Display driver and display device

A display driver according to the present invention generates a plurality of driving voltages based on a video signal and applies the respective driving voltages to a plurality of source lines of a display panel. The display driver includes an overdrive part and an overdrive control circuit. The overdrive part executes an overdrive processing to increase amplitudes of the driving voltages. The overdrive control circuit detects an internal temperature of the display driver and stops the overdrive processing by the overdrive part when the temperature is higher than a predetermined temperature threshold.

BACKGROUND

1. Technical Field

The present invention relates to a display driver that generates a drive signal for driving a display panel on the basis of a video signal, and a display device that includes the display driver.

2. Related Art

A liquid crystal display device as a display device includes a liquid crystal display panel and a display driver that drives the liquid crystal display panel. The display driver generates a drive signal having a voltage value corresponding to a luminance indicated by a video signal and supplies the drive signal to the liquid crystal display panel. In the liquid crystal display panel, when the drive signal is received, voltage values of the drive signal are written to respective pixels, and lights are emitted from the pixels at the luminance levels corresponding to the written voltage values.

Recently, because of a reduced horizontal scanning period in accordance with a larger screen and higher definition of the liquid crystal display panel, high speed processing has been required for the display driver that drives the liquid crystal display panel.

That is, since the liquid crystal display panel has capacitances, a response time from the reception of the drive signal until each of the pixels reaches a state of the voltage value of the drive signal becomes relatively long. Accordingly, when the horizontal scanning period becomes short and the voltage value of the drive signal does not reach a desired voltage value in the horizontal scanning period, a display at the luminance level is no longer performed based on the video signal.

Therefore, recently, in a high definition liquid crystal display device, driving a liquid crystal display panel by a drive signal having a voltage value corresponding to a luminance higher (or lower) than a luminance indicated by a video signal, what is called an overdrive is employed, thereby seeking to improve the response speed.

As a liquid crystal display device that employs the overdrive, there has been proposed a liquid crystal display device that includes a temperature sensor for measuring a temperature of a liquid crystal display panel outside the liquid crystal display device to adjust an overdrive amount on the basis of the temperature of the liquid crystal display panel (for example, see JP-A-2019-40036). The overdrive disclosed in JP-A-2019-40036 is focused on the response speed of the liquid crystal increased when the temperature of the liquid crystal display panel is high, and the overdrive amount is decreased as the temperature of the liquid crystal display panel increases, thereby homogenize the response speed regardless of the temperature of the liquid crystal display panel.

SUMMARY

As the above-described amount of the overdrive is increased, that is, an amplitude of the drive signal is increased, the response speed of the display driver can be increased.

However, as the overdrive amount is increased, an electric power consumed by the display driver increases, thus causing heat generation of the display driver. When the display driver continues to operate in the high temperature state, there is an increased possibility that the display driver does not normally operate, and a problem arises in that an image degradation occurs.

Therefore, it is an object of the present invention to provide a display driver that allows a high-speed response process while reducing an image degradation due to heat generation, and a display device that includes the display driver.

A display driver according to the present invention is a display driver that receives a video signal, generates a plurality of driving voltages based on the video signal, and applies the respective driving voltages to a plurality of source lines of a display panel. The display driver includes an overdrive part and an overdrive control circuit. The overdrive part performs an overdrive processing to increase respective amplitudes of the plurality of driving voltages. The overdrive control circuit detects an internal temperature of the display driver and stops the overdrive processing by the overdrive part when the temperature is higher than a predetermined temperature threshold.

A display device according to the present invention includes a display panel, a timing control part, and a driver IC. The display panel includes a plurality of source lines on each of which a plurality of pixels is formed. The timing control part receives a video signal, generates a plurality of pixel data pieces that indicate luminance levels of respective pixels based on the video signal, and outputs a series of pixel data pieces in which an overdrive processing is performed on each of the pixel data pieces. The luminance levels indicated by the pixel data pieces are increased or decreased in the overdrive processing. The driver IC generates a plurality of driving voltages having respective voltage values corresponding to the luminance levels indicated by the respective pixel data pieces based on the series of the pixel data pieces output from the timing control part and applies the plurality of driving voltages to the plurality of source lines of the display panel. The driver IC includes an overdrive control circuit that detects an internal temperature of the driver IC and stops the overdrive processing by the timing control part when the temperature is higher than a predetermined temperature threshold.

