Display device and method for driving same
An object of the disclosure is to achieve a current-driven display device able to compensate for a variation in threshold voltage of a drive transistor without causing a variation in luminance. A pixel circuit includes an organic EL element; a drive transistor; a first capacitor having a first electrode to be supplied with a reference voltage during a data writing period and a second electrode to be supplied with a data voltage-during a data writing period; a second capacitor having a first electrode connected to the first electrode of the first capacitor and a second electrode connected to a first conduction terminal of the drive transistor; and a short-circuit control transistor having a gate terminal to be supplied with a light emission control signal-, which becomes active during a light emission period, a first conduction terminal connected to the first electrode of the first capacitor, and a second conduction terminal connected to the second electrode of the first capacitor.
1. A display device comprising:
a pixel circuit arranged in a matrix shape;
a first power source wiring line supplied with a first power supply voltage;
a second power source wiring line supplied with a second power supply voltage at a lower voltage level than a voltage level of the first power supply voltage;
a third power source wiring line supplied with a third power supply voltage; and
a data signal line provided for each column and supplied with a data voltage,
the pixel circuit including:
a display element that is provided between the first power source wiring line and the second power source wiring line, and emits light with luminance in accordance with an amount of a current supplied;
a first capacitance element having a first electrode to be supplied with the third power supply voltage during a data writing period, and a second electrode to be supplied with the data voltage during a data writing period;
a drive transistor that is provided to be connected in series to the display element between the first power source wiring line and the second power source wiring line, and has a control terminal connected to the second electrode of the first capacitance element, a first conduction terminal to be supplied with the first power supply voltage during a light emission period, and a second conduction terminal;
a second capacitance element having a first electrode connected to the first electrode of the first capacitance element, and a second electrode connected to the first conduction terminal of the drive transistor; and
a short-circuit control transistor having a control terminal to be supplied with a signal that becomes active during a light emission period, a first conduction terminal connected to the first electrode of the first capacitance element, and a second conduction terminal connected to the second electrode of the first capacitance element,
wherein the display device further comprising:
an initialization power source wiring line supplied with an initialization voltage for initializing the pixel circuit,
the display element includes a first electrode provided electrically on the first power source wiring line side, and a second electrode provided electrically on the second power source wiring line side, and
the pixel circuit further includes
a first initialization transistor having a control terminal to be supplied with a signal that becomes active during an initialization period that is set before a data writing period, a first conduction terminal connected to the second electrode of the first capacitance element, and a second conduction terminal connected to the initialization power source wiring line,
a second initialization transistor having a control terminal to be supplied with a signal that becomes active during a data writing period, a first conduction terminal connected to the first electrode of the display element, and a second conduction terminal connected to the initialization power source wiring line, and
an initialization control transistor having a control terminal to be supplied with a signal that becomes active during an initialization period, a first conduction terminal connected to the second conduction terminal of the drive transistor, and a second conduction terminal connected to the first electrode of the display element.
2. The display device according to claim 1 ,
wherein the third power supply voltage is a fixed voltage.
3. The display device according to claim 2 ,
wherein a voltage level of the third power supply voltage is equal to or greater than a voltage level of the second power supply voltage and equal to or lower than a voltage level of the first power supply voltage.
4. The display device according to claim 1 ,
wherein the pixel circuit further includes an electric discharge control transistor having a control terminal to be supplied with a signal that becomes active during a period other than a light emission period, a first conduction terminal connected to the second conduction terminal of the drive transistor, and a second conduction terminal connected to the second power source wiring line.
5. The display device according to claim 1 ,
wherein the pixel circuit further includes
a first writing control transistor having a control terminal to be supplied with a signal that becomes active during a data writing period, a first conduction terminal to be supplied with the data voltage, and a second conduction terminal connected to the second electrode of the first capacitance element,
a second writing control transistor having a control terminal to be supplied with a signal that becomes active during a data writing period, a first conduction terminal connected to the third power source wiring line, and a second conduction terminal connected to the first electrode of the first capacitance element, and
a light emission control transistor having a control terminal to be supplied with a signal that becomes active during a light emission period, a first conduction terminal connected to the first power source wiring line, and a second conduction terminal connected to the first conduction terminal of the drive transistor.
6. The display device according to claim 1 ,
wherein the third power supply voltage is the initialization voltage.
7. The display device according to claim 1 ,
wherein a capacitance value of the second capacitance element is greater than a capacitance value of the first capacitance element.
8. The display device according to claim 1 ,
wherein the display element is an organic EL element.
