TWI460714B - System and a method of adaptively controlling an led backlight - Google Patents

Description

System and method for adapting and controlling light-emitting diode backlight

The present invention relates to a backlight, and more particularly to a system and method for an adaptive control light-emitting diode (LED) backlight suitable for use in a flat display panel.

The backlight is disposed on the back or side of the flat display panel (eg, the liquid crystal display panel) to provide a light source. The backlight may be a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED) or other light source, wherein the light emitting diode is generally used as a backlight due to its low power consumption, fast response and long service life. .

The first A diagram shows a schematic diagram of a backlight of a light-emitting diode, which is composed of a plurality of strings of LEDs connected in parallel, and each of the LED strings is composed of a plurality of LEDs connected in series. As shown in the first B-picture, the luminous intensity of the light-emitting diode is linearly proportional to the forward current.

Conventional backlights, such as light-emitting diode backlights, typically have a fixed illumination intensity. Since the image data usually does not occupy the entire dynamic range (that is, from the darkest to the brightest), the dynamic display range of the display panel cannot be effectively utilized. In addition, another disadvantage of conventional backlights, such as light-emitting diode backlights, is their low dynamic contrast.

Therefore, it is urgent to propose a novel light-emitting diode backlight, which not only has enhanced contrast, but also has the advantages of a light-emitting diode.

In view of the above, one of the objects of embodiments of the present invention is to provide a system and method for controlling the backlight of a light-emitting diode to greatly enhance the dynamic contrast of the displayed image and/or save considerable energy.

In accordance with an embodiment of the invention, a system adapted to control a backlight of a light emitting diode (LED) includes a content analyzer, a light emitting diode driver, and a light emitting diode current controller. The content analyzer analyzes the brightness of the image data to be displayed on a display panel. The LED driver is used to drive the LED backlight. The illuminating diode current controller controls the illumination of the illuminating diode backlight by the illuminating diode driver according to the analysis result of the content analyzer. When the analysis result of the content analyzer shows that the brightness of the image data is higher than a preset value, the LED current controller over-drives the backlight of the LED to make it flow through the backlight of the LED. The source drive current is greater than a normal current.

10‧‧‧Lighting diode (LED) backlight

11‧‧‧ display panel

12‧‧‧Content Analyzer

13‧‧‧Lighting diode (LED) current controller

14‧‧‧Lighting diode driver

141‧‧‧ Pulse Width Modulation (PWM) Controller

142‧‧‧ Current Limiter

15‧‧‧Data adjustment unit

16‧‧‧ Temperature Estimation Unit

17‧‧‧Overdrive timer

18‧‧‧ Temperature Sensor

21~25‧‧‧dynamic range

61~66‧‧‧Steps

71~74‧‧‧Steps

Figure AA shows a schematic diagram of a backlight of a light-emitting diode.

The first B diagram shows the relationship between the luminous intensity of the light-emitting diode and the forward current.

The second figure shows a system for adapting a control light-emitting diode backlight of the first embodiment of the present invention.

The third to third C diagrams illustrate the relationship between the normal dynamic range of the display panel, the dynamic range of the image content, and the dynamic range of the under-drive/over-drive display panel.

The fourth figure shows a partial system of a controllable light-emitting diode backlight of the second embodiment of the present invention.

The fifth figure shows a system for adapting the control of the backlight of the light-emitting diode according to the third embodiment of the present invention.

FIG. 6A is a flow chart showing a method for adapting the control LED backlight according to the fourth embodiment of the present invention.

Fig. 6B illustrates a time variation diagram of the drive current of Fig. 6A.

FIG. 7A is a flow chart showing a method for adapting the control LED backlight according to the fifth embodiment of the present invention.

Fig. 7B illustrates a time variation diagram of the drive current of Fig. 7A.

The seventh C diagram illustrates the duty cycle of using the sampling clock to obtain the PWM signal.

The second figure shows a system for adaptively controlling a light-emitting diode (LED) backlight 10 in accordance with a first embodiment of the present invention. The system of the present embodiment can be applied to a display panel 11 (e.g., a liquid crystal display panel) that can be illuminated by a backlight of a light emitting diode.

