31results about How to "Compensation for Threshold Voltage Variations" patented technology

A display device includes: a display unit including pixels coupled to scan lines for transmitting scan signals, data lines for transmitting data signals, and light emission control lines for transmitting light emission control signals; a scan driver; a data driver; and a light emission driver. Each pixel includes: an OLED; a driving transistor to transmit a driving current corresponding to a data signal to the OLED; a first transistor to transmit the data signal to the driving transistor according to a first scan signal; a second transistor to apply a first power source voltage to a first electrode of the driving transistor according to a second scan signal, during an initialization period for initializing a gate electrode voltage of the driving transistor; and a capacitor including a first electrode coupled to a gate electrode of the driving transistor and a second electrode coupled to a first power source supply.

A pixel at an ith pixel row (i is a natural number) includes an organic light emitting diode (OLED); a driving transistor for supplying a current to the OLED and a storage capacitor between a gate electrode of the driving transistor and an (i−1)th emission control line; and a compensating unit for controlling a voltage of the gate electrode of the driving transistor to compensate for deterioration of the OLED. The compensating unit includes: a first compensating unit transistor and a second compensating unit transistor between the OLED and a first power source; first and second feedback capacitors between a second node between the first and second compensating unit transistors and a first node between the gate electrode of the driving transistor and the storage capacitor; and a third compensating unit transistor coupled between a third node between the first and second feedback capacitors and a reference voltage source.

A pixel circuit for an active-matrix organic light-emitting diode display including an organic light-emitting diode and a driving circuit. The driving circuit includes six switches, a driving transistor, and a capacitor. By compensating the threshold voltage of the driving transistor, the electric current flowing through the organic light-emitting diode can precisely be controlled without influence by the threshold voltage of the driving transistor, increasing the luminance uniformity and stability of the display. Furthermore, the present invention can be applied to a depletion mode driving transistor (i.e., an oxide TFT). Thus, the threshold voltage can be obtained to proceed with compensation no matter the threshold voltage of the driving transistor is larger or smaller than zero.

The invention discloses an AMOLED pixel driver circuit and pixel driving method, by using a pixel driver circuit of 3T2C structure to effectively compensate threshold voltage of driving TFT in each pixel; through adding a third TFT (T3) and introducing control signal voltage (Vc) to control the third TFT (T3) to prevent current from flowing through in the threshold voltage detection phase and threshold voltage compensation phase so as to reduce the complexity of the power supply (Vdd); by adding a second capacitor (C2) to regulate the influence on the source voltage of the driving TFT by the data signal voltage (VData) so as to reduce the data signal complexity. As a result, the data signal only needs to switch once.

A pixel circuit includes a drive transistor that controls an amount of current to a light-emitting device, and a second transistor connected to the gate of the drive transistor and a second terminal of the drive transistor, such that when the second transistor is in an on state the drive transistor becomes diode-connected. A threshold voltage of the drive transistor is compensated during a compensation phase while the drive transistor is diode connected. The light-emitting device is connected between the drive transistor and at a second node to a first voltage input. The pixel circuit further includes a storage capacitor having a first plate connected to the gate of the drive transistor, and a programming capacitor having a first plate connected to a second plate of the storage capacitor, and a second plate of the programming capacitor is electrically connected to a data voltage input during a data programming phase. The second plate of the storage capacitor and the first plate of the programming capacitor are connectable to a reference voltage to perform the compensation phase independently of the programming phase, and the storage capacitor and the programming capacitor are series connected during the emission phase.

A pixel circuit has enhanced performance by minimizing noise effects from the data and reference voltage lines. To prevent data line noise from interfering with the drive transistor gate voltage during emission, a triple gate isolation is used between the data voltage line and the gate of the drive transistor by which three transistors are connected between the data voltage line and the gate of the drive transistor. To further improve the isolation, one of the middle nodes of the triple gate farthest from the data voltage line is connected to one floating node that is connectable to a reference voltage during the threshold compensation phase. A first capacitor is used for the threshold compensation, and a second capacitor is used to scale the data voltage during programming. The threshold compensation and data programming operations are thereby independent of each other to minimize programming time.

A pixel circuit compensates the threshold voltage variations of the drive transistor with an ultra-short one horizontal (1H) time, with additionally removing the possible memory effects associated with the light-emitting device and the drive transistor from the previous frame. An ultra-short 1H time (<2 μs) is achieved via separation of threshold compensation of the drive transistor and data programming phases. The pixel circuit has a two-capacitor configuration, whereby a first capacitor is used for drive transistor threshold compensation, and a second capacitor is used to store the data voltage during a data pre-loading phase. Two transistors are employed to electrically connect the gate and source of the drive transistor to a common initialization voltage during an initialization phase to reset circuit voltages for the current frame. In this manner, no current flows through the drive transistor to the light-emitting device during the initialization phase when the light-emitting device does not emit light, which saves power. An array of individual pixel circuits is controlled using a global compensation scheme in which global control signals are applied to the individual pixel circuits of the pixel array.

A pixel circuit for a display device is operable in a compensation phase, a data programming phase, and an emission phase, whereby the one horizontal time is minimized while maintaining accurate compensation of the threshold voltage of the drive transistor. The pixel circuit includes: a storage capacitor having a first plate connected to a third terminal of the drive transistor that receives a voltage input, and a second plate connected to the gate of the drive transistor; and a programming capacitor having a first plate connected to second and third transistors, and a second plate of the programming capacitor is electrically connected to a data voltage input during the data programming phase, wherein the first plate of the programming capacitor is electrically connected to the second plate of the storage capacitor when the second transistor is in an on state. The second plate of the programming capacitor further is electrically connected to a reference voltage input to perform the compensation phase, and the programming capacitor further is electrically isolated from the storage capacitor and the drive transistor by the second and third transistors during the emission phase.

A pixel circuit is operable in initialization, data programming, threshold compensation, and emission phases. The pixel circuit includes a drive transistor configured to control an amount of current to a light-emitting device during the emission phase depending upon a voltage applied to a gate of the drive transistor. A first ultra-low leakage oxide transistor is employed as a data switch device, and the data voltage is applied to the gate of the drive transistor through the first ultra-low leakage oxide transistor during the data programming phase. A second ultra-low leakage oxide transistor is employed as an initialization switch device. The second ultra-low leakage oxide transistor is in an on state during the initialization, data programming, and threshold compensation phases, and the initialization voltage is applied to the gate of the drive transistor through the second ultra-low leakage oxide transistor during the initialization phase.