PS3 Turns itself off

I don't think it is a problem but I was charging the controller on my playstation and I left it on for a few hours to charge it up, about 3 hours later I came back downstairs to turn the PS3 off and I found it was already off. Nobody else turned it off, I looked it up on the internet and I found that many people have had problems with there PS3 turning itself off after 5 or 10 minutes. Does the PS3 turn itself off if you don't do anything on it for a long time. Please leave a comment, because nobody every leaves my comments and I am getting annoyed with it.