TW201344658A - Light-emitting component driving circuit and related pixel circuit - Google Patents

Abstract

A pixel circuit relating to an organic light emitting diode (OLED) is provided by the invention, and if the circuit configuration (5T1C) thereof collocates with suitable operation waveforms, the current flowing through an OLED in the OLED pixel circuit may not be changed with the variation of the conducting voltage (Voled_th) of the OLED in a long time stress, and may not be varied with the threshold voltage (Vth) shift of a TFT used for driving the OLED. Accordingly, not only the brightness decay of the OLED in a long time stress can be mitigated or compensated, but also the brightness uniformity of the applied OLED display can be substantially improved.

Description

Light-emitting element driving circuit and related pixel circuit

The present invention relates to a flat display technology, and more particularly to a drive circuit for a light-emitting element having a self-luminous property (for example, an organic light-emitting diode) and related pixel circuits.

Due to the rapid advancement of the multimedia society, the technology of semiconductor components and display devices has also made great progress. In terms of the display, the Active Matrix Organic Light Emitting Diode (AMOLED) display has no viewing angle limitation, low manufacturing cost, high response speed (about 100 times or more of liquid crystal), power saving, and self-contained Light-emitting, DC drive for portable machines, large operating temperature range, light weight, and miniaturization and thinning of hardware devices to meet the characteristics of multimedia era displays. Therefore, the active matrix organic light-emitting diode display has great potential for development, and is expected to be the next generation of novel flat-panel display, thereby replacing the liquid crystal display (LCD).

At present, active matrix organic light-emitting diode display panels are mainly produced in two ways, one is fabricated by low-temperature polysilicon (LTPS) thin film transistor (TFT) process technology, and the other is using amorphous germanium (a- Si) is fabricated by thin film transistor (TFT) process technology. Among them, the thin film transistor manufacturing technology of low temperature polysilicon requires a relatively large number of mask processes, resulting in an increase in cost. Therefore, the current low-temperature polysilicon thin film transistor process technology is mainly applied to small and medium-sized panels, and the amorphous germanium thin film transistor technology is mainly applied to large-sized panels.

In general, an active matrix organic light-emitting diode display panel produced by a thin film transistor process technology using a low-temperature polycrystalline germanium may have a P-type or an N-type in a pixel circuit. Whether the P-type or N-type thin film transistor is selected to realize the organic light-emitting diode pixel circuit, the current flowing through the organic light-emitting diode not only undergoes long-term stress with the on-voltage (Voled_th) of the organic light-emitting diode The change in (long time stress) changes, and it also varies with the threshold voltage drift (Vth shift) of the thin film transistor used to drive the organic light-emitting diode. As a result, the brightness uniformity and brightness constancy of the organic light emitting diode display will be affected.

In view of the above, in order to effectively solve/improve the problems described in the prior art (ie, improve brightness uniformity and brightness constancy of an organic light emitting diode display), an exemplary embodiment of the present invention provides a light emitting element driving The circuit includes: a driving unit and a data storage unit. The driving unit is coupled between a predetermined potential and a light emitting element (for example, an organic light emitting diode, but is not limited thereto), and includes a driving transistor for controlling a light flowing through the light emitting element in an illumination stage. Drive current. The data storage unit includes a storage capacitor directly coupled to the conduction path for conducting the driving current for a data writing phase, through the storage capacitor to a data voltage, a threshold voltage associated with the driving transistor, and associated with the illuminating The on-voltage of the component is stored. During the light emitting phase, the driving unit generates the driving current flowing through the light emitting element in response to a voltage across the storage capacitor, and the driving current is not affected by the threshold voltage of the driving transistor and the turn-on voltage of the light emitting element.

In an exemplary embodiment of the present invention, the driving unit may further include: a light-emitting control transistor, wherein the gate is configured to receive a light-emitting signal, and the source is coupled, under the condition that the predetermined potential is a ground potential Connected to the ground potential, and the drain is coupled to the source of the driving transistor and the first end of the storage capacitor. In addition, the drain of the driving transistor is coupled to the cathode of the organic light emitting diode, and the anode of the organic light emitting diode is coupled to a power supply voltage.

In an exemplary embodiment of the present invention, the data storage unit may further include: a write transistor, a collection transistor, and a conversion transistor under the condition that the predetermined potential is the ground potential. The gate of the write transistor is configured to receive a scan signal, the drain of the write transistor is used to receive the data voltage, and the source of the write transistor is coupled to the second end of the storage capacitor. The gate of the collecting transistor is configured to receive the scanning signal, the source of the collecting transistor is coupled to the gate of the driving transistor, and the drain of the collecting transistor is coupled to the drain of the driving transistor and the organic light emitting diode The cathode of the body. The gate of the conversion transistor is configured to receive the illuminating signal, the source of the conversion transistor is coupled to the gate of the driving transistor and the source of the collecting transistor, and the drain of the switching transistor is coupled to the writing transistor The source and the second end of the storage capacitor.

In an exemplary embodiment of the present invention, the organic light emitting diode driving circuit sequentially enters the data writing phase and the light emitting phase under the condition that the predetermined potential is the ground potential.

In an exemplary embodiment of the present invention, the driving transistor, the light-emitting control transistor, the writing transistor, the collecting transistor, and the switching transistor are all under the condition that the predetermined potential is the ground potential. N-type transistor.

