WO2013080634A1 - Liquid crystal display apparatus, comparison circuit, and television receiver - Google Patents

Abstract

A television receiver (1) according to this invention comprises: a control unit (11) for controlling a scan line driver circuit (12) and a signal line driver circuit (13); and a comparator (15) for comparing a voltage of a monitor pixel electrode (152) with a predetermined threshold value. The control unit (11) controls the image refresh timing in accordance with a comparison result of the comparator (15).

Description

Liquid crystal display device, comparison circuit, and television receiver

The present invention relates to a liquid crystal display device. Further, the present invention relates to a voltage comparator provided in a liquid crystal display device, and a television receiver provided with the liquid crystal display device.

In recent years, the size of liquid crystal panels included in television receivers (hereinafter also referred to as televisions) has been increased. Along with this, the power consumption of the liquid crystal panel is increasing, and the reduction of the power consumption is an issue.

Furthermore, in recent years, development of a television (so-called 4K2K television) having a liquid crystal panel having a high resolution of about 4000 × 2000 has been advanced. Along with the development of televisions with such high resolution, not only moving images represented by broadcast programs and content recorded in video but also opportunities for displaying still images and moving images with few image changes on television It is increasing.

On the other hand, when the image displayed on the liquid crystal panel is a moving image, the display image is rewritten at a predetermined rewriting cycle (so-called refresh rate), but the still image and the image change are small. In this case, a technique has been developed to reduce power consumption by reducing the number of times the display image is rewritten by reducing the refresh rate.

Here, the voltage applied to each pixel provided in the liquid crystal panel to display an image on the display panel is held in a capacitor (for example, a capacitor or the like) provided in each pixel. In addition, the voltage held by the capacitor gradually decreases due to the leak current of the switching element (for example, a TFT (thin film transistor) or the like) included in each pixel.

Therefore, in the case of a still image and a moving image with a small change in image, it is necessary to rewrite (refresh) the displayed image before the displayed image changes due to the change in voltage of the pixel due to the leak current. is there.

According to Patent Document 1, when the image information displayed on the liquid crystal panel is not changed for a fixed time, the driving voltage and the driving frequency of the information signal applied to the information electrode of each pixel are lowered and the temperature of the liquid crystal panel There is disclosed a technique for controlling the drive voltage and drive frequency of the information signal in accordance with the above.

Japanese Patent Publication "Japanese Patent Application Laid-Open No. 9-5710 (Jan. 10, 1997)"

However, the leakage current in each switching element is different due to the variation of the characteristic at the time of manufacture and the characteristic changing with the passage of years of use (aging change) other than the temperature change. That is, in addition to the temperature change of each switching element due to the temperature change of the liquid crystal panel, the leak current also changes due to the dispersion of the characteristics and the like. Therefore, although the refresh rate can be changed according to the temperature change of the liquid crystal panel in the technology described in Patent Document 1, it is possible to change the leak current due to the variation of the characteristics of each switching element and aging. It can not be properly controlled accordingly.

Further, in the technique described in Patent Document 1, as described above, the refresh rate is controlled according to the temperature change of the liquid crystal panel, not the temperature change of each pixel. For this reason, when the temperature change of one part of the liquid crystal panel is more significant than the temperature change of the other part, the image displayed on the part of pixels may change.

Therefore, the technique described in Patent Document 1 has a problem that the control of the refresh rate can not be performed with high accuracy.

The present invention has been made to solve the above-described problems, and its main object is to provide a liquid crystal display device capable of performing control of the image rewriting timing (that is, the refresh timing) with higher accuracy. It is to provide.

A liquid crystal display device according to an aspect of the present invention includes a plurality of in-region pixels arranged in a display region for displaying an image, and at least one of a plurality of pixels arranged outside the display region. A display panel having three out-of-area pixels, a scanning signal supply circuit for supplying a scanning signal to the in-area pixels and the out-of-area pixels, and each pixel electrode of the in-area pixels and the out-of-area pixels A liquid crystal display device comprising an image signal supply circuit for supplying an image signal and a control unit for controlling the scan signal supply circuit and the image signal supply circuit; The image processing apparatus further comprises a comparison circuit that compares the threshold with the threshold value, and the control unit controls the timing of image refresh according to the comparison result by the comparison circuit.

A comparison circuit according to an aspect of the present invention is a comparison circuit formed on a display panel of a liquid crystal display device for comparing an input voltage with a predetermined threshold voltage, the source connected to a voltage input node, and a capacitor A first transistor having a drain connected to one end of the capacitor and a gate connected to the first control signal input node, a source connected to the other end of the capacitor, and a drain connected to an intermediate node, And a second transistor having a gate connected to the first control signal input node, a source connected to the intermediate node, a drain connected to the output node, and a second control signal input node. A third transistor having a gate connected, a source connected to the output node, a drain connected to ground, and the intermediate node Connected to a reference voltage power supply, a fourth transistor having a gate, a source connected to the intermediate node, a drain connected to ground, and a fifth transistor having a gate connected to a third control signal input node A sixth transistor having a source, a drain connected to the other end of the first resistor whose one end is connected to the output node, and a gate connected to the second control signal input node; A second resistor whose one end is connected to the reference voltage power supply and whose other end is connected to the output node; an input voltage is input to the voltage input node; and the comparison result is shown from the output node It is characterized in that an output voltage is output.

A television receiver provided with the above-described playback device also falls within the scope of the present invention.

As described above, the liquid crystal display device according to the present invention includes a plurality of in-region pixels arranged in the display region for displaying an image, and at least one out-of-region pixels arranged outside the display region. And a scanning signal supply circuit for supplying a scanning signal to the in-area pixel and the out-of-area pixel, and an image signal to each pixel electrode provided in the in-area pixel and the out-of-area pixel An image signal supply circuit, a control unit that controls the scan signal supply circuit and the image signal supply circuit, and a comparison circuit that compares a voltage of a pixel electrode of the out-of-region pixel with a predetermined threshold value. The control unit is characterized in that it controls the timing of image refresh according to the comparison result by the comparison circuit.

Therefore, the liquid crystal display device can control the timing of image refresh with high accuracy.

It is a figure which shows the outline of the whole structure of the television which concerns on one Embodiment of this invention. It is a timing chart which shows operation of a television in the case of displaying a moving picture on a display field with which a television concerning one embodiment of the present invention is provided. It is a timing chart which shows operation of a television in the case of displaying a still picture on a display field with which a television concerning one embodiment of the present invention is provided. It is a timing chart which shows operation of a television which measures leak time, when displaying a still picture on a display field with which a television concerning one embodiment of the present invention is provided. It is a timing chart which shows operation of a television which changes voltage and supply time of a scanning signal based on leak time, when displaying a still picture on a display field with which a television concerning one embodiment of the present invention is provided. When displaying a still picture on the display area with which the television which concerns on one Embodiment of this invention is equipped, it is a timing chart which shows operation | movement of the television which comprises 1 frame by multiple fields. It is a figure showing the outline of the display panel with which the television concerning one example of one embodiment of the present invention is provided. It is a figure which shows the outline of the display panel with which the television based on the other Example of one Embodiment of this invention is provided. It is a figure which shows the outline of the display panel with which the television based on the further another Example of one Embodiment of this invention is provided. It is a circuit diagram showing composition of a comparator with which a television concerning other embodiments of the present invention is provided. It is a timing chart which shows operation of a comparator with which a television concerning other embodiments of the present invention is provided. It is a figure which shows the outline of the whole structure of the television which concerns on other embodiment of this invention.

First Embodiment
A liquid crystal display device according to an embodiment of the present invention will be described with reference to FIG. 1 to FIG. However, the configuration described in this embodiment is not intended to limit the scope of the present invention to that alone, unless otherwise specifically described, and is merely an illustrative example. In addition, since the liquid crystal display device according to the present embodiment is realized by a television receiver (hereinafter, also referred to as a television), it is hereinafter referred to as a television.

In the following, the case where the liquid crystal display device is a television will be described as an example, but the present invention is not limited to this. The liquid crystal display device according to the present invention may be, for example, a personal computer, a PDA (Personal Digital Assistant: Personal Digital Assistants), a tablet PC, a mobile phone, a smartphone, or the like.

[Configuration of TV]
The configuration of the television 1 according to the present embodiment will be described with reference to FIG. FIG. 1 is a diagram showing an outline of the overall configuration of a television 1 according to the present embodiment. As shown in FIG. 1, the television 1 includes a display panel 10, a control unit 11, and a comparator (comparison circuit) 15.

(Display panel)
The display panel 10 includes a scanning line drive circuit (scan signal supply circuit) 12, a signal line drive circuit (image signal supply circuit) 13, and a display area 14 for displaying an image by driving a plurality of pixels. . The scanning line driving circuit 12 and the signal line driving circuit 13 are provided in a non-display area (so-called frame area) outside the display area.

The display panel 10 includes a total of P scanning lines (where P is an integer of 1 or more) in the display area 14, and a total number Q columns arranged to intersect each scanning line (where Q is an integer of 1 or more). And a plurality of pixels (in-area pixels) provided at the intersections of the scanning lines and the signal lines.