In the present invention, the display driver generates the driving voltages based on the video signal and applies the driving voltages to the source lines of the display panel. To the display driver, its internal temperature is detected, and when the temperature becomes higher than a predetermined temperature threshold, the overdrive processing to increase the amplitude of the driving voltage is stopped. Accordingly, the overdrive processing to increase the response speed of the display driver can be executed while reducing the temperature of the display driver to the predetermined temperature threshold or less.

According to the present invention, the response speed of the display driver can be increased while suppressing the image degradation due to the heat generation of the display driver.

DETAILED DESCRIPTION

The following describes embodiments of the present invention in detail with reference to the drawings.

FIG.1is a drawing illustrating an exemplary schematic configuration of a display device100as an exemplary display device that includes a display driver according to the present invention. As illustrated inFIG.1, the display device100includes a timing control part11, a gate driver12, a source driver13, and a display panel20.

The display panel20includes a capacitive image display panel, such as a liquid crystal or organic EL panel. The display panel20includes m (m is an integer of 2 or more) gate lines G1to Gm each extending in a horizontal direction of a two-dimensional screen and n (n is an integer of 2 or more) source lines S1to Sn each extending in a vertical direction of the two-dimensional screen. Display cells that serve as pixels are formed at respective intersecting portions of the gate lines and the source lines.

The timing control part11receives a video signal VS, extracts a horizontal synchronization signal from the video signal VS, and supplies the horizontal synchronization signal to the gate driver12. The timing control part11generates a series of pixel data pieces that indicates luminance levels of the respective pixels by, for example, 8-bit data based on the video signal VS.

The timing control part11includes an overdrive (ODR) part that executes, for example, an overdrive processing described below to the pixel data pieces.

First, the ODR part calculates an overdrive amount corresponding to a change amount of a luminance level indicated by each pixel data piece for each of a pair of pixel data pieces that corresponds to a pair of pixels mutually adjacent in the vertical direction of the two-dimensional screen.

Next, the ODR part adds or subtracts the above-described overdrive amount to or from a later pixel data piece of the pair of pixel data pieces in one horizontal scanning period. That is, when the luminance indicated by the later pixel data piece of the pair of pixel data pieces is larger than the luminance indicated by the prior pixel data piece, the ODR part adds the overdrive amount corresponding to the luminance change amount between both pixel data pieces to the later pixel data piece. When the luminance indicated by the later pixel data piece is equal to or less than the luminance indicated by the prior pixel data piece, the ODR part subtracts the overdrive amount corresponding to the change amount between both pixel data pieces from the later pixel data piece.

Thus, the ODR part performs the overdrive processing in which the overdrive amount is added to or subtracted from the pixel data piece for each pair of pixels mutually adjacent in the vertical direction of the two-dimensional screen. The overdrive amount has a magnitude corresponding to the luminance change amount between the pair of pixel data pieces that correspond to the pair of pixels. This overdrive processing increases the response speed of the source driver.

The timing control part11generates a series of pixel data PD in which the respective pixel data pieces to which the overdrive processing has been performed are arranged in a predetermined order.

When at least one of temperature abnormality signals Qa, Qb, Qc, Qd, and Qe supplied from the source driver13indicates a temperature abnormality presence, the timing control part11does not perform the overdrive processing to the pixel data piece group corresponding to that temperature abnormality signal. That is, the timing control part11includes the pixel data piece corresponding to the video signal VS as it is into the series of the pixel data PD as the pixel data PD.

Furthermore, the timing control part11generates a reference timing signal that indicates a reference timing for generating a clock signal, and a load signal indicating a fetch start timing of the pixel data.

The timing control part11supplies the source driver13with an image data signal PDS in which the reference timing signal and the load signal are included in the series of the pixel data PD.

The gate driver12generates a gate pulse in synchronization with the horizontal synchronization signal supplied from the timing control part11, and sequentially applies the gate pulse to each of the gate lines G1to Gm of the display panel20.

The source driver13generates driving voltages having voltage values corresponding to the luminance levels indicated by respective pieces of the pixel data PD in the image data signal PDS and applies the driving voltages to the source lines S1to Sn of the display panel20.

The source driver13includes five driver ICs3ato3ethat are each an independent semiconductor Integrated Circuit (IC) chip. The driver IC3adrives the source lines S1to Sk (k is an integer of 2 or more) among the source lines S1to Sn of the display panel20. The driver IC3bdrives the source lines Sk+1 to Sr (r is an integer of 2 or more). The driver IC3cdrives the source lines Sr+1 to Sy (y is an integer of 2 or more). The driver IC3ddrives the source lines Sy+1 to Sj (j is an integer of 2 or more). The driver IC3edrives the source lines Sj+1 to Sn. The driver ICs3ato3eeach include the same circuit.