In the present embodiment, the content analyzer 12 analyzes characteristics (for example, brightness) of image data to be displayed on the display panel 11. The light-emitting diode current controller 13 drives the light-emitting diode backlight 10 by the light-emitting diode driver (or driving board) 14 based on the analysis result of the content analyzer 12. The LED driver 14 includes a pulse width modulation (PWM) controller 141 for determining a duty cycle (of the PWM signal) during which the LED of the LED backlight 10 is turned on. The display panel 11 is illuminated. Thereby, the PWM signal with a larger duty cycle allows more current to pass through the light-emitting diode of the light-emitting diode backlight 10, thereby generating a larger brightness (making it brighter). Conversely, a PWM signal with a small duty cycle allows less current to pass through the light emitting diode of the LED backlight 10, thereby producing less brightness (making it darker). The LED driver 14 can also include a current limiter 142 that limits the current entering the LED backlight 10 to an upper limit (eg, using a register to set the upper limit) to avoid illumination. The diode backlight 10 is overheated.

In operation, when the analysis result of the content analyzer 12 indicates that the brightness of the image data is low (that is, the dark image), the light-emitting diode current controller 13 controls the pulse width modulation (PWM) controller 141 to flow in The current of the light-emitting diode of the LED backlight 10 is lower than a normal current (for example, the current recommended by the manufacturer of the light-emitting diode). In other words, the light-emitting diode at this time The body backlight 10 is under-drived or operates in an insufficient drive mode. The third A diagram illustrates the relationship between the normal dynamic range of the display panel 11, the dynamic range of the video content, and the dynamic range of the under-drive display panel 11. As shown in FIG. 3A, the dynamic range 21 of the dark image only accounts for a small portion of the entire dynamic range 22. By insufficiently driving the light-emitting diode backlight 10, the dynamic range 23 of the under-drive display panel 11 is much smaller than the normal display dynamic range 24, thereby saving considerable energy.

According to one of the features of the embodiment, when the analysis result of the content analyzer 12 indicates that the brightness of the image data is high (that is, the bright image), the LED current controller 13 controls the pulse width modulation (PWM) controller. 141, causing the current flowing into the light emitting diode of the light emitting diode backlight 10 to be higher than a normal current (for example, the current recommended by the manufacturer of the light emitting diode). In other words, the light-emitting diode backlight 10 at this time is over-drive or operates in an overdrive mode. The third B diagram illustrates the relationship between the normal dynamic range of the display panel 11, the dynamic range of the video content, and the dynamic range of the over-drive display panel 11. As shown in the third B diagram, the dynamic range 21 of the bright image accounts for almost the entire dynamic range 22. By overdriving the light-emitting diode backlight 10, the dynamic range 25 of the over-drive display panel 11 is made larger than the normal display dynamic range 24, thereby increasing the dynamic contrast of the bright image.

The third C diagram illustrates another overdrive embodiment of the third B diagram. The third C picture uses less overdrive than the third B picture. Thereby, the dynamic range 25 of the over-drive display panel 11 is substantially equal to the normal dynamic range of the display panel 11. Therefore, the number of light-emitting diodes can be reduced to reduce the cost.

The content analyzer 12 and the LED current controller 13 may be disposed in a timing controller (T-con) of the image system, and the embodiment may use hardware, software, or a combination thereof. The content analyzer 12 and the LED current controller 13 can also be provided in a system single chip (SOC) processor, which is typically located before the timing controller (T-con). The system shown in this embodiment may also include data adjustment The whole unit 15 is used to adjust or remap the dynamic range 21 (third A/B/C map) of the image to the entire dynamic range 22 before the image data is fed to the display panel 11.

According to another feature of this embodiment, some mechanisms are disclosed to protect the overdriving LED backlight 10 from overheating. The fourth figure shows a partial system of an adaptive control LED backlight 10 in accordance with a second embodiment of the present invention. In the present embodiment, the temperature estimating unit 16 estimates the temperature of the overdriving LED backlight 10 based on the duty cycle of the pulse width modulation (PWM) signal and the overdrive period recorded by the overdrive timer 17. When the estimated temperature reaches the upper limit of the high temperature, it means that excessive heat is generated, so the overdrive mode is temporarily turned off (that is, the normal current is restored), or the excessive drive current is temporarily lowered.

The fifth figure shows a system for adapting the control of the light-emitting diode backlight 10 of the third embodiment of the present invention. In the present embodiment, temperature sensor 18 is used to detect the temperature of overdriving LED backlight 10. When the detected temperature is higher than the preset temperature threshold, the overdrive current can be temporarily reduced by reducing the duty cycle of the PWM signal.