In each pixel, a pixel electrode 142 is provided, and a TFT (switching element) 141 is provided to turn on and off the electrical connection between the pixel electrode 142 and the signal line by a scanning signal supplied to the scanning line. ing. The gate electrode of the TFT 141 is connected to the scanning line, the source terminal is connected to the signal line, and the drain terminal is connected to the pixel electrode 142.

Furthermore, the display panel 10 is provided on the signal line drive circuit 13 side in the non-display area at the intersection of the monitor scanning line m in one row and the monitoring scanning line m and the total number Q of signal lines. A plurality of monitor pixels (outside pixels) are provided.

A monitor pixel electrode 152 is provided in each monitor pixel, and a monitor for turning on and off the electrical connection between the monitor pixel electrode 152 and the signal line by a scan signal supplied to the monitor scan line m. TFT (switching element) 151 is provided. The gate electrode of the monitor TFT 151 is connected to the monitor scan line m, the source terminal is connected to the signal line, and the drain terminal is connected to the monitor pixel electrode 152.

In the present embodiment, the monitor pixel is not used to display an image, and is used to monitor a change in the characteristics of the TFT during the operation of the television 1 as described later. It is not limited and, of course, may be used to display an image.

Of the three terminals provided for the TFT 141 and the monitoring TFT 151 for convenience of explanation, for the two terminals other than the gate terminal, the terminal connected to the signal line is called a source terminal, and the pixel electrode 142 and the monitor pixel electrode 152 The terminal connected to is referred to as a drain terminal, but may be reversed.

The semiconductor layer of the TFT 141 and the monitoring TFT 151 is generally formed of, for example, a-Si (amorphous silicon), but is not limited thereto.

The image displayed in the display area 14 may be a moving image or a still image. As a case where a still image is displayed on a display area, the case where a moving image is paused, etc. can be mentioned, for example.

(Control unit)
The control unit 11 controls the scanning line driving circuit 12 and the signal line driving circuit 13 to control the timing of refreshing the image displayed on the display area 14 of the display panel 10. Specifically, a synchronization signal and a gate clock signal sent from the outside are acquired, and a control signal for displaying an image in the display area 14 is output. The control unit 11 outputs a scan control signal, a gate clock signal, a gate start pulse signal, and the like to be described later to the scan line drive circuit 12. Further, the control unit 11 outputs a source clock signal, a source start pulse signal, a latch strobe signal, a polarity inversion signal, and the like to the signal line drive circuit 13.

In addition, when the image displayed in the display area 14 is a still image or a moving image with a small change in image, the control unit 11 causes the scanning line drive circuit 12 and the signal line drive circuit 13 to decrease the refresh rate. Control.

Furthermore, as described later, the control unit 11 outputs a voltage indicating a predetermined threshold, and acquires a comparison result by the comparator 15. The control unit 11 controls the scanning line drive circuit 12 and the signal line drive circuit 13 to refresh the image regardless of the set refresh rate when the comparison result input from the comparator 15 indicates a predetermined threshold. Control. The control unit 11 may control the scan line drive circuit 12 and the signal line drive circuit 13 by, for example, supplying a refresh signal indicating that the image is to be refreshed to the scan line drive circuit 12 and the signal line drive circuit 13. .

The threshold data indicating the value of the predetermined threshold voltage may be stored in advance in a memory (not shown) included in the television 1. The method of setting the threshold data will be described later.

(Scan line drive circuit)
The scanning line drive circuit 12 supplies a scanning signal to the pixels and the monitor pixels. Specifically, the scanning of the scanning line is started using the gate start pulse signal received from the control unit 11 as a signal.

When the scanning line driving circuit 12 starts supplying a scanning signal, the scanning line driving circuit 12 sequentially applies a scanning voltage from the scanning line of the first row in the display area according to the gate clock signal and the gate output control signal received from the control unit 11. A scan voltage is applied to all the scan lines in a row. Furthermore, the scanning line drive circuit 12 applies a scanning voltage also to the monitor scanning line m provided in the non-display area. Thus, the scanning line driving circuit 12 sequentially supplies a scanning signal having a scanning voltage for turning on the TFTs 141 and the monitoring TFTs 151 included in the pixels on the scanning lines, to each scanning line. Note that supplying a scanning signal (that is, applying a scanning voltage) to turn on the TFT 141 and the monitoring TFT 151 with respect to each scanning line is also described as scanning the scanning line hereinafter.

(Signal line drive circuit)
The signal line drive circuit 13 supplies an image signal to the pixel electrode 142 of the pixel and the monitor pixel electrode 152 of the monitor pixel. Specifically, based on the image data input from the outside and the source start pulse signal received from control unit 11, signal line drive circuit 13 registers the image signal of each pixel according to the source clock signal (not shown). Store in In addition, the signal line drive circuit 13 supplies an image signal indicating image data to each signal line of the display panel 10 according to the next source latch strobe signal, and the pixel electrode 142 and monitor provided in the pixel including each signal line Pixel electrode 152 is charged.

The signal line drive circuit 13 calculates the value of the voltage to be output to each pixel on the selected scanning line based on the input image data, and outputs the voltage of that value to each signal line. As a result, an image signal is supplied to each pixel and monitor pixel on the selected scanning line.

Further, the signal line drive circuit 13 sets the polarity of the image signal to be applied to the selected pixel which is a pixel to be selected in a certain field according to the polarity inversion signal received from the control unit Inverts in units of selected pixels of The signal line drive circuit 13 further controls the polarity of the image signal applied to each selected pixel in a certain field to that of the image signal applied to the selected pixel in the field immediately before the selected field. Invert to the polarity.

(Comparator)
The comparator 15 compares the voltage of the monitor pixel electrode 152 (hereinafter also referred to as monitor voltage) with the voltage indicating the predetermined threshold supplied from the control unit 11 (hereinafter also simply referred to as threshold voltage). . Specifically, the comparator 15 determines the timing at which the absolute value of the voltage held by the monitor pixel electrode 152 is reduced by the leak current of the monitor TFT 151 to be equal to or less than the absolute value of the threshold.

The comparator 15 can be realized by, for example, a comparator or the like, but the present invention is not limited to this.

The threshold voltage supplied from the control unit 11 to the comparator 15 is also “+” if the polarity of the voltage held in the monitor pixel electrode 152 is “+”. Good. Further, when the polarity of the voltage held in the monitor pixel electrode 152 is “−”, the threshold voltage may be “−” as well.

The comparator 15 outputs a monitor determination signal when the absolute value of the monitor voltage becomes equal to or less than the absolute value of the threshold.

(Setting of threshold data)
Here, an example of a method of setting threshold data will be described.

For example, a test mode is provided in the television 1 for displaying a test image, and the control unit 11 measures the voltage of each pixel in a state where the test image is displayed in the display area 14. As a result, the control unit 11 measures the voltage at the time when the image changes in the pixel where the image displayed in each pixel changes most rapidly (is defective). Next, the control unit 11 stores data indicating the measured value of the voltage in the memory as threshold data.

Thus, by setting the threshold data in the test mode, the control unit 11 can supply the comparator 15 with an optimal threshold voltage. Note that by setting the threshold data before shipment of the television 1, the user can set the television in a state in which the optimum threshold data according to the characteristics of the pixels included in the television 1, the TFT 141 and the pixel electrode 142 are preset. 1 can be used.

The threshold data stored in the memory may be rewritable (reset). For example, the setting may be made by the user by operating the remote controller.

According to the above-described configuration, the threshold data can be set optimally and reset, so that the comparison between the monitor voltage and the threshold voltage in the comparator 15 can be given freedom.

The control unit 11 according to the present embodiment may include a D / A converter (not shown) in order to supply the threshold voltage with reference to the threshold data stored in the memory.

[Operation of TV]
Next, the operation of the television 1 according to the present embodiment will be described with reference to FIG. 2 to FIG. Here, the operation of the television 1 in the case of displaying a still image and a moving image with little change in the image will be described by taking the operation of the television 1 in the case of displaying a still image as an example.

(Display of moving image)
First, the case where a normal moving image (that is, not a moving image with a small change in image) is displayed in the display area 14 will be described with reference to FIG. FIG. 2 is a timing chart showing the operation of the television 1 when displaying a moving image in the display area 14.

When displaying a moving image, as shown in FIG. 2, the scanning line drive circuit 12 first starts supplying a scanning signal to the monitor scanning line m in the first field. When the supply of the scan signal to the monitor scan line m is completed, the scan line drive circuit 12 next starts the supply of the scan signal to the first scan line provided in the display area 14. Further, when the supply of the scan signal to the first scan line is completed, the supply of the scan signal to the second scan line is started. As described above, the scan signal is sequentially supplied to each of the scan lines up to the P-th row.

Further, while each scanning line is being scanned, the signal line driving circuit 13 supplies an image signal to each of the signal lines from the first column to the Q column.

When the supply of the scanning signal to the scanning line m and the scanning line of the P rows (hereinafter, also simply referred to as the scanning line of the P + 1 row) ends, the first field is completed. Next, in the second field, the scanning line drive circuit 12 sequentially supplies the scanning signal to the scanning line of P + 1 row again. As a result, the image is sequentially refreshed, and a moving image is displayed on the display area 14.

