REVERSIBLE BIAS ORGANIC LIGHT-EMITTING DIODE (OLED) DRIVE CIRCUIT WITHOUT INITIALIZATION VOLTAGE

• US 20180357966A1
• Filed: 06/07/2017
• Published: 12/13/2018
• Est. Priority Date: 06/07/2017
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Ma, Jia Wei, Shin, Heesun, Weng, Wei Hsiang, Kim, Cheonhong, Bos, Jan
• Granted Patent: US 10,276,105 B2
• Time in Patent Office: Days
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 2300/0814 used for selection purposes, e.g. logical AND for partial update
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0823 used to establish symmetry in driving, e.g. with polarity inversion
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2300/0861 with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 2320/045 Compensation of drifts in the characteristics of light emitting or modulating elements
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element
• CPC Class Codes: G09G 3/3258 with pixel circuitry controlling the voltage across the light-emitting element
• CPC Class Codes: G09G 3/3266 Details of drivers for scan electrodes
• CPC Class Codes: G09G 3/3291 in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

Abstract

This disclosure provides systems, methods and apparatus for OLED control circuits. In some implementations, the OLED control circuit can be configured to reverse the bias of the OLED without the use of a dedicated initialization voltage. A low voltage data signal applied on a data line can be used to drain voltage from the anode of the OLED through a diode-connected transistor. A high voltage data signal applied on the same data line can be used to store a reference voltage on a storage capacitor, where the reference voltage is also a function of the threshold voltage of a driving transistor of the OLED control circuit. The stored reference voltage can be used to compensate for the threshold voltage of the driving transistor when the OLED is energized by a current, so that the current is independent of the threshold voltage of the driving transistor.

Claims

1. An organic light-emitting diode (OLED) control circuit configured to receive signals from a data line, an emission line, a scan line, a high-power supply line and a low power supply line, the OLED control circuit comprising:

an organic light-emitting diode (OLED) having an anode and a cathode, the cathode in electrical communication with the low power supply line;

a driving transistor having a gate, a source, and a drain, the source of the driving transistor in electrical communication with the OLED and a drain of the driving transistor in electrical communication with the high-power supply line;

a storage capacitor, a first plate of the storage capacitor in electrical communication with both the gate and the drain of the driving transistor, and a second plate of the storage capacitor in electrical communication with the high power supply line;

a data switch transistor having a source in electrical communication with the data line, a drain in electrical communication with the drain of the driving transistor, and a gate in electrical communication with the scan line; and

a first diode-connected transistor, the first diode-connected transistor having a gate, a drain, and a source, the drain of the first diode-connected transistor connected to the gate of the first diode-connected transistor and in electrical communication with the data line, and the source of the first diode-connected transistor in electrical communication with the anode of the OLED.

2. The control circuit of claim 1, additionally comprising a second diode-connected transistor having a source, a gate, and a drain, the drain of the second diode-connected transistor connected to the gate of the first diode-connected transistor and in electrical communication with the data line, and the source of the second diode-connected transistor in electrical communication with the first plate of the storage capacitor.

3. The control circuit of claim 2, additionally comprising a first leak-suppressing transistor connected between the source of the first diode-connected transistor and the anode of the OLED.

4. The control circuit of claim 3, additionally comprising a second leak-suppressing transistor connected between the source of the first diode-connected transistor and the first plate of the storage capacitor.

5. The control circuit of claim 1, additionally comprising a power conducting transistor, the power conducting transistor connected between the source of the driving transistor and the high-power supply line, the power conducting transistor having a gate in electrical communication with the emission line, a source in electrical communication with the high-power supply line, and a drain in electrical communication with the source of the power conduction transistor.

6. The control circuit of claim 1, additionally comprising an OLED-connected transistor, the OLED-connected transistor connected between the data switching transistor and the anode of the OLED, the OLED-connected transistor having a gate in electrical communication with the emission line, a source in electrical communication with OLED, and a drain in electrical communication with the data switching transistor.

