TWI410936B - Liquid crystal display and method for driving same - Google Patents

Abstract

The present invention relates to a liquid crystal display. The liquid crystal display includes a controlling unit, n inverter, and a load. The controlling unit is used for providing a first control signal and a second control signal to the inverter according to video signals. The load is used for providing light beams. The inverter is used for providing a modulating current to adjust a working current of the load according to the first and second control signals. The present invention also relates to a method for driving the liquid crystal display.

Description

Liquid crystal display and driving method thereof

The present invention relates to a liquid crystal display and a method of driving the same.

Liquid crystal displays (LCDs) are widely used because of their small size, low power consumption, and low radiation.

Currently, liquid crystal displays generally include a liquid crystal display panel and a backlight driving circuit. Since the liquid crystal display panel cannot actively emit light, the backlight driving circuit is required to provide light to the liquid crystal display panel. The outer surface of the liquid crystal display is generally provided with a button, and the user of the liquid crystal display can control the light intensity provided by the backlight driving circuit by operating the button, thereby adjusting the brightness of the image displayed by the liquid crystal display panel.

If the user of the liquid crystal display is watching a movie, or when the ambient light around the liquid crystal display is relatively dark, the user needs to manually set the brightness of the liquid crystal display panel. Moreover, after the user setting is completed, the light intensity provided by the backlight driving circuit cannot be automatically changed.

If the user sets a large intensity for the light provided by the backlight driving circuit, and the image actually displayed by the liquid crystal display panel does not require high brightness, but the user forgets to reset the backlight brightness, which will cause the liquid crystal The energy of the display is wasted.

In addition, when the liquid crystal display needs to display a dark image or a black image, since the backlight driving circuit can only provide the light of the intensity set by the user, the brightness of the image displayed by the liquid crystal display often tends to be relatively high. Big, can't get better visual effects.

In view of this, it is necessary to provide a liquid crystal display capable of automatically adjusting the backlight intensity.

It is also necessary to provide a driving method of the above liquid crystal display.

A liquid crystal display comprising a backlight driving circuit, the backlight driving circuit comprising a control unit, an inverter and a load. The control unit is configured to provide a first control signal and a second control signal to the inverter according to the external image signal. The inverter is configured to adjust the luminous intensity of the load according to the first control signal and the second control signal.

A liquid crystal display comprising a backlight driving circuit, the backlight driving circuit comprising a control unit, an adjusting unit, an inverter and a load. The control unit is configured to provide a first control signal to the inverter according to the external image signal, and provide a second control signal to the adjusting unit according to the external image signal. The adjusting unit is configured to provide an adjustment voltage to the inverter according to the second control signal. The inverter is configured to output an adjustment current to the load according to the first control signal and the adjustment voltage, and the adjustment current can adjust an illumination intensity of the load.

A liquid crystal display comprising a control unit, an inverter and a load, the control unit being capable of receiving an external image signal and providing at least one control signal to the inverter according to the image signal, the inverter being used according to the The control signal adjusts the operating current of the load.

A liquid crystal display includes a control unit, an inverter and a load, and the control unit is configured to provide a plurality of first images according to an external image signal The control signal and the plurality of second control signals are sent to the inverter, and the inverter is configured to adjust an operating current of the load according to the plurality of first control signals and the plurality of second control signals.

A liquid crystal display driving method, comprising: a control unit, an inverter and a load, the method comprising: receiving an image signal; calculating an image brightness value corresponding to the received image signal; and according to the image brightness value Providing a first control signal and a second control signal; adjusting the luminous intensity of the load according to the first control signal and the second control signal.

Compared with the prior art, the liquid crystal display includes the control unit and the inverter, and the control unit outputs the at least one control signal to the inverter according to the received image signal, and the inverter is configured according to the at least one control signal. The luminous intensity of the load is automatically adjusted. The above liquid crystal display driving method can adjust the luminous intensity of the load according to the calculation result of the received image signal.

Please refer to FIG. 1, which is a block diagram of a circuit of a first embodiment of a liquid crystal display (not shown) of the present invention. The liquid crystal display includes a liquid crystal display panel (not shown) and a backlight driving circuit 10. The backlight driving circuit 10 is configured to provide light to the liquid crystal display panel, and the liquid crystal display panel is configured to display a corresponding image according to an external image signal.

The backlight driving circuit 10 includes a control unit 11, an inverter 13, and a load 14. The control unit 11 is configured to provide a first control signal and a second control signal to the inverter 13 according to an external image signal. The inverter 13 is configured to adjust the load according to the first and second control signals respectively 14 working current. The load 14 has different luminous intensities at different operating currents. The first and second control signals are pulse signals, each having a certain duty ratio. The so-called duty cycle is the ratio of the duration of the signal and the duration of the entire period in one cycle of the pulse signal.

When the backlight driving circuit 10 is in normal operation, the control unit 11 receives an external image signal and calculates the received image signal.

