KR20060136068A - Current Sampling and hold Circuit and Display device - Google Patents

Abstract

According to the present invention, a switching thin film transistor is connected between a source and a power supply voltage to switch an input image signal current and a signal current sinked from an organic electroluminescent device, and is connected between the switching thin film transistor and a ground power supply by a first control signal. A driving thin film transistor for sinking a signal current from the organic light emitting diode into a ground power source and a first control signal connected between the driving thin film transistor and the ground power source and applied to a gate to output an input image signal current to the ground power source; A first switching unit, a second switching unit connected between the gate and the drain of the driving thin film transistor to activate the driving thin film transistor by a first control signal applied to the gate, and connected between the switching thin film transistor and the power supply voltage. The power supply voltage is transferred to the switching thin film transistor by the second control signal applied to the gate. It provides a location the third switching unit, and a current sample-and-hold circuit including a storage capacitor for storing data by the input video signal current.

Organic electroluminescence, current sample hold, sample hold, current sink

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 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 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 current sample holding circuit according to a second embodiment of the present invention.

7 is a circuit diagram of a current sample holding circuit according to a third embodiment of the present invention.

The present invention relates to a current sample holding circuit for supplying a signal current to a data line of an organic light emitting diode 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, a conventional current sample hold circuit 10 is connected to a pixel circuit 14 having four TFTs P1 to P4 and two capacitors C _st and C _boost through a data line 12. It was. The pixel circuit 14 is formed with a plurality of scan lines (select (m), boost (m), and emit (m)) for supplying a scan signal as well as a data line 12 for supplying a data signal.

In FIG. 1, only one conventional current sample hold circuit 10, a data line 12, and a pixel circuit 14 are briefly shown. However, in the conventional organic light emitting display device, a plurality of current sample hold circuits include a pixel circuit through the data lines. I was connected to the field.

The conventional current sample hold circuit 10 includes four p-channel MOS transistors TFTs (M1, M2, M4, M5), two n-channel TFTs (M3, M6), and one capacitor ( C _hold ). The A signal is applied to the gates of M2, M4, and M5 among the four p-channel TFTs, and the B signal is applied to the gates of the two n-channel TFTs M3 and M6.

In addition, the source of M2 was connected to the power supply voltage VDD1, and the drain of M2 was connected to the source of M1 and the capacitor C _hold . The drain of M1 was connected to the source of M3 and the source of M5, and the gate of M1 was connected to the capacitor C _hold and the source of M4. The drain of M3 was connected to ground voltage VSS2, and M4 and M5 were 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 uses a capacitor (C2) through a current flowing from the power supply voltage VDD1 to M2, M1, and M5 when M2, M1, and M5 are turned on. The input image signal current I _data1 was sampled to C _hold ). At this time, M3 must be turned off to sample and hold the input image signal current I _data1 to the capacitor C _hold through the current flowing to M2, M1, and M5.

When the A signal is applied while the input image signal current is sampled to the capacitor C _hold , and the B signal and the scan signal select [m] are applied, the data line 12, M6, The signal current (I _data2 ) flows through M1 and M1. 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 since emit (m) is turned on. The driving current I _oled was supplied to the organic light emitting diode.

Therefore, in the conventional current sample and hold circuit 10, M3 is necessary so that the input image signal current does not flow to the ground voltage when the input image signal current I _data1 is sampled to the capacitor C _hold .

As described above, the conventional current sample and hold circuit 10 has a large number of signal lines since M3 exists so that the input image signal current does not flow to the ground voltage when the input image signal current I _data1 is sampled to the capacitor C _hold . there was. 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.

In order to achieve the above technical problem, the present invention provides a switching thin film transistor for switching a source current connected to a power supply voltage and a signal current sinked from an organic electroluminescent device, between the switching thin film transistor and a ground power supply. A driving thin film transistor connected to sink the signal current from the organic light emitting diode to ground power by a first control signal, and an input image signal by a first control signal connected between the driving thin film transistor and ground power and applied to a gate; A first switching unit for outputting current to a ground power source, a second switching unit connected between the gate and the drain of the driving thin film transistor to activate the driving thin film transistor by a first control signal applied to the gate, and the switching thin film transistor Is connected between the power supply voltage and the power supply voltage by a second control signal applied to the gate. A current switching circuit including a third switching unit for switching a power supply voltage to a switching thin film transistor and a storage capacitor storing data by an input image signal current is provided.

In this case, the first control signal and the second control signal may be the same signal.

In addition, the switching thin film transistor, the driving thin film transistor, the first switching unit, the second switching unit and the third switching unit may be a p-channel MOS transistor (Metal Oxide Semiconductor Field Effect Transistor).

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 and stored the input image signal current when the data signal is applied through the data line When the scan signal is applied through the scan line provides a display device including a current sample holding circuit for sinking the signal current from the pixel circuit.

