Difference between Put someone in charge and Put someone on a charge

put someone in charge—cause a person to have supervision or control of smth.:

• The day when the editor put me in charge of a department was an important mile post.

put someone on a charge —(legal) accuse a person of a particular offence:

• Patrick trembles with fear and relief when he thinks of Mr. Fergusson who first put him on a charge.

See also: take charge of someone / take someone in charge.