USB Powers Up daily at fixed time (5:35, 5:40, ...)

I have question why the Philips Smart TV (PFL5507) spontaneously powers-on the USB-bus daily at certain fixed timings. Is it to check if there is a USB stick present with Firmware on it ???

My problem with it is as follows:

I have connected a Raspberry PI device via USB. This device has XBMC installed.
Every morning at 5:35 the USB powers on, the Raspberry PI starts booting and the XBMC activates, then HDMI signal wakes up the TV with Image + Sound .... ==> Problem: My Sleep is disturbed !

I can't find where to control the power-up of the USB,

Is there anyone who knows ?

Very much Appreciated !

PS. Besides, The Rapberry PI with XBIAN as XBMC is very working very well ! Even the Remote Control works excellent via EasyLink ! I can recommend this to anyone.