The driver ICs3ato3eeach receive the image data signal PDS and fetches the pixel data PD group corresponding to itself from the image data signal PDS in response to the load signal included in the image data signal PDS. Then, the driver ICs3ato3egenerate respective driving voltage groups corresponding to the luminance levels indicated by respective pieces of the fetched pixel data PD and apply the driving voltage groups to the respective corresponding source line groups.

For example, the driver IC3afetches k pieces of the pixel data PD corresponding to the first row to the k-th row of the display panel20from the image data signal PDS. Then, the driver IC3agenerates the driving voltages X1to Xk corresponding to the luminance levels indicated by the respective k pieces of the pixel data PD and applies the driving voltages X1to Xk to the source lines S1to Sk of the display panel20, respectively. The driver IC3bfetches (r-k) pieces of the pixel data PD corresponding to the k+1-th row to the r-th row of the display panel20from the image data signal PDS. Then, the driver IC3bgenerates the driving voltages Xk+1 to Xr corresponding to the luminance levels indicated by the respective (r-k) pieces of the pixel data PD and applies the driving voltages Xk+1 to Xr to the source lines Sk+1 to Sr of the display panel20, respectively. The driver IC3cfetches (y-r) pieces of the pixel data PD corresponding to the r+l-th row to the y-th row of the display panel20from the image data signal PDS. Then, the driver IC3cgenerates the driving voltages Xr+1 to Xy corresponding to the luminance levels indicated by the respective (y-r) pieces of the pixel data PD and applies the driving voltages Xr+1 to Xy to the source lines Sr+1 to Sy of the display panel20, respectively. The driver IC3dfetches (j-y) pieces of the pixel data PD corresponding to the y+1-th row to the j-th row of the display panel20from the image data signal PDS. Then, the driver IC3dgenerates the driving voltages Xy+1 to Xj corresponding to the luminance levels indicated by the respective (j-y) pieces of the pixel data PD and applies the driving voltages Xy+1 to Xj to the source lines Sy+1 to Sj of the display panel20, respectively. The driver IC3efetches (n-j) pieces of the pixel data PD corresponding to the j+1-th row to the n-th row of the display panel20from the image data signal PDS. Then, the driver IC3egenerates the driving voltages Xj+1 to Xn corresponding to the luminance levels indicated by the respective (n-j) pieces of the pixel data PD and applies the driving voltages Xj+1 to Xn to the source lines Sj+1 to Sn of the display panel20, respectively.

Furthermore, the driver IC3aoutputs the temperature abnormality signal Qa, the driver IC3boutputs the temperature abnormality signal Qb, the driver IC3coutputs the temperature abnormality signal Qc, the driver IC3doutputs the temperature abnormality signal Qd, and the driver IC3eoutputs the temperature abnormality signal Qe.

The following describes the configurations of the driver ICs3ato3e.

As described above, the driver ICs3ato3eeach include the same circuit. The following describes the circuit formed in each driver IC by extracting the driver IC3a.

FIG.2is a block diagram illustrating an exemplary circuit formed in the driver IC3a. As illustrated inFIG.2, the driver IC3aincludes a receiving part130, a data fetch part131, a data latch part132, a gradation voltage conversion circuit133, an output amplifier part134, a temperature detection circuit140, a comparator141, and a threshold register142.

The receiving part130extracts the load signal LD and the series of the pixel data PD from the image data signal PDS and supplies each of them to the data fetch part131. Furthermore, the receiving part130generates a clock signal CK having a cycle of one horizontal scanning period on the basis of the reference timing signal included in the image data signal PDS and supplies the clock signal CK to the data latch part132.

The data fetch part131fetches the pixel data PD corresponding to itself (in the example ofFIG.2, the driver IC3a) from the series of the pixel data PD by k pieces for each in response to the load signal LD. Then, the data fetch part131supplies the fetched k pieces of the pixel data PD to the data latch part132as the pixel data P1to Pk.

The data latch part132latches the pixel data P1to Pk at a timing correspond to the clock signal CK and supplies them to the gradation voltage conversion circuit133as pixel data R1to Rk, respectively.

