KR20070019396A - Current Sampling and hold Circuit and Display device - Google Patents

Abstract

The present invention is connected between a power supply voltage and a ground voltage to sink an input image signal current from a power supply voltage to a ground voltage by a first control signal, and to sink a signal current from a light emitting element to a ground voltage by a second control signal. Between the driving thin film transistor, a first switch connected between the power supply voltage and the driving thin film transistor and applying a first control signal to the gate, a first switch supplying an input image signal current to the driving thin film transistor, and between the gate and the drain of the driving thin film transistor. A second switch connected to the first control signal to turn on the driving thin film transistor when the first control signal is applied to the gate, and corresponding to the input video signal current when the driving thin film transistor sinks the input video signal current by the first control signal. A hold capacitor for storing the data voltage and a connection between the driving thin film transistor and the light emitting device Control and provides a second current first sample-and-hold circuit including three seuwichingreul when applying a control signal to sink a signal current corresponding to the data voltage stored in the holding capacitor through the driving thin film transistor from the light emitting element to the gate.

Organic electroluminescence, current sample hold, sample hold, current source

Description

Current sample hold circuit and display device including same {Current Sampling and hold Circuit and Display device}

1 is a circuit diagram of a current sample holding circuit of a conventional organic light emitting display device.

2 is a signal waveform diagram of the current sample hold circuit of FIG.

3 is a circuit diagram of a current sample holding circuit of an organic light emitting display device according to a first embodiment of the present invention;

4 is a signal waveform diagram of the current sample hold circuit of FIG.

5A and 5B are driving state diagrams of the current sample hold circuit of FIG. 3 by the signal waveform of FIG.

6 is a circuit diagram of a display device including a current sample hold circuit according to a second embodiment of the present invention.

7 is a signal waveform diagram of the display device of FIG. 6.

The present invention relates to a current sample holding circuit for supplying a signal current to a data line of a light emitting device by sampling and holding an input image signal current, and a display device including the same.

Organic light emitting diodes (OLEDs) were self-luminous devices that emit fluorescent materials by recombination of electrons and holes. The organic light emitting display device including the organic light emitting display device is a wall-mounted or portable device because the response speed is faster, the DC driving voltage is lower, and the ultra-thin film is possible than the passive light emitting device which requires a separate light source like the liquid crystal display device. Application was possible.

Such an organic light emitting display device implements color using pixels in which red, blue, and green subpixels represent one color. At this time, the organic light emitting diode is an active matrix organic light emitting diode (active matrix) which is a method of driving using a simple matrix type organic light emitting diode (PMOLED) and a thin film transistor (TFT) as a method of driving a subpixel. OLED, AMOLED).

As the driving method of the active matrix organic light emitting diode (AMOLED), there are a current driving method, a voltage driving method, and a digital driving method. In addition, the current driving method was divided into a current source type (current source type) and a current sink type (current sink type).

The current sink type active matrix organic light emitting display device includes a current sample holding circuit for sample-holding an input video signal current and supplying a signal current to a data line of the organic light emitting display device.

FIG. 1 is a circuit diagram of a conventional current sample holding circuit for sampling and holding an input image signal current to supply a signal current to a data line of a current sink type active matrix organic light emitting display device.

Referring to FIG. 1, the conventional current sample hold circuit 10 is connected to a pixel circuit unit 14 having four thin film transistors P1 to P4 and two capacitors C _st and C _boost through the data line 12. I was connected. In the pixel circuit unit 14, not only the data line 12 supplying the data signal but also a plurality of scan lines select (m), boost (m), and emit (m) for supplying the scan signal are formed. At this time, the parasitic capacitor having a capacitance 20 to 30 times larger than the two capacitors C _st and C _boost of the pixel circuit unit 14 exists in the data line 12. Therefore, the conventional current sample hold circuit 10 cannot store the data voltage in two capacitors (C _st and C _boost ) of the pixel circuit unit 14 after sufficiently charging the parasitic capacitor of the data line 12. Existed.

In addition, in FIG. 1, only one conventional current sample holding circuit 10, a data line 12, and a pixel circuit 14 are briefly illustrated. However, in the conventional organic light emitting display device, a plurality of current sample holding circuits include a plurality of data lines. Connected to the pixel circuits. Therefore, the problem that the conventional sample hold circuit 10 cannot store the data voltage in the two capacitors (C _st and C _boost ) of the pixel circuit unit 14 has been increased.

