Liquid crystal display device and backlight driving method thereof

Abstract

This application provides a liquid crystal display device and its backlight driving method. The liquid crystal display device includes a liquid crystal display panel, a backlight module, a control chip, and a driving chip. The backlight module includes a light guide plate, a first LED strip, and a second LED strip, which are disposed on the side of the light guide plate. The driving chip generates a first pulse width modulation signal and a second pulse width modulation signal with a phase difference of 180° based on the control signal from the control chip, and adjusts the driving current flowing through the first and second LED strips respectively. A brightness sensor detects the brightness at multiple locations on the backlight module, obtaining multiple brightness data. The control chip calculates the ratio of the average edge brightness to the center brightness value based on the multiple brightness data, and adjusts the driving current of the two LED strips accordingly. This technical solution effectively solves the technical problem of poor backlight brightness uniformity caused by single-LED-strip driving schemes.

Description

Technical Field

[0001] This application relates to the field of display technology, specifically to a liquid crystal display device and its backlight driving method. Background Technology

[0002] Side-lit backlight modules in LCD displays achieve uniform light diffusion by arranging LED strips along the edge of the light guide plate. The LED strips use packaged LED chips, whose light propagates laterally guided by dots on the light guide plate. The stacking of multiple optical films compensates for brightness attenuation from the edge to the center of the light guide plate. Furthermore, the LED strips typically employ pulse-width modulation (PWM) dimming technology, coupled with a constant current source circuit to stabilize the current output.

[0003] However, existing edge-lit backlight modules in LCD devices typically employ a single-lamp-strip driving scheme. Due to the difference in optical path from the edge to the center of the light guide plate, a significant brightness difference occurs between the center and edge areas of the light-emitting surface, often exceeding 20%, affecting the uniformity of the display. Traditional solutions involve increasing the thickness of the light guide plate or using multi-layer optical films for compensation, but these solutions increase the overall thickness and cost of the LCD device. Furthermore, in single-lamp-strip driving schemes, the pulse-width modulation (PWM) dimming frequency is typically low due to switching frequency limitations, easily producing visible flicker and impacting the user's visual experience. Additionally, single-lamp-strip driving schemes have low reliability; if a lamp fails, the entire backlight module becomes completely unusable. Moreover, single-lamp-strip driving schemes cannot dynamically adjust according to the content displayed on the LCD device, causing non-display areas to continue consuming power, resulting in low overall energy efficiency.

[0004] Therefore, it is necessary to propose a new technical solution to solve the above-mentioned technical problems. Summary of the Invention

[0005] The purpose of this application is to provide a liquid crystal display device and its backlight driving method, which aims to solve the technical problem of poor backlight brightness uniformity caused by the single lamp bar driving scheme in the prior art.

[0006] An embodiment of this application provides a liquid crystal display device, the liquid crystal display device comprising: a liquid crystal display panel; a backlight module, the backlight module comprising a light guide plate, a first lamp strip and a second lamp strip, the first lamp strip and the second lamp strip being disposed on the side of the light guide plate; a control chip; and a driver chip electrically connected to the control chip, the driver chip being configured to generate a first pulse width modulation signal and a second pulse width modulation signal according to a control signal from the control chip, and to adjust the driving current flowing through the first lamp strip according to the first pulse width modulation signal, and to adjust the driving current flowing through the second lamp strip according to the second pulse width modulation signal, wherein the phase difference between the first pulse width modulation signal and the second pulse width modulation signal is 180°.

[0007] In the aforementioned liquid crystal display device, the liquid crystal display device further includes: a brightness sensor, the brightness sensor being configured to detect the brightness at multiple locations of the backlight module to obtain multiple brightness data; wherein, the control chip is electrically connected to the brightness sensor, the control chip being configured to read the multiple brightness data detected by the brightness sensor at predetermined intervals, and to adjust the driving current flowing through the first lamp strip and the driving current flowing through the second lamp strip according to the multiple brightness data.

[0008] In the aforementioned liquid crystal display device, the control chip is configured to calculate the average edge brightness and center brightness of the backlight module based on multiple brightness data, and to calculate the ratio of the average edge brightness to the center brightness; the driving chip is configured to adjust the driving current flowing through the first LED strip and the driving current flowing through the second LED strip according to the ratio.

[0009] In the aforementioned liquid crystal display device, the driving chip is configured to increase the driving current flowing through at least one of the first and second light bars when the ratio is greater than 1.15, decrease the driving current flowing through at least one of the first and second light bars when the ratio is less than 0.95, and maintain the driving current flowing through the first and second light bars at the current value when the ratio is in the range of 0.95 to 1.15.

[0010] In the aforementioned liquid crystal display device, the control chip is configured to calculate the target drive current according to the following formula: I2 = I1 × k × (L target / L edge )^(1.8); where I1 is the current drive current, I2 is the target drive current, and L target L is the preset brightness value of the image to be displayed on the liquid crystal display panel. edge Let k be the average edge brightness of the backlight module, and k is a constant.

[0011] In the aforementioned liquid crystal display device, when the ratio is greater than 1.15, the driving chip adjusts the target driving current to 1.1 to 1.4 times the current driving current; when the ratio is less than 0.95, the driving chip adjusts the target driving current to 0.6 to 0.9 times the current driving current; and when the ratio is in the range of 0.95 to 1.15, the driving chip adjusts the target driving current to 0.9 to 1.1 times the current driving current.