The gradation voltage conversion circuit133converts the luminance levels indicated by the respective pixel data R1to Rk into gradation voltages V1to Vk having corresponding voltage values, respectively, and supplies the gradation voltages V1to Vk to the output amplifier part134.

The output amplifier part134amplifies each of the gradation voltages V1to Vk as required, and outputs them as the driving voltages X1to Xk. The driving voltages X1to Xk output from the output amplifier part134of the driver IC3aare applied to the source lines S1to Sk of the display panel20, respectively. The driving voltages X1to Xk output from the output amplifier part134of the driver IC3bare applied to the source lines Sk+1 to Sr of the display panel20, respectively. The driving voltages X1to Xk output from the output amplifier part134of the driver IC3care applied to the source lines Sr+1 to Sy of the display panel20, respectively.

The temperature detection circuit140detects the internal temperature of the driver IC3a(3bto3e) as the semiconductor chip, especially, the temperature of the output amplifier part134or the temperature around the output amplifier part134and supplies a temperature signal TD indicating the detected temperature to the comparator141.

The threshold register142is a register configured to hold a temperature threshold indicating the maximum limit temperature allowable as the temperature of the driver IC3a, and any given value is held as the temperature threshold after the manufacture of the driver IC3a. The threshold register142supplies a temperature threshold TH, which is held in itself and indicates the temperature threshold, to the comparator141.

The comparator141compares the temperature threshold TH with the temperature indicated by the temperature signal TD, and outputs a temperature abnormality signal indicative of no temperature abnormality when the temperature signal TD is the temperature threshold TH or less. When the temperature indicated by the temperature signal TD is higher than the temperature threshold TH, the comparator141outputs a temperature abnormality signal indicative of temperature abnormality presence. For the temperature threshold, a unique value can be set for each driver IC by the threshold register142of each of the driver ICs3ato3e.

As the above-described temperature abnormality signal, the comparator141of the driver IC3aoutputs the temperature abnormality signal Qa, the comparator141of the driver IC3boutputs the temperature abnormality signal Qb, and the comparator141of the driver IC3coutputs the temperature abnormality signal Qc. Similarly, as the temperature abnormality signal, the comparator141of the driver IC3doutputs the temperature abnormality signal Qd, and the comparator141of the driver IC3eoutputs the temperature abnormality signal Qe.

That is, the driver ICs3ato3eas the source drivers each include overdrive control circuits (140to142) that detect the internal temperature of the driver IC and generate the temperature abnormality signal (Qa to Qe) based on the temperature. The temperature abnormality signals Qa to Qe respectively generated by the overdrive control circuits (140to142) in the driver ICs3ato3eare supplied to the timing control part11.

The following describes an overdrive control.

First, when the internal temperatures of the driver ICs3ato3eare each equal to or less than the predetermined temperature threshold TH, the driver ICs3ato3esupply the temperature abnormality signals Qa to Qe indicative of no temperature abnormality to the timing control part11. The timing control part11having received the temperature abnormality signals Qa to Qe indicative of no temperature abnormality performs the overdrive processing as described above to the series of the pixel data pieces indicating the luminance level of each pixel based on the video signal VS. This makes the change amount of the luminance level large in the series of the pixel data pieces to which the overdrive processing has been performed compared with the series of the pixel data pieces to which the overdrive processing has not been performed. Accordingly, the amplitudes of the driving voltages X1to Xk generated by the output amplifier part134increase, the response speeds of the driver ICs3ato3eincrease, and the temperatures of the output amplifier part134rise.

Here, when, for example, the temperature abnormality signal Qa among the temperature abnormality signals Qa to Qe transitions to a state of indicating the temperature abnormality presence, the timing control part11stops the overdrive processing to the series of the pixel data pieces corresponding to the driver IC3a. That is, the timing control part11stops the overdrive processing to the series of the pixel data pieces corresponding to the driver IC3awhen the internal temperature of the driver IC3abecomes higher than the temperature threshold TH. Meanwhile, the timing control part11continues the overdrive processing to the series of the pixel data pieces corresponding to each of the driver ICs3bto3e.

Accordingly, the amplitudes of the driving voltages X1to Xk generated by the output amplifier part134of the driver IC3adecrease, and in association with this, the temperature of the output amplifier part134decreases. Therefore, subsequently, when the internal temperature of the driver IC3abecomes the temperature threshold TH or less, the driver IC3atransitions the temperature abnormality signal Qa from the state of the temperature abnormality presence to the state of no temperature abnormality. Then, according to the temperature abnormality signal Qa indicative of no temperature abnormality, the timing control part11starts the overdrive processing to the series of the pixel data pieces corresponding to the driver IC3aagain.