In the present embodiment, the case where the scanning line drive circuit 12 supplies a scanning signal to the monitor scanning line m when displaying a normal moving image has been described as an example. It is not limited to this. For example, when displaying a normal moving image, the scanning line drive circuit 12 may adopt a configuration in which a scanning signal is not supplied to the monitor scanning line m.

(Display of still image)
Next, the case of displaying a still image in the display area 14 will be described with reference to FIG. FIG. 3 is a timing chart showing the operation of the television 1 when displaying a still image in the display area 14.

When displaying a still image, as shown in FIG. 3, the scanning line drive circuit 12 supplies a scanning signal to the scanning line m for monitor in the first field, and further, each of the first to Pth rows. The scan signal is sequentially supplied to the scan line. Further, while each scanning line is being scanned, the signal line driving circuit 13 supplies an image signal to each of the signal lines from the first column to the Q column.

The scanning line drive circuit 12 stops the supply of the scanning signal when the supply of the scanning signal to all the scanning lines in the (P + 1) th row is completed. The signal line drive circuit 13 stops the supply of the image signal when the supply of the image signal to each signal line is completed while the scanning line of the Pth row is being scanned.

When the monitor determination signal is input from the comparator 15, that is, when the absolute value of the monitor voltage becomes equal to or less than the absolute value of the threshold, the control unit 11 causes the scan line drive circuit 12 and the signal line drive circuit 13 to refresh signals. To notify. When the monitor determination signal is input to the control unit 11, the first field ends and the second field starts.

When the refresh signal is notified in the second field, the scan line drive circuit 12 and the signal line drive circuit 13 resume the supply of the scan signal to the scan line and the supply of the image signal to the signal line, and the image is refreshed. Be done.

According to the above configuration, when displaying a still image and a moving image with little change in the image, the television 1 does not refresh the image until the monitor voltage becomes lower than the threshold due to the leak current, thereby reducing the number of refreshes. Can. Thus, the television 1 can reduce the power consumed for the refresh. Further, the television 1 can reduce the number of times the scanning signal is supplied to the TFTs 141 included in the respective pixels by reducing the number of times of refreshment, and can minimize the deterioration of the characteristics of the respective TFTs 141.

Therefore, the television 1 can control the timing of the image refresh according to the temperature change in each pixel, the variation in the leak current of each TFT, the deterioration of the characteristics, and the like.

(Setting the refresh rate for still image display)
Next, when displaying a still image in the display area 14, the figure illustrates the case where the leak time, which is the decay time of the monitor voltage, is measured from when the refresh is started at a certain time until the monitor voltage becomes lower than the threshold voltage. This will be described with reference to FIG. FIG. 4 is a timing chart showing the operation of the television 1 for measuring the leak time when displaying a still image in the display area 14.

When displaying a still image, as shown in FIG. 3, the scanning line drive circuit 12 supplies a scanning signal to the scanning line m for monitor in the first field, and further, each of the first to Pth rows. The scan signal is sequentially supplied to the scan line. Further, while each scanning line is being scanned, the signal line driving circuit 13 supplies an image signal to each of the signal lines from the first column to the Q column.

The scanning line drive circuit 12 stops the supply of the scanning signal when the supply of the scanning signal to all the scanning lines in the (P + 1) th row is completed. The signal line drive circuit 13 stops the supply of the image signal when the supply of the image signal to each signal line is completed while the scanning line of the Pth row is being scanned.

When the monitor determination signal is input from the comparator 15, that is, when the absolute value of the monitor voltage becomes equal to or less than the absolute value of the threshold, the control unit 11 refreshes the scanning line drive circuit 12 and the signal line drive circuit 13. Signal a signal.

When notified of the refresh signal, the scanning line driving circuit 12 and the signal line driving circuit 13 resume the supply of the scanning signal to the scanning line and the supply of the image signal to the signal line, and the image is refreshed. When the monitor determination signal is input to the control unit 11, the first field ends and the second field starts.

Further, from the time when supply of the scan signal to monitor scan line m is started, control unit 11 ends the supply of the scan signal to all the scan lines of P + 1 row, and monitor determination signal is input from comparator 15. The leak time taken to be measured is measured using a clock signal. The control unit 11 sets the measured leak time as a refresh rate when displaying a still image in the display area 14.

That is, after the second field, the control unit 11 controls the scanning line drive circuit 12 and the signal line drive circuit 13 to refresh the image based on the refresh rate set according to the leak time measured in the first field. . According to the above configuration, the television 1 can set the optimal refresh rate according to the change of the monitor voltage by measuring the leak time once.

The control unit 11 may adopt a configuration in which the leak time is repeatedly measured, and the refresh rate is reset each time the leak time is measured. According to this, the television 1 can always set the optimal refresh rate according to the change of the monitor voltage.

(Change of scanning signal in display of still image)
Next, referring to FIG. 5, the case where the scan voltage and supply time of the scan signal (that is, the scan time of the scan line) are changed based on the leak time when displaying the still image in the display area 14 will be described. . FIG. 5 is a timing chart showing the operation of the television 1 for changing the scanning voltage and the supply time based on the leak time when displaying a still image in the display area 14.

The control unit 11 first measures the leak time as described above, and sets the measured leak time as a refresh rate when displaying a still image in the display area 14.

Next, the control unit 11 changes the scan voltage (amplitude) and the supply time (pulse width) based on the set refresh rate. For example, as shown in FIG. 5, the control unit 11 may set the scanning voltage low. In this case, in order to obtain an on voltage for turning on each of the TFTs 141 and the monitoring TFT 151, the voltage of the image signal supplied via the signal line can be sufficiently set for each of the pixel electrodes 142 and the monitoring pixel electrode. In order to charge 152, the scan signal supply time may be set long. As shown in FIG. 5, the length of the scan signal supply time needs to be set within a range where the supply of scan signals to all the scan lines of P + 1 rows is completed during one field period (one cycle of the refresh rate). There is.

According to the above-described configuration, when displaying a still image and a moving image with little change in the image, the number of times a high voltage is applied to each TFT 141 can be reduced, so that deterioration of the characteristics of each TFT 141 can be minimized. It can be suppressed.

Further, the control unit 11 may set the voltage of the scanning signal high. In this case, since the on voltage and the voltage of the image signal can be sufficiently obtained, the supply time of the scanning signal can be set long.

Note that, as described above, the control unit 11 may reset the refresh rate every predetermined period. In this case, the control unit 11 can optimally reset the scan voltage and the supply time for each predetermined period in accordance with the reset refresh rate. Thus, when displaying a still image and a moving image with little change in image, the television 1 changes the temperature of each TFT 141 and the characteristic of each TFT 141 at the time of operation of the television 1 due to the deterioration of the characteristic. The scan voltage and supply time can be properly reset each time the refresh rate is reset to correspond to the dynamic change.

(Multiple fields make up one frame)
Next, a case where one frame is configured by a plurality of fields when displaying a still image in the display area 14 will be described with reference to FIG. FIG. 6 is a timing chart showing an operation of the television 1 in which one frame is constituted by a plurality of fields when displaying a still image in the display area 14.

Note that in order to form one frame by a plurality of fields, the non-display area is provided with monitor scanning lines and monitor pixels corresponding to the same number of fields as the number of fields constituting one frame. Is preferred. In the present embodiment, when one frame is configured by two fields, the case where two monitor scanning lines m1 and monitor scanning lines m2 are provided will be described as an example.

When displaying a still image, as shown in FIG. 6, the scanning line driving circuit 12 first supplies a scanning signal to the monitoring scanning line m1 in the first field. Furthermore, the scanning line driving circuit 12 sequentially supplies scanning signals to the scanning lines in the odd-numbered rows from the scanning line in the first row to the scanning line in the P−1th row provided in the display area 14. The signal line drive circuit 13 supplies an image signal to each signal line from the first column to the Q-th column while the monitor scanning line m1 and each scanning line in the odd-numbered row are scanned.

The scanning line driving circuit 12 stops the supply of the scanning signal when the supply of the scanning signal to the scanning lines in the odd rows provided in the monitor scanning line m1 and the display area 14 is finished. In addition, when the supply of the image signal to each signal line is completed while the scanning line of the Pth row is scanned, the signal line drive circuit 13 stops the supply of the image signal to each signal line.

The scanning line driving circuit 12 supplies a scanning signal to the monitoring scanning line m2 in the second field, and further, an even number from the second scanning line provided in the display area 14 to the Pth scanning line. A scan signal is sequentially supplied to each scan line of the row. The signal line drive circuit 13 supplies an image signal to each signal line from the first column to the Qth column while the monitor scanning line m2 and each scanning line in the even row are scanned.

The scanning line driving circuit 12 stops the supply of the scanning signal when the supply of the scanning signal to each scanning line of the even-numbered rows provided in the monitor scanning line m2 and the display area 14 is finished. In addition, when the supply of the image signal to each signal line is completed while the scanning line of the Pth row is scanned, the signal line drive circuit 13 stops the supply of the image signal to each signal line. As a result, one image (one frame) is displayed in the display area 14.

