomes audible if the duty cycles
varies to extreme, where the switching frequency effectivly drops
as it misses some cycles at 0% or 100% duty cycle.

hysteretic types can be more noisy for this reason
under non fixed load conditions.

Colin =^.^=