KR101255267B1 - Method and apparatus of driving lamp - Google Patents

Abstract

The present invention provides a lamp driving method and apparatus that can randomly change the position where the wavy noise is generated by randomly converting and supplying a pulse width of a pulse width modulation (PWM) signal according to an AC control signal from the outside. The method according to claim 1, further comprising: generating a variable voltage according to a first alternating current control signal from which an external frequency is converted, generating a triangular wave whose pulse width is changed according to the variable voltage, and generating the triangular wave according to a reference voltage from the outside. Converting the signal to a PWM signal, and driving the lamp using the PWM signal.

Pulse Width Modulation (PWM) Signal, Pulse Width Modulation, Voltage Regulator

Description

Lamp driving method and apparatus {Method and apparatus of driving lamp}

1 is a block diagram showing a liquid crystal display device according to an embodiment of the present invention.

2 is a block diagram showing a PWM signal generator according to a first embodiment of the present invention.

3 is a block diagram showing the inverter control IC shown in FIG.

4A to 4D are waveform diagrams of signals input / output to the PWM signal generator shown in FIG. 2;

5 is a block diagram showing a PWM signal generator according to a second embodiment of the present invention.

6A to 6D are waveform diagrams of signals input / output to the PWM signal generator shown in FIG. 5.

＊ Description of symbols for main parts of the drawings ＊

2: liquid crystal panel 4: data driver

6: gate driver 8: timing controller

10: backlight unit 12: inverter

14: PWM signal generator 141: inverter control IC

142: triangle wave generator 143: comparator

162: voltage adjusting unit Vref: reference voltage

ACS1: first AC control signal VR1, VR2: variable voltage

The present invention converts the pulse width of a PWM (Pulse Width Modulation) signal according to an AC control signal in which a frequency from an external source is randomly changed and supplies a lamp capable of randomly changing a position where a wavy noise is generated. It relates to a driving method and an apparatus.

Conventional liquid crystal displays display images by adjusting the light transmittance of liquid crystals having dielectric anisotropy using an electric field. To this end, the liquid crystal display includes a liquid crystal panel in which pixel regions are arranged in a matrix, and a driving circuit for driving the liquid crystal panel.

In the liquid crystal panel, a plurality of gate lines and a plurality of data lines are arranged to cross each other, and a pixel region is positioned in an area defined by vertical crossings of the gate lines and the data lines. Pixel electrodes and a common electrode for applying an electric field to each of the pixel regions are formed. Each of the pixel electrodes is connected to a thin film transistor (TFT) which is a switching element. The TFT is turned on by the scan pulse of the gate line, so that the data signal of the data line is charged to the pixel electrode.

The driving circuit includes a gate driver for driving the gate lines, a data driver for driving the data lines, a timing controller for supplying control signals for controlling the gate driver and the data driver, and a backlight for irradiating light to the liquid crystal panel. Unit and an inverter for driving the backlight unit.

The backlight unit includes a lamp as a light source for generating light. The lamp generates light by being driven by an AC drive signal from the inverter.

The inverter supplies an AC drive signal for driving the lamp to the backlight unit. Since the lamp driven in continuous mode consumes a lot of current, the inverter reduces the current consumption by driving in burst mode, which turns the lamp on and off at regular intervals. In this case, the inverter causes the AC driving signal for driving the lamp to be supplied or cut off in response to the PWM signal from the outside.

However, when the PWM signal supplied from the outside becomes an integer multiple (at least two times) of the AC drive signal, the wavy noise generated by the interference between frequencies appears to be fixed horizontally on the display device. In addition, when the PWM signal does not become an integer multiple of the AC driving signal, there is a problem that the web noise appearing horizontally on the display device is constantly detected in the vertical direction while being detected by the naked eye.

The present invention is to solve the problems described above, by randomly converting the pulse width of the PWM signal for driving the inverter according to the AC control signal is a random pulse width is changed randomly the position where the web noise is generated It is an object of the present invention to provide a lamp driving method and apparatus.