Before the control unit 11 receives the image signal corresponding to the black image, the duty ratio of the first control signal output by the control unit 11 depends on the user's demand setting for the image display brightness. The duty ratio of the first control signal may range from 0 to 100%. For example, the user can adjust the duty ratio of the first control signal through an external on-screen display unit connected to the control unit 11, and the external OSD unit can include a button extending to the outer surface of the liquid crystal display. User-friendly operation control. At the same time, the second control signal output by the control unit 11 has a first duty ratio.

When the control unit 11 receives the image signal corresponding to the black image, the control unit 11 outputs the first control signal having the corresponding duty ratio according to the calculation result of the received image signal. The result of the calculation can represent the average brightness value of the image corresponding to the received image signal. The calculation result has a preset linear or non-linear correspondence relationship with the duty ratio of the first control signal. For example, the calculation result may be 0 to 100, where 0 represents the darkest (in this case, the image signal corresponds to Black image), 100 represents the brightest (in this case, the image signal corresponds to the all-white image), and the duty ratio of the first control signal is 20%~100%. The above calculation process for the image signal can be A calculation circuit implemented in advance in the control unit 11 , for example, the calculation circuit may pre-store a relationship between a plurality of different image signals and their corresponding brightness values. Whenever all or part of the image signals included in an image are received, the received image signal is calculated to obtain the brightness value of the corresponding image. At the same time, the control unit 11 outputs a second control signal having a second duty ratio, and the second control signal will thereafter remain with the second duty ratio. The first duty ratio of the second control signal is greater than the second duty ratio thereof. If the first duty cycle can be 100%, the second duty cycle can be 20%. Therefore, after the control unit 11 receives the image signal corresponding to the black image, the duty ratio of the second control signal is changed from the first duty ratio to the second duty ratio. During the subsequent operation of the backlight driving circuit 10, the second control signal will maintain the second duty cycle.

The inverter 13 receives the first control signal and the second control signal, and outputs an adjustment current to the load 14. The first control signal is used to adjust the duty ratio of the adjustment current, and the second control signal is used to adjust the amplitude of the adjustment current. The magnitude of the adjustment current is simultaneously proportional to the duty cycle of the first and second control signals. Any one of the duty ratios of the first and second control signals is individually reduced, and the adjustment current is reduced. When the duty ratio of the first control signal and the adjustment voltage decrease simultaneously, the adjustment current decreases. The duty cycle and amplitude of the regulated current determine the duty cycle and amplitude of the operating current of the load 14, respectively. Therefore, when the adjustment current is decreased, the operating current of the load 14 is reduced.

Please refer to FIG. 2 , which is a schematic diagram of waveform changes of the adjustment current of the backlight driving circuit 10 shown in FIG. 1 . Wherein, the control unit 11 is connected at time t0. The received image signal corresponds to a black image. As shown, since the time t0, the duty cycle of the first control signal is reduced, and the duty cycle of the adjustment current is reduced. At the same time, the duty ratio of the second control signal is reduced from the first duty ratio to the second duty ratio, and the corresponding adjustment voltage is reduced from the first adjustment voltage to the second adjustment voltage, so the amplitude of the adjustment current Also reduced.

Therefore, the backlight driving circuit 10 can automatically adjust the luminous intensity of the load 14 according to the received image signal, so that the brightness of the liquid crystal display when displaying a black image is low, and the effect of displaying the image by the liquid crystal display is better.

Please refer to FIG. 3, which is a block diagram showing the circuit of the second embodiment of the liquid crystal display (not shown) of the present invention. The liquid crystal display includes a liquid crystal display panel (not shown) and a backlight driving circuit 20. The backlight driving circuit 20 is configured to provide light to the liquid crystal display panel, and the liquid crystal display panel is configured to display a corresponding image according to an external image signal.

The backlight driving circuit 20 includes a control unit 21, an adjusting unit 22, an inverter 23, and a load 24. The control unit 21 is configured to provide a first control signal to the inverter 23 and a second control signal to the adjusting unit 22 according to the external image signal. The liquid crystal display panel receives the image signal and displays an image having a corresponding brightness. The adjusting unit 22 is configured to receive the second control signal, and provide an adjustment voltage to the inverter 23 according to the second control signal. The inverter 23 is configured to receive the first control signal and the adjustment voltage, and provide an adjustment current according to the first control signal and the adjustment voltage, where the adjustment current corresponds to an operating current of the load 24. The first control signal is used to adjust the duty ratio of the adjustment current, and the second control signal is used to adjust the amplitude of the adjustment current. The adjustment voltage is one DC voltage. The load 24 is used to provide light to the liquid crystal display panel. The operating current of the load can be a sinusoidal current. The first and second control signals are all pulse signals, and the first and second control signals each have a certain duty ratio. The load 24 can be a plurality of cold cathode fluorescent lamps (CCFLs). The load 24 may be disposed on the side of the liquid crystal display panel or on the back side of the liquid crystal display panel.

