How to perform case insensitive search on keyword tokenizer


I have a requirement where I need to perform case insensitive search for keyword tokenize field , If I use lowercase filter then it converts all the data into lower case that I do not want . I am using wild card query for search (I am using this for auto-complete).
I am using keyword tokenizer because When I search for "keyword-" , it should not perform lucene query and exclude the second word.

let us suppose we have two string


when I search using hello or HELLO- ,it should return both the doc but in different case.

Any idea how can I achieve this.

Best Regards,