CN111028790B - Backlight adjusting circuit, adjusting method and liquid crystal display device - Google Patents
Backlight adjusting circuit, adjusting method and liquid crystal display device Download PDFInfo
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- CN111028790B CN111028790B CN201911251872.4A CN201911251872A CN111028790B CN 111028790 B CN111028790 B CN 111028790B CN 201911251872 A CN201911251872 A CN 201911251872A CN 111028790 B CN111028790 B CN 111028790B
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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
Abstract
The invention discloses a backlight adjusting circuit, an adjusting method and a liquid crystal display device, wherein the backlight adjusting circuit comprises a switching processing circuit, a backlight driving circuit and a backlight adjusting circuit, wherein the switching processing circuit is used for receiving a backlight enabling signal triggering a backlight switch to switch, and outputting the backlight enabling signal to the backlight driving circuit after carrying out time delay processing; the backlight control circuit receives the backlight enable signal and generates a control signal of the backlight illumination intensity according to the backlight enable signal; and the backlight current adjusting circuit receives the control signal and reduces the reference current of the backlight driving circuit according to the control signal so that the backlight driving circuit reduces the backlight illumination intensity according to the reference current before receiving the delayed backlight enabling signal. The invention can effectively avoid the phenomenon of image reddening when the liquid crystal display device is shut down, and improves the display quality of the liquid crystal display device.
Description
Technical Field
The present invention relates to the field of liquid crystal display technologies, and in particular, to a backlight adjusting circuit, an adjusting method, and a liquid crystal display device.
Background
At present, a backlight source of a liquid crystal display device generally uses a Light-Emitting Diode (LED) Light bar, and when a Light bar bead normally works, the backlight source emits white Light.
Because the prior art does not have an LED directly emitting white light, the white light LED is mostly converted from an LED directly emitting blue light, and the conversion is mainly caused by adding a layer of fluorescent powder in a wafer of the blue light LED. From a physical point of view: when current passes through a wafer of the blue LED, electrons in the N-type semiconductor and holes in the P-type semiconductor are combined in the luminous layer to generate blue light, a part of the generated blue light is directly emitted out through the fluorescent coating, the rest part of the generated blue light is irradiated on the fluorescent coating and reacts with the fluorescent coating to generate yellow light, and the blue light and the yellow light are mixed to generate white light.
However, the generation of white light has a problem that the fluorescent powder has a material property of long light-emitting time, for example, it takes 20ms to emit red light, so that an obvious image reddening phenomenon appears immediately before the liquid crystal display device is turned off, and the display quality of the liquid crystal display device is seriously affected.
Disclosure of Invention
In order to solve the problems of the prior art, the present invention provides a backlight adjusting circuit, an adjusting method and a liquid crystal display device, which can effectively avoid the occurrence of the image blushing phenomenon when the liquid crystal display device is turned off, so that the display quality of the liquid crystal display device is improved.
According to a first aspect of the present invention, there is provided a backlight adjusting circuit comprising:
the switching processing circuit receives a backlight enabling signal triggering the backlight switch to switch, and outputs the backlight enabling signal to the backlight driving circuit after time delay processing;
the backlight control circuit receives the backlight enabling signal and generates a control signal of backlight illumination intensity according to the backlight enabling signal;
and the backlight current adjusting circuit receives the control signal and reduces the reference current of the backlight driving circuit according to the control signal, so that the backlight driving circuit reduces the backlight illumination intensity according to the reduced reference current before receiving the delayed backlight enabling signal.
Optionally, the backlight current adjusting circuit includes:
the comparison unit is used for comparing the control signal with a reference voltage to obtain a comparison result signal;
and the switching unit is used for switching the reference current of the backlight driving circuit according to the comparison result signal.
Optionally, the comparing unit includes: a comparator and a fourth resistor, wherein,
the same-direction input end of the comparator is connected with the backlight control circuit to receive the control signal from the backlight control circuit;
the reverse input end of the comparator is a reference voltage interface of the comparison unit;
the fourth resistor is connected in series between the positive power supply port and the output end of the comparator.
Optionally, the backlight driving circuit performs pulse width dimming or direct current dimming, and the backlight driving circuit and the switching unit are connected in series at two ends of the power supply device, where the switching unit includes:
a first branch comprising a fifth resistor;
and the second branch circuit is connected with the first branch circuit in parallel and comprises a sixth resistor and a switching tube which are connected in series, and the switching state of the switching tube is controlled by the comparison result signal.
