JP3338438B1 - Liquid crystal driving device and gradation display method - Google Patents

Abstract

An object of the present invention is to provide a novel liquid crystal driving device capable of driving liquid crystal at high speed and performing multi-gradation display. SOLUTION: In a unit driving period of the liquid crystal, a predetermined pattern of voltage is applied to the liquid crystal to drive the liquid crystal, and an integral value of a transmitted light amount of the liquid crystal at each time when each applied pattern is applied to the liquid crystal is considered. To set an application pattern corresponding to each gradation data. Thus, even when the liquid crystal is driven only by turning on and off the maximum voltage of the rated voltage, fine gradation display can be performed. As a result, the liquid crystal can be driven at a high speed, and a multi-gradation display can be performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a liquid crystal driving device and a gradation display method, and more particularly, to a liquid crystal driving device and a gradation display method of a new gradation display system.

[0002]

2. Description of the Related Art Conventionally, an active matrix type liquid crystal display device for performing multi-tone display has been known. The multi-gradation display is performed, for example, by selecting one reference voltage corresponding to gradation display data from among reference voltages for the number of display gradations by an analog switch and driving the liquid crystal display device with the selected reference voltage. Done.

FIG. 18 is a block diagram showing a conventional liquid crystal driving device for driving an active matrix type liquid crystal display device. In this liquid crystal driving device, the first latch 1, the second latch
Are provided for each vertical pixel line of the liquid crystal display device.

The first latch 1 reads 3-bit grayscale data D0 to D2 for designating eight grayscale levels for each vertical pixel line during one horizontal scanning period. That is, the gradation data D0 to D2 are latched by the first latch 1 and held for one horizontal scanning period.

[0005] The second latch 2 supplies the gradation data D0 to D2 held by the first latch 1 to the decoder 3 in the next one horizontal scanning period. The decoder 3 decodes the grayscale data D0 to D2 from the second latch 2 and outputs a decoded signal S
0 to S7 are output to the control terminals of the analog switches A0 to A7, respectively.

The analog switches A0 to A7 selectively output reference voltages V0 to V7 respectively supplied to input terminals in accordance with decoded signals S0 to S7. That is, one of the reference voltages V0 to V7 is selected by the decoded signals S0 to S7 and output as the liquid crystal drive voltage.

The reference voltages V0 to V7 correspond to gradation levels as shown in FIG. Therefore, a reference voltage based on the grayscale data is selected, and the reference voltage is output to the liquid crystal panel as an applied voltage, whereby an amount of light transmission corresponding to the applied voltage is obtained, thereby enabling grayscale display.

[0008]

However, the conventional liquid crystal driving device is not sufficient for driving the liquid crystal at high speed. In recent years, with the spread of the Internet,
There is an increasing need to rapidly transmit large amounts of data such as images, and it is necessary to realize multiple gradations. In particular, in order to display a moving image, high-speed driving of a liquid crystal and multi-gradation display are desired.

The present invention has been made in view of the above points, and provides a novel liquid crystal driving device and a gradation display method capable of driving a liquid crystal at high speed and performing multi-gradation display. The purpose is to:

[0010]

[Means for Solving the Problems]

[0011]

[0012]

[0013]

[0014]

[0015]

According to the liquid crystal driving device of the present invention , according to the applied voltage,
And a liquid crystal that controls the amount of light transmitted through the light-emitting section.
A plurality of on-offs different from each other with the same number of on-times
Voltage application pattern setting that can set the pattern application voltage
Means and the voltage application pattern setting means.
The voltage of one of the on-off patterns
And a voltage supply means for supplying the liquid crystal to the liquid crystal.
The amount of liquid crystal transmitted during the period
Is variably controlled according to.

According to this configuration, the gradation display is performed by changing the voltage application pattern to the liquid crystal within the unit light emission period of the LED, so that the conventional PWM (Puls
Compared with e.g. Width Modulation, etc., a delicate gradation display corresponding to the gradation data can be performed.

In the liquid crystal driving device according to the present invention, the voltage application
The turn-on / off pattern of the turn setting means
Set based on the integrated value of the amount of transmitted light during the light period
I do.

According to this configuration, since the voltage application pattern to the liquid crystal is set by associating the area obtained by integrating the amount of transmitted light during the LED light emission period with each gradation, the liquid crystal is driven with a constant applied voltage. However, it is possible to perform delicate gradation display as if the liquid crystal was driven by an analog voltage. In addition, since the gradation is expressed by the integrated value of the transmitted light amount of the liquid crystal which continuously changes, the conventional PWM (Pulse Widt
h Modulation) and the like, and a more delicate gradation display according to the gradation data can be performed.

In the liquid crystal driving device according to the present invention, the voltage application
The turn setting means sets the voltage application pattern with reference to a table in which the gradation and the on / off pattern are associated.

According to this configuration, it is possible to easily set the voltage application pattern according to the gradation in accordance with the performance of the liquid crystal to be driven.

