Electrophoretic display apparatus

Abstract

This electrophoretic display apparatus comprises: a common electrode to which a common voltage is supplied; a pixel electrode disposed to correspond to the common electrode; a plurality of color pigments provided between the common electrode and the pixel electrode and dispersed in a solvent; a data driving unit for supplying a data voltage to the pixel electrode; a power supply unit including a plurality of power sources that supplies a plurality of voltages to the data driving unit; and a reverse polarity prevention unit configured to prevent voltage reversal between the plurality of power sources when power is shut off.

Description

Electrophoretic display device

[0001] The disclosed invention relates to an electrophoretic display device.

[0002] Electrophoretic Displays (EPDs) are display technologies that utilize the electrophoretic phenomenon to display characters or images by moving charged microparticles using an electric field. When an electric field is applied, the particles move and colors appear, and since the state is maintained even after the electric field is removed, no power is consumed in static images. Thanks to these low-power characteristics, they are widely used in electronic paper (E-paper), such as in e-book readers.

[0003] The electrophoretic display device is driven by multiple power sources. These multiple power sources are turned on or off according to a predetermined sequence.

[0004] When power is supplied, the electrophoretic display device is turned on sequentially starting from the lowest voltage according to the power supply sequence, and when power is cut off, it is turned off sequentially starting from the highest voltage according to the power cut-off sequence.

[0005] For example, when the power is cut off, a voltage reversal phenomenon may occur due to the difference in discharge rates between the first voltage (-3.5V) and the second voltage (-19V), which causes a short circuit in the parasitic diode within the data driver, resulting in damage to the data driver.

[0006] Previously, to prevent this, it was necessary to wait tens of seconds until natural discharge was completed, which was a factor that reduced the usability of the product.

[0007] The present disclosure provides an electrophoretic display device capable of preventing damage caused by reverse voltage that may occur when changing the voltage levels of a plurality of power sources and shortening the screen switching time while ensuring circuit stability.

[0008] The technical problems to be solved in this document are not limited to those mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art to which this invention belongs from the description below.

[0009] An electrophoretic display device according to one embodiment of the present disclosure may include: a common electrode to which a common voltage is supplied; a pixel electrode disposed corresponding to the common electrode; a plurality of color pigments disposed between the common electrode and the pixel electrode and dispersed in a solvent; a data driving unit for supplying a data voltage to the pixel electrode; a power supply unit including a plurality of power sources for supplying a plurality of voltages to the data driving unit; and a reverse prevention unit configured to prevent voltage reversal between the plurality of power sources when the power is cut off.

[0010] An electrophoretic display device according to another embodiment of the present disclosure may include: a power supply unit that generates a first power source that outputs a first voltage and a second power source that outputs a second voltage higher than the first voltage; and a reverse prevention unit configured to short-circuit the first power source and the second power source based on the occurrence of a reversal of the first voltage and the second voltage when the power is cut off.

[0011] FIG. 1 is a configuration diagram of an electrophoretic display device according to one embodiment.

[0012] FIG. 2 illustrates a pixel of a display panel of an electrophoretic display device according to one embodiment.

[0013] FIG. 3 is a driving circuit of an electrophoretic display device according to one embodiment.

[0014] FIG. 4 illustrates a reverse prevention unit of a power supply unit of an electrophoretic display device according to one embodiment.

[0015] FIG. 5 illustrates that a reversal occurs between power sources in an electrophoretic display device according to one embodiment.

[0016] FIG. 6 illustrates an example of a reverse prevention unit of a power supply unit of an electrophoretic display device according to one embodiment.

[0017] FIG. 7 illustrates the operation of a Schottky barrier diode in a reverse prevention unit of an electrophoretic display device according to one embodiment.

[0018] FIG. 8 is a graph showing the characteristics of Schottky barrier diodes by material in the reverse prevention section of an electrophoretic display device according to one embodiment.

[0019] FIG. 9 illustrates another example of a reverse prevention unit of a power supply unit of an electrophoretic display device according to one embodiment.

[0020] FIG. 10 illustrates the operation of an ideal diode equivalent circuit in a normal voltage state in a reverse prevention unit of an electrophoretic display device according to one embodiment.

[0021] FIG. 11 illustrates the operation of an ideal diode equivalent circuit in a reverse voltage state in a reverse prevention unit of an electrophoretic display device according to one embodiment.

[0022] FIG. 12 illustrates the results before and after the application of a reverse prevention unit to an electrophoretic display device according to one embodiment.

[0023] The embodiments described in this specification and the configurations illustrated in the drawings are merely preferred examples of the disclosed invention, and various modifications that may replace the embodiments and drawings of this specification may exist at the time of filing this application.

[0024] Additionally, the same reference numerals or symbols presented in each drawing of this specification represent parts or components that perform substantially the same function.

[0025] Additionally, the singular form of the noun corresponding to the item may include one or multiple items, unless the relevant context clearly indicates otherwise.

[0026] Additionally, in this document, each of the phrases such as "A or B", "at least one of A and B", "at least one of A or B", "A, B or C", "at least one of A, B and C", and "at least one of A, B, or C" may include any one of the items listed together in the corresponding phrase, or all possible combinations thereof.

