Psp comes on screen doesn't light it then goes off!!!?

when i turn it on the green light comes on but the screen doesn't light up or do anything then after about
60 seconds it switches off have tried replacing battery still no good, don't know if my son did something he took the battery out when it said it was downloading but it wasn't on net it only had a game in it, we would appreciate any help. Psp is just over a year old but its not a slim one.