Light emitting device, photoelectric conversion device, electronic device, lighting device, and mobile body
The light emitting device comprises: a plurality of pixels, each having a light-emitting element, a driving transistor configured to drive the light-emitting element, a capacitor configured to hold a threshold voltage of the driving transistor, a signal line, a first switch configured to connect the signal line and a control electrode of the driving transistor, and a second switch configured to connect a first main electrode of the driving transistor and a predetermined node; and a driving circuit configured to drive the signal line. In a preparation period in which the threshold voltage is held in the capacitor, the first switch is controlled to be on and the second switch is controlled to be off, and the driving circuit drives the signal line at a voltage level selected from a plurality of different voltage levels.
1. A light emitting device comprising:
a plurality of pixels, each having a light-emitting element, a driving transistor configured to drive the light-emitting element, a capacitor configured to hold a threshold voltage of the driving transistor, a signal line, a first switch configured to connect the signal line and a control electrode of the driving transistor, and a second switch configured to connect a first main electrode of the driving transistor and a predetermined node; and
a driving circuit configured to drive the signal line, wherein
in a preparation period in which the threshold voltage is held in the capacitor, the first switch is controlled to be on and the second switch is controlled to be off, and the driving circuit drives the signal line at a voltage level selected from a plurality of different voltage levels, and
in a signal write period in which a luminance signal value is written to the light-emitting element, the first switch is controlled to be on and the second switch is controlled to be off, and the driving circuit drives the signal line at a voltage that corresponds to the luminance signal value.
2. The light emitting device according to claim 1 , wherein
the plurality of difference voltage levels include a first voltage and a second voltage, and
the light-emitting element emits light in a first mode in which the first voltage is supplied and the threshold voltage is held or a second mode in which the second voltage is supplied and the threshold voltage is held.
3. The light emitting device according to claim 2 , wherein
the first voltage is smaller than the second voltage, and
when the signal line is driven at the same voltage, which is a voltage that corresponds to the luminance signal value in the first mode and the second mode, in the signal write period, the light-emitting element emits light at a higher luminance in the second mode than in the first mode.
4. The light emitting device according to claim 2 , wherein
the first voltage is smaller than the second voltage, and
the light-emitting element emits light at a lower luminance in the second mode than in the first mode with respect to the luminance signal value of the same value.
5. The light emitting device according to claim 1 , wherein the selected voltage level is selected from among the plurality of difference voltage levels in accordance with an environmental temperature of the light-emitting element.
6. The light emitting device according to claim 5 , wherein when the environmental temperature is lower than a predetermined temperature, a higher voltage level is selected from among the plurality of different voltage levels.
7. The light emitting device according to claim 1 , wherein a third switch is further connected between an anode and a cathode of the light-emitting element.
8. The light emitting device according to claim 1 , further comprising: a control unit, wherein the driving circuit selects a voltage from among the plurality of different voltage levels in accordance with an instruction from the control unit.
9. A photoelectric conversion device comprising: an optical unit having a plurality of lenses; an image capturing element configured to receive light that has passed through the optical unit; and a display unit configured to display an image that the image capturing element has captured, wherein the display unit includes the light emitting device according to claim 1 .
10. An electronic device comprising: a display unit having the light emitting device according to claim 1 ; a housing in which the display unit is provided; and a communication unit provided in the housing and configured to communicate with an external unit.
11. A lighting device comprising: a light source having the light emitting device according to claim 1 ; and a light diffusing unit or an optical film configured to transmit light that the light source emits.
12. A mobile body comprising: a lighting unit having the light emitting device according to claim 1 ; and a body in which the lighting unit is provided.