In an exemplary embodiment of the present invention, in the data writing phase, only the scan signal is enabled under the condition that the preset potential is the ground potential; and in the light emitting phase, only The illuminating signal is enabled.

In an exemplary embodiment of the present invention, the driving unit may further include: a light-emitting control transistor, wherein the gate is configured to receive a light-emitting signal, and the source is coupled, under the condition that the predetermined potential is a power supply voltage. Connected to the power supply voltage, and the drain is coupled to the source of the driving transistor and the first end of the storage capacitor. In addition, the drain of the driving transistor is coupled to the anode of the organic light emitting diode, and the cathode of the organic light emitting diode is coupled to a ground potential.

In an exemplary embodiment of the present invention, the data storage unit may further include: a write transistor, a collection transistor, and a conversion transistor under the condition that the preset potential is the power voltage. The gate of the write transistor is configured to receive a scan signal, the source of the write transistor is configured to receive the data voltage, and the drain of the write transistor is coupled to the second end of the storage capacitor. The gate of the collecting transistor is configured to receive the scanning signal, and the drain of the collecting transistor is coupled to the gate of the driving transistor, and the source of the collecting transistor is coupled to the drain of the driving transistor and the organic light emitting diode The anode of the body. The gate of the conversion transistor is configured to receive the illuminating signal, the drain of the conversion transistor is coupled to the gate of the driving transistor and the source of the collecting transistor, and the source of the converting transistor is coupled to the writing transistor The drain is connected to the second end of the storage capacitor.

In an exemplary embodiment of the present invention, under the condition that the preset potential is the power supply voltage, the storage capacitor is reset in a reset phase in response to the power supply voltage and the data voltage.

In an exemplary embodiment of the present invention, under the condition that the preset potential is the power supply voltage, the organic light emitting diode driving circuit sequentially enters the reset phase, the data writing phase, and The illuminating phase.

In an exemplary embodiment of the present invention, the driving transistor, the light-emitting control transistor, the writing transistor, the collecting transistor, and the switching transistor are all under the condition that the predetermined potential is the power voltage. P-type transistor.

In an exemplary embodiment of the present invention, the scanning signal and the illuminating signal are simultaneously enabled in the reset phase under the condition that the preset potential is the power voltage; In the writing phase, only the scanning signal is enabled; and in the illuminating phase, only the illuminating signal is enabled.

In an exemplary embodiment of the invention described above, the power supply voltage may be a fixed power supply voltage.

In another exemplary embodiment of the invention described above, the power supply voltage may be a variable supply voltage. Under this condition, the power supply voltage is only in the data writing phase (under the condition that the preset potential is the ground potential) or the reset phase (at the preset potential is the power supply) Under the condition of voltage) change from a high level voltage to a set voltage. The set voltage is lower than the high level voltage, and the set voltage may be determined according to a threshold voltage of the driving transistor and a turn-on voltage of the organic light emitting diode.

In an exemplary embodiment of the present invention, the light-emitting element driving circuit may be an organic light-emitting diode driving circuit.

Another exemplary embodiment of the present invention provides a pixel circuit having the proposed light emitting element driving circuit.

Based on the above, the present invention provides a pixel circuit associated with an organic light emitting diode, and the circuit structure (5T1C) can be combined with an appropriate operating waveform to make the current flowing through the organic light emitting diode not follow the organic The turn-on voltage (Voled_th) of the light-emitting diode changes over a long period of time, and does not vary with the threshold voltage drift (Vth shift) of the thin film transistor used to drive the organic light-emitting diode. . In this way, not only the brightness decay of the organic light-emitting diode over a long period of time can be slowed down or compensated, but also the brightness uniformity of the applied organic light-emitting diode display can be greatly improved.

It is to be understood that the foregoing general description and claims

DETAILED DESCRIPTION OF THE INVENTION Reference will now be made in detail to the exemplary embodiments embodiments In addition, wherever possible, the same reference numerals in the drawings

FIG. 1 is a schematic diagram of a pixel circuit 10 according to an exemplary embodiment of the present invention, and FIG. 2 is a circuit diagram of the pixel circuit 10 of FIG. Referring to FIG. 1 and FIG. 2 together, the pixel circuit 10 of the exemplary embodiment includes a light-emitting element (for example, an Organic Light Emitting Diode (OLED) 101, but is not limited thereto, so the pixel is The circuit 10 can be regarded as an organic light emitting diode pixel circuit and a light-emitting component driving circuit 103. The light emitting element driving circuit 103 includes a driving unit 105 and a data storage unit 107.

In the present exemplary embodiment, the driving unit 105 is coupled between a preset potential (eg, a ground potential) and the organic light emitting diode 101, and includes a driving transistor T1. The driving current I _OLED flowing through the organic light emitting diode 101 is controlled in an emission phase.

The data storage unit 107 includes a storage capacitor Cst directly coupled to the conduction path of the conduction driving current I _OLED for use in a data-writing phase and through a storage capacitor Cst to a data voltage (data V _IN , a threshold voltage (V _th (T1)) associated with the driving transistor T1, and a turn-on voltage (Voled_th) associated with the organic light-emitting diode 101 are stored.

In the present exemplary embodiment, the driving unit 105 is in the light emitting phase, and generates a driving current I _OLED flowing through the organic light emitting diode 101 in response to a voltage across the storage capacitor Cst, and the driving current I _{OLED is} not driven. The influence of the threshold voltage (V _th (T1)) of the crystal T1 and the on-voltage (Voled_th) of the organic light-emitting diode 101. In other words, the drive current I _{OLED is} independent of the turn-on voltage (Voled_th) of the organic light-emitting diode 101 and the threshold voltage (V _th (T1)) of the drive transistor T1.

