Display device and driving method therefor

Abstract

A display device according to an embodiment may comprise: a display module including a display panel; and a power board, which measures an operating frequency of output DC voltage input into the display panel, controls, on the basis of the measured operating frequency, that PFC voltage is changed, and varies the output DC voltage on the basis of the changed PFC voltage and supplies same to the display panel.

Description

Display device and driving method thereof

[0001] The embodiment relates to a display device that controls an output voltage based on a PFC voltage and a driving method thereof.

[0002] Recently, the types of display devices have become more diverse. Among them, Organic Light Emitting Diode Displays (hereinafter referred to as OLED displays) are widely used.

[0003] Since OLED displays are self-emissive devices, they have the advantage of lower power consumption and the ability to be manufactured thinly compared to liquid crystal displays that require a backlight. In addition, OLED displays offer the advantages of a wide viewing angle and fast response speed.

[0004] OLED display devices utilize an LLC topology capable of zero-voltage switching operation to achieve high power density when supplying power. In other words, OLED display devices can supply power using a DC-DC converter that includes an LLC resonant circuit.

[0005] Conventional OLED display devices utilize Dynamic Power Control (DPC) to lower the output voltage, contributing to efficiency ratings and heat dissipation; however, as the DPC voltage variation range increases, there is a problem in that frequency control under no-load conditions becomes difficult.

[0006] To solve the above problem, the embodiment aims to provide a display device and a driving method thereof for effectively limiting the rise in operating frequency regardless of the DPC mode.

[0007] To achieve the above objective, a display device according to an embodiment may include a display module including a display panel; and a power board that measures the operating frequency of an output DC voltage input to the display panel, controls the change of a PFC voltage based on the measured operating frequency, and varies the output DC voltage based on the changed PFC voltage and supplies it to the display panel.

[0008] When the above operating frequency reaches the reference frequency range, the PFC voltage can be changed from the first voltage to a second voltage lower than the first voltage.

[0009] The minimum value of the second voltage mentioned above may be greater than 1.4 times the input voltage.

[0010] The device further includes a control board that provides HDR mode or SDR mode information, and the power board can control the change of the PFC voltage based on the HDR mode or SDR mode information.

[0011] The power board measures the operating frequency in SDR mode, and if the operating frequency is greater than or equal to the reference frequency, it can vary the PFC voltage.

[0012] The above power board can control the output DC voltage to be raised or lowered in steps.

[0013] If the above operating frequency is less than the above reference frequency, the PFC voltage can be controlled to be maintained.

[0014] In addition, to achieve the above objective, a driving method for a display device according to an embodiment may include the steps of: measuring the operating frequency of an output DC voltage input to a display panel; controlling the PFC voltage to change based on the measured operating frequency; and varying the output DC voltage based on the changed PFC voltage and supplying it to the display panel.

[0015] If the above operating frequency corresponds to the reference frequency range, the PFC voltage can be changed from the first voltage to a second voltage lower than the first voltage.

[0016] The minimum value of the second voltage mentioned above may be greater than 1.4 times the input voltage.

[0017] It is possible to receive HDR mode or SDR mode information and control the PFC voltage to change based on the HDR mode or SDR mode information.

[0018] In the above SDR mode, the operating frequency is measured, and if the operating frequency is greater than or equal to the reference frequency, the PFC voltage can be varied.

[0019] The above output DC voltage can be controlled to be raised or lowered in steps.

[0020] If the above operating frequency is less than the above reference frequency, the PFC voltage can be controlled to be maintained.

[0021] The embodiment has the effect of improving OLED power consumption in response to various inputs by controlling the PFC output voltage using the operating frequency of the EVDD voltage.

[0022] In addition, the embodiment can reduce EMI effects by implementing it so that it cannot operate above a certain frequency.

[0023] FIG. 1 is a block diagram showing a display device according to a first embodiment.

[0024] Figure 2 is a block diagram showing an example of a display module illustrated in Figure 1.

[0025] FIG. 3 is a diagram showing the layout structure of a display panel according to a first embodiment.

[0026] FIG. 4 is a diagram showing the structure of a unit pixel according to the first embodiment.

[0027] FIG. 5 is a block diagram showing a power board according to a first embodiment.

[0028] FIG. 6 is a flowchart illustrating a method of driving a display device according to a first embodiment.

[0029] FIG. 7 is a graph showing the variation of the PFC voltage according to the first embodiment.

