TWI420494B - Liquid crystal display and dimming method and dimming device for backlight module - Google Patents

Description

Dimming method and device for liquid crystal display and backlight module

The invention relates to a dimming technology of a backlight module, and in particular to a dimming technology of a backlight module of a liquid crystal display.

Due to its advantages of lightness, thinness, power saving, no radiation, and low electromagnetic interference, LCD monitors are widely used in desktop computer screens, mobile phones, notebook computers, personal digital assistants (PDAs), digital cameras, and digital devices. Various electronic products such as cameras. With the rise of environmental awareness, the power-saving technology of liquid crystal displays has also received more and more attention.

In the background art, the earliest backlight module is in a normally bright state, and the power consumption of the backlight module is large. In view of this, it is proposed in the prior art that the liquid crystal display can control the brightness of the backlight module according to the gray scale value of the picture to be displayed. As the grayscale value of the display screen is brighter, the brightness of the backlight module will also increase; as the grayscale value of the display screen is darker, the brightness of the backlight module will also decrease. In this way, the power consumption of the backlight module can be reduced.

It is worth mentioning that in the prior art, if the brightness of the backlight module is adjusted according to the gray scale value of a single pixel, it is easy to misjudge the bright picture as a dark picture or misjudge the dark picture as a bright picture. If the brightness of the backlight module is adjusted according to the average grayscale value of all pixels The amount of computation will increase dramatically, which will not only consume power but also increase hardware costs.

For example, FIG. 1 is a schematic diagram of a liquid crystal display of the prior art. The timing controller 101 can receive the grayscale values of the pixels in the screen displayed by the system power supply VCC and the display panel 104. The calculation circuit in the timing controller 101 calculates the average grayscale value of the entire display screen according to the grayscale values of the respective pixels. The timing controller 101 then converts the pulse width modulation signal PWM1 into a pulse width modulation signal PWM2 according to the average grayscale value. The converter 102 controls the brightness and darkness of the backlight module 103 according to the system power supply VCC' and the pulse width modulation signal PWM2. This architecture complicates the circuit in the timing controller 101, increasing its area, thereby increasing the cost.

The invention provides a liquid crystal display, which can control the brightness of the backlight according to the instantaneous current value of the display panel.

The invention provides a dimming device applicable to a backlight module, which can save power consumption of the backlight module.

The invention provides a dimming method for a backlight module, which can save power consumption of the backlight module.

The invention provides a liquid crystal display, which comprises a display panel, a detector, a backlight module and a dimming circuit. The display panel can be used to display the picture. The detector is coupled to the display panel and can be used to detect the instantaneous current value of the display panel, thereby estimating the average grayscale value of the image. The dimming circuit is coupled to the backlight module and the detector, and the brightness of the backlight emitted by the backlight module can be adjusted according to the instantaneous current value of the display panel, so that the brightness of the backlight is proportional to or inversely proportional to the average gray level value of the above picture.

In an embodiment of the invention, if the display panel is in a normal white screen mode, the backlight brightness is proportional to the average grayscale value of the screen. If the display panel is in a normal black screen mode, the backlight brightness is inversely proportional to the average grayscale value of the above picture.

In an embodiment of the invention, the display panel includes a pixel unit, a source driver, and a gate driver. The pixel unit includes a plurality of pixel transistors. The source driver is coupled to the source of each pixel transistor. The gate driver is coupled to the gate of each pixel transistor.

In an embodiment of the invention, the detector includes first to fifth resistors and a voltage gain amplifier. The first end of the first resistor is coupled to the system power supply. The second end of the first resistor is coupled to the display panel. The resistance of the first resistor is no more than 10 ohms. The current flowing through the first resistor is proportional to the instantaneous current value described above. The detector can estimate the average grayscale value by using a voltage across the first end and the second end of the first resistor. The first end of the second resistor is coupled to the first end of the first resistor. The first end of the third resistor is coupled to the second end of the second resistor. The second end of the third resistor is coupled to the first voltage. The positive input end of the voltage gain amplifier is coupled to the first end of the third resistor. The first end of the fourth resistor is coupled to the second end of the first resistor. The second end of the fourth resistor is coupled to the negative input of the voltage gain amplifier. The first end of the fifth resistor is coupled to the second end of the fourth resistor. The second end of the fifth resistor is coupled to the output of the voltage gain amplifier.