In addition, the driving unit 105 further includes an emission control transistor T2. In addition, the data storage unit 107 further includes a writing transistor T3, a collection transistor T4, and a conversion. Transaction transistor T5.

In the present exemplary embodiment, the driving transistor T1, the light-emitting control transistor T2, the writing transistor T3, the collecting transistor T4, and the switching transistor T5 may all be N-type transistors, such as N-type thin film transistors ( Thin-film-transistor, TFT). Moreover, the organic light emitting diode display panel (OLED display panel) in which the (organic light emitting diode) pixel circuit 10 is applied can be fabricated by a low temperature polysilicon (LTPS) thin film transistor (TFT) process technology, but Not limited to this.

In addition, in the circuit structure of the (organic light-emitting diode) pixel circuit 10, the anode of the organic light-emitting diode 101 is coupled to the power supply voltage Vdd, and the cathode of the organic light-emitting diode 101 is connected. The drain of the driving transistor T1 is coupled. The gate of the light-emitting control transistor T2 is used to receive the emission signal Em, the source of the light-emitting control transistor T2 is coupled to the ground potential, and the drain of the light-emitting control transistor T2 is coupled to the driver. The source of the transistor T1 and the first end of the storage capacitor Cst.

The gate of the write transistor T3 is for receiving a scan signal Sn, and the gate of the write transistor T3 is for receiving the data voltage V _IN (this assumes V _IN =Vdd+Vdata-Voled_in, where Voled_in is The organic light-emitting diode 101 does not undergo an initial on-voltage of long-term stress, and the source of the write transistor T3 is coupled to the second end of the storage capacitor Cst. The gate of the collecting transistor T4 is for receiving the scanning signal Sn, the source of the collecting transistor T4 is coupled to the gate of the driving transistor T1, and the drain of the collecting transistor T4 is coupled to the drain of the driving transistor T1. The cathode of the organic light-emitting diode 101. The gate of the switching transistor T5 is configured to receive the illuminating signal Em. The source of the converting transistor T5 is coupled to the gate of the driving transistor T1 and the source of the collecting transistor T4, and the drain of the converting transistor T5 is coupled. The source of the transistor T3 is written to the second end of the storage capacitor Cst.

Furthermore, during the operation of the (organic light-emitting diode) pixel circuit 10, the light-emitting element driving circuit 103 (ie, the organic light-emitting diode driving circuit) successively enters the data writing phase and the light-emitting phase, for example, for example, P1 and P2 shown in Fig. 3. As is clear from Fig. 3, in the data writing phase P1, only the scanning signal Sn is enabled. In addition, in the illuminating phase P2, only the illuminating signal Em is enabled.

It is worthwhile to explain that, due to the driving transistor T1, the light-emitting control transistor T2, the writing transistor T3, the collecting transistor T4, and the type of the switching transistor T5 in the (organic light-emitting diode) pixel circuit 10. The states are all N-type, so it is known that the driving transistor T1, the light-emitting control transistor T2, the writing transistor T3, the collecting transistor T4, and the switching transistor T5 are high active. Thus, the previous expression for the scanning signal Sn and the illuminating signal Em means that the scanning signal Sn and the illuminating signal Em are at a high level.

First, in the data writing phase P1, since only the scanning signal Sn is enabled, as shown in FIG. 4A, the writing transistor T3 and the collecting transistor T4 are turned on-on (not turned on X). The light-emitting control transistor T2 and the switching transistor T5 are turned off-off (X). Accordingly, the driving transistor T1 will react to the conduction of the collecting transistor T4 to form a diode-connection, thereby charging the storage capacitor Cst until the voltage of the node C1 becomes Vdd-Voled_th- _Vth ( T1) so far. Further, in response to the turn-on of the write transistor T3, the voltage of the node B1 is Vdd+Vdata-Voled_in.

In the present exemplary embodiment, at the data writing phase P1, since the voltage across the organic light-emitting diode 101 is not greater than its turn-on voltage (Voled_th), and the voltage of the node B1 is greater than the voltage of the node C1, The organic light emitting diode 101 will not be illuminated (because there is no complete current loop). On the other hand, at the data writing phase P1, the voltage across the storage capacitor Cst can be expressed as:

Vdata+Voled_th-Voled_in+V _th (T1).

Moreover, it can be further simplified to Vdata + ΔVoled + V _th (T1). Among them, △Voled=Voled_th-Voled_in.

Therefore, in the data writing phase P1, the data voltage V _IN , the threshold voltage (V _th (T1)) associated with the driving transistor T1, and the organic light emitting diode 101 can be simultaneously completed through the storage capacitor Cst. The storage of the amount of cross-pressure change (ΔVoled).

Then, in the illuminating phase P2, since only the illuminating signal Em is enabled, as shown in FIG. 4B, the writing transistor T3 and the collecting transistor T4 are turned off (turned-off, X), and the illuminating The control transistor T2 and the switching transistor T5 are turned on-on. Accordingly, the driving transistor T1 will generate a driving current I _OLED that is not affected by the on-voltage (Voled_th) of the organic light-emitting diode 101 and the threshold voltage (V _th (T1)) of the driving transistor T1.