[0030] FIG. 8 is a block diagram showing a display device according to a second embodiment.

[0031] FIG. 9 is a flowchart illustrating a driving method of a display device according to a second embodiment.

[0032] FIG. 10 is a graph showing the variation of the PFC voltage according to the second embodiment.

[0033] Figure 11 is a graph showing the gain margin analysis of an LLC circuit.

[0034] Hereinafter, embodiments will be described in detail with reference to the attached drawings. Since embodiments may be subject to various modifications and may take various forms, specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the embodiments to the specific disclosed forms, and it should be understood that they include all modifications, equivalents, and substitutions that fall within the spirit and scope of the embodiments.

[0035] Terms such as "first," "second," etc., may be used to describe various components, but said components should not be limited by said terms. These terms are used for the purpose of distinguishing one component from another. Furthermore, terms specifically defined in consideration of the configuration and operation of the embodiments are intended only to describe the embodiments and do not limit the scope of the embodiments.

[0036] In the description of the embodiments, where it is stated that an element is formed "on or under," the terms "on or under" include both cases where two elements are in direct contact with each other and cases where one or more other elements are placed between the two elements to form the element indirectly. Furthermore, when expressed as "on or under," the meaning may include not only the upward direction but also the downward direction relative to a single element.

[0037] Additionally, relational terms such as "upper / upper / above" and "lower / lower / below" used below may be used to distinguish one entity or element from another, without necessarily requiring or implying any physical or logical relationship or order between such entities or elements.

[0038] FIG. 1 is a block diagram showing a display device according to a first embodiment.

[0039] Referring to FIG. 1, a display device (100) according to the first embodiment may include a control board (120), a power board (130), and a display module (110).

[0040] The control board (120) may be referred to as a control unit, controller, processor, CPU, etc. The power board (130) may be referred to as a power supply unit, power supply unit, power management unit, power controller, etc. The display module (110) may be referred to as a display, display unit, display block, display section, image display device, image device, etc.

[0041] The control board (120) is responsible for the overall management and control of the display device (100). For example, the control board (120) can control the display module (110) to display an image, control the power board (130) to stably supply a DC voltage (EVDD) to the display module (110), and control the display device (100) to obtain status information of the display device (100) based on various detection signals received from the display device (100) and to take measures corresponding to the status information.

[0042] The control board (120) generates a power control signal considering the load information of the display panel (118), transmits the generated power control signal to the power board (130), and the power board (130) can generate an output voltage (EVDD) based on the transmitted power control signal and supply it to the display module (110).

[0043] The load of the display panel (118) may refer to the amount of energy consumed by the display panel (118) and may be determined by the driving current used to display an image on the display panel (118). For example, if the display panel (118) requires a large driving current, the load may be large, and if the display panel (118) requires a small driving current, the load may be small.

[0044] For example, if most of the multiple pixels of the display panel (118) display a white-graded image, a maximum driving current is required for each pixel to display such a white-graded image, so the sum of the driving currents required for most of the pixels of the display panel (118) is large, which means the load is large. Conversely, if most of the multiple pixels of the display panel (118) display a black-graded image, a minimum driving current, such as 0mA or a current value close to it, is required for each pixel to display such a black-graded image, so the sum of the driving currents required for most of the pixels of the display panel (118) is small, which means the load is small. Although it has been explained above that the load is large when displaying a white-graded image and the load is small when displaying a black-graded image, the opposite is also possible.

[0045] Figure 2 is a block diagram showing an example of a display module illustrated in Figure 1.

[0046] Referring to FIG. 2, the display module (110) may include a timing controller (112), a gate driver (114), a data driver (116), and a display panel (118). If the display panel (118) is a liquid crystal display (LCD) panel, the display module (110) may further include a backlight unit (not shown).

[0047] The display panel (118) may include a plurality of pixels that display an image or video based on a driving current. The display panel (118) may be a liquid crystal display panel or an organic light-emitting diode (OLED) display panel.

[0048] The timing controller (112) can control the gate driver (114) and the data driver (116). That is, the timing controller (112) can output a gate control signal for controlling the gate driver (114) and a data control signal for controlling the data driver (116).

[0049] The gate driver (114) can supply a gate signal, such as a scan signal, to the display panel (118) in response to a gate control signal. The display panel (118) can activate pixels according to the scan signal. Activating a pixel may mean that an image signal is supplied to the corresponding pixel. If each pixel includes at least one switch, activating a pixel may mean that the corresponding switching element is turned on by the scan signal.