In an embodiment of the invention, the dimming circuit includes a pulse width modulation circuit, a reaction time adjustment circuit, and a phase adjustment circuit. The pulse width modulation circuit is coupled to the output end of the detector and receives the pulse width modulation signal for adjusting the pulse width of the pulse width modulation signal. The reaction time adjustment circuit is coupled to the pulse width modulation circuit for adjusting the reaction time of the pulse width modulation signal. The phase adjustment circuit is coupled to the reaction time adjustment circuit for controlling the phase of the pulse width modulation signal.

The dimming circuit includes first to twelfth transistors. The gate terminal of the first transistor is coupled to the output of the detector. The first end of the first transistor is coupled to the first voltage. The gate terminal of the second transistor receives the pulse width modulation signal. The first end of the second transistor is coupled to the second end of the first transistor. The gate terminal of the third transistor receives the pulse width modulation signal. The first end of the third transistor is coupled to the second end of the second transistor. The gate terminal of the fourth transistor is coupled to the output of the detector. The first end of the fourth transistor is coupled to the second end of the third transistor. The second end of the fourth transistor is coupled to the second voltage. The gate terminal of the fifth transistor is coupled to the second end of the fourth transistor. The first end of the fifth transistor is coupled to the first end of the first transistor. The gate terminal of the sixth transistor is coupled to the second end of the second transistor. The first end of the sixth transistor is coupled to the second end of the fifth transistor. The gate terminal of the seventh transistor is coupled to the second end of the second transistor. The first end of the seventh transistor is coupled to the second end of the sixth transistor. The gate terminal of the eighth transistor is coupled to the first end of the first transistor. The first end of the eighth transistor is coupled to the second end of the seventh transistor. The second end of the eighth transistor is coupled to the second end of the fourth transistor. The gate terminal of the ninth transistor is coupled to the second end of the sixth transistor. The first end of the ninth transistor is coupled to the first end of the first transistor. The gate terminal of the tenth transistor is coupled to the second end of the sixth transistor. The first end of the tenth transistor is coupled to the second end of the seventh transistor. The second end of the tenth transistor is coupled to the second end of the fourth transistor. The gate terminal of the eleventh transistor is coupled to the second end of the ninth transistor. The first end of the eleventh transistor is coupled to the first end of the first transistor. The gate terminal of the twelfth transistor is coupled to the second end of the ninth transistor. The first end of the twelfth transistor is coupled to the second end of the eleventh transistor. The second end of the twelfth transistor is coupled to the second end of the fourth transistor.

In an embodiment of the invention, the backlight module is a side-type backlight module.

From another point of view, the present invention provides a dimming device suitable for use in a backlight module. The dimming device includes a detector and a dimming circuit. The detector is coupled to the display panel and can be used to detect the instantaneous current value of the display panel to estimate the average grayscale value of the image. The dimming circuit is coupled to the backlight module and the detector, and the backlight brightness emitted by the backlight module can be adjusted according to the instantaneous current value of the display panel, so that the backlight brightness is proportional to or inversely proportional to the average grayscale value.

From another perspective, the present invention provides a dimming method for a backlight module, which includes detecting an instantaneous current value of a screen displayed by the display panel, thereby estimating an average grayscale value of the image. In addition, the brightness of the backlight emitted by the backlight module is adjusted according to the instantaneous current value of the above picture, so that the brightness of the backlight is proportional to or inversely proportional to the average gray level value of the above picture.

In an embodiment of the invention, the voltage across the first end and the second end of the resistor is detected, wherein the first end of the resistor is coupled to a system power supply, and the second end of the resistor is coupled to the display The current flowing through the resistor is proportional to the instantaneous current value described above. In addition, the voltage across the voltage is amplified by a voltage amplifier to generate a voltage. The duty cycle of the dimming signal can also be adjusted according to the voltage to change the brightness of the backlight.

Based on the above, the present invention can adjust the brightness of the backlight module according to the instantaneous current value of the display panel. In this way, the power consumption of the backlight module can be reduced.

The above described features and advantages of the invention will be apparent from the following description.

10‧‧‧LCD display

20‧‧‧ dimming device

21‧‧‧Detector

22‧‧‧ Dimming circuit

30, 103‧‧‧ backlight module

31‧‧‧Light source

40‧‧‧ display panel

51, 102‧‧‧ converter

101‧‧‧ timing controller

I _VCC ‧‧‧ Current

R1~R5‧‧‧ resistance

C1~C12‧‧‧O crystal

V1, V2‧‧‧ voltage

VCC1, VCC2, VCC, VCC'‧‧‧ system power supply

PWM, PWM'', PWM1, PWM2‧‧‧ pulse width modulation signal

S201, S202‧‧‧ steps of the dimming method of the backlight module

1 is a schematic view of a liquid crystal display of the prior art.

