KR102618603B1 - Organic Light Emitting Display Device - Google Patents

Abstract

The display device according to this embodiment includes an organic light emitting diode that has an anode, a cathode, an internal resistance, and a parasitic capacitor and emits light; a mux circuit having an input terminal connected to the anode of the organic light emitting diode; An amplifier having an inverting terminal, a non-inverting terminal, and an output terminal; a feedback capacitor having a first electrode connected to the inverting terminal of the amplifier and a second electrode connected to the output terminal of the amplifier; a reset switch connected between the inverting terminal and the output terminal of the amplifier; a first output of the mux circuit selectively connected to the output terminal of the amplifier; a second output of the mux circuit selectively connected to the first electrode of the feedback capacitor; a third output of the mux circuit selectively connected to the inverting terminal of the amplifier; and a sensing resistor connected in series between the third output of the mux circuit and the inverting terminal of the amplifier.

Description

Organic Light Emitting Display Device

The present invention relates to an organic light emitting display device, and more particularly to an organic light emitting display device capable of sensing the driving characteristics of an organic light emitting diode.

The active matrix type organic light emitting display device includes an organic light emitting diode (hereinafter referred to as “OLED”) that emits light on its own, and has the advantages of fast response speed, high luminous efficiency, brightness, and viewing angle.

An organic light emitting display device arranges pixels, each including OLED, in a matrix form and adjusts the luminance of the pixels according to the gradation of image data. Each pixel includes a driving TFT (Thin Film Transistor) that controls the driving current flowing through the OLED according to the voltage applied between its gate electrode and its source electrode (hereinafter referred to as gate-source voltage), and the driving current The brightness of the image is controlled by the proportional amount of light emitted by the OLED.

OLED's characteristic values (i.e. operating point voltage) may vary due to process variations. In addition, OLED has deterioration characteristics in which the operating point voltage shifts and luminous efficiency decreases as the emission time elapses. Depending on the process or degradation characteristics, the OLED operating point voltage may vary for each pixel. If OLED driving characteristics are different between pixels, image sticking may occur due to luminance deviation.

In order to compensate for the deterioration in image quality due to luminance deviation, a compensation technology is known that senses OLED driving characteristics and modulates digital image data based on this sensed value. Conventional compensation technology determines the change in the operating point of the OLED based only on the amount of charge accumulated in the parasitic capacitor of the OLED when the driving current flows through the OLED.

However, the change in charge of OLED does not depend only on the change in parasitic capacitance of OLED. The amount of charge in an OLED depends on the electron mobility of the driving TFT (Thin Film Transistor) that generates the driving current, the source electrode voltage of the driving TFT, the charge and discharge characteristics of the storage capacitor connected to the gate electrode and source electrode of the driving TFT, and the pixel circuit configuration. It may change further depending on the situation. Since the amount of charge of OLED changes due to various factors, it is difficult for conventional compensation technology to accurately sense OLED driving characteristics due to unstable sensing values.

Therefore, the present invention provides an organic light emitting display device that can accurately sense the driving characteristics of OLED.

A display device according to an embodiment of the present invention includes an organic light emitting diode that has an anode, a cathode, an internal resistance, and a parasitic capacitor and emits light; a mux circuit having an input terminal connected to the anode of the organic light emitting diode; An amplifier having an inverting terminal, a non-inverting terminal, and an output terminal; a feedback capacitor having a first electrode connected to the inverting terminal of the amplifier and a second electrode connected to the output terminal of the amplifier; a reset switch connected between the inverting terminal and the output terminal of the amplifier; a first output of the mux circuit selectively connected to the output terminal of the amplifier; a second output of the mux circuit selectively connected to the first electrode of the feedback capacitor; a third output of the mux circuit selectively connected to the inverting terminal of the amplifier; and a sensing resistor connected in series between the third output of the mux circuit and the inverting terminal of the amplifier.

The present invention generates a first sensing output voltage and a second sensing output voltage by sensing the amount of charge stored in the parasitic capacitor of the OLED twice using a first current path without a sensing resistor and a second current path with a sensing resistance. The present invention derives the driving characteristic value of the OLED for each pixel by dividing the second sensing result data corresponding to the second sensing output voltage by the first sensing result data corresponding to the first sensing output voltage.

Through this, the present invention can greatly improve the accuracy of sensing by excluding the influence of other circuit elements when sensing the driving characteristics of OLED. Furthermore, the present invention can prevent over-compensation/under-compensation in advance and greatly increase compensation performance by improving the accuracy of sensing.

Figure 1 is a block diagram showing an organic light emitting display device according to an embodiment of the present invention.
Figure 2 is a diagram showing an example of connection between a sensing line and a unit pixel.
Figure 3 is a diagram showing an example of the configuration of a pixel array and a data driver IC.
Figure 4 is a diagram showing an example of the configuration of one pixel and a sensing unit according to the present invention.
Figure 5 is a diagram showing a first current path for sensing the amount of charge accumulated in the parasitic capacitor of the OLED.
Figure 6 is a diagram showing a second current path for sensing the amount of charge accumulated in the parasitic capacitor of the OLED.
Figure 7 is a diagram showing a pixel sensing method of an organic light emitting display device according to an embodiment of the present invention.
Figure 8 is a driving waveform diagram of pixels and sensing units corresponding to S1 to S8 in Figure 7.
FIG. 9A is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in periods ① and ⑤ of FIG. 8.
FIG. 9B is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in periods ② and ⑥ of FIG. 8.
FIG. 9C is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in periods ③ and ⑦ of FIG. 8.
FIG. 9d is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in period ④ of FIG. 8.
Figure 9e is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in period ⑧ of Figure 8.