[0050] The data driver (116) can supply video signals to the display panel (118) in frames according to the data control signal.

[0051] Each of the multiple pixels included in the display panel (118) can output an image by operating based on a data signal provided by a data driver (116) and a gate signal provided by a gate driver (114). If the display panel (118) is an LCD panel, light emitted from a backlight unit (not shown) can pass through the color filter of each pixel to output an image. If the display panel (118) is an OLED panel, light emitted directly from each pixel can output an image.

[0052] The display panel (118) may include one or more sensing units (119), and the sensing unit (119) may detect a driving current flowing through a pixel of the display panel (118). For example, the sensing unit (119) may be connected to the data lines (R1, G1, B1, W1 ~ Rm, Gm, Bm, Wm) shown in FIG. 3. The sensing unit (119) may detect the load of the display panel (118) and transmit load information to the control board (120). For example, the sensing unit (119) may detect the state of the load by measuring the driving current flowing on the data lines (R1, G1, B1, W1 ~ Rm, Gm, Bm, Wm). Alternatively, the control board (120) may generate load information based on output image data.

[0053] FIG. 3 is a diagram showing the layout structure of a display panel according to a first embodiment.

[0054] Referring to FIG. 3, the display panel (118) may include a plurality of pixels. And, a plurality of subpixels (SPr1, SPg1, SPb1, SPw1) may form a group pixel. Each subpixel (SPr1, SPg1, SPb1, SPw1) may include an organic light-emitting element or a color filter capable of implementing different colors.

[0055] FIG. 4 is a diagram showing the structure of a unit pixel according to the first embodiment.

[0056] Referring to FIG. 4, each pixel (CRTm) may include a scan switching element (SW1), a storage capacitor (Cst), a driving switching element (SW2), and an organic light-emitting diode (OLED).

[0057] A scan switching element (SW1) has a scan line connected to its gate terminal and can be turned on according to a scan signal (Vscan) input from a gate driver (114). When the scan switching element (SW1) is turned on, an image signal (Vdata) input from a data driver (116) is transmitted to the gate terminal of a driving switching element (SW2) or to one end of a storage capacitor (Cst).

[0058] A storage capacitor (Cst) is formed between the gate terminal and the source terminal of a driving switching element (SW2) and stores a predetermined difference between the level of a video signal delivered to one end of the storage capacitor (Cst) and the level of a DC power supply (Vdd) delivered to the other end of the storage capacitor (Cst). For example, if the video signal has different levels according to the PAM (Pulse Amplitude Modulation) method, the power level stored in the storage capacitor (Cst) changes depending on the level difference of the video signal (Vdata).

[0059] As another example, when the video signal has different pulse widths according to the PWM (Pulse Width Modulation) method, the power level stored in the storage capacitor (Cst) varies depending on the difference in the pulse width of the video signal (Vdata).

[0060] The driving switching element (SW2) is turned on according to the power level stored in the storage capacitor (Cst). When the driving switching element (SW2) is turned on, a driving current (IOLED) proportional to the stored power level flows to the organic light-emitting diode (OLED). Accordingly, the organic light-emitting diode (OLED) can emit light.

[0061] An organic light-emitting diode (OLED) includes an RGBW light-emitting layer (EML) corresponding to a subpixel, and may include at least one of a hole injection layer (HIL), a hole transport layer (HTL), an electron transport layer (ETL), and an electron injection layer (EIL), and may also include a hole blocking layer, etc.

[0062] Each subpixel outputs white light from an organic light-emitting diode (OLED) and may include a separate color filter for color implementation. For green, red, and blue subpixels (SPr1, SPg1, SPb1), a separate color filter may be provided for color implementation. On the other hand, for the white subpixel (SPw1), since it outputs white light, a separate color filter may not be provided.

[0063] Meanwhile, in FIG. 4, the scan switching element (SW1) and the driving switching element (SW2) are exemplified as p-type MOSFETs, but they may be n-type MOSFETs, or other switching elements such as JFETs, IGBTs, or SICs may be used.

[0064] FIG. 5 is a block diagram showing a power board according to a first embodiment.

[0065] Referring to FIG. 5, the power board (130) may include a PFC circuit (131), a switching unit (132), an LLC resonant circuit (133), a transformer (134), a rectifier circuit (135), and a power controller (136).