2A is a schematic diagram of a liquid crystal display in accordance with an embodiment of the present invention.

2B is a schematic diagram of a side-lit backlight module in accordance with an embodiment of the invention.

FIG. 3 is a flow chart of a dimming method of a backlight module according to an embodiment of the invention.

4 is a schematic diagram of a dimming device in accordance with an embodiment of the present invention.

5A-5C are schematic diagrams of adjusting a duty cycle of a pulse width modulation signal PWM according to an embodiment of the invention.

Conventionally, the brightness of the backlight module is controlled according to the red, green, and blue grayscale values of the displayed image, which may cause an increase in the amount of calculation or a misjudgment of the bright and dark images.

In contrast, the embodiment of the present invention can detect the instantaneous current value of the display panel by using a resistor coupled between a system power supply and the display panel, and adjust the brightness of the backlight module accordingly. It is assumed that the display panel is in a normally white display mode. The larger the voltage difference of the pixel units applied in the display panel, the darker the picture; the smaller the voltage difference applied to the pixel elements in the display panel, the brighter the picture. That is to say, the darker the overall picture, the larger the instantaneous current value of the display panel; the brighter the overall picture, the smaller the instantaneous current value of the display panel. Therefore, the instantaneous current value of the display panel can be used to indicate the average grayscale value of the picture.

According to the above, since the resistor is coupled between a system power supply and the display panel, the current flowing through the resistor reflects the instantaneous current value of the display panel. In other words, flowing through the above The current of the resistor is proportional to the instantaneous current value described above. The greater the current flowing through the resistor, the greater the cross-over voltage across the resistor; conversely, the smaller the current flowing through the resistor, the smaller the cross-over voltage across the resistor. Embodiments of the present invention can detect the instantaneous current value of the display panel by detecting the voltage across the two ends of the resistor, and thereby controlling the brightness of the backlight module. As the instantaneous current value of the display panel is larger (dark screen), the brightness of the backlight module is darker; as the instantaneous current value of the display panel is smaller (bright picture), the brightness of the backlight module is brighter. In this way, the power consumption of the backlight module can be reduced. In addition, compared with the above-mentioned prior art, not only the amount of calculation but also the cost of hardware can be reduced. In addition, the above resistor can be selected with a small resistance value and used with a voltage gain amplifier to amplify the voltage across the small resistance value, thereby controlling the brightness of the backlight module, which can effectively reduce power consumption.

Similarly, assume that the display panel is in a normally black display mode. The larger the voltage difference of the pixel units applied in the display panel, the brighter the picture; the smaller the voltage difference of the pixel units applied in the display panel, the darker the picture will be. That is to say, the brighter the overall picture, the larger the instantaneous current value of the display panel; the darker the overall picture, the smaller the instantaneous current value of the display panel. Therefore, as the instantaneous current value of the display panel is larger (bright picture), the brightness of the backlight module is adjusted brighter; as the instantaneous current value of the display panel is smaller (dark picture), the brightness of the backlight module is adjusted. dark. In this way, the power consumption of the backlight module can be reduced. In addition, compared with the above-mentioned prior art, not only the amount of calculation but also the cost of hardware can be reduced. The embodiments of the present invention are explained in detail below with reference to the accompanying drawings, in which FIG.

2A is a schematic diagram of a liquid crystal display in accordance with an embodiment of the present invention. liquid crystal The display 10 can include a dimming device 20, a backlight module 30, a display panel 40, and a converter 51. The dimming device 20 can include a detector 21 and a dimming circuit 22. The display panel 40 can include a pixel unit (not shown), a source driver (not shown), and a gate driver (not shown). The pixel unit includes a plurality of pixel transistors (not shown). The source driver is coupled to the source of each pixel transistor. The gate driver is coupled to the gate of each pixel transistor.

