Trying to turn on and off leds with tv usb

I have LED lights in the back of my tv ( ambilight ), but they stay on when the tv turns off . What I am trying to do is to turn off with the USB on the tv with a relay . I'm thinking if it is possible to use the 5v from the tv usb to power the relay so when the tv stars it gives power to the usb , starts the relay, that is connected to the "+" of the leds and makes the connection to turn on the lights. My question is i'm not a electronic guy and I don't know if it will damage the tv or the lights . should i use something else like a diode?
This is the relay i'm using
https://www.amazon.com/Songle-House...2403297&sr=8-2&keywords=songle+srd-05vdc-sl-c

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