Control device and liquid crystal display device

Abstract

To provide a control device and a liquid crystal display device capable of quickly increasing luminance of light emitted by a backlight when a bright image is inputted after a dark image is inputted.SOLUTION: A control device controls a backlight provided in a display device, and includes an acquisition portion for acquiring input luminance from an image signal, and a control portion that performs first control for setting output luminance of light emitted from the backlight to the input luminance, performs second control for setting the output luminance to a second threshold or less that is smaller than the first threshold when a state in which the output luminance is equal to or more than the first threshold for a set time or longer continues, and ends the second control in the middle and performs the first control when the input luminance becomes the second threshold or less during the second control.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a control device and a liquid crystal display device. [Background technology]

[0002] Patent Document 1 discloses a control device. In this control device, when the duty ratio of the LED is equal to or greater than a threshold for a certain period of time, a backlight drive control unit reduces the power supplied to the backlight. Also, when the duty ratio of the LED is less than another threshold for another certain period of time, the backlight drive control unit increases the power supplied to the backlight. (

[0016] and

[0039] ) [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 047973 Summary of the Invention [Problem to be solved by the invention]

[0004] In the control device disclosed in Patent Document 1, in order to increase the power supplied to the backlight after decreasing it, it is necessary to wait until a certain time has elapsed since the LED duty ratio fell below another threshold. Therefore, even if a bright image is input after a dark image is input, the power supplied to the backlight cannot be increased in a short time. Therefore, even if a bright image is input after a dark image is input, the brightness of the light emitted by the backlight cannot be increased in a short time. This results in a decrease in the display quality of the liquid crystal display device.

[0005] The present disclosure has been made in view of this problem, and an object of one aspect of the present disclosure is to provide a control device and a liquid crystal display device that can increase the luminance of light emitted by a backlight in a short period of time when, for example, a dark image is input and then a bright image is input. [Means for solving the problem]

[0006] A control device of one embodiment of the present disclosure is a control device that controls a backlight provided in a display device, and includes: an acquisition unit that acquires input luminance from a video signal; and a control unit that performs first control to set the output luminance of light emitted by the backlight to the input luminance, and if the output luminance remains above a first threshold for a set time or longer, performs second control to set the output luminance to a second threshold or less that is smaller than the first threshold, and if the input luminance becomes below the second threshold while performing the second control, terminates the second control and performs the first control.

[0007] A liquid crystal display device according to another aspect of the present disclosure includes the control device according to the aspect of the present disclosure, the backlight, and a liquid crystal panel that transmits the light. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a block diagram of a liquid crystal display device according to a first embodiment. [Figure 2] FIG. 2 is a plan view schematically illustrating a backlight provided in the liquid crystal display device of the first embodiment. [Figure 3] FIG. 2 is a plan view schematically illustrating a liquid crystal panel provided in the liquid crystal display device of the first embodiment. [Figure 4] 10 is a graph showing an example of temporal changes in input luminance and output luminance in the first reference example. [Figure 5] 10A and 10B are diagrams showing examples of images in which the input luminance is the maximum luminance Lmax in the first reference example, the second reference example, and the first embodiment. [Figure 6]10A and 10B are diagrams showing examples of images in which the input luminance is luminance L in the first reference example, the second reference example, and the first embodiment. [Figure 7] 10 is a graph showing an example of temporal changes in input luminance and output luminance in a second reference example. [Figure 8] 4 is a graph showing an example of temporal changes in input luminance and output luminance in the first embodiment. [Figure 9] 5 is a flowchart showing the flow of processing performed by a control unit provided in the liquid crystal display device of the first embodiment. [Figure 10] 10 is a graph showing an example of temporal changes in input luminance and output luminance in a modified example of the first embodiment. [Figure 11] FIG. 10 is a block diagram of a liquid crystal display device according to a second embodiment and a third embodiment. [Figure 12] 10 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is 35° C. or higher in the second embodiment. [Figure 13] 10 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is lower than 35° C. in the second embodiment. [Figure 14] 11 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is 35° C. or higher in the third embodiment. [Figure 15] 11 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is lower than 35° C. in the third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, the same or equivalent elements are designated by the same reference numerals, and redundant description will be omitted.

[0010] 1. First embodiment 1.1 Liquid crystal display device FIG. 1 is a block diagram of a liquid crystal display device according to the first embodiment.

[0011] The liquid crystal display device 1 of the first embodiment shown in FIG. 1 is a television receiver. Therefore, the liquid crystal display device 1 is electrically connected to an antenna 11. The antenna 11 receives broadcast waves 21 and outputs a reception signal 22 corresponding to the received broadcast waves 21. The liquid crystal display device 1 displays an image corresponding to the output reception signal 22. The liquid crystal display device 1 may have a built-in antenna 11. The liquid crystal display device 1 may be electrically connected to an external device that outputs a video signal and display an image corresponding to the output video signal. The connected external device may be a tuner, a recorder, a game console, a personal computer, or the like. The liquid crystal display device 1 may not have the function of displaying an image corresponding to the reception signal 22 output by the antenna 11, but may be a display that exclusively functions in response to the video signal output by the external device.

