Ask Lenovo Think Stasion power supply part, need the real code of IC

[bietjun]

I need to replace the IC but can not find any datasheet and can not find anybody sell it, in simply can not find anything related on it.
What can be seen is : LENOVO i1803A . it suppouse to be ic for PWM controller/ osilator. the picture is in attached file.
Please help and advice what should be done. Thanks.