FIG. 6A is a flow chart showing a method of adapting the control of the LED backlight 10 according to the fourth embodiment of the present invention, and FIG. 6B is a diagram showing a time variation of the driving current. In step 61, the drive current value is accumulated during the period Δt, and then divided by Δt to obtain an average current value I _avg . Since the drive current is generally proportional to the duty cycle of the PWM signal, this step can be performed by processing the PWM signal instead of the drive current. At step 62, the average current value I _{avg is} compared to an upper limit value I _max . If the average current value I _{avg is} not greater than the upper limit value I _max , indicating that the light-emitting diode backlight 10 is not overheated, the flow returns to step 61 for performing drive current accumulation for the next Δt period to obtain another The average current value I _avg , wherein the next Δt period is shifted for a period of time from the previous Δt period. If step 62 determines that the average current value I _{avg is} greater than the upper limit value I _max , then proceeds to step 63 to lower the drive current to avoid overheating of the light-emitting diode backlight 10 . In particular, step 63 is to gradually reduce the drive current so that the viewer does not feel a sudden change in the displayed image. Next, step 64 (similar to step 61) performs accumulation of the drive current to obtain an average current value I _avg during the next Δt. At step 65, the average current value I _{avg is} compared with the upper limit value I _max minus the hysteresis value I _h (ie, I _max -I _h ). If the average current value I _{avg is} not less than the upper limit value I _max minus the hysteresis value I _h (ie, I _max -I _h ), it means that the drive current has not fallen low enough, so steps 63 and 64 are repeated until the average current value I _{avg is} less than the upper limit I _max minus the hysteresis value I _h (i.e., I _avg <I _max -I _h ), and the flow proceeds to step 66 to increase the drive current to enhance the dynamic contrast of the bright image. In particular, step 66 gradually increases the drive current so that the viewer does not experience a sudden change in the displayed image. After completing step 66, the flow returns to the initial step 61.

Since the accumulation of the drive current value requires a buffer or a memory to store the drive current value during Δt, and the average drive current needs to be compared and compared, the fourth embodiment (sixth A/B map) can be implemented. Used in a timing controller (T-con) or system single-chip (SOC) processor to utilize its computational and memory resources. FIG. 7A is a flow chart showing a method of adapting the control of the LED backlight 10 according to the fifth embodiment of the present invention, which does not require a buffer or a memory to store the driving current value. This embodiment can be implemented in a light-emitting diode driver 14, which generally lacks computational and memory resources. Figure 7B illustrates a time variation diagram of the drive current.

In step 71, the first counter (or variable) CNT1 is used to count the first accumulated drive current of the (small) unit period Δt, and in step 72, the second counter (or variable) CNT2 is used to count the double unit period. 2 Δt second cumulative drive current. Wherein, the half of the unit period 2 Δt overlaps the unit period Δt. In step 73, the second accumulated drive current CNT2 is divided by the double unit period 2Δt to obtain an average drive current. Next, at step 74, the difference between CNT2 and CNT1 is obtained as a new (updated) CNT1. The flow returns to step 72 to obtain a new (updated) second accumulated drive current CNT2 of the new double unit period 2Δt. its In the new double unit period 2 Δt before the half overlaps with the old (original) double unit period 2 Δt after the half. In this embodiment, the duty cycle of the PWM signal can be processed to replace the drive current. As shown in the seventh C diagram, the PWM signal can be sampled using a sampling clock having a frequency higher than the PWM signal to obtain a duty cycle of the PWM signal.

The above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention; all other equivalent changes or modifications which are not departing from the spirit of the invention should be included in the following Within the scope of the patent application.

