TWI839506B - Display driving device - Google Patents

Abstract

A display driving device includes sensing lines configured to sense pixel signals of a display panel; and a voltage limiter provided for each of the sensing lines. The voltage limiter senses a voltage variation of the sensing line, and limits a voltage level of the sensing line to a reference voltage.

Description

Display driver

Various embodiments generally relate to display devices, and more particularly, to display driver devices that sense pixel signals of display panels.

Generally, a display device includes a display panel, a display driver and a timing controller. The display driver converts digital image data into a source drive signal and provides the source drive signal to the display panel.

Depending on the degree of degradation, the display panel may have characteristics that are not uniform between pixels. To compensate for such characteristic deviations between pixels, the display driver detects pixel signals, converts the pixel signals into pixel data that are digital signals, and provides the pixel data to a timing controller.

However, in the prior art, when an overcurrent greater than a pixel current of a normal channel flows due to a defect in a pixel of a display panel, voltage variations at the input and output of the current-to-voltage converter suddenly increase, and thus data values of adjacent normal channels may be affected by parasitic capacitors between channels.

Therefore, in the related art, there is a problem that due to the influence of the defective channel on the data of the normal channel, compensation for the characteristic deviation between pixels cannot be performed normally, so good results cannot be obtained in terms of image quality.

Various embodiments relate to a display driving device that can minimize the influence of a defective pixel on sensing data of a normal channel by limiting a sudden voltage change caused by an overcurrent occurring in the defective pixel.

In one embodiment, a display driving device may include: a sensing line configured to sense a pixel signal of a display panel; and a voltage limiter provided for each of the sensing lines. The voltage limiter may sense a voltage change of the sensing line and limit the voltage level of the sensing line to a reference voltage.

According to an embodiment, the influence of a defective pixel of a display panel on sensing data of a normal channel can be minimized by limiting a sudden voltage change caused by an overcurrent occurring in the defective pixel.

In addition, according to the embodiment, since normal compensation can be expected, performance in terms of image quality can be improved.

In addition, according to the embodiment, improvement in reliability or productivity can be expected by minimizing image quality degradation caused when a small number of defective pixels occur.

The embodiment provides a display driving device that can minimize the influence of defective pixels of a display panel on sensing data of a normal channel by limiting the voltage change of the corresponding channel when an overcurrent occurs in the defective pixel.

In an embodiment, before starting the sensing operation, the reference voltage may be set to a value equal to or similar to the initial value of the sensing line.

In an embodiment, the first reference voltage and the second reference voltage may be set as a threshold voltage of the diode.

In an embodiment, the initialization period may be defined as a period for initializing the sensing line to a reference voltage before sensing a pixel signal from the display panel.

Although the embodiment shows the case where an overcurrent is sent in a defective pixel, it should be noted that the embodiment is not limited thereto. Even in the case where an overcurrent is introduced into the sensing line through the sensing pad due to electrostatic discharge, the embodiment can limit the voltage level of the sensing line to the reference voltage.

Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The terms used herein and in the claims should not be interpreted as limited to the general or dictionary meanings, and should be interpreted as the meanings and concepts corresponding to the technical aspects of the present disclosure.

The embodiments described herein and the configurations shown in the accompanying drawings are preferred embodiments of the present disclosure, but do not represent all technical features of the present disclosure. Therefore, various equivalent configurations and modifications may be made to the present disclosure when the present application is submitted.

FIG. 1 is a block diagram showing a representation of an example of a display drive device 100 according to an embodiment.

1, the display driver 100 according to the present embodiment includes a source driver (SD-IC) that provides a source drive signal to a display panel 200. For ease of explanation, FIG1 shows a portion of the inside of the source driver (SD-IC). FIG1 shows a component that senses a pixel signal from the display panel 200 for external compensation of the display panel 200.

As the display panel 200 , a liquid crystal panel, an organic light emitting diode (OLED) panel, or the like can be used.

The display panel 200 may include a pixel array in a matrix form. The pixel array may include R (red), G (green), and B (blue) pixels, or may further include W (white) pixels for improving brightness. Each pixel may include a pixel circuit that provides a current corresponding to a source drive signal provided from the display driver 100 to a light emitting element.

