CN112233625A - Backlight constant-current control circuit and backlight structure - Google Patents
Backlight constant-current control circuit and backlight structure Download PDFInfo
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- CN112233625A CN112233625A CN202011110366.6A CN202011110366A CN112233625A CN 112233625 A CN112233625 A CN 112233625A CN 202011110366 A CN202011110366 A CN 202011110366A CN 112233625 A CN112233625 A CN 112233625A
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- 235000019557 luminance Nutrition 0.000 description 7
- 230000000694 effects Effects 0.000 description 6
- 230000009286 beneficial effect Effects 0.000 description 5
- 239000003990 capacitor Substances 0.000 description 5
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- 230000002349 favourable effect Effects 0.000 description 2
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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
- G09G3/3406—Control of illumination source
- G09G3/3413—Details of control of colour illumination sources
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/32—Pulse-control circuits
- H05B45/325—Pulse-width modulation [PWM]
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- H—ELECTRICITY
- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B45/00—Circuit arrangements for operating light-emitting diodes [LED]
- H05B45/30—Driver circuits
- H05B45/345—Current stabilisation; Maintaining constant current
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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
- Y02B20/40—Control techniques providing energy savings, e.g. smart controller or presence detection
Abstract
The application discloses a backlight constant current control circuit and a backlight structure, wherein the backlight constant current control circuit comprises a light emitting module and a constant current control module; the constant current control module comprises a first switch unit; the constant current control module is used for adjusting the conduction time and the conduction degree of the first switch unit when detecting that the working current of the light emitting module deviates from the preset current so as to adjust the working current of the light emitting module to the preset current and keep the light emitting brightness of the light emitting module to be the preset light emitting brightness. The current of the light emitting module is kept to be the preset current by carrying out constant current control on the light emitting module, so that the brightness unevenness caused by current fluctuation is avoided, and the backlight brightness stability is improved.
Description
Technical Field
The application relates to the technical field of display, in particular to a backlight constant-current control circuit and a backlight structure.
Background
With the rapid development of the information-oriented society and the increasing maturity of the driving technology of the panel industry, the opportunity and the challenge are also followed, and due to the limitations of the LCD backlight, such as large power consumption and low contrast, the backlight is forced to develop towards Local dimming (Local controllability).
With the development of the technology, the Mini LED with an ultra-small process structure can realize small-batch mass production, and the Mini LED can realize more partitions due to a small structure.
The existing Mini LED backlight adopts Local Dimming backlight realized by an Active addressing driving (AM, also called Active addressing, Active driving and the like), each partition is formed by connecting a plurality of LED lamps in series, each partition is driven to work by a constant voltage control mode (namely VDD voltage is fixed), when one LED lamp in a circuit is in fault and short circuit, the total resistance of the LED lamp strings in the partition is reduced, the current of the LED lamp string in the partition is increased due to the unchanged voltage at two ends of the LED lamp string, the LED lamp is extremely sensitive to the current, the display brightness of the partition is larger than other partitions or is larger than the required brightness, the brightness of the whole backlight is uneven, and the display effect is greatly influenced.
Disclosure of Invention
The application provides a constant current control circuit and structure in a poor light, can avoid influencing the current of light emitting module after certain device short circuit in the light emitting module through carrying out constant current control to light emitting module, be favorable to making the current of light emitting module keep for predetermineeing the current for the luminance of light emitting module keeps for predetermineeing luminance, thereby guarantees that luminance is stable and the distribution is even in a poor light, is favorable to improving display effect.
The application provides a backlight constant current control circuit, which comprises a light emitting module and a constant current control module;
the constant current control module comprises a first switch unit; the constant current control module is used for adjusting the conduction time and the conduction degree of the first switch unit when detecting that the working current of the light emitting module deviates from the preset current so as to adjust the working current of the light emitting module to the preset current and keep the light emitting brightness of the light emitting module to be the preset light emitting brightness.
