Emission control driver and organic light emitting display having the same
View Patent ↗An emission control driver that applies an emission control signal for controlling an emission operation of a pixel circuit is provided. The emission control driver includes an emission control circuit with a plurality of transistors and a capacitor placed between a positive power supply voltage and a negative power supply voltage. When the driver is fabricated in an organic light emitting display (OLED), the transistors send a high level or low level emission control signal to a pixel circuit in response to a scan signal, and can be the same type transistors as the pixel circuit transistors. Further, the emission control driver may include a transistor for interrupting the positive power supply voltage in response to an initializing signal to initialize a capacitor of the pixel circuit.
1. An emission control driver for transmitting control signals to a gate terminal of an emission control transistor connected to a light emitting element for controlling an emission operation of a pixel, each pixel comprising a scan line controlling a gate terminal of a scanning transistor in said pixel through the use of a scan signal transmitted by said scan line in order to provide a data signal to the pixel, the emission control driver comprising:
a first signal transmitting portion to selectively output a positive power supply voltage in response to a (n−1)th scan signal supplied to an (n−1)th scan line of a pixel and a nth scan signal supplied to an nth scan line of a pixel;
a second signal transmitting portion to selectively output a negative power supply voltage in response to a (n+1)th scan signal supplied to an (n+1)th scan line of a pixel; and
an output portion connected between the first signal transmitting portion and second signal transmitting portion to selectively output the positive power supply voltage or negative power supply voltage to the emission control transistor as an emission control signal in response to the (n−1)th scan signal, nth scan signal, and (n+1)th scan signal;
wherein the first signal transmitting portion comprises:
a first switching portion for switching on or off in response to the (n−1)th scan signal and nth scan signal to receive and selectively output the positive power supply voltage; and
a second switching portion for switching on or off in response to the (n−1)th scan signal and nth scan signal to selectively transmit the positive power supply voltage from the first switching portion to the output portion;
wherein the first switching portion comprises:
a first transistor with an input terminal connected to the positive power supply voltage, an output terminal connected to the second switching portion and the output portion, and a control terminal for receiving the (n−1)th scan signal; and
a second transistor connected in parallel with the first transistor with an input terminal connected to the positive power supply voltage, an output terminal connected to the second switching portion and the output portion, and a control terminal for receiving the nth scan signal; and
wherein the second switching portion comprises:
a third transistor with an input terminal connected to the output terminal of the first transistor, an output terminal connected to the output portion, and a control terminal for receiving the (n−1)th scan signal; and
a fourth transistor connected in parallel with the third transistor with an input terminal connected to the output terminal of the first transistor, an output terminal connected to the output portion, and a control terminal for receiving the nth scan signal.
2. The emission control driver of claim 1 , wherein the (n−1)th scan signal is applied to the control terminal of the first transistor and the control terminal of the third transistor.
3. The emission control driver of claim 2 , wherein the n th scan signal is applied to the control terminal of the second transistor and the control terminal of the fourth transistor.
4. The emission control driver of claim 1 , wherein the second signal transmitting portion comprises:
a fifth transistor with an input terminal connected to the negative power supply voltage, an output terminal connected to the output portion, and a control terminal for receiving the (n+1)th scan signal; and
a sixth transistor with an input terminal connected to the negative power supply voltage, an output terminal connected to the output portion, and a control terminal for receiving the output signal of said fifth transistor.
5. The emission control driver of claim 4 , wherein the transistors of the first signal transmitting portion and second signal transmitting portion are p-type MOSFETs.
6. The emission control driver of claim 4 , wherein the transistors of the first signal transmitting portion and second signal transmitting portion are n-type MOSFETs.
7. The emission control driver of claim 4 , wherein the output portion comprises a capacitor.
8. The emission control driver of claim 7 , wherein the capacitor comprises:
a first electrode connected to the output terminal of the third transistor, the output terminal of the fifth transistor, and the control terminal of the sixth transistor, and
a second electrode connected to the output terminal of the first transistor, the input terminal of the third transistor, and the output terminal of the sixth transistor.
9. The emission control driver of claim 8 , wherein the output portion outputs an emission control signal from the second electrode of the capacitor.
10. The emission control driver of claim 7 , further comprising:
an initializing transistor connected between the first switching portion and the positive power supply voltage for interrupting the positive power supply voltage to the first switching portion in response to an initializing signal.
11. The emission control driver of claim 10 , wherein said initializing transistor is the same type of transistor as the transistors of the first signal transmitting portion and second signal transmitting portion.
12. An organic light emitting display (OLED), comprising:
a pixel portion comprising pixels for displaying a predetermined image thereon and comprising scan lines and data lines crossing the scan lines;
a scan driver for supplying (n−1)th, nth, and (n+1)th scan signals to (n−1)th, nth, and (n+1)th scan lines, respectively, of the pixel portion, each respective pixel of the pixel portion comprising a respective scan line controlling a gate terminal of a scanning transistor in the pixel through the use of a respective scan signal transmitted by a respective scan line in order to provide a data signal to the pixel;
a data driver for supplying a data signal to the pixel portion; and
an emission control driver fabricated on the OLED panel for supplying an emission control signal to the pixel portion to control an emission operation of the pixel portion the emission control for transmitting control signals to a gate terminal of an emission control transistor connected to a light emitting element for controlling an emission operation of a pixel;
wherein the emission control driver comprises transistors of the same type as the transistors in the pixel portion, and
wherein the emission control driver transistors are switched on or off in response to the (n−1)th, nth, and (n+1)th scan signals supplied by the scan driver to pixels of the pixel portion;
wherein the emission control driver comprises:
a first signal transmitting portion coupled to a positive power supply voltage to selectively output a positive power supply voltage in response to the (n−1)th and nth scan signals supplied to respective pixels:
a second signal transmitting portion coupled to a negative power supply voltage to selectively output a negative power supply voltage in response to the (n+1)th scan signal supplied to a pixel; and
an output portion connected between the first signal transmitting portion and second signal transmitting portion to selectively receive said positive power supply voltage or said negative power supply voltage, and to selectively output said emission control signal in response to said positive power supply voltage or said negative power supply voltage;
wherein the first signal transmitting portion comprises:
a first switching portion for switching on or off in response to the (n−1)th scan signal and nth scan signal to receive and selectively output the positive power supply voltage; and
a second switching portion for switching on or off in response to the (n−1)th scan signal and nth scan signal to selectively transmit the positive power supply voltage from the first switching portion to the output portion;
wherein the first switching portion comprises:
a first transistor with an input terminal connected to the positive power supply voltage, an output terminal connected to the second switching portion and the output portion, and a control terminal for receiving the (n−1)th scan signal; and
a second transistor connected in parallel with the first transistor with an input terminal connected to the positive power supply voltage, an output terminal connected to the second switching portion and the output portion, and a control terminal for receiving the nth scan signal; and
wherein the second switching portion comprises:
a third transistor with an input terminal connected to the output terminal of the first transistor, an output terminal connected to the output portion, and a control terminal for receiving the (n−1)th scan signal; and
a fourth transistor connected in parallel with the third transistor with an input terminal connected to the output terminal of the first transistor, an output terminal connected to the output portion, and a control terminal for receiving the nth scan signal.
13. The organic light emitting display of claim 12 , wherein the emission control driver further comprises:
an initializing transistor connected between the first signal transmitting portion and the positive power supply voltage for interrupting the positive power supply voltage from the first signal transmitting portion in response to an initializing signal.
14. The organic light emitting display of claim 13 , wherein the transistors of the first signal transmitting portion, second signal transmitting portion, and the initializing transistor are p-type MOSFETs.