7. The control circuit of claim 1, wherein the control circuit is configured to initialize the OLED by draining voltage from the anode of the OLED through the first diode-connected transistor to reverse the bias of the OLED.

8. The control circuit of claim 1, wherein the first plate of the storage capacitor is configured to store a reference voltage, and wherein the reference voltage is a function of a high data voltage applied on the on the data line and the threshold voltage of the driving transistor.

9. An organic light-emitting diode (OLED) control circuit configured to receive signals from a data line, an emission line, a scan line, a high-power supply line and a low power supply line, the OLED control circuit comprising:

an organic light-emitting diode (OLED) having an anode and a cathode, the cathode in electrical communication with the low power supply line;

a driving transistor having a gate, a source, and a drain, the source of the driving transistor in electrical communication with the OLED and a drain of the driving transistor in electrical communication with the high-power supply line;

means for storing a reference voltage, the reference voltage being a function of a high data voltage applied on the on the data line and the threshold voltage of the driving transistor;

a data switch transistor having a source in electrical communication with the data line, a drain in electrical communication with the drain of the driving transistor, and a gate in electrical communication with the scan line; and

a first diode-connected transistor configured to drain voltage from the anode of the OLED through the initializing means to reverse the bias of the OLED, the first diode-connected transistor having a gate, a drain, and a source, the drain of the first diode-connected transistor connected to the gate of the first diode-connected transistor and in electrical communication with the data line, and the source of the first diode-connected transistor in electrical communication with the anode of the OLED.

10. The control circuit of claim 9, wherein the storage means comprises a storage capacitor, a first plate of the storage capacitor in electrical communication with both the gate and the drain of the driving transistor, and a second plate of the storage capacitor in electrical communication with the high power supply line.

12. The control circuit of claim 9, additionally comprising a second diode-connected transistor having a source, a gate, and a drain, the drain of the second diode-connected transistor connected to the gate of the first diode-connected transistor and in electrical communication with the data line, and the source of the second diode-connected transistor in electrical communication with the first plate of the storage capacitor.

13. The control circuit of claim 12, additionally comprising a first leak-suppressing transistor connected between the source of the first diode-connected transistor and the anode of the OLED.

14. The control circuit of claim 13, additionally comprising a second leak-suppressing transistor connected between the source of the first diode-connected transistor and the first plate of the storage capacitor.

15. The control circuit of claim 9, additionally comprising a power conducting transistor, the power conducting transistor connected between the source of the driving transistor and the high-power supply line, the power conducting transistor having a gate in electrical communication with the emission line, a source in electrical communication with the high-power supply line, and a drain in electrical communication with the source of the power conduction transistor.

16. The control circuit of claim 9, additionally comprising an OLED-connected transistor, the OLED-connected transistor connected between the data switching transistor and the anode of the OLED, the OLED-connected transistor having a gate in electrical communication with the emission line, a source in electrical communication with OLED, and a drain in electrical communication with the data switching transistor.

11. (canceled)

17. A method of controlling an organic light-emitting diode (OLED) circuit in electrical communication with a data line, an emission line, a scan line, a high-power supply line and a low power supply line, comprising:

initializing the OLED circuit by applying a low voltage signal on the data line, and placing an anode of an OLED in electrical communication with the low voltage signal via a diode-connected transistor;

programming the OLED by applying a high voltage signal on the data line, and storing a reference voltage on a plate of a storage capacitor by charging the plate of the storage capacitor through a driving transistor of the OLED circuit, the reference voltage being a function of the high voltage signal applied on the data line and a threshold voltage of the driving transistor of the OLED circuit; and

energizing the OLED by applying a current through the OLED.

18. The method of claim 17, wherein the initializing the OLED circuit reverses the bias of the OLED.

19. The method of claim 17, wherein energizing the OLED comprises applying a current through the OLED which is independent of the threshold voltage of the driving transistor.

20. The method of claim 17, additionally comprising applying an emission signal on the emission line and simultaneously applying a scan signal on the scan line, wherein the emission signal is generated by driver circuitry in electrical communication with the OLED circuit, and wherein the scan signal is generated by the same driver circuitry.