Display apparatus

• US 8,416,158 B2
• Filed: 07/08/2009
• Issued: 04/09/2013
• Est. Priority Date: 07/15/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Seto, Yasuhiro
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): XAVIER, ANTONIO J
• Application Number:
  US12/499,593
• Publication Number:
  US 20100013746A1
• Time in Patent Office: 1,371 Days
• Field of Search: None
• US Class Current: 345/76
• 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 2300/0866 by means of changes in the pixel supply voltage
• CPC Class Codes: G09G 2310/0254 Control of polarity reversal in general, other than for liquid crystal displays
• 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

In a display apparatus that includes an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor, and a threshold voltage of the drive transistor is corrected by causing the capacitor element to hold the threshold voltage of the drive transistor, reverse bias voltages, each having a magnitude corresponding to a preset initial threshold voltage and a drive voltage of the drive transistor, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, are supplied to the gate terminal of the drive transistor.

Claims

1. A display apparatus, comprising:

an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor with a source terminal connected to an anode terminal of the light emitting element to apply a drive current to the light emitting element, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor connected between the gate terminal of the drive transistor and a data line through which a predetermined data signal flows;

a control unit that corrects a threshold voltage of the drive transistor by supplying a predetermined voltage to the gate terminal of the drive transistor to cause a current to flow through the drive transistor and charging a capacitive load connected to the source terminal of the drive transistor with the current, thereby causing the capacitor element to hold the threshold voltage of the drive transistor; and

a data drive circuit that supplies negative reverse bias voltages, each having a magnitude corresponding to a preset initial threshold voltage and a drive voltage of the drive transistor prior to the threshold voltage being corrected, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, to the gate terminal of the drive transistor;

wherein the data drive circuit is a circuit that performs the following;

setting a limit value for the reverse bias voltages;

comparing a reverse bias voltage to be supplied to the gate terminal of the drive transistor with the limit value;

if the reverse bias voltage is greater than the limit value, subtracting the limit value from the reverse bias voltage to obtain a difference voltage; and

sequentially carrying over and adding the difference voltage to a next reverse bias voltage to be supplied to the gate terminal of the drive transistor.

2. The display apparatus of claim 1, wherein the limit value has a magnitude corresponding to 15% to 50% of the drive voltage of the drive transistor when the light emitting element is at maximum luminance.

3. The display apparatus of claim 1, wherein the drive transistor is an n-type thin film transistor of IGZO (InGaZnO).

4. The display apparatus of claim 1, wherein the data drive circuit supplies a drive voltage dependent on the amount of emission of the light emitting element to the gate terminal of the drive transistor following correction of the threshold voltage.

5. A display apparatus, comprising:

an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor with a source terminal connected to an anode terminal of the light emitting element to apply a drive current to the light emitting element, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor connected between the gate terminal of the drive transistor and a data line through which a predetermined data signal flows; and

a control unit that corrects a threshold voltage of the drive transistor by supplying a predetermined voltage to the gate terminal of the drive transistor to cause a current to flow through the drive transistor and charging a capacitive load connected to the source terminal of the drive transistor with the current, thereby causing the capacitor element to hold the threshold voltage of the drive transistor, wherein;

the drive transistor is an n-type thin film transistor with a threshold voltage Vth of nearly 0V; and

the apparatus further includes a data drive circuit that supplies negative reverse bias voltages, each having a magnitude corresponding to a drive voltage of the drive transistor prior to the threshold value being corrected, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, to the gate terminal of the drive transistor;

wherein the data drive circuit is a circuit that performs the following;

setting a limit value for the reverse bias voltages;

comparing a reverse bias voltage to be supplied to the gate terminal of the drive transistor with the limit value;

if the reverse bias voltage is greater than the limit value, subtracting the limit value from the reverse bias voltage to obtain a difference voltage; and

sequentially carrying over and adding the difference voltage to a next reverse bias voltage to be supplied to the gate terminal of the drive transistor.

6. The display apparatus of claim 5, wherein the limit value has a magnitude corresponding to 15% to 50% of the drive voltage of the drive transistor when the light emitting element is at maximum luminance.

7. The display apparatus of claim 5, wherein the drive transistor is an n-type thin film transistor of IGZO (InGaZnO).

8. The display apparatus as defined in claim 5, wherein the data drive circuit supplies a drive voltage dependent on the amount of emission of the light emitting element to the gate terminal of the drive transistor following correction of the threshold voltage.

