CN111210779B - Liquid crystal module and driving method - Google Patents
Liquid crystal module and driving method Download PDFInfo
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- CN111210779B CN111210779B CN202010019420.XA CN202010019420A CN111210779B CN 111210779 B CN111210779 B CN 111210779B CN 202010019420 A CN202010019420 A CN 202010019420A CN 111210779 B CN111210779 B CN 111210779B
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/3406—Control of illumination source
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/34—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source
- G09G3/36—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters by control of light from an independent source using liquid crystals
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B20/00—Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps
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Abstract
The invention provides a liquid crystal module and a driving method, wherein the liquid crystal module comprises a time sequence control circuit and an LED drive circuit, the time sequence control circuit outputs PWM signals and feedback voltage regulating instructions, the LED drive circuit is connected with the time sequence control circuit and comprises a voltage output end and a voltage feedback end, the LED drive circuit outputs drive voltage to one end of an LED lamp group through the voltage output end and outputs feedback voltage to the other end of the LED lamp group through the voltage feedback end, the LED drive circuit outputs the feedback voltage according to the duty ratio of the PWM signals and the feedback voltage regulating instructions, and the larger the duty ratio of the PWM signals is, the smaller the feedback voltage is. According to the liquid crystal module and the driving method, the LED driving circuit outputs different feedback voltages at the voltage feedback end according to the duty ratios of different PWM signals output by the time sequence control circuit and corresponding feedback voltage adjusting instructions, so that DC dimming can be met, noise can be reduced, the liquid crystal module and the driving method can also be suitable for input of different LED driving voltages, and the maximum power consumption saving of LED driving is realized.
Description
Technical Field
The invention relates to the field of liquid crystal display, in particular to a liquid crystal module and a driving method.
Background
Since the lcd device has many advantages of lightness, thinness, energy saving, no radiation, etc., it is widely used in electronic devices such as televisions, personal computers, tablet computers, Personal Digital Assistants (PDAs), mobile phones, digital cameras, etc. With the development of the times, the demands of users on liquid crystal modules are continuously increased, and it is obvious that noise is reduced as much as possible. The existing solution is to replace PWM dimmed LED driving with DC dimming, since DC dimming can reduce the fluctuation of the output voltage to a large extent, thereby reducing the noise emitted on the ceramic capacitor.
However, in PWM dimming, the current applied to the LED is the set maximum current no matter what the PWM duty ratio is, so that the feedback voltage VFB does not change according to the I-V curve of the LED, and the voltage drop across a string of LEDs does not change under different duty ratios, but when the PWM duty ratio is reduced in DC dimming, the current applied to the LED is also reduced, and the feedback voltage VFB is also reduced according to the I-V curve, so that the voltage drop across a string of LEDs is reduced, for example, the current across a string of LEDs is 7mA when the display is in a narrow viewing angle, and the current is only 0.07mA when the PWM duty ratio is 1%, and the feedback voltage VFB is reduced even lower. FIG. 1 is a schematic circuit diagram of a liquid crystal module according to the prior art. As shown in fig. 1, the LED driving circuit 1 is connected to the LED lamp set 2, and for a display screen capable of displaying with a narrow viewing angle, if the LED lamp set 2 is 8 parallel LED lamp strings and each parallel LED lamp string includes 8 LED lamps, in order to satisfy the voltage input of 5-21V of the LED lamp set 2 and the voltage boosting ratio of LED driving, the driving voltage Vout must be greater than 23V, but when the PWM duty ratio is 1%, the feedback voltage VFB is lowered because the LED current is lowered to 0.07mA, so that the driving voltage Vout does not meet the voltage output requirement of greater than 23V.
The prior art can set the feedback voltage VFB at 3.0V, but then, no matter in the wide view angle mode or the narrow view angle mode, no matter what the duty ratio is, extra power consumption is consumed in the LED driving. For example, when the PWM duty ratio is 100% in the wide view angle mode, the feedback voltage VFB may be set to 0.3V to meet the requirement of the LED driving voltage boosting ratio, but considering the application of the PWM duty ratio of 1% in the narrow view angle mode, the feedback voltage VFB must be set to 3V, so that each LED channel will have (3V-0.3V) 20 mA-54 mW wasted in the form of heat when the LED is driven, thereby increasing the power consumption of the whole liquid crystal module.