Optionally, the backlight driving circuit adjusts the light by direct current, and the switching unit includes:
the seventh resistor and the switching tube are connected in series at two ends of the power supply equipment; and
the connecting node between the seventh resistor and the switch tube is connected with the time sequence backlight control circuit corresponding to the backlight driving circuit so as to output a switching enabling signal to the time sequence backlight control circuit,
the switching state of the switching tube is controlled by the comparison result signal, and the switching enable signal is used for adjusting the duty ratio of the pulse width modulation signal received by the timing sequence backlight control circuit.
Optionally, the switching processing circuit includes:
the first resistor is connected between the backlight enable signal input end and the backlight driving circuit in series;
and the first capacitor is connected between the first resistor and a connecting node of the backlight driving circuit in series and the ground.
Optionally, the backlight control circuit comprises:
the second resistor and the third resistor are connected between the backlight enabling signal input end and the ground in series;
and a node between the second resistor and the third resistor is an output end of the control signal.
According to a second aspect of the present invention, there is provided a backlight adjusting method comprising:
outputting the backlight enabling signal triggering the backlight switch to be switched to a backlight driving circuit after carrying out time delay processing;
generating a control signal of backlight illumination intensity according to the backlight enabling signal;
and reducing the reference current of the backlight driving circuit according to the control signal, so that the backlight driving circuit reduces the backlight illumination intensity according to the reduced reference current before receiving the delayed backlight enable signal.
Optionally, reducing the reference current of the backlight driving circuit according to the control signal includes:
within a preset time, gradually adjusting the reference current of the backlight driving circuit from a normal working current to a smaller target current, so that the backlight driving circuit reduces the backlight illumination intensity according to the target current before receiving the backlight enabling signal after the time delay processing.
According to a third aspect of the present invention, there is provided a liquid crystal display device comprising: the backlight driving circuit and the backlight adjusting circuit of the first aspect, wherein the backlight driving circuit and the backlight adjusting circuit are connected to adjust the reference current through the backlight adjusting circuit.
The invention has the beneficial effects that:
the invention adjusts the reference current of the backlight driving circuit based on the backlight enabling signal, and outputs the backlight enabling signal to the backlight driving circuit after the time delay processing, so that the backlight driving circuit reduces the backlight illumination intensity according to the smaller reference current before receiving the backlight enabling signal after the time delay processing, therefore, the red component generated when the backlight excites the fluorescent powder before the backlight is closed can be obviously reduced until the degree which can not be identified by human eyes, thereby effectively avoiding the occurrence of the image reddening phenomenon when the liquid crystal display device is shut down, and improving the display quality of the liquid crystal display device.
Drawings
The above and other objects, features and advantages of the present invention will become more apparent from the following description of the embodiments of the present invention with reference to the accompanying drawings.
Fig. 1 shows a block diagram of a backlight adjusting circuit according to a first embodiment of the present invention;
FIG. 2 is a block diagram showing a first control structure according to a first embodiment of the present invention;
FIG. 3 is a circuit diagram of a first regulation structure in a first embodiment of the present invention;
FIG. 4 shows an analog circuit diagram of a first regulation structure in a first embodiment of the invention;
FIG. 5 shows another analog circuit diagram of the first control structure in the first embodiment of the present invention;
FIG. 6 is a block diagram showing a second control structure according to the first embodiment of the present invention;
FIG. 7 is a circuit diagram showing a second regulation structure in the first embodiment of the present invention;
FIG. 8 illustrates the displayed colors of the white area before and after backlight adjustment according to the present invention;
fig. 9 shows a flowchart of a backlight adjusting method in the second embodiment of the present invention.
Detailed Description
The invention will be described in more detail below with reference to the accompanying drawings. Like elements in the various figures are denoted by like reference numerals. For purposes of clarity, the various features in the drawings are not necessarily drawn to scale. Moreover, certain well-known elements may not be shown in the figures.
In the following description, numerous specific details of the invention, such as structure, materials, dimensions, processing techniques and techniques of the devices are described in order to provide a more thorough understanding of the invention. However, as will be understood by those skilled in the art, the present invention may be practiced without these specific details.
Embodiments of the present invention are specifically described below with reference to the accompanying drawings.