System power supply VCC1 is available for display panel 40. The backlight module 30 is disposed under the display panel 40 and can be used to generate a backlight for use by the display panel 40. The converter 51 is coupled to the backlight module 30 to receive the system power supply VCC2 and to provide power to the backlight module 30. The detector 21 includes a resistor (not shown). The first end of the resistor is coupled to the system power supply VCC1, and the second end of the resistor is coupled to the display panel 40. The detector 21 can indirectly detect the instantaneous current value of the display panel 40 by using the above resistor. The dimming circuit 22 is coupled to the detector 21 and the converter 51. The converter 51 can be controlled according to the instantaneous current value of the display panel 40 measured by the detector 21, and the brightness of the backlight module 30 can be adjusted accordingly.

In this embodiment, the backlight module 30 is a side-type backlight module. 2B is a schematic diagram of a side-lit backlight module in accordance with an embodiment of the invention. Referring to FIG. 2B , the backlight module 30 includes a plurality of light sources 31 . The light source 31 is provided with a backlight to the display panel 40 in a side-by-side light input mode.

FIG. 3 is a flow chart of a dimming method of a backlight module according to an embodiment of the invention. Referring to FIG. 2A and FIG. 3 together, firstly, in step S201, the detector 21 displays a real-time current value of a picture by using a resistance detecting display panel 40, thereby estimating an average grayscale value of the picture.

Then, in step S202, the dimming circuit 22 adjusts the backlight brightness emitted by the backlight module 30 according to the instantaneous current value of the display panel 40, so that the backlight brightness is proportional to or inversely proportional to the average grayscale value of the screen.

Please note that in the present embodiment, the display panel 40 is described by taking a normal black screen type as an example. When the display panel 40 displays a white screen, the liquid crystal molecules of each pixel need to be rotated a lot, and therefore it is necessary to apply a large voltage difference to the pixel unit. Therefore, the display panel 40 displays a bright screen to consume power than a dark screen. In addition, since the liquid crystal display 10 generally employs a liquid crystal inversion technique, such as dot inversion, the display panel 40 also needs a large instantaneous current value to maintain a bright picture.

In the above, the dimming circuit 22 can adjust the backlight brightness of the backlight module 30 according to the instantaneous current value of the display panel 40 measured by the detector 21. When the bright picture is displayed, the brightness of the backlight is enhanced; when the dark picture is displayed, the brightness of the backlight is reduced. Therefore, the power consumption of the backlight module 30 can be reduced. In addition, compared with the prior art, the embodiment does not need to calculate the grayscale value of each pixel in the picture, which can reduce the amount of calculation and save hardware cost. The specific embodiments of several dimming devices 20 are disclosed below for those skilled in the art.

4 is a schematic diagram of a dimming device in accordance with an embodiment of the present invention. The dimming device 20 includes a detector 21 and a dimming circuit 22. The function of the detector 21 is to change the detected instantaneous current value Ivcc of the display panel 40 through the small resistance R1 to the voltage variation ΔV, and then the voltage gain amplifier ΔV is amplified by the voltage gain amplifier OP. The voltage VA that can be input to the dimming circuit 22 is reached. The main function of the dimming circuit 22 is to control the duty cycle of the pulse width modulation signal PWM by using the voltage VA in the detector 21. The detector 21 includes resistors R1 R R5 and a voltage gain amplifier OP. First end coupling system of resistor R1 Power supply VCC1. The second end of the resistor R1 is coupled to the display panel 40. The first end of the resistor R2 is coupled to the first end of the resistor R1. The first end of the resistor R3 is coupled to the second end of the resistor R2. The second end of the resistor R3 is coupled to the ground voltage. The positive input terminal of the voltage gain amplifier OP is coupled to the first end of the resistor R3. The first end of the resistor R4 is coupled to the second end of the resistor R1. The second end of the resistor R4 is coupled to the negative input terminal of the voltage gain amplifier OP. The first end of the resistor R5 is coupled to the second end of the resistor R4. The second end of the resistor R5 is coupled to the output of the voltage gain amplifier OP.

In the present embodiment, the resistance of the resistor R1 is 1 Ω, the resistance of the resistors R2 and R4 is 10K Ω, and the resistances of the resistors R3 and R5 are identical to each other, but the invention is not limited thereto. Those skilled in the art can change the resistance of each resistor according to their needs. Please note that the smaller the resistance of resistor R1, the smaller the power loss will be.

Note that the current I _VCC flowing through the resistor R1 is proportional to the instantaneous current value of the display panel. As the current I _VCC changes, the voltage across the resistor R1 will also change. The voltage gain amplifier OP can amplify the two ends of the resistor R1 across the voltage ΔV to a voltage VA, and accordingly control the dimming circuit 22. Those skilled in the art can adjust the resistance values of the resistors R3 and R5 according to their needs, thereby controlling the amplification factor of the voltage gain amplifier OP.