According to the overdrive control, even when the internal temperatures of the respective driver ICs3ato3eas the source drivers increase, the internal temperatures can be decreased to the temperature near the predetermined temperature threshold. Accordingly, the present invention ensures the higher speed response by the overdrive while reducing the image degradation due to the heat generation of the source driver.

In the configuration illustrated inFIG.1andFIG.2, the temperature thresholds as the factor of determining whether to execute the overdrive or not can be individually set by the threshold registers142included in the respective driver ICs3ato3e.

For example, the temperature threshold held by the threshold register142of the driver IC3c, which displays the screen central region that requires the relatively high luminance, is set to be higher than the temperature thresholds of the other driver ICs (3a,3b,3d, and3e). This increases the execution frequency of the overdrive processing in the driver IC3c, thus providing the higher speed response compared with the other driver ICs. Accordingly, since the amplitudes of the driving voltages X1to Xk can be increased in the driver IC3ccompared with the other driver ICs, the display with high luminance can be achieved in the screen central region of the display panel20.

FIG.3is a drawing illustrating an exemplary schematic configuration of a display device200as another example of the display device that includes the display driver according to the present invention. In the display device200illustrated inFIG.3, the configuration is the same as that of the display device100illustrated inFIG.1except that a timing control part11A is employed instead of the timing control part11and a source driver13A is employed instead of the source driver13.

The following describes configurations mainly for the timing control part11A and driver ICs30ato30e.

The timing control part11A is one in which the function of performing the overdrive processing as described above is omitted from the timing control part11.

That is, the timing control part11A receives a video signal VS, extracts a horizontal synchronization signal from the video signal VS, and supplies the horizontal synchronization signal to the gate driver12.

The timing control part11A generates a pixel data piece that indicates the luminance of the pixel by 8-bit data or the like for each pixel based on the video signal VS, and generates a series of the pixel data PD in which each of the pixel data pieces are arranged in a predetermined order. Furthermore, the timing control part11A generates a reference timing signal that indicates a reference timing for generating a clock signal, and a load signal indicating a fetch start timing of the pixel data.

Then, the timing control part11A supplies the source driver13A with an image data signal PDS in which the reference timing signal and the load signal are included in the series of the pixel data PD.

Similarly to the source driver13, the source driver13A generates driving voltages having voltage values corresponding to the luminance levels indicated by respective pieces of the pixel data PD in the image data signal PDS, and applies the driving voltages to the source lines S1to Sn of the display panel20.

Note that, in the source driver13A, the driver ICs30ato30eare employed instead of the driver ICs3ato3eillustrated inFIG.1andFIG.2.

Similarly to the driver ICs3ato3e, the driver ICs30ato30eare each an independent semiconductor IC chip. Similarly to the driver ICs3ato3e, the driver ICs30ato30edrive the respective divided source line groups (S1to Sk, Sk+1 to Sr, Sr+1 to Sy, Sy+1 to Sj, and Sj+1 to Sn) obtained by dividing the source lines S1to Sn of the display panel20into five.

The driver ICs30ato30eeach include one output terminal to output the temperature signal indicating its internal temperature, and four input terminals to receive the temperature signals indicating the internal temperatures of the respective driver ICs other than itself.

Accordingly, for example, the driver IC30areceives temperature signals Tb to Te respectively output from the driver ICs30bto30evia the wiring, and outputs a temperature signal Ta indicating the internal temperature of itself. The driver IC30breceives the temperature signals Ta and Tc to Te respectively output from the driver ICs30aand30cto30evia the wiring, and outputs the temperature signal Tb indicating the internal temperature of itself. The driver IC30creceives the temperature signals Ta, Tb, Td, and Te respectively output from the driver ICs30a,30b,30d, and30evia the wiring, and outputs the temperature signal Tc indicating the internal temperature of itself. The driver IC30dreceives the temperature signals Ta to Tc, and Te respectively output from the driver ICs30ato30c, and30evia the wiring, and outputs the temperature signal Td indicating the internal temperature of itself. The driver IC30ereceives the temperature signals Ta to Td respectively output from the driver ICs30ato30dvia the wiring, and outputs the temperature signal Te indicating the internal temperature of itself.

The following describes the configurations of the driver ICs30ato30e.