More specifically, in response to the capacitive coupling effect of the storage capacitor Cst, the gate-to-source voltage (Vgs) of the driving transistor T1 will be equal to Vdata + ΔVoled + V _th (T1). In this way, in the light-emitting phase P2, the driving current I _OLED generated by the driving transistor T1 can be expressed as Equation 1 below:

Where K is the current constant associated with the driving transistor T1.

In addition, since the gate-source voltage (Vgs) of the driving transistor T1 is known, that is, Vgs=Vdata+ΔVoled+ _Vth (T1).

Therefore, if the gate-source voltage (Vgs) of the known driving transistor T1 is brought to Equation 1 , then Equation 2 is as follows:

Equation 2 can be further simplified to Equation 3 below:

Here, it can be seen from Equation 3 that in the light-emitting phase P2, the driving current I _OLED flowing through the organic light-emitting diode 101 is not related to the threshold voltage (V _th (T1)) of the driving transistor T1. In addition, it can be seen in Equation 3 that the driving current I _OLED flowing through the organic light emitting diode 101 is additionally increased by a parameter ΔVoled, and the extra parameter ΔVoled can compensate/slow the organic light emitting The phenomenon that the polar body 101 is attenuated by the brightness caused by long-term stress. As a result, the driving current I _OLED flowing through the organic light emitting diode 101 can be prevented from changing with the change in the on-voltage (Voled_th) of the organic light-emitting diode 101 over a long period of time.

On the other hand, it is different from the operation waveform diagram of the (organic light-emitting diode) pixel circuit 10 shown in FIG. 3, and FIG. 5 is another diagram of the (organic light-emitting diode) pixel circuit 10 of FIG. Operate the waveform diagram. The operation waveform diagram of the (organic light-emitting diode) pixel circuit 10 shown in FIG. 3 is constructed such that the power supply voltage Vdd is a fixed power supply voltage, that is, the power supply voltage Vdd is continuously maintained at the high level voltage Vh.

However, the operational waveform diagram of the (organic light-emitting diode) pixel circuit 10 shown in FIG. 5 is structured such that the power supply voltage Vdd is a variable power supply voltage, and the power supply voltage Vdd is only high during the data writing phase P1. The level voltage Vh is changed to a certain set voltage Vp. The set voltage Vp is lower than the high level voltage Vh, and the set voltage Vp can be determined according to the threshold voltage (V _th (T1)) of the driving transistor T1 and the turn-on voltage (Voled_th) of the organic light emitting diode 101. In other words, the set voltage Vp may be a voltage that can just turn on the organic light-emitting diode 101 and the driving transistor T1, for example, Voled_th+V _th (T1), but is not limited thereto.

The difference between the operation waveforms of the (organic light-emitting diode) pixel circuit 10 shown in FIG. 3 and FIG. 5 is only that the power supply voltage Vdd based on FIG. 5 will be from the high level in the data writing phase P1. The voltage Vh changes to the set voltage Vp, so the voltage of the node C1 changes (decreases) to Vp-Voled_th- _Vth (T1), and the voltage of the node B1 changes (decreases) to Vp+Vdata-Voled_in. However, using the operational waveform diagram of the (organic light-emitting diode) pixel circuit 10 shown in FIG. 5, the driving current I _OLED flowing through the organic light-emitting diode 101 and the threshold voltage of the driving transistor T1 can still be made. _Th (T1)) is irrelevant, and at the same time, it can compensate/slow the phenomenon that the organic light-emitting diode 101 is attenuated by the long-term stress.

On the other hand, according to an idea similar to FIG. 2 and FIG. 3 (ie, a complementary circuit structure), FIG. 6 is a schematic diagram of a pixel circuit 60 according to another exemplary embodiment of the present invention, and FIG. 7 is illustrated as The circuit diagram of the pixel circuit 60 of FIG. Referring to FIG. 6 and FIG. 7 together, the pixel circuit 60 of the exemplary embodiment includes a light emitting element (for example, an organic light emitting diode (OLED) 601, but is not limited thereto, so the pixel circuit 60 can be regarded as organic. The light emitting diode circuit circuit) and the light emitting element drive circuit 603. The light emitting device driving circuit 603 includes a driving unit 605 and a data storage unit 607.

In the present exemplary embodiment, the driving unit 605 is coupled between a preset potential (eg, a power voltage Vdd) and the organic light emitting diode 601, and includes a driving transistor T1'. For controlling the driving current I _OLED flowing through the organic light emitting diode 601 during the light emitting phase. In addition, the data storage unit 607 includes a storage capacitor Cst directly coupled to the conduction path of the conduction driving current I _OLED for use in the data writing phase, through the storage capacitor Cst to the data voltage V _IN , associated with the driving transistor T1 ′. The threshold voltage (V _th (T1')) and the on-voltage (Voled_th) associated with the organic light-emitting diode 601 are stored.

In the present exemplary embodiment, the driving unit 605 is in the light emitting phase, and generates a driving current I _OLED flowing through the organic light emitting diode 601 in response to the voltage across the storage capacitor Cst, and the driving current I _{OLED is} not driven. The influence of the threshold voltage (V _th (T1')) of the crystal T1' and the on-voltage (Voled_th) of the organic light-emitting diode 601. In other words, the driving current I _{OLED is} independent of the turn-on voltage (Voled_th) of the organic light-emitting diode 601 and the threshold voltage (V _th (T1') of the driving transistor T1'.

