CN203311818U - Light emitting diode pixel unit circuit and display panel - Google Patents

Abstract

The utility model discloses an active matrix organic light-emitting diode AMOLED pixel unit circuit and a display panel, which are used to realize threshold voltage compensation. The AMOLED pixel unit circuit includes a light-emitting module; a driving module for driving the light-emitting module; a light-emitting control module for controlling the light-emitting module to emit light; a threshold compensation module for performing threshold voltage compensation on the driving module; A data voltage write module for data voltage and an initialization module for initializing the threshold compensation module.

Description

Light emitting diode pixel unit circuit and display panel

Technical Field

The utility model relates to a show technical field, concretely relates to emitting diode pixel unit circuit and display panel.

Background

In the field of display technology, Active Matrix Organic Light Emitting Diode (AMOLED) display devices are receiving attention due to their advantages of being ultra-thin, good in shock resistance, large in viewing angle, short in response time, good in low temperature, high in light emitting efficiency, capable of being manufactured into flexible displays, and the like. Fig. 1(a) shows a basic pixel circuit structure of an Active Matrix Organic Light Emitting Diode (AMOLED) driven by a Thin Film Transistor (TFT) in the prior art, and fig. 1(b) shows a basic pixel circuit structure of an AMOLED driven by a P-type TFT in the prior art. VDATA in fig. 1(a) and 1(b) is a data level signal, VSCAN is a scan signal, VDD is a high voltage level signal, VSS is a low voltage level signal, T1 and T2 are thin film transistors, C1 is a capacitor, D1 is a Light Emitting Diode, and the circuits in fig. 1(a) and 1(b) are applicable to all types of transistors, including depletion TFTs, but the pixel circuit does not have a threshold voltage compensation function, and cannot solve the problem of threshold voltage uniformity due to process uniformity and the problem of Organic Light Emitting Diode (OLED) driving Light emission uniformity.

The oxide TFT is a development direction of a large-sized AMOLED, and most of device characteristics of the oxide TFT have a depletion mode characteristic, that is, an N-type threshold voltage is negative. FIG. 2 shows the prior art I of an N-type depletion TFT_ds-V_gsCharacteristic curve of which I_dsIs the current between the drain and source of the TFT, V_gsIs the voltage between the gate and source of the TFT. It can be seen from fig. 2 that the greatest characteristic of the N-type depletion TFT is that the threshold voltage is less than 0.

FIG. 3(a) shows a conventional AMOLED pixel driving circuit with threshold voltage compensation function in the prior art, wherein the gate of the driving TFT T1 is G, the source is s, the drain is D, C is a storage capacitor, D1 is a light emitting diode, VINI is an initial level signal, VDD is a high voltage level signal, VSS is a low voltage level signal, DATA is a DATA level signal, G is a high voltage level signal, and VSS is a low voltage level signal_nGate control signals, G, of the thin film transistors T2 and T4, respectively_n-1In the voltage programming stage, as shown in FIG. 3(b), the connection between T1 and the high voltage level signal VDD and the low voltage level signal VSS is first cut off, and one end of the storage capacitor connected to the gate g of T1 is charged to the initial level voltage V, which is the gate control signal of TFT T5, EM is the gate control signal of TFT T3 and T6, respectively_INIThe end of the storage capacitor connected to the source s of T1 is charged to the data level voltage V_DATAThen, the gate g and the drain d of the driving thin film transistor T1 are connected (i.e. the transistor T4 in fig. 3(a) is turned on) to form a diode connection for discharging, i.e. the voltage across the storage capacitor is set to be V_INI-V_DATADischarging to driving thin film transistor T1 sub-threshold conducting state V_TH. Wherein, V_THRepresenting the threshold voltage of T1. When the driving TFT is of a general enhancement type, the threshold voltage is positive, as shown in FIG. 4(a), and the voltage across the storage capacitor can be normally discharged to V_THAnd threshold voltage compensation is realized. However, when the driving tft has depletion-type characteristics, the threshold voltage is negative, and as shown in fig. 4(b), when the voltage across the storage capacitor is discharged through the diode-connected driving tft, the source-drain voltage of the driving tft becomes zero and turns off, and the voltage across the storage capacitor is still not discharged to reach the subthreshold conduction state, that is, the voltage across the storage capacitor is 0, not V_TH（V_TH<0) Therefore, the pixel driving threshold voltage compensation fails, where V in FIG. 4(a) and FIG. 4(b)_dsRepresenting the voltage between the drain and source of the TFT.