As described above, the driver ICs30ato30eeach include the same circuit. The following describes the circuit formed in each driver IC by extracting the driver IC30a.

FIG.4is a block diagram illustrating an exemplary circuit formed in the driver IC30a. As illustrated inFIG.4, similarly to the driver IC3a, the driver IC30aincludes a receiving part130, a data fetch part131, a data latch part132, a gradation voltage conversion circuit133, and an output amplifier part134.

The driver IC30aemploys a temperature detection circuit150, an averaging circuit151, a comparator152, and a threshold register153instead of the temperature detection circuit140and the comparator141illustrated inFIG.2. Furthermore, the driver IC30aincludes an overdrive part160between the data latch part132and the gradation voltage conversion circuit133.

InFIG.4, the receiving part130extracts the load signal LD and the series of the pixel data PD from the image data signal PDS and supplies each of them to the data fetch part131. Furthermore, the receiving part130generates a clock signal CK having a cycle of one horizontal scanning period on the basis of the reference timing signal included in the image data signal PDS and supplies the clock signal CK to the data latch part132and the overdrive part160.

The data fetch part131fetches the pixel data PD corresponding to itself (in the example ofFIG.4, the driver IC30a) from the series of the pixel data PD by k pieces for each in response to the load signal LD. Then, the data fetch part131supplies the fetched k pieces of the pixel data PD to the data latch part132as the pixel data P1to Pk.

The data latch part132simultaneously latches the pixel data P1to Pk at a timing correspond to the clock signal CK and supplies them to the overdrive part160as pixel data R1to Rk, respectively.

The temperature detection circuit150detects the internal temperature of the driver IC30a, especially, the temperature of the output amplifier part134or the temperature around the output amplifier part134, and supplies a temperature signal TD indicating the detected temperature to the averaging circuit151. Furthermore, the temperature detection circuit150outputs the temperature signal TD to outside the driver IC30aas the temperature signal Ta indicating the internal temperature of the driver IC30a. Note that the temperature detection circuit150of the driver IC30b(or30cto30e) detects the internal temperature of the driver IC30b(or30cto30e). Then, the temperature detection circuit150of the driver IC30b(or30cto30e) supplies the temperature signal TD indicating the temperature to the averaging circuit151, and externally outputs the temperature signal TD as the temperature signal Tb (or Tc to Te) indicating the internal temperature of the driver IC30b(or30cto30e).

The averaging circuit151obtains an average of the temperatures indicated by the respective temperature signals Ta to Te, or a weighted average obtained by weighting predetermined weights to the respective temperature signals Ta to Te, and supplies an average temperature Tav indicating the average value or the weighted average value to the comparator152. When obtaining the weighted average, for example, the averaging circuit151increases the weighting to the temperature signal Tc from the driver IC30cthat displays the screen central region in which the image degradation is noticeable in the display image.

The threshold register153is a register configured to hold a temperature threshold indicating the maximum limit temperature allowable as the temperature of the driver IC30a, and any given value is held as the temperature threshold after the manufacture of the driver IC30a. The threshold register153supplies a temperature threshold TH, which is held in itself and indicates the temperature threshold, to the comparator152.

The comparator152compares the temperature threshold TH with the average temperature Tav, and supplies a temperature abnormality signal Qx indicative of no temperature abnormality to the overdrive part160when the average temperature Tav is equal to or less than the temperature threshold TH. On the other hand, when the average temperature Tav is higher than the temperature threshold TH, the comparator152supplies a temperature abnormality signal Qx indicative of the temperature abnormality presence to the overdrive part160. For the temperature threshold, a unique value can be set for each driver IC by the threshold register153of each of the driver ICs30ato30e.

Thus, the driver ICs30ato30eeach include the overdrive control circuits (150to153) that detect the internal temperature of the driver IC and control whether to execute the overdrive processing in the overdrive part160or not on the basis of the temperature.

When the temperature abnormality signal Qx indicates no temperature abnormality, the overdrive part160performs the overdrive processing to the pixel data R1to Rk supplied from the data latch part132, and supplies them to the gradation voltage conversion circuit133as pixel data Y1to Yk.

FIG.5is a circuit diagram illustrating an exemplary internal configuration of the overdrive part160.

As illustrated inFIG.5, the overdrive part160includes overdrive circuits OD1to ODk respectively disposed corresponding to the pixel data R1to Rk. The overdrive circuits OD1to ODk each have the same circuit configuration, and each include, for example, as illustrated inFIG.5, a delay element51, an overdrive amount calculation circuit52(hereinafter referred to as an ODV calculation circuit52), and an adder53.