The liquid crystal drive apparatus of the present invention, the table, when the voltage of the different on-off patterns respectively supplied to the liquid crystal over time to detect the amount of light transmitted through the liquid crystal which changes at each on-off patterns, detected transmission Emit light
Measuring the area by integrating a unit emission period of parts, the O gradation data by associating the said area and the gradation data
It is created by associating an on- off pattern .

According to this configuration, the table stores in advance the voltage application pattern for each gradation suitable for each liquid crystal, so that a voltage corresponding to the voltage application pattern stored in this table can be applied. Thus, it is possible to perform a gradation display that is very suitable for the input gradation data.

In the liquid crystal driving device according to the present invention, the voltage supply means does not supply an intermediate voltage between the maximum voltage and the minimum voltage to the liquid crystal, but supplies only the maximum voltage and the minimum voltage to the liquid crystal to obtain a gradation. Display it.

According to this configuration, the maximum voltage of the rated voltage
(For example, 5 [v]) and the minimum voltage (0 [v]) to drive the liquid crystal, the response speed of the liquid crystal is increased, and the transmitted light amount corresponding to the required gradation can be obtained in a short time. .
As a result, the liquid crystal can be driven at high speed.

The liquid crystal driving device of the present invention includes a temperature sensor provided near the liquid crystal and detecting a peripheral temperature of the liquid crystal.
The voltage application pattern setting means corrects the voltage application pattern according to the detection result of the temperature sensor.

According to this configuration, when the response speed of the liquid crystal decreases as the peripheral temperature of the liquid crystal decreases, the setting means corrects the voltage application time so as to increase the voltage application time accordingly, or Correct the applied pattern.
As a result, it is possible to always perform gradation display in accordance with the input gradation data regardless of the state of the liquid crystal.

The liquid crystal driving device of the present invention includes a luminance detecting means provided near the liquid crystal for detecting the luminance of the transmitted light of the liquid crystal, and the voltage application pattern setting means sets the voltage in accordance with the detection result of the luminance detecting means. The applied pattern was corrected.

[0029] According to this configuration, when the light emission of the LED decreases due to aging and the display brightness decreases,
Accordingly, the voltage application time is corrected so that the voltage application time becomes longer, or the voltage application pattern is corrected. As a result, irrespective of the aging of the LED or the like, the luminance balance is always good and a gradation display according to the input gradation data can be performed.

The liquid crystal driving device according to the present invention includes the liquid crystal driving device.
By causing the LEDs of R, G, and B to sequentially emit light, and changing the aperture ratio of the liquid crystal provided corresponding to the LEDs of the respective colors by a voltage applied to the liquid crystal ,
Field-sequential liquid crystal display for gradation display
Display device.

According to this configuration, since the gradation display is performed by changing the on / off pattern of the liquid crystal within the unit light emission period of the LED, the conventional PWM (Puls
Compared with e.g. Width Modulation, etc., a delicate gradation display corresponding to the gradation data can be performed. Also, by selecting the on / off pattern to be applied to the liquid crystal by associating the area obtained by integrating the transmitted light amount in the LED light emission period with each gradation, the liquid crystal can be driven by an analog voltage even if the liquid crystal is driven only by on / off. It is possible to perform delicate gradation display as if it were lit. That is, since the gradation is expressed by the integrated value of the transmitted light amount of the liquid crystal which continuously changes, a finer gradation display according to the gradation data can be further performed.

[0032]

[0033]

[0034]

[0035]

According to the gradation display method of the present invention, the unit emission of the light emitting section is performed.
As a voltage application pattern applied to the liquid crystal during the light period,
On-off putters that are different from each other even though they have the same number of on-times
And setting the voltage application pattern of emission, the voltage applied
Change the voltage of one of the on / off patterns of the pattern to gradation
Supplying to the liquid crystal according to the
The amount of transmitted light through the liquid crystal according to the on / off pattern.
Variable control.

[0037]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings.

(Embodiment 1) FIG. 1 is a block diagram showing a schematic configuration of a liquid crystal drive device according to Embodiment 1 of the present invention. The liquid crystal driving device 10 according to the first embodiment includes an application time control unit 102 that controls a voltage application time according to gradation data, and a reference table 101 that associates an application time (ON time) corresponding to the gradation. And the application time control unit 102
The constant voltage generated by the constant voltage generating circuit 105 according to the ON time control signal output from the
And a switch 103 for outputting 0.

As shown in FIG. 2, the reference table 101 is a table that associates the gradation level with the application time during which the switch is ON. Here, the gradation display of the liquid crystal driving device according to the present invention will be described with reference to FIGS.

FIG. 3 is a diagram showing the relationship between light transmittance and time, FIG. 4 is a diagram showing the relationship between applied voltage and time, and FIG. FIG. 4 is a diagram illustrating a relationship between an applied voltage and time.

When the liquid crystal responds and transmits light by applying a voltage to the liquid crystal, the liquid crystal exhibits a light transmittance as shown in FIG. In FIG. 3A, the time required for the light transmittance to change from 10% to 90% is τ _ON .

On the other hand, when the application of the voltage to the liquid crystal is stopped and the light is cut off, the light transmittance as shown in FIG. 3B is exhibited. In FIG. 3B, the time required for the light transmittance to change from 90% to 10% is τ _OFF .