In addition, when the monitor determination signal is input from the comparator 15 in any of the first field and the second field, the control unit 11 determines that the absolute value of the monitor voltage is less than or equal to the absolute value of the threshold. In this case, the refresh signal is notified to the scanning line drive circuit 12 and the signal line drive circuit 13.

The scanning line drive circuit 12 and the signal line drive circuit 13 start refreshing the still image when notified of the refresh signal. Specifically, when the refresh signal is notified in the first field, the scanning line driving circuit 12 and the signal line driving circuit 13 interrupt the first field, and do not execute the second field in the current frame. , Start the first field in the next frame. Further, when the refresh signal is notified in the second field, the scanning line driving circuit 12 and the signal line driving circuit 13 interrupt the second field and start the first field in the next frame.

Thus, when one frame is constituted by a plurality of fields, when the absolute value of the monitor voltage in any field becomes lower than the absolute value of the threshold, the operation in the current frame is interrupted and the refresh is started (that is, the next frame Start the operation in

Further, in the present embodiment, the scanning line scanned in each field is described as an example in which the scanning line is switched for every row (even and odd rows), but the present invention is not limited to this. Absent. For example, a configuration may be adopted in which scanning lines scanned in each field are switched for every n (n is a natural number) rows. For example, in the case of n = 2, the scan lines in the first and second rows may be scanned in the first frame, and the scan lines in the third and fourth rows may be scanned in the second frame. In addition, in the case of n = 1, it becomes the structure mentioned above.

Furthermore, it is preferable to determine the value of n in accordance with the number of scanning lines to which the scanning signal is inverted for each scanning signal supplied. For example, it is preferable that n = 1 if the polarity of the scanning signal is inverted every row, and it is preferable that n = 2 if the polarity of the scanning signal is inverted every two rows.

In the present embodiment, the scanning line driving circuit 12 has been described by way of an example in which the scanning line scanning in the first field and the scanning line scanning in the second field are alternately performed. The invention is not limited to this. For example, the scanning line drive circuit 12 may be independent of the scanning of the scanning line in the first field and the scanning of the scanning line in the second field. In this case, the scanning line driving circuit 12 detects the scanning line in the second field before the monitor determination signal is input to the control unit 11 in the first field (or before the period of one field indicated by the refresh rate elapses). The scan of may be started.

If a monitor determination signal is input to the control unit 11 in the first field (or if a period of one field indicated by the refresh rate has elapsed), before the monitor determination signal is input to the control unit 11 in the second field ( Alternatively, before the period of one field indicated by the refresh rate elapses, scanning of the scan line in the first field in the next frame (that is, the field in which the same scan line as the scan line scanned in the first field is scanned) Should be started.

According to the above configuration, since the scanning signal supplied to the scanning line has the same polarity in each field, the television 1 supplies the scanning signal in which the polarity is inverted every n scanning lines in one field. Power consumption can be reduced compared to the case.

Further, according to the above-described configuration, when displaying still images and moving images with little change in image, the television 1 displays an image until each monitor voltage falls below the threshold due to leakage current in each field constituting one frame. Do not refresh Thereby, the television 1 can reduce the number of refreshes in each field. For this reason, the television 1 can reduce the power consumed for the refresh, and can reduce the number of times the scanning signal is supplied to each TFT 141, so that the deterioration of the characteristics of each TFT 141 is minimized. Can be reduced to

(Drive by area)
Further, the control unit 11 may measure the leak time of the plurality of monitor TFTs 151 as in the measurement of the leak time described above. At this time, the control unit 11 divides the display area 14 into a plurality of areas (sub display areas) based on each leak time. Furthermore, the control unit 11 controls the timing of the refresh according to the corresponding leak time for each of the divided areas.

According to the above-described configuration, the television 1 divides the display area 14 into a plurality of areas in accordance with the variation in the characteristics of the TFT 141 and the monitor TFT 151 caused by the location of the display panel 10 at the time of manufacture. The timing of refresh is controlled for each selected area. As a result, it is possible to individually refresh the image of only the area to which the monitor pixel having the monitor pixel electrode in which the absolute value of the monitor voltage is equal to or less than the threshold absolute value. Therefore, it is not necessary to refresh the image displayed on all the pixels provided in the display panel 10 even when the absolute value of the voltage of some of the monitor pixel electrodes becomes equal to or less than the absolute value of the threshold. Power consumption can be reduced.

In the present embodiment, the case where one comparator 15 is provided is described as an example, but the present invention is not limited to this, and for example, a plurality of comparators 15 are provided. It is also good. When a plurality of comparators 15 are provided, each comparator 15 compares the absolute value of the monitor voltages different from each other with the absolute value of the threshold voltage. In this case, the control unit 11 follows the monitor determination signal inputted from each comparator 15 at the earliest, that is, according to the change of the characteristic of the monitor TFT 151 at which the absolute value of the monitor voltage becomes the threshold voltage or less earlier. And the above-described operation may be controlled.

Further, in the present embodiment, the voltage of the monitor pixel electrode 152 is used as a change of the voltage of the pixel electrode 142 (so-called sample), and the pixel electrode 142 is controlled by controlling the image refresh timing according to the comparison result. And the timing of image refresh according to the characteristics of the TFT 141 can be controlled. As a result, the characteristics of the pixel electrode 142 and the TFT 141 are changed due to direct connection of the comparator 15 to directly compare the voltage of the pixel electrode 142 with the threshold voltage (ie, the displayed image is Change) can be prevented.

With the above-described configuration, the television 1 according to the present embodiment can control the timing of image refresh with high accuracy.

<Modification 1>
Next, a modification of this embodiment will be described with reference to FIG. In the television 1a according to the present modification, as shown in FIG. 7, on the opposite side of the non-display area of the display panel 10a to the signal line drive circuit 13 side, the monitor scan line m ′ in one row and the monitor scan The configuration is the same as that of the television 1 according to the first embodiment except that a plurality of monitor pixels (outside pixels) provided at the intersections of the line m ′ and the signal lines in the total number Q columns are provided.

Each monitor pixel is provided with a monitor pixel electrode 152a, which turns on / off the electrical connection between the monitor pixel electrode 152a and the signal line by the scanning signal supplied to the monitor scanning line m '. A monitor TFT (switching element) 151a is provided. The gate electrode of the monitor TFT 151a is connected to the monitor scan line m ', the source terminal is connected to the signal line, and the drain terminal is connected to the monitor pixel electrode 152a.

For convenience of explanation, among the three terminals included in the monitoring TFT 151a, for two terminals other than the gate terminal, the terminal connected to the signal line is referred to as a source terminal, and the terminal connected to the monitoring pixel electrode 152a It is called a drain terminal, but may be reversed.

In the operation of the television 1a in the case of displaying a still image in the present modification, after the scanning line provided in the display area 14 is scanned by the scanning line drive circuit 12, the monitor scanning line m 'is scanned. The other operations are the same as the operation of the television 1 in the first embodiment, and thus the description thereof is omitted here.

<Modification 2>
Next, another modification of the present embodiment will be described with reference to FIG. In the television 1b according to the present modification, as shown in FIG. 8, the monitor scanning line m is changed to one monitor signal line l on the opposite side to the scanning line drive circuit side of the non-display area of the display panel 10b. Embodiment 1 except for including the plurality of monitor pixels (out-of-area pixels) provided at the intersections of the monitor signal lines 1 and the scan lines of the total number P of rows. The same configuration as the television 1 according to.

Each monitor pixel is provided with a monitor pixel electrode 152b, which turns on / off the electrical connection between the monitor pixel electrode 152b and the monitor signal line 1 by the scanning signal supplied to each scanning line. A monitor TFT (switching element) 151 b is provided. The gate electrode of the monitor TFT 151b is connected to the scanning line, the source terminal is connected to the monitor signal line 1, and the drain terminal is connected to the monitor pixel electrode 152b.

For convenience of explanation, among the three terminals of the monitor TFT 151b, among the three terminals other than the gate terminal, the terminal connected to the monitor signal line l is called a source terminal and is connected to the monitor pixel electrode 152b. The other terminal is called a drain terminal, but may be reversed.

[Operation of TV]
Next, an operation of displaying a still image on the display area 14 of the television 1b according to the present modification will be described.

(Display of still image)
When displaying a still image, the scanning line drive circuit 12 sequentially supplies a scanning signal to each of the scanning lines from the first row to the Pth row in the first field. At this time, while each scanning line is being scanned, the signal line driving circuit 13 supplies an image signal to each of the signal lines from the first column to the Qth column and the monitoring signal line l.

The scanning line drive circuit 12 stops the supply of the scanning signal when the supply of the scanning signal to all the scanning lines of the P rows is finished. Further, the signal line drive circuit 13 stops the supply of the image signal when the supply of the image signal to the signal lines of all the Q columns and the monitor signal line 1 is completed while the scanning line of the Pth row is scanned. .

When the monitor determination signal is input from the comparator 15, that is, when the absolute value of the monitor voltage becomes equal to or less than the absolute value of the threshold, the control unit 11 causes the scan line drive circuit 12 and the signal line drive circuit 13 to refresh signals. To notify. When the monitor determination signal is input to the control unit 11, the first field ends and the second field starts.