Fig. 1 shows a backlight adjusting circuit 100 according to a first embodiment of the present invention, including:
the switching processing circuit 110 receives a backlight enable signal EN triggering the backlight switch to switch, performs delay processing on the backlight enable signal EN, and outputs the delayed backlight enable signal EN to the backlight driving circuit 200, wherein the backlight driving circuit 200 controls the backlight switch according to the delayed backlight enable signal EN';
the backlight control circuit 120 receives the backlight enable signal EN and generates a control signal CON for controlling the intensity of backlight illumination according to the backlight enable signal EN.
The backlight current adjusting circuit 130 receives the control signal CON and reduces the reference current of the backlight driving circuit 200 according to the control signal CON, so that the backlight driving circuit 200 reduces the backlight illumination intensity according to the reduced reference current before receiving the delayed backlight enable signal EN'.
Specifically, the backlight driving circuit generates a smaller back photocurrent corresponding to a smaller backlight illumination intensity, i.e., corresponding to a darker screen of the display device, according to a smaller reference current. It should be understood that the smaller reference current is to reduce the illumination intensity of the backlight before the liquid crystal display device is turned off, so as to reduce the light emitting intensity of the phosphor layer to reduce the phenomenon of obvious red-burning of the image caused by the long light emitting time of the phosphor, but the backlight driving circuit 200 still generates the backlight current according to the smaller reference current, so that the smaller reference current adjusted by the backlight driving circuit 200 has a lower threshold.
It should be emphasized that, referring to fig. 1, the switching processing circuit 110 and the backlight control circuit 120 receive the backlight enable signal EN at the same time, wherein the switching processing circuit delays the backlight enable signal EN and sends the delayed backlight enable signal EN to the backlight driving circuit 200, the backlight control circuit 120 generates the control signal CON according to the backlight enable signal EN and the backlight current adjusting circuit 130 decreases the reference current of the backlight driving circuit 200 according to the control signal CON, so that the reference current of the backlight driving circuit 200 decreases before the backlight driving circuit receives the delayed backlight enable signal EN ', and the backlight intensity of the backlight adjusting circuit 100 is decreased before the backlight adjusting circuit is controlled to be turned off by the delayed backlight enable signal EN'.
The backlight adjusting circuit 100 provided by the embodiment of the invention reduces the illumination intensity before the backlight is turned off, so that the red component generated when the backlight excites the fluorescent powder is obviously reduced until the degree that human eyes can not recognize, thereby effectively avoiding the phenomenon of instant image reddening before the liquid crystal display device is turned off and improving the display quality of the liquid crystal display device.
At present, a liquid crystal display device modulates screen brightness by Pulse Width Modulation (PWM) or Direct Current (DC) through a backlight driving circuit, and what needs to be described is:
(1) the pulse width modulation (also called PWM) dimming is adopted to control the current on-off time ratio of the LED lamp based on the duty ratio of the pulse width modulation signal, namely the on-off time ratio of the LED lamp, and if the LED lamp is on for a longer time in a unit period, the screen seen by human eyes is brighter. However, it should be noted that in the dimming manner, the brightness of the LED lamp in the lighting phase is determined by the backlight current, and thus, under the condition that the backlight current is not changed, the brightness of the LED lamp in the lighting phase is not changed, that is, the screen brightness is not changed in a period of time during which the LED lamp is continuously lighted.
(2) The screen brightness is modulated by adopting direct current (also called direct current dimming), the brightness of the LED lamp is controlled through the magnitude of backlight current, so that the screen brightness is controlled, the magnitude of the backlight current is determined by the duty ratio of a pulse width modulation signal, and if the duty ratio of the pulse width modulation signal is larger, the backlight current is larger.
Therefore, if the illumination intensity of the backlight is to be reduced in a short time before the liquid crystal display device is turned off, the effective method of the PWM dimming is to reduce the backlight current; an effective method of direct current dimming includes not only directly reducing the backlight current but also reducing the pulse width modulation signal input to the backlight driving circuit to indirectly reduce the backlight current. Based on this, the embodiment of the present invention designs the first regulation structure shown in fig. 2 for PWM dimming and dc dimming to directly reduce the backlight current of the backlight driving circuit 200; a second regulation structure as shown in fig. 6 is also designed for dc dimming to indirectly reduce the backlight current of the backlight driving circuit 200.