As is clear from FIGS. 3A and 3B, τ _OFF is longer than τ _ON . This means that there is a difference between the time until the liquid crystal responds by applying the voltage and the light is transmitted, and the time until the voltage is stopped and the light is cut off.

In this case, the response speed τ of the liquid crystal
_ON is represented by kG ² / (V ² −V _th ² ), and the response speed τ _{OFF of the} liquid crystal is represented by k′G ² (k, k ′: constant, V:
Applied voltage, V _th : threshold voltage, G: cell gap).
As can be seen from this equation, the response speed of the liquid crystal differs between when the voltage is applied (τ _ON ) and when the voltage is not applied (τ _OFF ). For this reason, the ratio of the time change of the voltage differs between the voltage application and the voltage application stop, that is, the voltage application is asymmetric.

Therefore, as shown in FIG. 4, the time required for the liquid crystal to reach the applied voltage value (rise) differs between the case where an applied voltage of 2.5 V is applied and the case where an applied voltage of 5 V is applied. The time to reach the applied voltage value is shorter when 5 V is applied.

As described above, when a voltage is applied to the liquid crystal, the liquid crystal responds (opens) and transmits light. Therefore, when a voltage is continuously applied for a certain period of time, the liquid crystal continues to respond and becomes an open state during that time, and light continues to be transmitted. Therefore, the amount of transmitted light at that time can be considered as an integral value of the applied voltage at that time. That is, it can be considered that the shaded area in FIG. 4 indicates the amount of transmitted light. Specifically, the amount of transmitted light when the applied voltage is 5 V is the area indicated by the upward-sloping oblique line in FIG. 4, and the amount of transmitted light when the applied voltage is 2.5 V is the area indicated by the upward-sloping oblique line in FIG. It is.

In the gradation display in the conventional liquid crystal driving, a reference voltage such as 2.5 V or 5 V shown in FIG. 4 is set in advance, and the reference voltage is applied to the liquid crystal. As described above, when the transmitted light amount is considered as the total amount of the opening time, that is, the applied voltage × time (the area indicated by oblique lines in FIG. 4),
As shown in FIG. 5, it is possible to keep the applied voltage constant and control the application time (t0 to t7). In other words, in FIG. 5, by changing the application time,
The waveform from the rise to the fall changes, and the area in the waveform (applied voltage × time) changes accordingly. As a result, the transmitted light amounts are different, and a gray scale display can be realized.

In such a gray scale display, since the applied voltage can be kept constant, the applied state and the non-applied state can be controlled at timing, that is, digital control becomes possible. Digital control facilitates control. In addition, since the liquid crystal is driven at a relatively high applied voltage at which the response speed of the liquid crystal is high for all gradation levels, it is possible to reduce the liquid crystal driving time as a whole.

Next, the operation of the liquid crystal driving device having the above configuration will be described.

The gradation data representing the gradation level in the gradation display is input to the application time control unit 102 of the liquid crystal driving device 10. The grayscale data is represented by 3 bits for 8 grayscales, for example, and is set to grayscale levels 0 to 7.

Upon receiving the gradation data, the application time control unit 102 refers to the reference table 101 shown in FIG.
An application time (ON time) corresponding to the gradation data is set. Then, the application time control unit 102 outputs an ON time control signal to the switch 103 for the determined ON time. In this way, as shown in FIGS. 6A to 6C, gradation display is performed by digitally controlling the application time for a predetermined application voltage.

The switch 103 includes an application time control unit 102
The switch is turned ON in accordance with the ON time control signal from the controller to apply a voltage to the pixels of the LCD panel 20. That is, a signal voltage is supplied to the source electrode line according to the ON time control signal to drive the liquid crystal.

As described above, the liquid crystal driving device according to the present embodiment can perform multi-tone display by digital control. This facilitates control in multi-tone display. Further, in all gradation displays, time control is performed with a relatively high applied voltage that increases the response speed, so that the liquid crystal driving time as a whole can be reduced.
In addition, since the liquid crystal drive voltage is applied digitally by time control with a constant value, a D / A (digital / analog) converter normally required in a liquid crystal drive device becomes unnecessary.

(Embodiment 2) FIG. 7 is a block diagram showing a schematic configuration of a liquid crystal driving device according to Embodiment 2 of the present invention. The liquid crystal driving device according to the second embodiment includes an application time control unit 1 that controls a voltage application time according to gradation data.
02 and application pattern (ON pattern) corresponding to gradation
And a switch 103 for outputting a constant voltage generated by the constant voltage generation circuit 105 to the LCD panel 20 in accordance with the ON pattern control signal output from the application time control unit 102. ing.

As shown in FIG. 8, the pattern table 104 is a table that associates gradation levels with application patterns for turning on switches. As the application pattern, for example, a pattern in which a predetermined liquid crystal driving time is divided into a plurality of blocks and voltage application / non-voltage application is switched as shown in FIG. 9 can be considered.

