KR20130135487A - Method of driving light-source, light-source apparatus for performing the method and display apparatus having the light-source apparatus - Google Patents

Abstract

A light source operating method of a light source module including a light emitting diode string connected with a plurality of light emitting diodes adjusts a frequency of a boosting switching signal based on a dimming signal controlling the brightness of the string and controls a main transistor delivering an operating voltage to the string in response to the boosting switching signal. A step of adjusting the frequency of the boosting switching signal generates a triangle wave of a first operating frequency when a level of the dimming signal is greater than a set value and generates a triangle wave of a second operating frequency when a level of the dimming signal is smaller than a set value. Therefore, when a dimming signal having a duty rate of less than 1 % is applied to the light source module, the brightness control of the module is easily performed by preventing an output current of the module to decrease. The light and shade contrast of a display device is improved. [Reference numerals] (251e) Integrated circuit

Description

A light source driving method, a light source device for performing the same, and a display device including the light source device.

The present invention relates to a light source driving method, a light source device for performing the same, and a display device including the light source device. The present invention relates to a light source driving method for improving contrast ratio and a display device for performing the same.

In general, a liquid crystal display device includes a liquid crystal display panel displaying an image using light transmittance of a liquid crystal, and a backlight assembly disposed under the liquid crystal display panel and providing light to the liquid crystal display panel.

The liquid crystal display panel includes an array substrate having pixel electrodes and a thin film transistor electrically connected to the pixel electrodes, a color filter substrate having a common electrode and color filters, and a liquid crystal layer interposed between the array substrate and the color filter substrate. It includes. The arrangement of the liquid crystal layer is changed by an electric field formed between the pixel electrodes and the common electrode, thereby changing the transmittance of light passing through the liquid crystal layer. Herein, when the light transmittance is increased to the maximum, the liquid crystal display panel may implement a white image having high luminance, whereas when the light transmittance is reduced to the minimum, the liquid crystal display panel may implement a black image having low luminance. .

Recently, a PWM dimming method has been developed that uses a plurality of light emitting diodes as the backlight assembly and controls the amount of light based on the brightness of an image displayed on the liquid crystal display panel. The PWM dimming method is a method of controlling the amount of light of the light emitting diode by adjusting the duty ratio of the pulse. In the PWM dimming method, when the duty ratio of the pulse is about 1% to about 2% or less, the high level of the current output to the light emitting diode drops sharply, which makes it difficult to control the light emitting diode.

The technical problem to be solved by the present invention is to solve such a conventional problem, an object of the present invention is to provide a light source driving method for facilitating light amount control.

Another object of the present invention is to provide a light source device for performing the light source driving method.

It is still another object of the present invention to provide a display device including the light source device.

According to one or more embodiments, a light source driving method of a light source module including a light emitting diode string having a plurality of light emitting diodes connected in series is based on a dimming signal for controlling the brightness of the light emitting diode string. Adjusting a frequency of a boosting switching signal, and controlling a main transistor that transmits a driving voltage to the light emitting diode string in response to the boosting switching signal.

In the present embodiment, adjusting the frequency of the boosting switching signal may include generating a triangular wave of a first driving frequency when the level of the dimming signal is greater than a set value;

The method may include generating a first boosting switching signal by using the triangular wave of the first driving frequency.

In the present exemplary embodiment, adjusting the frequency of the boosting switching signal may include generating a triangular wave of a second driving frequency that is higher than the first driving frequency when the level of the dimming signal is smaller than a set value and the second driving frequency. Generating a second boosting switching signal using a triangular wave of the.

In the present embodiment, the set value may correspond to the dimming signal having a pulse duty ratio of 1% to 2%.

The method may further include outputting the boosting switching signal by comparing the output current of the LED string with a reference signal.

A light source device according to an embodiment for achieving another object of the present invention includes a light source module and a driving signal generator. The light source module includes a light emitting diode string in which a plurality of light emitting diodes are connected in series. The driving signal generator includes a main transistor for transmitting a driving voltage to the light emitting diode string, and adjusts a driving frequency of a boosting switching signal based on a dimming signal for controlling the luminance of the light emitting diode string, and the main transistor is configured to boost the boosting signal. The driving voltage is transmitted to the LED string in response to a switching signal.