When the refresh signal is notified in the second field, the scan line drive circuit 12 and the signal line drive circuit 13 resume the supply of the scan signal to the scan line and the supply of the image signal to the signal line, and the image is refreshed. Be done.

According to the above configuration, when displaying a still image and a moving image with little change in the image, the television 1b does not refresh the image until the monitor voltage becomes lower than the threshold due to the leak current, thereby reducing the number of refreshes. Can. Therefore, the television 1b can reduce the power consumed for the refresh. Further, by reducing the number of refreshes, the television 1 b can reduce the number of times the scan signal is supplied to the TFTs 141 included in the respective pixels, and can minimize the deterioration of the characteristics of the respective TFTs 141.

Therefore, the television 1 b can control the timing of the image refresh according to the temperature change in each pixel, the variation in the leak current of each TFT, the deterioration of the characteristics, and the like.

(Setting the refresh rate for still image display)
The control unit 11 ends the supply of the scan signals to the scan lines of all the P rows from the time when the supply of the scan signals to the scan line of the first row is started, and the monitor determination signal is input from the comparator 15 The leak time taken by the clock is measured using a clock signal. The control unit 11 sets the measured leak time as a refresh rate when displaying a still image.

That is, after the second field, the control unit 11 controls the scanning line drive circuit 12 and the signal line drive circuit 13 to refresh the image based on the refresh rate set according to the leak time measured in the first field. . Control unit 11 adopts a configuration for controlling scanning line drive circuit 12 and signal line drive circuit 13 in accordance with the refresh rate set according to the leak time measured in the first field in all the fields after the second field. It is also good. Further, the control unit 11 may adopt a configuration in which the refresh rate is reset every predetermined period by measuring the leak time every predetermined period.

(Change of scanning signal in display of still image)
Further, the control unit 11 changes the scan voltage (amplitude) and the supply time (pulse width) based on the refresh rate set as described above. For example, the control unit 11 may set the scanning voltage low. In this case, in order to obtain an on voltage for turning on each TFT 141, the voltage of the image signal supplied via each signal line and the monitoring signal line 1 is sufficiently set to each pixel electrode 142 and the monitor. In order to charge the pixel electrode 152b, the supply time of the scan signal may be set long. The length of the scan signal supply time needs to be set within a range in which the supply of scan signals to all the scan lines of P rows is completed within one field period.

According to the above-described configuration, when displaying a still image and a moving image with little change in the image, the number of times a high voltage is applied to each TFT 141 can be reduced, so that deterioration of the characteristics of each TFT 141 can be minimized. It can be suppressed.

Further, the control unit 11 may set the voltage of the scanning signal high. In this case, since the on voltage and the voltage of the image signal can be sufficiently obtained, the supply time of the scanning signal can be set long.

Note that, as described above, the control unit 11 may reset the refresh rate every predetermined period. In this case, the control unit 11 can optimally reset the scan voltage and the supply time for each predetermined period in accordance with the reset refresh rate. As a result, when displaying a still image and a moving image with little change in the image, the television 1 b may change the temperature of each TFT 141 and the characteristic of each TFT 141 during the operation of the television 1 b due to the deterioration of the characteristic. The scan voltage and supply time can be properly reset each time the refresh rate is reset to correspond to the dynamic change.

(Multiple fields make up one frame)
In addition, when displaying a still image in the display area 14, the case where one frame is configured by a plurality of fields will be described. When one frame is constituted by a plurality of fields, at least as many comparators 15 as the number of fields constituting one frame are provided one by one to the monitor pixel electrode 152b corresponding to the scanning line scanned in each field. It is preferable that it is connected.

In the case of displaying a still image, the scanning line driving circuit 12 first supplies scanning signals sequentially to the scanning lines in the odd lines from the scanning line of the first line to the scanning line in the P-1 line in the first field. Do. Further, while each scanning line in the odd-numbered rows is scanned, the signal line driving circuit 13 displays the image on each of the signal lines from the first column to the Q-th column provided in the monitoring signal line 1 and the display area 14. Provide a signal.

The scanning line driving circuit 12 stops the supply of the scanning signal when the supply of the scanning signal to each scanning line of the odd-numbered rows provided in the display area 14 is finished. In addition, when the supply of the image signal to each signal line is completed while the scanning line of the Pth row is scanned, the signal line drive circuit 13 stops the supply of the image signal to each signal line.

The scanning line driving circuit 12 and the signal line driving circuit 13 operate in the same manner as the first field except that the scanning line driving circuit 12 sequentially scans each even line in the second field. As a result, one image (one frame) is displayed in the display area 14.

In addition, when the monitor determination signal is input from the comparator 15 in any of the first field and the second field, the control unit 11 determines that the absolute value of the monitor voltage is less than or equal to the absolute value of the threshold. In this case, the refresh signal is notified to the scanning line drive circuit 12 and the signal line drive circuit 13.

When a frame is constituted by a plurality of fields, when the refresh signal is notified (that is, the absolute value of the monitor voltage becomes smaller than the absolute value of the threshold in any field), the operation in the current frame is interrupted and the next The operation in the frame is started. The operation of the television 1b notified of the notification of the refresh signal is the same as the operation of the television 1 according to the first embodiment, and thus the description thereof is omitted here.

According to the above-described configuration, when displaying a still image and a moving image with little change in image, the television 1 refreshes the image until each monitor voltage falls below the threshold due to leakage current in each field constituting one frame. do not do. Thereby, the television 1 can reduce the number of refreshes in each field. For this reason, the television 1 can reduce the power consumed for the refresh, and can reduce the number of times the scanning signal is supplied to each TFT 141, so that the deterioration of the characteristics of each TFT 141 is minimized. Can be reduced to

<Modification 3>
Next, still another modified example of the present embodiment will be described with reference to FIG. As shown in FIG. 9, the television 1c according to the present modification is provided with one monitoring signal line l 'on the scanning line drive circuit side of the non-display area of the display panel 10c instead of the monitoring scanning line m. In Embodiment 1 except that the first embodiment has a plurality of monitor pixels (outside pixels) provided at the intersections of the monitor signal lines l ′ and the total number of P scanning lines. It has the same configuration as the related television 1.

Each monitor pixel is provided with a monitor pixel electrode 152c, and the electrical connection between the monitor pixel electrode 152c and the monitor signal line l 'is turned on / off by a scanning signal supplied to each scanning line. And a monitoring TFT (switching element) 151c. The gate electrode of the monitor TFT 151c is connected to the scanning line, the source terminal is connected to the monitor signal line 1, and the drain terminal is connected to the monitor pixel electrode 152c.

For convenience of explanation, among the three terminals of the monitor TFT 151c, among the three terminals other than the gate terminal, the terminal connected to the monitor signal line l 'is referred to as a source terminal and connected to the monitor pixel electrode 152c. These terminals are called drain terminals, but may be reversed.

The operation of the television 1 c in the case of displaying a still image in this modification is the same as the operation of the television 1 b in the second embodiment, and thus the description thereof is omitted here.

Second Embodiment
Another embodiment of the present invention will be described below with reference to FIGS. 10 to 12. The television 2 according to the present embodiment is provided with a comparator 25 formed on the display panel 20 as shown in FIG. 12 instead of the comparator 15 provided outside the display panel 10. The configuration is the same as that of the television 1 described in the first embodiment except for the above. FIG. 12 is a diagram showing an outline of the overall configuration of the television 2 according to the present embodiment.

(Circuit configuration of comparator)
Here, the comparator 25 according to the present embodiment will be described with reference to FIG. FIG. 10 is a circuit diagram showing a configuration of the comparator 25 provided in the television 2 according to the present embodiment.

As shown in FIG. 10, the comparator (comparator circuit) 25 includes a power supply V1 (reference voltage power supply), V2 (ground), control signal input terminals S1 to S3 (first control signal input node to third control signal). Input node), monitor voltage input terminal (voltage input node) I, output terminal (output node) O, transistors T1 to T6 (first to sixth transistors), resistor R1 (first resistor), R2 A second resistor) and a capacitor C are provided. In the present embodiment, the power supply V2 may be, for example, a GND (ground) terminal.

The monitor voltage input terminal I is connected to the source terminal of the transistor T1. The gate terminal of the transistor T1 is connected to the control signal input terminal S1, and the drain terminal is connected to one end Net1 of the capacitor C. The other end Net2 of the capacitor C is connected to the source terminal of the transistor T2, the source terminal gate terminal of the transistor T2 is connected to the control signal input terminal S1, and the drain terminal is connected to the terminal Net3 (intermediate node) ing.

The gate terminal of the transistor T3 is connected to the control signal input terminal S2, the source terminal is connected to the terminal Net3, and the drain terminal is connected to the output terminal O. The gate terminal of the transistor T5 is connected to the control signal input terminal S3, the source terminal is connected to the terminal Net3, and the drain terminal is connected to the power supply V2.

The gate terminal of the transistor T6 is connected to the control signal input terminal S2, the source terminal is connected to the power supply V1, and the drain terminal is connected to one end of the resistor R1. The other end of the resistor R1 is connected to the output terminal O.