The following describes the circuit configuration with an example of the overdrive circuit OD1.

The delay element51includes a D flip-flop and the like, and is configured to delay the pixel data R1(or R2to Rk) by one horizontal scanning period in accordance with the clock signal CK and supply it to the ODV calculation circuit52as immediately preceding pixel data HD.

When the temperature abnormality signal Qx indicates no temperature abnormality, the ODV calculation circuit52subtracts the luminance indicated by the immediately preceding pixel data HD from the luminance indicated by the pixel data R1, thereby obtaining the luminance change amount. The ODV calculation circuit52supplies an overdrive amount OD having the magnitude corresponding to the luminance change amount to the adder53. On the other hand, when the temperature abnormality signal Qx indicates the temperature abnormality presence, the ODV calculation circuit52supplies the overdrive amount OD indicating zero to the adder53.

The adder53outputs the pixel data piece indicating the luminance obtained by adding the overdrive amount OD as a luminance correction value to the luminance indicated by the pixel data R1as the pixel data Y1.

With this configuration, the overdrive circuit OD1performs the overdrive processing of adding the overdrive amount OD to the pixel data R1when the temperature abnormality signal Qx indicates no temperature abnormality.

That is, in the overdrive processing, first, the overdrive circuit OD1obtains the luminance change amount from the immediately preceding pixel data HD, that is, the pixel data R1one horizontal scanning period before the current pixel data R1, to the current pixel data R1. Then, the overdrive circuit OD1adds the overdrive amount OD having the magnitude corresponding to the luminance change amount to the current pixel data R1, and outputs the addition result as the pixel data Y1.

That is, when the luminance indicated by the pixel data R1is higher than the luminance indicated by the pixel data R1one horizontal scanning period before, the overdrive circuit OD1outputs the pixel data Y1obtained by increasing the luminance of the current pixel data R1by the amount corresponding to the luminance change amount. When the luminance indicated by the pixel data R1is equal to or less than the luminance indicated by the pixel data R1one horizontal scanning period before, the overdrive circuit OD1outputs the pixel data Y1obtained by decreasing the luminance of the current pixel data R1by the amount corresponding to the luminance change amount. When the luminance indicated by the pixel data R1is equal to the luminance indicated by the pixel data R1one horizontal scanning period before, the overdrive circuit OD1directly outputs the current pixel data R1as the pixel data Y1because the luminance change amount becomes zero.

When the temperature abnormality signal Qx indicates the temperature abnormality presence, the overdrive circuit OD1directly outputs the current pixel data R1as the pixel data Y1regardless of the above-described luminance change amount.

With the configuration illustrated inFIG.5, when the temperature abnormality signal Qx indicates no temperature abnormality, the overdrive part160supplies the pixel data R1to Rk to which the overdrive processing has been performed to the gradation voltage conversion circuit133as the pixel data Y1to Yk. On the other hand, when the temperature abnormality signal Qx indicates the temperature abnormality presence, the overdrive part160directly supplies the pixel data R1to Rk to the gradation voltage conversion circuit133as the pixel data Y1to Yk.

The gradation voltage conversion circuit133converts the luminance levels indicated by the respective pixel data Y1to Yk into gradation voltages V1to Vk having corresponding voltage values, respectively, and supplies the gradation voltages V1to Vk to the output amplifier part134.

The output amplifier part134amplifies each of the gradation voltages V1to Vk as required and outputs them as the driving voltages X1to Xk. The driving voltages X1to Xk output from the output amplifier part134of the driver IC30aare applied to the source lines S1to Sk of the display panel20, respectively. The driving voltages X1to Xk output from the output amplifier part134of the driver IC30bare applied to the source lines Sk+1 to Sr of the display panel20, respectively. The driving voltages X1to Xk output from the output amplifier part134of the driver IC30care applied to the source lines Sr+1 to Sy of the display panel20, respectively.

The following describes the overdrive control in the display device200illustrated inFIG.3toFIG.5.

First, when the average value or a weighted average value (Tav) of the respective internal temperatures (Ta to Te) of the driver ICs30ato30eas the source drivers is the temperature threshold TH or less, the comparator152illustrated inFIG.4supplies the temperature abnormality signal Qx indicative of no temperature abnormality to the overdrive part160. This causes the overdrive part160to perform the overdrive processing as described below.

