JP4992954B2 - Backlight driving device, backlight driving method, and liquid crystal display device - Google Patents

Description

  The present invention relates to a backlight driving device, a backlight driving method, and a liquid crystal display device that drive and control a backlight light source composed of an LED (Light Emission Diode) element.

  As the backlight of the liquid crystal panel, a CCFL (Cold Cathode Fluorescent Lamp) type using a fluorescent tube is the mainstream, but mercury-less is demanded environmentally. For this reason, in recent years, LEDs have been promising as light sources to replace CCFLs. In particular, the method of obtaining white light by individually combining the primary colors of red LED, green LED, and blue LED and optically combining and additive color mixing is easy to balance the colors, so it is widely used for television applications. Has been considered.

  When an LED is used as a light source for a backlight, the red LED, the green LED, and the blue LED have different luminous efficiencies. Therefore, the current that flows through each color LED must be independent of the other colors. Moreover, since the LED used for each color has a different semiconductor composition, the voltage of the element is different for each color, and the power consumption is also different. Moreover, when using LED as a light source of a backlight, from a viewpoint of realistic cost, it cannot drive each LED separately (for example, refer patent document 1).

  For this reason, when LEDs are used as the light source of the backlight, a system in which a certain number of LEDs are connected in cascade and connected in series is used.

  Specifically, a DC-DC converter power supply and a PWM (Pulse) are connected for each group of LEDs connected in cascade, for example, a group in which a predetermined number of LEDs are connected in cascade for each of red, green, and blue colors. Width Modulation) control unit, the light quantity of each color is detected by red, green and blue photosensors, and based on the result, the amount of current flowing to each group of LEDs is PWM adjusted by feedback control, A method of adjusting chromaticity and brightness by combining red, green, and blue is used.

JP 2001-272938

  However, if the response of such feedback control is fast, the chromaticity changes frequently and is easily recognized by the user. In order to avoid such inconvenience that the chromaticity changes frequently, the feedback control is usually set to a slow response. Therefore, when the power is turned on, adjustment of chromaticity by such feedback control cannot be expected.

  Therefore, in a backlight using such an LED as a light source, for example, an electric power serving as a reference for obtaining predetermined white light is initially set for each color before factory shipment. For example, after roughly setting the duty ratio and the crest value (constant current value flowing through the LEDs of each group) for each color LED, these are adjusted to be a desired light quantity and chromaticity. This is done by storing the duty ratio of each color LED, the photosensor output of each color, and the temperature sensor output in a nonvolatile memory.

  Thus, since the reference duty ratio is set in advance, when the power is turned on, predetermined white light can be obtained by reading the duty ratio from the nonvolatile memory.

  However, LEDs are devices whose brightness deteriorates over time, and even with LEDs of the same color as well as LEDs of different colors, due to variations in manufacturing, the temperature of the LEDs, the ambient temperature of the backlight, etc. The deterioration rate varies.

  Therefore, when the brightness is greatly deteriorated, the power is turned on and the above reference value is read from the nonvolatile memory, and then the duty ratio of the remaining two LEDs is adjusted to obtain a predetermined white light. It takes a long time (convergence time) to be obtained. As a result, for example, a phenomenon occurs in which the screen becomes reddish when the power is turned on and then gradually becomes white. In addition, when the duty ratio of the LED increases due to the deterioration of luminance, a phenomenon occurs in which the power consumption of the backlight increases compared to the initial setting.

  This problem is not limited to luminance deterioration due to aging as described above, but LED characteristics fluctuate due to insufficient annealing, etc., and the difference between the initial duty ratio and the adjusted duty ratio seems to have increased. This is the same in any case.

The present invention has been proposed in view of such a conventional situation, and when a predetermined white light is obtained by adjusting the amount of current flowing through the LED by feedback control, the chromaticity is changed by secular change or the like. It is an object of the present invention to provide a backlight driving device, a backlight driving method, and a liquid crystal display device that can prevent the time required for convergence from becoming long.