The advantages and features of the present specification and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present specification is not limited to the embodiments disclosed below and will be implemented in various different forms, but the present embodiments only serve to ensure that the disclosure of the present specification is complete, and that common knowledge in the technical field to which this specification pertains is provided. It is provided to fully inform those who have the scope of the invention, and this specification is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present specification are illustrative, and the present specification is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. When 'includes', 'has', 'consists of', etc. mentioned in the specification are used, other parts may be added unless '~ only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise.

When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship between two parts is described as 'on top', 'on top', 'at the bottom', 'next to ~', 'right next to' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used.

First, second, etc. may be used to describe various components, but these components are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may be the second component within the technical idea of the present specification.

In this specification, the pixel circuit formed on the substrate of the display panel may be implemented as a TFT with an n-type MOSFET (Metal Oxide Semiconductor Field Effect Transistor) structure or a TFT with a p-type MOSFET structure. TFT is a three-electrode device including a gate, source, and drain. The source is an electrode that supplies carriers to the transistor. Within the TFT, carriers begin to flow from the source. The drain is the electrode through which carriers go out of the TFT. That is, the flow of carriers in the MOSFET flows from the source to the drain. In the case of n-type TFT (NMOS), because the carriers are electrons, the source voltage has a lower voltage than the drain voltage to allow electrons to flow from the source to the drain. Since electrons flow from the source to the drain in an n-type TFT, the direction of current flows from the drain to the source. On the other hand, in the case of p-type TFT (PMOS), since the carrier is a hole, the source voltage is higher than the drain voltage so that holes can flow from the source to the drain. In a p-type TFT, current flows from the source to the drain because holes flow from the source to the drain. It should be noted that the source and drain of the MOSFET are not fixed. For example, the source and drain of a MOSFET can change depending on the applied voltage.

Meanwhile, in this specification, the semiconductor layer of the TFT may be implemented as at least one of an oxide device, an amorphous silicon device, and a polysilicon device.

Hereinafter, embodiments of the present specification will be described in detail with reference to the attached drawings. In the following description, if it is determined that a detailed description of a known function or configuration related to the present specification may unnecessarily obscure the gist of the present specification, the detailed description will be omitted.

Figure 1 is a block diagram showing an organic light emitting display device according to an embodiment of the present invention. Figure 2 is a diagram showing an example of connection between a sensing line and a unit pixel. And, FIG. 3 is a diagram showing a configuration of a data driver connected to the pixel array of FIG. 2.

Referring to FIGS. 1 to 3 , an organic light emitting display device according to an embodiment of the present invention includes a display panel 10, a timing controller 11, a pixel sensing device, and a memory 16. The pixel sensing device of the present invention includes a sensing unit (SU) and a compensation unit (20). The pixel sensing device of the present invention may further include a panel driver consisting of a data driver 12 and a gate driver 13.

In the display panel 10, a plurality of data lines 14A and sensing lines 14B and a plurality of gate lines 15 intersect, and pixels P are arranged in a matrix form in each intersection area. .

Two or more pixels P connected to different data lines 14A may share the same sensing line 14B and the same gate line 15. For example, as shown in FIG. 2, the R pixel for red display, W pixel for white display, G pixel for green display, and B pixel for blue display that are horizontally adjacent to each other and connected to the same gate line 15 perform one sensing function. It can be commonly connected to line 14B. This sensing line sharing structure in which one sensing line 14B is assigned to each multiple pixel column makes it easy to secure the aperture ratio of the display panel. Under the sensing line structure, one sensing line 14B may be arranged for each of the plurality of data lines 14A. In the drawing, the sensing line 14B is shown parallel to the data line 14A, but may also be arranged to intersect the data line 14A.

The R pixel, W pixel, G pixel, and B pixel may constitute one unit pixel as shown in FIG. 2. However, the unit pixel may be composed of R pixel, G pixel, and B pixel.

Each pixel (P) receives a high-potential pixel voltage (EVDD) and a low-potential pixel voltage (EVSS) from the power generator. The pixel P of the present invention may have a structure suitable for sensing a deviation in the driving characteristics of a light emitting device due to a process deviation. Additionally, the pixel P of the present invention may have a structure suitable for sensing deviations in driving characteristics of a light emitting device depending on environmental conditions such as driving time and/or panel temperature. The configuration of the pixel (P) circuit can be modified in various ways. For example, the pixel P may include a plurality of switch elements and at least one storage capacitor in addition to a light emitting element and a driving element.

The timing controller 11 can implement sensing driving and display driving according to a set control sequence. Here, the sensing drive is a drive to sense the driving characteristics (operating point voltage) of the light emitting device and update the compensation value accordingly, and the display drive writes the corrected image data (CDATA) reflecting the compensation value to the display panel 10. This is the drive that reproduces the image. Under the control of the timing controller 11, sensing driving may be performed in a booting period before display driving begins or in a power-off period after display driving ends. The booting period refers to the period from when the system power is applied until the screen turns on. The power-off period refers to the period from when the screen turns off until the system is powered off.