On the other hand, the conventional current sample hold circuit 10 is the first, second, fourth, and fifth thin film transistors (M1, M2, M4, M5) and two four p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistor) The third and sixth thin film transistors M3 and M6, which are n-channel MOS transistors, and one capacitor C _hold . At this time, the A signal is applied to the gates of the second thin film transistor M2 and the fourth and fifth thin film transistors M4 and M5, and the B signal is applied to the gates of the third and sixth thin film transistors M3 and M6.

The second thin film transistor M2 was connected between the power supply voltage VDD1 and the first thin film transistor M1. The first thin film transistor M1 is connected between the second thin film transistor M2 and the third thin film transistor M3, and the gate is connected to the capacitor C _hold and the fourth thin film transistor M4. The drain of the third thin film transistor M3 is connected to the ground voltage VSS2, and the fourth thin film transistor M4 and the fifth thin film transistor M5 are connected to another ground voltage VSS1 through a current source. .

2 illustrates signal waveforms of the current sample hold circuit of FIG. 1. Hereinafter, the current sample holding operation of the conventional current sample holding circuit 10 will be described with reference to the signal waveforms of FIG. 2.

Referring to FIGS. 1 and 2, when the A signal is applied, the conventional current sample hold circuit 10 turns on the power supply voltage by turning on the second thin film transistor M2 and the first and fifth thin film transistors M1 and M5. The input image signal current I _data1 was sampled to the capacitor C _hold through the current flowing from the VDD1) to the second thin film transistor M2 and the first and fifth thin film transistors M1 and M5. At this time, the third thin film transistor M3 must be turned off so that the input image signal current I _data1 is input to the capacitor C _hold through the current flowing to the second thin film transistor M2 and the first and fifth thin film transistors M1 and M5. ) Can be sampled.

When the input image signal current is sampled to the capacitor C _hold and the A signal is applied, and the B signal and the scan signal select [m] are applied, the data line 12 and the sixth line from the pixel circuit 14 are applied. The signal current I _data2 flows through the second and third thin film transistors M6, M1, and M3. As the signal current (I _data2 ) flows, data is stored in the storage capacitor C _st of the pixel circuit 14. The data stored in the storage capacitor C _st is organic light emitting diode OLED because P4 is turned on. The driving current I _oled was supplied to the organic light emitting diode OLED.

Accordingly, the conventional thin film transistor M3 needs a third thin film transistor M3 so that the input video signal current does not flow to the ground voltage when the input video signal current I _data1 is sampled to the capacitor C _hold . It was.

As described above, in the conventional current sample and hold circuit 10, when the input image signal current I _data1 is sampled to the capacitor C _hold , the third thin film transistor M3 exists so that the input image signal current does not flow to the ground voltage. There were many problems with the signal line.

Although only one current sample hold circuit 10 is illustrated in FIG. 1, as described above, since a plurality of current sample hold circuits exist in the organic light emitting display device, the conventional organic light emitting display device includes a data driver including a current sample hold circuit. This caused a problem of increasing the number of pins. As the number of pins in the data driver increases, the price of the data driver increases.

In particular, the increase in the number of pins of the conventional organic light emitting display device causes more serious problems in high resolution.

The present invention has been made to solve the above problems, and an object of the present invention is to provide a current sample holding circuit which can minimize the number of signal lines.

Another object of the present invention is to provide an organic light emitting display device capable of providing a high resolution image by reducing the number of pins of the data driver.

Another object of the present invention is to provide a display device capable of sufficiently charging a data voltage to a storage capacitor.

In order to achieve the above technical problem, the present invention is connected between a power supply voltage and a ground voltage to sink the input image signal current from the power supply voltage to the ground voltage by the first control signal, and from the light emitting element by the second control signal. A driving thin film transistor for sinking a signal current with a ground voltage, a first switch connected between a power supply voltage and the driving thin film transistor, and supplying an input image signal current to the driving thin film transistor as a first control signal is applied to a gate; A second switch connected between the gate and the drain of the thin film transistor and turning on the driving thin film transistor as the first control signal is applied to the gate; and the driving thin film transistor sinks the input image signal current by the first control signal. A hold capacitor that stores a data voltage corresponding to an input video signal current when A current sample and hold circuit including a third switch connected between the transistor and the light emitting element and sinking a signal current corresponding to the data voltage stored in the hold capacitor from the light emitting element through the driving thin film transistor when the second control signal is applied to the gate; To provide.