[0012] 1, the liquid crystal display device 1 includes a tuner 31, an acquisition unit 32, a control unit 33, a backlight 34, a drive unit 35, and a liquid crystal panel 36. The acquisition unit 32 and the control unit 33 configure a control device 41 that controls the backlight 34. The control device 41 may be provided in a display device other than the liquid crystal display device 1 and may control the backlight provided in that display device.

[0013] The tuner 31 extracts a video signal 23 from the received signal 22. The extracted video signal 23 indicates the video content. The tuner 31 includes electronic circuits for performing processing. The tuner 31 may include a processor for executing a program, and the processor may perform all or part of the processing.

[0014] The acquisition unit 32 acquires the input luminance 24 and the light transmittance 25 from the extracted video signal 23. The acquisition unit 32 includes an electronic circuit for carrying out the processing. The acquisition unit 32 may include a processor for executing a program, and the processor may be responsible for all or part of the processing.

[0015] The control unit 33 supplies power 26 to the backlight 34 to cause the backlight 34 to emit light 51. The control unit 33 performs pulse width modulation (PWM) on the power 26 supplied to the backlight 34. The control unit 33 changes the output luminance 28 of the emitted light 51 by changing the duty ratio 27 of the power 26. The duty ratio 27 is the ratio of the power-on time to the length of one pulse cycle. The control unit 33 also monitors the output luminance 28 by monitoring the duty ratio 27. The control unit 33 may change and monitor the output luminance 28 using other methods. The control unit 33 controls the output luminance 28 based on the acquired input luminance 24 and the monitored duty ratio 27. The control unit 33 includes an electronic circuit that performs processing. The control unit 33 may include a processor that executes a program, and the processor may perform all or part of the processing.

[0016] The backlight 34 emits light 51 according to the supplied power 26 .

[0017] The driving unit 35 supplies a voltage 29 to the liquid crystal panel 36 to set the light transmittance of the liquid crystal panel 36 to a light transmittance corresponding to the supplied voltage 29. The driving unit 35 changes the light transmittance of the liquid crystal panel 36 by changing the voltage 29 it supplies. The driving unit 35 controls the light transmittance of the liquid crystal panel 36 based on the acquired light transmittance 25. The driving unit 35 includes an electronic circuit that performs processing. The driving unit 35 may include a processor that executes a program, and the processor may perform all or part of the processing.

[0018] The liquid crystal panel 36 transmits the emitted light 51 to generate image light 52. The liquid crystal panel 36 has a light transmittance that corresponds to the supplied voltage 29. Therefore, the liquid crystal panel 36 modulates the light 51 based on the voltage 29 to generate image light 52. The image light 52 depicts an image having the content indicated by the extracted video signal 23.

[0019] 1.2 Backlight FIG. 2 is a plan view schematically illustrating a backlight provided in the liquid crystal display device of the first embodiment.

[0020] As shown in FIG. 2, the backlight 34 includes a plurality of units 61 .

[0021] The multiple units 61 are arranged in a matrix in a row direction D1 and a column direction D2.

[0022] The power 26 supplied to the backlight 34 includes power supplied to each of the multiple units 61. The light 51 emitted by the backlight 34 includes light emitted by each of the units 61. Each unit 61 emits light having an output brightness corresponding to the power supplied thereto. Therefore, each unit 61 emits light having an output brightness corresponding to the duty ratio of the power supplied thereto. Therefore, the control unit 33 changes the output brightness of the light emitted by each unit 61 by changing the duty ratio of the power supplied to each unit 61.

[0023] Each unit 61 includes a plurality of light-emitting diodes (LEDs). The LEDs are arranged in a matrix in a row direction D1 and a column direction D2. The LEDs are electrically connected in series. The LEDs may include parallel-connected LEDs or LED strings. Power supplied to each unit 61 is supplied to the LEDs included in each unit 61. Light emitted by each unit 61 is emitted by the LEDs included in each unit 61.

[0024] The plurality of units 61 includes a plurality of monitored units 62 whose duty ratios are to be monitored.

[0025] The entire plurality of monitored units 62 occupies an area that is 0.3 times or more the area occupied by the entire plurality of units 61. The entire plurality of units 61 may be the entire plurality of monitored units 62. The positions at which the multiple monitored units 62 are arranged may be different from the positions illustrated in FIG. 2. The duty ratio 27 monitored by the control unit 33 includes the duty ratio of the power supplied to each monitored unit 62. Therefore, the control unit 33 monitors the duty ratio of the power supplied to each monitored unit 62, thereby monitoring the output brightness of the light emitted by each monitored unit 62.