When a voltage is applied to the liquid crystal, the rising and falling are asymmetric as shown in FIGS. 3A and 3B. Therefore, if this is utilized, as shown in FIG. 9, even if the voltage application time is the same, the pattern is different, so that the applied voltage × the voltage application unit (one block in the pattern of FIG. 9) The area of time will be different. As a result, Embodiment 1
A finer gradation display can be performed.

For example, as in conventional PWM control, LED
Instead of changing the voltage application time during the unit light emission period, the embodiment changes the voltage application pattern within the unit light emission period. Here, the unit light emission period of the LED is an LE provided for each liquid crystal.
A period from when D (light emitting diode) starts emitting light to when it stops.

By the way, in the case of this embodiment, display is performed by using the field sequential method, and the LED array is used as a backlight to blink at a high speed. That is, the unit light emitting period is a lighting period for one time of each LED array.

As described above, by changing the voltage application pattern within the unit light emission period of the LED, a much more delicate gradation display can be performed as compared with, for example, the conventional PWM control.

Next, the operation of the liquid crystal driving device having the above configuration will be described.

The gradation data representing the gradation level in the gradation display is input to the application time control unit 102 of the liquid crystal driving device 10. The grayscale data is represented by 4 bits for 16 grayscales, for example, and is set to grayscale levels 0 to 15.

When receiving the gradation data, the application time control unit 102 determines an application pattern (ON pattern) corresponding to the gradation data with reference to the pattern table 104 shown in FIG. Then, the application time control unit 102 outputs an ON pattern control signal to the switch 103 only for the determined ON pattern.

The switch 103 is connected to the application time control unit 102
Switch is turned on according to the ON pattern control signal from
N is set to apply a voltage to the pixels of the LCD panel 20. That is, a signal voltage is supplied to the source electrode line according to the ON pattern control signal to drive the liquid crystal.

As described above, the liquid crystal driving device according to the present embodiment can perform multi-tone display by digital control. This facilitates control in multi-tone display. Further, in all gradation displays, time control is performed with a relatively high applied voltage that increases the response speed, so that the liquid crystal driving time as a whole can be reduced.
In addition, since the liquid crystal drive voltage is applied digitally by time control with a constant value, a D / A (digital / analog) converter normally required in a liquid crystal drive device becomes unnecessary.

In the liquid crystal driving device according to the embodiment,
By utilizing the asymmetry of the rise and fall in the voltage application, the gradation is expressed by the combination of the voltage application units, so that it is possible to realize more gradation display.

Further, by changing the voltage application pattern within the unit light emitting period of the LED, delicate gradation display can be performed.

(Embodiment 3) In this embodiment, the area obtained by integrating the amount of transmitted light of the liquid crystal at each point in the LED emission period when the maximum voltage of the rated voltage of the liquid crystal is applied is considered. The voltage application time (or voltage application pattern) corresponding to each gradation data is set. Specifically, FIG.
As shown in (1), an area obtained by integrating the waveform of the amount of light transmitted through the liquid crystal when the driving voltage is applied during the LED emission period (the area of the hatched portion in the figure) is associated with each gradation.

That is, the liquid crystal is driven such that the area of the shaded portion in FIG. 10 increases as the input gradation data indicates a higher gradation. In practice, the applied voltage is set to be constant at the maximum voltage of the rated voltage of the liquid crystal. Therefore, by changing the voltage application time (or voltage application pattern), the area of the hatched portion is changed according to the gradation. . FIG. 10A shows how the amount of transmitted light of the liquid crystal changes over time when the applied voltage is turned on during a period from time t0 to time ta, and FIG. 5 shows how the amount of transmitted light of the liquid crystal changes with time when a voltage of? Specifically, FIG. 10B shows a case where the voltage of the application pattern # 3 in FIG. 9 is applied, and is a period from time t0 to time t2, and a time from time t3 to time t2.
4 shows a case where an ON voltage is applied during a period of 4 and a period from time t5 to time t6.

As described above, in the liquid crystal driving device according to the present embodiment, the voltage application time to the liquid crystal is set by associating the area obtained by integrating the amount of transmitted light in the LED light emission period with the gradation, thereby providing a constant applied voltage. Thus, even when the liquid crystal is driven, it is possible to perform a delicate gradation display as if the liquid crystal was driven by an analog voltage.

Further, by applying a voltage of an on / off pattern to the liquid crystal in consideration of the area of the amount of transmitted light during the LED light emission period, a more delicate gradation display according to the gradation data can be performed. That is, as is apparent from a comparison between FIG. 10A and FIG. 10B, when the voltage of the on / off pattern is applied (FIG. 10B), the area of the amount of transmitted light during the LED light emission period becomes finer. Since the selection can be made, more delicate gradation expression is possible. For example, 1
By setting on / off pattern of 0 bit, R, G, B
In each case, 1024 gradation expressions are possible.

Further, in this embodiment, the LED
A voltage in an on / off pattern is applied to the liquid crystal from a point in time that is a predetermined time before the point in time when light is emitted. As a result, a desired transmittance can be obtained from the start of light emission of the LED, so that the brightness of the display screen can be increased without increasing the output of the LED.

