U2713HM connect problem with HDMI to Dell Vostro

Hello,

My U2713HM connect well with Dell Precision through display port. Then when I connected U2713HM by HDMI from my Dell vostro, it was not work and the screen turned to saving power mode. I checked windows display setting and it showed display 2 U2713HM but it said "Display 2 isn't active". How can I solve this problem? Thanks in advance.