Please refer to FIG. 4 , which is a schematic diagram of the circuit structure of the adjusting unit 22 shown in FIG. 3 . The adjustment unit 22 includes an integration circuit (not shown). The integrating circuit includes a resistor 221 and a capacitor 222. The resistor 221 is connected in series between the control unit 21 and the inverter 23. The capacitor 222 is connected in series between the resistor 221 and the inverter 23. between. The resistor 221 and the capacitor 222 actually constitute an R-C circuit. The R-C circuit can integrate the input pulse signal and convert it into a DC voltage output, and the magnitude of the DC voltage is proportional to the duty ratio of the input pulse signal. That is, if the duty cycle of the input pulse signal is smaller, the DC voltage of the output is smaller. The resistor can be 1 KΩ and can be 47 μF.

The integrating circuit includes an R-C circuit formed by the resistor 221 and the capacitor 222. Therefore, the integrating circuit can convert the second control signal provided by the control unit 21 into the adjusted voltage.

When the backlight driving circuit 20 is working normally, the control unit 21 receives an external image signal and calculates the received image signal.

Before the control unit 21 receives the image signal corresponding to the black image, the duty ratio of the first control signal output by the control unit 21 depends on The user needs to set the brightness of the image display, which can range from 0 to 100%. For example, the user can adjust the duty ratio of the first control signal through an external on-screen display unit connected to the control unit 21, and the external OSD unit can include a button extending to the outer surface of the liquid crystal display for convenience. User operation control. At the same time, the second control signal output by the control unit 21 has a first duty ratio.

When the control unit 21 receives the image signal corresponding to the image of the first reference brightness value, the control unit 21 outputs the first control signal having the corresponding duty ratio according to the calculation result of the received image signal. The result of the calculation can represent the average brightness value of the image corresponding to the received image signal. The calculation result has a preset linear or non-linear correspondence relationship with the duty ratio of the first control signal. For example, the calculation result may be 0 to 100, where 0 represents the darkest (in this case, the image signal corresponds to black) Image), 100 represents the brightest (in this case, the image signal corresponds to the white image), and the duty ratio of the first control signal is 20%~100%. The calculation process of the image signal may be implemented by a calculation circuit preset in the control unit 21. For example, the calculation circuit may pre-store a relationship between a plurality of different image signals and their corresponding brightness values. Each time an image signal of a specified portion of an image is received, the received image signal is calculated to obtain a brightness value corresponding to the image.

At the same time, the second control signal outputted by the control unit 21 has a second duty ratio, wherein the first duty ratio of the second control signal is greater than the second duty ratio thereof. If the first duty cycle can be 100%, the second duty cycle can be 20%. Thereafter, when the control unit 21 receives a corresponding second reference When the image signal of the brightness value is used, the duty ratio of the second control signal is restored to the first duty ratio.

The image brightness corresponding to the first reference brightness value is less than the image brightness corresponding to the second reference brightness value. For example, the image corresponding to the first reference brightness value may be a black image, and the image corresponding to the second reference brightness value may be a white image. In addition, the first reference brightness value and the second reference brightness value can be set at the factory according to the needs of different customers.

Therefore, after the control unit 21 receives the image signal corresponding to the image of the first reference luminance value, the duty ratio of the second control signal is changed from the first duty ratio to the second duty ratio, and The image brightness corresponding to the image signal received by the control unit 21 is switched between the first duty ratio and the second duty ratio.

As described above, before the control unit 21 receives the image signal corresponding to the image of the first reference luminance value, the second control signal output by the control unit 21 has the first duty ratio, and defines the adjustment at this time. The regulated voltage output by unit 22 is the first regulated voltage. After the control unit 21 receives the image signal corresponding to the image of the first reference brightness value, the second control signal output by the control unit 21 has the second duty ratio, and defines the output of the adjusting unit 22 at this time. The adjustment voltage is the second adjustment voltage. Because the first duty ratio is greater than the second duty ratio, the first adjustment voltage is greater than the second adjustment voltage. For example, when the first duty ratio is 100% and the second duty ratio is 20%, the first adjustment voltage may be 2.1V, and the second adjustment voltage may be 0.6V.

The inverter 23 receives the first control signal and the adjustment voltage, and further The adjustment current is output to the load 24 according to the first control signal and the adjustment voltage. The magnitude of the adjustment current is proportional to the duty ratio of the first control signal and the magnitude of the adjustment voltage. The duty ratio of the first control signal and the adjustment voltage are individually reduced, and the adjustment current is reduced. When the duty ratio of the first control signal and the adjustment voltage decrease simultaneously, the adjustment current decreases. At the same time, the magnitude of the adjustment current determines the operating current of the load 24. When the adjustment current decreases, the operating current of the load 24 decreases.

