Led strip backlight Problem

Im designing a circuit with capacitors to make the light turn of a few seconds after tv goes into standby. The usb from the tv is the one connected to the transistor and the capacito Problem is when i turn off the tv with the remote the led strip is still lit but its very dim "almost like a pwm". looks like the led strip takes power from the tv. How do i go around avoiding the ledstrip from taking power from the tv. another big issue is that the tv feeds power into the circuit from the usb when tv is turned off so it wont turn of completely.

Have you tried a resistor in parallel with the LED? I would suggest a value that gives about 1% of the normal current.