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 ?
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 ?
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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.
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.
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
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.
More likely it is a fixed frequency pwm-controlled hard switching bridge type.
Then the noise is presumably subharmic oscillation, i.e. loop instability.
It may be more correct to call it 'skip-mode', cant remember...
In an under-loaded SMPS the voltage reaches set output value and the controller turns the switch off b/c it has now reached the desired voltage. With the switch off and a light load (or none at all) the output voltage still drops and suddenly the controller starts switching again. This ON-OFF switching is always at a lower frequency than the switch frequency, and very often in the audible band.
When overloaded the current limit usually kicks in, and shut the switch off. This may also produce an ON-OFF skip mode I guess, but usually skip mode is entered when the SMPS is under loaded.
In an under-loaded SMPS the voltage reaches set output value and the controller turns the switch off b/c it has now reached the desired voltage. With the switch off and a light load (or none at all) the output voltage still drops and suddenly the controller starts switching again. This ON-OFF switching is always at a lower frequency than the switch frequency, and very often in the audible band.
When overloaded the current limit usually kicks in, and shut the switch off. This may also produce an ON-OFF skip mode I guess, but usually skip mode is entered when the SMPS is under loaded.
I looked at the output of a smps I bought recently.
With a 3A load connected 24Vdc into 8r01 I could see the charging spikes ocurring on "up" side of the output ripple and I could see the clean "down" side.
The ripple frequency is very close to 50Hz.
The charging spikes on the loaded output are enormous. and this is after the filter that is supposed to make for quiet operation.
The plastic case must be pretty terrible for emi attenuation !!!
With a 3A load connected 24Vdc into 8r01 I could see the charging spikes ocurring on "up" side of the output ripple and I could see the clean "down" side.
The ripple frequency is very close to 50Hz.
The charging spikes on the loaded output are enormous. and this is after the filter that is supposed to make for quiet operation.
The plastic case must be pretty terrible for emi attenuation !!!
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