In order to achieve the above-described object, the present invention is a series of backlight drive devices that drive and control a display backlight device that generates predetermined white light by mixing light from a plurality of light emitting diodes. Storage means for storing an initial current amount of a current flowing through the plurality of light emitting diodes and a predetermined multiplication coefficient; a light amount detection means for detecting the light amount of light generated by the display backlight device; The current amount obtained by multiplying the current amount by the predetermined multiplication coefficient is set as an initial value, and the current amount of the current flowing through the plurality of light emitting diodes is adjusted by feedback control based on the detection output by the light amount detecting unit, thereby the predetermined amount. Control means for performing control to generate white light, and the control means includes a current amount after feedback control and the initial current amount. If a is greater than a predetermined threshold value, and updates the multiplication coefficient according to the amount of current after the feedback control.

Further, the present invention provides a backlight driving method for driving and controlling a display backlight device that generates predetermined white light by mixing light from a plurality of light emitting diodes. A reading step of reading out the initial current amount of the current to be passed and a predetermined multiplication coefficient from the storage means; a light amount detection step of detecting the amount of light generated by the display backlight device; and Control for generating the predetermined white light by adjusting the amount of current flowing through the plurality of light emitting diodes based on the detection output by the light amount detection means by feedback control, with the current amount multiplied by the multiplication coefficient as an initial value. If the difference between the control step for performing the control and the current amount after feedback control and the initial current amount exceeds a predetermined threshold, Depending on the amount of current after back control and having and an update step for updating the multiplication coefficient.

Furthermore, the present invention is driven by the backlight driving unit, and the display backlight device generating predetermined white light by mixing light from a plurality of light emitting diodes, light generated by the display backlight device Is a liquid crystal display device comprising a transmissive liquid crystal display panel irradiated from the back side, wherein the backlight driving device includes an initial current amount of current flowing through the plurality of light emitting diodes connected in series and a predetermined multiplication coefficient Are stored as storage means, light quantity detection means for detecting the light quantity of light generated by the display backlight device, and an initial current value obtained by multiplying the initial current quantity by the predetermined multiplication coefficient, by adjusting the feedback control of the current amount of the current supplied to the plurality of light emitting diodes based on the detection output of said light quantity detecting means, the upper Control means for performing control to generate predetermined white light, and the control means, when the difference between the current amount after feedback control and the initial current amount exceeds a predetermined threshold, the current after the feedback control The multiplication coefficient is updated according to the amount.

According to the present invention, a current amount obtained by multiplying the initial current amount stored in the storage means by a predetermined multiplication coefficient is set as an initial value, and the current amount of the current flowing through each light-emitting diode is adjusted by feedback control to thereby generate a predetermined white light. In particular, when the difference between the current amount after the feedback control and the initial current amount exceeds a predetermined threshold, the multiplication coefficient is updated according to the current amount after the feedback control. For example, even when the luminance of the light emitting diode is deteriorated due to secular change, it is possible to prevent the time required for convergence of chromaticity from becoming long.

It is a typical perspective view which shows the structure of the color liquid crystal display part of a backlight system in the color liquid crystal display device to which this invention is applied. A unit cell in which two red light-emitting diodes, two green light-emitting diodes and two blue light-emitting diodes are used and a total of six light-emitting diodes are arranged in a row is schematically shown by pattern notation with the number of light-emitting diodes of each color FIG. It is a figure which shows typically the example of a connection of the actual light emitting diode in the light source of the backlight apparatus which comprises the said color liquid crystal display device. It is a block diagram which shows the whole structure of a color liquid crystal display device. It is a figure which shows typically the temperature sensor and light quantity or chromaticity sensor which were provided in the said backlight apparatus. It is a figure which shows the backlight drive control part which drives a light emitting diode. It is a flowchart explaining the process of the microcomputer of the said backlight drive control part.

  Hereinafter, specific embodiments to which the present invention is applied will be described in detail with reference to the drawings.

  The present invention is applied to, for example, a color liquid crystal display device including a backlight type liquid crystal display unit 1 configured as shown in FIG.