Referring to fig. 2, in the first regulation structure, the backlight current adjusting circuit 130 reduces the reference current I according to the control signal CON0And applying the reference current I0Is input into the backlight driving circuit 200, and the backlight driving circuit 200 is driven by the reference current I0Generating a smaller back photocurrent; while the timing backlight control circuit TCON corresponding to the backlight driving circuit 200 is not controlled by the backlight current adjusting circuit 130,the pulse width modulation signal PWMO output by the timing backlight control circuit and the received pulse width modulation signal PWMI have the same duty ratio.
Referring to fig. 6, in the second regulation and control structure, the backlight current adjusting circuit 130 generates a switching enable signal DBC _ EN according to the control signal CON, and the switching enable signal DBC _ EN is input to the timing backlight control circuit TCON corresponding to the backlight driving circuit 200 and is used for adjusting the duty ratio of the pulse width modulation signal PWMI received by the timing backlight control circuit TCON, so as to realize indirect adjustment of the backlight current of the backlight driving circuit 200 by changing the duty ratio of the pulse width modulation signal PWMO output by the timing backlight control circuit TCON. Specifically, the switching enable signal DBC _ EN may control whether the timing backlight control circuit TCON starts the duty ratio switching function through a level state, wherein after the timing backlight control circuit TCON starts the duty ratio switching function, the timing backlight control circuit TCON outputs the duty ratio D of the pulse width modulation signal PWMO2Less than the duty cycle D of the received pulse width modulated signal PWMI1E.g. D2＝D1X n%, wherein the value range of n is more than 0 and less than 100, and the value of n can be set in the range as required; otherwise, after the time sequence backlight control circuit TCON does not start the duty ratio switching function, D is carried out2＝D1。
Referring to fig. 2 or fig. 6, in both of the above two control structures, the switching processing circuit 110 may adopt an RC switching processing circuit, and the switching processing circuit 110 includes: a first resistor R1 connected in series between the input terminal of the backlight enable signal EN (the output terminal of the connector 300 to the backlight enable signal EN as shown in fig. 2) and the backlight driving circuit 200; and a first capacitor C1 connected in series between the first resistor R1 and the connection node P1 of the backlight driving circuit 200 and ground, wherein the switching processing circuit 110 utilizes the energy storage characteristic of the first capacitor C1 to implement the delay processing of the backlight enable signal EN.
Fig. 3 shows the backlight control circuit 120 and the backlight current adjusting circuit 130 corresponding to the first adjustment structure, and fig. 7 shows the backlight control circuit 120 and the backlight current adjusting circuit 130 corresponding to the second adjustment structure.
Referring to fig. 3 or 7, the backlight control circuit 120 may include: a second resistor R2 and a third resistor R3 connected in series between the input terminal of the backlight enable signal EN and the ground; and a node P2 between the second resistor R2 and the third resistor R3 is an output terminal of the control signal CON. Specifically, if the backlight enable signal EN is at a high level, the control signal CON is at a high level; if the backlight enable signal EN is at a low level, the control signal CON is at a low level.
Referring to fig. 3 or 7, the backlight current adjusting circuit 130 may include: a comparing unit 131, configured to compare the control signal CON with a reference voltage Vref to obtain a comparison result signal CR; and a switching unit 132 for switching the magnitude of the reference current of the backlight driving circuit 200 according to the comparison result signal CR.
Specifically, the comparing unit 131 may include: a comparator U1A and a fourth resistor R4, wherein the same-direction input terminal of the comparator U1A is connected to the backlight control circuit 120 to receive the control signal CON from the backlight control circuit 120; the reverse input end of the comparator U1A is a reference voltage interface of the comparison unit; the fourth resistor R4 is connected in series between the positive supply port VCC and the output terminal of the comparator U1A, and the comparator U1A may be a comparator of the type LM 139W. Based on this, if the control signal CON is at a high level and the control signal CON is greater than the reference voltage Vref, the comparison result signal CR is at a high level; if the control signal CON is at a low level and the control signal CON is smaller than the reference voltage Vref, the comparison result signal CR is at a low level.
The switching unit 132 is connected to the backlight driving circuit 200, and the switching unit 132 is different between the two control structures.
(I) first regulating structure
Referring to fig. 3, in the first regulation and control structure, the switching unit 132 and the backlight driving circuit 200 are connected in series at two ends of the power supply device, and the switching unit 132 includes a first branch and a second branch connected in parallel between the interface ISET and the ground, where the first branch includes a fifth resistor R5; the second branch circuit comprises a sixth resistor R6 and a switching tube Q1 which are connected in series, and the switching state of the switching tube Q1 is controlled by a comparison result signal CR.
