LIGHT EMITTING DISPLAY DEVICE
First Claim
1. A light emitting display device comprising a pixel having a light emitting device and a drive circuit for driving the light emitting device, the drive circuit comprising:
- a first thin film transistor and a second thin film transistor having the same polarity, a gate terminal of the first thin film transistor being connected to a gate terminal of the second thin film transistor, a source terminal of the first thin film transistor being connected to a source terminal of the second thin film transistor, and the source terminals of the first thin film transistor and the second thin film transistor being connected to one end of the light emitting device;
a first switch having one end connected to the source terminals of the first thin film transistor and the second thin film transistor and to one end of the light emitting device and having the other end connected to a first line; and
a capacitor having one end connected to the gate terminals of the first thin film transistor and the second thin film transistor and having the other end connected to the source terminals of the first thin film transistor and the second thin film transistor,wherein the drive circuit has at least a first period for writing a drive signal and a second period for driving the light emitting device after the first period,wherein the first period contains a period in which the first line and the one end of the light emitting device are set to the same voltage through the first switch, and a second line for supplying the drive signal of the light emitting device is electrically connected to a drain terminal of the first thin film transistor and the gate terminals of the first thin film transistor and the second thin film transistor, to supply a current to the first thin film transistor from the second line, andwherein the second period contains a period in which connection between the second line and the first thin film transistor, connection between the second line and the second thin film transistor, and the first switch are shut off.
1 Assignment
0 Petitions
Accused Products
Abstract
A light emitting display device using a drive circuit formed of only unipolar thin film transistors, which suppresses effects of characteristic shifts of transistors, and is applicable to large, high-resolution light emitting displays. The device includes a pixel having an organic EL device (LED) and a drive circuit thereof. In a current writing period, the drive circuit sets TFT3, TFT4 and TFT5 ON and sets a ground line and one end of LED to the same voltage through TFT3. A current from a data line is supplied to transistors L-TFT and D-TFT forming a current mirror circuit through TFT4 and TFT5, and a voltage between gate and source terminals of L-TFT and D-TFT is retained in a capacitor. During a LED driving period, TFT3, TFT4 and TFT5 are interrupted, and a current flowing between the source and drain of D-TFT is supplied to LED according to the retaining voltage.
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Citations
17 Claims
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1. A light emitting display device comprising a pixel having a light emitting device and a drive circuit for driving the light emitting device, the drive circuit comprising:
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a first thin film transistor and a second thin film transistor having the same polarity, a gate terminal of the first thin film transistor being connected to a gate terminal of the second thin film transistor, a source terminal of the first thin film transistor being connected to a source terminal of the second thin film transistor, and the source terminals of the first thin film transistor and the second thin film transistor being connected to one end of the light emitting device; a first switch having one end connected to the source terminals of the first thin film transistor and the second thin film transistor and to one end of the light emitting device and having the other end connected to a first line; and a capacitor having one end connected to the gate terminals of the first thin film transistor and the second thin film transistor and having the other end connected to the source terminals of the first thin film transistor and the second thin film transistor, wherein the drive circuit has at least a first period for writing a drive signal and a second period for driving the light emitting device after the first period, wherein the first period contains a period in which the first line and the one end of the light emitting device are set to the same voltage through the first switch, and a second line for supplying the drive signal of the light emitting device is electrically connected to a drain terminal of the first thin film transistor and the gate terminals of the first thin film transistor and the second thin film transistor, to supply a current to the first thin film transistor from the second line, and wherein the second period contains a period in which connection between the second line and the first thin film transistor, connection between the second line and the second thin film transistor, and the first switch are shut off. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
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2. A light emitting display device comprising a pixel having a light emitting device and a drive circuit for driving the light emitting device, the drive circuit comprising:
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a first thin film transistor and a second thin film transistor having the same polarity, a gate terminal of the first thin film transistor being connected to a gate terminal of the second thin film transistor, a source terminal of the first thin film transistor being connected to a source terminal of the second thin film transistor, and the source terminals of the first thin film transistor and the second thin film transistor being connected to one end of the light emitting device; a first switch having one end connected to the source terminals of the first thin film transistor and the second thin film transistor and to one end of the light emitting device and having the other end connected to a first line; and a capacitor having one end connected to the gate terminals of the first thin film transistor and the second thin film transistor and having the other end connected to the source terminals of the first thin film transistor and the second thin film transistor, the drive circuit has at least a first period for writing a drive signal and a second period for driving the light emitting device after the first period, wherein, during the first period, the first line and one end of the light emitting device are set to the same voltage through the first switch, and a current from a second line for supplying the drive signal of the light emitting device is supplied to a drain terminal of the first thin film transistor and the gate terminals of the first thin film transistor and the second thin film transistor to retain in the capacitor a voltage between the gate terminal and the source terminal of the second thin film transistor which is determined based on a current flowing between the drain terminal and the source terminal of the first thin film transistor, and wherein, during the second period, a current flowing between the source terminal and the drain terminal of the second thin film transistor is supplied to the light emitting device according to a retaining voltage of the capacitor. - View Dependent Claims (3)
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Specification