Such a liquid crystal driving device is described in Embodiment 1.
Reference table 10 of the liquid crystal drive device 10 described above
1 can be realized by creating it as described below. FIG.
Denotes an apparatus for creating the reference table 101, and stores a voltage application time (or voltage application pattern) associated with each gradation data in the reference table 101.

The reference table creation device inputs the gradation data to the application time setting circuit 201. Application time setting circuit 2
01 sets a plurality of application times (or a plurality of application patterns) for each gradation designated by the gradation data. That is, a plurality of application times are sequentially set for one gradation data from a short application time to a long application time. The application time (or application pattern) thus set is determined by the switch 2
02 on / off control signal.

The switch 202 has a constant voltage generation circuit 203
, A constant voltage (in this embodiment, the maximum rated voltage 5 [v]) is input, and this voltage is applied to the LCD panel 2 for the time set by the application time setting circuit 201.
0 is applied as a drive voltage to the liquid crystal.

The LCD panel 20 is provided with a luminance sensor 204, and the transmitted light amount of the liquid crystal obtained from the luminance sensor 204 is sent to the integration circuit 205. Integration circuit 20
5 obtains the area indicated by the hatched portion in FIG. 10 by integrating the amount of transmitted light during the LED light emission period, and sends this area to the gradation determination circuit 206. The gradation data is also input to the gradation judgment circuit 206. The gradation judgment circuit 206 compares each gradation with the integrated area, and sends a write control signal for permitting writing to the reference table 101 when an area corresponding to the gradation is input.

The reference table 101 contains gradation data and application time information (or application pattern information) as write information.
Is written, and when writing is permitted by the gradation determination circuit 206, the gradation data and the application time (or application pattern) are written in association with each other. In this way, the reference table 101 stores the voltage application time (or voltage application pattern) corresponding to each gray level in consideration of the area of the hatched portion in FIG.

Incidentally, when displaying an actual image, it is ideal to select a point where the relationship between the gradation and the luminance falls on a gamma curve as shown in FIG. At this time, as shown in this embodiment, each color LED
By applying different voltages with different application patterns within the light emission period, a great number of gradations can be created by the applied patterns, so that points on the gamma curve can be easily selected, and high accuracy can be achieved. Gamma correction becomes possible.

Next, the operation of the liquid crystal driving device of this embodiment will be described with reference to FIG. FIG. 13A shows a drive voltage waveform applied to the liquid crystal. FIG. 13 (B) shows FIG.
FIG. 6 is a waveform diagram showing the amount of transmitted light of the liquid crystal when the voltage of the pattern of FIG. In the drawing, portions indicated as R, G, and B represent light emission periods of the LEDs of each color.

That is, when the driving voltage is applied at the time point t1, the transmitted light amount starts to increase from the time point t1. Then, at time t2, the R (red) LED emits light. Next, when the drive voltage is not applied at time t2, this time t2
From 2, the amount of transmitted light starts to decrease. Next, when an ON voltage is applied from time t2a to time t3, the amount of transmitted light increases during this period. Next, when the drive voltage is not applied at time t3, the transmitted light amount starts to decrease from this time t3, and the time t3
At 4, the light amount becomes 0. Incidentally, during the period from the time point t1 to the time point t2, the transmitted light amount increases but the LED is not emitting, so that the LCD display is not performed.

Similarly, when the drive voltage is applied at time t6, the transmitted light amount starts to increase from this time t6. Time t
When the G (green) LED starts to emit light at 7, the time t7
Starts the LCD display. Next, when the drive voltage is not applied from the time point t7a, the transmitted light amount starts to decrease from the time point t7a. Next, when an ON voltage is applied during a period from time t7b to time 8, the amount of transmitted light increases. Next, when the driving voltage is not applied at time t8, the transmitted light quantity starts to decrease from this time t8, and at time t9, the transmitted light quantity becomes 0, and the display ends.

Similarly, when the driving voltage is applied at time t10, the amount of transmitted light starts to increase from this time t10, and when the B (blue) LED starts to emit light at time t11, the LCD display starts at this time t11. Be started. Next, at time t12, the drive voltage is not applied and the light emission of the LED is stopped, so that the display is completed. By the way, in the display of B (blue), since the area surrounded by the amount of transmitted light and the light emission period is the maximum, it means that the maximum gradation in the liquid crystal is displayed.

Similarly, when the driving voltage is applied at time t13, the amount of transmitted light starts to increase at this time t13, and when the R (red) LED starts to emit light at time t14, the LCD display starts at this time t14. Be started. Next, when the drive voltage is not applied at time t15, the transmitted light quantity starts to decrease from this time t15, and at time t16, the transmitted light quantity becomes 0 and the display ends.

As described above, in the liquid crystal driving device according to the present embodiment, the liquid crystal is driven at the maximum voltage of the rated voltage, so that the rising and falling of the transmitted light amount waveform shown in FIG. Thus, the response speed of the liquid crystal can be increased. Thereby, for example, the frame frequency can be increased.

Further, since the voltage application time is set in consideration of the area obtained by integrating the transmitted light amount in the LED light emission period, a delicate gradation display suitable for the gradation can be performed.