Please refer to FIG. 5 , which is a schematic diagram of waveform changes of the adjustment current of the backlight driving circuit 20 shown in FIG. 3 . The image signal received by the control unit at time t1 corresponds to a black image. As shown, since the time t1, the duty cycle of the first control signal is reduced, and the duty cycle of the adjustment current is reduced. At the same time, the duty ratio of the second control signal is reduced from the first duty ratio to the second duty ratio, and the corresponding adjustment voltage is reduced from the first adjustment voltage to the second adjustment voltage, so the amplitude of the adjustment current Reduced. Therefore, when the black image is displayed, the light intensity of the load 24 is small, the brightness of the image displayed by the liquid crystal display panel is low, and the effect of displaying the image by the liquid crystal display is better. At time t2, the control unit 21 receives an image signal corresponding to the white image, the duty ratio of the first control signal increases, and the duty ratio of the second control signal changes from the second duty ratio to the first a duty ratio, the adjustment voltage corresponding to the second adjustment voltage being changed to the first adjustment voltage. Therefore, the duty ratio and the amplitude of the adjustment current are correspondingly increased. In this case, the backlight driving circuit 20 can reduce the luminous intensity of the load 24 when it is required to display a black image, and increase the luminous intensity of the load 24 when displaying a white image.

In fact, the backlight driving circuit 20 has two operating states: an operating state before receiving an image signal corresponding to the image of the first reference luminance value and an image signal receiving an image corresponding to the first reference luminance value. Working status. The working state before the image signal receiving the image corresponding to the first reference brightness value is defined as a static working state, and the working state after receiving the image signal corresponding to the image of the first reference brightness value is a dynamic working state.

Then, in the static working state, the luminous intensity of the load 24 of the backlight driving circuit 20 is set by the user of the liquid crystal display; in the dynamic working state, the luminous intensity of the load of the backlight driving circuit 20 is driven by the backlight. Circuit 20 is automatically adjusted. The control unit 21 can adjust the output of the first and second control signals according to the received image signal, thereby automatically adjusting the illumination intensity of the load 24, so that the liquid crystal display panel is in a dynamic working state when the backlight driving circuit 10 is in a dynamic working state. The brightness of the image corresponding to the first reference brightness value displayed is lowered and the brightness of the image corresponding to the second reference brightness value is not lowered.

In summary, when the backlight driving circuit 20 is in a dynamic working state, the luminous intensity of the load 24 can be automatically adjusted according to the image signal, so that the liquid crystal display panel can obtain a better display effect and a higher contrast ratio. And better power saving performance.

Please refer to FIG. 6, which is a block diagram of a circuit of a third embodiment of the liquid crystal display (not shown) of the present invention. The liquid crystal display includes a liquid crystal display panel (not shown) and a backlight driving circuit 30. The backlight driving circuit 30 includes a control unit 31, an adjusting unit 32, an inverter 33, and a negative Load 34. The control unit 31 includes a reset circuit 311.

The control unit 31 is configured to provide a first control signal to the inverter 33 and a second control signal to the adjusting unit 32 according to the external image signal. The adjusting unit 32 is configured to receive the second control signal, and provide an adjusted voltage to the inverter 33 according to the second control signal. The inverter 33 is configured to receive the first control signal and the adjustment voltage, and provide an adjustment current according to the first control signal and the adjustment voltage for adjusting an operating current of the load 34.

The adjustment voltage is a DC voltage. The load 34 is used to provide light to the liquid crystal display panel. The adjustment current can be a sinusoidal current. The first and second control signals are all pulse signals, and the first and second control signals each have a certain duty ratio, and the amplitudes of the first and second control signals are 3.3V. The load 34 can be a plurality of cold cathode fluorescent lamps (CCFLs). The load 34 may be disposed on the side of the liquid crystal display panel or on the back side of the liquid crystal display panel.

Please refer to FIG. 7 , which is a schematic diagram of the circuit structure of the adjusting unit 32 shown in FIG. 6 . The adjusting unit 32 includes an integrating circuit 36 and a voltage dividing circuit 37. The integrating circuit 36 includes a first resistor 361, a second resistor 362, a first capacitor 363 and a second capacitor 364. The first and second resistors 361 and 362 are sequentially connected in series to the control unit 31 and the inverter. The first and second capacitors 363 and 364 are connected in parallel between the node between the first resistor 361 and the second resistor 362 and the ground. The first resistor 361 and the first and second capacitors 363, 364 actually constitute an R-C circuit. The voltage dividing circuit 37 includes a third resistor 371, a fourth resistor 372 and a third capacitor 373. The third and fourth resistors 371 and 372 are sequentially connected in series between a 5V DC voltage source and ground. A node between the third and fourth resistors 371, 372 is connected to the inverter 33, that is, the DC voltage source is connected to the inverter 33 via the third resistor 371, and the DC voltage source is further connected via the third The resistor 371 and the third capacitor 373 are grounded. The integrating circuit 36 is configured to convert the second control signal into a DC voltage, and the voltage dividing circuit 37 is configured to perform a voltage division process on the DC voltage converted by the integrating circuit 36 to obtain the adjusted voltage. When the backlight driving circuit 30 is working normally, the control unit 31 receives an external image signal and calculates the received image signal.

Before the image signal received by the control unit 31 corresponds to the black image, the duty ratio of the first control signal output by the first control unit depends on the user's requirement for the brightness of the image display, and the first control signal is The duty cycle can range from 0 to 100%. At this time, the control unit 21 outputs the second control signal having the first duty ratio.