The lamp driving method according to the present invention for achieving the above object is to generate a variable voltage according to the first AC control signal is converted frequency from the outside, generating a triangular wave whose pulse width is changed in accordance with the variable voltage And converting the triangular wave into a PWM signal according to an external reference voltage, and driving a lamp using the PWM signal.

In addition, the driving method of the liquid crystal display according to the present invention for achieving the above object is to generate a variable voltage in accordance with the first AC control signal is converted frequency from the outside, the pulse width according to the variable voltage Generating a varying triangular wave, converting the triangular wave into a PWM signal according to a reference voltage from the outside, and driving a lamp using the PWM signal.

Lamp driving apparatus according to the present invention for achieving the above object is a PWM signal generator for generating a PWM signal whose pulse width is changed in accordance with the first AC control signal from the outside, and the lamp in response to the PWM signal It characterized in that it comprises an inverter for driving.

In addition, the driving device of the liquid crystal display according to the present invention for achieving the above object is a liquid crystal panel for displaying an image, a lamp for irradiating light to the liquid crystal panel, and according to the first AC control signal from the outside And a PWM signal generator for generating a PWM signal whose pulse width is changed, and an inverter for driving the lamp in response to the PWM signal.

Hereinafter, a driving apparatus and a driving method thereof of a liquid crystal display according to an exemplary embodiment of the present invention having the above characteristics will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

The liquid crystal display shown in FIG. 1 includes a liquid crystal panel 2 having a pixel region, a data driver 4 driving a plurality of data lines DL1 to DLm, and a plurality of gate lines GL1 to GLn. A gate driver 6 for driving the driver, a timing controller 8 for controlling the data driver 4 and the gate driver 6, a backlight unit 10 for irradiating light to the liquid crystal panel 2, and a back An inverter 12 for driving the light unit 10 and a PWM signal generator 14 for generating a PWM signal whose pulse width is randomly converted to drive the inverter 12 are included.

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel area defined by a plurality of gate lines GL1 to GLn and a plurality of data lines DL1 to DLm, and a liquid crystal connected to a TFT. Capacitor Clc is provided. The liquid crystal capacitor Clc is composed of a pixel electrode connected to a TFT and a common electrode facing each other with the pixel electrode and the liquid crystal interposed therebetween. The TFT supplies the data signals from the respective data lines DL1 to DLm to the pixel electrodes in response to the scan pulses from the respective gate lines GL1 to GLn. The liquid crystal capacitor Clc charges the difference voltage between the data signal supplied to the pixel electrode and the common voltage supplied to the common electrode, and adjusts the light transmittance by varying the arrangement of liquid crystal molecules according to the difference voltage. The storage capacitor Cst is connected in parallel to the liquid crystal capacitor Clc to maintain the voltage charged in the liquid crystal capacitor Clc until the next data signal is supplied. The storage capacitor Cst is formed by overlapping the pixel electrode with the previous gate line and the insulating layer interposed therebetween. In contrast, the storage capacitor Cst may be formed by overlapping the pixel electrode with the storage line and the insulating layer interposed therebetween.

The data driver 4 converts the digital image data Data into analog image data according to the data control signal DCS from the timing controller 8, and one horizontal period in which scan pulses are supplied to the gate lines GL1 to GLn. Each horizontal analog video data for one horizontal line is supplied to the data lines DL1 to DLm. That is, the data driver 4 selects a gamma voltage having a predetermined level according to the gray value of the analog image data and supplies the selected gamma voltage to the data lines DL1 to DLm.

The gate driver 6 includes a shift register that sequentially generates scan pulses, that is, gate high pulses, in response to the gate control signal GCS from the timing controller 8.

The timing controller 8 arranges the image data RGB from the outside to be suitable for driving the liquid crystal panel 2 and supplies the image data RGB to the data driver 4. In addition, the data driver 4 and the gate driver 6 are controlled by generating the data control signal DCS and the gate control signal GCS using the external synchronization signals DCLK, DE, Hsync, and Vsync. .

The backlight unit 10 includes a light source for generating light and an optical unit for diffusing and condensing incident light from the light source to improve light efficiency. The light source mainly uses a cylindrical lamp such as Cold Cathode Fluorescent Lamp (CCFL) and External Electrode Fluorescent Lamp (EEFL). The lamp is driven by the AC drive signal ACcs from the inverter 12 to generate light.