[0012] In the aforementioned liquid crystal display device, the liquid crystal display device further includes: a first current sensing resistor electrically connected to the first lamp strip; a second current sensing resistor electrically connected to the second lamp strip; and an error amplifier electrically connected to the first current sensing resistor and the second current sensing resistor, the error amplifier being configured to compare the detection result of the first current sensing resistor with a reference voltage, and to compare the detection result of the second current sensing resistor with the reference voltage, and output the comparison result to the driver chip.

[0013] In the aforementioned liquid crystal display device, the liquid crystal display device further includes: a first switch, the control terminal of the first switch being electrically connected to the driver chip and receiving the first pulse width modulation signal, the input terminal of the first switch being electrically connected to the constant current power supply of the liquid crystal display device, the output terminal of the first switch being electrically connected to the first LED strip, and the first switch being configured to adjust the driving current flowing through the first LED strip according to the first pulse width modulation signal; and a second switch, the control terminal of the second switch being electrically connected to the driver chip and receiving the second pulse width modulation signal, the input terminal of the second switch being electrically connected to the constant current power supply of the liquid crystal display device, the output terminal of the second switch being electrically connected to the second LED strip, and the second switch being configured to adjust the driving current flowing through the second LED strip according to the second pulse width modulation signal.

[0014] In the aforementioned liquid crystal display device, a plurality of brightness sensors are disposed in the backlight module, and one brightness sensor corresponds to one backlight zone of the backlight module.

[0015] An embodiment of this application also provides a backlight driving method for a liquid crystal display device, characterized in that the method includes: a driving chip generating a first pulse width modulation signal and a second pulse width modulation signal according to a control signal from a control chip, wherein the phase difference between the first pulse width modulation signal and the second pulse width modulation signal is 180°; and the driving chip adjusting the driving current flowing through a first lamp strip according to the first pulse width modulation signal, and adjusting the driving current flowing through a second lamp strip according to the second pulse width modulation signal.

[0016] In the aforementioned backlight driving method, before the driving chip generates the first pulse width modulation signal and the second pulse width modulation signal according to the control signal of the control chip, the method further includes: a brightness sensor detecting the brightness of multiple positions of the backlight module to obtain multiple brightness data; the control chip calculating the average edge brightness value and the center point brightness value of the backlight module based on the multiple brightness data; the control chip calculating the ratio of the average edge brightness value to the center point brightness value; and the control chip generating the control signal for adjusting the driving current flowing through the first LED strip and the driving current flowing through the second LED strip based on the ratio.

[0017] In the aforementioned backlight driving method, the driver chip adjusts the driving current flowing through the first LED strip according to the first pulse width modulation signal, and adjusts the driving current flowing through the second LED strip according to the second pulse width modulation signal, including: when the ratio is greater than 1.15, the driver chip increases the driving current flowing through at least one of the first LED strip and the second LED strip; when the ratio is less than 0.95, the driver chip decreases the driving current flowing through at least one of the first LED strip and the second LED strip; and when the ratio is in the range of 0.95 to 1.15, the driver chip maintains the current value of the driving current flowing through the first LED strip and the second LED strip.

[0018] In the aforementioned backlight driving method, the driving chip adjusts the driving current flowing through the first lamp strip according to the first pulse width modulation signal, and adjusts the driving current flowing through the second lamp strip according to the second pulse width modulation signal, including: when the ratio is greater than 1.15, the driving chip adjusts the target driving current to 1.1 to 1.4 times the current driving current; when the ratio is less than 0.95, the driving chip adjusts the target driving current to 0.6 to 0.9 times the current driving current; and when the ratio is in the range of 0.95 to 1.15, the driving chip adjusts the target driving current to 0.9 to 1.1 times the current driving current.

[0019] In the aforementioned backlight driving method, the method further includes calculating the target driving current according to the following formula: I2=I1×k×(L target / L edge )^(1.8); where I1 is the current drive current, I2 is the target drive current, and L target L is the preset brightness value of the image to be displayed on the liquid crystal display panel. edge Let k be the average edge brightness of the backlight module, and k is a constant.

[0020] In the above-described backlight driving method, after the brightness sensor detects the brightness at multiple locations of the backlight module and obtains multiple brightness data, and before the control chip calculates the average edge brightness and center point brightness value of the backlight module based on the multiple brightness data, the method further includes: the control chip reading the multiple brightness data at predetermined intervals.

[0021] In the above-described backlight driving method, the method further includes: sampling the driving current flowing through the first lamp strip and the second lamp strip respectively through a first current sensing resistor and a second current sensing resistor; comparing the sampled driving current with a reference voltage through an error amplifier to obtain a comparison result; and feeding the comparison result back to the driving chip.

[0022] In the aforementioned backlight driving method, the driving chip adjusting the driving current flowing through the first lamp strip according to the first pulse width modulation signal and adjusting the driving current flowing through the second lamp strip according to the second pulse width modulation signal includes: the driving chip controlling a first switch through the first pulse width modulation signal, such that the first switch adjusts the driving current flowing through the first lamp strip; and the driving chip controlling a second switch through the second pulse width modulation signal, such that the second switch adjusts the driving current flowing through the second lamp strip.

