KR102379186B1 - Flexible display device having the bending sensing device and method for bending sensing the same - Google Patents

Abstract

The present invention relates to a flexible display device having a bending sensing device capable of individually sensing bending of bending regions in a flexible display device having a bending structure, and a bending sensing method, and the flexible display device having the bending sensing device according to the present invention. to embed the first to fourth bending sensors in the first bending region and the second bending region, and to embed the first and second reference resistors in the non-bending region, so that the first to fourth bending sensors and the first and two Wheatstone bridges using the second reference resistor.

Description

A flexible display device having a bending sensing device and a bending sensing method {Flexible display device having the bending sensing device and method for bending sensing the same}

The present invention relates to a flexible display device, and more particularly, to a flexible display device having a bending sensing device capable of individually sensing bending of bending regions in a flexible display device having a bending structure and a bending sensing method.

The field of display that processes and displays a large amount of information has developed rapidly, and various display devices are being developed.

Examples of the display device include a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an electroluminescence display device (ELD). Luminescence Display Device), etc. have been developed, and these display devices are evolving in the direction of pursuing thinner, lighter, and lower power consumption. However, since the above-mentioned display devices use a glass substrate to withstand high heat generated during the manufacturing process, there is a limit in realizing lightweight and thinning or flexibility.

Accordingly, in recent years, a flexible display device manufactured to maintain display performance even when bent like paper by using a flexible material that can be folded and unfolded, such as a plastic film, instead of a conventional inflexible glass substrate is the next generation. It is emerging as a flat panel display device. Such a flexible display device is not only thin and light, but also has strong impact resistance, and can be bent or bent, so that it can be folded or rolled to be portable. In addition, since it has the advantage that it can be manufactured in various forms, its utility can be expanded in the future.

This flexible display technology has passed the experimental stage and is now on the verge of mass-production. The flexible display based on the flexible display is expected to provide a new type of input/output interface different from the conventional electronic devices having a rigid display, thereby providing a new user experience.

Recently, a device for detecting a shape of a flexible display capable of disposing a plurality of bending sensors at the edge of the flexible display device and detecting a shape of the flexible display device from the plurality of bending sensors has been proposed. There has been a bar (refer to Korean Patent Application Laid-Open No. 10-2014-0132569).

1 is a diagram illustrating a conventional flexible display device in which a plurality of bending sensors are disposed, and FIG. 2 is a diagram illustrating a configuration of a conventional measurement unit. 3A and 3B are diagrams illustrating a strain gauge circuit, and FIG. 4 is a block diagram illustrating a detailed configuration of the microprocessor of FIG. 2 .

Referring to FIG. 1 , bending sensors 101 and 102 capable of detecting bending of the flexible display panel are disposed along an edge (or edge) of the flexible display device 100 at regular intervals.

The bending sensors 101 and 102 are strain gauges. The strain gauge has a characteristic in which resistance between terminals changes according to physical elongation and contraction. In order to detect the shape of the flexible display device 100 using such a sensor, a measurement unit in charge of signal processing is required, which may be implemented as shown in FIG. 2 .

A conventional measurement unit may include a bridge circuit 210 , an amplifier 220 , an analog to digital converter (ADC) 230 , and the like.

The bridge circuit 210 is implemented as a Wheatstone bridge including one or more strain gauges. That is, since most of the resistance variations of the strain gauges are very small, as shown in FIG. 2 , a Wheatstone bridge is configured to convert a change in resistance into a change in voltage, and then amplify it through the amplifier 220 .

On the other hand, the Wheatstone bridge uses a quarter-bridge circuit for detecting a change in one strain gauge as shown in FIG. 3A, or the change in tension and contraction is reversed as shown in FIG. 3B. A half-bridge circuit is used to detect changes in a pair of strain gages. That is, when one strain gauge sensor is mounted on both sides of the arrangement position where each of the bending sensors 101 and 102 is disposed in the flexible display panel 100 of FIG. It is possible to obtain the effect of improving the sensitivity of the sensor.

