CN101866619B - Pixel circuit of organic light emitting diode, display and driving method thereof - Google Patents

Abstract

An organic light emitting diode pixel circuit and its display and driving method. The pixel circuit proposed in the present invention adopts a 3T2C architecture (that is, three thin film transistors plus two capacitors), and after the circuit state is driven by the corresponding scanning signal and data signal, the brightness presented by the pixel circuit is only related to the data signal, and has nothing to do with the threshold voltage of the transistor driving the light emitting component, the system high voltage received by the pixel circuit, and the cross voltage of the anode and cathode of the light emitting component, thereby effectively improving/solving the problem of uneven display of the organic light emitting diode panel.

Description

Pixel circuit of organic light emitting diode, display and driving method thereof

technical field

The present invention relates to a plane display technology, and in particular to a pixel circuit of an organic light emitting diode display and a driving method thereof.

Background technique

In recent years, the development of flat-panel display technology has continued to innovate. Among them, organic light emitting diode (OLED), also known as organic electroluminescence (OEL), has advantages that other flat-panel display technologies are difficult to achieve. New generation technology, including power saving, ultra-thin thickness, light weight, self-illumination, no viewing angle limit, fast response, high photoelectric efficiency, no need for backlight structure and color filter structure, high contrast, high luminance efficiency, high brightness , multi-color and color (RGB) component manufacturing capabilities, and a wide range of operating temperatures are considered to be one of the most promising flat-panel display technologies in the future.

Today's OLED displays can be broadly classified into passive matrix (PM) OLED displays and active matrix (AM) OLED displays. The driving method of the former is mainly to use scanning means/mechanism to generate high brightness instantly, so the power consumption is high, the components are easy to deteriorate, and it is not suitable for the development of high-resolution panels; in addition, the main driving method of the latter is to use thin film transistors ( TFT) components, and with capacitors to store different data signals, so as to control the gray scale of each pixel on the panel.

After the AMOLED display is scanned, the pixels can still maintain the original brightness, and the AMOLED display does not need to be driven to a very high brightness. Therefore, compared with the PMOLED display, the AMOLED display can not only achieve a better lifetime performance, but also meet the requirement of high resolution. Therefore, current research is all directed toward AMOLED displays that can be used for large panels.

As shown in FIG. 1 , the pixel circuit 100 of a conventional AMOLED display mostly adopts a 2T1C structure, that is, two thin film transistors T1 and T2 plus a single capacitor C. Generally speaking, the pixel circuit 100 is driven by the scan signal Vscan and the data signal Vdata to emit light, and the displayed brightness is proportional/inversely proportional to the intensity of the data signal Vdata.

In practice, since the system high voltage OVDD of each pixel circuit 100 in the AMOLED display is connected together, when each pixel circuit 100 is driven by its corresponding scan signal Vscan and data signal Vdata, due to the The current on the line that transmits the system high voltage OVDD will produce a voltage drop effect with the impedance of the line itself. In this way, the system high voltage OVDD received by each pixel circuit 100 will be different.

In addition, due to the influence of the manufacturing process, the threshold voltage (threshold voltage, Vth) of the thin film transistor T2 used to drive the organic light emitting diode (OLED) OD in each pixel circuit 100 may be different. Therefore, in response to the fact that the system high voltage OVDD received by each pixel circuit 100 is different and the threshold voltage of the thin film transistor T2 used to drive the organic light emitting diode (OLED) OD in each pixel circuit 100 is different, the Even if the same data signal Vdata is applied to each pixel circuit 100, the current flowing through the organic light-emitting diode (OLED) OD of each pixel circuit 100 will be different, so that the brightness displayed by each pixel circuit 100 will also be different. , and this is also the main reason that affects the display non-uniformity of the OLED panel.

Contents of the invention

In view of the problems faced by the prior art, the object of the present invention is to provide a pixel circuit of an organic light emitting diode (OLED) display and a driving method thereof, so as to effectively improve/solve the problem of display non-uniformity of the OLED panel.