In summary, if the depletion TFT adopts the conventional AMOLED pixel driving circuit design of the N-type TFT, when the diode connection mode is adopted to compensate the threshold voltage, since the threshold voltage is a negative value, the source-drain voltage is zero and is cut off in advance before the TFT enters the subthreshold saturation cut-off, so that the threshold voltage compensation function is lost.

SUMMERY OF THE UTILITY MODEL

An embodiment of the utility model provides an active matrix organic light emitting diode AMOLED pixel unit circuit to and display panel for realize threshold voltage compensation function.

The embodiment of the utility model provides an active matrix organic light emitting diode AMOLED pixel unit circuit, including light emitting module, drive module, light emitting control module, threshold value compensation module, data voltage write in module and initialization module; wherein,

the driving module is used for driving the light emitting module;

the light emitting control module is used for gating the light emitting module to enable the light emitting module to emit light;

the threshold compensation module is used for performing threshold voltage compensation on the driving module;

the data voltage writing module is used for inputting data voltage to the driving module;

and the initialization module is used for initializing the threshold compensation module.

An embodiment of the utility model provides a display panel, include AMOLED pixel unit circuit.

To sum up, in the embodiment of the present invention, an active matrix organic light emitting diode AMOLED pixel unit circuit and a display panel are provided, the AMOLED pixel unit circuit includes a light emitting module; a driving module for driving the light emitting module; a light emitting control module for controlling the light emitting module to emit light; the threshold compensation module is used for compensating the threshold voltage of the driving module; the data voltage writing module is used for inputting data voltage to the driving module, and the initialization module is used for initializing the threshold compensation module.

Drawings

Fig. 1(a) and 1(b) are schematic diagrams of a basic pixel circuit structure of an AMOLED in the prior art;

FIG. 2 is a graph of current-voltage characteristics of a depletion-mode TFT in the prior art;

fig. 3(a) and 3(b) are schematic diagrams of a common AMOLED pixel driving circuit with threshold voltage compensation function in the prior art;

FIG. 4(a) is a schematic diagram of a prior art circuit enhancement type TFT threshold voltage compensation; FIG. 4(b) is a schematic diagram of the threshold voltage compensation failure of a depletion mode TFT of a prior art circuit;

fig. 5 is a schematic circuit diagram of a depletion TFT threshold voltage compensated AMOLED pixel unit according to an embodiment of the present invention;

fig. 6 is a timing diagram of control signals of a depletion TFT threshold voltage compensated AMOLED pixel cell circuit according to an embodiment of the present invention;

fig. 7(a), fig. 7(b), and fig. 7(c) are schematic diagrams illustrating the operation principle of the depletion type TFT threshold voltage compensated AMOLED pixel unit circuit according to an embodiment of the present invention;

fig. 8 is a schematic diagram of a depletion TFT threshold voltage compensation implementation provided by an embodiment of the present invention;

fig. 9 is a schematic diagram of a depletion TFT threshold voltage compensated AMOLED pixel cell circuit according to another embodiment of the present invention.

Detailed Description

An embodiment of the utility model provides an active matrix organic light emitting diode AMOLED pixel unit circuit to and display panel for realize threshold voltage compensation function.

The following provides a detailed description of the technical solution provided by the embodiments of the present invention.

The first embodiment is as follows:

referring to fig. 5, an embodiment of the present invention provides an active matrix organic light emitting diode AMOLED pixel unit circuit, including: a light emitting module 50, a driving module 51, a light emitting control module 52, a threshold compensation module 53, a data voltage writing module 54, and an initialization module 55; wherein,

a driving module 51 for driving the light emitting module 50;

a light emission control module 52 for controlling whether the light emitting module 50 emits light;

a threshold compensation module 53, configured to perform threshold voltage compensation on the driving module 51;

a data voltage writing module 54 for inputting a data voltage to the driving module 51;

an initialization module 55 for initializing the threshold compensation module 53.