Meanwhile, the sensing drive may be performed in a state where only the screen of the display device is turned off while the system power is being applied, for example, in standby mode, sleep mode, or low power mode. The timing controller 11 can detect standby mode, sleep mode, low power mode, etc. according to a predetermined detection process and control various operations for sensing driving.

The timing controller 11 operates a data driver ( A data timing control signal (DDC) for controlling the operation timing of 12) and a gate timing control signal (GDC) for controlling the operation timing of the gate driver 13 can be generated. The timing controller 11 may generate different timing control signals (DDC, GDC) for display driving and timing control signals (DDC, GDC) for sensing driving.

The gate timing control signal (GDC) includes a gate start pulse, a gate shift clock, etc. The gate start pulse is applied to the gate stage that produces the first output and controls that gate stage. The gate shift clock is a clock signal commonly input to the gate stages and is a clock signal for shifting the gate start pulse.

The data timing control signal (DDC) includes a source start pulse, a source sampling clock, and a source output enable signal. The source start pulse controls the data sampling start timing of the data driver 12. The source sampling clock is a clock signal that controls the sampling timing of data based on the rising or falling edge. The source output enable signal controls the output timing of the data driver 12.

The timing controller 11 may have a built-in compensation unit 20.

The compensation unit 20 receives sensing result data (SDATA) representing the driving characteristics of the light-emitting device during sensing operation from the sensing unit SU twice for each pixel. The compensation unit 20 derives the driving characteristic value of the light emitting device for each pixel based on the first sensing result data and the second sensing result data. The first sensing result data may correspond to the first sensing output voltage (see Vsen1 in FIG. 8), and the second sensing result data may correspond to the second sensing output voltage (see Vsen2 in FIG. 8). In one embodiment, the compensator 20 may derive the driving characteristic value of the light emitting device based on the ratio between the first sensing result data and the second sensing result data. For example, the compensator 20 may divide the second sensing result data by the first sensing result data to derive the driving characteristic value of the light emitting device for each pixel. By dividing the two sensing result data in this way, the driving characteristic value of the light emitting device can be determined regardless of the amount of charge accumulated in the parasitic capacitor of the light emitting device. That is, since the driving characteristic value of the light-emitting device is determined by the internal resistance value of the light-emitting device/(value of sensing resistance + internal resistance value of the light-emitting device), the accuracy of sensing can be dramatically improved. Deriving the driving characteristic values of the light emitting device will be described in detail in the following examples.

The compensation unit 20 calculates a compensation value that can compensate for the luminance deviation due to the process deviation or deterioration (i.e., shift in operating point voltage) of the light emitting device based on the derived driving characteristic value of the light emitting device, and The compensation value is stored in memory 16. The compensation value stored in the memory 16 may be updated each time the sensing operation is repeated. The compensation unit 20 corrects the data (DATA) of the input image based on the compensation value read from the memory 16 when driving the display, and supplies the corrected image data (CDATA) to the data driver 12 to emit light. The luminance deviation due to differences in device characteristics can be easily compensated.

The data driver 12 includes at least one data driver integrated circuit (IC) (SDIC). This data driver IC (SDIC) has a built-in digital-to-analog converter (hereinafter referred to as DAC) connected to each data line (14A).

The DAC converts the corrected image data (CDATA) into a display data voltage according to the data timing control signal (DDC) applied from the timing controller 11 when the display is driven and supplies it to the data lines 14A. Meanwhile, the DAC of the data driver IC (SDIC) can generate a data voltage for sensing according to the data timing control signal (DDC) applied from the timing controller 11 during sensing operation and supply it to the data lines 14A.

The data voltage for sensing is a first sensing data voltage (hereinafter referred to as on-driving data voltage) capable of turning on and driving the driving element, and a second sensing data voltage (hereinafter referred to as off-driving) capable of turning off the driving element. (referred to as data voltage). The data voltage for on driving is the voltage applied to the gate electrode of the driving element during sensing operation to turn on the driving element (i.e., the voltage that conducts the driving current), and the data voltage for off driving is the voltage applied to the gate electrode of the driving element during sensing driving. It is a voltage applied to turn off the driving element (i.e., a voltage that blocks the driving current). The data voltage for on-driving can be set to a different size for each R (red), G (green), B (blue), and W (white) pixel, taking into account the different driving characteristics of the driving element/light-emitting element for each color. there is.

The on-driving data voltage is applied to the sensing pixel that is the object of sensing within 1 unit pixel, and the off-driving data voltage is applied to non-sensing pixels that share the sensing line 14B with the sensing pixel within 1 unit pixel. approved. For example, in Figure 2, when the R pixel is sensed and the W, G, and B pixels are not sensed, the on-driving data voltage is applied to the driving element of the R pixel, and the off-driving data voltage is applied to the W and G pixels. ,B can be applied to each driving element of the pixels.

Meanwhile, not only the on-driving data voltage but also the off-driving data voltage is applied to the sensing pixel. The on-driving data voltage may be supplied during the period of programming the driving current in the sensing pixel, and the off-driving data voltage may be applied to the sensing pixel at other times.

Multiple sensing units (SU) may be mounted on the data driver IC (SDIC).