One end of the resistor R2 is connected to the power supply V1, and the other end is connected to the output terminal O. The gate terminal of the transistor T4 is connected to the terminal Net3, the source terminal is connected to the output terminal O, and the drain terminal is connected to the power supply V2.

The transistors T4 and T6 and the resistors R1 and R2 constitute an inverter circuit, and the terminal Net3 can be regarded as an input terminal of the inverter circuit.

Further, in the present embodiment, the case where all the transistors T1 to T6 are Nch TFTs (thin film transistors) will be described as an example, but the present invention is not limited to this.

Further, in the present embodiment, the control signal input terminals S1 to S3 and the output terminal O are connected to the control unit 11, and the power supplies V1 and V2 are connected to a power supply circuit (not shown) included in the television 1. The monitor voltage input terminal I may be connected to the monitor pixel electrode 152.

(Operation of comparator)
Next, the operation of the comparator 25 will be described with reference to FIG. FIG. 11 is a timing chart showing the operation of the comparator 25 provided in the television 2 according to the present embodiment.

The voltage of the output terminal O at time before time t1 is a voltage of H level as shown in FIG. 11, and specifically, it is dropped by a voltage amount applied to the resistor R2 from the voltage applied to the power supply V1. It is a voltage.

At time t1, as shown in FIG. 11, the scanning of the monitor scanning line m is started (the scanning voltage changes to the high level (H level)) and simultaneously input to the control signal input terminals S1 and S2. The control signals both transition to the H level. The transistors T1 and T2 are turned on by inputting the control signal of H level to the control signal input terminal S1. In addition, when the control signal of H level is input to the control signal input terminal S2, the transistors T3 and T6 are turned on.

When the transistor T3 transitions to the on state, the input terminal (that is, the terminal Net3) of the inverter circuit including the transistors T4 and T5 and the resistors R1 and R2 and the output terminal O are shorted. Therefore, as shown in FIG. 11, the input voltage of the inverter circuit (that is, the voltage of the terminal Net3) and the output voltage (that is, the voltage of the output terminal O) become equal to the threshold voltage A of the inverter circuit. Note that, since the transistor T6 is in the on state, (1) the on-resistance of the transistor T6, the resistor R1 connected in series to the transistor T6, and the resistor connected in parallel to the transistor T6 and the resistor R1 It is determined by the ratio of the combined resistance value of R2 and (2) the resistance value of the on resistance of the transistor T4.

Further, in the present embodiment, as shown in FIG. 11, the threshold voltage B is used as a threshold when determining whether or not the absolute value of the monitor voltage is equal to or less than the absolute value of a predetermined threshold after time t4. Specifically, when the voltage of Net3 is larger than the threshold voltage B, an output signal having an L level voltage is output from the output terminal O, and when the voltage of Net3 is equal to or lower than the threshold voltage B, an output An output signal having a voltage of H level is output from the terminal O.

At the time point t4 when the voltage input to the monitor voltage input terminal I is compared with the threshold voltage, the control signal input terminal S2 is at the L level, and the transistor T6 is in the off state. For this reason, the threshold voltage B is determined by the ratio of the resistance value of the on resistance of the transistor T4 to the resistance R2. Therefore, the difference between the threshold voltage A and the threshold voltage B is a value for determining the amount of change in the potential charged in the pixel electrode.

Also, since the transistors T1 and T2 are in the on state, the monitor voltage input from the monitor voltage input terminal I is applied to one end Net1 of the capacitor C, and the threshold voltage A of the terminal Net3 is applied to the other end Net2. Ru. As a result, a difference voltage between the monitor voltage and the threshold voltage A is applied to the capacitor C.

At time t2, simultaneously with the transition of the scanning voltage to the low level (L level), the control signals input to the control signal input terminals S1 and S2 both transition to the L level. When a control signal at L level is input to the control signal input terminals S1 and S2, the transistors T1 and T2 are turned off. When the transistors T1 and T2 are turned off, the capacitor C holds the difference voltage between the monitor voltage and the threshold voltage A.

At time t3, the control signal input to the control signal input terminal S3 transitions to the H level, and the transistor T5 is turned on. When the transistor T5 is turned on, the terminal Net3 and the power supply V2 are short-circuited, and the voltage of the terminal Net3 becomes the same L level (ground potential) as the power supply V2. Since the voltage of the terminal Net3 applied to the gate terminal of the transistor T4 is at the L level, it is possible to minimize the deterioration of characteristics due to the application of the voltage at the H level to the transistor T4.

In addition, when the voltage of the terminal Net3 applied to the gate terminal of the transistor T4 becomes L level, the transistor T4 is turned off, and the voltage of the output terminal O returns to the initial voltage before time t1. . Hereinafter, the operation of returning the voltage of the output terminal O to the initial voltage when the control signal of H level is input to the control signal input terminal S3 is also described as resetting the voltage of the output terminal O.

As shown in FIG. 11, the monitor voltage input to the monitor voltage input terminal I is attenuated by the leak current in the period from time t2 to t4.

At time t4, the control signal input to the control signal input terminal S1 transitions to the H level, and the transistors T1 and T2 are turned on. When the transistors T1 and T2 are turned on, the voltages at one end Net1 and the other end Net2 of the capacitor C decrease by the same value as the monitor voltage that has been attenuated during the period from time t2 to t4. As a result, the voltage at the terminal Net3 decreases by the same value as the value at which the monitor voltage is attenuated.

At time t5, the control signal input to the control signal input terminal S1 both transitions to L level, and the transistors T1 and T2 are turned off. When the transistors T1 and T2 are turned off, the capacitor C holds a voltage lowered by the same value as the monitor voltage attenuated in the period from time t2 to time t4 from the voltage held at time t2. become.

Note that, as shown in FIG. 11, in the period from time t4 to time t6, the voltage of the terminal Net3 is larger than the threshold voltage B, so the output terminal O is an output having a voltage of L level as an output of the comparator 25. Output a signal.

At time t6, the control signal input to the control signal input terminal S3 transitions to the H level, and the transistor T5 is turned on. When the transistor T5 is turned on, the terminal Net3 and the power supply V2 are short-circuited, and the voltage of the terminal Net3 becomes the same L level as the power supply V2.

Further, when the voltage of the terminal Net3 applied to the gate terminal of the transistor T4 becomes L level, the transistor T4 is turned off, and the voltage of the output terminal O is reset.

As shown in FIG. 11, the monitor voltage input to the monitor voltage input terminal I is attenuated by the leak current in the period from time t5 to t7.

At time t7, the control signal input to the control signal input terminal S1 transitions to the H level, and the transistors T1 and T2 are turned on. When the transistors T1 and T2 are turned on, the voltages at one end Net1 and the other end Net2 of the capacitor C decrease by the same value as the monitor voltage attenuated in the period from time t5 to t7, and the voltage at the terminal Net3 is also the same. Decrease by the value.

At time t8, both control signals input to the control signal input terminal S1 transition to L level, and the transistors T1 and T2 are turned off. When the transistors T1 and T2 are turned off, the capacitor C holds a voltage reduced by the same value as the monitor voltage attenuated in the period from time t4 to time t6 from the voltage held at time t5. become.

Note that, as shown in FIG. 11, in the period from time t7 to time t9, the voltage of the terminal Net3 is smaller than the threshold voltage B, so the output terminal O is an output having a voltage of H level as an output of the comparator 25. Output a signal.

At time t9, the control signal input to the control signal input terminal S3 transitions to the H level, and the transistor T5 is turned on. When the transistor T5 is turned on, the terminal Net3 and the power supply V2 are short-circuited, and the voltage of the terminal Net3 becomes the same L level as the power supply V2.

Further, when the voltage of the terminal Net3 applied to the gate terminal of the transistor T4 becomes L level, the transistor T4 is turned off, and the voltage of the output terminal O is reset.

Note that the control unit 11 according to the present embodiment performs scanning so as to refresh the displayed image when the output signal (that is, the monitor determination signal) having the H level voltage is input from the comparator 25. The line drive circuit 12 and the signal line drive circuit 13 may be controlled.

In addition, about operation | movement of the television 2 which concerns on this embodiment, since it is the same as operation | movement of the television 1 which concerns on Embodiment 1, description is abbreviate | omitted here.

Further, by configuring the comparator 25 as described above, it is possible to realize a circuit in which the drive voltage is not continuously applied to each of the transistors T1 to T6 included in the comparator 25 for a long time. Thereby, the comparator 25 can be formed on the display panel 20 realized by, for example, a glass substrate.

(Characteristics of TFT using oxide semiconductor)
In Embodiments 1 and 2, a TFT using a so-called oxide semiconductor can be employed as the TFT 141, the monitoring TFT 151, and the transistors T1 to T6.

Since the TFT using an oxide semiconductor has about 20 to 50 times higher electron mobility in the on state than the TFT using a-Si, and the on property is very excellent, the frame period is 16 It is also easy to set the refresh rate to 60 Hz or less.

