SMPS failure about TOP244YN, PC817 in fb
Hi.
i have a SMPS design where i use TOP244YN switch. Recently one SMPS was returned from field where the TOP244YN IC was short. PC817 IC and1N4148 diode in feedback were also damaged.
Upon replacing the faulty components, it started working.
But i am unable to understand what might have caused this failure when there are overvoltage and overcurrent protections present in the lines? Is it some problem with transformer and its leakages?
Can anyone please explain what could be the cause?
Thanks.
srj
Comments
Thanks a lot for your reply.
Apperantly there was no damage to any other instruments that were on the same power supply.
Although this does not say anything really. It is just the argument that field guys put up. I don't even know if this was the only instrument that was ON at the time of lightening.
I have attached schematic of my power supply and mentioned the components which were damaged.
There is quite a good protection at the initial stage.
And the poer supply unit also complies to EN 61326 standard of low power devices of CE certification.
Maybe you would find something in schematic which might have gone unnoticed.
regards,
srj
The schematic looks very good to me. The only thing I do not like is the 200V zenner for the snubber, since the voltage stress can be easily be higher than 600V.
I guess the power supply have been mass production for about 4 years, so I think it is a reliable design. Maybe really cause dby the line surge. I am sorry not help a lot.
Regards
It is hard to know the root cause of this failure. But I do not think the root cause is the transformer. Millions of TOPSWITCH are used in all kinds of applications, and all have transformers.
I guess the failure maybe caused by the lighting at customer side. The extremely line voltage resulted from lighting caused the failure of these parts. If it was really caused by the lighting, It is very possible that the TOPSWITCH damged first, since it was connected to the line input directly.
Regards