Disclosure of Invention
In view of the above, the present invention provides a liquid crystal module, which is capable of outputting different feedback voltages at a voltage feedback end, reducing noise during DC dimming, and also suitable for inputting different LED driving voltages, thereby achieving maximum power saving of LED driving.
Specifically, the embodiment of the invention provides a liquid crystal module, which comprises a time sequence control circuit and an LED driving circuit, wherein the time sequence control circuit outputs a PWM signal and a feedback voltage adjustment instruction, the LED driving circuit is connected to the time sequence control circuit, the LED driving circuit comprises a voltage output end and a voltage feedback end, the LED driving circuit outputs a driving voltage to one end of an LED lamp set through the voltage output end and outputs a feedback voltage to the other end of the LED lamp set through the voltage feedback end, the LED driving circuit outputs the feedback voltage according to a duty ratio of the PWM signal and the feedback voltage adjustment instruction, and the larger the duty ratio of the PWM signal is, the smaller the feedback voltage is.
Further, in the feedback voltage adjustment instruction, the duty ratios of the PWM signals correspond to different feedback voltages in different value ranges.
Further, in the feedback voltage adjustment instruction, the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates.
Further, the timing control circuit comprises an LUT memory, the LUT memory stores a corresponding table of duty ratios and feedback voltages, and the timing control circuit outputs the feedback voltage adjustment instruction according to the corresponding table of duty ratios and feedback voltages in the LUT memory.
Further, in the table of correspondence between the duty ratio and the feedback voltage, the duty ratio of the PWM signal corresponds to different feedback voltages in different value ranges.
Further, in the table of correspondence between the duty ratio and the feedback voltage, the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates.
Further, the timing control circuit receives a mode selection signal, and the timing control circuit outputs different feedback voltage adjustment instructions according to different mode selection signals.
Further, the timing control circuit includes at least two LUT storages, where the at least two LUT storages store different corresponding tables of duty ratios and feedback voltages corresponding to the different mode selection signals, respectively, and the timing control circuit outputs the feedback voltage adjustment instruction according to the corresponding table of duty ratios and feedback voltages in the LUT storages corresponding to the mode selection signals.
Further, in the table of correspondence between the duty ratio and the feedback voltage, the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates.
The embodiment of the invention also provides a driving method of the liquid crystal module, which comprises the following steps: the time sequence control circuit detects a mode selection signal; selecting different LUT memories according to different mode selection signals; receiving a PWM signal and determining a duty ratio of the PWM signal; selecting an adjustable stage number according to the duty ratio of the PWM signal, wherein the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates; searching the feedback voltage corresponding to the duty ratio of the PWM signal in the selected LUT memory, and outputting a corresponding feedback voltage regulation instruction by the time sequence control circuit; and according to different duty ratios of the PWM signals, the LED driving circuit receives the feedback voltage regulation instruction and dynamically switches the feedback voltage.
According to the liquid crystal module and the driving method provided by the embodiment, the LED driving circuit outputs different feedback voltages at the voltage feedback end according to the duty ratios of different PWM signals output by the time sequence control circuit and corresponding feedback voltage adjusting instructions, so that DC dimming noise reduction can be met, the liquid crystal module and the driving method can also be suitable for input of different LED driving voltages, and the maximum power consumption saving of LED driving is realized.
In order to make the aforementioned and other objects, features and advantages of the invention comprehensible, preferred embodiments accompanied with figures are described in detail below.
Drawings
FIG. 1 is a schematic circuit diagram of a liquid crystal module according to the prior art.
Fig. 2 is a schematic circuit diagram of a liquid crystal module according to an embodiment of the invention.
Fig. 3 is a schematic circuit diagram of a liquid crystal module according to another embodiment of the invention.
Fig. 4 is a flowchart illustrating the operation of the liquid crystal module shown in fig. 3.
Detailed Description
To further illustrate the technical means and effects of the present invention for achieving the intended purpose, the following detailed description of the embodiments, methods, steps, structures, features and effects of the liquid crystal module according to the present invention will be made with reference to the accompanying drawings and preferred embodiments.
The foregoing and other aspects, features and advantages of the invention will be apparent from the following more particular description of preferred embodiments, as illustrated in the accompanying drawings. While the invention has been described in connection with specific embodiments thereof, it is to be understood that the invention is not limited to the disclosed embodiments, but is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the invention.