In this embodiment, the drive signal generator is a frequency oscillator for generating a triangular wave, frequency modulation for modulating the drive frequency of the triangular wave to a first drive frequency and a second drive frequency higher than the first drive frequency based on the dimming signal And a DC / DC converter including the main transistor and transferring the driving voltage to the LED string in response to a first or second boosting switching signal based on a triangular wave of the first or second driving frequency. can do.

In the present exemplary embodiment, the frequency modulator may include an input unit receiving the dimming signal, a voltage divider dividing a voltage of the dimming signal, a diode unit connecting the input unit and the voltage divider, and a division voltage provided from the voltage divider. A resistor may include an oscillation transistor driving in response and at least one second resistor element included in the frequency oscillator and connected in parallel with a first resistor element determining a driving frequency of the triangle wave.

In this embodiment, the frequency modulator may be implemented as one integrated circuit with the frequency oscillator.

In example embodiments, when the division voltage is greater than the threshold voltage of the oscillation transistor, the oscillation transistor may be turned off, and the frequency oscillator may generate a triangular wave of the first driving frequency.

In the present embodiment, when the division voltage is smaller than the threshold voltage of the oscillation transistor, the oscillation transistor is turned on, and the frequency oscillation part is driven based on the first and second resistance elements connected in parallel. Can generate a triangular wave of frequency.

In the present embodiment, the threshold voltage of the oscillation transistor may correspond to the division voltage of the dimming signal having a pulse duty ratio of 1% to 2%.

In this embodiment, the input unit is connected to the first input terminal for receiving a dimming signal of the AC signal, the first input terminal, a digital-to-analog converter for converting the AC signal into a DC signal and a dimming signal of the DC signal It may include a second input terminal for receiving.

In an embodiment, the driving signal generator may further include a current feedback unit, and the current feedback unit may include a first OP amplifier and the comparison signal configured to compare the output current of the LED string with a reference signal and output a comparison signal. It may include a second OP amplifier for outputting the boosting switching signal using the triangular wave.

According to another aspect of the present invention, a display device includes a display panel, a light source module, and a light source driver. The display panel displays the received image signal. The light source module includes a light emitting diode string in which a plurality of light emitting diodes are connected in series. The light source driver includes a main transistor configured to transfer a driving voltage to the light emitting diode string, and adjusts a driving frequency of a boosting switching signal based on a dimming signal for controlling the brightness of the light emitting diode string, and the main transistor is configured to boost the switching. The driving voltage is transmitted to the light emitting diode string in response to the signal.

The light source driver may include an image analyzer configured to analyze the image signal to determine a target luminance value of the LED string, and a dimming level determiner to determine a dimming signal of the LED string using the target luminance value. And a driving signal generator which adjusts a driving frequency of a boosting switching signal based on the dimming signal and drives the main transistor in response to the boosting switching signal.

In this embodiment, the driving signal generator is a frequency oscillator for generating a triangular wave, a frequency for modulating the driving frequency of the triangular wave into a first driving frequency and a second driving frequency higher than the first driving frequency based on the dimming signal A DC / DC converter including a modulator and the main transistor and transferring the driving voltage to the light emitting diode string in response to a first or second boosting switching signal based on a triangular wave of the first or second driving frequency. It may include.

In the present exemplary embodiment, the frequency modulator may include an input unit receiving the dimming signal, a voltage divider dividing a voltage of the dimming signal, a diode unit connecting the input unit and the voltage divider, and a division voltage provided from the voltage divider. And an oscillation transistor for driving in response, and a resistor unit including at least one second resistor element included in the frequency oscillator and connected in parallel with a first resistor element determining a driving frequency of the triangle wave.

In the present embodiment, the oscillation transistor may be a PNP type.

In the present embodiment, the display panel is divided into a plurality of display blocks, and the light source module includes a plurality of light emitting blocks corresponding to the display blocks, and each light emitting block includes at least one LED string. It may include.