9. A display apparatus, comprising an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor with a source terminal connected to an anode terminal of the light emitting element to apply a drive current to the light emitting element, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor connected between the gate terminal of the drive transistor and a data line through which a predetermined data signal flows, wherein:

the drive transistor is an n-type thin film transistor with a threshold voltage Vth of nearly 0V; and

the apparatus further includes a data drive circuit that supplies negative reverse bias voltages, each having a magnitude corresponding to a drive voltage of the drive transistor prior to the threshold value being corrected, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, to the gate terminal of the drive transistor;

wherein the data drive circuit is a circuit that performs the following;

setting a limit value for the reverse bias voltages;

comparing a reverse bias voltage to be supplied to the gate terminal of the drive transistor with the limit value;

if the reverse bias voltage is greater than the limit value, subtracting the limit value from the reverse bias voltage to obtain a difference voltage; and

sequentially carrying over and adding the difference voltage to a next reverse bias voltage to be supplied to the gate terminal of the drive transistor.

10. The display apparatus of claim 9, wherein the limit value has a magnitude corresponding to 15% to 50% of the drive voltage of the drive transistor when the light emitting element is at maximum luminance.

11. The display apparatus of claim 9, wherein the drive transistor is an n-type thin film transistor of IGZO (InGaZnO).

12. A display apparatus, comprising:

an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor with a source terminal connected to an anode terminal of the light emitting element to apply a drive current to the light emitting element, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor connected between the gate terminal of the drive transistor and a data line through which a predetermined data signal flows;

a control unit that corrects a threshold voltage of the drive transistor by supplying a predetermined voltage to the gate terminal of the drive transistor to cause a current to flow through the drive transistor and charging a capacitive load connected to the source terminal of the drive transistor with the current, thereby causing the capacitor element to hold the threshold voltage of the drive transistor; and

a data drive circuit that supplies negative reverse bias voltages, each having a magnitude corresponding to a preset initial threshold voltage and a drive voltage of the drive transistor prior to the threshold voltage being corrected, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, to the gate terminal of the drive transistor;

wherein

the magnitude Vry of the reverse bias voltage is set to satisfy the following formula

Vrv=(Vth0+Vodx)·

Tdsp/Try

with respect to an initial threshold voltage Vth0 of the drive transistor, a drive voltage Vodx of the drive transistor dependent on the amount of emission of the light emitting element, a light emission period Tdsp of the light emitting element, and a supply period Try of the reverse bias voltage.

13. A display apparatus, comprising:

an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor with a source terminal connected to an anode terminal of the light emitting element to apply a drive current to the light emitting element, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor connected between the gate terminal of the drive transistor and a data line through which a predetermined data signal flows; and

a control unit that corrects a threshold voltage of the drive transistor by supplying a predetermined voltage to the gate terminal of the drive transistor to cause a current to flow through the drive transistor and charging a capacitive load connected to the source terminal of the drive transistor with the current, thereby causing the capacitor element to hold the threshold voltage of the drive transistor, wherein;

the drive transistor is an n-type thin film transistor with a threshold voltage Vth of nearly 0V; and

the apparatus further includes a data drive circuit that supplies negative reverse bias voltages, each having a magnitude corresponding to a drive voltage of the drive transistor prior to the threshold value being corrected, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, to the gate terminal of the drive transistor;

wherein

the magnitude Vrv of the reverse bias voltage is set to satisfy the following formula

Vrv=(Vth0+Vodx)·

Tdsp/Try

with respect to an initial threshold voltage Vth0 of the drive transistor, a drive voltage Vodx of the drive transistor dependent on the amount of emission of the light emitting element, a light emission period Tdsp of the light emitting element, and a supply period Try of the reverse bias voltage.

14. A display apparatus, comprising an active matrix substrate on which multiple pixel circuits are disposed, each having a light emitting element, a drive transistor with a source terminal connected to an anode terminal of the light emitting element to apply a drive current to the light emitting element, a capacitor element connected between a gate terminal and the source terminal of the drive transistor, and a selection transistor connected between the gate terminal of the drive transistor and a data line through which a predetermined data signal flows, wherein:

the drive transistor is an n-type thin film transistor with a threshold voltage Vth of nearly 0V; and

the apparatus further includes a data drive circuit that supplies negative reverse bias voltages, each having a magnitude corresponding to a drive voltage of the drive transistor prior to the threshold value being corrected, the magnitude of the drive voltage being dependent on the amount of emission of the light emitting element, to the gate terminal of the drive transistor;

wherein

the magnitude Vry of the reverse bias voltage is set to satisfy the following formula

Vrv=(Vth0+Vodx)·

Tdsp/Trv

with respect to an initial threshold voltage Vth0 of the drive transistor, a drive voltage Vodx of the drive transistor dependent on the amount of emission of the light emitting element, a light emission period Tdsp of the light emitting element, and a supply period Try of the reverse bias voltage.