[0026] 1.3 LCD panel FIG. 3 is a plan view schematically illustrating a liquid crystal panel provided in the liquid crystal display device of the first embodiment.

[0027] As shown in FIG. 3, the liquid crystal panel 36 includes a plurality of pixels 71 .

[0028] The plurality of pixels 71 are arranged in a matrix in a row direction D1 and a column direction D2.

[0029] As shown in FIG. 3, each pixel 71 comprises a red sub-pixel 81, a green sub-pixel 82 and a blue sub-pixel 83.

[0030] The red sub-pixels 81, green sub-pixels 82, and blue sub-pixels 83 are linearly arranged in the row direction D1.

[0031] The red subpixel 81, the green subpixel 82, and the blue subpixel 83 transmit red light, green light, and blue light, respectively. Each of the subpixels 80 of the red subpixel 81, the green subpixel 82, and the blue subpixel 83 includes a pixel electrode. Each subpixel 80 has a light transmittance that corresponds to the voltage written to the pixel electrode provided in that subpixel 80.

[0032] The voltage 29 supplied to the liquid crystal panel 36 includes a voltage written to a pixel electrode provided in each subpixel 80. The light transmittance of the liquid crystal panel 36 includes the light transmittance of each subpixel 80. Each subpixel 80 has a light transmittance that corresponds to the voltage written to the pixel electrode provided in that subpixel 80. Therefore, the drive unit 35 changes the light transmittance of each subpixel 80 by changing the voltage written to the pixel electrode provided in that subpixel 80.

[0033] 1.4 Brightness control in the first reference example In the first reference example, the control unit 33 performs a first control to set the output luminance 28 to the input luminance 24. However, the control unit 33 does not monitor the duty ratio 27 and does not control the output luminance 28 based on the duty ratio 27.

[0034] 4 is a graph showing an example of time changes in input luminance and output luminance in the first reference example. max 6 is a diagram showing an example of an image in which the input luminance is luminance L in the first reference example.

[0035] In the example shown in Fig. 4, during the period from timing T11 to timing T12, an image 91 having a bright area shown in Fig. 5 is input. Therefore, when the input luminance 24 is equal to the maximum luminance L max becomes.

[0036] In the subsequent period from timing T12 to timing T13, an image 92 having no bright areas shown in FIG. 6 is input. Therefore, the input luminance 24 is equal to the maximum luminance L max The smaller the luminance L, the

[0037] In the subsequent period from timing T13 to timing T14, the image 91 is input. Therefore, the input luminance 24 is equal to the maximum luminance L max becomes.

[0038] When the input luminance 24 becomes the above-mentioned luminance and the control unit 33 performs the above-mentioned control, the control unit 33 sets the output luminance 28 to the maximum luminance L 1 , which is the same as the input luminance 24, during the period from timing T11 to timing T12. max To do so.

[0039] Furthermore, the control unit 33 sets the output luminance 28 to the same luminance L as the input luminance 24 during the subsequent period from timing T12 to timing T13.

[0040] Furthermore, the control unit 33 sets the output luminance 28 to the maximum luminance L 1 , which is the same as the input luminance 24, during the period from timing T13 to timing T14. max To do so.

[0041] This is true regardless of the length of the period from timing T11 to timing T12, the period from timing T12 to timing T13, or the period from timing T13 to timing T14.

[0042] 1.5 Brightness control in the second reference example In the second reference example, the control unit 33 performs a first control to set the output luminance 28 to the input luminance 24.

[0043] Furthermore, the control unit 33 monitors the duty ratio 27 and controls the output luminance 28 based on the duty ratio 27. Specifically, when the output luminance 28 remains equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1, the control unit 33 performs a second control to reduce the output luminance 28 to a second threshold B or less. The second threshold B is smaller than the first threshold A. This prevents the temperature of the LEDs provided in the backlight 34 from rising above the upper limit temperature specified in the specifications.

[0044] Furthermore, the control unit 33 performs a third control to set the output luminance 28 to a third threshold C or less. The third threshold C is equal to or less than the first threshold A and is greater than the second threshold B. In the second reference example, the third threshold C is set to the same value as the first threshold A. The third threshold C may also be set to a value different from the first threshold A.

[0045] Furthermore, the control unit 33 alternately performs the second control and the third control, thereby temporarily increasing the output luminance 28 while suppressing the temperature of the LEDs provided in the backlight 34. This makes it possible to improve the display quality of the liquid crystal display device 1 while suppressing deterioration of the backlight 34.