According to embodiments of the present invention, when a dimming signal having a low duty ratio of 1% or less is applied to the light source module, it is possible to easily control the brightness of the light source module by preventing the output current of the light source module from falling. Therefore, the contrast ratio of the display device can be improved.

1 is a block diagram of a display device according to an embodiment of the present invention.
FIG. 2 is a circuit diagram of the driving signal generator of FIG. 1.
3 is a flowchart illustrating a driving method of the driving signal generator of FIG. 2.
4A and 4B are waveform diagrams illustrating an output current of an LED string according to a dimming signal having a low duty ratio.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings.

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

Referring to FIG. 1, the display device includes a display panel 100, a timing controller 110, a panel driver 130, a light source module 200, and a light source driver 290.

The display panel 100 includes a plurality of pixels for displaying an image. For example, the pixels are M × N (M and N are natural numbers). Each pixel P includes a switching element TR connected to a gate line GL and a data line DL, a liquid crystal capacitor CLC connected to the switching element TR, and a storage capacitor CST.

The timing controller 110 receives a synchronization signal and an image signal from the outside. A timing control signal for controlling the driving timing of the display panel 100 is generated using the synchronization signal. The timing control signal includes a clock signal, a horizontal synchronization signal, and a vertical synchronization signal.

The panel driver 130 drives the display panel 100 using the synchronization signal and the image signal provided from the timing controller 110. For example, the panel driver 130 may provide a gate driver for generating a gate signal provided to the gate line GL using a vertical synchronization signal, and provide the gate line to the data line DL using the horizontal synchronization signal. And a data driver for generating a data signal.

The light source module 200 provides light to the display panel 100. The light source module 200 includes at least one light emitting block LB, and the light emitting block LB includes at least one light emitting diode string (hereinafter, referred to as an LED string), and the LED string includes a plurality of LED strings. Light emitting diodes (LEDs) are connected in series. The light source module 200 may include a plurality of light emitting blocks LB. Each of the light emitting blocks LB may have a brightness determined based on a brightness of an image displayed on the display block DB of the display panel 100. The light emitting blocks LB of the light source module 200 may be linearly arranged, or may be arranged in a matrix form. The light source module 200 may be driven in the local dimming manner by the light emitting blocks LB.

The light source driver 290 includes an image analyzer 210, a dimming level determiner 230, and a driving signal generator 250.

The image analyzer 210 determines a target luminance value by using the received synchronization signal and the image signal.

The dimming level determiner 230 generates a dimming signal for controlling the amount of light of the light source module 200 using the target luminance value. The driving method of the light source module 200 may include a method of collectively adjusting the luminance of the entire region and a method of independently adjusting the luminance for each region. The dimming signal may include a PWM dimming method for controlling the luminance with a PWM dimming signal and an analog dimming method for controlling the luminance with a DC signal. The PWM dimming method controls the luminance ratio of the light emitting block by controlling the duty ratio of the pulse signal, and the analog dimming signal controls the luminance of the light emission block by controlling the voltage level of the DC signal. The PWM dimming scheme may include an external dimming scheme for receiving a pulsed external diving signal from the outside, and an internal dimming scheme for receiving a DC voltage from the outside and generating a pulsed signal therein. In the present embodiment, a PWM dimming method is described as an example. The driving signal generator 250 provides a driving voltage to the light source module 200 using the dimming signal. The driving signal generator 250 applies a driving voltage to the light source module 200 in response to the first boosting switching signal having the first driving frequency when the level of the dimming signal, for example, the duty ratio is greater than a predetermined value, When the duty ratio of the dimming signal is less than the set value, the driving voltage is provided to the light source module 200 based on the second boosting switching signal having the second driving frequency higher than the first driving frequency. The set point may correspond to a duty ratio of about 1% to about 2%. The set value may be variously set without being limited thereto.

Accordingly, when the dimming signal having a duty ratio lower than a set value is applied to the light source module 200, the output of the light source module 200 is instantaneously increased by increasing the number of times the driving voltage is provided to the light source module 200. The current can be prevented from falling.