The pixel circuit may include a drive transistor that provides a current corresponding to a source drive signal to the light-emitting element. The characteristics of the drive transistor (such as a threshold voltage and a mobility) or the characteristics of the light-emitting element (such as a threshold voltage) may be non-uniform depending on the position of the pixel, or uneven brightness may occur due to degradation of the drive transistor and the light-emitting element over time.

To compensate for this characteristic of the pixel, the display driver 100 may sense a pixel signal representing the pixel characteristic of the display panel 200, may convert the pixel signal into pixel data as a digital signal, and may provide the pixel data to a controller (not shown). For example, the display driver 100 may be configured to sense a current or a voltage as a pixel signal. The embodiment of FIG. 1 shows a configuration in which a current is sensed as a pixel signal and then converted into a voltage.

The pixel signal can be used to calculate the characteristics of the driving transistor in the pixel circuit, such as the threshold voltage and the mobility, and the degradation characteristics of the light-emitting element, such as the threshold voltage. Since the pixel current flowing through the light-emitting element varies according to the threshold voltage and the mobility of the driving transistor and the threshold voltage of the light-emitting element, the pixel current can be used to calculate the value of the above characteristics of the pixel. In addition, the characteristic value of the pixel can be used to compensate the digital image data.

When a defect occurs in a pixel of the display panel 200 and an overcurrent I _damage flows, the sensing data of a normal channel may be affected by a parasitic capacitor C _para between the defective channel and the normal channel.

Therefore, the present disclosure discloses a display driving device 100 that can minimize the impact of a defective channel on sensing data of a normal channel by limiting a sudden voltage change caused by an overcurrent occurring in a defective pixel of a display panel.

To this end, the display driving device 100 may include a voltage limiter 10 in each sensing line SL for sensing a pixel signal of the display panel 200. Such a voltage limiter 10 may detect a voltage variation of the sensing line SL and may limit the voltage variation to a reference voltage.

The display driving device 100 may include a voltage limiter 10 and a current-to-voltage converter 20 provided for each sensing line SL, and an analog-to-digital converter 30.

As a wiring for sensing a pixel signal of the display panel 200, each sensing line SL electrically connects the sensing pad 12 and the current-voltage converter 20. The sensing pad 12 may be a read pad for reading a pixel signal from the display panel 200, and the pixel signal may be exemplified as a current _IPXL of each pixel.

The current-voltage converter 20 may convert a current _IPXL corresponding to a pixel signal transmitted through the sensing line SL into a voltage, and may provide the voltage to the analog-to-digital converter 30. For example, the current-voltage converter 20 may be configured by an integration circuit that converts a current into a voltage.

The analog-to-digital converter 30 converts the voltage corresponding to the current _IPXL of each pixel into pixel data as a digital signal and provides the pixel data to the timing controller. For example, the analog-to-digital converter 30 may include a sampling circuit that samples the voltage of each pixel in a predetermined sequence.

A voltage limiter 10 may be provided for each sensing line SL for sensing a pixel signal of a sensing channel CH of the display panel 200.

Such a voltage limiter 10 can sense the voltage variation of the sensing line SL and can limit the voltage variation to a reference voltage. Before starting the sensing operation, the reference voltage can be set to a value equal to or close to an initial value.

For example, in a case where an overcurrent I _damage flows through the sensing line SL due to a defect in a pixel of one of the channels CH of the display panel 200, the voltage limiter 10 can limit the voltage variation of the sensing line SL to a reference voltage, which is set to a value equal to or approximately equal to an initial value before the sensing operation starts.

FIG. 2 is a block diagram showing a representation of an example of a display driving device according to an embodiment, in which the voltage limiter 10 of FIG. 1 is configured by a diode.

2 , the voltage limiter 10 may include a first diode D1 and a second diode D2.

In the first diode D1, an anode terminal may be connected to the sensing line SL, and a cathode terminal may be connected to a reference voltage VREF.

In the second diode D2, a cathode terminal may be connected to the sensing line SL, and an anode terminal may be connected to a reference voltage VREF.

Before starting the sensing operation, the reference voltage VREF may be set to a value equal to or close to an initial value.

When the voltage variation of the sensing line SL is greater than the threshold voltage of the first diode D1 and the second diode D2, the voltage limiter 10 may limit the voltage variation of the sensing line SL to the reference voltage VREF.