In addition, the driving unit 605 further includes an emission control transistor T2'; in addition, the data storage unit 607 further includes a write transistor T3', an acquisition transistor T4', and a conversion transistor T5'. In the present exemplary embodiment, the driving transistor T1', the light-emitting control transistor T2', the writing transistor T3', the collecting transistor T4', and the switching transistor T5' may all be P-type transistors, such as P. Thin film transistor (TFT). Moreover, the organic light emitting diode display panel (OLED display panel) in which the (organic light emitting diode) pixel circuit 60 is applied can be fabricated by a low temperature polysilicon (LTPS) thin film transistor (TFT) process technology, but Not limited to this.

In addition, in the circuit structure of the (organic light-emitting diode) pixel circuit 60, the cathode of the organic light-emitting diode 601 is coupled to the ground potential, and the anode of the organic light-emitting diode 101 is coupled to the driving transistor T1'. Bungee jumping. The gate of the light-emitting control transistor T2' is configured to receive the light-emitting signal Em, the source of the light-emitting control transistor T2' is coupled to the power supply voltage Vdd, and the drain of the light-emitting control transistor T2' is coupled to the driving transistor T1' The source and the first end of the storage capacitor Cst.

The gate of the write transistor T3' is for receiving the scan signal Sn, and the source of the write transistor T3' is for receiving the data voltage V _IN (this assumes V _IN =Voled_in-Vdata, where Voled_in is the organic light-emitting diode The body 601 is not subjected to a long-term stress initial turn-on voltage, and the gate of the write transistor T3' is coupled to the second end of the storage capacitor Cst. The gate of the collecting transistor T4' is for receiving the scanning signal Sn, the drain of the collecting transistor T4' is coupled to the gate of the driving transistor T1', and the source of the collecting transistor T4' is coupled to the driving transistor T1. 'The bungee and the anode of the organic light-emitting diode 601. The gate of the conversion transistor T5' is for receiving the illuminating signal Em, and the drain of the switching transistor T5' is coupled to the gate of the driving transistor T1' and the drain of the collecting transistor T4', and the switching transistor T5' is The source is coupled to the drain of the write transistor T3' and the second end of the storage capacitor Cst.

Furthermore, during operation of the (organic light-emitting diode) pixel circuit 60, the light-emitting element driving circuit 603 (ie, the organic light-emitting diode driving circuit) successively enters a reset phase and data writing. The stages and the illuminating stages are, for example, PR, P1 and P2 as shown in FIG. As can be clearly seen from Fig. 8, in the reset phase PR, the scanning signal Sn and the illuminating signal Em are simultaneously enabled. In the data writing phase P1, only the scanning signal Sn is enabled. In addition, in the illuminating phase P2, only the illuminating signal Em is enabled.

It is worthwhile to explain that the driving transistor T1', the light-emitting control transistor T2', the writing transistor T3', the collecting transistor T4', and the conversion power in the (organic light-emitting diode) pixel circuit 60 are The pattern of the crystal T5' is all P-type, so that it is known that the driving transistor T1', the light-emitting control transistor T2', the writing transistor T3', the collecting transistor T4', and the switching transistor T5' are low. Level enable (low active). Thus, the previous expression for the scanning signal Sn and the illuminating signal Em means that the scanning signal Sn and the illuminating signal Em are at a low level.

First, in the reset phase PR, since the scanning signal Sn and the illuminating signal Em are simultaneously enabled, as shown in FIG. 9A, the illuminating control transistor T2', the writing transistor T3', the collecting transistor T4', and the conversion The transistor T5' will be turned on-on (not X). Accordingly, the storage capacitor Cst will be reset in the reset phase PR in response to the supply voltage Vdd and the data voltage V _IN . More specifically, in response to the conduction of the light-emitting control transistor T2', the voltage of the node C2 is substantially (or precharged) to the power supply voltage Vdd; in addition, it is reflected by the turn-on of the write transistor T3', the node B2 The voltage is substantially (or precharged) to V _IN (ie, Voled_in-Vdata).

Then, at the data writing phase P1, since only the scanning signal Sn is enabled, as shown in FIG. 9B, the writing transistor T3' and the collecting transistor T4' are turned on (turned-on, not hit). X), and the light-emitting control transistor T2' and the switching transistor T5' are turned off-off (X). Therefore, the driving transistor T1' is formed in response to the conduction of the collecting transistor T4' to form a diode connection, so that the storage capacitor Cst is discharged through the driving transistor T1' and the organic light emitting diode 601 until driving. The transistor T1' is turned off and the voltage of the node C2 becomes Voled_th + _Vth (T1'). Further, in response to the conduction of the write transistor T3', the voltage of the node B2 is Voled_in-Vdata.

In the present exemplary embodiment, at the data writing phase P1, the voltage across the storage capacitor Cst can be expressed as:

Voled_in-Vdata-Voled_th-V _th (T1').

Moreover, it can be further simplified to -Vdata-ΔVoled-V _th (T1'). Among them, △Voled=Voled_th-Voled_in.

Therefore, in the data writing phase P1, the data voltage V _IN , the threshold voltage (V _th (T1 ') associated with the driving transistor T1 ′, and the organic light emitting diode can be simultaneously completed through the storage capacitor Cst. Storage of the amount of change in the cross-pressure of the body 601 (ΔVoled).

