Polarity detection circuit for synchronizing signal

Abstract

Abstract PURPOSE:To execute a stable polarity detection and the detection of information at the time of non-inputting by using two comparators having comparing voltages different from each other and properly setting the relation of the comparing reference voltages and the mean DC voltage of an input synchronizing signal. CONSTITUTION:To the non-inversion input of a comparator 1 and the inversion input of a comparator 2, a synchronizing signal in which the mean value DC voltage is made into a reference voltage V3 is inputted. For the comparators 1 and 2, the comparing voltages are V4 and V5 respectly. A voltage holding circuit is composed of diodes D1 and D2, resistances R4 and R5 and capacities C4 and C5 at the output side of respective comparators 1 and 2. The relation of the voltages V3-V5 is V4>V3>V5, and simultaneously, V4-V3=V3-V4 is made. For the voltages V3-V5, when the inputted synchronizing signal has a straight polarity, the voltage is set so as to cross the voltage V3 and not to cross the voltage V5. Further, the inputted synchronizing signal has a negative polarity, the voltage is set so as to cross the voltage V5 and not to cross the voltage V3. Thus, the stable polarity detection can executed, and simultaneously, a non-input can be decided.

Inventors

• 👤 Junichi Momotake

Bibliographic Details