Preferably, the driving module 51 includes a first transistor T1, a gate of which is connected to the first node N1 of the circuit, and two poles of which are respectively connected to the second node N2 of the circuit and a high voltage level signal line (corresponding to the high voltage level signal VDD); the first node N1 is a common connection point of the driving module 51, the light emission control module 52 and the data voltage writing module 54, and the second node N2 is a common connection point of the driving module 51, the light emission control module 52, the threshold compensation module 53 and the initialization module 55.

Preferably, the light emission control module 52 includes a second transistor T2 and a sixth transistor T6, wherein a gate of the second transistor T2 is connected to a second control signal line (corresponding to the second control signal S2 of the AMOLED pixel unit circuit), and the other two electrodes are respectively connected to the first node N1 and the third node N3; a gate of the sixth transistor T6 is connected to a second control signal line (corresponding to the second control signal S2 of the AMOLED pixel unit circuit), and the other two electrodes are connected to the second node N2 and the light emitting module 50, respectively; the third node N3 is a common connection point of the initialization module 55, the lighting control module 52 and the threshold compensation module 53.

Preferably, the light emitting module 50 includes a light emitting diode D1, an anode of which is connected to the light emitting control module 52, and a cathode of which is connected to a low voltage level signal line (corresponding to the low voltage level signal VSS).

Preferably, the light emitting diode D1 is an organic light emitting diode.

Preferably, the threshold compensation module 53 includes a storage capacitor C1, one end of which is connected to the second node N2, and the other end of which is connected to the third node N3.

Preferably, the data voltage writing module 54 includes a third transistor T3, wherein a gate of the third transistor T3 is connected to a first control signal line (corresponding to the first control signal S1 of the AMOLED pixel unit circuit), and two other poles are respectively connected to the first node N1 and a data signal line (corresponding to the data level signal VDATA);

preferably, the initialization module 55 includes a fourth transistor T4 and a fifth transistor T5, wherein a gate of the fourth transistor T4 is connected to the first control signal line (corresponding to the first control signal S1 of the AMOLED pixel unit circuit), and the other two poles are respectively connected to the high voltage level signal line (corresponding to the high voltage level signal VDD) and the third node N3; the gate of the fifth transistor T5 is connected to a third control signal line (corresponding to the third control signal S3) and the other two electrodes are connected to the second node N2 and the data signal line (corresponding to the data level signal VDATA).

Preferably, the transistors T1, T2, T3, T4, T5 and T6 are all N-type thin film transistors.

The operation principle of the AMOLED pixel unit circuit according to the first embodiment of the present invention is described below with reference to fig. 6, fig. 7(a), fig. 7(b), and fig. 7 (c).

Fig. 6 is a timing diagram of control signals of an AMOLED pixel unit circuit according to an embodiment of the present invention, where S1 and S2 are control signals with opposite polarities, and S3 is an initialization control signal. The AMOLED pixel unit circuit comprises three stages: an initialization phase a, a data writing and threshold value compensation phase b and an OLED light emitting display phase c.

An initialization stage a: as shown in FIGS. 6 and 7(a), the first control signal S1 and the third control signal, i.e., the initialization control signal S3 is high, the second control signal S2 is low, and DATA is the DATA level signal VDATA, which is called the gray scale voltage V_DATA（V_SS<V_DATA<V_DD) In which V is_SSIs the voltage of a low voltage level signal VSS, V_DDAt the voltage of the high voltage level signal VDD, the transistors T3, T4, and T5 are turned on, and the transistors T2 and T6 are turned off. The gate of the transistor T1 is charged to V_DATAThe storage capacitor C1 is charged to V by connecting the source terminal of the transistor T1_DATAAnd the other end is charged to V_DDThen the voltage across the storage capacitor C1 is V_DD-V_DATA。

Data write and threshold compensation phase b: as shown in fig. 6 and 7(b), S1 is high, S2 and S3 are low, the transistors T3 and T4 are turned on, and the transistors T2, T5 and T6 are turned off. The gate of the transistor T1 is held at V_DATADue to V_TH<0, the voltage across the storage capacitor C1 is still charged through the transistor T1 until T1 is turned off by subthreshold saturation, i.e. the source level of T1 is V_DATA-V_THWherein V is_THRepresenting the threshold voltage of T1. While the other end of the storage capacitor C1 remains at V_DDThen the voltage across the storage capacitor C1 is V_DD-（V_DATA-V_TH）=V_DD-V_DATA+V_TH。