Optionally, the constant current control module further includes a feedback unit and a sampling unit;
the sampling unit is electrically connected with the first switch unit;
the feedback unit is respectively electrically connected with the sampling unit and the first switch unit and used for detecting the voltages at two ends of the sampling unit and determining that the working current of the light-emitting module deviates from the preset current when the voltages at two ends of the sampling unit deviate from the preset voltage, and the conduction time and the conduction degree of the first switch unit are adjusted to adjust the working current of the light-emitting module to the preset current.
Optionally, the feedback unit includes a level shifter, a first PWM controller, and a comparator;
the comparator is respectively electrically connected with the sampling unit and the first PWM controller and is used for detecting the voltages at two ends of the sampling unit and comparing the voltages at two ends of the sampling unit with the preset voltage; when the voltage at the two ends of the sampling unit deviates from the preset voltage, determining that the working current of the light-emitting module deviates from the preset current, and outputting a level signal to the first PWM controller according to the deviation degree;
the first PWM controller is also electrically connected with the level converter and is used for outputting a duty ratio signal to the level converter according to the level signal;
the level shifter is also electrically connected with the first switch unit and used for adjusting the level of the duty ratio signal and adjusting the conduction time and the conduction degree of the first switch unit through the adjusted duty ratio signal.
Optionally, the first switching unit includes a first transistor, and the sampling unit includes a sampling resistor;
the drain electrode of the first transistor is electrically connected with the output end of the light-emitting module, the source electrode of the first transistor is grounded through the sampling resistor, and the grid electrode of the first transistor is electrically connected with the output end of the level shifter;
the input end of the comparator is electrically connected with the source electrode of the first transistor, and the output end of the comparator is electrically connected with the input end of the first PWM controller;
and the output end of the first PWM controller is electrically connected with the input end of the level conversion.
Optionally, the light emitting module comprises a plurality of LEDs arranged in series.
Optionally, the backlight constant current control circuit further includes a boosting module electrically connected to the input terminal of the light emitting module;
the boosting module comprises a charging and discharging unit, a second switching unit and a third switching unit; the charging and discharging unit is electrically connected with the second switch unit and the third switch unit respectively;
the boosting module is used for adjusting the conduction time of the second switch unit and the third switch unit according to the preset light-emitting brightness; and when the first switch unit is switched on, the charging and discharging unit is charged, and when the second switch unit is switched on, the charging and discharging unit is discharged, so that a preset power supply voltage is output to the input end of the light-emitting module.
Optionally, the boost module further includes a driver and a second PWM controller; the charging and discharging unit comprises an inductor, the second switching unit comprises a second transistor, and the third switching unit comprises a third transistor;
the second PWM controller is electrically connected with the input end of the driver; the input end of the driver is electrically connected with the second PWM controller, and the output end of the driver is respectively electrically connected with the grid electrode of the second transistor and the grid electrode of the third transistor;
one end of the inductor is connected with an input voltage, the other end of the inductor is respectively electrically connected with the drain electrode of the second transistor and the source electrode of the third transistor, the source electrode of the second transistor is grounded, and the drain electrode of the third transistor is electrically connected with the input end of the light emitting module.
The application also provides a backlight structure, which comprises a plurality of backlight constant current control circuits; the backlight structure comprises at least one backlight partition, and each backlight partition is provided with at least one light-emitting module of the backlight constant-current control circuit.
Optionally, a plurality of constant current control modules in the backlight constant current control circuits are integrated in the same control chip.
Optionally, the backlight constant current control circuit further includes a boost module, and the boost module is also integrated in the control chip.
According to the backlight constant current control circuit and the backlight structure, the constant current control module comprises a first switch unit electrically connected with the light emitting module; when the constant current control module detects that the working current of the light emitting module deviates from the preset current, the light emitting time of the light emitting module and the partial pressure of the light emitting module can be adjusted by adjusting the conduction time and the conduction degree of the first switch unit, so that the working current (average current) of the light emitting module can be adjusted, the working current of the light emitting module is equal to the preset current, the light emitting brightness of the light emitting module can be kept to be the preset light emitting brightness, the problem that the backlight structure brightness of the light emitting module is uneven due to current fluctuation is avoided, and the stability of the backlight brightness is improved; when the backlight constant current control circuit and the backlight structure are applied to a display device, the display effect is improved.