Referring to fig. 2, fig. 2 is a schematic circuit structure diagram of a liquid crystal module according to an embodiment of the invention. As shown in fig. 2, the liquid crystal module includes a timing control circuit 10 and an LED driving circuit 20, the timing control circuit 10 outputs a PWM (Pulse Width Modulation) signal and a feedback voltage adjustment command, the LED driving circuit 20 is connected to the timing control circuit 10, the LED driving circuit 20 includes a voltage output end 21 and a voltage feedback end 22, the LED driving circuit 20 outputs a driving voltage Vout to one end of the LED lamp set 30 through the voltage output end 21 and outputs a feedback voltage VFB to the other end of the LED lamp set 30 through the voltage feedback end 22, the LED driving circuit 20 outputs the feedback voltage VFB according to the duty ratio of the PWM signal and the feedback voltage adjustment command, and the larger the duty ratio of the PWM signal is, the smaller the feedback voltage VFB is.
Specifically, in the present embodiment, the timing control circuit 10 outputs the PWM signal and the feedback voltage adjustment command to the LED driving circuit 20, the LED driving circuit 20 outputs the feedback voltage VFB at the voltage feedback terminal 22 according to the duty ratio of the PWM signal and the feedback voltage adjustment command, and the larger the duty ratio of the PWM signal, the smaller the feedback voltage VFB. That is, the LED driving circuit 20 may obtain the magnitude of the feedback voltage VFB from the feedback voltage adjustment command for different duty ratios of the PWM signal, and the larger the duty ratio of the PWM signal is, the smaller the feedback voltage VFB is. Meanwhile, because two ends of the LED lamp set 30 are respectively connected to the voltage output end 21 and the voltage feedback end 22 of the LED driving circuit 20, the magnitude of the driving voltage Vout received by the LED lamp set 30 from the voltage output end 21 of the LED driving circuit 20 is the feedback voltage VFB plus the voltage drop of each LED of the corresponding LED string of the LED lamp set 30. In the liquid crystal module of this embodiment, the smaller the duty ratio of the PWM signal is, the larger the feedback voltage VFB set by the LED driving circuit 20 from the feedback voltage adjustment command is; as the duty ratio of the PWM signal increases, the feedback voltage VFB set by the LED driving circuit 20 from the feedback voltage adjustment command decreases. Therefore, by setting the LED driving circuit 20 to output different feedback voltages VFB at the voltage feedback terminal 22, the boosting ratio requirement of the LED driving circuit 20 can be met, the DC dimming noise reduction can also be met, and the LED driving circuit is also applicable to the input of different LED driving voltages Vout, and can reduce the power consumption of each LED channel in the LED driving under the condition of improving the display application range, thereby achieving the maximum power consumption saving.
For example, in the prior art, the feedback voltage VFB is fixedly set to be, for example, 2.4V no matter what the duty ratio of the PWM signal is, and in this embodiment, the feedback voltage VFB may be set to be 2.4V when the duty ratio of the PWM signal is 1%, and the feedback voltage VFB may be set to be 0.3V when the duty ratio of the PWM signal is 100%, and if the LED current is 20mA, the power consumption of each corresponding LED channel may be saved as follows: (2.4V-0.3V) × 20mA ═ 42 mW.
In one embodiment, the feedback voltage adjustment command may be transmitted over the I2C bus. The timing control circuit 10 and the LED driving circuit 20 can perform data transmission such as feedback voltage adjustment instruction through the I2C bus. In an embodiment, the LED driving circuit 20 may send an inquiry command for inquiring the duty ratio of the PWM signal corresponding to the feedback voltage VFB to the timing control circuit 10 through the I2C bus according to the received PWM signal, and the timing control circuit 10 correspondingly sends a feedback voltage adjusting command to the LED driving circuit 20 through the I2C bus.
In one embodiment, in the feedback voltage adjustment command, the duty ratio of the PWM signal corresponds to different feedback voltages VFB in different value ranges. For example, if the duty ratio of the PWM signal is in the range of 100% to 98%, the feedback voltage VFB may be set to 0.3V, and for example, if the duty ratio of the PWM signal is in the range of 4% to 1%, the feedback voltage VFB may be set to 2.4V.
In one embodiment, in the feedback voltage adjustment command, the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates. For example, when the duty ratio of the PWM signal is 0< duty < 10%, a corresponding adjustable stage number (1-10) may be set, for example, the voltage change rate when the adjustable stage number is 1 may be 0.01%, and the voltage change rate when the adjustable stage number is 2 may be 0.02%.
