Patent ID: 8896224
Filing Date: 2014-11-25
Classification: H05B,Y02B

Abstract:
1. A driver circuit for an electroluminescent (EL) element, comprising: a first thin-film transistor (TFT); a second TFT, comprising a source connected to a drain of the first TFT; a third TFT, comprising a source connected to a drain of the second TFT and a drain connected to ground; an EL element, comprising an anode and a cathode, the anode connected to a first supply voltage, and the cathode connected to a source of the first TFT; a storage capacitor, comprising a first terminal and a second terminal, the first terminal connected to a gate of the second TFT and the second terminal connected to the drain of the second TFT; a fourth TFT, comprising a source connected to a second supply voltage and a drain connected to the source of the second TFT; a fifth TFT, comprising a source connected to the drain of the fourth TFT and a drain connected to the gate of the second TFT; and a sixth TFT, comprising a source connected to the drain of the second TFT and a drain connected to a data signal; wherein a duty cycle of the driver circuit for the EL element comprises a sampling phase and a holding phase, the first TFT, the second TFT, and the third TFT are conducted at the holding phase, an impedance of the first TFT, the second TFT, and the third TFT in cascode is greater than an impedance of the EL element, wherein the fourth transistor the fifth transistor, and the sixth transistor are cut-off in the holding phase, wherein the second transistor, the fourth transistor, the fifth transistor, and the sixth transistor are conducted at the sampling phase, while the first transistor and the third transistor are cut-off at the sampling phase, wherein the storage capacitor is used for storing an electric signal across the gate of the second TFT and the drain of the second TFT at the sampling stage and for holding a voltage which is between the gate of the second TFT and the drain of the second TFT and varies with the electric signal at the holding phase for controlling brightness of the EL element.