[0046] Furthermore, if the input luminance 24 remains below the second threshold B for a period of time equal to or longer than the second time TL2 while the control unit 33 is performing the second control, the control unit 33 terminates the second control and performs the first control.

[0047] The first threshold value A is set so that when the output luminance 28 is equal to or greater than the first threshold value A, the temperature of the LEDs included in the backlight 34 may exceed the upper limit temperature specified for the LEDs. For example, when the maximum luminance L max If the first threshold A is 1000 nit, the first threshold A is set to 800 nit. The range of brightness that is equal to or greater than the first threshold A is the maximum brightness L max Therefore, the output brightness 28 is the maximum brightness L max In this case, the temperature of the LEDs provided in the backlight 34 may exceed the upper temperature limit specified for the LEDs.

[0048] The second threshold B is set so that the temperature of the LEDs included in the backlight 34 will not exceed the upper limit temperature specified when the output luminance 28 is equal to or less than the second threshold B. For example, when the maximum luminance L max is 1000 nits, the second threshold B is set to 500 nits.

[0049] Maximum brightness L max is the maximum value of the output luminance 28 when the input luminance 24 is within the normal luminance range.

[0050] The upper limit temperature of the LEDs provided in the backlight 34 according to specifications is, for example, 100°C.

[0051] The first time TL1 is the time from when the output luminance 28 becomes equal to or greater than the first threshold A until when the process of decreasing the output luminance 28 to equal to or less than the second threshold B is started. The first time TL1 is set to, for example, 30 seconds.

[0052] The second time TL2 is the time from when the input luminance 24 becomes equal to or less than the second threshold B until the process of changing the output luminance 28 to the input luminance 24 is started. The second time TL2 is set to, for example, 30 seconds.

[0053] 7 is a graph showing an example of time variations of input luminance and output luminance in the second reference example. max 6 is also a diagram showing an example of an image in which the input luminance is luminance L in the second reference example.

[0054] 7, the image 91 is input during the period from timing T21 to timing T28. Therefore, when the input luminance 24 reaches the maximum luminance L max becomes.

[0055] During the subsequent period from timing T28 to timing T29, video 92 is input. Therefore, input luminance 24 becomes luminance L, which is smaller than first threshold A and second threshold B.

[0056] In the subsequent period from timing T29 to timing T31, the image 91 is input. Therefore, the input luminance 24 is the maximum luminance L max becomes.

[0057] When the input luminance 24 becomes the above-mentioned luminance and the control unit 33 performs the above-mentioned control, the control unit 33 performs the first control in the period from timing T21 to timing T22, and sets the output luminance 28 to the maximum luminance L max Timing T22 is the timing when the first time TL1 has elapsed since the output luminance 28 became equal to or greater than the first threshold value A.

[0058] Furthermore, the control unit 33 sets the output luminance 28 to the maximum luminance L 1 , which is the same as the input luminance 24, during the period from timing T22 to timing T23. max to a second threshold B which is less than the input luminance 24.

[0059] Furthermore, the control unit 33 performs a second control in the subsequent period from timing T23 to timing T24, and sets the output luminance 28 to a second threshold value B that is lower than the input luminance 24.

[0060] Furthermore, the control unit 33 increases the output luminance 28 from the second threshold B, which is lower than the input luminance 24, to the third threshold C, which is lower than the input luminance 24, during the subsequent period from timing T24 to timing T25.

[0061] Furthermore, the control unit 33 performs a third control in the subsequent period from timing T25 to timing T26, and sets the output luminance 28 to a third threshold C that is lower than the input luminance 24.

[0062] Furthermore, the control unit 33 reduces the output luminance 28 from the third threshold C, which is lower than the input luminance 24, to the second threshold B, which is lower than the input luminance 24, during the subsequent period from timing T26 to timing T27.

[0063] Furthermore, the control unit 33 performs a second control in the subsequent period from timing T27 to timing T28, and sets the output luminance 28 to a second threshold value B that is lower than the input luminance 24.

[0064] Furthermore, the control unit 33 continues to perform the second control during the subsequent period from timing T28 to timing T29, and sets the output luminance 28 to the luminance L that is the same as the input luminance 24.

[0065] Furthermore, the control unit 33 continues the second control during the subsequent period from timing T29 to timing T30, and sets the output luminance 28 to luminance L which is lower than the input luminance 24. In the second reference example, the output luminance 28 is set to luminance L which is lower than the input luminance 24 during this period. This is because, in the second reference example, the control unit 33 continues the second control that sets the output luminance 28 to be equal to or lower than the second threshold value B until the second time TL2 has elapsed, and waits until the second time TL has elapsed before returning from the second control to the first control.

[0066] Furthermore, the control unit 33 performs the first control in the period from the next timing T30 to the timing T31, and sets the output luminance 28 to the maximum luminance L max To do so.