When the image signal received by the control unit 31 corresponds to a black image, the control unit 31 outputs the first control signal having a corresponding duty ratio according to the calculation result of the received image signal. The calculation result can represent the brightness reference value of the image corresponding to the received image signal. The calculation result has a preset linear or non-linear correspondence relationship with the duty ratio of the first control signal. For example, the calculation result may be 0 to 100, where 0 represents the darkest (in this case, the image signal corresponds to Black image), 100 represents the brightest (in this case, the image signal corresponds to the all-white image), and the duty ratio of the first control signal is 20%~100%. The above calculation process of the image signal can be implemented by a calculation circuit preset in the control unit 21, for example, the meter The calculation circuit can pre-store the relationship between the plurality of image signals and the corresponding brightness values, and each time an image signal of a specified portion of the image is received, the received image signal is calculated to obtain the image. The average brightness value. At the same time, the second control signal output by the control unit 31 has a second duty ratio. The first duty ratio is greater than the second duty ratio. For example, the first duty ratio may be 100%, and the second duty ratio may be 20%. After the control unit 31 receives the image signal corresponding to the black image, the duty ratio of the second control signal is at the first duty ratio and the second duty according to the image brightness corresponding to the received image signal. Change between. That is, the control unit 31 outputs a first control signal having a duty ratio corresponding to the brightness of the image, and the duty ratio at this time is between the first duty ratio and the second duty ratio.

Therefore, after the image signal received by the control unit 31 corresponds to the black image, the duty ratios of the first and second control signals are automatically controlled by the control unit 31 according to the brightness value of the image corresponding to the received image signal. .

The reset circuit 311 includes a control button extending to the outer surface of the liquid crystal display panel, and the first and second control signals can be reset according to user requirements, so that the first and second control signals are returned to the control unit and the corresponding black is not received. The output of the image signal of the image. That is, the user of the liquid crystal display can return the first control signal to have a user-set duty ratio by controlling the reset circuit 311 while returning the second control signal to have a first duty ratio.

As described above, before the image signal received by the control unit 31 corresponds to the black image, the second control signal output by the control unit 31 has the first duty ratio, and the adjustment voltage output by the adjusting unit 32 is defined as First adjustment Voltage. When the control unit 31 receives the image signal corresponding to the black image, the second control signal output by the control unit 31 has the second duty ratio, and the adjustment voltage output by the adjusting unit 32 is defined as the second adjustment voltage. . Because the first duty ratio is greater than the second duty ratio, the first adjustment voltage is greater than the second adjustment voltage. For example, when the first duty ratio is 100% and the second duty ratio is 20%, the first adjustment voltage may be 2.1V, and the second adjustment voltage may be 0.6V.

The inverter 33 receives the first control signal and the adjustment voltage, and adjusts the duty ratio and the amplitude of the adjustment current according to the first control signal and the adjustment voltage respectively, so that the duty ratio and the amplitude of the adjustment current are adjusted. The values are reduced separately. The magnitude of the adjustment current is proportional to the duty ratio of the first control signal and the magnitude of the adjustment voltage. Therefore, any one of the duty ratio of the first control signal and the adjustment voltage is separately reduced, and the adjustment current is reduced. When the duty ratio of the first control signal and the adjustment voltage decrease simultaneously, the adjustment current decreases. At the same time, the magnitude of the adjustment current determines the operating current of the load. When the adjustment current decreases, the operating current of the load decreases. The relationship between the adjustment current and the first and second control signals may be: I=3.14×V×D÷1.414 (where I represents the adjustment current, V represents the adjustment voltage, and D represents the duty cycle of the first control signal) ).

Therefore, when the liquid crystal display displays a black image, the backlight driving circuit 30 provides a backlight with a small intensity. After the black image is displayed, the backlight driving circuit 30 can automatically adjust the duty ratio of the first and second control signals according to the image signal, thereby adjusting the duty ratio of the regulated current output by the inverter 33 and Amplitude that causes the load 34 to illuminate when displaying a black image The degree is small, and during the subsequent image display, the luminous intensity of the load 34 is automatically adjusted according to the image signal, and the brightness of the displayed white image is not lowered.

Generally, the duty cycle of the adjustment current cannot be lower than the minimum value of the normal operating range (for example, the duty ratio is not less than 20%), and the amplitude of the adjustment current cannot be lower than the minimum value of the normal operating range. (such as 3mA), otherwise the effect of the image displayed by the LCD will be affected, and even the displayed image will appear ripples. Therefore, the liquid crystal display that adjusts the luminous intensity of the load by separately adjusting the duty ratio or separately adjusting the amplitude can not further reduce the brightness when displaying the black image, so that the contrast can only reach about 6000:1. For example, a typical liquid crystal display displays a white image with a maximum brightness of 300 lumens, and a black image with a brightness of 0.05 lumens, and a contrast ratio of 6000:1. In addition, in the case where the brightness of the image corresponding to the image signal is the same, the difference in the luminous intensity of the load 34 may cause the brightness of the image displayed by the liquid crystal display to be different. A liquid crystal display that adjusts the duty ratio of the load by separately adjusting the duty ratio or separately adjusting the amplitude to display a white image may have a small range of brightness between the maximum brightness and the minimum brightness, such as displaying the maximum brightness of the white image. For 300 lumens, the white image has a minimum brightness of 67 lumens and its brightness adjustment range is only (300-67) ÷ 300 = 75%.