The dimming circuit 22 can include three parts, a pulse width modulation circuit, a reaction time adjustment circuit, and a phase adjustment circuit. The pulse width modulation circuit includes transistors C1, C4. The reaction time adjustment circuit includes transistors C5, C8. The phase adjustment circuit includes transistors C2, C3, C6, C7, C9~C12.

The gate terminal of the transistor C1 is coupled to the output of the voltage gain amplifier OP. The first end of the transistor C1 is coupled to the voltage V1, wherein the voltage V1 is, for example, a positive voltage. Gate of transistor C2 The terminal receives the pulse width modulation signal PWM. The first end of the transistor C2 is coupled to the second end of the transistor C1. The gate terminal of the transistor C3 receives the pulse width modulation signal PWM. The first end of the transistor C3 is coupled to the second end of the transistor C2. The gate terminal of transistor C4 is coupled to the output of voltage gain amplifier OP. The first end of the transistor C4 is coupled to the second end of the transistor C3. The second end of the transistor C4 is coupled to the voltage V2, wherein the voltage V2 is, for example, a ground voltage.

The gate terminal of the transistor C5 is coupled to the second end of the transistor C4. The first end of the transistor C5 is coupled to the first end of the transistor C1. The gate terminal of the transistor C6 is coupled to the second end of the transistor C2. The first end of the transistor C6 is coupled to the second end of the transistor C5. The gate terminal of the transistor C7 is coupled to the second end of the transistor C2. The first end of the transistor C7 is coupled to the second end of the transistor C6. The gate terminal of the transistor C8 is coupled to the first end of the transistor C1. The first end of the transistor C8 is coupled to the second end of the transistor C7. The second end of the transistor C8 is coupled to the second end of the transistor C4.

The gate terminal of the transistor C9 is coupled to the second end of the transistor C6. The first end of the transistor C9 is coupled to the first end of the transistor C1. The gate terminal of the transistor C10 is coupled to the second end of the transistor C6. The first end of the transistor C10 is coupled to the second end of the transistor C7. The second end of the transistor C10 is coupled to the second end of the transistor C4. The gate terminal of the transistor C11 is coupled to the second end of the transistor C9. The first end of the transistor C11 is coupled to the first end of the transistor C1. The gate terminal of the transistor C12 is coupled to the second end of the transistor C9. The first end of the transistor C12 is coupled to the second end of the transistor C11. The second end of the transistor C12 is coupled to the second end of the transistor C4.

The pulse width modulation circuit can be used to adjust the pulse width of the pulse width modulation signal PWM, and can also determine the length of time during which the pulse width modulation signal PWM rises or falls, that is, determines the size of the duty cycle. The reaction time adjustment circuit can be used to adjust the reaction time of the pulse width modulation signal PWM, and the time for the pulse width modulation signal PWM to rise or fall can be accelerated. Phase adjustment The circuit can be used to control the phase of the pulse width modulation signal PWM to generate the pulse width modulation signal PWM, and it can also determine whether the duty cycle is proportional or inverse. The transistors C2~C3, C6~C7, C9~C10, and C11~C12 are inverters. Please note that the transistors C2~C3, C6~C7, C9~C10, C11~C12 also have a buffer function. In the present embodiment, the transistors C1, C2, C5, C6, C9 and C11 are, for example, P-channel transistors. The transistors C3, C4, C7, C7, C10 and C12 are, for example, N-channel transistors. The P-channel transistor is a low-voltage start-up that controls the rise and fall of the PWM signal. That is, when the voltage is low, the pulse width modulation signal PWM rises faster. The N-channel transistor is a high-voltage start-up that controls the speed at which the PWM signal falls, that is, when the voltage is high, the pulse width modulation signal PWM falls faster. For example, FIG. 5A to FIG. 5C are schematic diagrams of adjusting the duty cycle of the pulse width modulation signal PWM according to an embodiment of the invention. FIG. 5A is a schematic diagram of a waveform before the duty cycle of the pulse width modulation signal is adjusted. If the current Ivcc rises, the voltage VA rises, the N-channel transistor turn-on time becomes faster, and the pulse width modulation signal PWM decreases faster, and a signal as shown in FIG. 5B appears. The transistors C1 and C4 determine the length of time during which the curves in the dashed boxes D1 and D2 in Fig. 5B rise and fall. The function of transistors C5 and C8 is to convert the waveform of Figure 5B into a standard waveform as shown in Figure 5C.