[0066] The PFC circuit (131) is a Power Factor Correction Circuit and may refer to a circuit that improves the power factor of an input power supply (or input voltage) and outputs it. The switching unit (132) includes at least one switch (e.g., two) and can supply voltage to the LLC resonant circuit (133) through switching operation under the control of the power controller (136). The LLC resonant circuit (133), transformer (134), and rectifier circuit (135) can generate an output DC voltage (EVDD). The LLC circuit (133) may also be referred to as a resonant tank.

[0067] The power controller (136) can control the switching unit (132) through a switch control signal, and the switch control signal may include a first output (or Ho output) that controls a first switch included in the switching unit (132) and a second output (or Lo output) that controls a second switch included in the switching unit (32).

[0068] The power controller (136) can receive the operating frequency of the output DC voltage (EVDD) as feedback and receive load information from the control board (120). Then, the power controller (136) can control the operation of the PFC circuit (131) or the switching unit (132) by considering the received load information or the operating frequency of the output DC voltage (EVDD). For example, the power controller (136) can control the operation of at least one switch included in the switching unit (132) by generating a switch control signal and transmitting the generated switch control signal to the switching unit (132). For example, the power controller (136) can adjust the output voltage of the PFC circuit (131).

[0069] FIG. 6 is a flowchart illustrating a method of driving a display device according to a first embodiment.

[0070] Referring to FIG. 6, the power controller can measure the operating frequency of the EVDD (S100).

[0071] The power controller can change the PFC voltage when the operating frequency of the measured EVDD voltage reaches a reference frequency (S200). The power controller can change the PFC voltage to a lower voltage. The reference frequency may include, but is not limited to, 140KHz to 150KHz.

[0072] The power controller can vary the EVDD voltage based on the changed PFC voltage and supply it to the display panel (S300).

[0073] FIG. 7 is a graph showing the variation of the PFC voltage according to the first embodiment.

[0074] Referring to FIG. 7, the PFC voltage can be maintained at time points t0-t1 and t1-t2. At time point t2-t3, when the no-load state is reached and the operating frequency of the EVDD voltage reaches 140 kHz, the PFC voltage can be changed from the first voltage to the second voltage. The second voltage may be a voltage lower than the first voltage. The second voltage may be a voltage greater than 1.4 times the input voltage.

[0075] As described above, the embodiment can be implemented so that it is easy to respond to feedback (F / B) operation for linear conversion of the output and cannot operate at frequencies, for example, 150 kHz or higher, which can have EMI EC effects as in the conventional method.

[0076] In addition, conventionally, the PFC input voltage is lowered only at a specific AC input voltage, so there is a problem in that it is difficult to respond to the input voltage range of 90 to 260 Vac.

[0077] The embodiment enables the advantage of improved OLED power consumption by variably changing the output voltage at which the PFC circuit can operate normally according to the EVDD operating frequency, thereby supporting a wide input regardless of efficiency, frequency, brightness control, and region.

[0078] FIG. 8 is a block diagram showing a display device according to a second embodiment.

[0079] Referring to FIG. 8, a display device according to the second embodiment may include a control board (120), a power board (130), and a display module (110).

[0080] The control board (120) can provide HDR mode information for reducing power consumption. The HDR mode may mean a mode that reduces power consumption in the display panel (118) by intermittently switching the switching unit (132).

[0081] The control mode (120) can provide on / off information for the HDR mode. When HDR is turned off, it can operate in SDR mode.

[0082] In the ON state of HDR mode, the OFF mode voltage can be maintained, and in SDR mode, the OFF voltage can be controlled linearly. For example, the voltage can be controlled between 0V and 5V.

[0083] The power board (120) can be linearly controlled using the pulse width of the control signal provided by the control board (120).

[0084] The control mode (120) can generate a power control signal by considering load information and HDR mode information, and transmit the generated power control signal to the power board (120). The power board (120) can generate an output voltage (EVDD) based on the transmitted power control signal and supply it to the display module (110).

[0085] That is, in the embodiment, the on / off of the HDR mode can be changed without using the DPC mode.

[0086] Although it was stated above that HDR mode is provided, it can also be configured to provide SDR mode.

[0087] FIG. 9 is a flowchart illustrating a driving method of a display device according to a second embodiment.

[0088] The driving method of the display device according to the second embodiment may be an operation performed in SDR mode. The SDR mode may include Eco, Vivid, Movie, and Standard modes.