And (c) OLED light-emitting display stage: as shown in FIG. 6 and FIG. 7(c), S2 is high, S1 and S3 are low, transistors T3, T4 and T5 are turned off, transistors T2 and T6 are turned on, and transistor T1 has a gate-source voltage V_DD-V_DATA+V_THTherefore, the transistor T1 has a leakage current of $I_{\mathrm{DS}}=\frac{1}{2}k\&CenterDot;{(V_{\mathrm{DD}}-V_{\mathrm{DATA}}+V_{\mathrm{TH}}+V_{\mathrm{TH}})}^2=\frac{1}{2}k\&CenterDot;{(V_{\mathrm{DD}}-V_{\text{DATA}})}^{},$ And k is a preset constant, the light emitting diode D1 emits light under the drive of the drain current of the transistor T1, and meanwhile, the drain current of the transistor T1 is irrelevant to the threshold voltage, so that the compensation of the threshold voltage of the transistor T1 is realized.

Since the above T1 leakage current is independent of the threshold voltage, it can be seen that the depletion TFT provided by the embodiments of the present invention can implement threshold voltage compensation, as shown in fig. 8, V in fig. 8_dsRepresenting the voltage between the drain and source of the TFT.

Example two:

referring to fig. 9, another embodiment of the present invention provides an active matrix organic light emitting diode AMOLED pixel unit circuit, including: a light emitting module 80, a driving module 81, a light emitting control module 82, a threshold compensation module 83, a data voltage writing module 84, and an initialization module 85; wherein,

a driving module 81 for driving the light emitting module 80;

a light emission control module 82 for controlling whether the light emitting module 80 emits light;

a threshold compensation module 83, configured to perform threshold voltage compensation on the driving module 81;

a data voltage writing module 84 for inputting a data voltage to the driving module 81;

an initialization module 85 for initializing the threshold compensation module 83.

Preferably, the driving module 81 includes a first transistor T1, a gate of which is connected to the first node N1 of the circuit, and two poles of which are respectively connected to the second node N2 of the circuit and a high voltage level signal line (corresponding to a high voltage level signal VDD); the first node N1 is a common connection point of the driving module 81, the light emission control module 82 and the data voltage writing module 84, and the second node N2 is a common connection point of the driving module 81, the light emission control module 82, the threshold compensation module 83 and the data initialization module 85.

Preferably, the light emission control module 82 includes a second transistor T2 and a sixth transistor T6, wherein a gate of the second transistor T2 is connected to a second control signal line (corresponding to the second control signal S2 of the AMOLED pixel unit circuit), and the other two electrodes are respectively connected to the first node N1 and the third node N3; a gate of the sixth transistor T6 is connected to a second control signal line (corresponding to the second control signal S2 of the AMOLED pixel unit circuit), and the other two electrodes are connected to the second node N2 and the light emitting module 80, respectively; the third node N3 is a common connection point of the initialization module 55, the lighting control module 82 and the threshold compensation module 83.

Preferably, the light emitting module 80 includes a light emitting diode D1, one end of which is connected to the light emitting control module 82, and the other end of which is connected to a low voltage level signal line (corresponding to the low voltage level signal VSS).

Preferably, the threshold compensation module 83 includes a storage capacitor C1, one end of which is connected to the second node N2, and the other end of which is connected to the third node N3.

Preferably, the data voltage writing module 84 includes a third transistor T3, wherein a gate of the third transistor T3 is connected to a first control signal line (corresponding to the first control signal S1 of the AMOLED pixel unit circuit), and two other poles are respectively connected to the first node N1 and a data signal line (corresponding to the data level signal VDATA);

preferably, the initialization module 85 includes a fourth transistor T4 and a fifth transistor T5, wherein a gate of the fourth transistor T4 is connected to the first control signal line (corresponding to the first control signal S1 of the AMOLED pixel unit circuit), and the other two poles are respectively connected to the high voltage level signal line (corresponding to the high voltage level signal VDD) and the third node N3; the gate of the fifth transistor T5 is connected to a third control signal line (corresponding to the third control signal S3) and the other two poles are connected to the second node N2 and the low voltage level signal line (corresponding to the low voltage level signal VSS), respectively.