The converter 51 determines whether to supply the system power supply VCC2 to the backlight module 30 based on the pulse width modulation signal PWM''. More specifically, if the duty cycle of the pulse width modulation signal PWM'' is 40%, 40% of the time converter 51 will provide the system power supply VCC2 to the backlight module 30 in one cycle, 60% of the time. The converter 51 does not provide the system power supply VCC2 to the backlight module 30. Therefore, during the above period, the backlight module 30 will be illuminated 40% of the time, and will not be illuminated 60% of the time. Since the pulse width modulation signal PWM'' is positively and negatively cycled at a relatively fast speed, the human eye does not see that the backlight module 30 is flickering. In the case, only the brightness of the backlight module 30 is different. Therefore, by changing the duty cycle of the pulse width modulation signal PWM', the brightness of the backlight module 30 also changes.

Although a dimming method and apparatus for a liquid crystal display and a backlight module have been drawn in the above embodiments, those skilled in the art should know that various manufacturers are interested in liquid crystal displays and backlight modules. The dimming method is different from the design of the device, so the application of the present invention is not limited to such a possible form. In other words, as long as the brightness of the backlight module is adjusted according to the instantaneous current value of the display panel, it is in line with the spirit of the present invention. In the following, several embodiments will be described to enable those skilled in the art to further understand the spirit of the invention and to practice the invention.

Although the display panel 40 in the above embodiment has been described with a normal black screen type as an example, the present invention is not limited thereto. In other embodiments, display panel 40 can also be a normal white screen type. For example, if the display panel 40 is in a normal white screen mode. When the display panel 40 displays a dark screen, the liquid crystal molecules of each pixel need to be rotated greatly, so that it is necessary to apply a large voltage difference to the pixel unit, so that the display panel 40 displays a dark screen to consume power than a bright screen. In addition, since the liquid crystal display 10 generally employs a liquid crystal inversion technique, the display panel 40 requires a large instantaneous current value to maintain a dark picture.

In the above, the dimming circuit 22 can adjust the backlight brightness of the backlight module 30 according to the instantaneous current value of the display panel 40 measured by the detector 21. When the bright picture is displayed, the brightness of the backlight is enhanced; when the dark picture is displayed, the brightness of the backlight is reduced. In this way, similar effects to the above embodiments can be achieved.

The dimming device 20 of FIG. 4 in the above embodiment is only an alternative embodiment, and the invention is not limited thereto. Those skilled in the art can also change the implementation of dimming device 20 as desired. For example, the detector 21 can also be a Hall sensor.

Further, although the above embodiment uses the duty cycle of changing the pulse width modulation signal PWM'' to change the brightness of the backlight module 30, the present invention is not limited thereto. In other embodiments, if the backlight module 30 is composed of a plurality of light emitting elements, the brightness of the backlight module 30 can be controlled by driving a different number of light emitting elements.

In summary, the present invention can adjust the brightness of the backlight module according to the instantaneous current value of the display panel. In this way, the power consumption of the backlight module can be reduced. Compared with the above-mentioned prior art, the amount of calculation can be reduced and the cost of hardware can be reduced.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention, and those skilled in the art can make some changes and refinements without departing from the spirit and scope of the present invention. The scope of the invention is defined by the scope of the appended claims.

10‧‧‧LCD display

20‧‧‧ dimming device

21‧‧‧Detector

22‧‧‧ Dimming circuit

30‧‧‧Backlight module

40‧‧‧ display panel

51‧‧‧ converter

VCC1, VCC2‧‧‧ system power supply

PWM, PWM''‧‧‧ pulse width modulation signal

Claims (17)