[0027] Additionally, the terms "part," "module," and "component" may be implemented in hardware or software. Depending on the embodiments, a plurality of "parts," "modules," and "components" may be implemented as a single component, or a single "part," "module," or "component" may include a plurality of components.

[0028] Furthermore, the terms used in this specification are for describing embodiments and are not intended to limit or / or restrict the disclosed invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this specification, terms such as "comprising" or "having" are intended to indicate the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and do not preclude the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0029] Additionally, terms including ordinal numbers, such as "first," "second," etc., used herein may be used to describe various components, but said components are not limited by said terms, and said terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term "and / or" includes a combination of a plurality of related described items or any one of a plurality of related described items.

[0030] Where any (e.g., 1st) component is referred to as "coupled" or "connected" to another (e.g., 2nd) component, with or without the terms "functionally" or "communicationly," it means that said any component may be connected to said other component directly (e.g., via a wire), wirelessly, or through a third component.

[0031] When it is said that a component is "connected," "combined," "supported," or "in contact" with another component, this includes not only cases where the components are directly connected, combined, supported, or in contact, but also cases where they are indirectly connected, combined, supported, or in contact through a third component.

[0032] When it is said that a component is located "on" another component, this includes not only cases where one component is in contact with the other, but also cases where another component exists between the two components.

[0033] Meanwhile, terms such as "up / down direction" and "front / back direction" used in the following description are defined based on the drawings, and the shape and position of each component are not limited by these terms. For example, the terms "front" and "rear" below may each be defined based on the X direction shown in the drawings. The terms "up" and "down" below may each be defined based on the Z direction shown in the drawings. The terms "left direction" and "right direction" below may be defined based on the Y direction shown in the drawings. The term "vertical direction" below may each refer to the Z direction shown in the drawings, and the term "horizontal direction" below may each refer to the Y direction shown in the drawings.

[0034] Hereinafter, embodiments according to the present invention will be described in detail with reference to the attached drawings.

[0035] FIG. 1 is a configuration diagram of an electrophoretic display device according to one embodiment.

[0036] Referring to FIG. 1, the electrophoretic display device (1) is a device capable of visually displaying characters or images. In the following examples, the electrophoretic display device (1) is an electronic paper, but is not limited thereto. The display device (10) is not limited in form as long as it is a device capable of visually displaying images.

[0037] The electrophoretic display device (1) may include a display panel (10), a panel display driver integrated circuit (PDDI) (20), a control unit (30), and a power supply unit (40).

[0038] The display panel (10) may include m / n pixels (11).

[0039] A display panel (10) may be formed such that a plurality of data lines (D1 to Dm) and a plurality of gate lines (G1 to Gn) intersect. A TFT may be electrically connected to each pixel (11) in the intersecting area.

[0040] The panel driver (20) can transmit electrical signals to each pixel (11) in the correct time and order according to the control of the control unit (30).

[0041] The control unit (30) may receive a control signal from the central processing unit (AP or CPU) of the electrophoretic display device (1). The control unit (30) may include a memory, a processor, and a control circuit board on which these are mounted.

[0042] The control unit (30) can generate a driver control signal (gate control signal, data control signal) for controlling the panel driver (20) based on the provided control signal and provide the driver control signal to the panel driver (20).

[0043] The power supply unit (40) can supply power to the display panel (10), the panel driver (20), and the control unit (30).

[0044] When the power supply unit (40) turns on the power of the electrophoretic display device (1), it can generate voltages required for driving the display panel (10) using the input power (Vin). The power supply unit (40) can supply and cut off multiple driving voltages according to the power control signal provided by the control unit (30) so that there is no section where the voltages are reversed.

[0045] The power supply unit (40) can supply driving voltages to the panel driver (20). For example, the power supply unit (40) can generate a plurality of driving voltages to apply an electric field to a charged color pigment of a pixel (11) of a display panel (10) and supply them to the panel driver (20) to output a waveform for determining the position of the charged color pigment.

[0046] The panel driver (20) may include a gate driver (21) and a data driver (22).

[0047] The gate driver (21) can supply a gate voltage to a plurality of gate lines (G1 to Gn) of the display panel (10) according to a gate control signal provided from the control unit (30). The gate driver (21) can select the TFT of the corresponding line and turn it on or off.

[0048] When the gate driving unit (21) applies a gate voltage to the gate lines (G1 to Gn), the pixel (11) of the corresponding line can be driven as the TFT is turned on or turned off by the applied gate voltage.

[0049] The data driving unit (22) can supply waveforms to a plurality of data lines (D1 to Dm) of the display panel (10) according to a data control signal provided from the control unit (30).

[0050] The electrophoretic display device (1) can supply a waveform to a specific pixel (11) using a gate driver (21) and a data driver (22). The waveform can be generated in various versions by reflecting the characteristics of the charged color pigment of the pixel (11) and the solvent, the characteristics of the solvent manufacturer's unique manufacturing process, and the operating temperature. For example, control information for implementing a waveform to display white, blue, red, and yellow, etc., on the pixel (11) may be stored in advance.

