TWI415090B - Brightness adjusting apparatus and method for dynamically adjusting brightness of backlight module - Google Patents

Abstract

The invention provides a brightness adjusting apparatus comprising a storing unit, a receiving/processing unit connected to the storing unit, and an output unit connected to the receiving/processing unit. The storing unit stores a lookup table corresponding to an adjusting curve representing the relationship between duty cycle and reference value. The adjusting curve is a gamma curve with a stop point thereon, and the slopes on two sides of the stop point of the adjusting curve are not continuous. The receiving/processing unit compares the reference value of a frame data with the lookup table to obtain the duty cycle corresponding to the reference value, and then the output unit generates a pulse-width modulation signal according to the duty cycle to dynamically adjust the brightness of the backlight module.

Description

Brightness adjusting device and method for dynamically adjusting brightness of backlight module

The present invention relates to a brightness adjusting device and a method for dynamically adjusting the brightness of a backlight module, and in particular, the present invention relates to a brightness adjusting device capable of improving the picture quality of a dynamic backlight technology and a method for dynamically adjusting the brightness of the backlight module.

Compared with the conventional cathode ray tube (CRT) display, the liquid crystal display has the advantages of small volume, low power consumption, low radiation and the like. Through the development of all walks of life, LCD monitors have become one of the mainstream monitors on the market.

The liquid crystal panel of the liquid crystal display itself does not emit light, but the light emitted by the backlight module disposed on the back surface of the liquid crystal panel penetrates the liquid crystal panel to allow the user to observe the light emitting effect. In general electronic products, such as LCD TVs, computer screens, mobile phones or notebook computers, the maximum power consumption of the liquid crystal display used is its backlight module. Therefore, the power saving technology of the backlight module becomes the energy saving of the liquid crystal display. The essential.

In the prior art, a light-emitting diode (LED) having a lower energy consumption has been used as a light-emitting unit of a backlight module, and a backlight backlight module (Dynamic Backlight Control, DBC) is used to reduce the consumption of the backlight module. The way to do it. Referring to FIG. 1, FIG. 1 is a schematic diagram showing a prior art dynamic backlight control system 1. As shown in FIG. 1 , the dynamic backlight control system 1 includes a dynamic backlight control unit 10 and an LED backlight. The module 12, wherein the LED backlight module 12 is coupled to the dynamic backlight control unit 10 and can receive the illumination control signal 100 from the dynamic backlight control unit 10 to emit light. The dynamic backlight control unit 10 can receive the screen information 14 and process the screen information 14 to obtain the liquid crystal control signal 102 and the illumination control signal 100. The liquid crystal control signal 102 can be output to the liquid crystal panel 16 to control the liquid crystal deflection of the liquid crystal panel 16. The illumination control signal 100 can be output to the LED backlight module 12 to control the illumination of the LED backlight module 12.

The illumination control signal may be an analog control signal or a pulse width modulation signal (digital control signal). However, the analog control is more complicated than the digital control using the pulse width modulation signal, and may cause unstable LED characteristics. Therefore, the current dynamic backlight control technology is usually performed with a pulse width modulation signal. The LED backlight module can determine the time of illumination according to the duty ratio of the backlight opening time of the pulse width modulation signal. The pulse width modulation signal can be synchronized with the liquid crystal control signal to control the illumination of the backlight module according to different picture data, thereby achieving the purpose of dynamically saving the energy consumption of the backlight module.

For example, referring to FIG. 2, FIG. 2 is a characteristic diagram of the dynamic backlight control system 1 of FIG. 1 dynamically controlling the backlight module 10 by using a pulse width modulation signal. As shown in FIG. 2, the dynamic backlight control unit 10 can analyze the statistical value (for example, the maximum grayscale value in the picture data) in the picture data 14 and determine the reference point X of the picture data 14, and compare the reference point 14 and The characteristic curve F of FIG. 2 controls the backlight backlight opening time ratio Y of the pulse width modulation signal, thereby controlling the illumination characteristics of the backlight module. Since the dynamic backlight control unit 10 can determine the back according to different picture materials 14 The light-emitting characteristics of the light module, so it is a dynamic backlight control technology.