In this case, the driving thin film transistor and the first to third switches may be p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistors).

In another aspect, the present invention, the pixel circuit portion formed at the intersection of the data line and the scan line, and connected to the pixel circuit portion through the data line, when the data signal is applied through the data line to store the input image signal current When the scan signal is applied through the scan line, the display device includes a current sample hold circuit that sinks a signal current from the pixel circuit.

On the other hand, the current sample holding circuit is connected between the power supply voltage and the ground voltage to sink the input image signal current from the power supply voltage to the ground voltage by the first control signal, and the signal from the light emitting element to the ground voltage by the second control signal. A driving thin film transistor for sinking current, a first switch connected between the power supply voltage and the driving thin film transistor and supplying an input image signal current to the driving thin film transistor as a first control signal is applied to the gate, and a gate of the driving thin film transistor; A second switch connected between the drain and the drain and turning on the driving thin film transistor as the first control signal is applied to the gate; and when the driving thin film transistor sinks the input image signal current by the first control signal. Hold capacitors for storing data voltages corresponding to signal currents, driving thin film transistors, and light emitting elements Is connected between, and when applied to the second control signal to the gate voltage corresponding to the data stored in the hold capacitor through the driving thin film transistor from the light emitting element and may comprise a third seuwichingreul to sink a signal current.

The driving thin film transistor and the first to third switches may be p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistors).

In this case, two or more sample hold circuits may be connected to one organic light emitting diode so that two or more sample hold circuits may alternately sink a signal current from the light emitting diode.

Also, when any one of the two or more sample hold circuits sinks the signal current, the other one or two of the two or more sample hold circuits may sink the input image signal current to sample the data.

In addition, the light emitting device may be an organic light emitting device.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Example 1

3 is a circuit diagram of a current sample holding circuit of an organic light emitting display device according to a first embodiment of the present invention, which samples and holds an input image signal current and supplies a signal current to a data line of a current source type active matrix organic light emitting display device. 4 is a signal waveform diagram of the current sample hold circuit of FIG. 3.

Referring to FIG. 3, the current sample hold circuit 20 according to the first embodiment of the present invention is a thin film transistor S_TFT2, which is a four p-channel MOS transistor (Metal Oxide Semiconductor Field Effect Transistor) through the data line 22. D_TFT2, S / W5, S / W4 and a pixel circuit section 24 including a plurality of organic light emitting elements having one capacitor C _stg . In the pixel circuit section 24, not only the data line 22 for supplying the data signal but also the scan line select (m) for supplying the scan signal are connected to the gates of S / W4 and S / W5.

In FIG. 3, only one current sample holding circuit 20, a data line 22, and a pixel circuit 24 are briefly illustrated. However, the organic field including the current sample holding circuit 20 according to the first embodiment of the present invention is illustrated. In the light emitting display device, a plurality of current sample holding circuits 20 are connected to the pixel circuit units 24 through a plurality of data lines 22.

3 and 4, the current sample hold circuit 20 includes four driving thin film transistors D_TFT1 and four first to third switches S / W1 to four p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistors). S / W3) and one hold capacitor (C _hold ). In the current sample hold circuit 20 according to the first embodiment of the present invention, the first control signal A signal is applied to the gates of the first and second switches S / W1 and S / W2, and the third switch Since the second control signal (B signal) is applied only to the gate of S / W3, one signal line can be reduced as compared with the conventional current sample hold circuit 10 of FIG.

The driving thin film transistor D_TFT1 is formed between the first switch S / W1 and the ground voltage.

The first switch S / W1 is formed at the power supply voltage VDD, the driving current source I_data, and the driving thin film transistor D_TFT1, and the first control signal A signal is applied to the gate. When the first control signal A signal is applied to the gate, the first switch S / W1 supplies the input image signal current I _data1 to the driving thin film transistor D_TFT1 from the driving current source I_data.

The second switch S / W2 is formed between the gate and the drain of the driving thin film transistor D_TFT1 and a first control signal A signal is applied to the gate. When the first control signal A signal is applied to the gate, the second switch S / W2 automatically turns on the driving thin film transistor D_TFT1 to sink the input image signal current I _data1 .

