Pixel circuit and driving method thereof and display panel having the same

A method of driving a pixel circuit configured to supply a current to a light emitting device so that the light emitting device emits light of a desired grayscale, the pixel circuit comprising:

• a first transistor having a first terminal connected to a data line and to which a data signal is applied and a gate terminal connected to a scan line and to which a scan signal is applied;
• a third transistor having a gate terminal connected to a second terminal of the first transistor and a second terminal connected to the light emitting device;
• a capacitor having a second terminal commonly connected to the second terminal of the first transistor and the gate terminal of the third transistor;
• and a second transistor having a second terminal commonly connected to a first terminal of the capacitor and a first terminal of the third transistor, a first terminal connected to a first power supply voltage, and a gate terminal connected to an emission line to which an emission signal is applied, the method comprising:
• charging a gate voltage node of the third transistor with an initial voltage, and charging a source voltage node of the third transistor with the first power supply voltage;
• in a state in which the second transistor is turned off, discharging a source voltage of the source voltage node by a source follower until a voltage corresponding to a sum of absolute values of the initial voltage and the threshold voltage is reached or until the third transistor is turned off;
• and
• in a state in which the third transistor is turned off, when coupling occurs by parasitic capacitors seen at the gate voltage node and the source voltage node, charging the source voltage node with a source voltage reflecting the coupling between the capacitor and the parasitic capacitor by a data voltage supplied through the first transistor.

A display panel configured to output an image, the display panel comprising:

• a pixel unit in which a plurality of pixels are arranged;
• and
• a pixel circuit provided in a first pixel among the pixels, and configured to supply a current to a light emitting device so that the light emitting device belonging to the first pixel emits light of a desired grayscale,
• wherein the pixel circuit comprises:
• a first transistor having a first terminal connected to a data line and to which a data signal is applied and a gate terminal connected to a scan line and to which a scan signal is applied;
• a third transistor having a gate terminal connected to a second terminal of the first transistor and a second terminal connected to the light emitting device;
• a capacitor having a second terminal commonly connected to the second terminal of the first transistor and the gate terminal of the third transistor;
• and
• a second transistor having a second terminal commonly connected to a first terminal of the capacitor and a first terminal of the third transistor, a first terminal connected to a first power supply voltage, and a gate terminal connected to an emission line to which an emission signal is applied,
• wherein, in a pre-charge period of a single operation cycle period, a gate voltage node of the third transistor is charged with an initial voltage, and a source voltage node of the third transistor is charged with the first power supply voltage, and
• wherein, in a data input period following a threshold voltage sampling period of the single operation cycle period, the first transistor maintains a turned-on state by the scan signal, the second transistor maintains a turned-off state by the emission signal, the data signal is applied to the gate terminal of the third transistor through the first transistor and the third transistor maintains a turned-off state and coupling occurs by parasitic capacitors seen at the gate voltage node and the source voltage node.