Display apparatus, driving method thereof and electronic instrument

• US 9,153,169 B2
• Filed: 12/08/2008
• Issued: 10/06/2015
• Est. Priority Date: 01/15/2008
• Status: Active Grant

• Current Assignee: JDI Design and Development GK
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Yamashita, Junichi, Uchino, Katsuhide
• Primary Examiner(s): Sasinowski, Andrew
• Assistant Examiner(s): RAYAN, MIHIR K
• Application Number:
  US12/314,313
• Publication Number:
  US 20090179838A1
• Time in Patent Office: 2,493 Days
• US Class Current: 1/1
• CPC Class Codes: G09G 2300/0819 used for counteracting undesired variations, e.g. feedback or autozeroing
• CPC Class Codes: G09G 2300/0842 forming a memory circuit, e.g. a dynamic memory with one capacitor
• CPC Class Codes: G09G 2320/043 Preventing or counteracting the effects of ageing
• CPC Class Codes: G09G 3/3233 with pixel circuitry controlling the current through the light-emitting element

Abstract

An image display apparatus includes a pixel array section and a drive section configured to drive the pixel array section. The pixel array section is a pixel-circuit matrix with pixel circuits each serving as a matrix element. The drive section has at least a write scanner for supplying the control signal to each of the scan lines in order to carry out a sequential scanning operation on the scan lines for every field and a signal selector for supplying a video signal to each of the signal lines with a timing adjusted to the sequential scanning operation. Each of the pixel circuits employs at least a sampling transistor, a drive transistor, a signal holding capacitor and a light emitting device.

Claims

1. An image display apparatus comprising:

a plurality of pixel circuits arranged in a matrix configuration within a pixel array section, at least one of the pixel circuits including a sampling transistor, a drive transistor, a holding capacitor, and a light emitting device; and

a drive section configured to drive the pixel array section, the drive section being configured to carry out a sequential scanning operation on scan lines, with the drive section providing a predetermined reference potential and a video signal on signal lines according to the sequential scanning operation, wherein

the sampling transistor is connected to one of the signal lines to selectively provide the video signal and the predetermined reference potential to the holding capacitor,

the drive transistor includes a gate electrode, a first current electrode and a second current electrode, the gate electrode being coupled to the holding capacitor, the first current electrode being coupled to a power-supply line and the second current electrode being coupled to the light emitting device,

the sampling transistor enters a turned-on state in accordance with a control signal supplied by one of the scan lines to sample the video signal into the signal holding capacitor,

the drive transistor supplies the light emitting device with a driving current having a magnitude according to the video signal held by the signal holding capacitor,

the sampling transistor provides the predetermined reference potential to cause a transition from a light emission period to a non-light emission period,

the sampling transistor is in a turned-on state during a time period wherein a threshold voltage of the drive transistor is stored in the signal holding capacitor,

when the video signal is set at a white level, the predetermined reference potential causes the drive transistor to be put in a state of a maximum reverse bias, and

when the video signal is set at a black level, the predetermined reference potential causes drive transistor is put in a state of a minimum reverse bias.

2. The image display apparatus according to claim 1,

wherein the sampling transistor applies the predetermined reference potential to the gate electrode of the drive transistor to reverse an electric potential at the gate electrode of the drive transistor with respect to a fixed electric potential on the power supply line to put the drive transistor in a state of a reverse bias.

3. The image display apparatus according to claim 1,

wherein a ratio of the light emission period to the no-light emission period is adjusted such that a threshold-voltage change in a state of a forward bias of the drive transistor during the light emission period is canceled by a threshold-voltage change in a state of a reverse bias of the drive transistor during the no-light emission period.

4. The image display apparatus according to claim 1,

wherein, prior to an operation to sample the video signal, the driving current is flowed through the drive transistor until the drive transistor is put in a turned-off state and a voltage, which is appearing between the gate and the second current electrode of the drive transistor when the driving current flowing through the drive transistor is cut off, is stored in the signal holding capacitor in order to carry out a threshold-voltage compensation operation to compensate the drive transistor for an effect of variations in threshold voltage from pixel to pixel.

5. The image display apparatus according to claim 1,

wherein, when the sampling transistor is put in a turned-on state in order to store the video signal in the signal holding capacitor, the driving current flowing through the drive transistor is negatively fed back to the signal holding capacitor during a mobility compensation period determined in advance in order to compensate the drive transistor for an effect of variations in carrier mobility.

6. An electronic instrument comprising the image display apparatus according to claim 1.

7. The electronic instrument according to claim 6,

wherein the sampling transistor applies the predetermined reference potential to the gate electrode of the drive transistor to reverse an electric potential at the gate electrode of the drive transistor with respect to a fixed electric potential on the power supply line to put the drive transistor in a state of a reverse bias.

8. The electronic instrument according to claim 6,

wherein a ratio of the light emission period to the no-light emission period is adjusted such that a threshold-voltage change in a state of a forward bias of the drive transistor during the light emission period is canceled by a threshold-voltage change in a state of a reverse bias of the drive transistor during the no-light emission period.