[0051] The control unit (30) can provide control information for implementing a waveform to the gate driver (21) and the data driver (22). The control unit (30) can perform control to create a waveform implemented as a sequence of positive (+) and negative (-) voltages in a section defined as a series of reset section and write section to move charged color pigments to a desired position.

[0052] The data driving unit (22) can generate a waveform using waveform control information from the control unit (30) and a driving voltage supplied from the power supply unit (40), and can supply the generated waveform to a plurality of data lines (D1 to Dm).

[0053] FIG. 2 illustrates a pixel of a display panel of an electrophoretic display device according to one embodiment.

[0054] Referring to FIG. 2, the display panel (10) may include a pixel electrode (12) provided on a lower substrate and a common electrode (13) on an upper substrate.

[0055] The pixel electrode (12) and the common electrode (13) can be positioned opposite each other.

[0056] The common electrode (13) provided on the upper substrate can be placed on the side visible to the user as a transparent electrode layer.

[0057] An electric field can be formed in the pixel (11) by the potential difference between the common electrode (13) and the pixel electrode (12). This electric field can guide the color pigments provided between the common electrode (13) and the pixel electrode (12) to a desired position, thereby enabling the realization of a desired color through external light reflection.

[0058] Between the pixel electrode (12) and the common electrode (13), charged color pigments can be dispersed in a solvent to form an electrophoretic layer.

[0059] The color pigments of the electrophoretic layer can each be charged with positive (+) or negative (-) charges of different polarities and capacities. When a waveform is applied through the data driver (22), the color pigments move to a specific location due to the difference in electric field with the common electrode (13), and a desired color can be realized using external light reflection.

[0060] For example, multiple color pigments may include four color particles (W, B, R, Y).

[0061] The four color particles (W, B, R, Y) may include two pairs of particles with opposite polarities.

[0062] The first pair may include a white particle (W) and a blue particle (B). The white particle (W) may have a high positive (+) charge, and the blue particle (B) may have a high negative (-) charge.

[0063] The second pair may include a red particle (R) and a yellow particle (Y). The red particle (R) may have a low positive (+) charge, and the yellow particle (Y) may have a low negative (-) charge.

[0064] In various embodiments, the white particles (W), blue particles (B), red particles (R), and yellow particles (Y) can be of various shapes.

[0065] The four color particles (W, B, R, Y) can be mixed to adjust the color state. The four colors (W, B, R, Y) can be extended to other colors in addition to white, blue, red, and yellow.

[0066] For example, when a high negative (-) potential is applied to the pixel electrode (12) compared to the common voltage of the common electrode (13), a high electric field is generated, causing blue particles (B) with a high negative (-) charge to move toward the common electrode (13) and white particles (W) with a high positive (+) charge to move toward the pixel electrode (12). Since red (R) and yellow particles (Y) have a low charge amount, they receive less force in the same electric field than white particles (W) with a high positive (+) charge and blue particles (B) with a high negative (-) charge, and the distance traveled to the common electrode (13) is shorter relative to the time. Finally, the movement of blue particles is concentrated toward the common electrode (13) for a specific period of time, and is displayed to the user as blue through external light reflection.

[0067] In addition, when a high positive (+) potential is applied to the pixel electrode (12) compared to the common voltage of the common electrode (13), a high electric field of opposite polarity is generated, and the particle distribution appears opposite to the previous one. Finally, it is displayed to the user as white through external light reflection.

[0068] Additionally, when a low positive (+) potential is applied to the pixel electrode (12) in comparison to the common voltage of the common electrode (13), a low electric field is applied to the blue particles (B) with a high negative (-) charge, thereby restricting their movement toward the pixel electrode (12). The white particles (W) with a high positive (+) charge are also restricted from moving toward the common electrode (13) for the same reason. This is because the low electric field is not strong enough to overcome the strong attractive force between the two particles. On the other hand, the low electric field is sufficient to separate the yellow particles (Y) with a low negative (-) charge and the red particles (R) with a low positive (+) charge, so the red particles (R) with a low positive (+) charge move toward the common electrode (13), and the yellow particles (Y) with a low negative (-) charge move toward the pixel electrode (12). Finally, to the user, it is displayed in red through external light reflection.

[0069] In addition, when a low negative (-) potential is applied to the pixel electrode (12) compared to the common voltage of the common electrode (13), a low electric field of opposite polarity is generated, and the particle distribution appears opposite to the previous one. Finally, it is displayed to the user in yellow through external light reflection.

[0070] FIG. 3 is a driving circuit of an electrophoretic display device according to one embodiment.

[0071] Referring to FIG. 3, the data driving unit (22) can be electrically connected to the source electrode of the TFT (14) through a data line.

[0072] The drain electrode of the TFT (14) can be electrically connected to the pixel electrode (12).

[0073] In various embodiments, the source electrode of the TFT (14) is electrically connected to the pixel electrode (12), and the drain electrode of the TFT (14) can be electrically connected to the data driver (22).

[0074] The gate electrode of the TFT (14) can be electrically connected to the gate driver (21).

[0075] The TFT (14) can be turned on or turned off by the gate voltage output from the gate driver (21).

[0076] When the TFT (14) is turned on, the data voltage having a waveform output from the data driving unit (22) can be supplied to the pixel electrode (12) through the TFT (14).

