DIGITAL AND FEEDBACK CONTROL OF ANALOGUE AND DIGITAL CONVERTER INPUT

摘要

PURPOSE: To achieve conversion with high precision and without color degradation by dynamically performing scaling to a voltage range of an AD converter to convert an analog video signal into digital image data. CONSTITUTION: A blank signal 34 and a synchronizing signal 34b are separately generated from the analog video signal by separation mechanism 33. The digital pixel data 26 from the AD converter(ADC) 24, specified blank signal and the synchronizing signal are compared during a blank period and a synchronizing period by reference voltage control logic mechanism 42. Positive reference voltage is generated to the ADC 24 by variable voltage mechanism 38 based on the comparison and controlled so as to be converged into a desired value by reference voltage feedback mechanism 36. The digital pixel data 26 and a specified synchronization signal value are compared by receiving the synchronizing signal 34b↓' by offset control logic mechanism 48. An offset of the analog video signal is controlled to be converged into the desired value by voltage feedback mechanism 35 with variable current mechanism 44 controlled based on the comparison.