Optionally, the switching tube Q1 is an NMOS tube (for example, an NMOS tube with model 2SK 2978), the gate of the switching tube Q1 is connected to the output terminal of the comparator U1A to receive the comparison result signal CR, the drain of the switching tube Q1 is connected to the sixth resistor R6, and the source of the switching tube Q1 is grounded, so that the switching tube Q1 is in an open state when the comparison result signal CR is at a low level, and the switching tube Q1 is in a closed state when the comparison result signal CR is at a high level, as seen by comparison: when the comparison result signal CR is at a low level, the reference current input to the backlight driving circuit 200 by the switching unit 132 is small.
It should be noted that, the backlight enable signal EN is a signal for controlling the backlight switch, based on the specific circuit diagrams of the backlight control circuit 120 and the adjustment circuit 130, if the high-level backlight enable signal EN controls the backlight to be turned on and the low-level backlight enable signal EN controls the backlight to be turned off, after the backlight driving circuit 200 receives the backlight enable signal EN 'after the delay processing, if the received signal EN' is a low level, the backlight is controlled to be turned off, and the illumination of the backlight is adjusted to be low according to a smaller reference current before the backlight is turned off, so that the occurrence of the image blush phenomenon when the image is turned off is avoided.
Fig. 4 and 5 are analog circuits for setting the backlight enable signal EN at different potentials in the first regulation structure, where fig. 4 realizes the simulation of the low-potential backlight enable signal EN by connecting the contact S1 through the key J1, and fig. 5 realizes the simulation of the high-potential backlight enable signal EN by connecting the contact S2 through the key J1. If the parameters of each element in fig. 4 and 5 are set as follows: the high potential voltage V1 of the backlight enable signal EN is 3.3V, and the low potential voltage is 0V; r2 is 20k Ω, R3 is 112k Ω, Vref is 2.8V, R5 is 1k Ω, R6 is 0.1k Ω, and the voltage V2 of the power supply device in the switching unit 132 is 3.3V, which are obtained through simulation, and the ammeter XMM2 in fig. 4 shows a reference current of 3.303mA, and the ammeter XMM2 in fig. 5 shows a reference current of 19.777mA, as shown in: when the backlight enable signal EN is pulled from the high potential simulated in fig. 5 to the low potential simulated in fig. 4, the reference current decreases.
It should be understood that the above description is only exemplary of the setting of parameter values for each element in the first control structure and does not represent a limitation on the parameter values for each element in the first control structure. When the values of the backlight enable signal EN, the second resistor R2 and the third resistor R3 are different, the same level correspondence between the control signal CON and the comparison result signal CR can be realized by changing the value of the reference voltage Vref; similarly, when the high and low reference currents required by the backlight driving circuit 200 are different, the voltage V2 of the power supply device and the resistances of the fifth resistor R5 and the sixth resistor R6 may be set appropriately.
(II) second regulating structure
Referring to fig. 7, the switching unit 132 in the second regulation structure includes: a seventh resistor R7 and a switch tube Q2 which are connected in series at two ends of the power supply device (namely, the anode VCC of the power supply device and the ground); and a connection node P3 between the seventh resistor R7 and the switching tube Q2 is connected to the timing backlight control circuit TCON corresponding to the backlight driving circuit 200 to output a switching enable signal DBC _ EN to the timing backlight control circuit TCON, and the switching state of the switching tube Q2 is controlled by the comparison result signal CR.
Optionally, the switching transistor Q2 is an NMOS transistor, and its gate is connected to the output terminal of the comparator U1A to receive the comparison result signal CR; the drain electrode is connected with the seventh resistor R7, and a node P3 between the drain electrode and the seventh resistor R7 is an output end of the switching enable signal DBC _ EN; the source is grounded, so that the switch Q2 is in an open state when the comparison result signal CR is low, and the switch Q2 is in a closed state when the comparison result signal CR is high, as shown by comparison: when the comparison result signal CR is at a low level, the switching enable signal DBC _ EN is at a high level.
In an example, the high-level switching enable signal DBC _ EN turns on the duty switching function of the sequential backlight control circuit TCON, and based on the specific circuit diagrams of the backlight control circuit 120 and the adjusting circuit 130, if the high-level backlight enable signal EN controls the backlight to be turned on and the low-level backlight enable signal EN controls the backlight to be turned off, after the backlight driving circuit 200 receives the backlight enable signal EN 'after the delay processing, if the received signal EN' is at a low level, the backlight is controlled to be turned off, and the duty ratio D of the pulse width modulation signal PWMO received before the backlight is turned off is controlled to be at a duty ratio D2Has been adjusted to be less than D1That is, the backlight driving circuit 200 has turned the illumination of the backlight down according to the smaller reference current, thereby avoiding the off-stateThe phenomenon of reddening of the images at times occurs.