[0077] A common voltage can be supplied to the common electrode (12) in the form of a DC voltage or an AC voltage.

[0078] Accordingly, an electric field can be formed in the pixel (11) by the potential difference between the pixel electrode (12) and the common electrode (13).

[0079] In the pixel (11), the common electrode (13) and the source electrode of the TFT (14) can be formed as a capacitive load. In various embodiments, the capacitive load can be formed between the common electrode (13) and the pixel electrode (12).

[0080] By supplying a common voltage to the common electrode (13) and supplying a data voltage to the pixel electrode (12), a plurality of color pigments of the pixel (11) can be reproducibly aligned to a specific position or moved to an initial position. The data voltage can be switched at high speed (e.g., 85Hz) with positive (+) and negative (-) high voltages (e.g., +19V, -19V). Additionally, depending on the characteristics or environment of the pixel (11), it can be driven at high speed for as short as a few seconds (e.g., 15 seconds) to a few minutes.

[0081] FIG. 4 illustrates a reverse prevention unit of a power supply unit of an electrophoretic display device according to one embodiment.

[0082] Referring to FIG. 4, when the power of the electrophoretic display device (1) is turned on, the power supply unit (40) uses the input power (Vin) to generate voltages (VDDP, VDDN, VCOM, VPOS, VNEG, VNCP, VGH, VGL, etc.) required for driving the display panel (10) according to the power supply sequence, and supplies the voltages to the display panel (10), the gate driver (21), the data driver (22), etc. For example, the power supply unit (40) can supply gate voltages (VGH, VGL) to the gate driver (21). The power supply unit (40) can supply driving voltages (VDDP, VDDN, VPOS, VNEG, VNCP) required for driving the data driver (22) to the data driver (22).

[0083] The data driving unit (22) can generate a data voltage supplied to the pixel electrode (12) using driving voltages generated by the power supply unit (40). The data voltage can be repeated based on the common voltage of the common electrode (13) within the range of positive (+) voltage (e.g., +19V) and negative (-) voltage (e.g., -19V) to move the charged color pigment to the common electrode, and can have multiple voltage levels depending on the charge amount of the charged color pigments.

[0084] The power supply unit (40) can generate multiple driving voltages (VDDP, VDDN, VPOS, VNEG, VNCP) so that the data driving unit (22) generates a data voltage having multiple voltage levels.

[0085] To this end, the power supply unit (40) may include a plurality of power sources (50). The plurality of power sources (50) may include a first power source to the nth power source having different voltage levels. The first power source to the nth power source may be named the first power supply unit to the nth power supply unit.

[0086] The first power supply can output a first voltage (VDDP, for example, +19V).

[0087] The nth power supply can output the nth voltage (VDDN, e.g., -19V).

[0088] A plurality of power sources (50) may include multiple power sources that output a voltage of positive (+) polarity (VPOS, e.g., +10V, +7V, etc.), multiple power sources that output a voltage of negative (-) polarity (VNEG, e.g., -10V, -7V, etc.), and a power source that outputs a preset voltage (VNCP, e.g., -3.5V). FIG. 5 illustrates an inversion occurring between power sources in an electrophoretic display device according to one embodiment.

[0089] Referring to FIG. 5, the electrophoretic display device (1) is driven by a plurality of power sources (41). These plurality of power sources (41) are controlled according to a predetermined sequence.

[0090] When power is supplied, it is applied in order from the lowest voltage to the highest voltage according to the power supply sequence, and when power is cut off, it is cut off in order from the highest voltage to the lowest voltage according to the power cut-off sequence.

[0091] For example, depending on the characteristics of the loads connected to each power source, when the power is cut off at time t1, the VNCP power (-3.5V) may rise slowly to the ground potential (GND), whereas the VDDN power (-19V) may rise rapidly to the ground potential (GND). In other words, although the voltage should discharge quickly when a specific voltage is cut off, there are cases where it fails to reach the reference potential, the GND level. This is attributed to the difference in natural discharge time depending on the load characteristics. Due to this difference in voltage reduction time, a voltage inversion phenomenon occurs in the interval (T) from time t2 to time t3.

[0092] The power sources (50) are connected to the data driver (22). The data driver (22) is a semiconductor device, and depending on the circuit design, switching elements such as diodes may be placed between the supplied power sources (50). When the potential between the power sources (50) is reversed due to the charging and discharging time based on load characteristics while the supplied power sources (50) are rising and falling, they may be short-circuited through the diodes. If a current exceeding the design capacity occurs suddenly, the data driver (22) may be damaged.

[0093] Previously, to prevent this voltage reversal phenomenon, it was necessary to wait anywhere from a few seconds to several minutes until natural discharge was complete. From the consumer's perspective, this requires a very long waiting time and is a factor that degrades product performance.

[0094] Generally, depending on the characteristics of the data driving unit (22) and the characteristics of the power supply and connected load used, there is a difference in the voltage charging and discharging times, and as a result, a sufficient time interval is required between each voltage. For example, there is a driving voltage that takes a long time to completely discharge in the power cut-off sequence, and in order to prevent damage caused by reverse voltage, it is necessary to supply and cut off another power supply until it is completely discharged for tens of seconds, and since such a series of times is required, the screen switching time becomes long. In addition, if the input power is cut off due to a situation that is difficult for the control unit to predict, such as battery discharge, power outage, adapter disconnection, or power cable disconnection during screen display driving, the control of the power cut-off sequence becomes impossible, and damage caused by reverse voltage occurs.