[0023] The liquid crystal display device provided in this application effectively solves the technical problem of poor backlight brightness uniformity caused by the single-lamp-strip driving scheme in the prior art by using a dual-lamp-strip phase-interleaved driving technology. This technology sets the first and second lamp strips on opposite sides of the light guide plate, achieving bidirectional light injection compared to the traditional single-lamp-strip scheme which only sets one side of the light guide plate. In the traditional single-lamp-strip scheme, light only enters from one side of the light guide plate. During propagation in the light guide plate, due to absorption and scattering losses, a significant brightness attenuation gradient occurs from the light source side to the opposite side, with the brightness difference between the center and edge areas typically exceeding 20%. The dual-lamp-strip scheme of this application, by simultaneously providing light sources on opposite sides of the light guide plate, allows light to converge from both directions to the center area of ​​the light guide plate, effectively compensating for light loss during unidirectional propagation and significantly improving the brightness distribution uniformity of the backlight module's light-emitting surface.

[0024] In this technical solution, the driver chip generates a first pulse width modulation signal and a second pulse width modulation signal with a phase difference of 180°, which control the driving current of the first and second light strips respectively. This enables the two light strips to work alternately, complementing each other in time and ensuring that the light guide plate always has light input. This phase-interleaved working mode avoids the light interference effect that may occur when the two light strips are turned on simultaneously. At the same time, through light modulation in the time dimension, it further optimizes the light distribution characteristics in the light guide plate, helping to reduce local over-brightness or under-brightness.

[0025] A brightness sensor continuously monitors the brightness at multiple locations on the backlight module, generating multiple brightness data points. The control chip calculates the average edge brightness and the center brightness value based on this data, and then calculates the ratio between the two. When the ratio is greater than 1.15, it indicates that the center area is too bright relative to the edge area. The control chip increases the drive current flowing through at least one of the first and second LED strips via the driver chip, enhancing light compensation for the edge area. When the ratio is less than 0.95, it indicates that the edge area is too bright relative to the center area. The control chip reduces the drive current of the corresponding LED strip via the driver chip, weakening the light input intensity to the edge area. When the ratio is between 0.95 and 1.15, it indicates that the brightness distribution is ideal, and the driver chip maintains the current of the two LED strips at their current values. This adaptive adjustment scheme based on real-time brightness detection can dynamically adjust the current distribution of the two LED strips according to the actual brightness distribution, achieving light compensation for different areas of the light guide plate.

[0026] The dual-path pulse-width modulation (PWM) signal driving scheme with a 180° phase difference also achieves flicker suppression. Because the two LED strips work alternately, with one strip always active, this continuous light output mode effectively reduces light interruptions caused by PWM switching, lowering the perceptible flicker. Simultaneously, the alternating operation of the two LED strips disperses the electromagnetic interference spectrum, avoiding energy concentration at a single frequency and reducing the peak intensity of electromagnetic interference. Furthermore, the dual-LED configuration provides redundancy protection; if one LED strip fails, the other can continue operating, ensuring the basic display function of the LCD device and significantly improving the reliability of the backlight module. Attached Figure Description

[0027] Figure 1 A block diagram of a liquid crystal display device provided for an embodiment of this application.

[0028] Figure 2 Waveforms of the first pulse width modulation signal and the second pulse width modulation signal of the liquid crystal display device provided in the embodiments of this application.

[0029] Figure 3 A flowchart of a backlight driving method for a liquid crystal display device provided in an embodiment of this application.

[0030] Figure 4 for Figure 3 The flowchart shown illustrates the steps by which the control chip generates control signals to adjust the drive current flowing through the first LED strip and the drive current flowing through the second LED strip based on this ratio. Detailed Implementation

[0031] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0032] The terms “first,” “second,” and similar words do not indicate any order, quantity, or importance, but are merely used to distinguish different technical features. The terms “multiple,” and similar words mean two or more, unless otherwise expressly specified.

[0033] The embodiments of this application can be combined with each other.

[0034] The embodiments of this application provide a liquid crystal display device that adopts a dual lamp bar driving technology based on phase interleaving modulation, which effectively solves the technical problems of poor backlight brightness uniformity, obvious flicker, low reliability and high power consumption in liquid crystal display devices.

[0035] like Figure 1 As shown, the liquid crystal display device includes a liquid crystal display panel, a backlight module, a brightness sensor, a control chip, and a driver chip. The liquid crystal display panel includes a display area and a non-display area. The display area has an array of m×n pixels, where m and n are integers greater than 1. The non-display area is located around the periphery of the display area and is used to arrange gate drive signal generation circuits and various signal lines. The liquid crystal display panel also includes multiple gate lines and multiple data lines. The gate lines extend along a first direction and are arranged along a second direction, while the data lines extend along the second direction and are arranged along the first direction, with the first direction perpendicular to the second direction.