When the liquid crystal display displays a black image, the first control signal can control the duty ratio of the adjustment current to a minimum value of a normal working range, and the second control signal can control the amplitude of the adjustment current to a normal working range. Minimum value, so it is possible to simultaneously adjust the duty cycle and amplitude of the current Line adjustment. The magnitude of the adjustment current can be changed to be smaller than if the duty ratio or amplitude of the adjustment current is separately adjusted, so that the brightness of the black image displayed by the liquid crystal display is lower. By adjusting the duty ratio and the amplitude of the adjustment current by the backlight driving circuit 30, the contrast of the liquid crystal display can be remarkably improved. For example, when the liquid crystal display displays a white image, the maximum brightness can be 300 lumens, and when the black image is displayed, the brightness can be as low as about 0.014 lumens, so that the contrast can reach up to 20,000:1 or more, so that the liquid crystal display displays the image. Has a good visual effect. The liquid crystal display can display a white image with a maximum brightness of 300 lumens, and a white image with a minimum brightness of 12 lumens, and the brightness adjustment range can be greatly improved to (300-12) ÷ 300 = 96%.

After the backlight driving circuit 30 receives the image signal corresponding to the black image, the backlight driving circuit 30 automatically adjusts the adjusting current according to the brightness of the image corresponding to the received image signal, thereby adjusting the luminous intensity of the load 34. Therefore, the liquid crystal display shows that a better display effect, a higher contrast effect, and better power saving performance can be obtained.

The present invention is not limited to the above embodiments. For example, when the control unit 11 in the first embodiment receives the image signal corresponding to the black image, the first control signal output by the control unit 11 remains the brightness set by the user. The duty ratio corresponding to the value, the duty ratio of the second control signal becomes the second duty ratio.

In addition, the second control signal in the first embodiment may be a DC voltage signal. Before the control unit 11 receives the image signal corresponding to the black image, the voltage of the second control signal is a first voltage, and the control After the unit 11 receives the image signal corresponding to the black image, the voltage of the second control signal becomes a second voltage, and the first voltage is greater than the second voltage. The first voltage can be 2.1V and the second voltage can be 0.6V.

In addition, the adjustment unit 32 in the third embodiment may be omitted. When the backlight driving circuit 30 is in a static working state, the second control signal outputted by the control unit 31 to the inverter 33 is a 2.1V DC voltage, and when the backlight driving circuit is in a dynamic working state, the control The second control signal outputted by the unit 31 to the inverter 33 is a 0.6V DC voltage. The above working process can be realized by software or hardware setting inside the control unit 21.

In addition, the reset circuit 311 in the third embodiment can be combined with an OSD unit, and the user can reset the first control signal and the second control signal by adjusting the content of the OSD unit.

In addition, the reset circuit 311 in the third embodiment may be disposed outside the control unit 31, and the first and second control signals are reset by the control unit 31.

In addition, the control unit 31 in the third embodiment can change the condition for setting the dynamic operation mode of the backlight driving circuit 30, that is, when the image signal corresponding to the image of the specific brightness value can be set, the backlight driving circuit 30 enters the dynamic state. Operating mode.

In addition, the second control signal outputted by the control unit 21 in the second embodiment automatically adjusts according to the image brightness value corresponding to the received image signal when the backlight driving circuit 20 is in the dynamic working state, and the adjustment voltage also corresponds to Variety. For example, the second control signal is received at the control unit 21 When the image brightness value corresponding to the image signal changes, the image brightness value corresponding to the different duty ratio automatically changes between the first duty ratio and the second duty ratio. The change in the duty cycle of the second control signal can be implemented by the software or hardware setting of the control unit 21, and the change can be linear or non-linear, continuous or non-continuous.

In addition, the duty ratio of the second control signal output by the control unit 21 in the second embodiment may remain unchanged during the static working state and the dynamic working state. The second control signal has a first frequency in a static operating state and a second frequency in a dynamic operating state, the first frequency being greater than the second frequency. The first frequency corresponds to a first adjustment voltage, and the second frequency corresponds to a second adjustment voltage.

In addition, the control unit 21 in the second embodiment may output a plurality of first control signals and a plurality of second control signals, where the plurality of first control signals are used to adjust a duty ratio of the adjustment current, the plurality of second The control signal is used to adjust the amplitude of the adjustment current.

In addition, the control unit 21 in the second embodiment may output at least one control signal, and when the static working state enters the dynamic working state, the duty ratio and the frequency of the at least one control signal become smaller, respectively, so that the duty of the adjusting current is small. The ratio and frequency are smaller.