[0095] Referring again to FIG. 4, the power supply unit (40) may include a reverse prevention unit (60) provided between a plurality of power sources (50).

[0096] The reverse prevention unit (60) can prevent voltage reversal between multiple power sources (50) when the power is cut off. The reverse prevention unit (60) may include an equivalent circuit provided between two power sources (50) where voltage reversal may occur due to load characteristics when power is supplied and cut off, which actively operates to short-circuit the two voltages to prevent reversal when voltage reversal occurs.

[0097] For example, the reverse protection unit (60) can be connected between the VNCP power supply (-3.5V) and the VDDN power supply (-19V). In addition, the reverse protection unit (60) can be provided between two power supplies of different voltage levels.

[0098] The reverse prevention unit (60) can prevent reverse even when an accidental input voltage is interrupted, such as when the battery is discharged, a power outage occurs, the adapter is disconnected, or the power cable is disconnected, during screen display operation.

[0099] The reverse prevention unit (60) can prevent reverse not only during normal operation but also when an accidental input voltage is cut off, and can significantly reduce the standby time caused by the charging and discharging times of multiple power sources.

[0100] Accordingly, the electrophoretic display device (1) according to one embodiment can implement a stable and reliable driving circuit by including a reverse prevention unit (60) and can implement an electrophoretic display capable of fast screen switching.

[0101] FIG. 6 illustrates an example of a reverse prevention unit of a power supply unit of an electrophoretic display device according to one embodiment.

[0102] Referring to FIG. 6, the reverse prevention unit (60) may include a diode, which is a passive circuit element. For example, the diode may include a Schottky barrier diode (SBD), a fast recovery diode, etc.

[0103] For example, the reverse prevention unit (60) may include a Schottky barrier diode (61).

[0104] A Schottky barrier diode (61) is a semiconductor diode formed through a junction of metal and semiconductor, and can achieve a low voltage drop and a fast switching speed. A Schottky barrier diode can have a relatively low voltage drop compared to a general diode. A Schottky barrier diode can reduce power loss and can operate effectively at switching frequencies of tens of kHz or higher.

[0105] A Schottky barrier diode (61) may be provided between the output terminal of the power supply that outputs the lower voltage and the output terminal of the power supply that outputs the higher voltage among the two power supplies. The anode of the Schottky barrier diode (61) may be connected to the power supply that outputs the lower voltage and the cathode may be connected to the power supply that outputs the higher voltage. For example, the anode of the Schottky barrier diode (61) may be connected to the VDDN power supply (-19V) and the cathode may be connected to the VNCP power supply (-3.5V).

[0106] The Schottky barrier diode (61) does not require a logic voltage for reverse prevention operation when the voltage reverses. Even when accidental input voltage is interrupted, such as when the battery is discharged, power is cut off, the adapter is disconnected, or the power cable is disconnected, the voltage can be effectively prevented without additional control, thereby preventing damage to the data driving unit (22). In addition, the diode is a passive circuit element and does not require a control signal, such as a logic voltage for switching when the voltage reverses.

[0107] The Schottky barrier diode (61) does not require logic and switches to control the reversal timing and can operate actively even in the event of an accidental power interruption. The same applies to the diode, which is a passive circuit element. In addition, since there is no need for the waiting time required for charging and discharging during the two power supply and cutoff, the screen transition time can be significantly reduced.

[0108] FIG. 7 illustrates the operation of a Schottky barrier diode in a reverse prevention unit of an electrophoretic display device according to one embodiment.

[0109] Referring to Figure 7, it is assumed that the VNCP power supply (-3.5V) takes a long time to discharge due to the load characteristics compared to the VDDN power supply (-19V) when the power is cut off.

[0110] The Schottky barrier diode (61) is a passive circuit element that allows current to flow in the forward direction when reverse voltage occurs, causing the two power sources to be short-circuited to each other.

[0111] More specifically, the Schottky barrier diode (61) can remain turned off during normal operation when the VDDN power supply (-19V) connected to the anode is lower than the VNCP power supply (-3.5V) connected to the cathode.

[0112] In this state, the power cutoff operation is initiated, and when the potential of the VDDN power supply (-19V) rises rapidly and reaches a point higher than the potential of the VNCP power supply (-3.5V), the Schottky barrier diode (61) is turned on and current flows. Through this, the two power supplies converge to the same level without voltage inversion.

[0113] FIG. 8 is a graph showing the characteristics of Schottky barrier diodes by material in the reverse prevention section of an electrophoretic display device according to one embodiment.

[0114] Referring to FIG. 8, the horizontal axis represents voltage (V) and indicates forward and reverse voltage characteristics. The vertical axis represents current (I).

[0115] Schottky barrier diodes (61) are developed using various materials, and depending on the material characteristics, the forward voltage Vf characteristics differ as shown in Fig. 8.

