Correct me if I am wrong. As the PSP AC Charger outputs 2000mAh for the current , it will have a "Quick Charge" effect which might not be good for the battery.
So I think a better choice is to use the PSP USB Sync and Charge cable, with the layout like that :
http://www.play-asia.com/paOS-13-71-...zh-70-kuc.html
The mini-USB can be used for connection to the pc only, but you can use another end to plug in the "DC IN" of the sony reader for charging.
And it is much cheaper than the AC Adapter!