  The liquid crystal display unit 1 includes a transmissive color liquid crystal display panel 10 and a backlight device 20 provided on the back side of the color liquid crystal display panel 10.

  The transmissive color liquid crystal display panel 10 has a configuration in which a TFT substrate 11 and a counter electrode substrate 12 are arranged to face each other, and a liquid crystal layer 13 in which, for example, twisted nematic (TN) liquid crystal is sealed is provided in the gap. On the TFT substrate 11, signal lines 14 and scanning lines 15 arranged in a matrix and thin film transistors 16 and pixel electrodes 17 as switching elements arranged at the intersections thereof are formed. The thin film transistor 16 is sequentially selected by the scanning line 15 and writes the video signal supplied from the signal line 14 to the corresponding pixel electrode 17. On the other hand, a counter electrode 18 and a color filter 19 are formed on the inner surface of the counter electrode substrate 12.

  In the color liquid crystal display unit 1, the transmission type color liquid crystal display panel 10 having such a configuration is sandwiched between two polarizing plates and driven by an active matrix system in a state where white light is irradiated from the back side by the backlight device 20. By doing so, a desired full-color video display can be obtained.

  The backlight device 20 includes a light source 21 and a wavelength selection filter 22. The backlight device 20 illuminates the color liquid crystal display panel 10 from the back side with the light emitted from the light source 21 via the wavelength selection filter 22. Such a backlight device 20 is of a direct type in which a transmissive color liquid crystal display panel 10 is disposed on the back side and illuminates from directly below the back side of the color liquid crystal display panel 10.

  Here, the light source 21 of the backlight device 20 is provided with a number of light emitting diodes (LEDs) 3 and outputs light emitted from the light emitting diodes. The light source 21 includes a number of light emitting diodes 3R that emit red (R) light, a number of light emitting diodes 3G that emit green (G) light, and a number of light emitting diodes that emit blue (B) light. 3B is provided. In the light source 21, R, G, B light is mixed to generate white light, and this white light is emitted to the color liquid crystal display panel 10.

  For example, the arrangement of the light emitting diodes 3 in the light source 21 of the backlight device 20 is as follows.

  First, as shown in FIG. 2, two red light emitting diodes 3R, two green light emitting diodes 3G and two blue light emitting diodes 3B are used, and a total of six light emitting diodes are arranged in a unit cell (2G 2R 2B). Subsequently, a middle unit (6G 6R 6B) in which three unit cells (2G 2R 2B) are arranged in the horizontal direction is configured. Then, the middle units (6G 6R 6B) are connected in series in the horizontal direction as shown in FIG. 3, and the light emitting diodes 3 connected in series are arranged in the vertical direction so as to cover the entire screen.

  By arranging the light emitting diode 3 in this way, the light emitting diodes of the three colors R, G, and B are mixed to emit white light with a good balance. As long as the colors are mixed in a balanced manner, the arrangement is not limited to the arrangement shown in FIGS. Not only the light emitting diodes of three colors of R, G, and B, but also white light of a predetermined chromaticity can be obtained by using light emitting diodes of more colors.

  Next, an example of the overall configuration of the color liquid crystal display device 30 is shown in FIG.

  The color liquid crystal display device 30 includes a power supply unit 31 that supplies driving power to the color liquid crystal display panel 10 and the backlight device 20, an X driver circuit 32 and a Y driver circuit 33 that drive the color liquid crystal display panel 10, and an external device. An RGB process processing unit 35 to which a video signal is supplied via the input terminal 34, a video memory 36 and a control unit 37 connected to the RGB process processing unit 35, and a backlight drive control for controlling the backlight device 20 Part 38.

  The video signal input via the input terminal 34 is subjected to signal processing such as chroma processing by the RGB process processing unit 35, and further converted from a composite signal to an RGB separate signal suitable for driving the color liquid crystal display panel 10. Are supplied to the control unit 37 and are also supplied to the X driver 32 via the video memory 36. Further, the control unit 37 controls the X driver 32 and the Y driver circuit 33 at a predetermined timing according to the RGB separate signal, and performs color processing using the RGB separate signal supplied to the X driver 32 via the video memory 36. By driving the liquid crystal display panel 10, an image corresponding to the RGB separate signal is displayed.