Further, by applying the voltage of the on / off pattern in consideration of the area of the amount of transmitted light during the LED light emission period, a more delicate gradation display according to the gradation data can be performed.

Here, as a comparative example with the liquid crystal driving device of this embodiment, FIG. 14 shows a waveform diagram when the liquid crystal is driven by the conventional applied voltage variable system. In this liquid crystal driving method, the applied voltage value increases as the designated gradation increases.

That is, when a medium drive voltage is applied during the period from the time point t1 to the time point t3, an amount of transmitted light corresponding to the voltage value is obtained from the liquid crystal. Similarly,
When a drive voltage having a relatively large value is applied during a period from time t4 to time t6, a relatively large amount of transmitted light corresponding to the voltage value is obtained from the liquid crystal.

When the maximum drive voltage is applied during the period from time t7 to time t9, the liquid crystal produces a maximum amount of transmitted light corresponding to this voltage value. Further at time t10
When a small drive voltage is applied during a period from to time t12, a small amount of transmitted light corresponding to this voltage is obtained from the liquid crystal. Incidentally, the actual LCD display is performed during the period from time t2 to time t3, the period from time t5 to time t6, the period from time t8 to time t9, and the time from time t11 to time t12 when the RGB LEDs are emitting light. Period.

In the liquid crystal drive of the applied voltage variable system, the drive voltage value is set by paying attention to the average height of the transmitted light amount waveform in each display period. For example, from time t2 to time t3
The driving voltage is set such that the average height of the transmitted light amount in the period of the period satisfies the designated gradation.

On the other hand, in the liquid crystal drive of the transmitted light amount integration method according to the embodiment, the liquid crystal drive is performed in consideration of the integrated area of the transmitted light amount. It is possible to perform delicate gradation expression suitable.

As described above, according to the liquid crystal driving device of this embodiment, the driving voltage is controlled based on the integral value of the amount of transmitted light from the liquid crystal. The time is changed earlier than the response time (on / off) of the device. This makes it possible to control the degree of opening of the liquid crystal at the optimal timing in time and obtain a desired luminance.

(Embodiment 4) FIG. 15, in which parts corresponding to those in FIG. 1 are assigned the same reference numerals, shows the configuration of a liquid crystal drive device according to Embodiment 4. This liquid crystal driving device has an LCD panel 2
A temperature sensor 301 is provided near zero. When detecting the peripheral temperature of the liquid crystal, the temperature sensor 301 sends the detection result to the correction circuit 302 as temperature information.

[0093] The correction circuit 302
The ON time control signal output from the application time control unit 102 is corrected. Here, as shown in FIG. 16, the liquid crystal has a temperature characteristic in which the response speed of the liquid crystal decreases as the temperature decreases, and the amount of transmitted light decreases. In this embodiment, in consideration of this point, the ON time control signal is corrected such that the ON time becomes longer as the peripheral temperature of the liquid crystal becomes lower.

Thus, according to the above configuration, in addition to the effects obtained in the above-described first to third embodiments, a liquid crystal driving device with further improved gradation display accuracy in consideration of the temperature characteristics of the liquid crystal is provided. The effect that can be realized can be obtained.

(Embodiment 5) FIG. 17 in which portions corresponding to those in FIG. 1 are assigned the same reference numerals, shows the configuration of a liquid crystal driving device according to Embodiment 5. In this liquid crystal driving device, a luminance detecting unit 401 is provided at a position where the periphery of the LCD panel 20 is inconspicuous. In the case of this embodiment, the brightness detection unit 401
Comprises a detection cell arranged in a liquid crystal cell array, and a photosensor for detecting the luminance of the detection cell. Then, the luminance detection result detected by the photo sensor is sent to the correction circuit 402 as luminance information.

The correction circuit 402 receives gradation data in addition to the luminance information from the luminance detection unit 401.
The luminance information and the gradation data are compared. If the luminance information is different from the gradation data, the ON time control signal output from the application time control unit 102 is corrected according to the difference. Specifically, when the luminance indicated by the luminance information is smaller than the gradation indicated by the gradation data, the ON time control signal is corrected so that the ON time becomes longer.

Here, when LEDs are used for many years, the brightness tends to decrease due to aging. Especially B out of RGB
The luminance of the (blue) LED may be significantly reduced due to aging. In this embodiment, in consideration of this point, the ON time control signal is corrected so that the ON time becomes longer as the luminance of the transmitted light of the liquid crystal becomes lower. In addition to this, the white balance is corrected by changing the current value of each color according to the luminance information. As a result, a liquid crystal display device having a good luminance balance can be obtained.

Thus, according to the above configuration, in addition to the effects obtained in the above-described first to third embodiments, the gradation display accuracy is further improved in consideration of a decrease in luminance due to aging of the LED. An effect that a liquid crystal driving device can be realized can be obtained.

(Other Embodiments) The operation modes of the liquid crystal molecules of the LCD panel in this embodiment are as follows.
TN (Twisted Nematic) mode, STN (Super Twist
ed Nematic) mode, ferroelectric liquid crystal mode, birefringence mode, guest / host mode, dynamic scattering mode, phase transition mode, etc.

