Tracing family of charles johnson (johannson) b 1799 - Helsingborg

[David Johnson]

Attempting to trace parents of Charles Johnson (or possibly JOHANNSON) born in Helsingborg 1799.  Died in Australia 28 May 1875.  I have Australian Death Certificate details but there is limited detail. Parents are not listed nor his actual date of Birth.  Information from another genealogy site relating to his wife indicates both surnames - JOHNSON and JOHANNSON.  From what resources I have indicate that the family traces back to Scotland and a Robert Johnson (B. 1724) left Scotland after the Jacobite Rebellion of 1745/46 failed.  Robert was apparently a supporter of Bonnie Prince Charles and as such under threat of execution by the English Crown and fled to Sweden I understand during 1745/46. 
Trying to trace family history from either 1745/46 of backtrack from Charles Johnson - if in fact there is a link.  Name may have changed from the English Johnson to Swedish Johannson - do not know.
Charles was a seaman and arrived in Australia in 1817 as far as the recorded details go (if accurate). If correct this would have made him a very early Swedish citizen to arrive in Australia.
Would appreciate any information from the group if you have searched previously for this family name.
Thank you.
David Johnson