The hold capacitor C _hold is connected between the source and the gate of the driving thin film transistor D_TFT1 The hold capacitor C _hold is an input video signal current when the driving thin film transistor D_TFT1 sinks the input video signal current. The data voltage corresponding to (I _data1 ) is held.

The third switch S / W3 is formed on the data line 22 between the pixel circuit unit 24 and the driving thin film transistor D_TFT1 and the second control signal B signal is applied to the gate. When the second control signal is applied to the gate, the third switch S / W3 sinks the signal current I _data2 corresponding to the data voltage held by the hold capacitor C _hold from the pixel circuit unit 24.

5A and 5B are driving state diagrams of the current sample hold circuit of FIG. 3 by the signal waveform of FIG.

4 and 5A, as a result, when the first control signal A signal is applied, the first switch S / W1 is driven from the power supply voltage VDD and the drive current source I_data. The input image signal current I _data1 is supplied to the D_TFT1, and the second switch S / W2 activates the driving thin film transistor D_TFT1. In this way, the driving current source I_data is connected to the source terminal of the driving thin film transistor to sample and hold data and to supply the signal current I _data2 .

The driving thin film transistor D_TFT1 sinks the input image signal current I _data1 with the ground voltage GND. At this time, the hold capacitor C _hold samples the data voltage corresponding to the input image signal current.

Referring to FIG. 5B, the second control signal (B signal) is applied to the gate of the third switch S / W3 of the sample hold circuit 20 while the input image signal current is sampled and held by the capacitor C _hold . When the scan signal select (m) is applied to the pixel circuit unit 34, the signal current I _data2 flows from the pixel circuit 24 to the data line 22 and the driving thin film transistor D_TFT1.

At this time, the driving thin film transistor D_TFT1 sinks the signal current I _data2 corresponding to the data voltage held in the hold capacitor C _hold . Sample-and-hold circuit 20 is stored jeonapga data corresponding to the signal current (I _data2) to the storage capacitor (C _stg) in the pixel circuit 24. When a sync signal current (I _data2).

As a result, in the current sample hold circuit 20 according to the first embodiment of the present invention, the driving thin film transistor D_TFT1 is automatically turned on when the first control signal A signal is automatically applied. There is no need for a separate signal line to control (D_TFT1). Therefore, the current sample hold circuit 20 according to the first embodiment of the present invention can reduce the number of signal lines while performing the same operation as the conventional current sample hold circuit 10.

Example 2

6 is a circuit diagram of a display device including a current sample hold circuit according to a second embodiment of the present invention, and FIG. 7 is a signal waveform diagram of the display device of FIG.

Referring to FIG. 6, the display device 28 including the current sample hold circuit according to the second exemplary embodiment of the present invention includes a plurality of sample hold circuits 30a, 30b, 32a, 32b,... Between the organic light emitting diodes 40, 42, ..., and the sample holding circuits 30a, 30b, 32a, 32b, ... and the organic light emitting diodes 40, 42, ... It includes a plurality of data lines 50, 52,...

The plurality of sample hold circuits 30a, 30b, 32a, 32b, ... are the same as, but not limited to, the current sample circuit 20 according to the first embodiment of the present invention.

The plurality of organic light emitting diodes 40, 42,... Are also the same as, but not limited to, the organic light emitting diode of the pixel circuit unit 24 shown in FIG. 3.

In this case, the pair of sample and hold circuits 30a and 30b are connected to one organic light emitting diode 40 through one data line 50. The other pair of sample and hold circuits 32a and 32b are also connected to one organic light emitting diode 42 through one data line 52. The connection relationship between the omitted sample hold circuits, the organic light emitting diode, and the data line is the same.

6 and 7, the first control signals A1, A2, ... are sequentially one of a pair of sample hold circuits, for example, sample hold circuits 30a, 32a, .... The data is held in the hold capacitor (C _hold ) when it is applied. The second control signals DA are then applied to one of the pair of sample hold circuits, for example, the sample hold circuits 30a, 32a, ..., and the organic light emitting diodes 40, 42,. When the scan signal Scan (N-1) is applied to the ..), signal currents from the organic light emitting diodes 40, 42,... Are sample hold circuits 30a, 32a,... The data voltage is stored in the storage capacitor while being sinked.

When the scan signal Scan (N-1) is applied, the other first control signals B1, B2,... Are sequentially arranged in another one of the pair of sample hold circuits, for example, the sample hold circuit ( 30b, 32b, ....) to sample and hold the data to the hold capacitor (C _hold ).