  4 and 5, the color liquid crystal display device 30 includes a temperature sensor 41 for detecting the temperature of the light source 21 (light emitting diode) of the backlight device 20 and a light source 21 (light emission) of the backlight device 20. A light amount or chromaticity sensor 42 (42R, 42G, 42B) for detecting the light amount or chromaticity of each color of R, G, B of the diode).

  The detection value of the temperature sensor 41 and the detection value of the light quantity or chromaticity sensor 42 are supplied to the backlight drive control unit 38. The backlight drive control unit 38 controls the drive current of the light emitting diodes constituting the light source 21 based on the detection values of these sensors.

  Next, the backlight drive control unit 38 that drives the light emitting diodes 3 connected in series in the horizontal direction will be described. FIG. 6 shows a circuit configuration example of the backlight drive control unit 38.

  The backlight drive control unit 38 includes a DC-DC converter 51, a constant resistance (Rc) 52, an FET 53, a PWM control circuit 54, a capacitor 55, a sample hold FET 56, a resistor 57, and a hold timing circuit 58. And a microcomputer 59 as a control unit.

  The DC-DC converter 51 receives the DC voltage VIN generated from the power supply 31 shown in FIG. 4, and generates a DC output voltage Vcc that is stabilized by switching the input DC power. The DC-DC converter 51 generates an output voltage Vcc that is stabilized so that the potential difference between the voltage input from the feedback terminal Vf and the output voltage Vcc becomes a constant value (Vref).

  The anode side of the light emitting diodes 3 connected in series is connected to the output terminal of the output voltage Vcc of the DC-DC converter 51 via a constant resistance (Rc) 52. The anode side of the light emitting diodes 3 connected in series is connected to the feedback terminal of the DC-DC converter 51 through the source-drain of the sample hold FET 56. In addition, the cathode side of the light emitting diodes 3 connected in series is connected to the ground via the source and drain of the FET 53.

  The PWM signal generated from the PWM control circuit 54 is input to the gate of the FET 53. The FET 53 is turned on between the source and the drain when the PWM signal is turned on, and turned off between the source and the drain when the PWM signal is turned off. Therefore, the FET 53 causes a current to flow through the light emitting diode 3 when the PWM signal is on, and sets a current flowing through the light emitting diode 3 to 0 when the PWM signal is off. That is, the FET 53 causes the light emitting diode 3 to emit light when the PWM signal is on, and stops the light emission of the light emitting diode 3 when the PWM signal is off.

  The PWM control circuit 54 generates a PWM signal that is a binary signal in which the duty ratio of the on time and the off time is adjusted. When the power of the color liquid crystal display device 30 is turned on, the PWM control circuit 54 receives an initial duty ratio corresponding to each color from the microcomputer 59, and the pulse width of the PWM signal so as to coincide with this duty ratio. Adjust. Further, when the target duty ratio set according to the actual light quantity or chromaticity of each color of R, G, B is input from the microcomputer 59, the PWM control circuit 54 matches the target duty ratio. Adjust the pulse width of the PWM signal. That is, the PWM control circuit 54 widens the ON pulse width when the current duty ratio is smaller than the target duty ratio, and lengthens the light emission time of the light emitting diode 3, and when larger than the target duty ratio, the pulse width. The PWM signal is controlled so that the light emission time of the light emitting diode 3 is shortened by narrowing.

  The capacitor 55 is provided between the output end of the DC-DC converter 51 and the feedback end. The resistor 57 is connected to the output terminal of the DC-DC converter 51 and the gate of the sample and hold FET 56.

  The hold timing circuit 58 receives a PWM signal, and generates a hold signal that is turned off for a predetermined time at the rising edge of the PWM signal and turned on at other times.

  The hold signal output from the hold timing circuit 58 is input to the gate of the sample hold FET 56. The sample and hold FET 56 is turned on between the source and drain when the hold signal is off, and turned off between the source and drain when the hold signal is on.