FIG. 2 is a circuit diagram of the driving signal generator of FIG. 1.

1 and 2, the display device includes a driving signal generator 250 and the light source module 200. The light source module 200 may be independently driven by at least one light emitting block, and the light emitting block may include at least one LED string LS.

The driving signal generator 250 includes a DC / DC converter 251, a frequency oscillator 252, a frequency modulator 253, and a current feedback unit 254.

The DC / DC converter 251 includes a booster 251a, a main transistor 251b, a rectifier 251c, a charger 251d, and an integrated circuit 251e. The boosting unit 251a includes an inductor L1. The boosting unit 251a boosts the input voltage Vin to the driving voltage Vout according to the operation of the main transistor 251b. The main transistor 251b includes a control electrode connected to the integrated circuit 251e, an input electrode connected to the boosting unit 251a, and an output electrode connected to ground. The main transistor 251b turns on or off in response to a boosting switching signal provided from the integrated circuit 251e. The rectifying unit 251c includes a diode D1 and connects the boosting unit 251a and the charging unit 251d. The charging unit 251d includes a capacitor C1 and is connected between the rectifying unit 251c and one end of the LED string LS to charge the driving voltage Vout.

 The integrated circuit 251e performs a boosting operation and a dimming operation for driving the LED string LS. For example, the integrated circuit 251e controls the main transistor 251b based on the boosting switching signal received from the current feedback unit 254.

The frequency oscillator 252 generates a triangular wave that oscillates, and generates a triangular wave of a first driving frequency and a second driving frequency under the control of the frequency modulator 253.

The frequency oscillator 252 may include a plurality of OP amplifiers, a plurality of resistors, a plurality of diodes, and at least one capacitor, and may be implemented in various oscillation circuits. For example, the frequency oscillator 252 may generate a triangular wave of a driving frequency fop based on Equation 1.

Equation 1

The resistance value RRT of Equation 1 may correspond to the resistance value of the first resistance element R3 included in the frequency oscillator 252. In other words, the driving frequency of the triangular wave may be determined by the resistance value of the first resistance element R3.

The frequency modulator 253 includes an input unit 253a, a diode unit 253b, a voltage divider 253c, an oscillation transistor 253d, and a resistor unit 253e, and based on the level of the dimming signal, Modulates the driving frequency of the triangle wave.

The input unit 253a includes a first input terminal IT1 for receiving an external dimming signal E_DIM and a second input terminal IT2 for receiving an internal dimming signal I_DIM. The first input terminal IT1 further includes a digital-to-analog converter DAC. The external dimming signal E_IM is an AC signal including a pulse and converts the AC signal into a DC signal such as a DC voltage through the digital-to-analog converter DAC. The internal dimming signal I_DIM is a direct current signal such as a DC voltage. The internal dimming signal I_DIM may be about 0V to about 3.3V. The input unit 253a selectively receives the external dimming signal E_DIM and the internal dimming signal I_DIM.

The diode unit 253b includes a first diode D8 connected to the first input terminal IT1 and a second diode D9 connected to the second input terminal IT2. The external or internal dimming signal received from the input unit 253a is applied to the voltage divider 253c through the diode unit 253b.

The voltage divider 253c includes a plurality of resistors R7 and R8 connected in series. The voltage divider 253c divides a voltage corresponding to the external or internal dimming signal and applies a divided voltage to the oscillation transistor 253d.

The oscillation transistor 253d is a PNP type transistor, and includes a control electrode connected to the voltage divider 253c, an input electrode connected to the frequency oscillator 252, and an output electrode connected to the resistor 253e. . When the division voltage of the oscillation transistor 253d is smaller than the threshold voltage of the oscillation transistor 253d, the oscillation transistor 253d is turned on. When the oscillation transistor 253d is turned on, the resistor unit 253e is connected in parallel with the first resistor element R3 that affects the driving frequency.