On the other hand, when the bridge circuit 210 of FIG. 2 is configured as a quarter bridge circuit as shown in FIG. 3A , R1, R2, R3 and one strain gauge 330a may constitute the quarter bridge circuit 320a. In addition, when power is distributed to each resistor by the power supply of the power supply unit 310 , the magnitude of the voltage output from the bridge circuit varies according to a change in the resistance of the strain gauge 330a.

In addition, when the bridge circuit 210 of FIG. 2 is configured as a half-bridge circuit as shown in FIG. 3b, R1, R3 and two strain gauges 330b may constitute the half-bridge circuit 320b, When power is distributed to each resistor by the power supply of the power supply unit 310 , the magnitude of the voltage output from the bridge circuit changes according to a change in the resistance of each strain gauge 330b and 330c. The shape of the flexible display device is sensed by the voltage value output from the bridge circuit.

The output voltage of the bridge circuit 210 is input to the amplifier 220 , the small voltage change is amplified into a large voltage value, and then input to the analog-to-digital converter 230 . The analog-to-digital converter 230 converts an analog signal into a digital value and outputs it to a microprocessor 240 . The microprocessor 240 detects the shape of the flexible display panel 100 from measurement values sensed by the respective sensors.

A detailed configuration of the microprocessor 240 is shown in FIG. 4 .

That is, the microprocessor 240 includes a noise filter 402, a channel compensator 403, a curve point detector 404, and a VGA gain controller 405 ), a bending line detector (Bending Line Detector; 406), a slope compensator (Slope Compensator; 407), a feature extractor (408) and the like.

The noise filter unit 402 functions to filter a change in a sensor value caused by a factor other than a user's bending motion in the flexible display panel 100 from a meaningful signal.

The channel compensator 403 functions to compensate for a deviation between sensors disposed on the flexible display panel 100 , and may compensate for deviation between different sensors for each of the flexible display panels 100 . there is.

The inflection point detection unit 404 analyzes the measured values (eg, voltage values) sensed from the sensors 101 and 102 arranged in a line on each side (edge), and the inflection point formed on each edge (ie, each outer region) to extract the location and features of

The gain adjusting unit 405 is configured to output an amplifier (such as an output of each of the sensors 101 and 102 that is smaller than a predetermined reference value or out of an input range of the analog-to-digital converter 230 based on the output value of the inflection point detection unit 404). 220) (eg, a variable gain amplifier), when it is necessary to adjust the gain, an appropriate gain control signal is generated and provided to the amplifier 220 .

Meanwhile, the inflection point information detected from each of the outer regions 111 , 112 , 113 and 114 by the inflection point detector 404 is input to the bending line detector 406 and is used to detect the shape of the flexible display panel 100 .

The inclination compensator 407 compensates for bending information of the bending line based on the inclination information of the bending line.

The feature extraction unit 408 extracts the positions, inclinations, angles, thicknesses and directions of the detected bending lines and transmits them to the upper layer.

However, the conventional bending sensing device and bending sensing method of the flexible display device have the following problems.

First, the conventional bending sensing device of the flexible display device senses each bending area in the double bending (in-bending, in-folding and out-bending, our-folding occur at the same time) in the flexible display device. In this case, since it is necessary to configure a bridge circuit by using one bending sensor (strain gauge) and three resistors (R1, R2, R3) for each sensor as a set, the design area increases and the unit price increases.

Second, a divider (Mux) is required to sense each bending area.

Third, when controlling the bending sensor (strain gauge) by position using the divider as described above, the three resistors R1, R2, R3 should be the same as the resistance of the bending sensor, but the wiring connected to the bending sensor It is practically impossible to apply because the resistance of each bending sensor is different due to the difference in length.

