These are really great questions. First, let's make sure you're clearly distinguishing your knowledge areas. The Project Charter is an output of the Develop Project Charter process in the Integration Management knowledge area (initiating process group). Scope Management is it's own knowledge area producing, of course, the scope baseline. Similarly, the schedule baseline is created in the Time Management knowledge area. Both of these baselines are created in the planning process group.
All being said, change requests against the scope and schedule baselines involve internal monitoring, controlling, and executing of the project against those baselines. Changes in the Project Charter, although still requiring approval through the Change Control Board, are often external to the project (i.e., changes to the organization). A very common change may relate to those running the project, both as the sponsor and/or the Project Manager. Other reasons may involve changes to the EEFs/OPAs that are being used as INPUTS to the Develop Project Charter process.
If you consider the list on pg. 72 of the PMBOK (5th ed), any of those high-level items could compel a change w/in the Project Charter. Since this is a formal document of the project, it would require board approvals.
Hope that helps you, but please let me know if it doesn't!
Regards,
Eric Bartlett, PMP
Community Moderator