The display driving device 100 including the voltage limiter 10 in this manner can limit the voltage level of the sensing line SL to the reference voltage VREF by turning on the first diode D1 and the second diode D2 when an overcurrent I _damage flows due to a defect in a pixel of the display panel 200.

Therefore, even in the case where an overcurrent flows due to a defect in a pixel, the display driving device 100 including the voltage limiter 10 can minimize the influence exerted on the data value of the adjacent normal channel.

Although these embodiments illustrate the case where an overcurrent flows through the sensing line SL due to a defect in a pixel of the display panel 200, it should be noted that these embodiments are not limited thereto.

Even when an overcurrent is introduced into the sensing line SL through the sensing pad 12 due to electrostatic discharge, the display driving device 100 according to this embodiment can limit the voltage level of the sensing line SL to the reference voltage VREF by turning on the first diode D1 and the second diode D2.

FIG. 3 is a block diagram showing a representation of an example of a display drive device 100 according to an embodiment, in which the voltage limiter 10 of FIG. 1 is configured by a comparator.

3 , the voltage limiter 10 may include a first comparator 14, a second comparator 16, and an operator. For example, the operator may include an OR element 18.

The first comparator 14 compares the voltage of the sense line SL with the first reference voltage VREFH and provides a first comparison signal to the OR element 18.

The second comparator 16 compares the voltage of the sense line SL with the second reference voltage VREFL and provides a second comparison signal to the OR element 18.

For example, the first reference voltage VREFH and the second reference voltage VREFL may be set to a threshold voltage of a diode. The first comparator 14 and the second comparator 16 may output a logic low signal by sensing that the voltage of the sense line SL has a voltage change amplitude less than the threshold voltage of the diode, and may output a logic high signal when the voltage of the sense line SL changes to be equal to or greater than the threshold voltage.

As another example, the first reference voltage VREFH and the second reference voltage VREFL may be set to a level less than a threshold voltage of a diode. The voltage limiter 10 may sense that the voltage of the sense line SL changes to be equal to or greater than the first reference voltage VREFH and the second reference voltage VREFL, where the first reference voltage VREFH and the second reference voltage VREFL are set to a level less than a threshold voltage of a diode, and may output a reset signal. In this way, in this embodiment, the voltage limiter 10 may be configured to sense a voltage change amplitude less than a threshold voltage of a diode. The OR element 18 can perform an OR logic function on the first comparison signal and the second comparison signal, and can output a reset signal SW_RST to the reset circuit 19.

The reset circuit 19 initializes the sense line SL to a reset voltage in response to the reset signal SW_RST. Before starting the sensing operation, the reset voltage may be set to a value equal to or close to the initial value. For example, the reset circuit 19 may use the circuit in the current-voltage converter 20 and the reset voltage.

When the voltage of the sense line SL reaches or exceeds the first reference voltage VREFH or the second reference voltage VREFL, the first comparator 14 and the second comparator 16 make the first comparison signal or the second comparison signal logically high.

In response to the first comparison signal or the second comparison signal, the OR element 18 makes the reset signal SW_RST logically high.

The reset circuit 19 can initialize the sensing line SL to a reset voltage in response to the reset signal SW_RST.

In this way, in the display driving device 100 including the voltage limiter 10, in the event that an overcurrent _Idamage flows due to a defect in a pixel of the display panel 200, the reset signal SW_RST can be enabled to initialize the voltage level of the sensing line SL to a value equal to or approximately the initial value before the sensing operation starts.

Meanwhile, the display driving device 100 may include an internal voltage generating circuit (not shown) that generates a first reference voltage VREFH and a second reference voltage VREFL. The internal voltage generating circuit may generate a plurality of internal voltages, and an internal voltage optimized for an operation of limiting voltage variation in the internal voltage may be selected as the first reference voltage VREFH and the second reference voltage VREFL.

For example, the internal voltage generating circuit can select voltages suitable for the characteristics of the display panel 200 as the first reference voltage and the second reference voltage among a plurality of internal voltages by using a decoder, a voltage reference, and a control signal (such as a packet). The characteristics of the display panel 200 may include a normal voltage variation range of a sensing line according to characteristics of a pixel such as a threshold voltage and a mobility.