The present invention is to solve such a conventional problem, a bending sensing device for sensing bending by making two Wheatstone bridges by embedding two bending sensors in each bending area and separately embedding a reference resistor in a non-bending area. An object of the present invention is to provide a flexible display device having a bending sensing method.

In order to achieve the above object, a flexible display device having a bending sensing device according to the present invention includes first to fourth bending sensors embedded in a first bending area and a second bending area, and first and second bending sensors in the non-bending area. A second reference resistor is built in, and two Wheatstone bridges are constructed using the first to fourth bending sensors and the first and second reference resistors.

Here, the first to fourth bending sensors and the first and second reference resistors are formed of a conductive material used in a process of a film constituting a flexible display device.

The first to fourth bending sensors are formed on both sides or one side of the first or second bending region, and the first and second reference resistors are formed on both sides or one side of the non-bending region.

The two Wheatstone bridge circuits include a first Wheatstone bridge circuit including the first to third bending sensors and the second reference resistor, and the second to fourth bending sensors and the first reference resistor. and a second Wheatstone bridge circuit.

The first Wheatstone bridge circuit includes a first connection part between a power supply terminal to which the first bending sensor and the second reference resistor are connected in series through a first load, and the second bending sensor and the third bending sensor A second connection part is connected in series through two rods, the first connection part and the second connection part are connected in parallel to each other, and an output terminal is formed at the first rod and the second rod.

The second Wheatstone bridge circuit includes the second connection part and a third connection part in which the first reference resistor and the fourth bending sensor are connected in series through a third rod, and the second connection part and the third connection part are connected to each other in parallel, and an output terminal is formed at the second load and the third load.

Meanwhile, according to the present invention, there is provided a bending sensing method of a flexible display device having a bending sensing device to achieve the above object, wherein the output voltage V1 of the first Wheatstone bridge circuit and the second Wheatstone bridge circuit are The output voltage V2 is detected and compared with a lookup table, and the bending state of each bending region is determined by the value of the lookup table matching the output voltages V1 and V2 of the first and second Wheatstone bridges. do.

In addition, in the bending sensing method of a flexible display device having a bending sensing device according to the present invention for achieving the above object, the first bending sensor and the second reference resistor are connected in series between power terminals through a first load. and a second connection part in which the second bending sensor and the third bending sensor are connected in series through a second rod, wherein the first connection part and the second connection part are connected in parallel to each other, A first Wheatstone bridge circuit in which an output terminal is formed between a load and a second load, the second connection part, and a third connection part through which the first reference resistor and the fourth bending sensor are connected in series through a third load; , wherein the second connection part and the third connection part are connected in parallel to each other, and in the flexible display device having a bending sensing device including a second Wheatstone bridge circuit in which an output terminal is formed at the second rod and the third rod, the first and the first and third divided voltages V3 and V5 of each of the third connectors are detected, compared with the lookup table, and the values of the lookup table matched to the first and third divided voltages V3 and V5 are matched. to determine the bending state of each bending area.

The flexible display device and the bending sensing method having the bending sensing device according to the present invention having the above characteristics have the following effects.

First, in a flexible display having a bending area, two bending sensors are built in each bending area and two reference resistors are separately built in a non-bending area to form two Wheatstone bridges to sense bending. The bending state can be accurately judged.

Second, since two Wheatstone bridge circuits are formed by overlapping bending sensors embedded in the flexible display device, the number of bending sensors and reference resistors can be reduced, thereby reducing unit cost.

Third, since the present invention embeds the bending sensor in the bending region inside the flexible display device, the bending sensor and the reference resistor can be formed with the conductive material used in the forming process of forming the flexible display device, so an additional process is not required. Also, the unit price can be lowered.