The inverter 12 generates and supplies an AC driving signal ACcs for driving a lamp. At this time, the inverter 12 is a burst mode (Burst Mode) to turn on / off the lamp by supplying or interrupting the AC drive signal (ACcs) in response to a pulse width modulation (PWM) signal with a randomly changed pulse width Drive).

The PWM signal generation unit 14 generates and supplies a PWM signal whose pulse width is randomly converted according to the AC control signal ACS and the reference voltage Vref which are randomly converted within a predetermined frequency range, and supplies the same to the inverter 12. .

2 is a block diagram illustrating a PWM signal generator according to a first embodiment of the present invention, and FIGS. 4A to 4D are waveform diagrams of signals input / output to the PWM signal generator shown in FIG. 2.

2 and 4A to 4D, the PWM signal generator 14 generates a PWM signal having a random pulse width in response to signals such as an input voltage Vin and a reference voltage Vref from the outside. An inverter control IC 141, a first switching element Tr1 switched to a turn-on or turn-off state according to an AC control signal ACS having a random pulse width from the outside, and a first switching The first resistor R1 has a voltage VR1 that varies according to the switching state of the device Tr1. Here, the variable voltage VR1 is a value at which the voltage level is converted according to the resistance values of the first switching element Tr1 and the first resistor R1. That is, although the resistance value of the first resistor R1 is always fixed, the resistance value of the first switching element Tr1 varies depending on the turn-on or turn-off state. Accordingly, the sum of the resistance values of the first switching element Tr1 and the first resistor R1 is changed according to the turn-on or turn-off state of the first switching element Tr1. The voltage applied to the first switching element Tr1 and the first resistor R1 is changed according to the changed resistance value. Here, the first switching element Tr1 has a constant gain as the analog signal is supplied.

The inverter control IC 141 converts the input voltage Vin into a triangular wave CW in accordance with the variable voltage VR1 from the first switching element Tr1 and the first resistor R1. The inverter control IC 141 includes a pulse generator (not shown) to generate a PWM signal according to the input voltage Vin and the reference voltage Vref. In this case, the first switching element Tr1 and the first resistor ( The pulse width is converted according to the variable voltage VR1 of the terminal to which R1) is connected. Then, by converting the voltage level of the triangular wave CW in accordance with the reference voltage Vref, a PWM signal whose pulse width is converted at the reference voltage Vref level is generated and supplied to the inverter 12.

The first switching element Tr1 is turned on or off in accordance with an AC control signal ACS which is converted to a random frequency from the outside. Here, when driving the 32-inch display device, the AC control signal ACS is input as a sine wave in which the frequency is randomly converted to about 180 Hz to 210 Hz as shown in FIG. 4A.

The resistance value Ohm of the first switching element Tr1 and the first resistor R1 is variable as shown in FIG. 4B according to the switching state of the first switching element Tr1, that is, the amplitude change of the AC control signal ACS. do.

Specifically, the resistance value Ohm of the first switching element Tr1 and the first resistor R1 is determined by the AC control signal ACS according to the turn-on or turn-off state of the first switching element Tr1. Change in inverse proportion to amplitude. Therefore, the variable voltage VR1 of the first resistor R1 varies in inverse proportion to the resistance value Ohm of the first switching element Tr1 and the first resistor R1.

The variable voltage VR1 may be represented by an AC waveform according to a gain value of the first switching element Tr1 since the AC control signal ACS input is an AC waveform. Therefore, the variable voltage VR1 has a waveform in which the variable voltage VR1 is synchronized with the AC control signal ACS in inverse proportion to the resistance value Ohm of the first switching element Tr1 and the first resistor R1.

Thereafter, the pulse width of the triangle wave CW generated by the inverter control IC 141 is randomly converted as shown in FIG. 4C according to the variable voltage VR1. Here, in the triangle wave CW shown in FIG. 4C, when the resistance value Ohm shown in FIG. 4B is low, that is, when the voltage VR1 of the first resistor R1 is high, the width of the triangle wave CW is narrow. When the voltage VR1 of R1 is low, its width is wide.