  That is, in the backlight drive control unit 38, the current ILED is allowed to flow through the light emitting diode 3 only when the PWM signal generated from the PWM control circuit 54 is turned on. The capacitor 55, the sample and hold FET 56, and the resistor 57 constitute a sample and hold circuit. This sample-and-hold circuit samples the voltage value of the anode of the light emitting diode 3 (that is, one end of the constant resistance (Rc) 52 to which the output voltage Vcc is not connected) when the PWM signal is turned on, and the DC-DC converter 51 is fed to the feedback end. Since the DC-DC converter 51 stabilizes the output voltage Vcc based on the voltage value input to the Ford back end, the peak value of the current ILED flowing through the constant resistance (Rc) 52 and the light emitting diode 3 is constant. Therefore, the backlight drive control unit 38 is pulse-driven according to the PWM signal in a state where the peak value of the current ILED flowing through the light emitting diode 3 is constant.

  When the power of the color liquid crystal display device 30 is turned on, the microcomputer 59 reads the duty ratio at the time of initial setting of each color from the nonvolatile memory 60 and supplies it to the PWM control circuit 54. Here, the initial setting is performed by, for example, roughly setting the duty ratio and the peak value of the current ILED for the light-emitting diodes 3 of each color, and then adjusting them so that the desired light quantity and chromaticity are obtained. The duty ratio of the light emitting diodes 3 of each color, the light quantity and chromaticity of each color, and the output of the temperature sensor 41 are stored in advance in the nonvolatile memory 60 before shipment from the factory.

  Further, the microcomputer 59 fixes the duty ratio of one of the light emitting diodes 3 in order to obtain predetermined white light, performs feedback control for the remaining two light emitting diodes 3, and performs a light quantity or chromaticity sensor 42. The target duty ratio is set until the ratio of the light quantity or chromaticity of each color detected in step 1 matches the ratio at the time of initial setting (that is, until the chromaticity of white light mixed with R, G, B light converges). This is supplied to the PWM control circuit 54.

  As described above, the backlight drive control unit 38 including the microcomputer 59 first generates a PWM signal with the duty ratio at the time of initial setting, and then the light amount or color of each color detected by the light amount or chromaticity sensor 42. With reference to the degree, the duty ratio is adjusted by feedback control so that predetermined white light is obtained.

  By the way, the light emitting diode is a device whose luminance deteriorates with time, and, of course, in the light emitting diodes of different colors due to variations in manufacturing, the temperature of the light emitting diode, the ambient temperature in which the backlight device 20 is arranged, Even with light emitting diodes of the same color, the degradation rate varies.

  Therefore, when the brightness is greatly deteriorated and the difference between the duty ratio at the initial setting read from the nonvolatile memory 60 and the adjusted duty ratio becomes large, the duty ratio at the initial setting from the nonvolatile memory 60 is increased. The time (convergence time) required until the predetermined white light is obtained by adjusting the duty ratios of the light emitting diodes 3 of the remaining two colors after reading out the light becomes longer. As a result, for example, a phenomenon occurs in which the screen becomes reddish when the power is turned on and then gradually becomes white. Further, when the duty ratio of the light emitting diode 3 is increased due to the deterioration of the luminance, a phenomenon occurs in which the total power of the backlight is increased as compared with the initial setting.

  This problem is not limited to luminance degradation due to aging degradation as described above, but characteristic variations of the light emitting diode 3 occur due to insufficient annealing or the like, and the difference between the duty ratio at the initial setting and the adjusted duty ratio seems to have increased. This is the same in any case.

  Therefore, the microcomputer 59 actually reads a predetermined multiplication coefficient set for each color together with the duty ratio at the initial setting from the nonvolatile memory 60, and multiplies the read multiplication coefficient by the read multiplication coefficient. By correcting and using the corrected duty ratio, the time required for the chromaticity to converge is shortened.