A liquid crystal display comprising: a display panel for displaying a picture; a detector coupled to the display panel for detecting an instantaneous current value of the display panel, thereby estimating an average gray level of the picture The first detector has a first end coupled to a system power supply, and a second end of the first resistor is coupled to the display panel, wherein a current flowing through the first resistor is The above-mentioned detector uses a voltage between the first end and the second end of the first resistor to estimate the average gray scale value; a backlight module; and a dimming circuit coupled The backlight module and the detector are connected to adjust a brightness of the backlight emitted by the backlight module according to the instantaneous current value, so that the brightness of the backlight is proportional to or inversely proportional to the average gray level value. The liquid crystal display according to claim 1, wherein if the display panel is in a normal white mode, the backlight brightness is proportional to the average grayscale value; if the display panel is a normal black screen type, the backlight is The brightness is inversely proportional to the above average gray level value. The liquid crystal display of claim 1, wherein the display panel comprises: a pixel unit comprising a plurality of pixel transistors; and a source driver coupled to the sources of the pixel cells; as well as A gate driver is coupled to the gates of the pixel transistors. The liquid crystal display of claim 1, wherein the detector further includes: a second resistor having a first end coupled to the first end of the first resistor; a third resistor, the first The second end of the third resistor is coupled to the second end of the second resistor; the voltage gain amplifier has a positive input end coupled to the first end of the third resistor; and a fourth resistor, the first end The second end of the fourth resistor is coupled to the negative input end of the voltage gain amplifier; and the fifth end is coupled to the second end of the fourth resistor The second end of the fifth resistor is coupled to the output end of the voltage gain amplifier. The liquid crystal display of claim 1, wherein the resistance of the first resistor is not more than 10 ohms. The liquid crystal display of claim 1, wherein the dimming circuit comprises: a pulse width modulation circuit coupled to the output end of the detector and receiving a pulse width modulation signal for adjusting The pulse width modulation signal has a pulse width; a reaction time adjustment circuit coupled to the pulse width modulation circuit for adjusting the reaction time of the pulse width modulation signal; and a phase adjustment circuit coupled to the reaction time An adjustment circuit for controlling the phase of the pulse width modulation signal. The liquid crystal display of claim 1, wherein the dimming circuit comprises: a first transistor having a gate terminal coupled to an output end of the detector, the first The first end of the crystal is coupled to a first voltage; the second transistor has a gate terminal receiving the pulse width modulation signal, and the first end of the second transistor is coupled to the second end of the first transistor; a third transistor having a gate terminal receiving the pulse width modulation signal, a first end of the third transistor coupled to the second end of the second transistor; a fourth transistor having a gate terminal coupled thereto The second end of the fourth transistor is coupled to the second end of the third transistor, the second end of the fourth transistor is coupled to a second voltage, and a fifth transistor is coupled to the output end of the detector. The gate end is coupled to the second end of the fourth transistor, the first end of the fifth transistor is coupled to the first end of the first transistor; the sixth transistor is coupled to the second end a second end of the sixth transistor, the first end of the sixth transistor is coupled to the second end of the fifth transistor; a seventh transistor having a gate end coupled to the second end of the second transistor, a first end of the seventh transistor is coupled to the second end of the sixth transistor; an eighth transistor, The first end of the first transistor is coupled to the second end of the first transistor, the second end of the eighth transistor is coupled to the second end of the seventh transistor, and the second end of the eighth transistor is coupled to the fourth transistor a second end; a ninth transistor having a gate terminal coupled to the second end of the sixth transistor, a first end of the ninth transistor coupled to the first end of the first transistor; a transistor having a gate terminal coupled to the second end of the sixth transistor, a first end of the tenth transistor coupled to the second end of the seventh transistor, and a second end of the tenth transistor coupled a second end of the fourth transistor; an eleventh transistor having a gate terminal coupled to the second end of the ninth transistor; a first end of the eleventh transistor coupled to the first transistor First end; a twelfth transistor having a gate terminal coupled to the second end of the ninth transistor, a first end of the twelfth transistor coupled to the second end of the eleventh transistor, the twelfth The second end of the crystal is coupled to the second end of the fourth transistor. The liquid crystal display according to claim 1, wherein the backlight module is a side backlight module. A dimming device is applied to a backlight module. The dimming device includes a detector coupled to a display panel for detecting an instantaneous current value of the display panel to estimate the image. An average grayscale value; wherein the detector includes: a first resistor, the first end of which is coupled to a system power supply, and the second end of the first resistor is coupled to the display panel, wherein the first a current of the resistor is proportional to the instantaneous current value, wherein the detector uses the voltage across the first end and the second end of the first resistor to estimate the average gray level value; and a dimming circuit coupled