3 is a configuration diagram illustrating the inverter control IC shown in FIG. 2.

The inverter control IC 141 shown in FIG. 3 is a triangular wave generator for converting an input voltage Vin into a triangular wave CW according to the variable voltage VR from the first switching element Tr1 and the first resistor R1. 142 and a comparator 143 for converting the triangle wave CW input from the triangle wave generator 142 according to the reference voltage Vref to generate a PWM signal.

The triangular wave generator 142 converts the input voltage Vin from the outside into a triangular wave CW whose pulse width is converted as shown in FIG. 4C according to the variable voltage VR1 from the first switching element Tr1 and the first resistor R1. Will occur). Specifically, the voltage VR1 of the first switching element Tr1 and the first resistor R1 is varied according to the AC control signal ACS supplied with a random frequency as shown in FIG. 4A. Therefore, the pulse width of the triangle wave CW generated from the triangle wave generator 142 is also converted corresponding to the AC control signal ACS.

The comparator 143 generates a PWM signal by converting the triangular wave CW from the triangular wave generator 142 according to the reference voltage Vref as shown in FIGS. 4C and 4D, and supplies the PWM signal to the inverter 12. do. Here, the PWM signal is output with a pulse width randomly converted corresponding to the pulse width of the triangle wave CW.

Thereafter, the inverter 12 generates an AC driving signal ACcs in response to the PWM signal in which the pulse width is randomly converted and supplies it to the backlight 10. As a result, the web noise generated in the liquid crystal panel 2 randomly moves in the up / down direction and cannot be detected by the naked eye.

5 is a block diagram illustrating a PWM signal generator according to a second exemplary embodiment of the present invention, and FIGS. 6A to 6D are waveform diagrams of signals input / output to the PWM signal generator illustrated in FIG. 5.

5 and 6A to 6D, the PWM signal generator 16 may include an inverter control IC 161 for generating a PWM signal in which pulse widths are randomly converted, and a first AC control signal ACS1 and a bias. A voltage adjusting unit 162 generating a second AC control signal ACS2 according to the voltage BDCv, and a second switching element switched in a turn-on or turn-off state according to the second AC control signal ACS2 ( Tr2 and a second resistor R2 to which the voltage VR2 that is changed according to the switching state of the second switching element Tr2 is applied. Here, the variable voltage VR2 is a value at which the voltage level is converted according to the resistance values of the second switching element Tr2 and the second resistor R2. That is, although the resistance value of the first resistor R2 is always fixed, the resistance value of the second switching element Tr2 varies depending on the turn-on or turn-off state. Accordingly, the sum of the resistance values of the second switching element Tr2 and the second resistor R2 is changed depending on the turn-on or turn-off state of the second switching element Tr2. The voltage applied to the second switching element Tr2 and the second resistor R2 is changed according to the changed resistance value. Here, the second switching device Tr2 has a constant gain as the analog signal is supplied.

The inverter control IC 161 converts the input voltage Vin into a triangular wave CW in accordance with the variable voltage VR2 from the second switching element Tr2 and the second resistor R2. The inverter control IC 141 includes a pulse generator (not shown) to generate a PWM signal according to the input voltage Vin and the reference voltage Vref. In this case, the second switching element Tr2 and the second resistor ( The pulse width is converted according to the variable voltage VR2 of the terminal to which R2) is connected. In addition, a PWM signal is generated and supplied to the inverter 12 by modulating the pulse width of the triangular wave CW in accordance with the reference voltage Vref.

The voltage adjusting unit 162 generates a second AC control signal ASC2 whose voltage level is converted according to the first AC control signal ACS1 and the bias voltage BDCv that are converted into a random frequency. Here, the second AC control signal ACS2 has a voltage level corresponding to the bias voltage BDCv as shown in FIG. 6A, and is output as a sine wave in which the frequency is randomly converted from about 180 Hz to 210 Hz.