  Specifically, an example of duty ratio correction processing will be described with reference to the flowchart of FIG. When the duty ratio is adjusted so that predetermined white light is obtained, the duty ratio of the light emitting diode 3 of any one color is fixed, and the duty ratio is adjusted for the remaining two colors of the light emitting diodes 3. In this specific example, the duty ratio of the blue light-emitting diode 3B is fixed because the blue light-emitting diode 3B has the smallest change in luminance and peak wavelength due to temperature change.

First, when the power of the color liquid crystal display device 30 is turned on, the microcomputer 59 sets the duty ratios PWM _R0 , PWM _G0 , PWM _B0 for each color at the time of initial setting, and a predetermined multiplication coefficient Kr set for each color. , Kg, Kb are read from the non-volatile memory 60, the duty ratios PWM _R0 , PWM _G0 , PWM _B0 are multiplied by multiplication coefficients Kr, Kg, Kb, respectively, and the multiplication results are supplied to the PWM control circuit 54 (step S1). . Here, the initial values of the multiplication coefficients Kr, Kg, and Kb are 1, and initially, the duty ratios PWM _R0 , PWM _G0 , and PWM _B0 at the initial setting are supplied to the PWM control circuit 54 as they are. The PWM control circuit 54 adjusts the pulse width of the PWM signal so as to match the supplied duty ratio.

Next, in order to obtain predetermined white light, the microcomputer 59 fixes the duty ratio PWM _B0 of the blue light-emitting diode 3B, performs feedback control on the red and green light-emitting diodes 3R and 3G, and performs light quantity or chromaticity. The duty ratio is changed and supplied to the PWM control circuit 54 until the ratio of the light quantity or chromaticity of each color detected by the sensor 42 matches the ratio at the time of initial setting (step S2). As a result, when predetermined white light is obtained, it is assumed that the duty ratio of each color becomes PWM _Rx , PWM _Gx , PWM _B0 .

If the light emitting diode 3 is repeatedly lit for a long time while performing such adjustment processing, the luminance of the light emitting diode 3 deteriorates. It is assumed that the duty ratio is changed by the microcomputer 59 so as to correct this luminance deterioration, and as a result, the adjusted duty ratios of the respective colors are PWM _Ry , PWM _Gy , and PWM _B0 .

The microcomputer 59 determines the absolute value of the difference between the duty ratios PWM _Ry and PWM _Gy of the red and green light emitting diodes 3R and 3G and the initial duty ratios PWM _R0 and PWM _G0 and predetermined threshold values limitR and limitG. In comparison, as a result of the deterioration of the luminance of the light emitting diode 3, the absolute value of the difference between the duty ratios PWM _Ry and PWM _{Gy of} the red and green light emitting diodes 3R and 3G and the initial duty ratios PWM _R0 and PWM _G0 is If it is larger than the predetermined thresholds limitR and limitG (step S3), the microcomputer 59 updates the values of the multiplication coefficients Kr, Kg and Kb (step S4).

As an update method, for example, Kb = 1 is fixed, and Kr and Kg are updated according to the ratio between the duty ratios PWM _R0 and PWM _G0 at the initial setting and the adjusted duty ratios PWM _Ry and PWM _Gy. Can be mentioned.

However, in this case, since the duty ratio of the light emitting diode 3 becomes large and the power consumption of the backlight may become larger than that at the time of initial setting, the increase in power consumption is, for example, within 5%. , Kr, Kg, Kb may all be updated. Note that the power consumption Power of the backlight is expressed by the following equation when the total voltage of the light emitting diodes 3R, 3G, and 3B is Vr, Vg, and Vb and the current values are Ir, Ig, and Ib, respectively:
Power = Vr * PWM _R * Ir + Vg * PWM _G * Ig + Vb * PWM _B * Ib
An approximate estimate can be obtained.

Further, after _obtaining the multiplication factors Kr, Kg, Kb according to the ratios of the duty ratios PWM _R0 , PWM _G0 , PWM _B0 at the initial setting and the duty ratios PWM _Rx , PWM _Gx , PWM _B0 of each color after adjustment, Correction may be made so that the maximum value is 1, and new multiplication coefficients Kr, Kg, Kb may be obtained.