Drawings
The technical solution and other advantages of the present application will become apparent from the detailed description of the embodiments of the present application with reference to the accompanying drawings.
Fig. 1 is a schematic block diagram of a backlight constant current control circuit provided in an embodiment of the present application.
Fig. 2 is a circuit schematic diagram of a backlight constant current control circuit provided in an embodiment of the present application.
Fig. 3a is a schematic view of a backlight structure according to an embodiment of the present disclosure.
Fig. 3b is a schematic view of another backlight structure provided in the embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. It is to be understood that the embodiments described are only a few embodiments of the present application and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed in a particular orientation, and be operated in a particular manner, and are not to be construed as limiting the present application. Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", may explicitly or implicitly include one or more of the described features. In the description of the present application, "a plurality" means two or more unless specifically limited otherwise.
In the description of the present application, it is to be noted that, unless otherwise explicitly specified or limited, the terms "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; may be mechanically connected, may be electrically connected or may be in communication with each other; either directly or indirectly through intervening media, either internally or in any other relationship. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.
In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may comprise direct contact of the first and second features, or may comprise contact of the first and second features not directly but through another feature in between. Also, the first feature being "on," "above" and "over" the second feature includes the first feature being directly on and obliquely above the second feature, or merely indicating that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature includes the first feature being directly under and obliquely below the second feature, or simply meaning that the first feature is at a lesser elevation than the second feature.
The following disclosure provides many different embodiments or examples for implementing different features of the application. In order to simplify the disclosure of the present application, specific example components and arrangements are described below. Of course, they are merely examples and are not intended to limit the present application. Moreover, the present application may repeat reference numerals and/or letters in the various examples, such repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, examples of various specific processes and materials are provided herein, but one of ordinary skill in the art may recognize applications of other processes and/or use of other materials.
As shown in fig. 1 and fig. 2, an embodiment of the present application provides a backlight constant current control circuit 1, where the backlight constant current control circuit 1 includes a light emitting module 2 and a constant current control module 3; the constant current control module 3 comprises a first switch unit 4 which is connected with the light-emitting module 2 in series; the constant current control module 3 is configured to adjust the conduction time and the conduction degree of the first switch unit 4 when detecting that the working current of the light emitting module 2 deviates from the preset current, so as to adjust the working current of the light emitting module 2 to the preset current, and maintain the light emitting brightness of the light emitting module 2 to be the preset light emitting brightness.
Specifically, in the embodiment of the present application, the luminance of the light emitting module 2 is controlled by the working current; the working current is the actual current when the light emitting module 2 emits light, and the preset current is the current flowing through the light emitting module 2 when the light emitting module 2 presets the light emitting brightness; therefore, the preset current can be obtained according to the preset light emission luminance.
Specifically, the light emitting module 2 includes a plurality of LEDs arranged in series, specifically, a plurality of Mini-LEDs arranged in series, and in this embodiment, 4 LEDs arranged in series are taken as an example for illustration. Since the average current in unit time is used for determining the brightness of the LED, both the working current and the preset current can be understood as the average current. Since the light emitting module 2 is connected in series with the first switch unit 4, the light emitting time of the light emitting module 2 can be controlled by controlling the on-time of the first switch unit 4, so as to control the average current of the light emitting module 2 and realize the adjustment of the working current of the light emitting module 2. In addition, the first switch unit 4 in the embodiment of the present application is a voltage-controlled device, such as a transistor, which may be specifically an NMOS transistor; the on-resistance Rds between the drain and the source of the first switching unit 4 can be controlled by controlling Vgs (voltage between the gate and the source) of the first switching unit 4, that is, the on-state of the first switching unit 4; since the light emitting module 2 is disposed in series with the first switching unit 4, the voltage division of the light emitting module 2 on the whole circuit can be controlled by controlling the magnitude of Rds, thereby adjusting the operating current of the light emitting module 2. Therefore, the embodiment of the application can adjust the light emitting time and the partial pressure of the light emitting module 2 by adjusting the conduction time and the conduction degree of the first switch unit 4, thereby adjusting the working current of the light emitting module 2 to the preset current, keeping the light emitting brightness of the light emitting module 2 to the preset light emitting brightness, avoiding the problems of current fluctuation and uneven brightness caused by the short circuit of the LED in the light emitting module 2, and being beneficial to improving the stability of backlight brightness, and being beneficial to improving the display effect when the backlight constant current control circuit 1 is applied to a display device.
