JPS5492080A - Driving method of thin film el element - Google Patents

Abstract

PURPOSE:To secure the luminance modulation through the pulse duration modulation by changing previously the voltage lower than the light emisson starting threshold level of the EL element to all picture elements on the selected scan electrodes. CONSTITUTION:Switches Sy1, Sy3, Syj, Sx1 ... Snk are turned on when the number of the data electrode is referred to as m and the number of one scanning electrode is n and the number of the selected picture elements is k at the driving time of one scan electrode. In this case, each picture element can be expressed by the equivalent circuits formed by capacity C1-C4. Difference Vs-Vp between writing voltage Vs and clamping voltage Vp is charged to all elements of scan electrode Y in the 1st timing, and then C1 and C2 are charged. No conduction is given via C2 when Vs is applied at the 2nd timing, and the time when the voltage of selected picture element C1 turns to Vs is always constant regardless of the number of the electrode of the matrix panel and the quantity of the data. The voltage of semi- selected picture element C2 and C4 becomes Vs-Vp and Vp respectively. And if Vp is selected properly to the level under the light emission threshold of the EL element, no light emission is obtained. In such constitution, the pulse duration can be modulated to perform the luminance modulation.