[0036] A liquid crystal display panel includes a thin-film transistor array substrate, a counter substrate, and a liquid crystal layer disposed between the two substrates. The thin-film transistor array substrate includes a first glass substrate, a first metal layer disposed on the first glass substrate, a gate insulating layer disposed on the first metal layer, a semiconductor layer disposed on the gate insulating layer, a second metal layer disposed on the semiconductor layer, a passivation layer disposed on the second metal layer, and a pixel electrode disposed on the passivation layer. The first metal layer includes a gate line and a gate electrode, and the second metal layer includes a data line, a source electrode, and a drain electrode. The counter substrate includes a second glass substrate, a black matrix disposed on the second glass substrate, a color filter layer disposed on the black matrix, and a common electrode disposed on the color filter layer. Each pixel includes at least one thin-film transistor and a pixel electrode. The gate electrode of the thin-film transistor is electrically connected to the corresponding gate line, the source electrode is electrically connected to the corresponding data line, and the drain electrode is electrically connected to the corresponding pixel electrode. The color filter layer may also be disposed in the thin-film transistor array substrate.

[0037] The backlight module includes a light guide plate, a first LED strip, and a second LED strip. The first and second LED strips are disposed on the sides of the light guide plate, specifically on opposite sides of the light guide plate. The first and second LED strips are light-emitting diode (LED) strips. This dual-LED strip technology, compared to the traditional single-LED strip solution which is only disposed on one side of the light guide plate, achieves bidirectional light injection. In the traditional single-LED strip solution, light enters only from one side of the light guide plate. During propagation within the light guide plate, absorption and scattering losses result in a significant brightness attenuation gradient from the light source side to the opposite side, with the brightness difference between the center and edge regions typically exceeding 20%. This dual-LED strip solution, by simultaneously providing light sources on opposite sides of the light guide plate, allows light to converge from both directions towards the center of the light guide plate, effectively compensating for light loss during unidirectional propagation and significantly improving the uniformity of brightness distribution on the light-emitting surface of the backlight module.

[0038] The driver chip is electrically connected to the control chip. The driver chip is configured to generate a first pulse width modulation (PWM) signal PWM1 and a second pulse width modulation (PWM) signal PWM2 based on the control signal from the control chip. The phase difference between the first PWM signal PWM1 and the second PWM signal PWM2 is 180°. Figure 2 As shown, the driver chip generates a first pulse width modulation signal (PWM1) and a second pulse width modulation signal (PWM2) with a phase difference of 180°. These signals control the drive current of the first and second LED strips, respectively, enabling the two LED strips to work alternately. The two strips complement each other in time, ensuring a constant light input to the light guide plate. This phase-interleaved operating mode avoids the light interference effect that may occur when the two LED strips are turned on simultaneously. Furthermore, by modulating the light in the time dimension, it further optimizes the light distribution characteristics in the light guide plate of the backlight module, helping to reduce localized over-brightness or under-brightness.

[0039] A brightness sensor is configured to detect the brightness at multiple locations within the backlight module, generating multiple brightness data points. Multiple brightness sensors are positioned within the backlight module, with each sensor corresponding to a specific backlight zone. For example, a liquid crystal display device may include 16 brightness sensors, each positioned within one of the 16 backlight zones of the backlight module. Each brightness sensor detects the light output brightness of its corresponding backlight zone. Each brightness sensor converts the received light signal into an electrical signal via a photoelectric conversion element, thereby enabling real-time monitoring of the brightness of each backlight zone within the backlight module.

[0040] The control chip is electrically connected to the brightness sensor. The control chip is configured to read multiple brightness data points detected by the brightness sensor at predetermined time intervals and adjust the driving current flowing through the first LED strip and the driving current flowing through the second LED strip based on the multiple brightness data points. The predetermined time is in the range of 1 millisecond to 20 milliseconds. In one embodiment, the predetermined time is 8 milliseconds, corresponding to a reading frequency of 125 Hz. This reading frequency matches the refresh rate of the liquid crystal display panel, which is in the range of 50 Hz to 240 Hz. The control chip reads brightness data from 16 backlight zones sensed by the brightness sensor every 8 milliseconds. This reading cycle is synchronized with the frame cycle of the liquid crystal display panel, avoiding brightness fluctuations caused by a mismatch between the reading frequency and the display refresh rate. The brightness sensor integrates the received light signal within each reading cycle for 80% to 95% of the predetermined time; in one embodiment, the integration time is 7 milliseconds. This integration process effectively filters out instantaneous brightness fluctuations caused by the pulse width modulation signal, obtaining the average brightness value within the reading cycle. The control chip performs filtering on multiple brightness data obtained from multiple consecutive reading cycles. The filtering process further suppresses random fluctuations in the brightness data and improves the stability of brightness detection.

[0041] The control chip is configured to calculate the average edge brightness and center brightness of the backlight module based on multiple brightness data points, and to calculate the ratio of the average edge brightness to the center brightness. The average edge brightness is calculated using data from brightness sensors located in the edge region of the backlight module; the specific formula is: Average Edge Brightness L edge It equals the sum of the values ​​detected by the zeroth brightness sensor (S0), the third brightness sensor (S3), the twelfth brightness sensor (S12), and the fifteenth brightness sensor (S15), then divided by four, i.e., L. edge = (S0+S3+S12+S15) / 4. The center point brightness value is determined by selecting brightness sensor data located in the center area of ​​the backlight module. In a specific embodiment, the center point brightness value L... center The detected value S7 of the seventh brightness sensor, i.e., L center = S7. The control chip calculates the brightness ratio R, which is equal to the center point brightness value L. center Divide by the mean edge brightness L edge That is, R=L center / L edge .

