I have a problem with my switch mode power supply, smps. It creates audio sound when I power it up, especially at minimum load. As I increase the load then sound disappears and in some designs it is still there. I don't know what to do. It is a bottleneck for me. Anyone who knows what to do about it. I'm operating it at 50KHz which is well above audio frequency.
berkeman
Aug18-08, 12:45 PM
I have a problem with my switch mode power supply, smps. It creates audio sound when I power it up, especially at minimum load. As I increase the load then sound disappears and in some designs it is still there. I don't know what to do. It is a bottleneck for me. Anyone who knows what to do about it. I'm operating it at 50KHz which is well above audio frequency.
Most likely it is magnetostriction noise in your main switching magnetic component. What topology is your SMPS? What transformer/inductor are you using? The general fix/prevention is to put some epoxy material in the gap of your transformer. Who is your transformer/inductor supplier?
ElectroPhysics
Aug19-08, 07:18 AM
I'm using it in forward topology. etd49 as main transformer and etd39 with gape for output inductor.
I have measured the waveshape at the drain of mosfet. It looks like distorted when audio noise comes otherwise it is clean waveshape.
berkeman
Aug19-08, 12:27 PM
I'm using it in forward topology. etd49 as main transformer and etd39 with gape for output inductor.
I have measured the waveshape at the drain of mosfet. It looks like distorted when audio noise comes otherwise it is clean waveshape.
Can you find the source of the distortion/noise? Maybe a feedback stability problem?