In this case, the pixel circuit unit may be configured of a plurality of organic light emitting diodes.

In this case, the current sample holding circuit includes a switching thin film transistor for switching the input image signal current and the signal current sinked from the organic electroluminescent device, the source being connected to the power supply voltage, and connected between the switching thin film transistor and the ground power source. A driving thin film transistor for sinking a signal current from the organic light emitting device into the ground power source by a control signal, and a first control signal connected to the gate of the driving thin film transistor and the ground power source to be applied to the gate to receive the input video signal current. A first switching unit outputting the ground power source, a second switching unit connected between the gate and the drain of the driving thin film transistor to activate the driving thin film transistor by a first control signal applied to the gate, the switching thin film transistor and the power supply The power supply voltage is switched by a second control signal applied to the gate because the voltage is connected between the voltages. A display device includes a third switching unit for switching a thin film transistor and a storage capacitor to store data by an input image signal current.

In this case, the first control signal and the second control signal may be the same signal.

In addition, the switching thin film transistor, the driving thin film transistor, the first switching unit, the second switching unit and the third switching unit may be a p-channel MOS transistor (Metal Oxide Semiconductor Field Effect Transistor).

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 hold circuit according to a first embodiment of the present invention for sample-holding an input image signal current and supplying a signal current to a data line of a current sinking type active matrix type organic light emitting display device. 4 is a signal waveform 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 TFT (S_TFT2, D_TFT2) which is four p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistors) through the data line 22. , S / W5, S / W4 and one pixel C _stg are connected to the pixel circuit 24. In the pixel circuit 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 light emitting display device including the current sample holding circuit according to the first embodiment of the present invention is illustrated. A plurality of current sample hold circuits are connected to the pixel circuits through the data lines.

In this case, the current sample hold circuit 20 includes TFTs (S_TFT1, D_TFT1, S / W1 to S / W3, S / W6), which are six p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistors), and one capacitor (C _hold). Has A signal is applied to the gates of S / W3, S / W2, and S / W1 among the six p-channel TFTs, and a B signal is applied to the gates of one p-channel TFT (S / W6). Also, since the B signal is applied to only one p-channel TFT, the current sample holding circuit 20 according to the first embodiment of the present invention reduces one signal line compared with the conventional current sample holding circuit 10 of FIG. Can be.

In addition, the source of S / W3 is connected to the power supply voltage VDD1, and the drain of M2 is connected to the source and capacitor C _hold of S_TFT1. The drain of S_TFT1 is connected to the source of D_TFT1 and the drain of S / W2, and the gates of S_TFT1 and D_TFT1 are connected to the capacitor C _hold and the source of S / W2. The drain of D_TFT1 was connected to ground voltage GND2, and the drain of S / W1 was connected to another ground voltage GND1 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.

3 and 4, in the current sample hold circuit 20 according to the first exemplary embodiment of the present invention, S / W1 to S / W3 are first turned on when an A signal is applied. At this time, when S / W2 is turned on, the source and gate of D_TFT1 have the same voltage, so the source-gate voltage Vgs of D_TFT1 becomes "0" and D_TFT1 is automatically turned off.

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

Referring to FIG. 5A, as a result, when the A signal is applied, the input image signal current I _data1 is sampled in the capacitor C _hold through the current flowing from the power supply voltage VDD to S / W3, S_TFT1, and S / W1. It is held.

Referring to FIG. 5B, when the input image signal current is sampled to the capacitor C _hold , the A signal is erased. When the B signal and the scan signal select (m) are applied, the data line from the pixel circuit 24 is applied. (22), the signal current I _data2 flows to S_TFT1 and D_TFT1. At this time, an operating point for enabling S_TFT1 and D_TFT1 to be determined is determined, and D_TFT1 is automatically turned on. At this time, as the signal current I _data2 flows, data is stored in the storage capacitor C _stg of the pixel circuit 24.

As a result, the current sample hold circuit 20 according to the first embodiment of the present invention is automatically turned off when the D_TFT1 is applied to the A signal and turned on when the B signal is applied to control a separate signal for controlling the D_TFT1. No lines are required. 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 current sample holding circuit according to a second embodiment of the present invention.

Referring to FIG. 6, the current sample hold circuit 30 according to the second embodiment of the present invention is connected to a pixel circuit through a data line and includes six p-channel TFTs (S_TFT1, D_TFT1, S / W1 to S /). W3, S / W6) and one capacitor C _hold are the same as in the first embodiment.

In addition, the current sample hold circuit 30 according to the second embodiment of the present invention has the same connection relationship between six p-channel TFTs (S_TFT1, D_TFT1, S / W1 to S / W3, and S / W6). The source of W2 and the source of S / W1 are connected, and the drain of S / W2 is connected to the voltage source, and the drain of S / W1 is connected to the source of D_TFT1.