[0116] When using silicon (Si) material for the Schottky barrier diode (61), the turn-on voltage is generally higher than 0.7V. Even when turned on, the potential difference between the two terminals remains higher than 0.7V. As a result, even if the two power sources are short-circuited when reverse voltage occurs, a voltage of 0.7V or higher is maintained, which may cause damage depending on the internal design of the data driver (22). Generally, when using platinum (Pt) material for the Schottky barrier diode (61), a level of 0.6V to 0.7V can be secured, and when using molybdenum (Mo) material, a level of 0.55V can be secured. As a result, even if the two power sources are short-circuited when reverse voltage occurs, the voltage remains between 0.55V to less than 0.7V, which may cause damage depending on the internal design of the data driver (22).

[0117] However, when using titanium (Ti) material, the Schottky barrier diode (61) can secure a level lower than 0.3V. As a result, even if the two power sources are short-circuited when reverse voltage occurs, the voltage is maintained at 0.3V or lower, and the internal design of the data driver (22) can minimize and prevent damage.

[0118] FIG. 9 illustrates another example of a reverse prevention unit of a power supply unit of an electrophoretic display device according to one embodiment.

[0119] Referring to FIG. 9, the reverse prevention unit (60) may include an equivalent circuit (62) that simulates an ideal diode (IDEAL DIODE) in which the forward voltage Vf is 0.

[0120] An ideal diode equivalent circuit (62) includes a Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and a transistor as active elements and can be actively turned on without additional external control by detecting voltage reversal.

[0121] The ideal diode equivalent circuit (62) is an ideal active reverse prevention equivalent circuit because the voltage across the circuit terminals is assumed to be 0, or short circuit, compared to the Schottky barrier diode (61) shown in FIG. 7.

[0122] An ideal diode equivalent circuit (62) can be effective when there is a risk of damage to the driving circuit due to the voltage difference and the amount of charge to be discharged, or due to the forward voltage Vf of the diode, even though the complexity of the Schottky barrier diode (61) increases.

[0123] An ideal diode equivalent circuit (62) may include a first switching element (MOSFET) and a voltage comparison circuit (Q1, Q2, R1, R2), etc.

[0124] The drain (D) of the first switching element (MOSFET) is connected to Vin (e.g., -19V). The source (S) is connected to Vout (e.g., -3.5V). The gate (G) is connected to the VG node. An internal parasitic diode exists between the drain and the source.

[0125] The voltage comparison circuit (Q1, Q2, R1, R2) can turn on or turn off the first switching element (MOSFET) based on the difference between the voltage output from Vin (e.g., -19V) and the voltage output from Vout (e.g., -3.5V).

[0126] The voltage comparison circuit (Q1, Q2, R1, R2) may include a second switching element (Q1) and a third switching element (Q2).

[0127] The second switching element (Q1) and the third switching element (Q2) may be PNP transistors.

[0128] The emitter of the second switching element (Q1) is connected to Vin, and the collector is connected to the base connected to the VB node.

[0129] The emitter of the third switching element (Q2) is connected to Vout, and the collector is connected to the VG node, which is connected to the gate of the first switching element.

[0130] For example, the preset voltage (VGL) can be -22V or ground. R1 is connected between the VB node and VGL. R2 is connected between the VG node and VGL.

[0131] FIG. 10 illustrates the operation of an ideal diode equivalent circuit in a normal voltage state in a reverse prevention unit of an electrophoretic display device according to one embodiment.

[0132] Referring to Fig. 10, it is assumed that in the normal state, Vin outputs -19V and Vout outputs -3.5V.

[0133] The operation of an ideal diode equivalent circuit (62) in a normal state is explained.

[0134] The voltage (VB) of the VB node can be the value obtained by subtracting a preset voltage value from Vin. The preset voltage value can be -0.65V.

[0135] When the condition is Vout > Vin, VB < Vout - 0.65V (-19V - 0.65V < -3.5V - 0.65V), Q2 is turned on, the MOSFET is turned off as Vg > Vs, and the terminals of the MOSFET's parasitic diode remain in a reverse bias state.

[0136] FIG. 11 illustrates the operation of an ideal diode equivalent circuit in a reverse voltage state in a reverse prevention unit of an electrophoretic display device according to one embodiment.

[0137] Referring to Fig. 11, when Vin, which was -19V, rapidly rises to a voltage greater than VNCP (-3.5V) (e.g., -3V), the voltages at both ends are reversed.

[0138] When the condition Vout < Vin is met, VB > Vout - 0.65V (-3V - 0.65V > -3.5V - 0.65V), Q2 is turned off, current flows between the drain (D) and source (S) of the MOSFET, and the voltage across both ends converges to the same level.

[0139] FIG. 12 illustrates the results before and after the application of a reverse prevention unit to an electrophoretic display device according to one embodiment.

[0140] FIG. 12(a) shows the result of applying a reverse prevention unit (60) to an electrophoretic display device according to one embodiment, and FIG. 12(b) shows the result before the reverse prevention unit (60) is applied.

[0141] As shown in Fig. 12(b), when the power is cut off, the VNCP power (-3.5V) rises slowly to GND and the VDDN power (-19V) rises rapidly to GND, causing voltage inversion due to the difference in natural discharge time according to load characteristics.