[0042] The control chip is also configured to analyze the independent brightness data of each backlight zone and calculate the variance of the brightness of each zone at the edge. When the variance exceeds a preset threshold, it indicates that the brightness distribution at different locations on the edge is uneven. The control chip then adjusts the driving current of the first and second LED strips according to the specific brightness values ​​of each zone. For example, when the brightness of the edge area (S0, S12) corresponding to the first LED strip is lower than the preset value, while the brightness of the edge area (S3, S15) corresponding to the second LED strip is higher than the preset value, the control chip increases the driving current flowing through the first LED strip and decreases the driving current flowing through the second LED strip through the driving chip, thereby achieving differentiated compensation for different edge areas.

[0043] The driver chip is configured to adjust the drive current flowing through the first LED strip and the drive current flowing through the second LED strip based on a ratio. When the ratio is greater than 1.15, it indicates that the brightness of the central area is too high compared to the edge area. The driver chip increases the drive current flowing through at least one of the first and second LED strips to enhance light compensation in the edge area. When the ratio is less than 0.95, it indicates that the brightness of the edge area is too high compared to the central area. The driver chip decreases the drive current flowing through at least one of the first and second LED strips to reduce the light input intensity in the edge area. When the ratio is within the range of 0.95 to 1.15, it indicates that the brightness distribution is ideal, and the driver chip maintains the current of the drive current flowing through the first and second LED strips at its current value. This adaptive adjustment scheme based on real-time brightness detection can dynamically adjust the current distribution of the two LED strips according to the actual brightness distribution, achieving light compensation for different areas of the light guide plate.

[0044] The control chip is configured to calculate the target drive current according to a specific formula, where I2 equals I1 multiplied by k multiplied by L. target Divide by L edge The 1.8th power, that is, I2 = I1 × k × (L target / L edge )^(1.8); where I1 is the current drive current, I2 is the target drive current, and L target L is the preset brightness value of the image to be displayed on the LCD panel. edgeHere, k represents the average edge brightness of the backlight module, and k is a constant. When the ratio is greater than 1.15, the driver chip adjusts the target drive current to 1.1 to 1.4 times the current drive current; when the ratio is less than 0.95, the driver chip adjusts the target drive current to 0.6 to 0.9 times the current drive current; and when the ratio is between 0.95 and 1.15, the driver chip adjusts the target drive current to 0.9 to 1.1 times the current drive current. In a specific embodiment, when the ratio is greater than 1.15, the driver chip adjusts the target drive current to 1.25 times the current drive current; when the ratio is less than 0.95, the driver chip adjusts the target drive current to 0.8 times the current drive current; and when the ratio is between 0.95 and 1.15, the driver chip adjusts the target drive current to the current drive current. The constant k is a temperature compensation coefficient used to compensate for changes in the photoelectric conversion efficiency of the light strip at different operating temperatures. The value of the constant k ranges from 0.5 to 1.5. The constant k has a value of 1.0 at 20 degrees Celsius. When the operating temperature of the backlight module is higher than 20 degrees Celsius, the value of constant k is greater than 1.0 and less than 1.5. When the operating temperature of the backlight module is lower than 20 degrees Celsius, the value of constant k is less than 1.0 and greater than 0.5. The relationship between constant k and temperature is k = 1.0 + 0.01 × (T - 20), where T is the current operating temperature of the backlight module. The LCD device also includes a temperature sensor, which is installed in the backlight module. The temperature sensor is configured to detect the operating temperature of the backlight module, and the control chip calculates the value of constant k based on the temperature data detected by the temperature sensor.

[0045] like Figure 1 As shown, the liquid crystal display device further includes a first current sensing resistor and a second current sensing resistor. The first current sensing resistor is electrically connected to the first LED strip, and the second current sensing resistor is electrically connected to the second LED strip. In a specific embodiment, the resistance values ​​of both the first and second current sensing resistors are 0.1 ohms. The first and second current sensing resistors are used to sample the driving current flowing through the first and second LED strips, respectively.

[0046] The liquid crystal display device also includes an error amplifier, which is electrically connected to a first current sensing resistor and a second current sensing resistor. The error amplifier is configured to compare the detection result of the first current sensing resistor with a reference voltage, and to compare the detection result of the second current sensing resistor with the reference voltage, and output the comparison result to the driver chip. By comparing the difference between the voltage signal across the current sensing resistor and the reference voltage, the error amplifier generates an error signal and feeds it back to the feedback input pin of the driver chip, thereby achieving constant current control of the LED strip current.

[0047] The driver chip includes a first output pin and a second output pin. The first output pin is used to output a first pulse width modulation signal PWM1, and the second output pin is used to output a second pulse width modulation signal PWM2. The driver chip also includes a feedback input pin, and an error amplifier is electrically connected to the feedback input pin to receive the comparison result of the error amplifier.