Finally, in the illuminating phase P2, since only the illuminating signal Em is enabled, as shown in FIG. 9C, the writing transistor T3' and the collecting transistor T4' are turned off (turned-off, X). The light-emitting control transistor T2' and the switching transistor T5' are turned on-on. Accordingly, the driving transistor T1' will generate a driving current I _OLED that is not affected by the on-voltage (Voled_th) of the organic light-emitting diode 601 and the threshold voltage (V _th (T1') of the driving transistor T1'.

More specifically, in response to the capacitive coupling effect of the storage capacitor Cst, the gate-to-source voltage (Vgs) of the driving transistor T1' will be equal to -Vdata-ΔVoled- _Vth (T1'). In this way, in the light-emitting phase P2, the driving current I _OLED generated by the driving transistor T1 ′ can be expressed as Equation 4 below:

Where K is the current constant associated with the driving transistor T1'.

In addition, since the gate-source voltage (Vgs) of the driving transistor T1' is known, that is, Vgs=-Vdata-ΔVoled- _Vth (T1').

Therefore, if the gate-source voltage (Vgs) of the known driving transistor T1' is brought to Equation 4 , that is, Equation 5 below:

Equation 5 can be further simplified to Equation 6 below:

Here, it can be seen from Equation 6 that in the light-emitting phase P2, the driving current I _OLED flowing through the organic light-emitting diode 601 is not related to the threshold voltage (V _th (T1')) of the driving transistor T1'. In addition, it can be seen in Equation 6 that the driving current I _OLED flowing through the organic light emitting diode 601 is additionally increased by a parameter ΔVoled, and the extra parameter ΔVoled can compensate/slow the organic light emitting The phenomenon that the polar body 601 is attenuated by the long-term stress. As a result, the driving current I _OLED flowing through the organic light emitting diode 601 is not changed as the conduction voltage (Voled_th) of the organic light emitting diode 601 changes over a long period of time.

Similarly, an operation waveform diagram different from the (organic light-emitting diode) pixel circuit 60 shown in FIG. 8 is shown, and FIG. 10 is another operation of the (organic light-emitting diode) pixel circuit 60 of FIG. Waveform diagram. The operation waveform diagram of the (organic light-emitting diode) pixel circuit 60 shown in FIG. 8 is constructed such that the power supply voltage Vdd is a fixed power supply voltage, that is, the power supply voltage Vdd is continuously maintained at the high level voltage Vh.

However, the operation waveform diagram of the (organic light-emitting diode) pixel circuit 60 shown in FIG. 10 is structured such that the power supply voltage Vdd is a variable power supply voltage, and the power supply voltage Vdd is only in the reset phase PR from the high standard. The bit voltage Vh is changed to a certain set voltage Vp. In other words, except for the reset phase PR, the power supply voltage Vdd is maintained at the high level voltage Vh, that is, the power supply voltage Vdd changes from the set voltage Vp back to the high level in the data writing phase P1 after the reset phase PR. Voltage Vh. The set voltage Vp is lower than the high level voltage Vh, and the set voltage Vp may be based on the threshold voltage (V _th (T1′)) of the driving transistor T1′ and the turn-on voltage (Voled_th) of the organic light emitting diode 601. Decide. In other words, the set voltage Vp may be a voltage that is just capable of turning on the organic light-emitting diode 601 and the driving transistor T1', for example, Voled_th+ _Vth (T1'), but is not limited thereto.

The difference between the operation waveforms of the (organic light-emitting diode) pixel circuit 60 shown in FIG. 8 and FIG. 10 is only that the power supply voltage Vdd based on FIG. 10 will be from the high-level voltage in the reset phase PR. Vh changes to the set voltage Vp, so the voltage of the node C2 changes (decreases) to Vp, and the voltage of the node B2 remains Voled_in-Vdata. However, with the operation waveform diagram of the (organic light-emitting diode) pixel circuit 60 shown in FIG. 10, the driving current I _OLED flowing through the organic light-emitting diode 601 and the threshold voltage of the driving transistor T1' can still be made ( V _th (T1')) is irrelevant, and at the same time, it can compensate/slow the phenomenon that the organic light-emitting diode 601 is attenuated by the long-term stress.

It can be seen that the circuit structure of the (organic light-emitting diode) pixel circuit 10/60 disclosed in the above exemplary embodiment is 5T1C (that is, 5 thin film transistors + 1 capacitor), and if appropriate operation is performed The waveform (as shown in [Fig. 3, Fig. 5] / [Fig. 8, Fig. 10]), so that the current flowing through the organic light emitting diode 101/601 (I _OLED ) does not follow the organic light emitting diode The turn-on voltage (Voled_th) changes over a long period of time, and does not follow the threshold voltage drift (Vth shift) of the thin film transistor T1/T1' used to drive the organic light-emitting diode 101/601. It is different. In this way, not only the brightness decay of the organic light-emitting diode 101/601 over a long period of time can be slowed down or compensated, but also the brightness uniformity of the applied organic light-emitting diode display can be greatly improved ( Brightness uniformity). In addition, any organic light-emitting diode display panel and an organic light-emitting diode display thereof to which the (organic light-emitting diode) pixel circuit 10/60 of the above exemplary embodiment is applied, belong to the present invention. Want to ask for the scope of protection.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the invention, and any one of ordinary skill in the art can make some modifications and refinements without departing from the spirit and scope of the invention. The scope of the invention is defined by the scope of the appended claims. In addition, any of the objects or advantages or features of the present invention are not required to be achieved by any embodiment or application of the invention. In addition, the abstract sections and headings are only used to assist in the search of patent documents and are not intended to limit the scope of the invention.