The present invention provides a pixel circuit, which includes a first transistor, a second transistor, a third transistor, a first capacitor, a second capacitor, and a light emitting element (OLED). Wherein, the gate of the first transistor is used for receiving the first scan signal, and the first drain or source of the first transistor is used for receiving the data signal. The gate of the second transistor is used for receiving the second scan signal, and the first drain or source of the second transistor is used for receiving the reference signal. The first end of the first capacitor is electrically connected to the second drain or source of the first transistor, and the second end of the first capacitor is electrically connected to the second drain or source of the second transistor. The gate of the third transistor is electrically connected to the second drain or source of the first transistor, the first drain or source of the third transistor is electrically connected to the first voltage, and the second drain or source of the third transistor is connected to the first voltage. Electrically connected to the second drain or source of the second transistor. The first end of the second capacitor is electrically connected to the first drain or source of the third transistor, and the second end of the second capacitor is electrically connected to the second drain or source of the third transistor. The first terminal of the light-emitting component is electrically connected to the second drain or the source of the third transistor, and the second terminal of the light-emitting component is electrically connected to the second voltage.

In an embodiment of the present invention, the first terminal and the second terminal of the light-emitting component are respectively an anode and a cathode, and the first voltage and the second voltage are respectively a system high voltage and a system low voltage. Under this condition, the first, second and third transistors are N-type transistors respectively.

In another embodiment of the present invention, the first terminal and the second terminal of the light-emitting component are respectively a cathode and an anode, and the first voltage and the second voltage are respectively a system low voltage and a system high voltage. Under this condition, the first, second and third transistors are P-type transistors respectively.

The present invention further provides a display with the above-mentioned pixel circuit provided by the present invention.

The present invention also proposes a driving method suitable for driving the above-mentioned pixel circuit proposed by the present invention, which includes: resetting the voltage level between the gate of the third transistor and the second drain or source during the reset period of the frame period. During the storage period of the same frame period, record the threshold voltage of the third transistor; during the writing period of the same frame period, write the data signal to the light emitting component; and during the light emitting period of the same frame period, only respond to the data signal and Causes the light-emitting component to emit light.

Based on the above, the pixel circuit proposed by the present invention adopts a 3T2C structure (that is, three thin film transistors plus two capacitors), and its circuit configuration is driven by the corresponding scanning signal and data signal, which will cause the pixel The brightness presented by the circuit is only related to the data signal, and has nothing to do with the threshold voltage of the transistor driving the light-emitting component, the system high voltage received by the pixel circuit, and the cross-voltage of the anode and cathode of the light-emitting component, thus effectively improving/solving OLED panels. Problems showing non-uniformity.

Description of drawings

1 is a schematic diagram of a pixel circuit of a conventional active matrix organic light emitting diode (AMOLED) display;

2A is a system block diagram of an organic light emitting diode (OLED) display according to an embodiment of the present invention;

FIG. 2B is a driving waveform diagram of the pixel circuit in FIG. 2A;

3A to 3D are schematic diagrams of the operation of the pixel circuit in FIG. 2A;

4A is a system block diagram of an organic light emitting diode (OLED) display according to another embodiment of the present invention;

FIG. 4B is a driving waveform diagram of the pixel circuit in FIG. 4A;

5A is a system block diagram of an organic light emitting diode (OLED) display according to yet another embodiment of the present invention;

FIG. 5B is a driving waveform diagram of the pixel circuit in FIG. 5A .

[Description of main component symbols]

100, Pix, Pix': pixel circuit

200, 400, 500: Organic light-emitting diode (OLED) displays

210: timing controller

220: data drive device

230, 240, 510: scanning drive device

250, 250': display panel

260: Reference signal generating device

A, B: node

C, C1, C2: capacitance

T1～T3, T1’～T3’: Transistor

OD: Organic Light Emitting Diode/Light-Emitting Component

DL: data line

SL1, SL2: scan lines

Vscan, Vscan1, Vscan2, Vscan1’, Vscan2’: scanning signal

Vdata: data signal

Vsus: reference signal

VD, VD(N-1), VD(N): data voltage

VR: reference voltage

OVDD: System high voltage

OVSS: System Low Voltage

P1: Reset period

P2: storage period

P3: during writing

P4: Luminescence period

Detailed ways

Reference will now be made in detail to the exemplary embodiments of the present invention, examples of which are illustrated in the accompanying drawings. In addition, wherever possible, components/members using the same reference numerals in the drawings and embodiments represent the same or similar parts.