[0048] The liquid crystal display device further includes a first switch and a second switch. The control terminal of the first switch is electrically connected to the driver chip and receives a first pulse width modulation signal PWM1. The input terminal of the first switch is electrically connected to the constant current power supply of the liquid crystal display device, and the output terminal of the first switch is electrically connected to a first LED strip. The first switch is configured to adjust the driving current flowing through the first LED strip according to the first pulse width modulation signal PWM1. The control terminal of the second switch is electrically connected to the driver chip and receives a second pulse width modulation signal PWM2. The input terminal of the second switch is electrically connected to the constant current power supply of the liquid crystal display device, and the output terminal of the second switch is electrically connected to a second LED strip. The second switch is configured to adjust the driving current flowing through the second LED strip according to the second pulse width modulation signal PWM2. In a specific embodiment, both the first switch and the second switch are metal-oxide-semiconductor field-effect transistor (MOSFET) switching elements.

[0049] like Figure 2 As shown, the phase of the first pulse width modulation signal PWM1 is 0°, and the phase of the second pulse width modulation signal PWM2 is 180°. The two pulse width modulation signals are complementary in time. The high-level period of the first pulse width modulation signal PWM1 overlaps with the low-level period of the second pulse width modulation signal PWM2, and vice versa. In a specific embodiment, the high-level period of the first pulse width modulation signal PWM1 starts from 0 milliseconds, lasts for 2 milliseconds, and then the low-level period lasts for 2 milliseconds, and so on. The high-level period of the second pulse width modulation signal PWM2 starts from 2 milliseconds, lasts for 2 milliseconds, and then the low-level period lasts for 2 milliseconds, and so on. When the first light strip is in the on state, the second light strip is in the off state; when the first light strip is in the off state, the second light strip is in the on state. The two light strips work alternately to ensure that the light guide plate always has light input.

[0050] A dual-path pulse-width modulation (PWM) signal driving scheme with a 180° phase difference achieves flicker suppression. Because the two LED strips work alternately, with one strip always active, this continuous light output mode effectively reduces light interruptions caused by PWM switching, lowering the perceived flicker. Simultaneously, the alternating operation of the two strips disperses the electromagnetic interference spectrum, avoiding energy concentration at a single frequency and reducing the peak intensity of electromagnetic interference. Furthermore, the dual-strip configuration provides redundancy protection; if one strip fails, the other can continue operating, ensuring the basic display function of the LCD device and significantly improving the reliability of the backlight module.

[0051] like Figure 3 and Figure 4 As shown, this application also provides a backlight driving method for a liquid crystal display device. This method, through a dual-lamp-strip phase-interleaved driving technique, effectively solves the technical problems of poor backlight brightness uniformity, noticeable flicker, low reliability, and high power consumption caused by the single-lamp-strip driving scheme in the prior art. The method includes the following steps: The driver chip generates a first pulse width modulation signal PWM1 and a second pulse width modulation signal PWM2 based on the control signal from the control chip. The phase difference between the first pulse width modulation signal PWM1 and the second pulse width modulation signal PWM2 is 180°.

[0052] The driver chip adjusts the driving current flowing through the first LED strip according to the first pulse width modulation signal PWM1, and adjusts the driving current flowing through the second LED strip according to the second pulse width modulation signal PWM2.

[0053] The dual-strip LED scheme of this application provides light sources simultaneously from opposite sides of the light guide plate, allowing light to converge from two directions towards the center of the light guide plate. This effectively compensates for light loss during unidirectional propagation and significantly improves the uniformity of brightness distribution on the light-emitting surface of the backlight module. The driver chip generates a first pulse width modulation signal PWM1 and a second pulse width modulation signal PWM2 with a phase difference of 180°, which control the driving current of the first and second LED strips respectively. This enables the two LED strips to work alternately, complementing each other in time and ensuring that the light guide plate always has light input. This phase-interleaved working mode avoids the light interference effect that may occur when the two LED strips are turned on simultaneously. At the same time, through light modulation in the time dimension, the distribution characteristics of light in the backlight module are further optimized, helping to reduce local over-brightness or under-brightness.

[0054] Before the driver chip generates the first pulse width modulation signal PWM1 and the second pulse width modulation signal PWM2 according to the control signal from the control chip, the method further includes: The brightness sensor detects the brightness at multiple locations on the backlight module and obtains multiple brightness data.

[0055] The control chip reads multiple brightness data points at predetermined intervals. The predetermined intervals range from 2 microseconds to 20 microseconds.

[0056] The control chip calculates the average edge brightness and center brightness of the backlight module based on multiple brightness data.

[0057] The control chip calculates the ratio of the average edge brightness to the brightness value at the center point.

[0058] The control chip generates control signals based on the ratio to adjust the drive current flowing through the first LED strip and the drive current flowing through the second LED strip. A brightness sensor detects the brightness distribution of the backlight module in real time. The control chip calculates the average edge brightness and the center point brightness value based on the detected brightness data, and then calculates the ratio between the two. This adaptive adjustment scheme based on real-time brightness detection dynamically adjusts the current distribution of the two LED strips according to the actual brightness distribution, achieving light compensation for different areas of the backlight module.

[0059] The method also includes: Read the preset brightness value of the image to be displayed from the memory of the liquid crystal display device.

[0060] The target driving current is calculated using the following formula: I2 = I1 × k × (L target / L edge )^(1.8); where I1 is the current drive current, I2 is the target drive current, and L target L is the preset brightness value of the image to be displayed on the LCD panel. edge Let be the average edge brightness of the backlight module, and k be a constant.