[0067] 1.6 Brightness Control in the First Embodiment In the first embodiment, the control unit 33 performs a first control to set the output luminance 28 to the input luminance 24.

[0068] Furthermore, the control unit 33 monitors the duty ratio 27 and controls the output luminance 28 based on the duty ratio 27. Specifically, when the output luminance 28 remains equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1, the control unit 33 performs a second control to reduce the output luminance 28 to a value equal to or less than the second threshold B. The second threshold B is smaller than the first threshold A.

[0069] Furthermore, if the input luminance 24 becomes equal to or less than the second threshold value B while the second control is being performed, the control unit 33 terminates the second control and performs the first control. Unlike the second reference example, if the input luminance 24 becomes equal to or less than the second threshold value B while the second control is being performed, the control unit 33 can perform the first control without waiting for the second time TL2 to elapse.

[0070] The first threshold A, the second threshold B, and the first time TL1 in the first embodiment are respectively the same as the first threshold A, the second threshold B, and the first time TL1 in the second reference example.

[0071] 8 is a graph showing an example of time variations of input luminance and output luminance in the first embodiment. max 6 is also a diagram showing an example of an image in which the input luminance is luminance L in the first embodiment.

[0072] 8, the image 91 is input during the period from timing T41 to timing T44. Therefore, when the input luminance 24 reaches the maximum luminance L max becomes.

[0073] During the subsequent period from timing T44 to timing T45, video 92 is input. Therefore, input luminance 24 becomes luminance L, which is smaller than first threshold A and second threshold B.

[0074] In the subsequent period from timing T45 to timing T46, the image 91 is input. Therefore, the input luminance 24 becomes the maximum luminance L max becomes.

[0075] When the input luminance 24 becomes the above-mentioned luminance and the control unit 33 performs the above-mentioned control, the control unit 33 performs the first control in the period from timing T41 to timing T42, and sets the output luminance 28 to the maximum luminance L max Timing T42 is the timing when the first time TL1 has elapsed since the output luminance 28 became equal to or greater than the first threshold value A.

[0076] Furthermore, in the subsequent period from timing T42 to timing T43, the control unit 33 sets the output luminance 28 to the maximum luminance L max to a second threshold B which is less than the input luminance 24.

[0077] Furthermore, the control unit 33 performs a second control in the subsequent period from timing T43 to timing T44, and sets the output luminance 28 to a second threshold value B that is lower than the input luminance 24.

[0078] Furthermore, the control unit 33 continues to perform the second control during the subsequent period from timing T44 to timing T45, and sets the output luminance 28 to the luminance L that is the same as the input luminance 24.

[0079] Furthermore, the control unit 33 performs the first control in the period from the next timing T45 to timing T46, and sets the output luminance 28 to the maximum luminance L max In the period from timing T45 to timing T46 in the first embodiment, unlike the period from timing T29 to timing T30 in the second reference example, the output luminance 28 is set to the same maximum luminance L max This is because, in the first embodiment, unlike the second reference example, the control unit 33 does not continue the second control that keeps the output luminance 28 equal to or less than the second threshold B until the second time TL2 has elapsed, and returns from the second control to the first control without waiting for the second time TL to elapse. This is regardless of the length of the period from timing T44 to timing T45. Therefore, even if the period is only for an instant, the return from the second control to the first control is performed.

[0080] According to the first embodiment, even when the output luminance 28 is reduced to prevent the temperature of the LEDs provided in the backlight 34 from rising above the upper limit temperature specified in the specifications, the output luminance 28 can be increased in a short time. This allows the output luminance 28 to be increased in a short time when the image 91 is input following the image 92. This allows the display quality of the liquid crystal display device 1 to be improved.

[0081] 1.7 Processing flow performed by the control unit FIG. 9 is a flowchart showing the flow of processing performed by the control unit provided in the liquid crystal display device of the first embodiment.

[0082] The control unit 33 executes steps S101 to S106 shown in FIG.

[0083] In step S101, the control unit 33 determines whether the input luminance 24 is less than the first threshold value A. If it is determined that the input luminance 24 is less than the first threshold value A, step S102 is executed. If it is not determined that the input luminance 24 is less than the first threshold value A, step S103 is executed.

[0084] In step S102, the control unit 33 sets the output luminance 28 to the input luminance 24. Step S102 is executed when it is determined that the input luminance 24 is smaller than the first threshold value A. Therefore, in step S102, the control unit 33 performs the first control or the second control to set the output luminance 28 to the input luminance 24, thereby making the output luminance 28 smaller than the first threshold value A. After step S102 is executed, step S101 is executed again.

[0085] Through steps S101 and S102, the control unit 33 continues to set the output luminance 28 to the input luminance 24 while the state in which the input luminance 24 is equal to or less than the first threshold value A continues.