1 is a view showing a conventional flexible display panel on which a plurality of bending sensors are disposed;
2 is a diagram showing the configuration of a conventional measurement unit;
3A and 3B show a strain gauge circuit, wherein FIG. 3A is a quarter-bridge circuit, and FIG. 3B is a half-bridge circuit diagram.
4 is a block diagram showing a detailed configuration of the microprocessor of FIG.
5 is an explanatory diagram for explaining a bending sensing principle of a flexible display device having a bending sensing device according to the present invention;
6 is an explanatory view for explaining a case in which a bending sensor is mounted in each bending area in the flexible display device having a bending structure according to the present invention;
7 is a block diagram of a bending sensor or reference resistance according to the present invention;
8 is an explanatory diagram of a bridge circuit configuration of a flexible display device having a bending sensing device according to the present invention;
9 is a bridge circuit diagram of a flexible display device having a bending sensing device according to the present invention;
10 is a measurement configuration diagram of a bridge circuit of a flexible display device having a bending sensing device according to the present invention;
11 is a flowchart of the operation of the measurement unit according to the present invention;
12 is a block diagram of a lookup table according to the first embodiment of the present invention;
13 is a block diagram of a lookup table according to a second embodiment of the present invention;

A flexible display device having a bending sensing device and a bending sensing method according to the present invention having the above characteristics will be described in more detail with reference to the accompanying drawings.

5 is an explanatory diagram for explaining a bending sensing principle of a flexible display device having a bending sensing device according to the present invention, and FIG. 6 is an explanatory diagram illustrating a bending sensor in each bending region in the flexible display device having a bending structure according to the present invention. It is an explanatory diagram for explaining a case where the sensor has been used, and FIG. 7 is a configuration diagram of a bending sensor according to the present invention.

First, the present invention relates to a flexible display device having a multi-bending structure. For convenience of description, a flexible display device having a double bending structure will be described as an example.

As shown in FIG. 5 , the flexible display device having a double bending structure is bent at two positions. Since each of the two bending positions may be bent inward or outward, the screen size of the flexible display may be variously adjusted.

In FIG. 5, region D between regions A and B and region E between regions B and C are bending (bending) regions.

In the flexible display device having the bending sensing device of the present invention, as shown in FIG. 6 , two bending sensors R1 and R3 are installed on both sides of the first bending area D of the flexible display device, , two bending sensors R2 and R4 are installed on both sides of the second bending area E of the flexible display device, and the reference resistance Rref1 is disposed on both sides of the non-bending area (one of A, B, and C). , Rref2) is installed. In FIG. 6 , reference resistors Rref1 and Rref2 are installed in region B located between the double bending regions.

In the above, all of the bending sensors R1-R4 and the reference resistors Rref1 and Rref2 are built in the flexible display device.

In general, a flexible display device is composed of a plurality of films (layers), such as a back plate, a pixel array (TFT+Encap), a touch sensor (Touch), and a cover plate (Cover+Pol).

Accordingly, the flexible display device having the bending sensing device according to the present invention is embedded in the pixel array film (layer) or the touch sensor film (layer), and the bending sensor is a conductive material used in the pixel array process or the touch sensor process. and a reference resistance, etc.

In FIG. 6 , it has been described that two bending sensors are built-in at both sides of each of the bending areas D and E, but the present invention is not limited thereto, and two bending sensors may be built-in at one side of each of the bending areas D and E. In addition, although it has been described that two reference resistors are also formed on both sides of the non-bending region, the present invention is not limited thereto, and two reference resistors may be built in one side of the non-bending region.

As shown in FIG. 7 , the bending sensors R1-R4 are formed of a conductive material having electrical resistance, and have physical elongation and contraction, that is, a degree of bending (bending angle) between terminals. It is a sensor whose resistance value is variable. Similarly, although the reference resistors Rref1 and Rref2 are formed of a conductive material having electrical resistance as shown in FIG. 7 , they are formed in a non-bending region, so that their resistance values do not change.

8 is an explanatory diagram of a bridge circuit configuration of a flexible display device having a bending sensing device according to the present invention, FIG. 9 is a bridge circuit diagram of a flexible display device having a bending sensing device according to the present invention, and FIG. It is a measurement configuration diagram of a bridge circuit of a flexible display device having a bending sensing device.