Each sensing unit (SU) is connected to the sensing line (14B) and can be selectively connected to an analog-to-digital converter (hereinafter, ADC) through one of the sampling switches (SS1 and SS2). Each sensing unit (SU) may be implemented as a current integrator. Since each sensing unit (SU) is implemented as a current sensing type, it is suitable for low current sensing and high-speed sensing. In other words, configuring each sensing unit (SU) as a current sensing type is advantageous in reducing sensing time and increasing sensing sensitivity.

The sensing unit SU further includes a mux circuit switching between the sensing line 14B and the current integrator. Here, the mux circuit may include a demultiplexer as well as a multiplexer. Depending on various circuit designs, the mux circuit may perform the functions of multiple inputs and single outputs, or may perform the functions of single inputs and multiple outputs, or may perform the functions of multiple inputs and multiple outputs. The mux circuit forms two current paths to sense the amount of charge accumulated in the parasitic capacitor. The mux circuit forms a first current path for first sensing the amount of charge accumulated in the parasitic capacitor of the light emitting device and a second current path for secondly sensing the amount of charge. The sensing unit (SU) senses the driving characteristics of the light emitting device for each pixel twice through a first current pass and a second current pass. This is to increase the accuracy of sensing by allowing the driving characteristic value of the light emitting device to be determined regardless of the amount of charge accumulated in the parasitic capacitor of the light emitting device. This will be described in detail with reference to FIGS. 4 to 9E.

The ADC can convert the sensing output voltage output twice for each pixel from the sensing unit (SU) into sensing result data (SDATA) and output it to the compensation unit 20.

The gate driver 13 may generate a gate signal for sensing based on the gate control signal (GDC) during sensing operation and then sequentially supply the gate signal to the gate lines 15. The sensing gate signal is a sensing scan signal that is synchronized with the sensing data voltage. The display lines (L1 to Ln) are sequentially sensed and driven by the sensing gate signal and the sensing data voltage. Here, each display line (L1 to Ln) is not a physical signal line, but rather a collection of R, W, G, and B pixels arranged next to each other along the horizontal direction.

When driving the display, the gate driver 13 may generate a gate signal for the display based on the gate control signal (GDC) and then sequentially supply the gate signal to the gate lines 15. The display gate signal is a display scan signal that is synchronized with the display data voltage. The display lines (L1 to Ln) are sequentially driven by the display gate signal and the display data voltage.

In the present invention, the sensing driving sequence for detecting the driving characteristics of the light emitting device can be independently performed for each R, W, G, and B pixel. For example, the sensing driving sequence of the present invention senses R pixels in a line sequential manner targeting all display lines of the display panel 10, then W pixels in a line sequential manner, and then G pixels in a line sequential manner. After sensing, B pixels can be sensed in a line sequential manner. However, the sensing order according to color can be set differently.

Figure 4 is a diagram showing an example of the configuration of a pixel (P) and a sensing unit (SU) according to the present invention. Figure 5 is a diagram showing a first current path for sensing the amount of charge accumulated in the parasitic capacitor of the OLED. And, Figure 6 is a diagram showing a second current path for sensing the amount of charge accumulated in the parasitic capacitor of the OLED.

Referring to FIG. 4, each pixel (P) may be provided with an OLED, a driving TFT (Thin Film Transistor) (DT), a storage capacitor (Cst), a first switch TFT (ST1), and a second switch TFT (ST2). You can. The TFTs constituting the pixel P may be implemented as a p type, an n type, or a hybrid type combining the p type and the n type. Additionally, the semiconductor layer of the TFTs constituting the pixel P may include amorphous silicon, polysilicon, or oxide.

OLED is a light-emitting device that emits light depending on the driving current. The OLED includes an anode electrode connected to the second node (N2), a cathode electrode connected to an input terminal of a low-potential pixel voltage (EVSS), and an organic compound layer located between the anode electrode and the cathode electrode. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer. EIL). When a driving voltage is applied to the anode and cathode electrodes, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) are moved to the emitting layer (EML) to form excitons, and as a result, the emitting layer (EML) Visible light is generated.

The driving TFT (DT) is a driving element that generates a driving current corresponding to the gate-source voltage (that is, the voltage difference between the gate voltage and the source voltage). The driving TFT (DT) includes a gate electrode connected to the first node (N1), a drain electrode connected to the input terminal of the high potential pixel voltage (EVDD), and a source electrode connected to the second node (N2). The driving TFT (DT) generates a large driving current as the voltage between the gate and source increases, and conversely, it generates a small driving current as the voltage between the gate and source becomes small.

The storage capacitor Cst is connected between the first node N1 and the second node N2 to maintain the gate-source voltage of the driving TFT DT. The first switch TFT (ST1) applies the sensing data voltage (Vdata-SEN) charged in the data line (14A) to the first node (N1) in response to the sensing gate signal (SCAN). The data voltage for sensing (Vdata-SEN) includes the data voltage for on-driving and the data voltage for off-driving. The first switch TFT (ST1) has a gate electrode connected to the gate line 15, a drain electrode connected to the data line 14A, and a source electrode connected to the first node N1. The second switch TFT (ST2) turns on/off the current flow between the second node (N2) and the sensing line (14B) in response to the sensing gate signal (SCAN). The second switch TFT (ST2) includes a gate electrode connected to the gate line 15, a drain electrode connected to the sensing line 14B, and a source electrode connected to the second node N2.