[0086] In step S103, the control unit 33 sets the output luminance 28 to be equal to or greater than the first threshold value A. Step S103 is executed when it is determined that the input luminance 24 is equal to or greater than the first threshold value A. Therefore, in step S103, the control unit 33 performs the first control to set the output luminance 28 to the input luminance 24, thereby setting the output luminance 28 to be equal to or greater than the first threshold value A.

[0087] In the following step S104, the control unit 33 determines whether the output luminance 28 is equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1. If it is determined that the output luminance 28 is equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1, step S105 is executed. If it is not determined that the output luminance 28 is equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1, step S103 is executed again. For example, if at least one monitored unit 62 having an output luminance of emitted light equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1 is included in the multiple monitored units 62, the control unit 33 determines that the output luminance 28 is equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1. Furthermore, the control unit 33 repeatedly monitors the output luminance, and if it determines that the output luminance is equal to or greater than the first threshold A during the monitoring, it counts. If the cumulative count reaches a set value or greater, the control unit 33 determines that the output luminance is equal to or greater than the first threshold A for a period of time equal to or greater than the first time TL1.

[0088] In step S105, the control unit 33 performs the second control to set the output luminance 28 to the second threshold B. By setting the upper limit of the output luminance 28 to the second threshold B, the control unit 33 sets the output luminance 28 to the second threshold B even if the input luminance 24 is greater than the second threshold B. In transitioning to the second control, the control unit 33 gradually lowers the upper limit of the output luminance 28 toward the second threshold B, and finally sets the upper limit of the output luminance 28 to the second threshold B.

[0089] By steps S103 to S105, control unit 33 continues to make output luminance 28 equal to or greater than first threshold value A before the first time TL1 has elapsed since output luminance 28 became equal to or greater than first threshold value A. On the other hand, after the first time TL1 has elapsed since output luminance 28 became equal to or greater than first threshold value A, control unit 33 stops making output luminance 28 equal to or greater than first threshold value A and sets output luminance 28 to second threshold value B.

[0090] In the following step S106, the control unit 33 determines whether the input luminance 24 or the output luminance 28 is equal to or less than the second threshold value B. If it is determined that the input luminance 24 or the output luminance 28 is equal to or less than the second threshold value B, step S102 is executed again. If it is not determined that the input luminance 24 or the output luminance 28 is equal to or less than the second threshold value B, step S105 is executed again.

[0091] In steps S105, S106, and S102, the control unit 33 sets the output luminance 28 to the input luminance 24 in response to the input luminance 24 becoming equal to or less than the second threshold B. As a result, the control unit 33 sets the output luminance 28 to equal to or less than the second threshold B. After setting the output luminance 28 to equal to or less than the second threshold B in step S102, if the control unit 33 does not determine in step S101 that the input luminance 24 is less than the first threshold A, that is, if the control unit 33 determines in step S101 that the input luminance 24 is equal to or greater than the first threshold A, the control unit 33 immediately sets the output luminance 28 to equal to or greater than the first threshold A in step S103. This allows the output luminance 28 to be increased in a short period of time. Meanwhile, the control unit 33 continues to set the output luminance 28 to the second threshold B until the input luminance 24 becomes equal to or less than the second threshold B.

[0092] 1.8 Brightness control in the modified example of the first embodiment In the modification of the first embodiment, the control unit 33 performs a first control to set the output luminance 28 to the input luminance 24.

[0093] Furthermore, when the state in which the output luminance 28 is equal to or greater than the first threshold A continues for a period of time equal to or greater than the first time period TL1, the control unit 33 performs a second control to reduce the output luminance 28 to equal to or less than the second threshold B. The second threshold B is smaller than the first threshold A.

[0094] Furthermore, the control unit 33 performs a third control to set the output luminance 28 to a third threshold C or less. The third threshold C is equal to or less than the first threshold A and is greater than the second threshold B. In a modification of the first embodiment, the third threshold C is set to the same value as the first threshold A. The third threshold C may also be set to a value different from the first threshold A.

[0095] Moreover, the control unit 33 alternately performs the second control and the third control.

[0096] Furthermore, when the input luminance 24 becomes equal to or less than the second threshold value B while the control unit 33 is performing the second control, the control unit 33 stops performing the second control and performs the first control.

[0097] 10 is a graph showing an example of time variations of input luminance and output luminance in the modified example of the first embodiment. max 6 is also a diagram showing an example of an image in which the input luminance is luminance L in the modification of the first embodiment.

[0098] 10, the image 91 is input during the period from timing T51 to timing T58. Therefore, when the input luminance 24 reaches the maximum luminance L max becomes.