10, 60. . . (organic light-emitting diode) pixel circuit

101, 601. . . Light-emitting element (organic light-emitting diode)

103, 603. . . Light-emitting element driving circuit

105, 605. . . Drive unit

107,607. . . Data storage unit

T1, T1’. . . Drive transistor

T2, T2’. . . Illumination control transistor

T3, T3’. . . Write transistor

T4, T4’. . . Acquisition transistor

T5, T5’. . . Conversion transistor

Cst. . . Storage capacitor

B1, C1, B2: C2. . . node

I _OLED . . . Drive current

V _IN . . . Data voltage

Vdd. . . voltage

Vh. . . High level voltage

Vp. . . Setting voltage

Sn. . . Scanning signal

Em. . . Luminous signal

P1. . . Data writing phase

P2. . . Luminous phase

PR. . . Reset phase

The following drawings are a part of the specification of the invention, and illustrate the embodiments of the invention

FIG. 1 is a schematic diagram of a pixel circuit 10 according to an exemplary embodiment of the invention.

2 is a circuit diagram of the pixel circuit 10 of FIG. 1.

FIG. 3 is a diagram showing the operation waveform of the pixel circuit 10 of FIG. 1.

4A and 4B are respectively schematic diagrams showing the operation of the pixel circuit 10 of FIG. 1.

FIG. 5 is a diagram showing another operational waveform of the pixel circuit 10 of FIG. 1.

FIG. 6 is a schematic diagram of a pixel circuit 60 according to another exemplary embodiment of the present invention.

FIG. 7 is a circuit diagram of the pixel circuit 60 of FIG. 6.

FIG. 8 is a diagram showing the operation waveform of the pixel circuit 60 of FIG.

9A-9C are schematic diagrams showing the operation of the pixel circuit 60 of FIG. 6, respectively.

FIG. 10 is a diagram showing another operational waveform of the pixel circuit 60 of FIG.

10. . . (organic light-emitting diode) pixel circuit

101. . . Light-emitting element (organic light-emitting diode)

103. . . Light-emitting element driving circuit

105. . . Drive unit

107. . . Data storage unit

T1. . . Drive transistor

T2. . . Illumination control transistor

T3. . . Write transistor

T4. . . Acquisition transistor

T5. . . Conversion transistor

Cst. . . Storage capacitor

I _OLED . . . Drive current

V _IN . . . Data voltage

Vdd. . . voltage

Sn. . . Scanning signal

Em. . . Luminous signal

Claims (17)