The display panels 10 and 20 according to the first and second embodiments can drive pixels with smaller TFTs by adopting a TFT using an oxide semiconductor having such excellent on-state characteristics for each pixel. it can. Thus, the display panels 10 and 20 can reduce the ratio of the area occupied by the TFT in each pixel. That is, the aperture ratio in each pixel can be increased, and the transmittance of backlight can be increased. As a result, a backlight with low power consumption can be adopted, and the luminance of the backlight can be suppressed, whereby power consumption can be reduced.

In addition, since the on-characteristics of the TFTs are excellent, the writing time of the source signal to each pixel can be further shortened, so that the frame period of the display panels 10 and 20 can be easily shortened (that is, the refresh rate Can be easily raised).

In addition, a TFT using an oxide semiconductor has a leakage current of about 100 times smaller than that of a TFT using a-Si, and almost no leakage current occurs, and the off characteristic is very excellent. It is a thing. As described above, since the off characteristic is very excellent, it is also easy to set the frame period to 33 ms or more, that is, to set the refresh rate to 30 Hz or less.

The display panels 10 and 20 according to the first and second embodiments employ a TFT using an oxide semiconductor having such excellent off characteristics for each pixel, whereby the display panels 10 and 20 have a plurality of pixels. Since the state in which each source signal is written can be maintained for a long time, the frame period of the display panels 10 and 20 can be easily extended (that is, the refresh rate can be easily lowered).

In addition, even if it is TFT using such an oxide semiconductor, since a leak current arises not a little, deterioration of TFT is further minimized by using comparator 25 provided with the circuit concerning this embodiment. be able to.

[Summary]
The liquid crystal display device (televisions 1 and 2) according to one aspect of the present invention includes a plurality of in-region pixels (pixels) disposed in the display region 14 for displaying an image, as described above, A display panel 10, 20 having at least one outside pixel (monitoring pixel) disposed outside, and a scanning signal supply circuit (scanning line for supplying a scanning signal to the inside pixel and the outside pixel) A drive circuit 12), an image signal supply circuit (signal line drive circuit 13) for supplying an image signal to each pixel electrode provided in the in-region pixel and the out-of-region pixel, the scan signal supply circuit and the image signal supply And a control circuit (11) for controlling the circuit, the liquid crystal display further comprising a comparison circuit (comparator 15, 25) for comparing the voltage of the pixel electrode of the outside pixel with a predetermined threshold. control 11, according to the comparison result by the comparator circuit controls the timing of the image refresh is characterized by.

According to the above configuration, the control unit 11 controls the timing of image refresh according to the comparison result.

Here, the voltage of the pixel electrode of the out-of-area pixel is provided to the out-of-area pixel, and the electrical connection between the image signal line for supplying the image signal according to the scanning signal and the pixel electrode Is attenuated by the leak current of the TFT (thin film transistor) that turns on and off. Further, the leak current of the TFT is changed due to the temperature change of the TFT due to the driving of the pixel outside the area, the dispersion of the characteristic at the time of manufacturing the TFT, the deterioration of the characteristic of the TFT by continuing use, and the like.

Therefore, the liquid crystal display device can control the timing of image refresh in the control unit 11 according to the comparison result (that is, the change in voltage of the pixel electrode due to the leak current of the TFT). Thus, the liquid crystal display device can control the timing of image refresh with high accuracy.

The voltage of the pixel electrode included in the out-of-region pixel is used as a change of the voltage of the pixel electrode included in the in-region pixel (so-called sample), and the timing of image refresh is controlled according to the comparison result. The timing of image refresh can be controlled in accordance with the characteristics of the pixel electrode and the TFT included in the in-area pixel. As a result, the characteristics of the pixel electrode provided in the in-area pixel change due to the connection of the comparison circuit to directly compare the voltage of the pixel electrode provided in the in-area pixel with the threshold voltage. It is possible to prevent (that is, changing the displayed image).

In addition, in the liquid crystal display device according to one aspect of the present invention, the control unit 11 refreshes the image when the absolute value of the voltage of the pixel electrode of the out-of-area pixel becomes equal to or less than the absolute value of the threshold. Preferably.

According to the above configuration, the control unit 11 does not start the image refresh when the absolute value of the voltage of the pixel electrode is larger than the absolute value of the threshold. According to this, for example, when the image displayed in the display area 14 is not an image that requires constant refreshing (for example, when the image is a still image), the number of times of refreshing can be reduced.

Therefore, the liquid crystal display device can reduce the power consumed for refreshing the image. Further, since the liquid crystal display device can reduce the number of times the scanning signal is supplied to the pixels in each area by reducing the number of times of refresh, deterioration of the characteristics of the TFTs provided in the pixels in each area can be minimized. It can be suppressed.

In the liquid crystal display device according to one aspect of the present invention, the display panels 10 and 20 include a plurality of out-of-region pixels, and the control unit 11 calculates the absolute value of the voltage of the pixel electrode of each out-of-region pixel. Preferably, the image is refreshed when the absolute value of the lowest voltage falls below the absolute value of the threshold.

According to the above configuration, the control unit 11 controls the refresh of the image based on the absolute value of the lowest voltage among the absolute values of the voltages of the pixel electrodes. Thus, the liquid crystal display device can control the image refresh based on the voltage of the pixel electrode of the out-of-area pixel having the TFT with the largest leak current.

Further, as the size of the display panels 10 and 20 increases, the variation in the characteristics of the TFTs of the out-of-area pixels generated increases depending on where the display panels 10 and 20 are formed at the time of manufacture. Therefore, the liquid crystal display device can control the timing of refreshing the image with higher accuracy even if the variation of the characteristics of each TFT is large.

Further, in the liquid crystal display device according to one aspect of the present invention, the absolute value of the voltage of the pixel electrode of each pixel outside each region is equal to or less than the absolute value of the threshold from the time when the control unit 11 starts refreshing the image. It is preferable to measure the decay time until and set the refresh rate of the image based on each decay time.

According to the above configuration, the liquid crystal display device can set the optimal refresh rate according to the change of the voltage of the pixel electrode by measuring the decay time at least once. Of course, it is possible to repeatedly measure the decay time and reset the refresh rate each time the decay time is measured. According to this, the liquid crystal display device can always set the optimal refresh rate according to the change of the voltage of the pixel electrode.

Further, in the liquid crystal display device according to one aspect of the present invention, the control unit 11 divides the display area 14 into a plurality of sub display areas (areas) based on each attenuation time, and for each of the sub display areas. Preferably, the timing of the refresh is controlled.

According to the above configuration, even if the liquid crystal display device has variations in the characteristics of the TFTs provided in the out-of-region pixels depending on where in the display panels 10 and 20 the liquid crystal display device is manufactured, the variations Thus, the display area 14 is divided into a plurality of sub display areas, and the refresh timing is controlled for each of the divided sub display areas. Thus, it is possible to refresh the image of only the sub display area to which the outside pixel having the pixel electrode whose absolute value of the voltage is equal to or less than the absolute value of the threshold value. Therefore, even when the absolute value of the voltage of the pixel electrode of some of the out-of-area pixels becomes equal to or less than the absolute value of the threshold value, the image displayed on all the pixels of the display panels 10 and 20 is refreshed. Therefore, the power consumed in the refresh can be reduced.

Further, in the liquid crystal display device (television 2) according to an aspect of the present invention, the comparison circuit (comparator 25) is formed on the display panel 20, and a voltage input node (monitor voltage input terminal I A first transistor (transistor T1) having a source connected to the drain, a drain connected to one end Net1 of the capacitor C, and a gate connected to a first control signal input node (control signal input terminal S1) A second transistor (a transistor having a source connected to the other end Net2 of the capacitor C, a drain connected to the intermediate node (terminal Net3), and a gate connected to the first control signal input node T2), a source connected to the intermediate node, a drain connected to the output node (output terminal O), and a second control signal A third transistor (transistor T3) having a gate connected to the input node (control signal input terminal S2), a source connected to the output node, a drain connected to ground, and a gate connected to the intermediate node A fourth transistor (transistor T4), a source connected to the intermediate node, a drain connected to ground, and a gate connected to a third control signal input node (control signal input terminal S3) A transistor 5 (transistor T5), a source connected to the reference voltage power supply (power supply V1), a drain connected to the other end of the first resistor (resistor R1) whose one end is connected to the output node, A sixth transistor (transistor T6) having a gate connected to the second control signal input node, and the reference voltage A second resistor (resistor R2) whose one end is connected to the source and the other end is connected to the output node, and the voltage of the pixel electrode of the out-of-area pixel is input to the voltage input node; Preferably, an output voltage indicating the comparison result is output from the output node.

According to the above configuration, since the comparison circuit including the above-described elements is formed on the display panel 20, the liquid crystal display device is configured as compared with the case where the comparison circuit is provided other than on the display panel 10. The number of parts can be reduced.

In the liquid crystal display device according to one aspect of the present invention, each of the plurality of in-region pixels and the at least one out-of-region pixel preferably includes a TFT having an oxide semiconductor as a semiconductor layer.