As described above, four bending sensors R1-R4 and two reference resistors Rref1 and Rref2 are installed to configure a total of two Wheatstone bridges as shown in FIGS. 8 and 9 .

That is, the first Wheatstone bridge circuit is composed of three bending sensors R1, R2, R3 and one reference resistor Rref2, and three bending sensors R2, R3, R4 and one reference resistor Rref1 ) to configure the second Wheatstone bridge circuit. The two bending sensors R2 and R3 overlap the first Wheatstone bridge circuit and the second Wheatstone bridge circuit.

The first Wheatstone bridge circuit includes a first connection part in which a first bending sensor (R1) and a second reference resistor (Rref2) are connected in series between a power supply terminal (12V) through a first load, and a second bending sensor ( R2) and the third bending sensor R3 have a second connection part connected in series through a second rod, wherein the first connection part and the second connection part are connected in parallel to each other, and an output terminal is connected to the first rod and the second rod this is formed

In addition, the second Wheatstone bridge circuit includes the second connection part in which a second bending sensor (R3) and a second bending sensor (R3) are connected in series through the second load between a power supply terminal (12V); The first reference resistor Rref1 and the fourth bending sensor R4 have a third connection part connected in series through a third rod, the second connection part and the third connection part are connected in parallel to each other, and the second rod and the second connection part are connected in parallel. 3 The output stage is formed on the rod.

The outputs of the first and second Wheatstone bridge circuits configured as described above are processed through the measurement unit shown in FIG. 10 to determine the bending state of each bending region.

That is, as shown in FIG. 10 , the measuring unit of the present invention may include an amplifier (G+50), an analog to digital converter (ADC), and a microprocessor (MCU).

Since the amount of change in resistance of the bending sensors is mostly very small, as described above, a Wheatstone bridge is configured to convert a change in resistance into a change in voltage, and then amplify it through an amplifier (G=50).

The analog-to-digital converter (ADC) converts the analog signal amplified by the amplifier into a digital signal and outputs it to the microprocessor (MCU).

That is, the output voltages of the first and second Wheatstone bridges are amplified by the amplifier, converted into digital signals by the analog-to-digital converter (ADC), and input to the microprocessor (MCU).

The microprocessor (MCU) compares the input digital values of the output voltages of the first and second Wheatstone bridges with data stored in a lookup table to match the output voltages of the first and second Wheatstone bridges ( The bending state of the flexible display device is determined according to the matched value.

Although not shown in FIG. 10, an analog filter may be further provided between the amplifier and the analog-to-digital converter, and a digital filter between the analog-to-digital converter and the microprocessor.

Hereinafter, the operation of the measurement unit will be described in more detail as follows.

11 is a flowchart of an operation of the measurement unit according to the present invention, and FIG. 12 is a configuration diagram of a lookup table according to the first embodiment of the present invention.

First, in the bridge circuit configured as described above, the output voltage V1 of the first Wheatstone bridge circuit and the output voltage V2 of the second Wheatstone bridge circuit are as follows.

Although the power supply stage is set to 12V in FIG. 9, the present invention is not limited thereto, and various voltages may be set.

As described above, the output voltage V1 of the first Wheatstone bridge circuit and the output voltage V2 of the second Wheatstone bridge circuit are amplified by an amplifier (G=50) and then the analog-to-digital converter (ADC) is converted into a digital signal and input to the microprocessor (MCU) (1S).

At this time, if the amplifier amplifies with a gain value that is too high, the analog-to-digital converter (ADC) cannot convert the input analog value to a digital value. The analog value output from the amplifier is made to be within the normal range of the analog-to-digital converter (ADC) (2S, 3S).