The constant current control module 3 further comprises a feedback unit 5 and a sampling unit 6. The sampling unit 6 is electrically connected with the light-emitting module 2 through the first switch unit 4; the feedback unit 5 is electrically connected to the sampling unit 6 and the first switch unit 4, and is configured to detect a voltage Vs across the sampling unit 6, determine that the working current of the light emitting module 2 deviates from a preset current when the voltage Vs across the sampling unit 6 deviates from a preset voltage Vref, and adjust the conduction time and the conduction degree of the first switch unit 4 to adjust the working current of the light emitting module 2 to the preset current.
In particular, the sampling unit 6 has a fixed resistance R0The light emitting module 2, the first switching unit 4 and the sampling unit 6 are connected in series, and thus flow through the light emitting module 2, the first switching unit 4 and the sampling unit6, the current is the same; therefore, the operating current of the light emitting module 2 can be obtained from the voltage Vs across the sampling unit 6. In the embodiment of the present application, when the preset voltage Vref is the voltage Vs at two ends of the sampling unit 6 when the current of the sampling unit 6 is the preset current, that is, the preset voltage Vref is equal to the preset current × R0Therefore, the magnitude of the working current of the light emitting module 2 can be compared with the magnitude of the preset current by comparing the voltage Vs across the sampling unit 6 with the magnitude of the preset voltage Vref.
Specifically, the feedback unit 5 includes a level shifter Ls, a first PWM controller 7, and a comparator Com.
The comparator Com is electrically connected with the sampling unit 6 and the first PWM controller 7, and is configured to detect a voltage Vs across the sampling unit 6, and compare the voltage Vs across the sampling unit 6 with a preset voltage Vref; when the voltage Vs across the sampling unit 6 deviates from the preset voltage Vref, it is determined that the operating current of the light emitting module 2 deviates from the preset current, and a level signal is output to the first PWM controller 7 according to the degree of deviation. The first PWM controller 7 is further electrically connected to the level shifter Ls for outputting a first duty cycle signal to the level shifter Ls according to the level signal. The level shifter Ls is further electrically connected to the first switch unit 4, and is configured to adjust a level of the first duty ratio signal, and adjust a conduction time and a conduction degree of the first switch unit 4 according to the adjusted first duty ratio signal.
Specifically, when the working current of the light emitting module 2 deviates (is greater than) the preset current in the positive direction, the comparator Com outputs a first level signal to the first PWM controller 7, and when the working current of the light emitting module 2 deviates (is less than) the preset current in the negative direction, the comparator Com outputs a second level signal to the first PWM controller 7; the first PWM controller 7 outputs different first duty ratio signals according to the first level signal and the second level signal.
Specifically, the level shifter Ls is used to amplify the first duty cycle signal, i.e. to increase the level of the first duty cycle signal.
In one embodiment, the first switch unit 4 is a first transistor Q1, specifically an NMOS transistor; the sampling unit 6 is a sampling resistor Rs. The drain of the first transistor Q1 is electrically connected to the output terminal of the light emitting module 2, the source of the first transistor Q1 is grounded via the sampling resistor Rs, and the gate of the first transistor Q1 is electrically connected to the output terminal of the level shifter Ls. An input terminal of the comparator Com is electrically connected to the source of the first transistor Q1, and an output terminal of the comparator Com is electrically connected to an input terminal of the first PWM controller 7. The output of the first PWM controller 7 is electrically connected to the input of the level shift.
It is understood that the input terminal of the light emitting module 2 is an anode terminal, and the output terminal of the light emitting module 2 is a cathode terminal.
