Gradual increase of voltage on 12V mains adaptor

[zed]

Hi, I hope you can help with something I'd like to make.

I'd like a 12v DC adaptor (like this for example: http://www.maplin.co.uk/Module.aspx?ModuleNo=46107 ) to automatically gradually increase when it is powered on from around 3 volts upto its operating rate of 12 volts over a set period of time (a couple of minutes?)

Is this do-able?

Any pointers greatly appreciated, thanks.