10‧‧‧Lighting diode (LED) backlight

11‧‧‧ display panel

12‧‧‧Content Analyzer

13‧‧‧Lighting diode (LED) current controller

14‧‧‧Lighting diode driver

141‧‧‧ Pulse Width Modulation (PWM) Controller

142‧‧‧ Current Limiter

15‧‧‧Data adjustment unit

Claims (14)

A system for controlling a backlight of a light-emitting diode (LED), comprising: a content analyzer for analyzing brightness of image data to be displayed on a display panel; and a light-emitting diode driver for driving the light a diode backlight, the LED driver includes a pulse width modulation (PWM) controller for determining a duty cycle of a pulse width modulation signal, wherein the pulse width modulation signal is coupled to control flow through a driving current of the LED backlight; and a light emitting diode current controller, according to the analysis result of the content analyzer, controlling the illumination of the LED backlight by the LED driver; Wherein, when the analysis result of the content analyzer indicates that the brightness of the image data is higher than a preset value, the LED current controller over-drives the LED backlight to make it flow through The driving current of the LED backlight is greater than a normal current. The system for adjusting the backlight of the light-emitting diode as described in claim 1 further includes a current limiter for limiting the driving current flowing through the backlight of the light-emitting diode to an upper limit value. The system for controlling the backlight of the light-emitting diode according to the first aspect of the patent application, when the analysis result of the content analyzer indicates that the brightness of the image data is lower than a preset value, the LED current control The backlight is under-drived such that the drive current flowing through the LED backlight is less than the normal current. A system for controlling a backlight of a light-emitting diode (LED), comprising: a content analyzer for analyzing brightness of image data to be displayed on a display panel; and a light-emitting diode driver for driving the light a diode backlight, the LED driver includes a pulse width modulation (PWM) controller for determining a duty cycle of a pulse width modulation signal, wherein the pulse width modulation signal is coupled to control flow through Driving current of the LED backlight; a light-emitting diode current controller, according to the analysis result of the content analyzer, by the light-emitting diode The body driver controls the illumination of the backlight of the light emitting diode; wherein, when the analysis result of the content analyzer indicates that the brightness of the image data is higher than a preset value, the LED current controller is overdriven (over - driving) the backlight of the LED, so that the driving current flowing through the backlight of the LED is greater than a normal current; an over-driving timer for recording the excessive driving time of the backlight of the LED; And a temperature estimating unit, according to the duty cycle of the pulse width modulation signal and the overdrive time of the recording, to estimate the temperature of the overdriving LED backlight; wherein, when the estimated temperature reaches a high temperature upper limit , the drive current is reduced. A system for controlling a backlight of a light-emitting diode (LED), comprising: a content analyzer for analyzing brightness of image data to be displayed on a display panel; and a light-emitting diode driver for driving the light a diode backlight; a light-emitting diode current controller, according to the analysis result of the content analyzer, controlling the illumination of the backlight of the light-emitting diode by the LED driver; wherein, when the content is analyzed The analysis result of the device shows that when the brightness of the image data is higher than a preset value, the LED current controller over-drives the backlight of the LED to pass through the backlight of the LED The driving current of the source is greater than a normal current; and a temperature sensor is configured to detect the temperature of the over-driving LED backlight, wherein when the detecting temperature is higher than a preset temperature threshold, Then the drive current is reduced. A system for controlling a backlight of a light-emitting diode (LED), comprising: a content analyzer for analyzing brightness of image data to be displayed on a display panel; and a light-emitting diode driver for driving the light a diode backlight; a light-emitting diode current controller, according to the analysis result of the content analyzer, controlling the illumination of the backlight of the light-emitting diode by the LED driver; wherein, when the content is analyzed The analysis result of the device shows that when the brightness of the image data is higher than a preset value, The illuminating diode current controller over-drives the illuminating diode backlight such that a driving current flowing through the illuminating diode backlight is greater than a normal current; and a processor for performing the following Step: accumulating a driving current during a period to form an accumulated driving current value; obtaining an average current value according to the accumulated driving current value and the period; and decreasing the average current value when the average current value is greater than an upper limit value Driving current; wherein the step of reducing the driving current is repeated until the average current value is less than the upper limit minus a hysteresis value. A system for controlling a backlight of a light-emitting diode (LED), comprising: a content analyzer for analyzing brightness of image data to be displayed on a display panel; and a light-emitting diode driver for driving the light a diode backlight; a light-emitting diode current controller, according to the analysis result of the content analyzer, controlling the illumination of the backlight of the light-emitting diode by the LED driver; wherein, when the content is analyzed The analysis result of the device shows that when the brightness of the image data is higher than a preset value, the LED current controller over-drives the backlight of the LED to pass through the backlight of the LED The source drive current is greater than a normal current; and a processor for performing the