The flyback SMPS output diode reverse voltage is very high
The flyback SMPS power is about 20W,output voltage is 12V,input power is 220V,50HZ.SMPS Switching IC is top253PN.When starting on,there are about 12cycles high voltage(over 200V) on 12V rectifier diode(ES2D:max reverse voltage is 200V).Whether these high voltage will destroy the diode?And why will it occur?Thank you.
Comments
I want to know what cause the spike and how to remove it.I test another different 5 PCB,no such high voltage.Only this PCB has the problem.
Thank you!
During the start up, the flyback actually operates on CCM mode, since the output is almost zero and no volatge to demagnetizing the transformer. The CCM operation results in worse reverse recovery issue than DCM mode, and thus the voltage stess on the diode could be higher. that is why I suggest using schottky diode. As you know, schottky didoe has no reverse recovery issue. But It is hard for me to know the exact root cause of the different results of these 6 boards.
regards
Today I compare the two PBA start up(you answer is very very right):one is CCM mode(has problem),anther is DCM(no problem).But I do not know the diffrence.Can I change it to DCM mode,so that the problem will be solved also?Thank you!
I do not think thi problem can be fixed, a lot of parts and parameters affect the start up process.
Regards
Thank you for your answer,I want to improve it,what can I do?
Try longer soft start time, and hopefully the problem can be improved.
Regards
Can you tell me the detailed way?
For your question, PLS contact with diode vendor. But I do not think you can get any guarantee from vender. Actually you can solve this problem with schottky diode. PLS try to find a 200V or 150V schokky diode.
Regards