Noise on start (TOP223)
Hello Friends!I'm designing a 18W SMPS with TOP223 with universal input and +5 V/14V and one isolated output +5 V.I used a transformer EE25 with 82 turns on the primary and 1000uH of inductance.The source works and works normally regulated. But when I turn on the power, I hear a small noise. This noise comes not from the input capacitors, since they have a NTC for starter.
I'm afraid this noise is stressing the components and may cause a burning later.
I emphasize that the noise only happens when I turn on the power, after it does not emit any noise.
Would this normal? The primary inductance is too high?
Thank you!
Comments
Hello Friend!I downloaded the inductance of the transformer and the noise essentially gone. You are right in their considerations.My transformer was:- Primary: 82 voltas/26 AWG/1mH inductance- Secondary: 13 turns / 22 AWGReel E24/25.
The inductance decreases by half and improved, but had loss adjustment, and recalculated all the transformer using the spreadsheet found now.It looked like this:- Primary: 92 voltas/28 AWG / 0.742 mH inductance- Secondary: 14 turns / 20 AWGReel E24/25.
I asked my supplier and samples will be tested.What do you think?
I can't comment on your design without your design files and power supply specifications.
-The Traveler
Common culprits of power supply noise are going to be magnetic components and ceramic capacitors. High peak flux densities during startup can cause noise with unvarnished windings in the transformer and ceramic capacitors used in the clamp can cause high frequency noise during periods of high dV/dt stress.
Can you please reply with the following informaiton:
-PI Expert Design Files
-PDF of your actual circuit schematic
-PDF of your PCB layout.
-If your transformer is different than described in the PI Expert files, please attach the documentation for that as well.
-The Traveler