steps of: using a first counter to count to generate a first accumulated drive current for a unit period; using a second counter for counting a second cumulative driving current for generating a double unit period, wherein a first half of the double unit period coincides with the unit period; and the second cumulative driving power is During this unit and twice to obtain an average driving current; obtaining a driving current of the second cumulative difference between the first accumulated drive current, accumulated as a new first drive current; and The counting step of the second counter is repeated to obtain a new second accumulated driving current for a new double unit period, wherein the first half of the new double unit period coincides with the second half of the original double unit period. A method for controlling a backlight of a light-emitting diode (LED), comprising: analyzing brightness of image data to be displayed on a display panel to generate an analysis result; and controlling the backlight of the light-emitting diode according to the analysis result Irradiation to drive the light-emitting diode backlight, wherein a driving current flowing through the light-emitting diode backlight is controlled by a duty cycle of a pulse width modulation signal; wherein, when the analysis result shows the image data When the brightness is higher than a preset value, the light-emitting diode backlight is over-driven, so that the driving current flowing through the light-emitting diode backlight is greater than a normal current. The method for controlling the backlight of the LED as described in claim 8 further includes a current limiting step for limiting a driving current flowing through the backlight of the LED to an upper limit. The method for controlling the backlight of the light-emitting diode according to Item 8 of the patent application, when the analysis result shows that the brightness of the image data is lower than a preset value, the light-emitting two is under-drived. The polar body backlight causes the driving current flowing through the backlight of the light emitting diode to be smaller than the normal current. A method for controlling a backlight of a light-emitting diode (LED), comprising: analyzing brightness of image data to be displayed on a display panel to generate an analysis result; controlling the backlight of the light-emitting diode according to the analysis result Illuminating to drive the LED backlight, wherein a driving current flowing through the LED backlight is controlled by a duty cycle of a pulse width modulation signal, wherein the analysis result displays brightness of the image data Above a predetermined value, the backlight of the LED is over-driven, so that the driving current flowing through the backlight of the LED A greater than a normal current; recording an overdrive time of the LED backlight; and estimating a duty cycle of the overdriving LED according to a duty cycle of the pulse width modulation signal and the recorded overdrive time The temperature; wherein, when the estimated temperature reaches an upper limit of the high temperature, the driving current is decreased. A method for controlling a backlight of a light-emitting diode (LED), comprising: analyzing brightness of image data to be displayed on a display panel to generate an analysis result; controlling the backlight of the light-emitting diode according to the analysis result Illuminating to drive the LED backlight, wherein when the analysis result shows that the brightness of the image data is higher than a preset value, over-drive the LED backlight to make the stream The driving current of the backlight of the LED is greater than a normal current; and a temperature sensing step for detecting the temperature of the over-driving LED backlight, wherein when the detection temperature is higher than one When the temperature threshold is preset, the drive current is reduced. A method for controlling a backlight of a light-emitting diode (LED), comprising: analyzing brightness of image data to be displayed on a display panel to generate an analysis result; controlling the backlight of the light-emitting diode according to the analysis result Illuminating to drive the LED backlight, wherein when the analysis result shows that the brightness of the image data is higher than a preset value, over-drive the LED backlight to make the stream Driving current through the backlight of the LED is greater than a normal current; and using a processor to perform the following steps: accumulating driving current during a period to form an accumulated driving current value; and according to the cumulative driving current value And obtaining an average current value; and when the average current value is greater than an upper limit value, reducing the driving current; wherein the step of reducing the driving current is repeated until the average current value is less than the upper limit value Go to a hysteresis value. A method for controlling a backlight of a light-emitting diode (LED), comprising: analyzing brightness of image data to be displayed on a display panel to generate an analysis result; controlling the backlight of the light-emitting diode according to the analysis result Illuminating to drive the LED backlight, wherein when the analysis result shows that the brightness of the image data is higher than a preset value, over-drive the LED backlight to make the stream Driving current through the LED backlight is greater than a normal current; and using a processor to perform the following steps: using a first counter for counting to generate a first accumulated driving current for a unit period; using one And generating, by the second counter, a second accumulated driving current of a double unit period, wherein a first half of the double unit period coincides with the unit period; and according to the second accumulated driving current and the double unit period, Obtaining an average driving current; obtaining a difference between the second accumulated driving current and the first accumulated driving current as a new first accumulated driving power And repeating the counting step of the second counter to obtain a new second cumulative driving current for a new double unit period, wherein the first half of the new double unit period coincides with the second half of the original double unit period section.