That is, first, the overdrive part160calculates the overdrive amounts OD corresponding to the change amounts of the luminance levels between the pixel data R1to Rk supplied from the data latch part132and the pixel data R1to Rk supplied one horizontal scanning period before, respectively. Then, the overdrive part160adds or subtracts the overdrive amounts OD calculated for the respective pixel data R1to Rk to or from the pixel data R1to Rk, and supplies them to the gradation voltage conversion circuit133of the next stage as the pixel data Y1to Yk. Thus, the change amounts of the luminance levels at the pixel data Y1to Yk are increased compared with the pixel data R1to Rk. In accordance with this, the amplitudes of the driving voltages X1to Xk generated by the output amplifier part134increase, the response speeds of the driver ICs30ato30eincrease, and the temperature of the output amplifier part134rises.

When the average value or the weighted average value (Tav) of the internal temperatures (Ta to Te) of the respective driver ICs30ato30eas the source drivers become higher than the temperature threshold TH, the comparator152supplies the temperature abnormality signal Qx indicative of the temperature abnormality presence to the overdrive part160. Accordingly, the overdrive part160stops the above-described overdrive processing, and directly supplies the pixel data R1to Rk supplied from the data latch part132to the gradation voltage conversion circuit133as the pixel data Y1to Yk. Accordingly, the amplitudes of the driving voltages X1to Xk generated by the output amplifier part134decrease, thus decreasing the temperature of the output amplifier part134. Accordingly, subsequently, when the average value or the weighted average value of the internal temperatures of the driver ICs30ato30ebecomes the temperature threshold TH or less, the comparator152supplies the temperature abnormality signal Qx indicative of no temperature abnormality to the overdrive part160. Then, corresponding to the temperature abnormality signal Qx indicative of no temperature abnormality, the overdrive part160starts the overdrive processing again.

Therefore, according to the overdrive control, even when the internal temperatures of the respective driver ICs30ato30eas the source drivers increase, the internal temperatures can be decreased to the temperature near the predetermined temperature threshold. Accordingly, the present invention ensures the higher speed response by the overdrive while reducing the image degradation due to the heat generation of the source driver.

In the display device200illustrated inFIG.3toFIG.5, since the overdrive processing can be performed inside each of the driver ICs30ato30eas the source drivers, the timing control part11A without the overdrive function can be employed.

The display device200illustrated inFIG.3toFIG.5includes the overdrive control circuit that detects the internal temperature of the driver IC and control whether to execute the overdrive processing or not on the basis of the internal temperature together with the overdrive part160in each of the driver ICs30ato30e. In view of this, compared with the one that performs the overdrive processing by the timing control part11as the display device100illustrated inFIG.1andFIG.2, when the rapid temperature rise in the driver IC occurs, the temperature can be quickly decreased to the temperature near the predetermined temperature threshold.

In the example illustrated inFIG.1orFIG.3, while the timing control part11(11A) is disposed outside the source driver13, the timing control part11(11A) may be configured as a part of the driver.

In the overdrive part described in the embodiments, the overdrive processing as described above is performed on the pixel data PD, thereby increasing the amplitudes of the driving voltages X1to Xk. However, the configuration of the overdrive processing is not limited insofar as the amplitudes of the driving voltages X1to Xk are increased.

In short, it is only necessary to employ a display driver that includes an overdrive part and an overdrive control circuit described below as a display driver (for example,11,11A,13, and13A) that receives a video signal (VS), generates a plurality of driving voltages (for example, X1to Xk) based on the video signal, and applies the driving voltages to a plurality of source lines (for example, S1to Sk) of the display panel (20), respectively.

The overdrive part (for example,11,160) executes the overdrive processing to increase the respective amplitudes of the plurality of driving voltages. The overdrive control circuits (for example,140to142,150to153) detect the internal temperatures of the display drivers (for example,3ato3e,30ato30e), and stop the overdrive processing by the overdrive part when the temperature is higher than the predetermined temperature threshold (TH).

It is understood that the foregoing description and accompanying drawings set forth the preferred embodiments of the present invention at the present time. Various modifications, additions and alternative designs will, of course, become apparent to those skilled in the art in light of the foregoing teachings without departing from the spirit and scope of the disclosed invention. Thus, it should be appreciated that the present invention is not limited to the disclosed Examples but may be practiced within the full scope of the appended claims. This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2020-126396 filed on Jul. 27, 2020, the entire contents of which are incorporated herein by reference.