[0142] However, as illustrated in FIG. 12(b), when the voltage is reversed, the reverse prevention unit (60) short-circuits the two power sources. Therefore, the moment the VDDN power becomes higher than the VNCP power, the two voltages are short-circuited and converge to the same potential, rising to GND. As a result, the electrophoretic display device (1) according to one embodiment can prevent voltage reversal when the power is cut off and eliminates the need for a waiting time until natural discharge, thereby significantly shortening the screen switching time. The electrophoretic display device (1) according to one embodiment comprises: a common electrode (12) to which a common voltage is supplied; a pixel electrode (13) arranged to correspond to the common electrode (12); a plurality of color pigments arranged between the common electrode (12) and the pixel electrode (13) and dispersed in a solvent; a data driving unit (22) that supplies a data voltage to the pixel electrode (13); and a power supply unit (40) including a plurality of power sources that supply a plurality of voltages to the data driving unit (22). It may include a reverse prevention unit (50) configured to prevent voltage reversal between the plurality of power sources when the power is cut off.

[0143] The above-mentioned reverse prevention unit (50) can short-circuit two of the plurality of power sources whose voltages have been reversed based on the occurrence of a voltage reversal between the plurality of power sources.

[0144] The above reverse prevention unit (50) may include a diode provided between two of the plurality of power sources.

[0145] The two power sources mentioned above include a first power source that outputs a first voltage and a second power source that outputs a second voltage higher than the first voltage, and the diode may have its anode connected to the first power source and its cathode connected to the second power source.

[0146] The above diode includes a Schottky barrier diode, and the material of the Schottky barrier diode (61) may be titanium.

[0147] The above reverse prevention unit (50) includes a plurality of reverse prevention units (50), and the plurality of reverse prevention units (50) may include a first reverse prevention unit provided between a first power source and a second power source among the plurality of power sources; and a second reverse prevention unit provided between a third power source and a fourth power source among the plurality of power sources.

[0148] The above reverse prevention unit (50) may include an ideal diode equivalent circuit (62) in which the forward voltage Vf is 0, provided between two of the plurality of power sources.

[0149] The above ideal diode equivalent circuit (62) may include: a first switching element in which a parasitic diode is connected between a drain connected to the first power source and a source connected to the second power source among the two power sources; and a voltage comparison circuit configured to turn on or turn off the first switching element based on the difference between a first voltage output from the first power source and a second voltage output from the second power source.

[0150] The above voltage comparison circuit can compare a first voltage output from the first power source and a second voltage output from the second power source, and turn on or turn off the first switching element according to the comparison result.

[0151] The above voltage comparison circuit includes a second switching element and a third switching element, and

[0152] The second switching element may have an emitter connected to the first power source, a collector connected to the base, and the base connected to the base of the second switching element, and the third switching element may have an emitter connected to the second power source, a collector connected to the gate of the first switching element, and a base connected to the base of the second switching element.

[0153] In a normal state, the first power supply outputs a voltage lower than the second power supply, and in response to the first power supply outputting a voltage lower than the second power supply, the third switching element can be turned on and the first switching element can be turned off.

[0154] In a voltage inversion state, the first power supply outputs a higher voltage than the second power supply, and in response to the first power supply outputting a higher voltage than the second power supply, the third switching element can be turned off and the first switching element can be turned on.

[0155] An electrophoretic display device (1) according to another embodiment may include: a power supply unit (40) that generates a first power source that outputs a first voltage and a second power source that outputs a second voltage higher than the first voltage; and a reverse prevention unit (50) configured to short-circuit the first power source and the second power source based on the occurrence of a reversal of the first voltage and the second voltage when the power is cut off.

[0156] The above reverse prevention unit (50) may include a diode.

[0157] The above diode may have its anode connected to the first power source and its cathode connected to the second power source.

[0158] The above diode includes a Schottky barrier diode, and the material of the Schottky barrier diode (61) may be titanium.

[0159] The above reverse prevention unit (50) may include an ideal diode equivalent circuit (62).

[0160] The above ideal diode equivalent circuit (62) comprises: a first switching element in which a parasitic diode is connected between a drain connected to the first power source and a source connected to the second power source; and

[0161] It may include a voltage comparison circuit configured to turn on or turn off the first switching element based on the difference between the first voltage and the second voltage.

[0162] The above voltage comparison circuit can compare the first voltage and the second voltage, and turn on or turn off the first switching element according to the comparison result.

[0163] The above voltage comparison circuit includes a second switching element and a third switching element, wherein the emitter of the second switching element is connected to the first power source, the collector is connected to the base, and the base is connected to the base of the second switching element, and the emitter of the third switching element is connected to the second power source, the collector is connected to the gate of the first switching element, and the base is connected to the base of the second switching element.

[0164] Meanwhile, the disclosed embodiments may be implemented in the form of a storage medium that stores instructions executable by a computer. The instructions may be stored in the form of program code, and when executed by a processor, they may generate a program module to perform the operation of the disclosed embodiments.

[0165] Computer-readable recording media include all types of recording media that store instructions that can be decoded by a computer. Examples include ROM (read-only memory), RAM (random access memory), magnetic tape, magnetic disk, flash memory, optical data storage devices, etc.