Since the above prior art uses the statistical value of the picture data (for example, the maximum gray level value) as a reference point to dynamically adjust the backlight module to emit light, when the picture has a drastic change (such as an explosion picture), backlight continuity will be caused. A large change in the cause of flicker. In the prior art, the method of reducing the sensitivity of the backlight change can be used to improve the backlight flicker phenomenon. However, this method will cause the change of the backlight to keep up with the change of the picture, resulting in a situation in which some pictures are mismatched (for example, originally required to be compared). High-brightness picture with low-brightness backlight). In addition, using the above improvements will also increase the complexity of the algorithm.

Therefore, one aspect of the present invention is to provide a brightness adjusting device capable of dynamically adjusting the brightness of a backlight module to solve the above problems.

According to a specific embodiment, the brightness adjusting device of the present invention comprises a storage unit, a receiving/processing unit and an output unit, wherein the receiving/processing unit is connected to the storage unit, and the output unit is connected to the receiving/processing unit. A comparison table is stored in the storage unit. The receiving/processing unit can receive the picture data and compare the reference table in the storage unit according to the reference value in the picture data to obtain a backlight opening time ratio corresponding to the reference value. The output unit can generate a pulse width modulation signal according to the ratio of the backlight on time.

In this embodiment, the comparison table stored by the storage unit may correspond to a modulation curve, and the modulation curve represents a correspondence between the ratio of the backlight opening time and the reference value. The modulation curve is a gamma curve and has At a stop loss point, the slopes on either side of the stop loss point are not continuous. When the reference value of the picture data is smaller than the reference value corresponding to the stop loss point, the ratio of the reference value of the picture data to the time backlight on time on the modulation curve is substantially maintained within a range. Therefore, the ratio of the backlight on time obtained by the receiving/processing unit does not cause the picture to flicker due to excessive changes.

One aspect of the present invention is to provide a method for dynamically adjusting the brightness of a backlight module.

According to a specific embodiment, the method for dynamically adjusting the brightness of the backlight module of the present invention may include the following steps: first, generating a pulse width modulation signal having a backlight on-time ratio according to a reference value and a comparison table; and then, according to a pulse width modulation The variable signal controls the brightness of the backlight module. The reference value is a numerical operation value in a picture data.

In this embodiment, the comparison table may correspond to a modulation curve, which represents a correspondence between the ratio of the backlight on time and the reference value. The modulation curve is a gamma curve with a stop point on it, and the slopes on both sides of the stop point are not continuous. When the reference value of the picture data is smaller than the reference value corresponding to the stop loss point, the ratio of the reference value of the picture data to the time backlight on time on the modulation curve is substantially maintained within a range. Therefore, the backlight turn-on time ratio of the pulse width modulation signal generated by the method of the embodiment does not cause the picture to flicker due to excessive change.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

Referring to FIG. 3, FIG. 3 is a schematic diagram of a brightness adjusting device 2 according to an embodiment of the present invention. The brightness adjusting device 2 can be used to dynamically adjust the brightness of the backlight module and improve the flicker phenomenon generated during dynamic adjustment. As shown in FIG. 3, the brightness adjusting device 2 includes a storage unit 20, a receiving/processing unit 22, and an output unit 24. The receiving/processing unit 22 is connected to the storage unit 20, and the output unit 24 is connected to the receiving/processing unit 22. Further, a lookup table 200 is stored in the storage unit 20.

In the present embodiment, the receiving/processing unit 22 can receive the picture material A and process the picture material A to obtain a numerical operation value in the picture material A as a reference value. For example, the receiving/processing unit can analyze the picture data to obtain the grayscale values required for each pixel in the picture data, and count the gray level values to find the largest gray level value as its reference value. Please note that the reference value in practice is not limited to the maximum grayscale value, depending on the user or designer's needs. The receiving/processing device 22 can compare the reference value to the look-up table 200 to obtain a backlight turn-on time ratio corresponding to the reference value, and the output unit 24 generates the pulse width modulation signal M according to the backlight turn-on time ratio. In practice, the pulse width modulation signal M can be further connected to the LED driver of the backlight module to drive the LED illumination. On the other hand, the brightness adjustment device 2 of the specific embodiment can also be directly established in the LED driver.