On the contrary, when the division voltage is greater than the threshold voltage of the oscillation transistor 253d, the oscillation transistor 253d is turned off. When the oscillation transistor 253d is turned off, the frequency modulator 253 is electrically cut off from the frequency oscillator 252 so that the frequency oscillator 252 generates a triangular wave of the set first driving frequency. .

The resistor unit 253e includes at least one second resistor element R6 connected in parallel with the first resistor element R3 of the frequency oscillator 252. When the oscillation transistor 253d is turned on, the second resistance element R6 is connected in parallel with the first resistance element R3 so that the resistance value RRT of Equation 1 decreases. The driving frequency fop is inversely proportional to the resistance value RRT, and as a result, the frequency oscillator 252 generates a triangular wave of a second driving frequency that is higher than the first driving frequency.

That is, when the level of the external or internal dimming signal received by the input unit 253a exceeds a set value, the oscillation transistor 253d is turned off and the frequency oscillator 252 has a triangular wave having a first driving frequency of low frequency. Occurs. On the other hand, when the level of the external or internal dimming signal received by the input unit 253a is smaller than the set value, the oscillation transistor 253d is turned on and the frequency oscillator 252 generates a triangular wave having a second driving frequency of high frequency. Occurs. The set value may be set to a level of the external or internal dimming signal, eg, a duty ratio of about 1% to about 2%.

The frequency modulator 253 according to the present embodiment may be implemented as an external application circuit or may be embedded in the frequency oscillator 252. The frequency modulator 253 may be variously implemented without being limited thereto.

The current feedback unit 254 includes a first OP amplifier 254a and a second OP amplifier 254b. The current feedback unit 254 determines the duty ratio of the boosting switching signal based on the output current of the LED string LS.

For example, the first OP amplifier 254a outputs a first comparison signal and a second comparison signal by comparing the detected voltage sensed from the second end of the LED string LS with a reference voltage Vref. The first OP amplifier 254a outputs a first comparison signal when the detection voltage is greater than the reference voltage Vref, and outputs a second comparison signal when the detection voltage is less than the reference voltage Vref.

The second OP amplifier 254b outputs the boosting switching signal using the first or second comparison signal output from the first OP amplifier 254a and the triangular wave received from the frequency oscillator 252. The second OP amplifier 254b outputs the boosting switching signal having a relatively reduced duty ratio when the first comparison signal is received, and outputs the boosting switching signal having a relatively increased duty ratio when the second comparison signal is received. Output Therefore, the current feedback unit 254 may keep the output current flowing in the LED string LS constant.

Although not shown, the frequency modulator 253 may be embedded in the frequency oscillator 252 and implemented as a single integrated circuit.

3 is a flowchart illustrating a driving method of the driving signal generator of FIG. 2.

1, 2 and 3, a case where an external dimming signal, which is a pulse signal, is received by the driving signal generator 250 will be described as an example.

The external dimming signal E_DIM is received at the first input terminal IT1 (step S110).

The frequency modulator 253 determines the duty ratio of the received external dimming signal E_DIM (step S120).

For example, the external dimming signal E_DIM, which is the pulse signal, is converted into a first voltage in an analog form through a digital-to-analog converter DAC. The first voltage is divided into a second voltage lower than the first voltage through the voltage divider 253c and applied to the oscillation transistor 253d. The threshold voltage of the oscillation transistor 253d may be set to correspond to a duty ratio of about 1% for a dimming signal having a duty ratio in a range of 0% to 100%. That is, it may be determined whether the duty ratio of the external dimming signal E_DIM is greater than or less than 1% according to the operation of the PNP type oscillation transistor 253d.

When the duty ratio of the external dimming signal E_DIM is greater than the set value of 1%, the oscillation transistor 253d is turned off. When the oscillation transistor 253d is turned off, the frequency modulator 253 is electrically cut off from the frequency oscillator 252.

Therefore, the frequency oscillator 252 generates a triangular wave of the set first driving frequency (step S130).