The present invention is not limited to the above embodiment, but can be implemented with various modifications. For example,
In the above embodiment, the case where the applied voltage is 5 V is described, but the present invention is not limited to this, and can be applied to the case where the applied voltage is other than 5 V.

In the third embodiment described above, by storing data by the transmitted light intensity integration method in the reference table 101 of the first embodiment, the voltage in consideration of the area obtained by integrating the transmitted light amount of the liquid crystal in the LED light emission period is considered. Although the case where the application time is set has been mainly described, the present invention is not limited to this, and data according to the transmitted light amount integration method may be stored in the pattern table 104 of the second embodiment. In this case, if a voltage of a certain pattern is applied to the liquid crystal, the transmitted light amount of the liquid crystal is detected, and a voltage application pattern suitable for each gradation is set in consideration of an area obtained by integrating the transmitted light amount in the LED emission period. Good.

In particular, the pattern voltage application method of the present invention, as described in the second embodiment, applies a pattern voltage corresponding to the gradation data within one LED light emission period, thereby making it possible to perform the comparison with the conventional PWM control. Thus, a delicate LCD display according to the gradation data can be performed. In addition, by determining this application pattern in accordance with the above-described integral area, a more delicate L in accordance with the gradation data can be obtained.
CD display becomes possible.

In the fourth embodiment, the case where the voltage application time is corrected according to the temperature detection result has been described. However, the present invention is not limited to this, and the voltage application pattern is corrected according to the temperature detection result. You may do so.

Similarly, in Embodiment 5 described above, the case where the voltage application time is corrected according to the luminance detection result has been described. However, the present invention is not limited to this, and the voltage application pattern is corrected according to the luminance detection result. You may make it.

In the above embodiment, the case where the pulse pattern control method according to the present invention in which the integrated value of the amount of transmitted light is considered is applied to control without using a D / A converter has been described. The present invention is not limited to this, and can be applied to control using a D / A converter. For example, a D / A converter capable of expressing a specific gradation (for example, 4 gradations) (in the case of digital control as in the embodiment, it can be considered as a 2 gradation D / A converter) and the present invention (For example, a quaternary voltage application pattern), it is possible to express gray scales with more levels.

Further, in the above-described embodiment, the case where the liquid crystal driving device and the liquid crystal driving method according to the present invention are applied to a liquid crystal display device of a field sequential system has been described. Even when the present invention is applied to another liquid crystal display device such as a liquid crystal display system or a projector system, the same effects as those of the above-described embodiment can be obtained.

[0107]

As described above, according to the present invention,
It is possible to provide a novel liquid crystal driving device and a gradation display method capable of performing multi-gradation display by digital control and driving a liquid crystal at high speed.

According to the present invention, when a constant voltage is applied to the liquid crystal, the voltage corresponding to each gradation data is taken into account in consideration of the area obtained by integrating the amount of transmitted light of the liquid crystal at each point in the LED emission period. By setting the application time,
Even when driving the liquid crystal only with the maximum voltage of the rated voltage,
A liquid crystal driving device capable of performing fine gradation display can be provided.

According to the present invention, since a voltage according to the voltage application pattern is applied within the unit light emitting period of the LED,
It is possible to provide a liquid crystal driving device capable of performing fine gradation display according to gradation data as compared with a conventional PWM or the like. In addition, by setting the voltage application pattern in consideration of the area obtained by integrating the amount of transmitted light at each point of the liquid crystal by the application pattern supply time when the voltage application pattern is applied to the liquid crystal, the gradation data can be further increased. Delicate gradation display according to the image.

According to the present invention, an intermediate voltage between the maximum voltage and the minimum voltage of the rated voltage of the liquid crystal is not supplied to the liquid crystal, and only the maximum voltage and the minimum voltage are supplied to the liquid crystal to perform gradation display. By doing so, it is possible to provide a liquid crystal driving device and a liquid crystal driving device capable of driving liquid crystal at a higher speed.

Further, according to the present invention, the temperature sensor and / or the luminance detecting means are provided near the liquid crystal, and the voltage application time or the voltage application pattern is corrected according to the detection result of the temperature sensor and / or the luminance detecting means. Accordingly, it is possible to provide a liquid crystal driving device and a method with further improved gradation display accuracy.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a schematic configuration of a liquid crystal driving device according to a first embodiment of the present invention.

FIG. 2 is a view showing a reference table in the liquid crystal driving device shown in FIG. 1;

FIG. 3 is a diagram showing a relationship between light transmittance and time.

FIG. 4 shows a relationship between applied voltage and time.

FIG. 5 is a diagram showing a relationship between an applied voltage and time for each gradation.

FIG. 6 is a diagram showing timing of voltage application.

FIG. 7 is a block diagram illustrating a schematic configuration of a liquid crystal driving device according to a second embodiment of the present invention.

8 is a view showing a pattern table in the liquid crystal driving device shown in FIG. 7;

FIG. 9 is a diagram showing a voltage application pattern.