The backlight module and the detector are connected to adjust a brightness of the backlight emitted by the backlight module according to the instantaneous current value, so that the brightness of the backlight is proportional to or inversely proportional to the average gray level value. The dimming device of claim 9, wherein if the display panel is in a normal white mode, the backlight brightness is proportional to the average grayscale value; if the display panel is a normal black screen type, The backlight brightness is inversely proportional to the above average grayscale value. The dimming device of claim 10, wherein the detector further comprises: a second resistor, the first end of which is coupled to the first end of the first resistor; a third resistor having a first end coupled to the second end of the second resistor, the second end of the third resistor being grounded; a voltage gain amplifier having a positive input coupled to the first end of the third resistor; a fourth resistor, the first end of which is coupled to the second end of the first resistor, the second end of the fourth resistor is coupled to the negative input end of the voltage gain amplifier, and a fifth resistor is coupled to the first end Connected to the second end of the fourth resistor, the second end of the fifth resistor is coupled to the output end of the voltage gain amplifier. The dimming device of claim 9, wherein the dimming circuit comprises: a pulse width modulation circuit coupled to the output end of the detector and receiving a pulse width modulation signal for Adjusting a pulse width of the pulse width modulation signal; a reaction time adjustment circuit coupled to the pulse width modulation circuit for adjusting a reaction time of the pulse width modulation signal; and a phase adjustment circuit coupled to the reaction a time adjustment circuit for controlling the phase of the pulse width modulation signal. The dimming device of claim 9, wherein the dimming circuit comprises: a first transistor having a gate terminal coupled to an output end of the detector, a first end of the first transistor a first transistor is coupled to the first voltage; a second transistor has a gate terminal receiving the pulse width modulation signal, and a first end of the second transistor is coupled to the second end of the first transistor; a third transistor The gate terminal receives the pulse width modulation signal, the first end of the third transistor is coupled to the second end of the second transistor; and the fourth transistor has a gate terminal coupled to the output of the detector End, the fourth electric a first end of the crystal is coupled to the second end of the third transistor, a second end of the fourth transistor is coupled to a second voltage, and a fifth transistor is coupled to the fourth transistor. a second end, the first end of the fifth transistor is coupled to the first end of the first transistor; a sixth transistor is coupled to the second end of the second transistor, the sixth a first end of the crystal is coupled to the second end of the fifth transistor; a seventh transistor is coupled to the second end of the second transistor, and the first end of the seventh transistor is coupled to the first end a second end of the sixth transistor; an eighth transistor having a gate terminal coupled to the first end of the first transistor, and a first end of the eighth transistor coupled to the second end of the seventh transistor a second end of the eighth transistor is coupled to the second end of the fourth transistor; a ninth transistor having a gate terminal coupled to the second end of the sixth transistor, the ninth transistor One end is coupled to the first end of the first transistor; a tenth transistor is coupled to the sixth electro-crystal The second end of the tenth transistor is coupled to the second end of the seventh transistor, and the second end of the tenth transistor is coupled to the second end of the fourth transistor; a transistor having a gate terminal coupled to the second end of the ninth transistor, a first end of the eleventh transistor coupled to the first end of the first transistor, and a twelfth transistor The gate end is coupled to the second end of the ninth transistor, the first end of the twelfth transistor is coupled to the second end of the eleventh transistor, and the second end of the twelfth transistor is coupled to the second end The second end of the fourth transistor. The dimming device of claim 9, wherein the backlight module is a side backlight module. A dimming method for a backlight module, comprising: Detecting a display panel to display an instantaneous current value of a picture, thereby estimating an average gray level value of the image; and adjusting a backlight brightness emitted by the backlight module according to the instantaneous current value to make the backlight brightness and the above The average grayscale value is proportional or inversely proportional; wherein if the display panel is a normal white screen type, the backlight brightness is proportional to the average grayscale value; if the display panel is a normal black screen type, the backlight brightness and the average The grayscale value is inversely proportional. The dimming method of claim 15, wherein the step of detecting the instantaneous current value of the screen by the display panel to estimate the average grayscale value of the image comprises: detecting a resistance a voltage across the first end and the second end, wherein the first end of the resistor is coupled to a system power supply, and the second end of the resistor is coupled to the display panel, and a current flowing through the resistor and the instantaneous current value Directly proportional; and amplifying the above-mentioned voltage across a voltage amplifier to generate a voltage. The dimming method of claim 16, wherein the step of adjusting the brightness of the backlight emitted by the backlight module according to the instantaneous current value to make the backlight brightness proportional to or inversely proportional to the average gray level value includes : adjusting a duty cycle of the dimming signal according to the voltage to change the brightness of the backlight.