FIG. 2A is a system block diagram of an organic light emitting diode (OLED) display according to an embodiment of the present invention. Please refer to FIG. 2A, the OLED display 200 includes a timing controller (timing controller, T-con) 210, a data driving device (data driving device) 220, a scanning driving device (scan driving device) 230 and 240, a display panel (display panel) 250, and a reference signal generating device (reference signal generating device) 260.

In this embodiment, the display panel 250 includes at least one data line DL, at least two scan lines SL1 and SL2, and at least one pixel circuit Pix. Wherein, the data line DL is electrically connected to the data driving device 220 for receiving the data signal Vdata provided by the data driving device 220 controlled by the timing controller 210 . The scan line SL1 is electrically connected to the first scan driving device 230 for receiving the scan signal Vscan1 provided by the scan driving device 230 controlled by the timing controller 210 . The scan line SL2 is electrically connected to the scan driving device 240 for receiving the second scan signal Vscan2 provided by the scan driving device 240 controlled by the timing controller 210 .

On the other hand, the pixel circuit Pix includes transistors T1 - T3 (such as thin film transistors), capacitors C1 and C2 , and a light emitting element OD. Wherein, the transistors T1 - T3 are N-type transistors, and the light-emitting component OD is an organic light-emitting diode (OLED). In this embodiment, the gate of the N-type transistor T1 is electrically connected to the scan line SL1 to receive the scan signal Vscan1; and the drain of the N-type transistor T1 is electrically connected to the data line DL to receive the data signal. Vdata. The gate of the N-type transistor T2 is electrically connected to the scan line SL2 to receive the scan signal Vscan2 ; and the drain of the N-type transistor T2 is used to receive the reference signal Vsus provided by the reference signal generating device 260 .

A first end of the capacitor C1 is electrically connected to the source of the N-type transistor T1, and a second end of the capacitor C1 is electrically connected to the source of the N-type transistor T2. The gate of the N-type transistor T3 is electrically connected to the source of the N-type transistor T1, the drain of the N-type transistor T3 is electrically connected to the system high voltage OVDD, and the source of the N-type transistor T3 is electrically connected to the N-type transistor T2 source. The first end of the capacitor C2 is electrically connected to the drain of the N-type transistor T3, and the second end of the capacitor C2 is electrically connected to the source of the N-type transistor T3. The anode of the light emitting device OD is electrically connected to the source of the N-type transistor T3, and the cathode of the light emitting device OD is electrically connected to the system low voltage OVSS.

Based on the above, the operation of the pixel circuit Pix will be described in detail below for reference to those skilled in the field of the present invention.

FIG. 2B is a driving waveform diagram of the pixel circuit Pix in FIG. 2A . 3A to 3D are schematic diagrams of the operation of the pixel circuit Pix in FIG. 2A . Please refer to FIG. 2B first. In this embodiment, a frame period of the OLED display 200 is composed of a reset period (reset period) P1, a storage period (storing period) P2, and a writing period (writing period) P3. And the emission period (emission period) P4.