The second switching element Tr2 is turned on or off according to the second AC control signal ACS2 from the voltage adjusting unit 162. Accordingly, the resistance value Ohm of the second switching element Tr2 and the second resistor R2 is changed according to the switching state of the second switching element Tr2, that is, the amplitude change of the second AC control signal ACS2. It randomly varies as shown in FIG. 6B.

Here, since the resistance value Ohm of the second switching element Tr2 is inversely proportional to the bias voltage BDCv, the higher the bias voltage BDCv is applied, the lower the resistance value Ohm of the second switching element Tr2 can be. have.

At this time, the variable voltage VR2 of the second switching element Tr2 and the second resistor R2 is inversely proportional to the resistance value Ohm of the second switching element Tr2 and the second resistor R2. Therefore, the pulse width of the triangular wave CW generated by the inverter control IC 161 is randomly converted as shown in FIG. 6C according to the variable voltage VR2.

The variable voltage VR2 may be represented by an AC waveform according to a gain value of the second switching element Tr2 since the AC control signal ACS2 input is an AC waveform. Therefore, the variable voltage VR2 has a waveform in which the variable voltage VR2 is synchronized with the AC control signal ACS in inverse proportion to the resistance value Ohm of the second switching element Tr2 and the second resistor R2.

The triangle wave CW shown in FIG. 6C has a narrow width when the resistance value Ohm shown in FIG. 6B is low, that is, when the voltage VR2 of the second resistor R2 is high, and the second resistor R2 is narrow. When the voltage VR2 is low, the width is wide.

Since the configuration and operation of the inverter control circuit IC 161 have been described above in detail in FIG. 3, the description thereof will be omitted. In addition, the triangular wave CW generated by the inverter control circuit IC 161 shown in FIGS. 6C and 6D and the PWM signal supplied to the inverter 12 are the same as the output waveforms shown in FIGS. 4C and 4D. That is, the voltage adjusting unit 162 is for supplying the bias voltage BDCv according to the operating characteristic of the second switching element Tr2.

The PWM generation unit 16 may not use the voltage adjusting unit 162 according to the operating characteristics of the second switching element Tr2, and according to the voltage adjusting unit 162, the second switching element Tr2 and the second switching element Tr2 may not be used. The resistance value Ohm of the resistor R2 may be adjusted according to the operating characteristics of various types of inverter control ICs 161.

The inverter control IC 141 may be used as a BD9884FV, a BD9885FV, a BD9766FV, or the like formed of a one-chip. At this time, the first resistor R1 connected in series with the first switching element Tr1 is connected to an input terminal of a clock generator of BD9766FV.

As shown in FIGS. 4A and 6A, the AC control signal ACS is randomly converted to a frequency of about 180 Hz to 210 Hz on a 32-inch basis, and is suitable for the size of the liquid crystal panel and the driving method of the backlight. It can be converted and supplied at random within the range.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is conventional in the art that various substitutions, modifications and changes are possible without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

The lamp driving method and apparatus according to the present invention as described above has the following effects.

According to the present invention, a pulse width of a PWM signal for driving an inverter is also randomly converted and supplied according to an AC control signal whose frequency is randomly converted. As a result, the web noise generated in the liquid crystal panel randomly moves in the up / down direction and cannot be detected by the naked eye.

Claims (26)

