LNK304 audible noise analysis

[dpj]

I have built a non isolated power supply unit using PI chip LNK304. The supply is emitting a continuous audible noise. I want to analyze and find out the culprit.
Can some one guide where I should start my search?

I suspect inductor..but is it possible that flywheel diode create a noise?
Link Switch can generate noise?

 

[dougy83]

It's generally the inductor that makes the noise. You can cover the inductor in glue, resin or varnish (but not one that affects the wire's coating) to stop the windings and core moving.

If the feedback capacitor or feedback resistors are too small, they may give rise to audible noise in the inductor too as the device will jump from on to off at an audible frequency.

 

[crutschow]

I agree with dougy83, the only thing likely to generate noise is the inductor.

What type of inductor are you using?

 

[dpj]

I am using TDK TSL0709 series drum inductor 1 mH.
I do not doubt this component thats why asked whether diode or LNK304 itself can generate audible noise.

Ind. datasheet www.tdk.co.jp/tefe02/e532_tsl0709.pdf