In particular, the comparator Com comprises a non-inverting input (+) and an inverting input (-). When the non-inverting input end of the comparator Com is electrically connected with the source electrode of the first transistor Q1, the non-inverting input end of the comparator Com is connected with a preset voltage Vref, and at the moment, the non-inverting input end of the comparator Com receives the voltage Vs at the two ends of the sampling resistor Rs; comparing the voltage Vs across the sampling unit 6 with the preset voltage Vref, if the voltage Vs across the sampling unit 6 is greater than the preset voltage Vref, the comparator Com outputs a high level signal to the first PWM controller 7, and if the voltage Vs across the sampling unit 6 is less than the preset voltage Vref, the comparator Com outputs a low level signal to the first PWM controller 7. Of course, when the inverting input terminal of the comparator Com is electrically connected to the source of the first transistor Q1, the non-inverting input terminal of the comparator Com is connected to the preset voltage Vref, and at this time, the inverting input terminal of the comparator Com receives the voltage Vs across the sampling resistor Rs; comparing the voltage Vs across the sampling unit 6 with the preset voltage Vref, if the voltage Vs across the sampling unit 6 is greater than the preset voltage Vref, the comparator Com outputs a low level signal to the first PWM controller 7, and if the voltage Vs across the sampling unit 6 is less than the preset voltage Vref, the comparator Com outputs a high level signal to the first PWM controller 7.
In an embodiment, the constant current control module 3 may further include a controller electrically connected to an input terminal of the comparator Com, and configured to output the preset voltage Vref to the comparator Com. The constant current control module 3 may further include an adjusting resistor, one end of the adjusting resistor is electrically connected to the controller, and the other end of the adjusting resistor is grounded. The controller can adjust the preset luminance of the light emitting module 2 according to the resistance of the adjusting resistor, and it can be understood that the preset voltage Vref output by the controller is different when the resistance of the adjusting resistor is different. The setting of the adjusting resistor can enable the constant current control module 3 to be suitable for the light emitting modules 2 with different brightness requirements, and the application range is enlarged.
Specifically, the backlight constant current control circuit 1 further includes a voltage boosting module 8 electrically connected to the input terminal of the light emitting module 2, and configured to provide a preset power voltage VDD to the input terminal of the light emitting module 2. The boost module 8 comprises a charge and discharge unit 9, a second switching unit 10 and a third switching unit 11; the charge and discharge unit 9 is electrically connected to the second switching unit 10 and the third switching unit 11, respectively, and the third switching unit 11 is electrically connected to an input terminal of the light emitting module 2. The boosting module 8 is used for adjusting the conducting time of the second switching unit 10 and the third switching unit 11 according to preset light-emitting brightness; the charging and discharging unit 9 is charged when the first switch unit 4 is turned on, and the charging and discharging unit 9 is discharged when the second switch unit 10 is turned on, so as to output a predetermined power voltage VDD to the input terminal of the light emitting module 2.
It should be noted that the preset power voltage VDD in this embodiment is a fixed voltage.
Specifically, the boost module 8 further includes a driver 12 and a second PWM controller 13; the charging and discharging unit 9 is an inductor Lf, the second switching unit 10 is a second transistor Q2, specifically an NMOS transistor, and the third switching unit 11 is a third transistor Q3, specifically a PMOS transistor. The second PWM controller 13 is electrically connected to an input terminal of the driver 12, and is configured to output a second duty ratio signal to the driver 12 according to a preset light emitting brightness. An input terminal of the driver 12 is electrically connected to the second PWM controller 13, and an output terminal of the driver 12 is electrically connected to a gate of the second transistor Q2 and a gate of the third transistor Q3, respectively, for adjusting turn-on times of the second transistor Q2 and the third transistor Q3, respectively, according to the second duty signal. One end of the inductor Lf is connected to the input voltage Vin, the other end is electrically connected to the drain of the second transistor Q2 and the source of the third transistor Q3, the source of the second transistor Q2 is grounded, and the drain of the third transistor Q3 is electrically connected to the input terminal of the light emitting module 2.
Specifically, the boost module 8 may boost the input voltage Vin to a preset output voltage through a charging process of the inductor Lf, and may output the preset output voltage to the input end of the light emitting module 2 through a discharging process of the inductor Lf.
Specifically, the boost module 8 further includes a first capacitor C1 and a second capacitor C2. One end of the first capacitor C1 is electrically connected to one end of the inductor Lf far away from the second transistor Q2, and the other end is grounded, so as to stabilize the input voltage Vin; one end of the second capacitor C2 is electrically connected to the input end of the light emitting module 2, and the other end is grounded, so as to keep the preset output voltage VDD stable.