[0099] During the subsequent period from timing T58 to timing T59, video 92 is input. Therefore, input luminance 24 becomes luminance L, which is smaller than first threshold A and second threshold B.

[0100] During the subsequent period from timing T59 to timing T60, video 91 is input. Therefore, the input luminance 24 reaches the maximum luminance L max becomes.

[0101] When the input luminance 24 becomes the above-mentioned luminance and the control unit 33 performs the above-mentioned control, the control unit 33 performs the first control in the period from timing T51 to timing T52, and sets the output luminance 28 to the maximum luminance L max Timing T52 is the timing when the first time TL1 has elapsed since the output luminance 28 became equal to or greater than the first threshold value A.

[0102] Furthermore, in the subsequent period from timing T52 to timing T53, the control unit 33 sets the output luminance 28 to the maximum luminance L max to a second threshold B which is less than the input luminance 24.

[0103] Furthermore, the control unit 33 performs a second control in the subsequent period from timing T53 to timing T54, and sets the output luminance 28 to a second threshold value B that is lower than the input luminance 24.

[0104] Furthermore, the control unit 33 increases the output luminance 28 from the second threshold value B, which is lower than the input luminance 24, to the third threshold value C, which is lower than the input luminance 24, during the subsequent period from timing T54 to timing T55.

[0105] Furthermore, the control unit 33 performs a third control in the subsequent period from timing T55 to timing T56, and sets the output luminance 28 to a third threshold C that is lower than the input luminance 24.

[0106] Furthermore, the control unit 33 reduces the output luminance 28 from the third threshold C, which is lower than the input luminance 24, to the second threshold B, which is lower than the input luminance 24, during the subsequent period from timing T56 to timing T57.

[0107] Furthermore, the control unit 33 performs a second control in the subsequent period from timing T57 to timing T58, and sets the output luminance 28 to a second threshold value B that is lower than the input luminance 24.

[0108] Furthermore, the control unit 33 continues to perform the second control during the subsequent period from timing T58 to timing T59, and sets the output luminance 28 to the luminance L that is the same as the input luminance 24.

[0109] Furthermore, the control unit 33 performs the first control in the period from the next timing T59 to timing T60, and sets the output luminance 28 to the maximum luminance L maxIn the period from timing T59 to timing T60 in the modified example of the first embodiment, unlike the period from timing T29 to timing T30 in the second reference example, the output luminance 28 is set to the same maximum luminance L max This is because, unlike the second reference example, even in the modified example of the first embodiment, the control unit 33 does not continue the second control that keeps the output luminance 28 equal to or less than the second threshold B until the second time TL2 has elapsed, and returns from the second control to the first control without waiting for the second time TL to elapse. This is regardless of the length of the period from timing T57 to timing T58. Therefore, even if the period is only for an instant, the return from the second control to the first control is performed.

[0110] 2. Second embodiment The following describes the differences between the second embodiment and the first embodiment. For points that are not described, the second embodiment also employs the same configuration as that employed in the first embodiment.

[0111] FIG. 11 is a block diagram of a liquid crystal display device according to the second embodiment.

[0112] In the liquid crystal display device 2 of the second embodiment shown in FIG.

[0113] The sensor 37 detects the temperature 101 of the environment surrounding the backlight 34. The detected temperature 101 may be the temperature of the backlight 34 or an LED provided in the backlight 34.

[0114] The control unit 33 sets the first threshold A and the second threshold B based on the detected temperature 101. For example, the lower the temperature 101, the larger the first threshold A and the second threshold B are set by the control unit 33. As a result, when the temperature 101 is low and the constraint on the temperature increase of the backlight 34 is weak, the first threshold A and the second threshold B can be increased to increase the output luminance 28. On the other hand, when the temperature 101 is high and the constraint on the temperature increase of the backlight 34 is strong, the first threshold A and the second threshold B can be decreased to decrease the output luminance 28. As a result, the output luminance 28 can be increased within the range of the constraint imposed by the temperature 101. As a result, the display quality of the liquid crystal display device 2 can be improved within the range of the constraint imposed by the temperature 101.

[0115] Fig. 12 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is 35°C or higher in the second embodiment. Fig. 13 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is lower than 35°C in the second embodiment.

[0116] 12 and 13, when the temperature 101 is equal to or higher than 35° C., the control unit 33 sets the first threshold A and the second threshold B to values ​​a and b, respectively, as shown in Fig. 12. On the other hand, when the temperature 101 is lower than 35° C., the control unit 33 sets the first threshold A and the second threshold B to values ​​a' and b', respectively, which are greater than value a and b, as shown in Fig. 13.

[0117] 3 Third embodiment The following describes the differences between the third embodiment and the first embodiment. For points that are not described, the third embodiment also employs the same configuration as that employed in the first embodiment.