Preferably, the anode of the light emitting diode D1 is connected to the sixth transistor T6, and the cathode is connected to a low voltage level signal line (corresponding to the low voltage level signal VSS).

Preferably, the transistors T1, T2, T3, T4, T5 and T6 are all N-type thin film transistors.

The embodiment of the utility model provides a second the theory of operation of the circuit that provides with the utility model provides a first the theory of operation of the circuit that provides is the same, and the difference only lies in when initializing to charge the one end that connects electric capacity C1 transistor T1 source electrode to different voltages, so the unnecessary repeated description here.

The embodiment of the utility model provides a display panel is still provided, include AMOLED pixel unit circuit.

To sum up, in the embodiment of the present invention, an active matrix organic light emitting diode AMOLED pixel unit circuit and a display panel are provided, the AMOLED pixel unit circuit includes a light emitting module; a driving module for driving the light emitting module; a light emitting control module for controlling the light emitting module to emit light; the threshold compensation module is used for compensating the threshold voltage of the driving module; the charging module is used for charging the threshold compensation module, and the data voltage writing module is used for inputting data voltage to the driving module.

Although the above embodiments have been described with reference to organic light emitting diodes as an example, it will be understood by those skilled in the art that the pixel circuits described above can be applied to driving other light emitting diodes (e.g., inorganic light emitting diodes), and are not limited to organic light emitting diodes.

It will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims and their equivalents, the present invention is also intended to include such modifications and variations.

Claims (11)

1. An active matrix light emitting diode pixel cell circuit, comprising: the device comprises a light emitting module, a driving module, a light emitting control module, a threshold compensation module, a data voltage writing module and an initialization module; wherein,

the driving module is used for driving the light emitting module;

the light emitting control module is used for gating the light emitting module to enable the light emitting module to emit light;

the threshold compensation module is used for performing threshold voltage compensation on the driving module;

the data voltage writing module is used for inputting data voltage to the driving module;

and the initialization module is used for initializing the threshold compensation module.

2. The circuit of claim 1, wherein the driving module comprises a first transistor having a gate connected to a first node of the circuit and two other poles connected to a second node of the circuit and a high voltage level signal line, respectively; the first node is a common connection point of the driving module, the light-emitting control module and the data voltage writing module, and the second node is a common connection point of the driving module, the light-emitting control module, the threshold compensation module and the initialization module.

3. The circuit according to claim 2, wherein the light emission control module comprises a second transistor and a sixth transistor, wherein a gate of the second transistor is connected to the second control signal line, and the other two electrodes are connected to the first node and the third node, respectively; the grid electrode of the sixth transistor is connected with the second control signal line, and the other two electrodes are respectively connected with the second node and the light-emitting module; the third node is a common connection point of the initialization module, the light emitting control module and the threshold compensation module.

4. The circuit of claim 3, wherein the light emitting module comprises a light emitting diode having an anode connected to the light emitting control module and a cathode connected to a low voltage level signal line.

5. The circuit of claim 4, wherein the light emitting diode is an organic light emitting diode.

6. The circuit of claim 2, wherein the threshold compensation module comprises a storage capacitor having one end connected to the second node and another end connected to the third node.

7. The circuit according to claim 2, wherein the data voltage writing module comprises a third transistor, wherein a gate of the third transistor is connected to the first control signal line, and the other two electrodes are respectively connected to the first node and the data signal line.

8. The circuit of claim 2, wherein the initialization module comprises a fourth transistor and a fifth transistor, a gate of the fourth transistor is connected to the first control signal line, and the other two electrodes are respectively connected to the high voltage level signal line and the third node; a gate of the fifth transistor is connected to a third control signal line, and the other two electrodes are connected to the second node and the data signal line, respectively.

9. The circuit of claim 2, wherein the initialization module comprises a fourth transistor and a fifth transistor, a gate of the fourth transistor is connected to the first control signal line, and the other two electrodes are respectively connected to the high voltage level signal line and the third node; and the grid electrode of the fifth transistor is connected with a third control signal line, and the other two poles of the fifth transistor are respectively connected with the second node and the low-voltage level signal line.

10. The circuit according to any of claims 2-9, wherein the transistors are all N-type thin film transistors, TFTs.

11. A display panel comprising an active matrix light emitting diode pixel cell circuit as claimed in any one of claims 1 to 10.

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