Specifically, the other input end of the driver 12 is further connected to an enable signal En, when the enable signal En is at a high level, the driver 12 is in an operating state, and when the enable signal En is at a low level, the driver 12 is in a shutdown state; the enable signal En may be provided to the driver 12 by gate driving.
Specifically, the working principle of the boost module 8 is as follows: when the driver 12 is connected to the enable signal En of high level, the boost module 8 starts to operate, the second PWM controller 13 outputs a second duty ratio signal to the driver 12 according to the preset light emitting brightness of the light emitting module 2, the driver 12 controls the second transistor Q2 and the third transistor Q3 to be sequentially turned on according to the second duty ratio signal, when the second transistor Q2 is turned on and the third transistor Q3 is turned off, the inductor Lf is charged, the input voltage Vin flows through the inductor Lf, and the current on the inductor Lf linearly increases at a certain proportion; when the second transistor Q2 is turned off and the third transistor Q3 is turned on, the inductor Lf discharges, and the current flowing through the inductor Lf flows to the input terminal of the light emitting module 2 and charges the second capacitor C2, so that the voltage VDD received by the input terminal of the light emitting module 2 is higher than the input voltage Vin. Therefore, by controlling the turn-on time of the second transistor Q2 and the third transistor Q3 to be different, the increase ratio of the input voltage Vin can be controlled to be different, and different VDD can be provided according to the preset brightness.
Of course, the embodiment of the present application does not limit to providing the preset power voltage VDD to the input terminal of the light emitting module 2 in other ways.
In the backlight constant current control circuit 1 provided in the embodiment of the present application, the constant current control module 3 includes a first switch unit 4 and a sampling unit 6 that are sequentially connected in series with the light emitting module 2, and a feedback unit 5 that is electrically connected to the first switch unit 4 and the sampling unit 6, respectively. The constant current control module 3 detects the voltage Vs at the two ends of the sampling unit 6 through the feedback unit 5, so as to indirectly detect the working current of the light emitting module 2, and when the working current of the light emitting module 2 is detected to deviate from the preset current, the feedback unit 5 adjusts the conduction time and the conduction degree of the first switch unit 4 to adjust the light emitting time of the light emitting module 2 and the partial pressure of the light emitting module, so as to adjust the working current (average current) of the light emitting module 2, so that the working current of the light emitting module 2 is equal to the preset current, the light emitting brightness of the light emitting module 2 can be kept to be the preset light emitting brightness, the problem that the light emitting module 2 has uneven brightness due to current fluctuation is avoided, and the stability of the backlight brightness; when the backlight constant current control circuit 1 is applied to a display device, the display effect is improved.
As shown in fig. 3a and fig. 3b, an embodiment of the present application further provides a backlight structure 14, where the backlight structure 14 includes a plurality of backlight constant current control circuits provided in the above embodiments. The backlight structure 14 includes at least one backlight partition 15, and each backlight partition 15 is provided with at least one light emitting module of a backlight constant current control circuit.
Specifically, the plurality of constant current control modules in the plurality of backlight constant current control circuits are integrally arranged in the same control chip 16, and the boost module in the backlight constant current control circuit may also be integrally arranged in the control chip 16. At this time, the light emitting modules and the connecting lines between the light emitting modules and the control chip 16 are arranged in the backlight subarea 15, and the control chip 16 can be arranged in the frame area or the back of the backlight structure 14, so as to avoid being arranged in the backlight subarea 15, and the light emitting modules of a plurality of subareas can be controlled by one control chip 16, so that the circuit structure of the backlight subarea 15 can be effectively simplified, and the cost can be reduced.
Specifically, a first end of the control chip 16 is connected to the input voltage Vin, a second end of the control chip 16 is connected to the enable signal En, a third end of the control chip 16 is grounded, a fourth end of the control chip 16 is electrically connected to the output ends of the light emitting modules in the backlight partitions 15, and a fifth end of the control chip 16 is electrically connected to the output ends of the light emitting modules in the backlight partitions 15.