Please refer to FIG. 4A and FIG. 4B. FIG. 4A is a schematic diagram showing the brightness adjustment device 2 connected to the LED driver 3 according to another embodiment of the present invention, and FIG. 4B is a diagram showing another specific embodiment according to the present invention. A schematic diagram of the brightness adjustment device 4 of the embodiment. As shown in FIG. 4A, the brightness adjusting device 2 is a special application integrated circuit (Application-Specific Integrated Circuit (ASIC), whose output unit 24 is connected to the LED driver 3. The LED driver 3 can be a part of the backlight module in practice. When the LED driver 3 receives the pulse width modulation signal M generated by the output unit 24, the LED in the backlight module can be controlled according to the pulse width modulation signal M. Glowing.

As shown in FIG. 4B, in the present embodiment, the brightness adjusting device 4 itself is a part of an LED driver or an LED driver. The brightness adjusting device 4 also includes a storage unit 40, a receiving/processing unit 42 and an output unit 44, and the functions of the units are substantially the same as those of the unit corresponding to the above specific embodiment, and thus will not be described again. The difference between the specific embodiment and the above embodiment is that the pulse width modulation signal M generated by the output unit 44 of the specific embodiment is fed back to the brightness adjusting device 4 itself, and the brightness adjusting device 4 controls according to the modulation signal M. The LEDs (not shown in the figure) in the backlight module emit light.

In the above specific embodiment, the receiving/processing unit can receive picture information from the system side. For example, in a desktop computer or a notebook computer, the host transmits screen information corresponding to the screens to the receiving/processing unit of the brightness adjusting device in order to display certain screens on the liquid crystal screen. In addition, the comparison table stored in the storage unit of the above specific embodiment may correspond to a modulation curve, and the receiving/processing unit may find the backlight opening time ratio of the corresponding reference value according to the comparison table or the modulation curve.

Please refer to FIG. 5 , which is a schematic diagram of the modulation curve C1 corresponding to the comparison table 200 of FIG. 1 . As shown in FIG. 5, the modulation curve C1 represents the correspondence between the backlight opening time ratio D (Y axis) and the reference value R (X axis). relationship. In this embodiment, the reference value R may be the maximum grayscale value in the picture data, but the invention is not limited thereto. In practice, the reference value R may be a numerical value that can represent one of the brightness of the screen.

In this embodiment, the modulation curve C1 may be a gamma corrected gamma curve. In general, the user views the most comfortable gamma value 2.2, so the modulation curve C1 of the present embodiment is a gamma curve of the gamma value of 2.2, however, the invention is not limited thereto. There is a stop loss point P1 above the modulation curve C1, and the slope of the modulation curve C1 on both sides of the stop loss point P1 is discontinuous.

As shown in FIG. 5, the stop loss point P1 corresponds to the reference value R1 and the backlight open time ratio D1. The slope of the modulation curve C1 on the left side of the stop loss point P1 becomes small, and when the reference value approaches 0, the corresponding backlight on-time ratio remains within one of the backlight on-time ratios D1 rather than close to zero. Therefore, the ratio of the backlight turn-on time obtained by the receiving/processing unit according to the reference value in the screen information is not excessively changed, so that the light source emitted by the backlight module can be further prevented from frequently changing to cause flicker.

The above modulation curve C1 limits the minimum backlight turn-on time ratio, so that the backlight turn-on time ratio does not change too much. In practice, the modulation curve C1 can also limit the maximum backlight turn-on time ratio. For example, the modulation curve C1 on the left side of the stop loss point P1 may have a larger slope, and the modulation curve C1 on the right side of the stop loss point P1 may have a smaller slope. Thereby, when the reference value of the picture data is greater than the reference value R1, the ratio of the backlight on time obtained by the receiving/processing unit 22 in comparison with the comparison table 200 is maintained. Within the range of the backlight opening time ratio D1. Please note that in practice, the set position of the stop loss point P1 is determined according to the needs of the user or the designer, and is not limited to the specific embodiments listed in the present specification.