In addition, the control unit 21 in the second embodiment may output at least one control signal, and when entering the dynamic working state from the static working state, the duty ratio and the amplitude of the at least one control signal become smaller, respectively, thereby adjusting the current The duty cycle and amplitude are reduced respectively.

In addition, the control unit 21 in the second embodiment may further provide a third The control signal is sent to the inverter 23. The frequency of the third control signal in the static working state is greater than the frequency in the dynamic working state, so that the frequency of the adjusting current in the static working state is also greater than the frequency in the dynamic working state.

In summary, the present invention has indeed met the requirements of the invention patent, and has filed a patent application according to law. However, the above description is only the preferred embodiment of the present invention, and the scope of the present invention is not limited to the above-described embodiments, and equivalent modifications or variations made by those skilled in the art in light of the spirit of the present invention are It should be covered by the following patent application.

Backlight drive circuit ‧‧10,20,30

First resistance ‧‧‧361

Control unit ‧‧11,21,31

Second resistance ‧‧‧362

Adjustment unit ‧‧‧22,32

Third resistance ‧‧‧371

Inverter ‧‧‧13, 23, 33

Fourth resistance ‧‧‧372

Load ‧‧‧14,24,34

First capacitor ‧‧‧363

Resistance ‧‧‧221

Second capacitor ‧‧‧364

Capacitance ‧‧‧222

Third capacitor ‧‧ 373

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a block diagram showing the circuit of a first embodiment of a liquid crystal display of the present invention.

FIG. 2 is a schematic diagram showing changes in the adjustment current waveform of the backlight driving circuit shown in FIG. 1. FIG.

3 is a block diagram showing the circuit of a second embodiment of the liquid crystal display of the present invention.

FIG. 4 is a schematic structural diagram of the adjustment unit circuit shown in FIG. 3.

FIG. 5 is a schematic diagram showing changes in the adjustment current waveform of the backlight driving circuit shown in FIG. 3. FIG.

Figure 6 is a block diagram showing the circuit of a third embodiment of the liquid crystal display of the present invention.

FIG. 7 is a schematic diagram showing the circuit structure of the adjusting unit shown in FIG. 6.

Backlight drive circuit ‧‧20

Control unit ‧‧21

Adjustment unit ‧‧22

Inverter ‧‧23

Load ‧‧‧24

Claims (25)