Fig. 3a and 3b illustrate an example of 4 backlight partitions 15, and the 4 backlight partitions 15 are respectively provided with light emitting modules D1, D2, D3 and D4. As shown in fig. 3a, when the brightness requirements of the 4 backlight partitions 15 are consistent, that is, the preset brightness luminances of the light emitting modules D1, D2, D3 and D4 are the same, only one boosting module may be disposed in the control chip 16, and the output terminals of the boosting module are electrically connected to the input terminals of the light emitting modules D1, D2, D3 and D4, respectively, for providing the same preset power voltage VDD; at this time, the number of the boosting modules can be reduced, and the number of the input ends of the enable signal En can be reduced, thereby facilitating the simplification of the circuit and the cost saving. As shown in fig. 3b, when the brightness requirements of the 4 backlight partitions 15 are different, a voltage boosting module is disposed in the control chip 16 corresponding to each backlight partition 15, such that VDD received by the input terminals of the light emitting modules D1, D2, D3 and D4 are different, for example, VDD1, VDD2, VDD3 and VDD4, and each voltage boosting module corresponds to an enable signal En, for example, En1, En2, En3 and En 4.
In this implementation, the constant current control module in the backlight structure 14 can perform constant current control on the light emitting module, so as to avoid the influence of fluctuation of the working current caused by the short circuit of the LED on the brightness of the light emitting module, and therefore, the backlight structure 14 can be applied to a liquid crystal display device to provide a backlight source with stable brightness for a liquid crystal display panel, which is beneficial to the stability and uniform distribution of the backlight brightness, thereby being beneficial to improving the display effect. In addition, the constant current control module and the boost module in the backlight structure 14 are integrated in one control chip 16, so that the backlight structure 14 can adjust the light emitting brightness of the light emitting modules of the plurality of backlight partitions 15 through one control chip 16, which is beneficial to simplifying the circuit structure of the backlight partitions 15 and reducing the cost.
The embodiment of the present application further provides a backlight structure, which is different from the above embodiments in that the constant current control module and the boosting module corresponding to each backlight partition are disposed in independent control chips, that is, one control chip controls a light emitting module of one backlight partition.
In the foregoing embodiments, the descriptions of the respective embodiments have respective emphasis, and for parts that are not described in detail in a certain embodiment, reference may be made to related descriptions of other embodiments.
The backlight constant-current control circuit and the backlight structure provided by the embodiment of the application are introduced in detail, a specific example is applied in the description to explain the principle and the implementation of the application, and the description of the embodiment is only used for helping to understand the technical scheme and the core idea of the application; those of ordinary skill in the art will understand that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications or substitutions do not depart from the spirit and scope of the present disclosure as defined by the appended claims.
Claims (10)
1. A backlight constant current control circuit is characterized by comprising a light emitting module and a constant current control module;
the constant current control module comprises a first switch unit; the constant current control module is used for adjusting the conduction time and the conduction degree of the first switch unit when detecting that the working current of the light emitting module deviates from the preset current so as to adjust the working current of the light emitting module to the preset current and keep the light emitting brightness of the light emitting module to be the preset light emitting brightness.
2. The backlight constant current control circuit according to claim 1, wherein the constant current control module further comprises a feedback unit and a sampling unit;
the sampling unit is electrically connected with the first switch unit;
the feedback unit is respectively electrically connected with the sampling unit and the first switch unit and used for detecting the voltages at two ends of the sampling unit and determining that the working current of the light-emitting module deviates from the preset current when the voltages at two ends of the sampling unit deviate from the preset voltage, and the conduction time and the conduction degree of the first switch unit are adjusted to adjust the working current of the light-emitting module to the preset current.
3. The backlight constant-current control circuit according to claim 2, wherein the feedback unit includes a level shifter, a first PWM controller, and a comparator;
the comparator is respectively electrically connected with the sampling unit and the first PWM controller and is used for detecting the voltages at two ends of the sampling unit and comparing the voltages at two ends of the sampling unit with the preset voltage; when the voltage at the two ends of the sampling unit deviates from the preset voltage, determining that the working current of the light-emitting module deviates from the preset current, and outputting a level signal to the first PWM controller according to the deviation degree;
the first PWM controller is also electrically connected with the level converter and is used for outputting a duty ratio signal to the level converter according to the level signal;
the level shifter is also electrically connected with the first switch unit and used for adjusting the level of the duty ratio signal and adjusting the conduction time and the conduction degree of the first switch unit through the adjusted duty ratio signal.