9. A driving method for a display device equipped with a pixel circuit arranged in a matrix shape, a first power source wiring line supplied with a first power supply voltage, a second power source wiring line supplied with a second power supply voltage at a lower voltage level than a voltage level of the first power supply voltage, a third power source wiring line supplied with a third power supply voltage, and a data signal line provided for each column and supplied with a data voltage,
the pixel circuit including:
a display element that is provided between the first power source wiring line and the second power source wiring line, and emits light with luminance in accordance with an amount of a current supplied;
a first capacitance element having a first electrode and a second electrode;
a drive transistor that is provided to be connected in series to the display element between the first power source wiring line and the second power source wiring line, and has a control terminal connected to the second electrode of the first capacitance element, a first conduction terminal, and a second conduction terminal; and
a second capacitance element having a first electrode connected to the first electrode of the first capacitance element and a second electrode connected to the first conduction terminal of the drive transistor, and
the driving method comprising:
electrically connecting the first electrode of the first capacitance element and the third power source wiring line and electrically connecting the second electrode of the first capacitance element and the data signal line as data writing processing, in a state in which the first electrode and the second electrode of the first capacitance element are electrically disconnected, and the first conduction terminal of the drive transistor and the first power source wiring line are electrically disconnected; and
electrically connecting the first electrode and the second electrode of the first capacitance element and electrically connecting the first conduction terminal of the drive transistor and the first power source wiring line as light emission processing, in a state in which the first electrode of the first capacitance element and the third power source wiring line are electrically disconnected, and the second electrode of the first capacitance element and the data signal line are electrically disconnected,
wherein the display device further includes an initialization power source wiring line provided with an initialization voltage for initializing the pixel circuit, and
the driving method further includes electrically connecting the second electrode of the first capacitance element and the initialization power source wiring line as initialization processing, in a state in which a current supply to the display element is blocked and the first electrode and the second electrode of the first capacitance element are electrically connected.
10. A driving method for a display device equipped with a pixel circuit arranged in a matrix shape, a first power source wiring line supplied with a first power supply voltage, a second power source wiring line supplied with a second power supply voltage at a lower voltage level than a voltage level of the first power supply voltage, a third power source wiring line supplied with a third power supply voltage, and a data signal line provided for each column and supplied with a data voltage,
the pixel circuit including:
a display element that is provided between the first power source wiring line and the second power source wiring line, and emits light with luminance in accordance with an amount of a current supplied;
a first capacitance element having a first electrode and a second electrode;
a drive transistor that is provided to be connected in series to the display element between the first power source wiring line and the second power source wiring line, and has a control terminal connected to the second electrode of the first capacitance element, a first conduction terminal, and a second conduction terminal; and
a second capacitance element having a first electrode connected to the first electrode of the first capacitance element and a second electrode connected to the first conduction terminal of the drive transistor, and
the driving method comprising:
electrically connecting the first electrode of the first capacitance element and the third power source wiring line and electrically connecting the second electrode of the first capacitance element and the data signal line as data writing processing, in a state in which the first electrode and the second electrode of the first capacitance element are electrically disconnected, and the first conduction terminal of the drive transistor and the first power source wiring line are electrically disconnected; and
electrically connecting the first electrode and the second electrode of the first capacitance element and electrically connecting the first conduction terminal of the drive transistor and the first power source wiring line as light emission processing, in a state in which the first electrode of the first capacitance element and the third power source wiring line are electrically disconnected, and the second electrode of the first capacitance element and the data signal line are electrically disconnected,
wherein the display element includes a first electrode provided electrically on the first power source wiring line side and a second electrode provided electrically on the second power source wiring line side, and
the first electrode of the display element and an initialization power source wiring line supplied with an initialization voltage are electrically connected in the data writing processing.
11. The driving method according to claim 9 , further comprising:
causing a state of the pixel circuit to be such that the first electrode and the second electrode of the first capacitance element are electrically disconnected, the first conduction terminal of the drive transistor and the first power source wiring line are electrically disconnected, the first electrode of the first capacitance element and the third power source wiring line are electrically disconnected, and the second electrode of the first capacitance element and the data signal line are electrically disconnected, as light emission preparation processing.
12. The driving method according to claim 11 ,
wherein, in the light emission preparation processing, after the second electrode of the first capacitance element and the data signal line are brought into an electrically disconnected state, the first electrode of the first capacitance element and the third power source wiring line are brought into an electrically disconnected state.
13. The driving method according to claim 9 ,
wherein, in the data writing processing, the second conduction terminal of the drive transistor and the second power source wiring line are electrically connected in a state in which a current supply to the display element is blocked.
14. The driving method according to claim 10 , further comprising:
causing a state of the pixel circuit to be such that the first electrode and the second electrode of the first capacitance element are electrically disconnected, the first conduction terminal of the drive transistor and the first power source wiring line are electrically disconnected, the first electrode of the first capacitance element and the third power source wiring line are electrically disconnected, and the second electrode of the first capacitance element and the data signal line are electrically disconnected, as light emission preparation processing.
15. The driving method according to claim 14 ,
wherein, in the light emission preparation processing, after the second electrode of the first capacitance element and the data signal line are brought into an electrically disconnected state, the first electrode of the first capacitance element and the third power source wiring line are brought into an electrically disconnected state.
16. The driving method according to claim 10 ,
wherein, in the data writing processing, the second conduction terminal of the drive transistor and the second power source wiring line are electrically connected in a state in which a current supply to the display element is blocked.