[0089] Referring to FIG. 9, it can be checked whether the power is on (S400). Then, it can be determined whether a power-on signal has been generated (S410). If a power-on signal is confirmed, it can be checked whether the PFC circuit is operating (S420).

[0090] When it is confirmed that the PFC circuit is in a normal state, it can be determined whether a driver-on signal has been generated (S430).

[0091] Next, the start operation of the EVDD circuit can be checked (S450). Next, the feedback signal of the EVDD voltage can be detected (S460).

[0092] Next, the operating frequency of the EVDD voltage can be checked (S470). If the operating frequency of the EVDD voltage is greater than or equal to the reference frequency, the PFC feedback voltage can be linearly varied (S480).

[0093] Alternatively, if the operating frequency of the EVDD voltage is less than the reference frequency, the PFC feedback voltage can be set to a normal state (S490).

[0094] As described above, the change in PFC feedback voltage can be verified (S500).

[0095] FIG. 10 is a graph showing the variation of the PFC voltage according to the second embodiment.

[0096] Referring to Figure 10, when the operating frequency reaches the reference frequency of 140KHz at time t4-t5, the EVDD load increases.

[0097] The PFC voltage is varied to increase, and the operating frequency decreases at time t5-t6. When the operating frequency decreases, the PFC voltage is maintained in a steady state.

[0098] When the operating frequency starts to rise and reaches the reference frequency at time t6-t7, the PFC voltage can be varied to decrease.

[0099] In other words, the PFC voltage can be varied depending on whether the operating frequency reaches the reference frequency.

[0100] Figure 11 is a graph showing the gain margin analysis of an LLC circuit.

[0101] As shown in FIGS. 11a and 11b, it can be observed that the leakage inductance decreases under no-load conditions and the frequency tends to increase due to the influence of the secondary parasitic capacitor. It can be seen that the trend of increasing frequency rises according to the no-load characteristic curve.

[0102] Although the foregoing has been described with reference to the drawings and embodiments, those skilled in the art will understand that the embodiments can be modified and changed in various ways without departing from the technical spirit of the embodiments described in the following claims.

Claims

1. A display module including a display panel; and A power board that measures the operating frequency of an output DC voltage input to the display panel, controls the change of the PFC voltage based on the measured operating frequency, and varies the output DC voltage based on the changed PFC voltage and supplies it to the display panel; A display device including 2. In Paragraph 1, The above power board is, A display device that changes the PFC voltage from a first voltage to a second voltage lower than the first voltage when the above operating frequency corresponds to a reference frequency range.

3. In Paragraph 2, A display device in which the minimum value of the second voltage is greater than 1.4 times the value of the input voltage.

4. In Paragraph 1, It further includes a control board that provides HDR mode or SDR mode information, and The above power board is a display device that controls the change of the PFC voltage based on the HDR mode or SDR mode information.

5. In Paragraph 4, The above power board is a display device that measures the operating frequency in SDR mode and varies the PFC voltage if the operating frequency is greater than or equal to a reference frequency.

6. In Paragraph 5, The above power board is a display device that controls the output DC voltage to be raised or lowered in steps.

7. In Paragraph 5, A display device that controls the PFC voltage to be maintained when the above operating frequency is less than the above reference frequency.

8. A step of measuring the operating frequency of the output DC voltage input to the display panel; A step of controlling to change the PFC voltage based on the above-mentioned measured operating frequency; and A method for driving a display device comprising the step of varying the output DC voltage based on the above-mentioned changed PFC voltage and supplying it to the display panel.

9. In Paragraph 8, A driving method for a display device that changes the PFC voltage from a first voltage to a second voltage lower than the first voltage when the above operating frequency corresponds to a reference frequency range.

10. In Paragraph 9, A driving method for a display device in which the minimum value of the second voltage is greater than 1.4 times the value of the input voltage.

11. In Paragraph 8 A driving method for a display device that receives HDR mode or SDR mode information and controls the PFC voltage to change based on the HDR mode or SDR mode information.

12. In Paragraph 11, A driving method for a display device that measures the operating frequency in the above SDR mode and varies the PFC voltage if the operating frequency is greater than or equal to a reference frequency.

13. In Paragraph 12, A driving method for a display device that controls the output DC voltage to be raised or lowered in steps.

14. In Paragraph 12, A driving method for a display device that controls the PFC voltage to be maintained when the above operating frequency is less than the above reference frequency.

Images