Next, please refer to FIG. 2B and FIG. 3A together. During the reset period P1, since the scanning signals Vscan1 and Vscan2 are both in the enable state, the N-type transistors T1 and T2 are both turned on. At this time, the data driving device 220 will provide the data signal Vdata with the reference voltage VR to the pixel circuit Pix, so as to pre-charge the pixel circuit Pix, and reset the voltage of the gate of the N-type transistor T3 quasi-position. On the other hand, the reference signal generating device 260 provides the reference signal Vsus to the pixel circuit Pix to reset the voltage level of the source of the N-type transistor T3. Wherein, the voltage level of the reference voltage VR is greater than the voltage level of the reference signal Vsus. In this way, the voltage level of the node A (that is, the gate voltage of the N-type transistor T3) is equal to the voltage level of the reference voltage VR; and the voltage level of the node B (that is, the source voltage of the N-type transistor T3) It is equal to the voltage level of the reference signal Vsus.

Next, please refer to FIG. 2B and FIG. 3B together. During the storage period P2, since the scanning signals Vscan1 and Vscan2 are in the enabled and disabled states respectively, the N-type transistor T1 will remain on, and the N-type transistor T1 will remain on. Transistor T2 is turned off. At this time, since the data driving device 220 will continue to provide the data signal Vdata with the reference voltage VR to the pixel circuit Pix, the voltage level of the node A is still equal to the voltage level of the reference voltage VR, and the voltage level of the node B is equal to VR-Vth, the capacitor C1 records the threshold voltage (Vth) of the N-type transistor T3. Wherein, VR is the voltage level of the reference voltage VR; and Vth is the threshold voltage of the N-type transistor T3.

Afterwards, please refer to FIG. 2B and FIG. 3C together. During the writing period P3, since the scanning signals Vscan1 and Vscan2 are in the enabled and disabled states respectively, the N-type transistor T1 will remain on, and the N-type transistor T2 will be turned on. Stay closed. At this time, because the data driving device 220 will turn to provide the data signal Vdata with the data voltage VD to the pixel circuit Pix (that is, provide the data signal Vdata with the data voltage VD to the gate of the N-type transistor T3), so that the node A The voltage level of the node B is changed to the voltage level of the data voltage VD, and the voltage level of the node B is equal to VR−Vth+a*(VD−VR). Wherein, a=C1/(C1+C2); C1 is the capacitance of the capacitor C1; C2 is the capacitance of the capacitor C2; and VD is the voltage level of the data voltage VD.

Finally, please refer to FIG. 2B and FIG. 3D together. During the light-emitting period P4, since the scanning signals Vscan1 and Vscan2 are both in a disabled state, the N-type transistors T1 and T2 are both turned off. At this time, the voltage level of the node A is equal to VD+Voled+OVSS-a*(VD-VR)+Vth-VR, and the voltage level of the node B is equal to Voled+OVSS. Wherein, Voled is the voltage across the anode and cathode of the light-emitting element OD. In this way, the current flowing through the light-emitting element OD is equal to K*[(1-a)*(VD-VR)]2. Wherein, K is a manufacturing process parameter related to the N-type transistor T3, which is generally a constant.

It can be seen that, during the light-emitting period P4, the magnitude of the current flowing through the light-emitting element OD is only related to the data signal Vdata having the reference voltage VR and the data voltage VD (that is, the light-emitting element OD only emits light in response to the data signal Vdata), and is related to The pixel circuit Pix is used to drive the threshold voltage (Vth) of the N-type transistor T3 of the light-emitting device OD, the received system high voltage OVDD, and the anode-cathode voltage (Voled) of the light-emitting device OD are irrelevant. Therefore, the pixel circuit Pix of this embodiment can effectively improve/solve the problem of display non-uniformity of the OLED panel 250 .

The pixel circuit Pix in the above embodiment is realized by three N-type transistors T1 - T3 and two capacitors C1 and C2 , but the present invention is not limited thereto.

FIG. 4A is a system block diagram of an organic light emitting diode (OLED) display 400 according to another embodiment of the present invention, and FIG. 4B is a driving waveform diagram of the pixel circuit Pix' in FIG. 4A. Please refer to FIG. 4A and FIG. 4B together. The difference between the OLED displays 200 and 400 lies in the structure of the display panels 250 and 250'. In this embodiment, the pixel circuit Pix' in the display panel 250' and the pixel circuit Pix in the display panel 250 have a complementary structure. To be clearer, the pixel circuit Pix' is realized by three P-type transistors T1-T3 and two capacitors C1 and C2. In this way, this embodiment only needs to invert the scanning signals Vscan1 and Vscan2 in FIG. 2B into the scanning signals Vscan1' and Vscan2' in FIG. 4B respectively to drive the pixel circuit Pix' to achieve the similarity to the previous embodiment. Similar technical effects are not repeated here.