  The backlight drive control unit 38 updates the values of the multiplication coefficients Kr, Kg, and Kb as described above. As a result, when the power of the color liquid crystal display device 30 is turned on next time, the final duty ratio after the adjustment is obtained. Since the approximate duty ratio is supplied to the PWM control circuit 54 from the beginning, the time required until the chromaticity converges can be shortened.

  It should be noted that the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention.

  For example, in the embodiment described above, the initial setting value and the multiplication coefficient of each color are described as being stored in the nonvolatile memory 60. However, the present invention is not limited to this, and the setting value of each color after adjustment is stored in the nonvolatile memory as it is. May be stored in the memory 60. Further, the setting value of a specific color and the ratio information of other colors with respect to the setting value may be stored in the nonvolatile memory 60. In other words, any data may be stored in the non-volatile memory 60 as long as the data of each color applied to shorten the time required for the chromaticity to converge when the power is turned on can be reproduced.

  DESCRIPTION OF SYMBOLS 1 Color liquid crystal display part, 3 Light emitting diode, 10 Color liquid crystal display panel, 20 Backlight apparatus, 30 Color liquid crystal display apparatus, 38 Backlight drive control part, 41 Temperature sensor, 42 Light quantity or chromaticity sensor, 51 DC-DC converter , 52 Constant resistance (Rc), 53 FET, 54 PWM control circuit, 55 capacitor, 56 Sample hold FET, 57 Resistance, 58 Hold timing circuit, 59 Microcomputer, 60 Non-volatile memory

Claims (3)

In a backlight driving device that drives and controls a display backlight device that generates predetermined white light by mixing light from a plurality of light emitting diodes,
Storage means for storing an initial current amount of a current flowing through the plurality of light emitting diodes connected in series and a predetermined multiplication coefficient;
A light amount detecting means for detecting a light amount of light generated by the display backlight device;
The current amount obtained by multiplying the initial current amount by the predetermined multiplication coefficient is set as an initial value, and the current amount of the current flowing through the plurality of light emitting diodes is adjusted by feedback control based on the detection output by the light amount detection unit, thereby Control means for performing control to generate predetermined white light,
The control means updates the multiplication coefficient according to the current amount after the feedback control when the difference between the current amount after the feedback control and the initial current amount exceeds a predetermined threshold value. Light drive device. In a backlight driving method for driving and controlling a display backlight device that generates predetermined white light by mixing light from a plurality of light emitting diodes,
A reading step of reading out an initial current amount of a current flowing through the plurality of light emitting diodes connected in series and a predetermined multiplication coefficient from a storage unit;
A light amount detecting step for detecting the amount of light generated by the display backlight device;
The current amount obtained by multiplying the initial current amount by the predetermined multiplication coefficient is set as an initial value, and the current amount of the current flowing through the plurality of light emitting diodes is adjusted by feedback control based on the detection output in the light amount detection step. A control process for performing control to generate light of a predetermined white light;
An update step of updating the multiplication coefficient according to the current amount after the feedback control when the difference between the current amount after the feedback control and the initial current amount exceeds a predetermined threshold value. Light drive method. Is driven by the backlight driving unit, and the display backlight device generating predetermined white light by mixing light from a plurality of light emitting diodes, light generated by the display backlight device is illuminated from the back side A transmissive liquid crystal display panel comprising:
The backlight driving device includes a storage unit that stores an initial current amount of a current flowing through the plurality of light emitting diodes connected in series and a predetermined multiplication coefficient, and a light amount of light generated by the display backlight device. A light amount detecting means for detecting the current amount, and a current amount obtained by multiplying the initial current amount by the predetermined multiplication coefficient as an initial value, and feeding back the current amounts of the currents to be supplied to the plurality of light emitting diodes based on the detection output by the light amount detecting means. Control means for performing control to generate the predetermined white light by adjusting by control, and the control means has a difference between a current amount after feedback control and the initial current amount exceeds a predetermined threshold value. In this case, the multiplication coefficient is updated according to the amount of current after the feedback control.

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