Referring to FIG. 3 and FIG. 6 together, FIG. 6 is a flow chart showing the steps of a method for dynamically adjusting the brightness of a backlight module according to an embodiment of the present invention. As shown in FIG. 6, the method for dynamically adjusting the brightness of the backlight module of the present invention includes the following steps: in step S50, obtaining a backlight on-time ratio corresponding to the reference value according to a reference value and a comparison table, and according to The obtained backlight opening time ratio generates a pulse width modulation signal; in step S52, the brightness of the backlight module is controlled according to the pulse width modulation signal.

Regarding step S50, the brightness adjusting device 2 of Fig. 3 can be described in detail as an example. The receiving/processing unit 22 can receive the picture information A and obtain the reference value from the picture information A. Then, the receiving/processing unit 22 compares the reference value in the comparison table 200 in the storage unit 20 to obtain the corresponding reference value. The ratio of backlight turn-on time. The output unit 24 generates a pulse width modulation signal M according to the ratio of the backlight on time obtained by the receiving/processing unit 22.

In step S52, the pulse width modulation signal generated in step S50 can be input to the LED driver to drive the LED of the backlight module to emit light, as shown in FIG. 4A. On the other hand, if the brightness adjusting device itself is part of the LED driver or the LED driver, in step S52, the pulse width modulation signal can be fed back to the LED driver to drive the LED of the backlight module to emit light, as shown in FIG. 4B.

The method for dynamically adjusting the brightness of the above specific embodiment, the comparison table can be Corresponding to a modulation curve, the modulation curve represents the correspondence between the backlight time ratio and the reference value. The modulation curve can be a gamma curve, and its slope on both sides of the stop loss point is discontinuous, as shown in Figure 5.

The above comparison table and the modulation curve can be completed by the device in the following manner. Please refer to FIG. 7A to D and FIG. 5 together. FIG. 7A is a flow chart showing steps of a method for establishing a comparison table according to an embodiment of the present invention, and FIG. 7B is a diagram showing steps in FIG. 7A. Schematic diagram of the unit, FIG. 7C to D show a schematic diagram of each corresponding curve formed by each step in FIG. Please note that the units shown in FIG. 7B may be disposed in the brightness adjusting device of the above specific embodiment, or may be independent of the brightness adjusting device, depending on the needs of the user or the designer, and the present invention does not Limit it. As shown in FIG. 7B, the second adjusting unit 72 is connected to the first adjusting unit 70; the third adjusting unit 74 is connected to the second adjusting unit 72; and the fourth adjusting unit 76 is connected to the third adjusting unit 74. In addition, the corresponding curves of FIG. 7C to D represent the correspondence relationship between the backlight opening time ratio D (Y axis) and the reference value R (X axis).

As shown in FIG. 7A and FIG. 7B, in step S60, the first adjusting unit 70 linearly matches the backlight on-time ratio D and the reference value R to obtain a linear first corresponding curve C2 (as shown in FIG. 7C). In step S62, the second adjusting unit 72 may set the first reference value R2, and obtain a first backlight opening time ratio D2 according to the first reference value R2 and the first corresponding curve C2, wherein the first reference value R2 and the first backlight The position of the opening time ratio D2 corresponding to the first corresponding curve C2 can be used as the stop loss point P2.

In step S64, the third adjusting unit 74 may change the backlight on-time ratio D corresponding to the reference value R that is smaller than the first reference value R2 on the first corresponding curve C2 to the first backlight-on time ratio D2, thereby obtaining the second Corresponding to curve C3 (as shown in Figure 7D). In step S66, the fourth adjusting unit 76 may perform gamma correction on the second corresponding curve C3 according to a gamma value to obtain a modulation curve C1 (as shown in FIG. 5). In addition, in step S66, the fourth adjusting unit 76 may further obtain a comparison table about the backlight opening time ratio D and the reference value R according to the modulation curve C1. In practice, the fourth adjustment unit may further connect the storage unit of the above specific embodiment to store the comparison table in the storage unit. By the above method, the comparison table and its corresponding modulation curve can be completed and stored in the storage unit of the above specific embodiment.