On the other hand, in the above embodiment, the two scan driving devices 230 and 240 respectively provide the scan signals Vscan1 (or Vscan1') and Vscan2 (or Vscan2') to drive the N-type transistors T1 and T2 (or the P-type transistor T1' T2') is taken as an example for description, but the present invention is not limited thereto.

FIG. 5A is a system block diagram of an organic light emitting diode (OLED) display according to another embodiment of the present invention, and FIG. 5B is a driving waveform diagram of the pixel circuit Pix in FIG. 5A . Please refer to FIG. 5A and FIG. 5B together. The difference between OLED displays 200 and 500 is that OLED display 500 has only one scanning driving device 510, and this scanning driving device 510 can use any existing shift temporary memory mechanism/means to generate scan signals Vscan1 and Vscan2. In this way, the implementation of the scan driving device 510 is easier than that of the scan driving devices 230 and 240 , and its manufacturing cost is relatively low.

In this embodiment, if the pixel circuit Pix is driven by the scanning signals Vscan1 and Vscan2 provided by the scanning driving device 510 and the data signal Vdata provided by the data driving device 220, a technique similar/similar to the above embodiment can also be achieved. effect, and therefore will not be repeated here.

However, it is worth mentioning here that if the pixel circuit Pix is driven by the scanning signals Vscan1 and Vscan2 and the data signal Vdata as shown in FIG. 5B , the only result different from the driving method in FIG. During the set period P1, the voltage level of the node A is equal to the voltage level of the data signal Vdata having the data voltage VD(N−1), instead of the voltage level of the reference voltage VR as in the previous embodiment. Besides, in the other periods P2-P4, the respective voltage levels of the nodes A and B are the same as the previous embodiment. In FIG. 5B , the symbol VD(N−1) represents the data voltage of the previous data signal Vdata; and the symbol VD(N) represents the data voltage of the current data signal Vdata.

In summary, the pixel circuit (Pix/Pix') proposed by the present invention adopts a 3T2C structure (that is, three N-type/P-type thin film transistors plus two capacitors), and its circuit configuration is subject to After corresponding scan signal (Vscan1/Vscan1' and Vscan2/Vscan2') and data signal (Vdata) are driven, the brightness presented by the pixel circuit is only related to the data signal, and not related to the transistor driving the light-emitting device (OLED). The threshold voltage (Vth) of the pixel circuit, the system high voltage (OVDD) received by the pixel circuit, and the anode-cathode voltage (Voled) of the light-emitting component are irrelevant, thereby effectively improving/solving the problem of OLED panel display non-uniformity.

Although the present invention has been disclosed above with the embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be determined by the scope defined in the claims.

Claims (10)

1. the image element circuit of an Organic Light Emitting Diode is characterized in that, comprising:

One the first transistor, the grid of described the first transistor be in order to receiving one first sweep signal, and in the leakage of described the first transistor or the source electrode one is in order to receive a data-signal;

One transistor seconds, the grid of described transistor seconds be in order to receiving one second sweep signal, and in the leakage of described transistor seconds or the source electrode one is in order to receive a reference signal;

One first electric capacity, the first end of described the first electric capacity are electrically connected the leakage of described the first transistor or in the source electrode another, and the second end of described the first electric capacity is electrically connected the leakage of described transistor seconds or in the source electrode another;

One the 3rd transistor, the described the 3rd transistorized grid is electrically connected the leakage of described the first transistor or in the source electrode another, one in the described the 3rd transistorized leakage or the source electrode is electrically connected to one first voltage, and in the described the 3rd transistorized leakage or the source electrode another is electrically connected the leakage of described transistor seconds or in the source electrode another;

One second electric capacity, the first end of described the second electric capacity are electrically connected in the described the 3rd transistorized leakage or the source electrode, and the second end of described the second electric capacity is electrically connected in the described the 3rd transistorized leakage or the source electrode another; And

One luminescence component, the first end of described luminescence component are electrically connected another in the described the 3rd transistorized leakage or the source electrode, and the second end of described luminescence component is electrically connected to a second voltage.