A driving device for driving a light-emitting device, comprising: a driving unit coupled between a predetermined potential and a light-emitting element, and comprising a driving transistor for controlling a driving current flowing through the light-emitting element in an illumination phase; And a data storage unit, including a storage capacitor directly coupled to one of the conduction paths for conducting the driving current, for performing a data writing phase, through the storage capacitor, for a data voltage, associated with the driving transistor a threshold voltage and a turn-on voltage associated with the light-emitting element are stored, wherein, in the light-emitting phase, the driving unit generates the driving current flowing through the light-emitting element in response to a voltage across the storage capacitor, and the driving current It is not affected by the threshold voltage of the driving transistor and the turn-on voltage of the light-emitting element. The light-emitting device driving circuit of claim 1, wherein the predetermined potential is a ground potential, and the light-emitting element is an organic light-emitting diode, and the driving unit further comprises: a light-emitting control transistor, The gate is configured to receive a light emitting signal, the source thereof is coupled to the ground potential, and the drain is coupled to the source of the driving transistor and the first end of the storage capacitor, wherein the driving transistor The anode is coupled to the cathode of the organic light emitting diode, and the anode of the organic light emitting diode is coupled to a power supply voltage. The light-emitting device driving circuit of claim 2, wherein the data storage unit further comprises: a write transistor, the gate is configured to receive a scan signal, and the drain is configured to receive the data voltage, and The source is coupled to the second end of the storage capacitor; a collector transistor, the gate is configured to receive the scan signal, the source is coupled to the gate of the drive transistor, and the drain is coupled to the gate Driving a drain of the transistor and a cathode of the organic light emitting diode; and a switching transistor, the gate of the transistor is configured to receive the light emitting signal, and the source thereof is coupled to the gate of the driving transistor and the collecting transistor The source is coupled to the source of the write transistor and the second end of the storage capacitor, wherein the light emitting device driving circuit is an organic light emitting diode driving circuit. The illuminating device driving circuit of claim 3, wherein the OLED driving circuit sequentially enters the data writing phase and the illuminating phase; the driving transistor, the illuminating control transistor, and the writing The transistor, the acquisition transistor, and the conversion transistor are all N-type transistors; in the data writing phase, only the scan signal is enabled; and in the illumination phase, only the illumination signal is enabled. The light-emitting element driving circuit of claim 4, wherein the power supply voltage is a fixed power supply voltage. The light-emitting element driving circuit of claim 4, wherein the power supply voltage is a variable power supply voltage. The light-emitting device driving circuit of claim 6, wherein the power supply voltage is changed from a high-level voltage to a set voltage only during the data writing phase, and the set voltage is lower than the high-level voltage; And the set voltage is determined according to the threshold voltage of the driving transistor and the ON voltage of the organic light emitting diode. The light-emitting device driving circuit of claim 1, wherein the predetermined potential is a power supply voltage, and the light-emitting element is an organic light-emitting diode, and the driving unit further comprises: a light-emitting control transistor, The gate is configured to receive a light emitting signal, the source thereof is coupled to the power supply voltage, and the drain is coupled to the source of the driving transistor and the first end of the storage capacitor, wherein the driving transistor The anode is coupled to the anode of the organic light emitting diode, and the cathode of the organic light emitting diode is coupled to a ground potential. The light-emitting device driving circuit of claim 8, wherein the data storage unit further comprises: a write transistor, wherein the gate is configured to receive a scan signal, and the source is configured to receive the data voltage; The drain is coupled to the second end of the storage capacitor; a collector transistor, the gate is configured to receive the scan signal, the drain is coupled to the gate of the drive transistor, and the source is coupled to the gate a drain of the driving transistor and an anode of the organic light emitting diode; and a switching transistor, wherein the gate is configured to receive the light emitting signal, and the drain is coupled to the gate of the driving transistor and the collecting transistor The drain electrode is coupled to the drain of the write transistor and the second end of the storage capacitor, wherein the light emitting device driving circuit is an organic light emitting diode driving circuit. The illuminating element driving circuit of claim 9, wherein the storage capacitor is reset in a reset phase in response to the power supply voltage and the data voltage. The illuminating device driving circuit of claim 10, wherein the OLED driving circuit sequentially enters the resetting phase, the data writing phase, and the illuminating phase; the driving transistor, the illuminating control The transistor, the write transistor, the acquisition transistor, and the conversion transistor are all P-type transistors; during the reset phase, the scan signal is simultaneously enabled with the illumination signal; during the data writing phase, Only the scan signal is enabled; and during the illumination phase, only the illumination signal is enabled. The light-emitting element driving circuit of claim 11, wherein the power supply voltage is a fixed power supply voltage. The light-emitting element driving circuit of claim 11, wherein the power supply voltage is a variable power supply voltage. The light-emitting element driving circuit of claim 13, wherein the power supply voltage is changed from a high-level voltage to a set voltage only during the reset phase, and the set voltage is lower than the high-level voltage; The set voltage is determined according to the threshold voltage of the driving transistor and the turn-on voltage of the organic light emitting diode. A pixel circuit includes: a light-emitting element for emitting light in response to a driving current in a light-emitting phase; a driving unit coupled between a predetermined potential and the light-emitting element, and comprising a driving transistor And the data storage unit includes a storage capacitor directly coupled to one of the conduction paths of the driving current for a data writing phase. And storing, by the storage capacitor, a data voltage, a threshold voltage associated with the driving transistor, and a turn-on voltage associated with the light emitting device, wherein the driving unit reacts with the storage capacitor during the light emitting phase The driving current flowing through the light emitting element is generated across the voltage, and the driving current is not affected by the threshold voltage of the driving transistor and the turn-on voltage of the light emitting element. The pixel circuit of claim 15, wherein: the predetermined potential is a ground potential; the light emitting element is an organic light emitting diode; the driving unit further comprises: a light emitting control transistor, the gate The pole is configured to receive a light emitting signal, the source thereof is coupled to the ground potential, and the drain is coupled to the source of the driving transistor and the first end of the storage capacitor, wherein the driving transistor has a drain The anode of the organic light emitting diode is coupled to a power supply voltage; the data storage unit further includes: a write transistor, the gate is configured to receive a scan signal The drain is configured to receive the data voltage, and the source is coupled to the second end of the storage capacitor; a collection transistor, the gate is configured to receive the scan signal, and the source is coupled to the drive transistor a gate electrode coupled to the drain of the driving transistor and a cathode of the organic light emitting diode; and a switching transistor having a gate for receiving the light emitting signal, the source of which is coupled to the gate Driving the gate of the transistor and the collecting transistor a source of the drain electrode coupled to the source of the write transistor and the second end of the storage capacitor; and the drive transistor, the light-emitting control transistor, the write transistor, the acquisition transistor And the conversion transistor is an N-type transistor. The pixel circuit of claim 15, wherein: the predetermined potential is a power supply voltage; the light emitting element is an organic light emitting diode; and the driving unit further comprises: a light emitting control transistor, the gate The pole is configured to receive a light-emitting signal, the source of which is coupled to the power supply voltage, and the drain of the driving transistor is coupled to the source of the driving transistor and the first end of the storage capacitor, wherein the driving transistor has a drain An anode of the organic light emitting diode is coupled to the cathode of the organic light emitting diode, and the cathode of the organic light emitting diode is coupled to a ground potential. The data storage unit further includes: a write transistor, the gate is configured to receive a scan signal The source is configured to receive the data voltage, and the drain is coupled to the second end of the storage capacitor; a collector transistor, the gate is configured to receive the scan signal, and the drain is coupled to the drive transistor a gate electrode coupled to the drain of the driving transistor and an anode of the organic light emitting diode; and a switching transistor, the gate of the gate is configured to receive the light emitting signal, and the drain is coupled to the gate Driving the gate of the transistor and the collecting transistor a drain, the source of which is coupled to the drain of the write transistor and the second end of the storage capacitor; and the drive transistor, the light-emitting control transistor, the write transistor, the acquisition transistor And the conversion transistor is a P-type transistor.