As apparent from the above description, in the display driving device 100 according to the embodiment, the influence of the defective pixels of the display panel 200 on the sensing data of the normal channels can be minimized by limiting the sudden voltage change caused by the overcurrent occurring in the defective pixels.

Furthermore, in the display driving device 100 according to the embodiment, since normal compensation can be expected, performance in terms of image quality can be improved.

Furthermore, in the display driving device 100 according to the embodiment, improvement in reliability or productivity can be expected by minimizing image quality degradation caused when a small number of defective pixels occur.

Although various embodiments have been described above, those skilled in the art will appreciate that the embodiments described are exemplary only. Therefore, the disclosure described herein should not be limited based on the embodiments described.

10: Voltage limiter

12: Sensing pad

14: First comparator

16: Second comparator

18: OR element

19: Reset circuit

20: Current-voltage converter

30:Analog to Digital Converter

100: Display driver

200: Display panel

CH: Sensing channel, channel

C _para : Parasitic capacitor

D1: The first diode

D2: Second diode

I _damage : overcurrent

I _PXL : Current

SD-IC: Source Driver

SL: Sensing line

SW_RST: reset signal

VREF: Reference voltage

VREFH: First reference voltage

VREFL: Second reference voltage

FIG. 1 is a block diagram showing a representation of an example of a display drive device according to an embodiment.

FIG. 2 is a block diagram showing a representation of an example of a display drive device according to an embodiment, in which the voltage limiter of FIG. 1 is configured by a diode.

FIG. 3 is a block diagram showing a representation of an example of a display drive device according to an embodiment, in which the voltage limiter of FIG. 1 is configured by a comparator.

10: Voltage limiter

12: Sensing pad

20: Current-voltage converter

30:Analog to digital converter

100: Display driver

200: Display panel

CH: sensing channel, channel

C _para : Parasitic capacitor

I _damage : overcurrent

I _PXL : Current

SD-IC: Source Driver

SL: Sensing line

Claims (11)

A display driving device includes: a sensing line configured to sense a pixel signal of a display panel; and a voltage limiter disposed in each of the sensing lines, wherein the voltage limiter senses a voltage change of the sensing line and limits the voltage level of the sensing line to a reference voltage to eliminate the influence of parasitic capacitance between the sensing line and other adjacent sensing lines. The display drive device according to claim 1, wherein the voltage limiter comprises: a first diode having an anode terminal connected to the sensing line and a cathode terminal connected to the first terminal; and a second diode having a cathode terminal connected to the sensing line and an anode terminal connected to the second terminal; wherein the reference voltage is applied to the first terminal and the second terminal. The display driving device according to claim 2, wherein when the voltage variation of the sensing line is greater than the threshold voltage of the first diode and the second diode, the voltage limiter limits the voltage level of the sensing line to the reference voltage. The display drive device according to claim 1, wherein the voltage limiter sets the reference voltage to an initial value, and the sensing line is initialized to the initial value during an initialization period. The display driving device according to claim 1, wherein the voltage limiter comprises: a first comparator configured to compare the voltage of the sensing line with a first reference voltage and output a first comparison signal; a second comparator configured to compare the voltage of the sensing line with a second reference voltage and output a second comparison signal; and an operator configured to output a reset signal by executing a logic function on the first comparison signal and the second comparison signal. A display drive device according to claim 5, wherein the operator includes an OR gate (OR) element. According to the display driving device described in claim 5, the voltage limiter further includes: a reset circuit configured to initialize the sensing line to the reference voltage in response to the reset signal. The display driving device according to claim 7, wherein when the voltage of the sensing line changes to be equal to or greater than the first reference voltage or the second reference voltage, the voltage limiter outputs the reset signal. The display drive device according to claim 5, wherein the voltage limiter sets the level of the first reference voltage and the level of the second reference voltage to be lower than the threshold voltage of the diode so as to sense a voltage change less than the threshold voltage of the diode. The display drive device as described in claim 5 further includes: an internal voltage generating circuit configured to generate multiple internal voltages and provide the multiple internal voltages to the voltage limiter, wherein at least one of the multiple internal voltages is set as the first reference voltage and the second reference voltage. The display drive device according to claim 10, wherein the internal voltage generating circuit selects a voltage corresponding to the characteristics of the display panel from among the plurality of internal voltages as the first reference voltage and the second reference voltage.