In each pixel (P), the capacity of the parasitic capacitor (Coled) of the OLED may vary depending on the process deviation or deterioration deviation of the OLED. For example, as OLED deterioration increases, the capacity of the OLED's parasitic capacitor (Coled) may decrease. By sensing the capacity of the OLED's parasitic capacitor (Coled), the threshold voltage of the OLED can be indirectly determined. The method of sensing the capacity of the OLED's parasitic capacitor (Coled) is to sense the amount of charge accumulated in the OLED's parasitic capacitor (Coled) in response to the driving current. However, as mentioned above, since the OLED charge amount is influenced not only by the OLED but also by other circuit elements, the OLED driving characteristics cannot be determined as a result of sensing the OLED charge amount once. The present invention increases the accuracy of sensing by sensing the OLED charge amount for each pixel twice through two different current passes, so that the driving characteristic value of the light emitting device is determined regardless of the OLED charge amount.

For this purpose, the sensing unit (SU) includes a current integrator (CI) and a mux circuit (MUX).

The current integrator (CI) has a first input terminal (-) connected to the sensing resistor (Rsen), a second input terminal (+) to which the amplifier reference voltage (Vpre) is applied, and a sensing output voltage (Vsen) loaded. It is provided with an amplifier (AMP) having an output terminal. Additionally, the current integrator CI includes a feedback capacitor Cfb whose one electrode is connected to the first input terminal (-) of the amplifier AMP and the other electrode is connected to the output terminal of the amplifier AMP. Additionally, the current integrator (CI) includes a reset switch (Tss) connected between the first input terminal (-) and the output terminal of the amplifier (AMP).

The mux circuit (MUX) selectively connects the mux input terminal (Ti) to the mux output terminals T1, T2, and T3. The mux input terminal Ti is connected to the sensing line 14B, and the mux output terminal T1 is connected to the output terminal of the amplifier (AMP). The mux output terminal T2 is directly connected to the first input terminal (-) of the amplifier (AMP) and one electrode of the feedback capacitor (Cfb), and the mux output terminal T3 is connected to the first input terminal (-) of the amplifier (AMP) through the sensing resistor (Rsen). It is connected to the input terminal (-) and one electrode of the feedback capacitor (Cfb).

The mux circuit (MUX) forms a first current path for first sensing the amount of charge accumulated in the parasitic capacitor (Coled) of the OLED as much as Q1, and a second current path for secondly sensing the amount of charge as much as Q2. .

As shown in Figure 5, when forming a first current path for sensing the charge amount Q1, the mux input terminal (Ti) and the mux output terminal T2 are connected to each other. Since the first current pass does not include a sensing resistance (Rsen), due to the current characteristic of flowing toward the side with a smaller resistance, all of the charge Q1 accumulated in the parasitic capacitor (Coled) of the OLED is transferred to the feedback capacitor (CI) of the current integrator (CI). Cfb) accumulates. The current integrator (CI) outputs the accumulation result of the charge amount Q1, that is, the first sensing output voltage (Vsen1).

As shown in Figure 6, when forming a second current path for sensing the charge amount Q2, the mux input terminal (Ti) and the mux output terminal T3 are connected to each other. Since the second current path includes a sensing resistor (Rsen), current distribution occurs between the OLED internal resistance (Roled) and the sensing resistor (Rsen) connected in parallel. Due to this current distribution, the charge amount Q2 corresponding to a portion of the charge amount Q1 accumulated in the parasitic capacitor (Coled) of the OLED is accumulated in the feedback capacitor (Cfb) of the current integrator (CI). The current integrator (CI) outputs the accumulation result of the charge amount Q2, that is, the second sensing output voltage (Vsen2).

Meanwhile, during the first initialization and OLED charging before the first current path is formed, and during the second initialization and OLED charging before the second current path is formed, the mux input terminal (Ti) and the mux output terminal T1 are connected to each other. do. The first initialization operation and the second initialization operation refer to initializing the source electrode node (second node) of the sensing line 14B and the driving TFT (DT) to the amplifier reference voltage (Vpre) prior to charging the OLED. OLED charging refers to accumulating charge in the OLED's parasitic capacitor (Coled) in response to the driving current input from the driving TFT (DT). The driving TFT (DT) generates a driving current in response to the on driving data voltage among the sensing data voltages (Vdata-SEN).

The sensing unit (SU) of the present invention is a sample and hold unit that sequentially samples and holds the first sensing output voltage (Vsen1) and the second sensing output voltage (Vsen2) output from the current integrator (CI) and then outputs them to the ADC. (SH) may be further included. The sample and hold unit (SH) is a sampling switch (SAM) and a holding switch (HOLD) connected in series between the current integrator (CI) and the ADC, and between the node between both switches (SAM and HOLD) and the base voltage source (GND). It has a sampling capacitor (Cs) connected to.

Figure 7 is a diagram showing a pixel sensing method of an organic light emitting display device according to an embodiment of the present invention. Figure 8 is a driving waveform diagram of pixels and sensing units corresponding to S1 to S8 in Figure 7. FIG. 9A is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in periods ① and ⑤ of FIG. 8. FIG. 9B is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in periods ② and ⑥ of FIG. 8. FIG. 9C is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in periods ③ and ⑦ of FIG. 8. FIG. 9d is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in period ④ of FIG. 8. And, Figure 9e is an equivalent circuit diagram showing the operation of the pixel and the sensing unit in period ⑧ of Figure 8.