In one embodiment, the timing control circuit 10 includes a Look-Up Table (LUT) memory, the LUT memory stores a corresponding Table of duty ratios and feedback voltages, and the timing control circuit 10 outputs the feedback voltage adjustment command according to the corresponding Table of duty ratios and feedback voltages in the LUT memory. In the correspondence table of duty ratios and feedback voltages stored in the LUT memory, duty ratios of different PWM signals correspond to different feedback voltages VFB. The timing control circuit 10 may find the magnitude of the feedback voltage VFB corresponding to the duty ratio of the PWM signal through the LUT memory, and thereby output a corresponding feedback voltage adjustment command to provide the magnitude of the feedback voltage VFB to the LED driving circuit 20.
In an embodiment, in the table of correspondence between the duty ratio and the feedback voltage, the duty ratio of the PWM signal corresponds to different feedback voltages VFB in different value ranges. In the corresponding table of duty ratio and feedback voltage stored in the LUT memory, the duty ratio corresponds to different feedback voltages VFB in different value ranges according to the duty ratio of the PWM signal. The timing control circuit 10 may find the magnitude of the feedback voltage VFB corresponding to the value range of the duty ratio of the PWM signal through the LUT memory, so as to output a corresponding feedback voltage adjustment command to provide the magnitude of the feedback voltage VFB to the LED driving circuit 20.
In an embodiment, in the table of correspondence between duty ratios and feedback voltages, the duty ratios of the PWM signals correspond to corresponding adjustable stages in corresponding value ranges, and different adjustable stages correspond to different voltage change rates.
In the liquid crystal module provided in this embodiment, the LED driving circuit 20 outputs different feedback voltages VFB at the voltage feedback end 22 according to the duty ratios of different PWM signals output by the timing control circuit 10 and corresponding feedback voltage adjustment commands, so as to meet the requirements of DC dimming and noise reduction, and is also suitable for the input of different LED driving voltages Vout, thereby achieving maximum power saving of LED driving.
Fig. 3 is a schematic circuit diagram of a liquid crystal module according to another embodiment of the invention. As shown in fig. 3, an embodiment of the invention further provides a liquid crystal module, the liquid crystal module of this embodiment has a circuit structure substantially the same as that of the liquid crystal module of the previous embodiment, except that the timing control circuit 10 receives a mode selection signal, and the timing control circuit 10 outputs different feedback voltage adjustment commands according to different mode selection signals.
In an embodiment, the timing control circuit 10 includes at least two LUT memories, the at least two LUT memories respectively store different corresponding tables of duty ratios and feedback voltages corresponding to different mode selection signals, and the timing control circuit 10 outputs the feedback voltage adjustment command according to the corresponding table of duty ratios and feedback voltages in the LUT memory corresponding to the mode selection signal. The following description will take as an example that different mode selection signals correspond to the wide view mode and the narrow view mode, respectively. In the wide view angle mode, the timing control circuit 10 selects a corresponding LUT1 memory of the two LUT memories according to the corresponding mode selection signal, searches the magnitude of the feedback voltage VFB corresponding to the duty ratio of the PWM signal in the wide view angle mode from the LUT1 memory, and outputs a corresponding feedback voltage adjustment command to the LED driving circuit 20; in the narrow viewing angle mode, the timing control circuit 10 selects the LUT2 memory of the two LUT memories according to the corresponding mode selection signal, searches the magnitude of the feedback voltage VFB corresponding to the duty ratio of the PWM signal in the narrow viewing angle mode from the LUT2 memory, and outputs a corresponding feedback voltage adjustment command to the LED driving circuit 20.
In an embodiment, in the table of correspondence between the duty ratio and the feedback voltage, the duty ratio of the PWM signal may correspond to different feedback voltages VFB in different value ranges. According to different mode selection signals, corresponding LUT memories in the LUT memories are selected to obtain a corresponding table of duty ratios and feedback voltages, the duty ratios of the PWM signals may correspond to different feedback voltages VFB in different value ranges, and different feedback voltage adjustment commands are output to the LED driving circuit 20. For example, according to the low level of the mode selection signal, an LUT memory, that is, an LUT1 memory, corresponding to the wide view angle mode is selected, and the duty ratio of the PWM signal may correspond to different feedback voltages VFB in different value ranges, referring to table 1 below; according to the high level of the mode selection signal, the LUT2 memory corresponding to the wide view mode is selected, and the duty ratio of the PWM signal may correspond to different feedback voltages VFB in different value ranges, as shown in table 2 below.