Generating a variable voltage according to a first AC control signal in which a frequency from the outside is converted; Generating a triangular wave whose pulse width is changed according to the variable voltage; Converting the triangular wave into a PWM signal according to a reference voltage from the outside; And And driving the lamp using the PWM signal. The method of claim 1, Generating the variable voltage Switching the switching element on or off according to the amplitude of the first AC signal, And generating a variable voltage by varying a resistance value according to a turn-on or turn-off state of the switching element. The method of claim 2, The variable voltage is The lamp driving method, characterized in that converted in proportion to the voltage of the first AC control signal. The method of claim 3, wherein The pulse width of the triangle wave Lamp driving method characterized in that converted in proportion to the variable voltage. The method of claim 1, The first AC control signal is Lamp driving method, characterized in that randomly converted to any frequency of 180Hz to 210Hz on the basis of 32 inches. The method of claim 1, Generating the variable voltage Generating a second AC control signal by converting a voltage level of the first AC control signal according to a preset bias voltage from the outside; and And generating a variable voltage according to the second AC control signal. The method of claim 6, The second AC control signal is And a voltage level of the first AC control signal is converted in proportion to the bias voltage. A PWM signal generator for generating a PWM signal whose pulse width is changed in accordance with a first AC control signal from the outside; And, And an inverter for driving the lamp in response to the PWM signal. 9. The method of claim 8, The PWM signal generator A first switching element switched according to the first AC control signal; A first resistor for varying a voltage according to the switching state of the first switching element, And an inverter control IC for converting an input voltage from the outside into a triangular wave so as to vary a pulse width according to the variable voltage, and generating a PWM signal in response to the triangular wave and the reference voltage converted from the pulse width. Drive system. The method of claim 9, Inverter control IC A triangular wave generator for converting the input voltage into a triangular wave having a variable pulse width according to the variable voltage; And a comparator for generating a PWM signal by modulating the pulse width of the triangle wave according to the reference voltage. 9. The method of claim 8, And a voltage adjusting unit configured to generate a second alternating current control signal converted from a voltage level of the first alternating current control signal according to a bias voltage from an external source, and supply the generated second alternating current control signal to the first switching element. The method of claim 11, The second AC control signal is And the voltage of the first AC control signal is increased or decreased in proportion to the bias voltage. 9. The method of claim 8, The first AC control signal is Lamp driving apparatus, characterized in that the randomly converted to any one of the frequency pulse width of 180Hz to 210Hz on the basis of 32 inches. Generating a variable voltage according to a first AC control signal in which a frequency from the outside is converted; Generating a triangular wave whose pulse width is changed according to the variable voltage; Converting the triangular wave into a PWM signal according to a reference voltage from the outside; And And driving a lamp by using the PWM signal. 15. The method of claim 14, Generating the variable voltage Switching the switching element on or off according to the amplitude of the first AC signal, And generating a variable voltage by varying a resistance value according to a turn-on or turn-off state of the switching device. 16. The method of claim 15, The variable voltage is And a method of converting the voltage in proportion to the voltage of the first AC control signal. 17. The method of claim 16, The pulse width of the triangle wave And a method of converting the variable voltage in proportion to the variable voltage. 15. The method of claim 14, The first AC control signal is 32. A method of driving a liquid crystal display device, characterized in that randomly converted to any one of 180Hz to 210Hz reference. 15. The method of claim 14, Generating the variable voltage Generating a second AC control signal by converting a voltage level of the first AC control signal according to a preset bias voltage from the outside; and And generating a variable voltage according to the second AC control signal. 20. The method of claim 19, The second AC control signal is And a voltage level of the first AC control signal is converted in proportion to the bias voltage. A liquid crystal panel displaying an image; A lamp for irradiating light onto the liquid crystal panel; A PWM signal generator for generating a PWM signal whose pulse width is changed in accordance with a first AC control signal from the outside; And, And an inverter for driving the lamp in response to the PWM signal. 22. The method of claim 21, The PWM signal generator A first switching element switched according to the first AC control signal; A first resistor for varying a voltage according to the switching state of the first switching element, And an inverter control IC for converting an input voltage from the outside into a triangular wave so as to vary a pulse width according to the variable voltage, and generating a PWM signal in response to the triangular wave converted from the pulse width and a reference voltage. Drive of display device. 23. The method of claim 22, Inverter control IC A triangular wave generator for converting the input voltage into a triangular wave having a variable pulse width according to the variable voltage; And a comparator for generating a PWM signal by modulating the pulse width of the triangle wave according to the reference voltage. 24. The method of claim 23, And a voltage adjusting unit configured to generate a second alternating current control signal converted from a voltage level of the first alternating current control signal according to a bias voltage from an external source, and supply the generated second alternating current control signal to the first switching element. Device. 25. The method of claim 24, The second AC control signal is And the voltage of the first AC control signal is increased or decreased in proportion to the bias voltage. 22. The method of claim 21, The first AC control signal is The driving device of the liquid crystal display device, characterized in that randomly converted to any one of the frequency pulse width of 180Hz to 210Hz on the basis of 32 inches.

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