Referring to FIGS. 7, 8, and 9A, in the first initialization period (①), the first and second switch TFTs (ST1, ST2) of the pixel (P) are connected to the on-level sensing gate signal (SCAN). In response, it is turned on, the mux input terminal (Ti) and the mux output terminal T1 are connected in the mux circuit (MUX), and the reset switch (Tss) in the current integrator (CI) is turned on. In the first initialization period (①), the output terminal of the amplifier (AMP), the sensing line (14B), and the second node (N2) of the pixel (P) are initialized to the amplifier reference voltage (Vpre) (S1). Then, the first node N1 of the pixel P is charged with the off-driving data voltage Voff and the driving TFT DT is turned off. In the first initialization period (①), the voltage of the OLED anode electrode (Vanode) and the sensing output voltage (Vsen) become the amplifier reference voltage (Vpre).

Referring to FIGS. 7, 8, and 9B, in the first Vgs programming period (②), the first and second switch TFTs (ST1, ST2) and the reset switch (Tss) of the pixel (P) are turned on. and the connection between the mux input terminal (Ti) and the mux output terminal T1 in the mux circuit (MUX) is maintained. At this time, the sensing data voltage (Vdata-SEN) is charged to the first node (N1) as the on-driving data voltage (Von), and the voltage (VN2) of the second node (N2) is the amplifier reference voltage (Vpre). maintain In the first Vgs programming period (②), the gate-source voltage (Von-Vpre) that can turn on the driving TFT (DT) is set (S2). In the first Vgs programming period (②), the voltage of the OLED anode electrode (Vanode) and the sensing output voltage (Vsen) maintain the amplifier reference voltage (Vpre).

Referring to FIGS. 7, 8, and 9C, in the first OLED charging period (③), the first and second switch TFTs (ST1, ST2) of the pixel (P) are turned off, and in the mux circuit (MUX) The connection between the mux input terminal (Ti) and the mux output terminal T1 is maintained. At this time, the voltage difference between the gate and source of the driving TFT (DT) is maintained by the storage capacitor (Cst) of the pixel (P). In the first OLED charging period (③), the driving TFT (DT) is turned on to generate driving current (Ids). The parasitic capacitor (Coled) of the OLED accumulates the driving current (Ids) input from the driving TFT (DT) (S3). The amount of charge (Qsen) accumulated in the parasitic capacitor (Coled) of the OLED is proportional to the capacity of the parasitic capacitor (Coled). In the first OLED charging period (③), the voltage of the OLED anode electrode (Vanode) is boosted to the operating point voltage of the OLED, and the OLED emits light. At this time, the sensing output voltage (Vsen) maintains the amplifier reference voltage (Vpre). Meanwhile, when the voltage (VN2) of the second node (N2), which is the voltage (Vanode) of the OLED anode electrode, is boosted in the first OLED charging period (③), the first node (Vanode) is boosted by the coupling effect of the storage capacitor (Cst). The voltage (VN1) of N2) is also boosted. Accordingly, the voltage difference between the gate and source of the driving TFT (DT) in step S3 remains the same as that in step S2.

Referring to FIGS. 7, 8, and 9D, in the Q1 sensing period (④), the first and second switch TFTs (ST1, ST2) of the pixel (P) are turned on and the reset switch (Tss) is turned off. , the mux input terminal (Ti) of the mux circuit (MUX) and the mux output terminal T2 are connected to form a first current path. At this time, the sensing data voltage (Vdata-SEN) is applied to the first node (N1) as the off-driving data voltage (Voff) to turn off the driving TFT (DT). Therefore, in the Q1 sensing period (④), the charge amount (Qsen) accumulated in the parasitic capacitor (Coled) of the OLED moves to the feedback capacitor (Cfb) of the current integrator (CI) along the first current path (i.e., Q1 sensing path). It is saved. At this time, since there is no sensing resistance (Rsen) on the first current path, no current distribution operation occurs. In other words, the amount of charge (Qsen) accumulated in the parasitic capacitor (Coled) of the OLED is not moved to the low-potential pixel voltage (EVSS) terminal through the OLED internal resistance (Roled), and Q1, which corresponds to all of the amount of charge (Qsen), is used as a current integrator. It is stored in the feedback capacitor (Cfb) of (CI). In the Q1 sensing period (④), the sensing output voltage (Vsen) gradually decreases from the amplifier reference voltage (Vpre) to the first sensing output voltage (Vsen1) corresponding to Q1 (S4). The first sensing output voltage (Vsen1) becomes Qsen/Cout. Here, Cout is the capacity of the feedback capacitor (Cfb). The first sensing output voltage (Vsen1) is converted into first sensing result data by the ADC through the sample and hold unit and then output to the compensation unit 20. Meanwhile, in the Q1 sensing period (④), the voltage (Vanode) of the OLED anode electrode is lowered by Q1 from the operating point voltage of the OLED.

Referring to FIGS. 7, 8, and 9A, the operation of the second initialization period (⑤) is substantially the same as the operation of the first initialization period (①). In the second initialization period (⑤), the output terminal of the amplifier (AMP), the sensing line (14B), and the second node (N2) of the pixel (P) are initialized again to the amplifier reference voltage (Vpre) (S5).

Referring to FIGS. 7, 8, and 9B, the operation of the second Vgs programming period (⑥) is substantially the same as the operation of the first Vgs programming period (②). In the second Vgs programming period (⑥), the gate-source voltage (Von-Vpre) that can turn on the driving TFT (DT) is set (S6).