4 and 6, in the current sample hold circuit 30 according to the second embodiment of the present invention, when an A signal is applied, S / W1 to S / W3 are first turned on, and a source and a gate of D_TFT1 are turned on. Since the same voltage has the same voltage, the source-gate voltage Vgs of D_TFT1 becomes "0" and D_TFT1 is automatically turned off.

Similarly to the first embodiment, when the resultant A signal is applied, the input image signal current I _data1 is applied to the capacitor C _hold through the current flowing from the power supply voltage VDD to S / W3, S_TFT1, and S / W1. Sample is held.

When the A signal is applied while the input image signal current is sampled to the capacitor C _hold , and the B signal and the scan signal select (m) are applied, the data line 22, S_TFT1, The signal current I _data2 flows to D_TFT1. At this time, an operating point for enabling S_TFT1 and D_TFT1 to be determined is determined, and D_TFT1 is automatically turned on. At this time, as the signal current (I _data2 ) flows, data is stored in the storage capacitor C _stg of the pixel circuit.

Example 3

7 is a circuit diagram of a current sample hold circuit according to a third embodiment of the present invention.

Referring to FIG. 7, the current sample holding circuit 40 according to the third embodiment of the present invention is basically the same as the first and second embodiments.

However, in the current sample hold circuit 40 according to the third embodiment of the present invention, the gates of S / W2 and S / W1 are connected, the source of S / W1 is connected to the source of D_TFT1, and S / W2. The source of is connected to the gate of S_TFT1. On the other hand, the drains of D_TFT1 and S_TFT1 differ from the first and second embodiments in that they are connected in common with the voltage source.

4 and 6, in the current sample hold circuit 40 according to the third embodiment of the present invention, the source and gate voltage of D_TFT1 are equal when the A signal is applied in the same manner as the first and second embodiments. When D_TFT1 is automatically turned on and B signal is applied, there is no signal line that is automatically turned off and connected to D_TFT1.

 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 the above embodiments, it has been described that S / W1 to S / W3 apply the same A signal, but S / W1 and S / W3 apply the same A signal and S / W2 applies another signal that is turned off first. You may. Even if different signals are applied to S / W1, S / W3, and S / W2, when turned on at the same time, D_TFT1 is automatically turned off and then turned on so that a signal line connected to a separate D_TFT1 is not needed.

In the above embodiments, it has been described that one AC sample holding circuit is connected to one pixel circuit, but two or three pixel circuits are formed in one AC sample holding circuit by configuring one to two or one to three demux. May be connected. As described above, since one to two or one to three demuxes are configured in the data driver of the organic light emitting display device, the number of pins of the data driver can be further reduced.

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.

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

Claims (8)

A switching thin film transistor having a source connected to the power supply voltage and switching the input image signal current and the signal current sinked from the organic electroluminescent element; A driving thin film transistor connected between the switching thin film transistor and a ground power source to sink the signal current from the organic light emitting diode to the ground power by a first control signal; A first switching unit connected between the driving thin film transistor and the ground power source and outputting the input image signal current to the ground power source by the first control signal applied to a gate; A second switching unit connected between the gate and the drain of the driving thin film transistor to activate the driving thin film transistor by the first control signal applied to the gate; A third switching unit connected between the switching thin film transistor and the power supply voltage to switch the power supply voltage to the switching thin film transistor according to a second control signal applied to a gate; And a storage capacitor configured to store data by the input image signal current. The method of claim 1, And the first control signal and the second control signal are the same signal. The method of claim 1, And the switching thin film transistor, the driving thin film transistor, the first switching unit, the second switching unit and the third switching unit are p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistor). A pixel circuit unit formed at a position where the data line and the scan line cross each other; It is 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 the 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 4, wherein And the pixel circuit unit is configured of a plurality of organic light emitting diodes. The method of claim 5, The current sample hold circuit, A switching thin film transistor having a source connected to the power supply voltage and switching the input video signal current and the signal current sinked from the organic electroluminescent device; A driving thin film transistor connected between the switching thin film transistor and a ground power source to sink the signal current from the organic light emitting diode to the ground power by a first control signal; A first switching unit connected between the driving thin film transistor and the ground power source and outputting the input image signal current to the ground power source by the first control signal applied to a gate; A second switching unit connected between the gate and the drain of the driving thin film transistor to activate the driving thin film transistor by the first control signal applied to the gate; A third switching unit connected between the switching thin film transistor and the power supply voltage to switch the power supply voltage to the switching thin film transistor by a second control signal applied to a gate; And a storage capacitor configured to store data by the input image signal current. The method of claim 6, And the first control signal and the second control signal are the same signal. The method of claim 7, wherein And the switching thin film transistor, the driving thin film transistor, the first switching unit, the second switching unit, and the third switching unit are p-channel MOS transistors (Metal Oxide Semiconductor Field Effect Transistor).

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