[0061] The driver chip adjusts the drive current flowing through the first LED strip according to the first pulse width modulation signal PWM1, and adjusts the drive current flowing through the second LED strip according to the second pulse width modulation signal PWM2, including: When the ratio is greater than 1.15, it indicates that the brightness of the central area is too high compared to the edge area. The driver chip increases the driving current flowing through at least one of the first and second LED strips to enhance light compensation in the edge area. When the ratio is less than 0.95, it indicates that the brightness of the edge area is too high compared to the central area. The driver chip decreases the driving current flowing through at least one of the first and second LED strips to reduce the light input intensity in the edge area. When the ratio is between 0.95 and 1.15, it indicates that the brightness distribution is ideal, and the driver chip maintains the current driving current flowing through the first and second LED strips at its current value.

[0062] The driver chip adjusts the drive current flowing through the first LED strip according to the first pulse width modulation signal PWM1, and adjusts the drive current flowing through the second LED strip according to the second pulse width modulation signal PWM2, further including: When the ratio is greater than 1.15, the driver chip adjusts the target drive current to 1.1 to 1.4 times the current drive current. When the ratio is less than 0.95, the driver chip adjusts the target drive current to 0.6 to 0.9 times the current drive current. When the ratio is in the range of 0.95 to 1.15, the driver chip adjusts the target drive current to 0.9 to 1.1 times the current drive current.

[0063] The method also includes: The error amplifier samples the drive current flowing through the first lamp bar and the second lamp bar through the first current sensing resistor and the second current sensing resistor, respectively.

[0064] The error amplifier compares the sampled drive current with the reference voltage to obtain the comparison result.

[0065] The error amplifier feeds back the comparison result to the driver chip.

[0066] The driver chip adjusts the drive current flowing through the first LED strip according to the first pulse width modulation signal PWM1, and adjusts the drive current flowing through the second LED strip according to the second pulse width modulation signal PWM2, further including: The driver chip controls the first switch through the first pulse width modulation signal PWM1, so that the first switch adjusts the driving current flowing through the first light strip. The driver chip also controls the second switch through the second pulse width modulation signal PWM2, so that the second switch adjusts the driving current flowing through the second light strip.

[0067] A dual-path pulse-width modulation (PWM) signal driving scheme with a 180° phase difference achieves flicker suppression. Because the two LED strips work alternately, with one strip always active, this continuous light output mode effectively reduces light interruptions caused by PWM switching, lowering the perceived flicker. Simultaneously, the alternating operation of the two strips disperses the electromagnetic interference spectrum, avoiding energy concentration at a single frequency and reducing the peak intensity of electromagnetic interference. Furthermore, the dual-strip configuration provides redundancy protection; if one strip fails, the other can continue operating, ensuring the basic display function of the LCD device and significantly improving the reliability of the backlight module.

[0068] The embodiments of this application have been described in detail above. The content of this specification should not be construed as limiting the scope of protection of this application.

Claims

1. A liquid crystal display device, characterized in that, The liquid crystal display device includes: LCD display panel; A backlight module, the backlight module including a light guide plate, a first light strip and a second light strip, the first light strip and the second light strip being disposed on different sides of the light guide plate; Control chip; A driver chip, electrically connected to the control chip, is configured to generate a first pulse width modulation (PWM) signal and a second PWM signal according to a control signal from the control chip, and to adjust the driving current flowing through the first light strip according to the first PWM signal, and to adjust the driving current flowing through the second light strip according to the second PWM signal, wherein the phase difference between the first PWM signal and the second PWM signal is 180°; and A brightness sensor is configured to detect the brightness at multiple locations of the backlight module to obtain multiple brightness data. The control chip is electrically connected to the brightness sensor. The control chip is configured to read multiple brightness data detected by the brightness sensor at predetermined intervals, and adjust the driving current flowing through the first light strip and the driving current flowing through the second light strip according to the multiple brightness data. The control chip is also configured to calculate the average edge brightness value and the center point brightness value of the backlight module according to the multiple brightness data, and calculate the ratio of the average edge brightness value to the center point brightness value. The driver chip is configured to adjust the driving current flowing through the first light bar and the driving current flowing through the second light bar according to the ratio.

2. The liquid crystal display device according to claim 1, characterized in that, The driver chip is configured to increase the driving current flowing through at least one of the first and second light bars when the ratio is greater than 1.15, decrease the driving current flowing through at least one of the first and second light bars when the ratio is less than 0.95, and maintain the driving current flowing through the first and second light bars at the current value when the ratio is in the range of 0.95 to 1.

15.

3. The liquid crystal display device according to claim 2, characterized in that, The control chip is configured to calculate the target drive current according to the following formula: I2 = I1 × k × (L target / L edge )^(1.8); Where I1 is the current drive current, I2 is the target drive current, and L target L is the preset brightness value of the image to be displayed on the liquid crystal display panel. edge Let k be the average edge brightness of the backlight module, and k is a constant.

