A large current flowing out from video signal line driver is prevented whenever the video signal line is being grounded. The system includes a video signal line driver circuit transmitting video signal at pre-determined DC level, a large current prevention circuit detecting video signal line being shorted to ground and cut-off excessive current source out from video signal line driver circuit into video signal line, a start-up time enhancement circuit improving start-up time of ground detection circuit so that system start-up time is not limited by large current prevention circuit, and a switching threshold control circuit setting the switching threshold of large current prevention circuit and start-up time enhancement circuit.