Referring to FIGS. 7, 8, and 9C, the operation of the second OLED charging period (⑦) is substantially the same as the operation of the first OLED charging period (③). In the second OLED charging period (⑦), the parasitic capacitor (Coled) of the OLED accumulates the driving current (Ids) input from the driving TFT (DT) (S7).

Referring to FIGS. 7, 8, and 9E, in the Q2 sensing period (⑧), the first and second switch TFTs (ST1, ST2) of the pixel (P) are turned on and the reset switch (Tss) is turned off. , the mux input terminal (Ti) of the mux circuit (MUX) and the mux output terminal T3 are connected to form a second current path. At this time, the sensing data voltage (Vdata-SEN) is applied to the first node (N1) as the off-driving data voltage (Voff) to turn off the driving TFT (DT). In the Q2 sensing period (⑧), the charge (Qsen) accumulated in the parasitic capacitor (Coled) of the OLED moves to the feedback capacitor (Cfb) of the current integrator (CI) along the second current path (i.e., Q2 sensing path) and is stored. do. At this time, a current distribution operation occurs because there is a sensing resistance (Rsen) on the first current path. In other words, a portion of the charge (Qsen) accumulated in the parasitic capacitor (Coled) of the OLED is moved to the low-potential pixel voltage (EVSS) terminal through the OLED internal resistance (Roled), and Q2, which corresponds to a portion of the charge amount (Qsen), is used as a current. It is stored in the feedback capacitor (Cfb) of the integrator (CI). In the Q2 sensing period (⑧), the sensing output voltage (Vsen) gradually decreases from the amplifier reference voltage (Vpre) to the second sensing output voltage (Vsen2) corresponding to Q2 (S8). The second sensing output voltage (Vsen2) becomes Qsen*Roled/[(Rsen+Roled)*Cout]. Here, Cout is the capacity of the feedback capacitor (Cfb). The second sensing output voltage (Vsen2) is converted into second sensing result data by the ADC through the sample and hold unit and then output to the compensation unit 20. Meanwhile, in the Q2 sensing period (⑧), the voltage (Vanode) of the OLED anode electrode is lowered by Q2 from the operating point voltage of the OLED.

Referring to FIG. 7, the compensator 20 divides the second sensing result data corresponding to the second sensing output voltage (Vsen2) into the first sensing result data corresponding to the first sensing output voltage (Vsen1) to drive the OLED. Derive characteristic values. The driving characteristic value of OLED is determined as “Roled/(Rsen+Roled)”. Unlike "Qsen," "Roled/(Rsen+Roled)" is not affected by other circuit elements, greatly improving sensing accuracy.

As described above, the present invention uses a first current pass without a sensing resistor and a second current pass with a sensing resistor to sense the amount of charge stored in the parasitic capacitor of the OLED twice to produce a first sensing output voltage and a second sensing output. generates voltage. The present invention derives the driving characteristic value of the OLED for each pixel by dividing the second sensing result data corresponding to the second sensing output voltage by the first sensing result data corresponding to the first sensing output voltage.

Through this, the present invention can greatly improve the accuracy of sensing by excluding the influence of other circuit elements when sensing the driving characteristics of OLED. Furthermore, the present invention can prevent over-compensation/under-compensation in advance and greatly increase compensation performance by improving the accuracy of sensing.

Through the above-described content, those skilled in the art will be able to see that various changes and modifications can be made without departing from the technical idea of the present invention. Therefore, the technical scope of the present invention should not be limited to what is described in the detailed description of the specification, but should be defined by the scope of the patent claims.

10: display panel 11: timing controller
12: data driver 13: gate driver
14A: data line 14B: sensing line
15: gate line 20: compensation unit
SU: Sensing unit 30: Power generation unit

Claims (20)