9. The electronic instrument according to claim 6,

wherein, prior to an operation to sample the video signal, the driving current is flowed through the drive transistor until the drive transistor is put in a turned-off state and a voltage, which is appearing between the gate and the second current electrode of the drive transistor when the driving current flowing through the drive transistor is cut off, is stored in the signal holding capacitor in order to carry out a threshold-voltage compensation operation to compensate the drive transistor for an effect of variations in threshold voltage from pixel to pixel.

10. The electronic instrument according to claim 6,

wherein, when the sampling transistor is put in a turned-on state in order to store the video signal in the signal holding capacitor, the driving current flowing through the drive transistor is negatively fed back to the signal holding capacitor during a mobility compensation period determined in advance in order to compensate the drive transistor for an effect of variations in carrier mobility.

11. A method of driving an image display apparatus that includes a plurality of pixel circuits arranged in a matrix configuration within a pixel array section, at least one of the pixel circuits including a sampling transistor, a drive transistor, a holding capacitor, and a light emitting device, the drive transistor including a gate electrode, a first current electrode and a second current electrode, the gate electrode being coupled to the holding capacitor, the first current electrode of being coupled to a power-supply line and the second current electrode being coupled to the light emitting device, the image display apparatus further including a drive section configured to drive the pixel array section, the drive section being configured to carry out a sequential scanning operation on scan lines, with the drive section providing a predetermined reference potential and a video signal on signal lines according to the sequential scanning operation, the method comprising:

selectively providing the video signal and the predetermined reference potential to the holding capacitor through the sampling transistor;

causing the sampling transistor to enter a turned-on state in accordance with a control signal supplied by one of the scan lines to sample the video signal into the signal holding capacitor,

supplying, through the drive transistor, the light emitting device with a driving current having a magnitude according to the video signal held by the signal holding capacitor,

providing, by the sampling transistor, the predetermined reference potential to cause a transition from a light emission period to a non-light emission period, and

causing the sampling transistor to be in a turned-on state during a time period wherein a threshold voltage of the drive transistor is stored in the signal holding capacitor, wherein

when the video signal is set at a white level, the predetermined reference potential causes the drive transistor to be put in a state of a maximum reverse bias; and

when the video signal is set at a black level, the predetermined reference potential causes drive transistor is put in a state of a minimum reverse bias.

12. The method according to claim 11,

wherein the sampling transistor applies the predetermined reference potential to the gate electrode of the drive transistor to reverse an electric potential at the gate electrode of the drive transistor with respect to a fixed electric potential on the power supply line to put the drive transistor in a state of a reverse bias.

13. The method according to claim 11,

wherein a ratio of the light emission period to the no-light emission period is adjusted such that a threshold-voltage change in a state of a forward bias of the drive transistor during the light emission period is canceled by a threshold-voltage change in a state of a reverse bias of the drive transistor during the no-light emission period.

14. The method according to claim 11,

wherein, prior to an operation to sample the video signal, the driving current is flowed through the drive transistor until the drive transistor is put in a turned-off state and a voltage, which is appearing between the gate and the second current electrode of the drive transistor when the driving current flowing through the drive transistor is cut off, is stored in the signal holding capacitor in order to carry out a threshold-voltage compensation operation to compensate the drive transistor for an effect of variations in threshold voltage from pixel to pixel.

15. The method according to claim 11,

wherein, when the sampling transistor is put in a turned-on state in order to store the video signal in the signal holding capacitor, the driving current flowing through the drive transistor is negatively fed back to the signal holding capacitor during a mobility compensation period determined in advance in order to compensate the drive transistor for an effect of variations in carrier mobility.

16. An image display apparatus comprising:

a plurality of pixel circuits arranged in a matrix within a pixel array section, at least one of the pixel circuits including a first transistor, a second transistor, a holding capacitor, and a light emitting device, wherein

the first transistor is configured to provide a predetermined reference potential to the holding capacitor to cause a transition from a light emission period to a non-light emission period,

the second transistor is connected between a power-supply line and the light emitting device,

the second transistor is configured to supply a driving current having a magnitude according to a video signal held by the holding capacitor,

when the video signal is set at a white level, the second transistor is put in a state of a maximum reverse bias; and

when the video signal is set at a black level, the second transistor is put in a state of a minimum reverse bias.

17. The image display apparatus according to claim 16, wherein a ratio of the light emission period to the non-light emission period is adjusted such that a threshold-voltage change in a state of a forward bias of the second transistor during the light emission period is canceled by the threshold-voltage change in a state of a reverse bias of the second transistor during the non-light emission period.

18. The image display apparatus according to claim 16, wherein, prior to an operation to sample the video signal, the driving current is flowed through the second transistor until the second transistor is put in a turned-off state and a voltage, which is appearing between the gate and a second current electrode of the second transistor when the driving current flowing through the second transistor is cut off, is stored in the holding capacitor in order to carry out a threshold-voltage compensation operation to compensate the second transistor for an effect of variations in a threshold voltage from pixel to pixel.

19. The image display apparatus according to claim 16, wherein, when the first transistor is put in a turned-on state in order to store the video signal in the holding capacitor, the driving current flowing through the second transistor is negatively fed back to the holding capacitor during a mobility compensation period determined in advance in order to compensate the second transistor for an effect of variations in carrier mobility.