Compared with the prior art, the brightness adjusting device provided by the present invention and the method for dynamically adjusting the brightness of the backlight module can make the light source emitted by the backlight module not to be continuous due to the dramatic change of the screen by setting the stop loss point. Great changes, and thus avoid the phenomenon of flickering. Since the brightness adjusting device of the present invention and the method for dynamically adjusting the brightness of the backlight module do not reduce the sensitivity of the backlight change, there is no possibility that the backlight change cannot be changed with the screen change, causing some screen mismatching conditions to occur, and neither Will increase the complexity of the algorithm.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patent claimed by the present invention The scope should be interpreted broadly according to the above description so that it covers all possible changes and arrangements of equality.

1‧‧‧Dynamic backlight control system

10‧‧‧Dynamic backlight control unit

12‧‧‧LED backlight module

14‧‧‧ Screen Information

16‧‧‧LCD panel

100‧‧‧Lighting control signal

102‧‧‧LCD control signal

F‧‧‧ characteristic curve

X‧‧‧ benchmark

Y‧‧‧Backlight start time ratio

2, 4‧‧‧ brightness adjustment device

20, 40‧‧‧ storage unit

22, 42‧‧‧ receiving/processing unit

24, 44‧‧‧ Output unit

200, 400‧‧‧ comparison table

A‧‧‧ screen material

M‧‧‧ pulse width modulation signal

3‧‧‧LED driver

C1‧‧‧ modulation curve

C2‧‧‧ first corresponding curve

C3‧‧‧second correspondence curve

R, R1‧‧‧ reference value

D, D1‧‧‧ backlight opening time ratio

P1, P2‧‧‧ stop loss points

D2‧‧‧First backlight turn-on time ratio

R2‧‧‧ first reference value

70‧‧‧First adjustment unit

72‧‧‧Second adjustment unit

74‧‧‧ Third adjustment unit

76‧‧‧Fourth adjustment unit

S50~S52‧‧‧ Process steps

S60~S66‧‧‧ Process steps

Figure 1 is a schematic diagram showing a prior art dynamic backlight control system.

FIG. 2 is a characteristic diagram of the dynamic backlight control system of FIG. 1 dynamically controlling the backlight module by using a pulse width modulation signal.

Figure 3 is a schematic illustration of a brightness adjustment device in accordance with an embodiment of the present invention.

FIG. 4A is a schematic diagram showing the connection of an LED driver to a brightness adjusting device according to another embodiment of the present invention.

FIG. 4B is a schematic diagram showing a brightness adjusting device according to another embodiment of the present invention.

Figure 5 is a schematic diagram showing the modulation curve corresponding to the comparison table of Figure 1.

6 is a flow chart showing the steps of a method for dynamically adjusting the brightness of a backlight module according to an embodiment of the present invention.

Figure 7A is a flow chart showing the steps of a method for establishing a look-up table according to an embodiment of the present invention.

Figure 7B is a schematic diagram showing the units performing the steps in Figure 7A.

Figure 7C~D is a schematic diagram showing the corresponding curves formed by the steps in Figure 7A.