According to the above configuration, in the display device, the refresh rate is changed by adopting a TFT having a semiconductor layer that is an oxide semiconductor having excellent on and off characteristics with respect to in-region pixels and out-region pixels. It will be easier to

In the liquid crystal display device according to one aspect of the present invention, as described above, a plurality of in-region pixels arranged in the display region for displaying an image and at least one region arranged outside the display region A display panel having an outer pixel, a scan signal supply circuit for supplying a scan signal to the in-region pixel and the out-of-region pixel, and pixel electrodes of the in-region pixel and the out-of-region pixel The image signal supply circuit that supplies an image signal, the control unit 11 that controls the scan signal supply circuit and the image signal supply circuit, the voltage of the pixel electrode of the out-of-region pixel and the predetermined threshold voltage are compared The display panel 10 or 20 includes a plurality of the out-of-region pixels, and the control unit 11 controls the timing of the image refresh according to the comparison result by the comparison circuit. The image is refreshed and the image is refreshed when the absolute value of the lowest voltage among the absolute values of the voltages of the pixel electrodes included in each of the out-of-area pixels becomes equal to or less than the absolute value of the threshold voltage. The decay time until the absolute value of the voltage of the pixel electrode of each out-of-area pixel becomes equal to or less than the absolute value of the threshold voltage is measured from the time when the above is started, and the refresh rate of the image is set based on each decay time. To be characterized.

According to the above configuration, the control unit 11 can control the timing of the image refresh with high accuracy according to the comparison result. Further, the liquid crystal display device can control the refresh of the image based on the voltage of the pixel electrode of the out-of-area pixel having the TFT with the largest leakage current. Furthermore, the liquid crystal display device can always set the optimal refresh rate according to the change of the voltage of the pixel electrode.

The comparison circuit (comparator 25) according to an aspect of the present invention is a comparison circuit formed on the display panel 20 of the liquid crystal display device (television 2) for comparing the input voltage with a predetermined threshold voltage, A first transistor having a source connected to the voltage input node, a drain connected to one end of the capacitor, and a gate connected to the first control signal input node, and the other end of the capacitor A second transistor having a source, a drain connected to an intermediate node, and a gate connected to the first control signal input node, a source connected to the intermediate node, a drain connected to an output node, And a third transistor having a gate connected to the second control signal input node, a source connected to the output node, and a drain connected to ground, A fourth transistor having a gate connected to the intermediate node, a source connected to the intermediate node, a drain connected to ground, and a gate having a gate connected to a third control signal input node , A source connected to a reference voltage power supply, a drain connected to the other end of the first resistor whose one end is connected to the output node, and a second control signal input node A sixth transistor having a gate, and a second resistor having one end connected to the reference voltage power supply and the other end connected to the output node, and an input voltage being input to the voltage input node; An output voltage indicating the comparison result is output from the output node.

By forming the comparison circuit as in the above configuration, a circuit in which a drive voltage is not continuously applied to each transistor forming the comparison circuit can be realized. Thus, the voltage comparator can be formed on the display panel 20 even if the display panel 20 included in the display device is made of, for example, a glass substrate. The comparison circuit is provided outside the display area 14 of the display panel 20 having a plurality of pixels.

A television receiver provided with the above-described playback device also falls within the scope of the present invention.

It should be understood that the embodiments disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is indicated not by the above description but by the scope of the claims, and is intended to include all modifications within the scope and meaning equivalent to the scope of the claims.

The display device according to the present invention can be suitably applied to a television receiver, a personal computer, a car navigation system, a mobile phone, a PDA, a smartphone, a tablet PC, a digital camera, a digital video camera, and the like.

1, 1a, 1b, 1c, 2 Television (Liquid Crystal Display)
10, 10a, 10b, 10c, 20 Display panel 11 Control unit 12 Scanning line drive circuit (scanning signal supply circuit)
13 Signal line drive circuit (image signal supply circuit)
14 Display area 15, 25 comparator (comparison circuit)
141 TFT
142 pixel electrode 151, 151a, 151b, 151c TFT for monitor
152, 152a, 152b, 152c Monitor pixel electrodes

Claims (10)

1. A display panel having a plurality of in-area pixels arranged in a display area for displaying an image, and at least one out-of-area pixels arranged outside the display area;
   A scanning signal supply circuit that supplies a scanning signal to the in-region pixels and the out-of-region pixels;
   An image signal supply circuit that supplies an image signal to each pixel electrode provided in the in-region pixel and the out-of-region pixel;
   A control unit that controls the scanning signal supply circuit and the image signal supply circuit;
   The circuit further includes a comparison circuit that compares the voltage of the pixel electrode of the out-of-area pixel with a predetermined threshold voltage,
   The control unit controls an image refresh timing according to the comparison result by the comparison circuit.
   A liquid crystal display device characterized by
2. The control unit refreshes the image when the absolute value of the voltage of the pixel electrode of the out-of-area pixel becomes equal to or less than the absolute value of the threshold voltage.
   The liquid crystal display device according to claim 1,
3. The display panel includes a plurality of out-of-region pixels,
   The control unit performs the image refresh when the absolute value of the lowest voltage among the absolute values of the voltages of the pixel electrodes of the pixels outside the respective regions becomes equal to or less than the absolute value of the threshold voltage. The liquid crystal display device according to claim 1 or 2, characterized in that
4. The control unit measures the decay time until the absolute value of the voltage of the pixel electrode of each out-of-area pixel becomes equal to or less than the absolute value of the threshold voltage from when the image refresh is started. Set the refresh rate of the above image,
   The liquid crystal display device according to any one of claims 1 to 3, characterized in that:
5. The control unit divides the display area into a plurality of sub display areas based on each decay time, and controls the timing of the refresh for each of the sub display areas.
   The liquid crystal display device according to claim 4,
6. The comparison circuit is formed on the display panel,
   A first transistor having a source connected to the voltage input node, a drain connected to one end of the capacitor, and a gate connected to the first control signal input node;
   A second transistor having a source connected to the other end of the capacitor, a drain connected to an intermediate node, and a gate connected to the first control signal input node;
   A third transistor having a source connected to the intermediate node, a drain connected to the output node, and a gate connected to a second control signal input node;
   A fourth transistor having a source connected to the output node, a drain connected to ground, and a gate connected to the intermediate node;
   A fifth transistor having a source connected to the intermediate node, a drain connected to ground, and a gate connected to a third control signal input node;
   A source connected to the reference voltage power supply, a drain connected to the other end of the first resistor connected to the output node at one end, and a gate connected to the second control signal input node With six transistors,
   A second resistor whose one end is connected to the reference voltage power supply and whose other end is connected to the output node,
   The voltage of the pixel electrode of the outside pixel is input to the voltage input node,
   An output voltage indicating the comparison result is output from the output node,
   The liquid crystal display device according to any one of claims 1 to 5, characterized in that:
7. Each of the plurality of in-region pixels and the at least one out-of-region pixel includes a TFT having an oxide semiconductor as a semiconductor layer.
   The liquid crystal display device according to any one of claims 1 to 6, characterized in that:
8. A display panel having a plurality of in-area pixels arranged in a display area for displaying an image, and at least one out-of-area pixels arranged outside the display area;
   A scanning signal supply circuit that supplies a scanning signal to the in-region pixels and the out-of-region pixels;
   An image signal supply circuit that supplies an image signal to each pixel electrode provided in the in-region pixel and the out-of-region pixel;
   A control unit that controls the scanning signal supply circuit and the image signal supply circuit;
   A comparison circuit that compares the voltage of the pixel electrode of the out-of-region pixel with a predetermined threshold voltage,
   The display panel includes a plurality of out-of-region pixels,
   The control unit
   Controlling the timing of image refresh according to the comparison result by the comparison circuit;
   The image is refreshed when the absolute value of the lowest voltage among the absolute values of the voltages of the pixel electrodes included in the pixels outside the respective regions becomes equal to or less than the absolute value of the threshold voltage,
   The decay time until the absolute value of the voltage of the pixel electrode of each out-of-area pixel falls below the absolute value of the threshold voltage from when the image refresh is started is measured, and the image is refreshed based on each decay time. Set the rate,
   A liquid crystal display device characterized by
9. A comparison circuit formed on a display panel of a liquid crystal display device for comparing an input voltage with a predetermined threshold voltage,
   A first transistor having a source connected to the voltage input node, a drain connected to one end of the capacitor, and a gate connected to the first control signal input node;
   A second transistor having a source connected to the other end of the capacitor, a drain connected to an intermediate node, and a gate connected to the first control signal input node;
   A third transistor having a source connected to the intermediate node, a drain connected to the output node, and a gate connected to a second control signal input node;
   A fourth transistor having a source connected to the output node, a drain connected to ground, and a gate connected to the intermediate node;
   A fifth transistor having a source connected to the intermediate node, a drain connected to ground, and a gate connected to a third control signal input node;
   A source connected to the reference voltage power supply, a drain connected to the other end of the first resistor connected to the output node at one end, and a gate connected to the second control signal input node With six transistors,
   A second resistor whose one end is connected to the reference voltage power supply and whose other end is connected to the output node,
   The input voltage is input to the voltage input node,
   An output voltage indicating a comparison result is output from the output node,
   A comparison circuit characterized by
10. A liquid crystal display device according to any one of claims 1 to 8, comprising:
    Television receiver characterized by

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