Automatic gain control circuit in video signal processing device

An automatic gain control circuit for receiving a video signal including a black level which indicates a minimum brightness of a video image and a white level which indicates a maximum brightness of the video image more than one time within one horizontal period and automatically adjusting a signal of the video signal, the automatic gain control circuit comprising:

• a black level detecting unit which detects the black level from the video signal;
• a white level detecting unit which detects the white level from the video signal;
• and
• an analog-to-digital converter which adjusts a dynamic range of the video signal based on a difference value between the black level and the white level;
• a level calculating unit which calculates a difference between the black level detected by the black level detecting unit and the white level detected by the white level detecting unit;
• a subtractor which calculates a difference between the difference calculated by the level calculating unit and a target value of the dynamic range of the video signal;
• and
• a gain determining unit which determines a target gain based on the difference calculated by the subtractor, wherein
• the analog-to-digital converter adjusts the dynamic range of the video signal based on the target gain determined by the gain determining unit.