Display apparatus, method of driving a display, and electronic device

• US 20080198104A1
• Filed: 02/19/2008
• Published: 08/21/2008
• Est. Priority Date: 02/21/2007
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Tomida, Masatsugu, Uchino, Katsuhide, Yamashita, Junichi
• Granted Patent: US 7,880,695 B2
• Time in Patent Office: Days
• US Class Current: 345/77
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• 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 2310/0289 Details of voltage level shifters arranged for use in a driving circuit
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/0233 Improving the luminance or brightness uniformity across the screen
• CPC Class Codes: G09G 3/3208 organic, e.g. using organic light-emitting diodes [OLED]
• 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 5/10 Intensity circuits
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H10K 50/824 combined with auxiliary electrodes
• CPC Class Codes: H10K 50/841 Self-supporting sealing arrangements
• CPC Class Codes: H10K 50/8426 Peripheral sealing arrangements, e.g. adhesives, sealants
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/1216 the pixel elements being capacitors
• CPC Class Codes: H10K 59/123 Connection of the pixel electrodes to the thin film transistors [TFT]
• CPC Class Codes: H10K 59/124 Insulating layers formed between TFT elements and OLED elements
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals
• CPC Class Codes: H10K 59/38 comprising colour filters or colour changing media [CCM]
• CPC Class Codes: H10K 59/871 Self-supporting sealing arrangements

Abstract

In a display apparatus including a correction unit and a switching transistor, the correction unit operates in a non-light emission period such that a correction voltage for eliminating an effect of a variation in a characteristic of a driving transistor is stored in a storage capacitor. The switching transistor is disposed between one current terminal of the driving transistor and a light emitting element. The switching transistor turns off during the non-light emission period thereby to electrically disconnect the light emitting element from the one current terminal of the driving transistor thereby preventing a leakage current from flowing through the light emitting element during the period in which the correction unit operates, and thus preventing the correction voltage from having an error due to the leakage current.

Claims

1. A display apparatus comprising:

a pixel array; and

a driving unit adapted to drive the pixel array, the pixel array including scanning lines disposed in the form of rows, signal lines disposed in the form of columns, and pixels disposed, in the form of an array, at respective intersections of the scanning lines and the signal lines,

each pixel including at least a sampling transistor, a driving transistor, a light emitting element, and a storage capacitor,

a control terminal of the sampling transistor being connected to a corresponding scanning line, one of two current terminals of the sampling transistor being connected to a corresponding signal line and the control terminal of the driving transistor,

one of two current terminals of the driving transistor being connected to the light emitting element and the other one being connected to a power supply line,

the storage capacitor being connected between the control terminal and one of the two current terminals of the driving transistor,

the driving unit being configured to output a control signal over a selected scanning line to turn on the sampling transistor connected to the selected scanning line, and output an image signal over a selected signal line to write the image signal in the storage capacitor via the turned-on sampling transistor,

whereby the driving transistor supplies a driving current, depending on a signal voltage of the written image signal, to the light emitting element during a predetermined light emission period, while the driving transistor supplies no driving current during a non-light emission period,

each pixel including correction means and a switching transistor,

the correction means being adapted to operate in the non-light emission period so as to write a correction voltage in the storage capacitor thereby to eliminate an effect of a variation in a characteristic of the driving transistor,

the switching transistor being disposed between one of the two current terminals of the driving transistor and the light emitting element, and the switching transistor being adapted to turn off during the non-light emission period thereby to electrically disconnect the light emitting element from the one the two current terminals of the driving transistor thereby preventing a leakage current from flowing through the light emitting element during the period in which the operates and thus preventing the correction voltage from having an error due to the leakage current.

2. The display apparatus according to claim 1, wherein the correction means additively writes a correction voltage corresponding to a threshold voltage of the driving transistor into the storage capacitor so as to eliminate an effect of a variation in the threshold voltage of the driving transistor.

3. The display apparatus according to claim 1, wherein the correction means subtracts a correction voltage depending on a mobility of the driving transistor from the signal voltage of the image signal written in the storage capacitor so as to eliminate an effect of a variation in the mobility of the driving transistor.

5. An electronic device including a display apparatus according to claim 1.

4. A method of driving a display apparatus,

the display apparatus including a pixel array and a driving unit adapted to drive the pixel array,

the pixel array including scanning lines disposed in the form of rows, signal lines disposed in the form of columns, and pixels disposed, in the form of an array, at respective intersections of the scanning lines and the signal lines,

each pixel including at least a sampling transistor, a driving transistor, a switching transistor, a light emitting element, and a storage capacitor,

a control terminal of the sampling transistor being connected to a corresponding scanning line, one of two current terminals of the sampling transistor being connected to a corresponding signal line and the control terminal of the driving transistor,

one of two current terminals of the driving transistor being connected to the light emitting element and the other one being connected to a power supply line,

the switching transistor being disposed between one of the two current terminals of the driving transistor and the light emitting element,

the storage capacitor being connected between the control terminal and one of the two current terminals of the driving transistor,

the driving unit being configured to output a control signal over a selected scanning line to turn on the sampling transistor connected to the selected scanning line, and output an image signal over a selected signal line to write the image signal in the storage capacitor via the turned-on sampling transistor,

whereby the driving transistor supplies a driving current, depending on a signal voltage of the written image signal, to the light emitting element during a predetermined light emission period, while the driving transistor supplies no driving current during a non-light emission period,

the method comprising the steps of:

performing a correction process for eliminating an effect of a variation in a characteristic of the driving transistor in the non-light emission period, the correction process including writing a correction voltage into the storage capacitor from one of two current terminals of the driving transistor; and

turning off the switching transistor during the non-light emission period thereby to electrically disconnect the light emitting element from the one the two current terminals of the driving transistor thereby preventing a leakage current from flowing through the light emitting element and thus preventing the correction voltage from having an error due to the leakage current.

6. A display apparatus comprising:

a pixel array; and

a driving unit adapted to drive the pixel array,

the pixel array including scanning lines disposed in the form of rows, signal lines disposed in the form of columns, and pixels disposed, in the form of an array, at respective intersections of the scanning lines and the signal lines,

each pixel including at least a sampling transistor, a driving transistor, a light emitting element, and a storage capacitor,

a control terminal of the sampling transistor being connected to a corresponding scanning line, one of two current terminals being connected to a corresponding signal line and the control terminal of the driving transistor,

one of two current terminals of the driving transistor being connected to the light emitting element and the other one being connected to a power supply line,

the storage capacitor being connected between the control terminal and one of the two current terminals of the driving transistor,

the driving unit being configured to output a control signal over a selected scanning line to turn on the sampling transistor connected to the selected scanning line, and output an image signal over a selected signal line to write the image signal in the storage capacitor via the turned-on sampling transistor,

whereby the driving transistor supplies a driving current, depending on a signal voltage of the written image signal, to the light emitting element during a predetermined light emission period, while the driving transistor supplies no driving current during a non-light emission period,

each pixel including a correction unit and a switching transistor,

the correction unit being adapted to operate in the non-light emission period so as to write a correction voltage in the storage capacitor thereby to eliminate an effect of a variation in a characteristic of the driving transistor,

the switching transistor being disposed between one of the two current terminals of the driving transistor and the light emitting element, and the switching transistor being adapted to turn off during the non-light emission period thereby to electrically disconnect the light emitting element from the one the two current terminals of the driving transistor thereby preventing a leakage current from flowing through the light emitting element during the period in which the correction unit operates and thus preventing the correction voltage from having an error due to the leakage current.