4. The liquid crystal display device according to claim 3, characterized in that, When the ratio is greater than 1.15, the driver chip adjusts the target drive current to 1.1 to 1.4 times the current drive current; When the ratio is less than 0.95, the driver chip adjusts the target drive current to 0.6 to 0.9 times the current drive current; When the ratio is in the range of 0.95 to 1.15, the driver chip adjusts the target drive current to 0.9 to 1.1 times the current drive current.

5. The liquid crystal display device according to claim 1, characterized in that, The liquid crystal display device further includes: The first current sensing resistor is electrically connected to the first light strip. A second current-sensing resistor is electrically connected to the second lamp strip; and An error amplifier is electrically connected to the first current sensing resistor and the second current sensing resistor. The error amplifier is configured to compare the detection result of the first current sensing resistor with a reference voltage, and to compare the detection result of the second current sensing resistor with the reference voltage, and output the comparison result to the driver chip.

6. The liquid crystal display device according to claim 1, characterized in that, The liquid crystal display device further includes: A first switch, the control terminal of the first switch being electrically connected to the driver chip and receiving the first pulse width modulation signal, the input terminal of the first switch being electrically connected to the constant current power supply of the liquid crystal display device, and the output terminal of the first switch being electrically connected to the first light strip, the first switch being configured to adjust the driving current flowing through the first light strip according to the first pulse width modulation signal; and The second switch has its control terminal electrically connected to the driver chip and receiving the second pulse width modulation signal, its input terminal electrically connected to the constant current power supply of the liquid crystal display device, and its output terminal electrically connected to the second light strip. The second switch is configured to adjust the driving current flowing through the second light strip according to the second pulse width modulation signal.

7. The liquid crystal display device according to claim 1, characterized in that, Multiple brightness sensors are disposed in the backlight module, and each brightness sensor corresponds to a backlight zone of the backlight module.

8. A backlight driving method for a liquid crystal display device, characterized in that, The method includes: The brightness sensor detects the brightness at multiple locations on the backlight module and obtains multiple brightness data. The control chip calculates the average edge brightness and center point brightness of the backlight module based on multiple brightness data. The control chip calculates the ratio of the average edge brightness to the brightness value of the center point; The control chip generates a control signal based on the ratio to adjust the driving current flowing through the first light bar and the driving current flowing through the second light bar. The driver chip generates a first pulse width modulation signal and a second pulse width modulation signal according to the control signal from the control chip, wherein the phase difference between the first pulse width modulation signal and the second pulse width modulation signal is 180°; and The driver chip adjusts the driving current flowing through the first light strip according to the first pulse width modulation signal, and adjusts the driving current flowing through the second light strip according to the second pulse width modulation signal.

9. The backlight driving method according to claim 8, characterized in that, The driver chip adjusts the driving current flowing through the first light strip according to the first pulse width modulation signal, and adjusts the driving current flowing through the second light strip according to the second pulse width modulation signal, including: When the ratio is greater than 1.15, the driver chip increases the driving current flowing through at least one of the first light strip and the second light strip; When the ratio is less than 0.95, the driver chip reduces the driving current flowing through at least one of the first and second light strips; and When the ratio is in the range of 0.95 to 1.15, the driver chip keeps the driving current flowing through the first and second light bars at its current value.

10. The backlight driving method according to claim 8, characterized in that, The method further includes calculating the target drive current according to the following formula: I2 = I1 × k × (L target / L edge )^(1.8); Where I1 is the current drive current, I2 is the target drive current, and L target L is the preset brightness value of the image to be displayed on the LCD panel. edge Let k be the average edge brightness of the backlight module, and k is a constant.

11. The backlight driving method according to claim 10, characterized in that, The driver chip adjusts the driving current flowing through the first light strip according to the first pulse width modulation signal, and adjusts the driving current flowing through the second light strip according to the second pulse width modulation signal, including: When the ratio is greater than 1.15, the driver chip adjusts the target drive current to 1.1 to 1.4 times the current drive current; When the ratio is less than 0.95, the driver chip adjusts the target drive current to 0.6 to 0.9 times the current drive current; and When the ratio is in the range of 0.95 to 1.15, the driver chip adjusts the target drive current to 0.9 to 1.1 times the current drive current.

12. The backlight driving method according to claim 8, characterized in that, After the brightness sensor detects the brightness at multiple locations of the backlight module and obtains multiple brightness data, and before the control chip calculates the average edge brightness value and the center point brightness value of the backlight module based on the multiple brightness data, the method further includes: The control chip reads multiple brightness data points at predetermined intervals.

13. The backlight driving method according to claim 8, characterized in that, The method further includes: The driving current flowing through the first lamp strip and the second lamp strip is sampled by the first current sensing resistor and the second current sensing resistor, respectively. The sampled drive current is compared with the reference voltage using an error amplifier to obtain the comparison result; and The comparison result is fed back to the driver chip.

14. The backlight driving method according to claim 8, characterized in that, The driver chip adjusts the driving current flowing through the first light strip according to the first pulse width modulation signal, and adjusts the driving current flowing through the second light strip according to the second pulse width modulation signal, including: The driver chip controls the first switch via the first pulse width modulation signal, causing the first switch to adjust the driving current flowing through the first light strip; and The driver chip controls the second switch through the second pulse width modulation signal, so that the second switch adjusts the driving current flowing through the second light strip.

Images