The microprocessor (MCU) compares the digital value input from the analog-to-digital converter (ADC) with the initial digital value while storing the initial digital value in a state in which the flexible display device is not bent, and the input value is If it is the same as the initial value, the flexible display device determines that it is not bent and continues to compare the input value with the initial value (4S, 5S).

If the input value is different from the initial value, the output voltage V1 of the first Wheatstone bridge circuit and the output voltage V2 of the second Wheatstone bridge circuit are compared with a lookup table as shown in FIG. 12 . Accordingly, the bending state of the flexible display device is determined according to the values matched to the output voltages V1 and V2 of the first and second Wheatstone bridges (6S, 7S). In FIG. 12 , the unit of the output voltage V1 of the first Wheatstone bridge circuit and the output voltage V2 of the second Wheatstone bridge circuit is mV.

That is, in FIG. 12 , it is assumed that the flexible display device is not bent when the angles D and E are 180 degrees, and the microprocessor (MCU) sets the V1 and V2 values ( 0, 0) is stored as an initial digital value, and, for example, the input output voltage V1 of the first Wheatstone bridge circuit and the output voltage V2 of the second Wheatstone bridge circuit are - Assuming 6.234 mV, the microprocessor (MCU) determines that the first bending region D and the second bending region are bent 90 degrees inward, and the output voltage V1 of the first Wheatstone bridge circuit is Assuming that the output voltage V2 of the second Wheatstone bridge circuit is 6.234 mV, respectively, the microprocessor (MCU) bends the first bending region D and the second bending region 90 degrees (270 degrees) outward. judged to have been

Meanwhile, in the bridge circuit of FIG. 9 , the bending state of the flexible display may be determined by measuring the divided voltages V3 , V4 , and V5 of the first to third connectors.

13 is a block diagram of a lookup table according to a second embodiment of the present invention.

That is, in the bridge circuit of FIG. 9 , the first divided voltage V3 between the first bending sensor R1 and the second reference resistor Vref2 of the first connection part, and the second bending sensor ( The second divided voltage V4 between R2) and the third bending sensor R3 and the third divided voltage V5 between the first reference resistor Vref1 of the third connection part and the fourth bending sensor R4 are same as

In FIG. 6 , when the first bending region D is bent inward (in bending), the resistance values of the first bending sensor R1 and the third bending sensor R3 decrease, and the first bending region D ) is bent outwardly, the resistance values of the first bending sensor R1 and the third bending sensor R3 increase. Similarly, when the second bending region E is bent inward (in bending), resistance values of the second bending sensor R2 and the fourth bending sensor R4 are decreased, and the second bending region E is bent inward. When bending toward the outside (out bending), resistance values of the second bending sensor R2 and the fourth bending sensor R4 increase.

Since the resistance values of the bending sensors vary according to the bending state of the first and second bending regions D and E, the divided voltage V3 is changed according to the bending state of the first and second bending regions D and E. , V4, V5) are also variable.

As shown in FIG. 13 , the first and third divided voltages V3 and V5 are varied in two levels, and the second divided voltage V4 is varied in three or more levels. Accordingly, bending states of the first and second bending regions D and E may be determined by using the first divided voltage V3 and the third divided voltage V5.

Therefore, the first and third divided voltages V3 and V5 are measured by the method described with reference to FIGS. 10 and 11, and the first and third divided voltages are compared with respective initial voltages to compare the first and third divided voltages. 2 The bending state of the bending regions D and E is determined.

In FIG. 13 , a state in which the first and second bending regions D and E are not bent is set as an initial digital value, and according to variable amounts of the first and third divided voltages V3 and V5 It may be determined whether the first and second bending regions D and E are bent inwardly or outwardly.

For example, in FIG. 13 , when the first divided voltage V3 is slightly decreased, it is determined that the first bending region is bent outward, and when the first divided voltage V3 is greatly increased, it is determined that the first bending region is bent. It is judged that this is bent inward. Also, when the third divided voltage V5 is slightly increased, it is determined that the second bending region is bent outward, and when the third divided voltage V5 is greatly decreased, the second bending region is bent inward. judged to have been

Accordingly, the bending state is determined according to the amount of change of the first and third divided voltages V3 and V5.