2. image element circuit as claimed in claim 1 is characterized in that, the first end of described luminescence component and the second end are respectively an anode and a negative electrode, and described the first voltage and described second voltage are respectively a system high voltage and a system low-voltage.

3. image element circuit as claimed in claim 2 is characterized in that, described the first transistor, described transistor seconds and described the 3rd transistor are respectively a N-type transistor.

4. image element circuit as claimed in claim 1 is characterized in that, the first end of described luminescence component and the second end are respectively a negative electrode and an anode, and described the first voltage and described second voltage are respectively a system low-voltage and a system high voltage.

5. image element circuit as claimed in claim 4 is characterized in that, described the first transistor, described transistor seconds and described the 3rd transistor are respectively a P transistor npn npn.

6. the display of an Organic Light Emitting Diode is characterized in that, comprising:

One display panel, described display panel comprises:

At least one data line is in order to receive a data-signal;

At least one the first sweep trace and one second sweep trace receive respectively one first sweep signal and one second sweep signal; And

At least one image element circuit, described image element circuit comprises:

One the first transistor, the grid of described the first transistor are electrically connected described the first sweep trace, and a described data line of electric connection in the leakage of described the first transistor or the source electrode;

One transistor seconds, the grid of described transistor seconds are electrically connected described the second sweep trace, and in the leakage of described transistor seconds or the source electrode one is in order to receive a reference signal;

One first electric capacity, the first end of described the first electric capacity are electrically connected the leakage of described the first transistor or in the source electrode another, and the second end of described the first electric capacity is electrically connected the leakage of described transistor seconds or in the source electrode another;

One the 3rd transistor, the described the 3rd transistorized grid is electrically connected the leakage of described the first transistor or in the source electrode another, one in the described the 3rd transistorized leakage or the source electrode is electrically connected to one first voltage, and in the described the 3rd transistorized leakage or the source electrode another is electrically connected the leakage of described transistor seconds or in the source electrode another;

One second electric capacity, the first end of described the second electric capacity are electrically connected in the described the 3rd transistorized leakage or the source electrode, and the second end of described the second electric capacity is electrically connected in the described the 3rd transistorized leakage or the source electrode another; And

One luminescence component, the first end of described luminescence component are electrically connected another in the described the 3rd transistorized leakage or the source electrode, and the second end of described luminescence component is electrically connected to a second voltage.

7. display as claimed in claim 6 is characterized in that, described display also comprises:

One data driven unit is electrically connected described data line, in order to described data-signal to be provided.

8. display as claimed in claim 6 is characterized in that, described display also comprises:

One first scanning driving device is electrically connected described the first sweep trace, in order to described the first sweep signal to be provided; And

One second scanning driving device is electrically connected described the second sweep trace, in order to described the second sweep signal to be provided.

9. display as claimed in claim 6 is characterized in that, described display also comprises:

The one scan drive unit is electrically connected described the first sweep trace and described the second sweep trace, in order to described the first sweep signal and described the second sweep signal to be provided.

10. the driving method of the image element circuit of an Organic Light Emitting Diode is characterized in that, is suitable for driving image element circuit as claimed in claim 1, and described driving method comprises:

During one during the picture reset, the voltage quasi position of another in reset the described the 3rd transistorized grid and leakage or the source electrode;

Between the storage life during the described picture, record the described the 3rd transistorized threshold voltage;

During writing during described picture provides described data-signal to the described the 3rd transistorized grid; And

Between the light emission period during the described picture, cause described luminescence component only to react on described data-signal and luminous.

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