The backlight adjusting circuit provided by the first embodiment of the invention obviously improves the problem of backlight reddening by carrying an actual circuit, actually taking a picture, recording a video and observing human eyes. Fig. 8 shows colors displayed in the white region before and after the backlight adjustment by the CIE-1931-chromaticity diagram, in which the sum of colors displayed in the liquid crystal display device under the NTSC standard is located within a triangular region, the color displayed in the white region before the backlight adjustment corresponds to a point M1 in the CIE-1931-chromaticity diagram, and the color displayed in the white region after the backlight adjustment corresponds to a point M2 in the CIE-1931-chromaticity diagram. Referring to fig. 8, the color coordinate of the point M1 is: x-0.4775 and y-0.3073, the color coordinates of point M2 are: x-0.3275 and y-0.3082, i.e. the white area is displayed with colors far from the lower right corner of the triangular area after backlight adjustment, as can be seen: the displayed color of the white area is closer to white after backlight adjustment, and the phenomenon of image redness during shutdown is effectively avoided.
Fig. 9 shows a flowchart of a backlight adjusting method according to a second embodiment of the invention. Referring to fig. 9, the backlight adjusting method includes:
step S101, outputting a backlight enabling signal triggering the backlight switch to a backlight driving circuit after time delay processing;
step S102, generating a control signal of backlight illumination intensity according to the backlight enable signal;
and step S103, reducing the reference current of the backlight driving circuit according to the control signal, so that the backlight driving circuit reduces the backlight illumination intensity according to the reduced reference current before receiving the delayed backlight enabling signal.
The backlight adjusting method provided by the embodiment of the invention enables the illumination intensity to be reduced before the backlight is closed, so that the red component generated when the backlight excites the fluorescent powder can be obviously reduced until the degree can not be identified by human eyes, thereby effectively avoiding the occurrence of the phenomenon of image reddening when the liquid crystal display device is shut down and improving the display quality of the liquid crystal display device.
In an alternative embodiment, the step S103 of reducing the reference current of the backlight driving circuit according to the control signal includes: within a preset time, the reference current of the backlight driving circuit is gradually adjusted to a smaller target current from the normal working current, so that the backlight driving circuit reduces the backlight illumination intensity according to the target current before receiving the backlight enabling signal after the time delay processing.
Specifically, the normal operating current is a reference current of the backlight driving circuit when the liquid crystal display device normally displays before backlight adjustment, and the target current is a reference current of the backlight driving circuit when no reddish image appears in the liquid crystal display device after backlight adjustment.
It should be understood that the preset time period is less than the time period when the backlight enable signal is delayed.
In the embodiment of the invention, the reference current of the backlight driving circuit is gradually adjusted to a smaller target current from the normal working current within the preset time, and the liquid crystal display device is shut down when the image becomes dark from bright to dark and is not easy to be perceived, so that the phenomenon of instant image reddening before the liquid crystal display device is shut down is avoided, the sudden change of the image brightness of the liquid crystal display device is avoided, and the display quality of the liquid crystal display device is further improved.
In view of the backlight adjusting circuit provided in the first embodiment of the present invention, a third embodiment of the present invention further provides a liquid crystal display device, which includes not only the conventional backlight driving circuit but also the backlight adjusting circuit of the first embodiment, wherein the backlight driving circuit is connected to the backlight adjusting circuit to adjust the reference current through the backlight adjusting circuit, thereby preventing the occurrence of the phenomenon of image blushing when the liquid crystal display device is turned off.
It is noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
While embodiments in accordance with the invention have been described above, these embodiments are not intended to be exhaustive or to limit the invention to the precise embodiments described. Obviously, many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and the practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. The invention is limited only by the claims and their full scope and equivalents.
