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Old 21st May 2014, 01:57 AM   #1
toyer is offline toyer  Turkey
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Default transformer is buzzing

er 35/20/11 smps transformer.

12 volt to 310 volt dc 50 khz. push pull 2 primary (3+3 turns ) one secondary 112 turns.

it is buzzing. what can be the reason ?

Last edited by toyer; 21st May 2014 at 02:01 AM.
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Old 22nd May 2014, 08:37 PM   #2
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Loose wire.
Being overloaded.
The SMPS frequency is wrong and is in the audio band.
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Old 22nd May 2014, 08:58 PM   #3
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Try to change frequency...
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Old 5th June 2014, 11:48 PM   #4
toyer is offline toyer  Turkey
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Quote:
Originally Posted by nigelwright7557 View Post
Loose wire.
Being overloaded.
The SMPS frequency is wrong and is in the audio band.
with some duty cyles it is not doing any noise. but with some duty cyles it is doing noise. what do you say ? any idea?
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Old 5th June 2014, 11:52 PM   #5
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Originally Posted by toyer View Post
with some duty cyles it is not doing any noise. but with some duty cyles it is doing noise. what do you say ? any idea?
Its probably one of the reasons I suggested earlier.

I have seen SMPS transformers growl if they are over loaded too.
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Old 6th June 2014, 11:24 AM   #6
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If it's audible buzz, which this obviously is, the SMPS is probably going into burst mode. The burst frequency is low enough that it becomes intrusive. It goes into burst mode when under-loaded, so either adjust it for lower power or load it more.
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Old 6th June 2014, 06:32 PM   #7
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İm adjusting the duty with a potantiometer manually and having like more than 2 hundreds watts load. At some duty cyles starting from zero to max 80 percent it is buzzing at some points. When it is buzzing the duty is changing like 5 percent by its own without any change on potantiometer
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Old 6th June 2014, 08:56 PM   #8
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Quote:
Originally Posted by SemperFi View Post
If it's audible buzz, which this obviously is, the SMPS is probably going into burst mode. The burst frequency is low enough that it becomes intrusive. It goes into burst mode when under-loaded, so either adjust it for lower power or load it more.
Don't you mean over loaded ?
In LLC SMPS the frequency goes down as load increases.
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Old 7th June 2014, 08:57 PM   #9
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Obviously this smps is duty cycle controlled - so it cannot be LLC.
More likely it is a fixed frequency pwm-controlled hard switching bridge type.
Then the noise is presumably subharmic oscillation, i.e. loop instability.
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Old 9th June 2014, 02:35 PM   #10
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Originally Posted by voltwide View Post
Obviously this smps is duty cycle controlled - so it cannot be LLC.
More likely it is a fixed frequency pwm-controlled hard switching bridge type.
Then the noise is presumably subharmic oscillation, i.e. loop instability.
Hoş to get rid of the subharmonic ossilationas?
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