As such, when one of the pair of sample hold circuits (30a, 32a, ...) sinks the signal current, the other one of the pair of sample hold circuits (30b, 32b, ...) holds the data. This provides enough time for the signal current to charge the storage capacitors of the organic light emitting diodes 40, 42,... As a result, the charging time is sufficiently secured, so that the parasitic capacitor of the data line and the storage capacitor of the pixel circuit part can be sufficiently charged.

In the above, embodiments of the present invention have been described in detail with reference to the drawings, but the present invention is not limited thereto.

In Embodiments 1 and 2, one or two sample holding circuits are connected to one organic light emitting diode, but three or more sample holding circuits are connected to one organic light emitting diode to hold the data. And sequentially charging the data voltage. Accordingly, the parasitic capacitor of the data line and the storage capacitor of the pixel circuit unit may be sufficiently charged.

In Examples 1 and 2, the sample hold circuit is described as driving a pixel circuit unit including a plurality of organic light emitting diodes. However, another device, for example, an inorganic light emitting diode (LED), may be driven.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may be embodied in other specific forms without changing the technical spirit or essential features of the present invention. I can understand that. Therefore, since the embodiments described above are provided to fully inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

By such a configuration, the present invention has the effect of minimizing the number of signal lines of the current sample hold circuit.

In addition, the present invention has the effect of providing a high resolution image by reducing the number of pins of the data driver.

In addition, the present invention has the effect of sufficiently charging the data voltage to the storage capacitor.

Accordingly, the organic light emitting display device can be compact and the price can be lowered.

Claims (8)

A driving thin film connected between a power supply voltage and a ground voltage to sink an input image signal current from the power supply voltage to the ground voltage by a first control signal and to sink the signal current from the light emitting element to the ground voltage by a second control signal A transistor; A first switch connected between the power supply voltage and the driving thin film transistor and supplying the input image signal current to the driving thin film transistor as the first control signal is applied to a gate; A second switch connected between the gate and the drain of the driving thin film transistor and turning on the driving thin film transistor as the first control signal is applied to the gate; A hold capacitor configured to store a data voltage corresponding to the input video signal current when the driving thin film transistor sinks an input video signal current according to the first control signal; A third control signal connected to the driving thin film transistor and the light emitting device and configured to sink the signal current corresponding to the data voltage stored in the hold capacitor from the light emitting device through the driving thin film transistor when a second control signal is applied to a gate; A current sample hold circuit including switching. The method of claim 1, And the driving thin film transistor and the first to third switches are p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistors). A pixel circuit unit formed at a position where the data line and the scan line cross each other; Connected to the pixel circuit unit through the data line. When a data signal is applied through the data line, an input image signal current is stored. When a scan signal is applied through the scan line, the signal current is sinked from the pixel circuit. A display device comprising a current sample hold circuit. The method of claim 3, The current sample hold circuit, A connection between a power supply voltage and a ground voltage to sink the input video signal current from the power supply voltage to the ground voltage by a first control signal, and to sink the signal current from the light emitting element to the ground voltage by a second control signal. A driving thin film transistor; A first switch connected between the power supply voltage and the driving thin film transistor and supplying the input image signal current to the driving thin film transistor as the first control signal is applied to a gate; A second switch connected between the gate and the drain of the driving thin film transistor and turning on the driving thin film transistor as the first control signal is applied to the gate; A hold capacitor configured to store a data voltage corresponding to the input video signal current when the driving thin film transistor sinks an input video signal current according to the first control signal; A third control signal connected to the driving thin film transistor and the light emitting element and configured to sink the signal current corresponding to the data voltage stored in the storage capacitor through the driving thin film transistor from the light emitting element when a second control signal is applied to a gate; Display comprising switching. The method of claim 4, wherein The driving thin film transistor and the first to third switches are p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistor). The method according to any one of claims 3 to 5, And the at least two sample hold circuits are connected to one light emitting device so that the at least two sample hold circuits alternately sink the signal current from the light emitting device. The method of claim 6, And when one of the two or more sample hold circuits sinks the signal current, the other one or more of the two or more sample hold circuits sinks the input image signal current to sample and hold data. Device. The method of claim 6, The light emitting device is an organic light emitting display device, characterized in that.

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