The present invention described above is not limited to the above-described embodiments and the accompanying drawings, and it is common in the technical field to which the present invention pertains that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be clear to those who have the knowledge of

Claims (8)

In a flexible display device having a bending structure,
first and third bending sensors embedded in the first bending area;
second and fourth bending sensors embedded in the second bending area;
and first and second reference resistors embedded in the non-bending region;
Bending forming a first Wheatstone bridge circuit using the first to third bending sensors and the second reference resistance, and configuring a second Wheatstone bridge circuit using the second to fourth bending sensors and the first reference resistance A flexible display having a sensing device. The method of claim 1,
and the first to fourth bending sensors and the first and second reference resistors are formed of a conductive material used in a process of a film constituting the flexible display device. The method of claim 1,
The first to fourth bending sensors are formed on both sides or one side of the first or second bending region, and the first and second reference resistors are formed on both sides or one side of the non-bending region. flexible display. delete The method of claim 1,
The first Wheatstone bridge circuit includes: a first connection part connected in series between the first bending sensor and the second reference resistor through a first load between power terminals;
The second bending sensor and the third bending sensor have a second connection part connected in series through a second rod, and the first connection part and the second connection part are connected in parallel to each other, and are connected to the first rod and the second rod. A flexible display device having a bending sensing device on which an output end is formed. The method of claim 1,
The second Wheatstone bridge circuit comprises:
and the second connection unit in which the second bending sensor and the third bending sensor are connected in series through the second load between power terminals;
The first reference resistor and the fourth bending sensor have a third connection part connected in series through a third rod, and the second connection part and the third connection part are connected in parallel to each other, and are connected to the second rod and the third rod. A flexible display device having a bending sensing device on which an output end is formed. first and third bending sensors embedded in the first bending region; second and fourth bending sensors embedded in the second bending region; and first and second reference resistors embedded in the non-bending region; A bending sensing device in which a first Wheatstone bridge circuit is constituted by first to third bending sensors and the second reference resistor, and a second Wheatstone bridge circuit is constituted by the second to fourth bending sensors and the first reference resistor. In a bending sensing method of a flexible display having a
detecting an output voltage (V1) of the first Wheatstone bridge circuit and an output voltage (V2) of the second Wheatstone bridge circuit;
comparing the output voltage (V1) of the first Wheatstone bridge circuit and the output voltage (V2) of the second Wheatstone bridge circuit with a lookup table; And,
and determining a bending state of each bending region by a value of a lookup table that matches the output voltages V1 and V2 of the first and second Wheatstone bridges. first and third bending sensors embedded in the first bending region, second and fourth bending sensors embedded in the second bending region, and first and second reference resistors embedded in the non-bending region;
A first connection part between the power supply terminals in which the first bending sensor and the second reference resistance are connected in series through a first load, and a second connection in which the second bending sensor and the third bending sensor are connected in series through a second load a first Wheatstone bridge circuit including a connection part, wherein the first connection part and the second connection part are connected in parallel to each other, and an output terminal is formed at the first rod and the second rod;
The second connection part, and a third connection part in which the first reference resistor and the fourth bending sensor are connected in series through a third rod, the second connection part and the third connection part are connected in parallel to each other, and the second connection part A bending sensing method for a flexible display device having a bending sensing device constituting a second Wheatstone bridge circuit in which an output terminal is formed on a rod and a third rod, the bending sensing method comprising:
detecting first and third divided voltages (V3, V5) of the first and third connections, respectively;
comparing the first and third divided voltages (V3, V5) with a lookup table; And,
and determining a bending state of each bending region by a value of a lookup table that matches the first and third divided voltages (V3, V5).

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