Table 1 wide view mode: LUT1 memory
Table 2 narrow viewing angle mode: LUT2 memory
In an embodiment, in the table of correspondence between duty ratios and feedback voltages, the duty ratios of the PWM signals correspond to corresponding adjustable stages in corresponding value ranges, and different adjustable stages correspond to different voltage change rates. For example, the duty cycle range of the PWM signal versus the number of adjustable stages may be as follows in table 3.
Specifically, in the present embodiment, the timing control circuit 10 receives the mode selection signal, the timing control circuit 10 outputs different feedback voltage adjustment commands according to different mode selection signals, and fig. 4 is a flowchart illustrating a working process of the liquid crystal module shown in fig. 3. As shown in fig. 4, the present embodiment further provides a driving method of a liquid crystal module, and the working process includes:
s10, the timing control circuit 10 detects the mode selection signal;
the timing control circuit 10 detects mode selection signals, and the different mode selection signals respectively correspond to different viewing angle modes, for example, a low-level mode selection signal corresponds to a wide viewing angle mode, and a high-level mode selection signal corresponds to a narrow viewing angle mode.
S20, selecting different LUT memories according to different mode selection signals;
for example, if the detected mode select signal is low level L, the selected LUT memory is the LUT1 memory; if the detected mode select signal is high H, the selected LUT memory is the LUT2 memory.
S30, receiving the PWM signal and judging the duty ratio of the PWM signal;
s40, selecting an adjustable stage number according to the duty ratio of the PWM signal, wherein the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates;
for example, when the duty ratio of the PWM signal is 0< duty < 10%, a corresponding adjustable stage number (1-10) may be set, for example, the voltage change rate when the adjustable stage number is 1 may be 0.01%, and the voltage change rate when the adjustable stage number is 2 may be 0.02%.
S50, the size of the feedback voltage VFB corresponding to the duty ratio of the PWM signal is searched in the selected LUT memory, and the timing control circuit 10 outputs a corresponding feedback voltage adjustment command.
S60, according to the duty ratios of the different PWM signals, the LED driving circuit 20 receives the feedback voltage regulation command to dynamically switch the feedback voltage VFB;
the timing control circuit 10 searches the feedback voltage VFB in the corresponding LUT memory according to the duty ratio of the PWM signal and the mode selection signal in real time, and outputs a feedback voltage adjustment command, and the LED driving circuit 20 dynamically switches the feedback voltage VFB according to the feedback voltage adjustment command.
Specifically, in the present embodiment, the timing control circuit 10 outputs the PWM signal and outputs different feedback voltage adjusting commands to the LED driving circuit 20 according to different mode selection signals, so that the LED driving circuit 20 outputs the feedback voltage VFB at the voltage feedback terminal 22 according to the duty ratio of the PWM signal and the feedback voltage adjusting command, and the larger the duty ratio of the PWM signal is, the smaller the feedback voltage VFB is. Accordingly, the LED driving circuit 20 may obtain different magnitudes of the feedback voltage VFB from the feedback voltage regulation command at different mode selection signals, and the larger the duty ratio of the PWM signal is, the smaller the feedback voltage VFB is. Therefore, by setting the LED driving circuit 20 to output different feedback voltages VFB at the voltage feedback terminal 22 when the LED driving circuit 20 is in different display modes, the boost ratio requirement of the LED driving circuit 20 can be met, the DC dimming noise can be reduced, and the LED driving circuit can be applied to the input of different LED driving voltages Vout, and can reduce the power consumption of each LED channel in LED driving under the condition of improving the display application range, thereby saving the power consumption to the maximum extent.
For example, in the wide view angle mode, in order to meet the requirement when the duty ratio of the PWM signal is 1%, the feedback voltage VFB is fixedly set at 2.4V, whereas in the present embodiment, the feedback voltage VFB may be set at 2.4V when the duty ratio of the PWM signal is 1%, and the feedback voltage VFB may be set at 0.3V when the duty ratio of the PWM signal is 100%, and if the LED current is 20mA, the power consumption of each corresponding LED channel may be saved as follows: (2.4V-0.3V) × 20mA ═ 42 mW; in the narrow viewing angle mode, in order to meet the requirement when the duty ratio of the PWM signal is 1%, the feedback voltage VFB is fixedly set at 3.0V in the prior art, and in this embodiment, the feedback voltage VFB may be set to 3.0V when the duty ratio of the PWM signal is 1%, and the feedback voltage VFB may be set to 1.6V when the duty ratio of the PWM signal is 100%, if the LED current is 7mA, the power consumption of each corresponding LED channel may be saved as follows: (3.0V-1.6V) × 7mA ═ 10 mW.