An organic light-emitting diode that has an anode, a cathode, an internal resistance, and a parasitic capacitor and emits light;
a mux circuit having an input terminal connected to the anode of the organic light emitting diode;
An amplifier having an inverting terminal, a non-inverting terminal, and an output terminal;
a feedback capacitor having a first electrode connected to the inverting terminal of the amplifier and a second electrode connected to the output terminal of the amplifier;
a reset switch connected between the inverting terminal and the output terminal of the amplifier;
a first output of the mux circuit selectively connected to the output terminal of the amplifier;
a second output of the mux circuit selectively connected to the first electrode of the feedback capacitor;
a third output of the mux circuit selectively connected to the inverting terminal of the amplifier; and
A display device having a sensing resistor connected in series between the third output of the mux circuit and the inverting terminal of the amplifier. According to claim 1,
A display device in which the driving characteristics of the organic light emitting diode are determined according to the ratio of the internal resistance and the sensing resistance. According to claim 2,
A display device in which the driving characteristic value of the organic light emitting diode is determined by dividing the internal resistance by the sum of the internal resistance and the sensing resistance. According to claim 1,
A display device in which the feedback capacitor and the amplifier operate as a current integrator. According to claim 1,
The non-inverting terminal of the amplifier is a display device connected to a reference voltage source. According to claim 1,
a first switching transistor having a first gate electrode, a first source electrode, and a first drain electrode;
a second switching transistor having a second gate electrode, a second source electrode, and a second drain electrode;
a gate line connected to the first gate electrode of the first switching transistor and connected to the second gate electrode of the second switching transistor;
a data line connected to the first drain electrode of the first switching transistor;
a sensing line connected to the second drain electrode of the second switching transistor and connected to the input terminal of the mux circuit;
A gate electrode is connected to the first source electrode of the first switching transistor, a drain electrode is connected to a high potential driving voltage source, and the source electrode is connected to the anode of the organic light emitting diode and the second source electrode of the second switching transistor. A driving transistor connected to; and
A display device further comprising a storage capacitor connected between the first source electrode of the first switching transistor and the second source electrode of the second switching transistor. According to claim 6,
The gate line supplies scan signals to the first and second switching transistors,
The data line supplies a data voltage to the driving transistor,
The sensing line is connected to any one of the first output, the second output, and the third output of the mux circuit. According to claim 7,
Further comprising a data driving circuit,
The data driving circuit is,
Supplying a reference voltage from the amplifier to the anode of the organic light-emitting diode through the sensing line during a first period for initializing the organic light-emitting diode,
In order to turn on the driving transistor during the second period, an on-driving data voltage is supplied to the driving transistor through the data line, and a driving signal is supplied to the organic light-emitting diode through the driving transistor,
Charging the parasitic capacitor of the organic light emitting diode during a third period,
During the fourth period, a first sensing path is formed connecting the parasitic capacitor of the organic light-emitting diode, the sensing line, and the feedback capacitor, and after charging the feedback capacitor with the parasitic capacitor of the organic light-emitting diode, the feedback capacitor A display device that senses the stored first charge amount. According to claim 8,
The anode of the organic light emitting diode maintains the reference voltage during the first and second periods. According to clause 9,
The data driving circuit is,
To supply a reference voltage from the amplifier to the anode of the organic light-emitting diode through the sensing line during the first period,
Turn on the reset switch connected to the amplifier to discharge the feedback capacitor,
Supplying the reference voltage to the output terminal of the amplifier,
A display device connecting the sensing line and the output terminal of the amplifier through the mux circuit. According to clause 9,
The driving signal includes a driving current flowing into the organic light emitting diode. According to clause 9,
The data driving circuit is,
To charge the parasitic capacitor of the organic light emitting diode during the third period,
Turning off the first switching transistor by applying a gate signal to the first switching transistor connected to the driving transistor,
Turning off the second switching transistor by applying the gate signal to the second switching transistor connected to the anode of the organic light-emitting diode,
A display device that supplies the driving signal to the parasitic capacitor to accumulate charge in the parasitic capacitor. According to claim 12,
The data driving circuit is,
To form the first sensing path connecting the parasitic capacitor of the organic light emitting diode, the sensing line, and the feedback capacitor during the fourth period,
Connecting the sensing line to the input terminal of the mux circuit,
Connecting the second output of the mux circuit to the feedback capacitor,
Applying the gate signal to the second switching transistor to turn on the second switching transistor,
A display device that turns off the driving transistor by applying an off-driving data voltage to the driving transistor. According to claim 8,
A display device in which the internal resistance of the organic light emitting diode is not included in the first sensing path. According to claim 8,
The data driving circuit is,
Supplying the reference voltage of the amplifier to the anode of the organic light-emitting diode through the sensing line during a fifth period for initializing the organic light-emitting diode,
Supplying the driving signal to the organic light-emitting diode through the driving transistor connected to the anode of the organic light-emitting diode during a sixth period,
Charging the parasitic capacitor of the organic light emitting diode during a seventh period,
During the eighth period, a second sensing path is formed connecting the internal resistance of the organic light-emitting diode, the parasitic capacitor, the sensing line, the sensing resistance of the amplifier, and the feedback capacitor, and the parasitic capacitor of the organic light-emitting diode is formed. A display device that senses the second amount of charge stored in the feedback capacitor after charging the feedback capacitor. According to claim 15,
The data driving circuit is,
To form the second sensing path connecting the internal resistance of the organic light emitting diode, the parasitic capacitor, the sensing line, the sensing resistance of the amplifier, and the feedback capacitor during the eighth period,
Connect the sensing line to the input terminal of the mux circuit,
Connecting the third output of the mux circuit to the sensing resistor of the amplifier,
Applying a gate signal to the second switching transistor to turn on the second switching transistor,
A display device that turns off the driving transistor by applying an off-driving data voltage to the driving transistor. According to claim 16,
Further comprising a compensation circuit connected to the data driving circuit,
The compensation circuit is,
Determining a first value based on the first charge amount along the first sensing path,
Determining a second value based on the second amount of charge according to the second sensing path,
A display device that calculates a driving characteristic value of the organic light emitting diode based on the ratio of the first value and the second value. According to claim 1,
Further comprising a sample and hold circuit,
The sample and hold circuit is,
a sampling switch connected to the output terminal of the amplifier;
a holding switch connected to the sampling switch; and
A display device including a sampling capacitor connected between the sampling switch and the holding switch. According to claim 18,
An analog-to-digital converter connected to the output terminal of the sample and hold circuit; and
Further comprising a compensation circuit connected to the analog-to-digital converter,
A display device wherein the compensation circuit determines a driving characteristic value of the organic light emitting diode based on a value obtained by dividing the internal resistance by a sum of the internal resistance and the sensing resistance. According to claim 19,
The display device wherein the compensation circuit determines a data voltage for compensating for luminance deviation based on the determined driving characteristic value of the organic light emitting diode.