A liquid crystal display comprising a backlight driving circuit, the backlight driving circuit comprising a control unit, an inverter connected to the control unit, and a load connected to the inverter, the control unit for using an external map The image sensor provides a first control signal and a second control signal to the inverter, and the control unit is capable of calculating a brightness value of the image corresponding to the received image signal, and when the calculation result satisfies a preset first reference When the brightness value is used, the backlight driving circuit enters a dynamic working state from a static working state. When the backlight driving circuit is in a static working state, the first control signal is set by a user, and the second control signal has a first duty ratio. When the backlight driving circuit is in a dynamic working state, the first control signal is provided by the adjusting unit according to the brightness value of the image corresponding to the received image signal, and the second control signal has a second duty ratio, the first The duty ratio is greater than the second duty ratio, and the inverter is configured to adjust the luminous intensity of the load according to the first control signal and the second control signal The liquid crystal display of claim 1, wherein the inverter outputs an adjustment current according to the first and second control signals, wherein the first control signal is used to adjust a duty ratio of the adjustment current, The second control signal is used to adjust the amplitude of the adjustment current. The liquid crystal display of claim 1, wherein the first duty ratio is 100% and the second duty ratio is 20%. The liquid crystal display according to claim 1, wherein when the backlight driving circuit is in a static working state, the duty ratio of the first control signal is set according to a brightness requirement of the displayed image by the user; When the optical driving circuit is in a dynamic working state, the duty ratio of the first control signal changes between 20% and 100%. The liquid crystal display of claim 1, wherein the preset first reference brightness value corresponds to a black image. The liquid crystal display according to claim 1, wherein when the backlight driving circuit is in a dynamic working state, when the control unit receives a corresponding second reference brightness value, the second control signal is occupied. The null ratio is changed from the second duty ratio to the first duty ratio. The liquid crystal display of claim 6, wherein the preset second reference brightness value corresponds to a white image. The liquid crystal display of claim 1, wherein the first and second control signals are pulse signals. The liquid crystal display of claim 1, further comprising a liquid crystal display panel, wherein the liquid crystal display panel displays an image having a corresponding brightness according to an external image signal. A liquid crystal display includes a control unit, an adjusting unit, an inverter and a load, and the control unit is configured to provide a first control signal to the inverter according to an external image signal, and according to an external map The image sensor provides a second control signal to the adjustment unit, and the adjustment unit is configured to provide an adjustment voltage to the inverter according to the second control signal, and the control unit calculates the brightness of the image corresponding to the received image signal. a value, when the calculation result does not satisfy a preset reference brightness value, the first control signal is set by a user, the second control signal has a first duty ratio, and the adjustment unit outputs a first adjustment voltage; Result satisfaction When the preset brightness value is preset, the first control signal is provided by the adjusting unit according to an average brightness value of the image corresponding to the received image signal, and the second control signal has a second duty ratio, the adjustment The unit outputs a second adjustment voltage, the first duty ratio is greater than the second duty ratio, and the inverter is configured to output an adjustment current to the load according to the first control signal and the adjustment voltage, and the adjustment current can be adjusted. The luminous intensity of the load. The liquid crystal display of claim 10, wherein the adjusting unit comprises an integrating circuit, the integrating circuit comprising a first resistor, a second resistor, a first capacitor and a second capacitor, the first The second resistor is sequentially connected in series between the control unit and the inverter, and the first and second capacitors are connected in parallel between a node between the first resistor and the second resistor and the ground, and the integrating circuit is used for Converting the second control signal to a DC voltage. The liquid crystal display of claim 11, wherein the adjusting unit further comprises a voltage dividing circuit, the voltage dividing circuit comprising a third resistor, a fourth resistor and a third capacitor, the third The fourth resistor is connected in series between a DC voltage source and a ground. The DC voltage source is connected to the inverter via the third resistor, and the DC voltage source is further grounded via the third resistor and the third capacitor. The voltage dividing circuit is configured to convert the DC voltage converted by the integrating circuit into the adjusted voltage. The liquid crystal display according to claim 10, wherein the duty ratio of the second control signal after the brightness of the image corresponding to the image signal received by the control unit is the preset reference brightness value Maintained at the second duty cycle. The liquid crystal display of claim 10, wherein the control unit receives the image signal according to the received image after the brightness of the image corresponding to the image signal received by the control unit is the preset reference brightness value. The brightness of the corresponding image adjusts the duty ratio of the second control signal such that the duty ratio of the second control signal corresponds to an image of different brightness between the first duty ratio and the second duty ratio. The liquid crystal display according to claim 10, wherein the first adjustment voltage is 2.1V, and the second adjustment voltage is 0.6V. The liquid crystal display of claim 10, wherein the first control signal is used to adjust a duty ratio of the adjustment current, and the second control signal is used to adjust a magnitude of the adjustment current. A liquid crystal display includes a control unit, an inverter and a load, and the control unit is configured to provide a plurality of control signals to the inverter according to an external image signal, the plurality of control signals including a plurality of first a control signal and a plurality of second control signals, wherein the control unit is capable of calculating a brightness value of the image corresponding to the received image signal, and when the calculation result satisfies a preset first reference brightness value, the backlight driving circuit is static The working state enters a dynamic working state. When the backlight driving circuit is in a static working state, the plurality of first control signals are set by a user, the plurality of second control signals have a first duty ratio, and the backlight driving circuit is in dynamic operation. In the state, the plurality of first control signals are provided by the adjusting unit according to the brightness value of the image corresponding to the received image signal, and the plurality of second control signals have a second duty ratio, the first duty Ratio is greater than the second a duty ratio, the inverter is configured to adjust an operating current of the load according to the plurality of control signals, and the inverter provides an adjustment current to the load according to the plurality of first control signals and the plurality of second control signals, The adjustment current can adjust the operating current of the load. The liquid crystal display of claim 17, wherein the plurality of first control signals are used to adjust a duty ratio of the adjustment current, and the plurality of second control signals are used to adjust a magnitude of the adjustment current. The liquid crystal display of claim 18, wherein when the brightness of the image corresponding to the image signal received by the control unit is small, the duty ratio of the first control signal and the second control signal is decreased. . The liquid crystal display according to claim 18, wherein when the brightness of the image corresponding to the image signal received by the control unit is small, the duty ratio and the amplitude of the adjustment current are decreased, and the load works. The current is reduced. The liquid crystal display of claim 18, wherein the plurality of control signals further comprise a plurality of third control signals, wherein the plurality of third control signals are used to adjust the frequency of the adjustment current. The liquid crystal display of claim 17, wherein the load is a plurality of cold cathode tubes. A liquid crystal display driving method, the liquid crystal display comprises a control unit, an inverter and a load, the method comprising: receiving an image signal; calculating a brightness value of the image corresponding to the received image signal, when the calculation result satisfies a The backlight driving circuit when the first reference brightness value is preset Entering a dynamic working state from a static working state; providing a first control signal and a second control signal according to the image brightness value, wherein the first control signal is set by a user when the backlight driving circuit is in a static working state, the second control The signal has a first duty ratio. When the backlight driving circuit is in a dynamic working state, the first control signal is provided by the adjusting unit according to the brightness value of the image corresponding to the received image signal, and the second control signal has a second duty ratio, the first duty ratio is greater than the second duty ratio; adjusting the luminous intensity of the load according to the first control signal and the second control signal. The liquid crystal display driving method of claim 23, wherein an adjustment current is provided, and an operating current of the load is adjusted according to the adjustment current. The liquid crystal display driving method of claim 23, wherein the first control signal is used to determine a duty ratio of the adjustment current, and the second control signal is used to determine a magnitude of the adjustment current.