Active matrix display device
View Patent ↗A plurality of pixel units are arranged in a matrix, each pixel unit including a display element and a pixel circuit which supplies a driving current to the display element. Each pixel circuit includes a first memory section which stores, in a write period of the pixel unit, a first driving current corresponding to a first signal current and then outputs the stored first driving current, and further stores a second driving current corresponding to a second signal current, and a second memory section which stores the first driving current output from the first memory section in the write period of the pixel unit. The pixel circuit outputs, in a light emission period of the pixel unit, a difference current between the second driving current stored in the first memory section and the first driving current stored in the second memory section to the display element as the driving current.
1. An active matrix display device comprising:
a plurality of pixel units arranged in a matrix on a substrate, each of the pixel units including a display element and a pixel circuit which supplies a driving current to the display element;
a plurality of video signal lines connected to columns of the pixel units, respectively; and
a signal line driving circuit which supplies a first signal current to the pixel circuit via the video signal line and then supplies a second signal current to the pixel circuit via the video signal line,
each of the pixel circuits including a first memory section which stores, in a write period of the pixel unit, a first driving current corresponding to the first signal current and then outputs the stored first driving current, and further stores a second driving current corresponding to the second signal current, and a second memory section which stores the first driving current which is output from the first memory section in the write period of the pixel unit, and each of the pixel circuits being configured to output, in a light emission period of the pixel unit, a difference current between the second driving current stored in the first memory section and the first driving current stored in the second memory section to the display element as the driving current.
2. The active matrix display device according to claim 1 , wherein the first memory section includes a first driving transistor which is formed of a P-channel thin-film transistor and outputs the first driving current and the second driving current, and the second memory section includes a second driving transistor which is formed of an N-channel thin-film transistor and outputs the first driving current which is written by the first driving transistor.
3. The active matrix display device according to claim 1 , wherein the signal line driving circuit includes an N-channel IC which supplies the first signal current and the second signal current to the first memory section of each of the pixel units via the video signal line.
4. The active matrix display device according to claim 2 , wherein each of the pixel circuits includes a pixel switch which controls selection/non-selection of the pixel unit, and an output switch which is connected between voltage power supplies in series to the display element and the first and second driving transistors,
the first memory section includes a first storage capacitance which stores a potential between a source and a gate of the first driving transistor, and a first hold switch which is formed of a transistor, is connected to the gate and a drain of the first driving transistor, and controls turn-on/turn-off of the first driving transistor, and
the second memory section includes a second storage capacitance which stores a potential between a source and a gate of the second driving transistor, a second hold switch which is formed of a transistor, is connected to the gate and a drain of the second driving transistor, and controls turn-on/turn-off of the second driving transistor, and a first switch which is formed of a transistor and is connected to the drain of the first driving transistor and the source of the second driving transistor, the pixel switch being connected to the first hold switch and the video signal line.
5. The active matrix display device according to claim 4 , wherein the pixel switch and the first hold switch are formed of P-channel thin-film transistors and are opened/closed by a common control signal.
6. The active matrix display device according to claim 4 , wherein the first switch is formed of an N-channel thin-film transistor and is opened/closed by a control signal which is common to the pixel switch and the first hold switch.
7. The active matrix display device according to claim 4 , wherein the pixel switch and the first hold switch are formed of N-channel thin-film transistors and are opened/closed by a common control signal.
8. The active matrix display device according to claim 7 , wherein the first switch is formed of a P-channel thin-film transistor and is opened/closed by a control signal which is common to the pixel switch and the first hold switch.
9. The active matrix display device according to claim 4 , wherein the transistor, the first driving transistor and the second driving transistor are formed of thin-film transistors in which polysilicon is used for semiconductor layers.
10. The active matrix display device according to claim 1 , wherein the display element is a self-luminous display element including an organic light-emitting layer between opposed electrodes.