2‧‧‧Brightness adjustment device

20‧‧‧ storage unit

22‧‧‧Receiving/Processing Unit

24‧‧‧Output unit

200‧‧‧ comparison table

A‧‧‧ screen material

M‧‧‧ pulse width modulation signal

Claims (14)

A brightness adjusting device for dynamically adjusting the brightness of a backlight module, the brightness adjusting device comprising: a storage unit for storing a comparison table; a receiving/processing unit connecting the storage unit, the receiving/processing unit is for Receiving a picture data and obtaining a backlight turn-on time ratio according to one of the reference values in the picture data; and an output unit connected to the receiving/processing unit, the output unit is configured to turn on according to the backlight The ratio generates a pulse width modulation signal; wherein the comparison table stored by the storage unit corresponds to a modulation curve, and the modulation curve represents a correspondence between the ratio of the backlight opening time and the reference value, and the modulation curve is a gamma curve and having a stop loss point thereon, and the slope of the modulation curve on both sides of the stop loss point is discontinuous, the brightness adjusting device further comprises: a first adjusting unit, according to the backlight opening time a linear relationship between the ratio and the reference value obtains the first corresponding curve; a second adjusting unit connecting the first adjusting unit, the first The adjusting unit is configured to set a first reference value to obtain the stop loss point, and obtain a first backlight opening time ratio according to the first reference value and the first corresponding curve; and a third adjusting unit to connect the second adjustment a unit, the third adjusting unit is configured to change the ratio of the backlight on-time that matches the reference value that is less than the first reference value on the first corresponding curve to the first backlight on-time ratio to obtain the second Corresponding song And a fourth adjusting unit, connected to the third adjusting unit and the storage unit, wherein the fourth adjusting unit is configured to perform the gamma correction on the second corresponding curve according to a gamma value The curve is changed, and the fourth adjusting unit obtains the comparison table of the backlight opening time ratio and the reference value according to the modulation curve and stores the comparison table in the storage unit. The brightness adjusting device according to claim 1, wherein the modulation curve has a gamma value of 2.2. The brightness adjusting device according to claim 1, wherein the reference value is a numerical value calculated with respect to one of the picture materials. The brightness adjusting device of claim 3, wherein the numerical value is a maximum gray level value of one of the picture data. The brightness adjusting device according to claim 1, wherein the brightness adjusting device is an Application-Specific Integrated Circuit (ASIC). The brightness adjustment device of claim 5, wherein the output unit is coupled to a LED driver to output the pulse width modulation signal to the LED driver, and the LED is The polar body driver controls the brightness of the backlight module according to the pulse width modulation signal. The brightness adjusting device according to claim 1, wherein the brightness adjusting device is a light emitting diode driver. The brightness adjustment device of claim 7, wherein the pulse width modulation signal outputted by the output unit is fed back to the LED driver, and the LED driver adjusts the signal according to the pulse width. Control the brightness of the backlight module. A method for dynamically adjusting the brightness of a backlight module includes the steps of: generating a pulse width modulation signal having a backlight on-time ratio according to a reference value and a comparison table; and controlling the pulse width modulation signal according to the pulse width The brightness of the backlight module; wherein the comparison table corresponds to a modulation curve, the modulation curve represents a correspondence between the ratio of the backlight opening time and the reference value, and the modulation curve is a gamma curve and has thereon a stop point, and the slope of the modulation curve on both sides of the stop loss point is discontinuous, the method further comprising the steps of: linearly matching the backlight turn-on time ratio with the reference value to obtain a first corresponding curve; setting a first reference value and obtaining a first backlight on-time ratio according to the first reference value and the first corresponding curve; the backlight corresponding to the reference value that is smaller than the first reference value on the first corresponding curve Changing the turn-on time ratio to the first backlight turn-on time ratio to obtain a second corresponding curve; and the second according to a gamma value The modulation curve is obtained by performing gamma correction on the corresponding curve, and the comparison table of the backlight opening time ratio and the reference value is obtained according to the modulation curve. The method of claim 9, wherein the modulation curve is The value of the horse is 2.2. The method of claim 9, wherein the reference value is a numerical operation value relating to one of the picture data. The method of claim 11, wherein the numerical value is a maximum grayscale value of one of the picture data. The method of claim 9, further comprising the steps of: obtaining a ratio of the backlight on time corresponding to the reference value according to the comparison table; and generating the pulse according to the ratio of the backlight on time Width modulation signal. The method of claim 9, further comprising the steps of: inputting the pulse width modulation signal to a light emitting diode driver, so that the light emitting diode driver controls the backlight mode according to the pulse width modulation signal The brightness of the group.