FIG. 10 is a diagram showing a relationship between a transmitted light amount and time for explaining a transmitted light amount integration method according to a third embodiment of the present invention;

FIG. 11 is a block diagram for explaining creation of a reference table used in the liquid crystal driving device according to the third embodiment of the present invention;

FIG. 12 is a characteristic curve diagram for explaining gamma correction.

FIG. 13 is a waveform chart for explaining the operation in the transmitted light amount integration method according to the third embodiment.

FIG. 14 is a waveform chart for explaining an applied voltage variable method used for comparison with the third embodiment.

FIG. 15 is a block diagram illustrating a schematic configuration of a liquid crystal driving device according to a fourth embodiment of the present invention.

FIG. 16 is a diagram showing temperature characteristics of a liquid crystal;

FIG. 17 is a block diagram illustrating a schematic configuration of a liquid crystal driving device according to a fifth embodiment of the present invention.

FIG. 18 is a block diagram showing a schematic configuration of a conventional liquid crystal driving device.

FIG. 19 is a diagram showing a relationship between light transmittance and applied voltage.

[Explanation of symbols]

 Reference Signs List 10 liquid crystal drive device 20 LCD panel 101 reference table 102 application time control unit 103 switch 104 pattern table 105, 203 constant voltage generation circuit 201 application time setting circuit 204 luminance sensor 205 integration circuit 301 temperature sensor 302, 402 correction circuit 401 luminance detection unit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification code FIG09G 3/20 631 G09G 3/20 631U 641 641A 642 642F 670 670L 3/34 3/34 J H04N 5/66 H04N 5/66 B 9/30 9/30 (56) References JP-A-8-54859 (JP, A) JP-A-3-134695 (JP, A) JP-A-63-231423 (JP, A) JP-A-11-296150 (JP, A) JP-A-10-268849 (JP, A) JP-A-9-114421 (JP, A) JP-A-11-38386 (JP, A) (58) Fields investigated (Int. Cl. ⁷⁾ G09G 3/00-3/38 G02F 1/133 H04N 5/66 H04N 9/30

Claims (9)

(57) [Claims] And a control unit that controls the amount of light transmitted through the light emitting unit according to an applied voltage.
The same number of ON times in the liquid crystal to be controlled and the unit light emission period
To set the applied voltage of multiple on-off patterns different from each other.
Voltage application pattern setting means and a voltage application pattern
One of the on-off patterns set by the turn setting means
The voltage of the turn is supplied to the liquid crystal in accordance with the gray scale.
Liquid crystal transmission during a unit light emission period.
Light amount is variably controlled according to the on / off pattern,
A liquid crystal drive device characterized by the above-mentioned. 2. The on / off operation of said voltage application pattern setting means.
The pattern is based on the integrated value of the amount of transmitted light during the unit light emission period of the light emitting section.
Is set Zui, liquid crystal driving device according to claim 1, wherein a. Wherein the voltage applying pattern setting means sets a voltage application pattern with reference to the table that associates said gradation-off patterns, it is characterized 請
The liquid crystal driving device according to claim 1 or 2 . 4. The table according to claim 1, wherein each of the tables is different .
When the voltage of Fupatan supplied to the liquid crystal, each on
The transmitted light amount of the liquid crystal that changes in the off pattern is detected over time, and the detected transmitted light amount is integrated over the unit light emission period of the light emitting section to obtain an area, and the area is associated with the gradation data, thereby obtaining the gradation data. claims, characterized in said the off pattern to associate have been created, that a
3. The liquid crystal driving device according to 3 . 5. The liquid crystal display according to claim 1, wherein said voltage supply means does not supply an intermediate voltage between a maximum voltage and a minimum voltage to said liquid crystal, but supplies only a maximum voltage and a minimum voltage to said liquid crystal to perform gradation display. The liquid crystal driving device according to any one of claims 1 to 4 , wherein: 6. provided near the liquid crystal, a temperature sensor for detecting the ambient temperature of the liquid crystal, the voltage applying path
The turn setting means corrects the voltage application pattern according to a detection result of a temperature sensor.
The liquid crystal driving device according to any one of claims 1 to 4 . 7. provided near the liquid crystal, comprising a brightness detecting means for detecting the intensity of the transmitted light of the liquid crystal, said voltage
5. The liquid crystal driving device according to claim 1, wherein the application pattern setting unit corrects the voltage application pattern according to a detection result of the luminance detection unit. 6. 8. The method according to claim 1, wherein :
This the liquid crystal driving device, R, G, B causes sequentially emit respective colors of LED, so the aperture ratio of the liquid crystal which is provided in correspondence with the respective colors of the LED is changed by the voltage applied to the liquid crystal of
Thus, a liquid crystal driving device is used for a field sequential type liquid crystal display device that performs gradation display . 9. A method for applying a voltage to a liquid crystal within a unit light emitting period of a light emitting unit.
Voltage application pattern
Setting voltage application patterns having different on / off patterns from each other , and any one of the voltage application patterns.
Supplying a voltage of an on-off pattern to the liquid crystal in accordance with the gradation, and transmitting the amount of liquid crystal through the unit light emission period.
Variably controlled according to the on / off pattern .