Capacitor and diode curcit for ac to dc voltage

[nokia8650]

http://img42.imageshack.us/img42/2461/49889005.th.jpg [Broken]

My question is, why does the dc voltage vary with time in this way? Ply it is something to do with the diode allowing current to flow when it has 0.7V or more across it, allowing the capacitor to charge, and when the voltage drops to below this, the capacitor discharges, however could someone please provide a more comprehensive explanation?

Thanks a lot in advance.

 

[berkeman]

http://img42.imageshack.us/img42/2461/49889005.th.jpg [Broken]

My question is, why does the dc voltage vary with time in this way? Ply it is something to do with the diode allowing current to flow when it has 0.7V or more across it, allowing the capacitor to charge, and when the voltage drops to below this, the capacitor discharges, however could someone please provide a more comprehensive explanation?

Thanks a lot in advance.

Your explanation is correct. The droop between the power input part is at the RC time constant specified by the load R and the storage C.