[0118] FIG. 11 is also a block diagram of a liquid crystal display device according to the third embodiment.

[0119] In the liquid crystal display device 3 of the third embodiment shown in FIG.

[0120] The sensor 37 detects the temperature 101 of the environment surrounding the backlight 34. The detected temperature 101 may be the temperature of the backlight 34 or an LED provided in the backlight 34.

[0121] The control unit 33 sets a first time required to reduce the output luminance 28 and a second time required to increase the output luminance 28 based on the detected temperature 101. For example, the control unit 33 lengthens the first time and shortens the second time as the temperature 101 decreases. As a result, when the temperature 101 is low and the constraint on the increase in the temperature of the backlight 34 is weak, the control unit 33 can lengthen the first time to make the output luminance 28 less likely to decrease and shorten the second time to make the output luminance 28 more likely to increase. On the other hand, when the temperature 101 is high and the constraint on the increase in the temperature of the backlight 34 is strong, the control unit 33 can shorten the first time to make the output luminance 28 more likely to decrease and lengthen the second time to make the output luminance 28 less likely to increase. This can lengthen the time during which the output luminance 28 is high within the constraints imposed by the temperature 101. This can improve the display quality of the liquid crystal display device 3 within the constraints imposed by the temperature 101.

[0122] Fig. 14 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is 35°C or higher in the third embodiment. Fig. 15 is a graph showing an example of temporal changes in input luminance and output luminance when the temperature is lower than 35°C in the third embodiment.

[0123] In the examples shown in FIGS. 14 and 15, when the temperature 101 is 35° C. or higher, the control unit 33 sets the output luminance 28 to the maximum luminance L 2 that is equal to or higher than the first threshold value A, as shown in FIG. maxThe control unit 33 sets the first time required to decrease the output luminance 28 from the first threshold value B to the second threshold value B as time ΔT1, and sets the second time required to increase the output luminance 28 from the second threshold value B to the third threshold value C as time ΔT2. On the other hand, when the temperature 101 is lower than 35° C., the control unit 33 sets the output luminance 28 to the maximum luminance L as shown in FIG. max The control unit 33 sets the first time required to decrease the output luminance 28 from the first threshold value B to the second threshold value B to a time ΔT1' longer than the time ΔT1, and sets the second time required to increase the output luminance 28 from the second threshold value B to the third threshold value C to a time ΔT2' shorter than the time ΔT2. The control unit 33 sets the time ΔT1' and the time ΔT2' so that the absolute value of the time rate of change of the output luminance 28 (slope of the graph) when increasing the output luminance 28 is greater than the absolute value of the time rate of change of the output luminance 28 (slope of the graph) when decreasing the output luminance 28.

[0124] The present disclosure is not limited to the above-described embodiments, and may be replaced with a configuration that is substantially the same as the configuration shown in the above-described embodiments, a configuration that has the same effect, or a configuration that can achieve the same purpose. [Explanation of symbols]

[0125] 1 liquid crystal display device, 2 liquid crystal display device, 3 liquid crystal display device, 11 antenna, 21 broadcast wave, 22 received signal, 23 video signal, 24 input brightness, 25 light transmittance, 26 power, 27 duty ratio, 28 output brightness, 29 voltage, 31 tuner, 32 acquisition unit, 33 control unit, 34 backlight, 35 drive unit, 36 liquid crystal panel, 37 sensor, 41 control device, 51 light, 52 video light, 61 unit, 62 monitored unit, 71 pixel, 80 subpixel, 81 red subpixel, 82 green subpixel, 83 blue subpixel, 91 video, 92 video, 101 temperature.

Claims

1. A control device that controls a backlight provided in a display device, an acquisition unit that acquires input luminance from a video signal; a control unit that performs a first control to set the output luminance of light emitted by the backlight to the input luminance, and when the output luminance continues to be equal to or greater than a first threshold value for a set time or longer, performs a second control to set the output luminance to or less than a second threshold value that is smaller than the first threshold value, and when the input luminance becomes equal to or less than the second threshold value while performing the second control, terminates performing the second control and performs the first control; A control device comprising:

2. Equipped with a sensor that detects temperature, The control unit sets the first threshold value and the second threshold value based on the temperature. The control device according to claim 1 .

3. The control unit increases the first threshold value and the second threshold value as the temperature decreases. The control device according to claim 2 .

4. Equipped with a sensor that detects temperature, The control unit sets a first time required to decrease the output luminance and a second time required to increase the output luminance based on the temperature. The control device according to claim 1 .

5. The control unit increases the first time period and decreases the second time period as the temperature decreases. The control device according to claim 4.

6. A control device according to any one of claims 1 to 5; the backlight; a liquid crystal panel that transmits the light; A liquid crystal display device comprising:

Images