Claims (9)
1. A backlight adjustment circuit, comprising:
the switching processing circuit receives a backlight enabling signal triggering the backlight switch to switch, and outputs the backlight enabling signal to the backlight driving circuit after time delay processing;
the backlight control circuit receives the backlight enabling signal and generates a control signal of backlight illumination intensity according to the backlight enabling signal;
the backlight current adjusting circuit receives the control signal and reduces the reference current of the backlight driving circuit according to the control signal so that the backlight driving circuit reduces the backlight illumination intensity according to the reduced reference current before receiving the backlight enabling signal after the time delay processing; wherein the content of the first and second substances,
the backlight current adjusting circuit includes:
the comparison unit is used for comparing the control signal with a reference voltage to obtain a comparison result signal;
and the switching unit is used for switching the reference current of the backlight driving circuit according to the comparison result signal.
2. The backlight adjustment circuit according to claim 1, wherein the comparison unit comprises: a comparator and a fourth resistor, wherein,
the same-direction input end of the comparator is connected with the backlight control circuit to receive the control signal from the backlight control circuit;
the reverse input end of the comparator is a reference voltage interface of the comparison unit;
the fourth resistor is connected in series between the positive power supply port and the output end of the comparator.
3. The backlight adjusting circuit according to claim 1, wherein the backlight driving circuit performs pulse width dimming or direct current dimming, and the backlight driving circuit and the switching unit are connected in series across a power supply device, wherein the switching unit comprises:
a first branch comprising a fifth resistor;
and the second branch circuit is connected with the first branch circuit in parallel and comprises a sixth resistor and a switching tube which are connected in series, and the switching state of the switching tube is controlled by the comparison result signal.
4. The backlight adjusting circuit according to claim 1, wherein the backlight driving circuit adjusts the light by direct current, and the switching unit comprises:
the seventh resistor and the switching tube are connected in series at two ends of the power supply equipment; and
the connecting node between the seventh resistor and the switch tube is connected with the time sequence backlight control circuit corresponding to the backlight driving circuit so as to output a switching enabling signal to the time sequence backlight control circuit,
the switching state of the switching tube is controlled by the comparison result signal, and the switching enable signal is used for adjusting the duty ratio of the pulse width modulation signal received by the timing sequence backlight control circuit.
5. The backlight adjustment circuit of claim 1, wherein the switching processing circuit comprises:
the first resistor is connected between the backlight enable signal input end and the backlight driving circuit in series;
and the first capacitor is connected between the first resistor and a connecting node of the backlight driving circuit in series and the ground.
6. The backlight adjustment circuit of claim 1, wherein the backlight control circuit comprises:
the second resistor and the third resistor are connected between the backlight enabling signal input end and the ground in series;
and a node between the second resistor and the third resistor is an output end of the control signal.
7. A backlight adjustment method, comprising:
outputting the backlight enabling signal triggering the backlight switch to be switched to a backlight driving circuit after carrying out time delay processing;
generating a control signal of backlight illumination intensity according to the backlight enabling signal;
and comparing the control signal with the reference voltage to obtain a comparison result signal, and switching the reference current of the backlight driving circuit according to the comparison result signal, so that the backlight driving circuit reduces the backlight illumination intensity according to the reduced reference current before receiving the backlight enabling signal after the time delay processing.
8. The backlight adjustment method according to claim 7, wherein switching the reference current of the backlight driving circuit according to the comparison result signal comprises:
within a preset time, gradually adjusting the reference current of the backlight driving circuit from a normal working current to a smaller target current, so that the backlight driving circuit reduces the backlight illumination intensity according to the target current before receiving the backlight enabling signal after the time delay processing.
9. A liquid crystal display device, comprising: a backlight driver circuit and the backlight conditioning circuit of any of claims 1-6, wherein the backlight driver circuit and the backlight conditioning circuit are connected to condition a reference current through the backlight conditioning circuit.
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| CN113450727B (en) * | 2021-06-25 | 2022-11-11 | 京东方科技集团股份有限公司 | Driving circuit and driving method of display device |
| CN114071268B (en) * | 2021-12-13 | 2024-03-01 | 中国电子科技集团公司第四十四研究所 | GPON digital optical module quick start circuit and quick start method |
| CN115083358A (en) * | 2022-07-05 | 2022-09-20 | 珠海格力电器股份有限公司 | Display panel backlight control circuit and control method |
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| CN102682718B (en) * | 2012-05-11 | 2015-01-21 | 深圳市华星光电技术有限公司 | Backlight module of liquid crystal display screen and control method thereof |
| CN103761953B (en) * | 2014-01-28 | 2016-04-06 | 北京京东方显示技术有限公司 | A kind of indicative control unit and display device |
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