According to the liquid crystal module and the driving method provided by the embodiment, in different display modes, the LED driving circuit 20 outputs different feedback voltages VFB at the voltage feedback end 22 according to the duty ratios of different PWM signals output by the timing control circuit 10 and corresponding feedback voltage adjustment instructions, so that DC dimming noise reduction can be met, and the driving method can be applied to input of different LED driving voltages Vout, so as to achieve maximum power consumption saving of LED driving.
Although the present invention has been described with reference to the preferred embodiments, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims.
Claims (10)
1. A liquid crystal module, comprising:
a timing control circuit (10), the timing control circuit (10) outputting a PWM signal and a feedback voltage adjustment instruction;
LED drive circuit (20), LED drive circuit (20) with sequential control circuit (10) link to each other, LED drive circuit (20) include voltage output end (21) and voltage feedback end (22), LED drive circuit (20) are through voltage output end (21) output drive voltage to the one end of LED banks (30), and pass through voltage feedback end (22) output feedback voltage extremely the other end of LED banks (30), LED drive circuit (20) are according to the duty cycle of PWM signal with feedback voltage adjusts the instruction output feedback voltage, just the duty cycle of PWM signal is big more, feedback voltage is little more.
2. The liquid crystal module of claim 1, wherein in the feedback voltage adjustment command, the duty ratios of the PWM signals correspond to different feedback voltages in different value ranges.
3. The liquid crystal module of claim 1, wherein in the feedback voltage adjustment command, the duty cycle of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates.
4. The liquid crystal module according to claim 1, wherein the timing control circuit (10) includes an LUT memory that stores a correspondence table of duty ratios and feedback voltages, the timing control circuit (10) outputting the feedback voltage adjustment instruction according to the correspondence table of duty ratios and feedback voltages in the LUT memory.
5. The liquid crystal module as claimed in claim 4, wherein in the table of correspondence between the duty ratio and the feedback voltage, the duty ratio of the PWM signal corresponds to different feedback voltages in different value ranges.
6. The liquid crystal module of claim 4, wherein in the table of correspondence between duty ratios and feedback voltages, the duty ratios of the PWM signals correspond to corresponding adjustable levels in corresponding value ranges, and different adjustable levels correspond to different voltage change rates.
7. The liquid crystal module as set forth in claim 1, wherein the timing control circuit (10) receives a mode selection signal, and the timing control circuit (10) outputs different feedback voltage adjustment commands according to different mode selection signals.
8. The liquid crystal module as set forth in claim 7, wherein the timing control circuit (10) comprises at least two LUT memories respectively storing different corresponding tables of duty ratio and feedback voltage corresponding to different ones of the mode selection signals, and the timing control circuit (10) outputs the feedback voltage adjustment command according to the corresponding table of duty ratio and feedback voltage in the LUT memory corresponding to the mode selection signal.
9. The liquid crystal module of claim 8, wherein in the table of correspondence between duty ratios and feedback voltages, the duty ratios of the PWM signals correspond to corresponding adjustable levels in corresponding value ranges, and different adjustable levels correspond to different voltage change rates.
10. A driving method of a liquid crystal module is characterized by comprising the following steps:
a timing control circuit (10) detects a mode selection signal;
selecting different LUT memories according to different mode selection signals;
receiving a PWM signal and determining a duty ratio of the PWM signal;
selecting an adjustable stage number according to the duty ratio of the PWM signal, wherein the duty ratio of the PWM signal corresponds to a corresponding adjustable stage number in a corresponding value range, and different adjustable stage numbers correspond to different voltage change rates;
searching the feedback voltage corresponding to the duty ratio of the PWM signal in the selected LUT memory, and outputting a corresponding feedback voltage regulation instruction by the time sequence control circuit (10);
and according to different duty ratios of the PWM signals, the LED driving circuit (20) receives the feedback voltage regulation instruction and dynamically switches the feedback voltage.
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