4. The backlight constant-current control circuit according to claim 3, wherein the first switching unit includes a first transistor, and the sampling unit includes a sampling resistor;
the drain electrode of the first transistor is electrically connected with the output end of the light-emitting module, the source electrode of the first transistor is grounded through the sampling resistor, and the grid electrode of the first transistor is electrically connected with the output end of the level shifter;
the input end of the comparator is electrically connected with the source electrode of the first transistor, and the output end of the comparator is electrically connected with the input end of the first PWM controller;
and the output end of the first PWM controller is electrically connected with the input end of the level conversion.
5. The backlight constant-current control circuit as claimed in claim 1, wherein the light emitting module includes a plurality of LEDs arranged in series.
6. The backlight constant-current control circuit according to claim 1, further comprising a boosting module electrically connected to an input terminal of the light emitting module;
the boosting module comprises a charging and discharging unit, a second switching unit and a third switching unit; the charging and discharging unit is electrically connected with the second switch unit and the third switch unit respectively;
the boosting module is used for adjusting the conduction time of the second switch unit and the third switch unit according to the preset light-emitting brightness; and when the first switch unit is switched on, the charging and discharging unit is charged, and when the second switch unit is switched on, the charging and discharging unit is discharged, so that a preset power supply voltage is output to the input end of the light-emitting module.
7. The backlight constant current control circuit according to claim 6, wherein the boosting module further comprises a driver and a second PWM controller; the charging and discharging unit comprises an inductor, the second switching unit comprises a second transistor, and the third switching unit comprises a third transistor;
the second PWM controller is electrically connected with the input end of the driver; the input end of the driver is electrically connected with the second PWM controller, and the output end of the driver is respectively electrically connected with the grid electrode of the second transistor and the grid electrode of the third transistor;
one end of the inductor is connected with an input voltage, the other end of the inductor is respectively electrically connected with the drain electrode of the second transistor and the source electrode of the third transistor, the source electrode of the second transistor is grounded, and the drain electrode of the third transistor is electrically connected with the input end of the light emitting module.
8. A backlight structure comprising a plurality of backlight constant current control circuits according to any one of claims 1 to 7; the backlight structure comprises at least one backlight partition, and each backlight partition is provided with at least one light-emitting module of the backlight constant-current control circuit.
9. The backlight structure as claimed in claim 8, wherein a plurality of the constant current control modules in a plurality of the backlight constant current control circuits are integrally disposed in a same control chip.
10. The backlight structure of claim 9, wherein the backlight constant current control circuit further comprises a boost module, and the boost module is also integrated in the control chip.
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011110366.6A CN112233625B (en) | 2020-10-16 | 2020-10-16 | Backlight constant current control circuit and backlight structure |
| PCT/CN2020/139008 WO2022077766A1 (en) | 2020-10-16 | 2020-12-24 | Backlight constant-current control circuit and backlight structure |
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| Application Number | Priority Date | Filing Date | Title |
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| CN202011110366.6A CN112233625B (en) | 2020-10-16 | 2020-10-16 | Backlight constant current control circuit and backlight structure |
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| CN112233625B CN112233625B (en) | 2024-02-09 |
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| CN114783385A (en) * | 2022-04-19 | 2022-07-22 | 惠科股份有限公司 | Backlight module and display device |
| US11763760B1 (en) | 2022-04-02 | 2023-09-19 | Tcl China Star Optoelectronics Technology Co., Ltd. | Backlight module and display device |
| US11854501B1 (en) | 2022-07-20 | 2023-12-26 | Mianyang HKC Optoelectronics Technology Co., Ltd. | Backlight driving circut, backlight module and display device |
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|---|---|
| CN112233625B (en) | 2024-02-09 |
| WO2022077766A1 (en) | 2022-04-21 |
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