[0166] Additionally, computer-readable recording media may be provided in the form of non-transitory storage media. Here, 'non-transitory storage media' simply means that it is a tangible device and does not contain a signal (e.g., electromagnetic waves), and this term does not distinguish between cases where data is stored semi-permanently and cases where it is stored temporarily. For example, 'non-transitory storage media' may include a buffer in which data is stored temporarily.

[0167] According to one embodiment, the method according to the various embodiments disclosed herein may be provided by being included in a computer program product. The computer program product may be traded between a seller and a buyer as a product. The computer program product may be distributed in the form of a device-readable storage medium (e.g., compact disc read-only memory (CD-ROM)), or distributed online (e.g., download or upload) through an application store (e.g., Play Store™) or directly between two user devices (e.g., smartphones). In the case of online distribution, at least a portion of the computer program product (e.g., downloadable app) may be temporarily stored or temporarily created on a device-readable storage medium, such as the memory of a manufacturer's server, an application store's server, or a relay server.

[0168] As described above, the disclosed embodiments have been explained with reference to the attached drawings. Those skilled in the art will understand that the present invention may be practiced in forms different from the disclosed embodiments without changing the technical spirit or essential features of the invention. The disclosed embodiments are illustrative and should not be interpreted restrictively.

Claims

1. A common electrode to which a common voltage is supplied; A pixel electrode positioned to correspond to the above common electrode; A plurality of color pigments disposed between the common electrode and the pixel electrode and dispersed in a solvent; A data driving unit that supplies a data voltage to the pixel electrode; A power supply unit comprising a plurality of power sources that supply a plurality of voltages to the above data driving unit; and An electrophoretic display device comprising: a reverse prevention unit configured to prevent voltage reversal between the plurality of power sources when the power is cut off.

2. In Paragraph 1, The above-mentioned reverse prevention unit is, An electrophoretic display device that short-circuits two of the plurality of power sources whose voltages have been reversed based on the occurrence of a voltage reversal between the plurality of power sources.

3. In Paragraph 1, The above-mentioned reverse prevention unit is, An electrophoretic display device comprising a diode provided between two of the plurality of power sources.

4. In Paragraph 3, The two power sources mentioned above are, It includes a first power source that outputs a first voltage and a second power source that outputs a second voltage higher than the first voltage, The above diode is, An electrophoretic display device in which an anode is connected to the first power source and a cathode is connected to the second power source.

5. In Paragraph 3, The above diode includes a Schottky barrier diode, and Electrophoretic display device in which the material of the above Schottky barrier diode is titanium.

6. In Paragraph 1, The above-mentioned reverse prevention unit includes a plurality of reverse prevention units, and The above plurality of reverse prevention units are, A first reverse prevention unit provided between a first power source and a second power source among the plurality of power sources; and An electrophoretic display device comprising a second reverse prevention unit provided between the third power source and the fourth power source among the plurality of power sources.

7. In Paragraph 1, The above-mentioned reverse prevention unit is, An electrophoretic display device comprising an ideal diode equivalent circuit having a forward voltage Vf of 0, arranged between two of the plurality of power sources.

8. In Paragraph 7, The above ideal diode equivalent circuit is, A first switching element having a parasitic diode connected between a drain connected to the first power source and a source connected to the second power source among the two power sources; and An electrophoretic display device comprising a voltage comparison circuit configured to turn on or turn off a first switching element based on the difference between a first voltage output from the first power source and a second voltage output from the second power source.

9. In Paragraph 8, The above voltage comparison circuit is, An electrophoretic display device that compares a first voltage output from the first power source and a second voltage output from the second power source, and turns on or turns off the first switching element according to the comparison result.

10. In Paragraph 8, The above voltage comparison circuit is, It includes a second switching element and a third switching element, and The above second switching element is, The emitter is connected to the first power source, the collector is connected to the base, and the base is connected to the base of the second switching element. The above third switching element is, An electrophoretic display device in which the emitter is connected to the second power source, the collector is connected to the gate of the first switching element, and the base is connected to the base of the second switching element.

11. In Paragraph 10, In a normal state, the first power source outputs a voltage lower than the second power source, and An electrophoretic display device in which the third switching element is turned on and the first switching element is turned off in response to the first power source outputting a voltage lower than the second power source.

12. In Paragraph 10, In a voltage reversal state, the first power source outputs a higher voltage than the second power source, and An electrophoretic display device in which, in response to the first power source outputting a voltage higher than the second power source, the third switching element is turned off and the first switching element is turned on.

13. In an electrophoretic display device, A power supply unit that generates a first power source outputting a first voltage and a second power source outputting a second voltage higher than the first voltage; and An electrophoretic display device comprising: a reverse prevention unit provided between the first power source and the second power source and configured to short-circuit the first power source and the second power source based on the occurrence of a reversal of the first voltage and the second voltage when the power is cut off.

14. In Paragraph 13, The above-mentioned reverse prevention unit is, Electrophoretic display device including a diode.

15. In Paragraph 14, The above diode is, An electrophoretic display device in which an anode is connected to the first power source and a cathode is connected to the second power source.

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