The triangular wave of the first driving frequency is provided to the current feedback unit 254, and the second OP amplifier 254b of the current feedback unit 254 is used to compare the comparison signal output from the first OP amplifier 254a and the The first boosting switching signal, which is a pulse signal, is output using the triangular wave of the first driving frequency (step S140). The first boosting switching signal may have the first driving frequency.

The integrated circuit 251e of the DC / DC converter 251 controls the driving of the main transistor 251b based on the first boosting switching signal. In response to the first boosting switching signal having the first driving frequency, the main transistor 251b applies the driving voltage Vout boosted by the input voltage Vin to the LED string LS. Accordingly, the LED string LS is emitted (step S190).

On the other hand, when the duty ratio of the external dimming signal E_DIM is less than the set value of 1%, the oscillation transistor 253d is turned on. When the oscillation transistor 253d is turned on, the first resistance element R3 of the frequency oscillator 252 and the second resistance element R6 of the frequency modulator 253 are connected in parallel with each other. That is, the second resistance element R6 is connected in parallel with the first resistance element R3 to reduce the resistance value RRT of Equation 1 for controlling the driving frequency of the frequency oscillator 252. As a result, the frequency oscillator 252 generates a triangular wave of a second driving frequency higher than the first driving frequency (step S150).

The triangular wave of the second driving frequency is provided to the current feedback unit 254, and the second OP amplifier 254b of the current feedback unit 254 is a comparison signal output from the first OP amplifier 254a and the The second boosting switching signal is output using the triangular wave of the second driving frequency (step S160). The second boosting switching signal may have the second driving frequency.

The integrated circuit 251e of the DC / DC converter 251 controls the driving of the main transistor 251b based on the second boosting switching signal. In response to the second boosting switching signal having the second driving frequency, the main transistor 251b applies the driving voltage Vout boosted by the input voltage Vin to the LED string LS. This causes the LED string LS to emit light (step S190).

The number of times that the driving voltage Vout is applied to the first end of the LED string LS for a predetermined time is increased in the case of the second boosting switching signal which is high frequency compared to the first boosting switching signal. Therefore, in the case of a dimming signal having a low duty ratio of about 1% or less, the number of times that the driving voltage Vout is applied to the LED string LS is increased to increase the amount of current flowing in the LED string LS instantaneously. Can be increased. Therefore, in the case of the dimming signal having a low duty ratio of about 1% or less, it is possible to prevent the high level of the output current flowing through the LED string LS from falling.

According to the present exemplary embodiment, the luminance control of the light source module can be facilitated with respect to the dimming signal having a high duty ratio as well as the dimming signal having a low duty ratio of 1% or less. Therefore, the contrast ratio of the display device can be improved.

4A and 4B are waveform diagrams illustrating an output current of an LED string according to a dimming signal having a low duty ratio. 4A is a graph illustrating an output current of a boosting switching signal and an LED string according to an embodiment, and FIG. 4B is a graph illustrating an output current of a boosting switching signal and an LED string according to a comparative example.

2 and 4A, when the duty ratio of the dimming signal DIM is less than 1%, the frequency oscillator 252 may generate a high frequency triangular wave under the control of the frequency modulator 253. The current feedback unit 254 outputs a high frequency boosting switching signal H_Cb based on a high frequency triangular wave. The output current Iout of the LED string could maintain the desired high level.

2 and 4B, according to a comparative example in which the frequency modulator 253 is omitted, when the duty ratio of the dimming signal DIM is less than 1%, the frequency oscillator 252 is set. A low frequency triangular wave is output, and the current feedback unit 254 outputs a low frequency boosting switching signal L_Cb based on the low frequency triangular wave. The output current Iout of the LED string has decreased in high level.

According to an embodiment of the present invention, when a dimming signal having a low duty ratio of 1% or less is applied to the light source module, the output current of the light source module may be prevented from falling, and consequently, the brightness control may be facilitated to provide contrast. Can improve rain.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined in the appended claims. It will be possible.

100: display panel 110: timing control unit
130 panel driver 200 light source module
210: image analyzer 230: dimming level determiner
290: drive signal generator 251: DC / DC converter
252: frequency oscillator 253: frequency modulator
254: current feedback LS: LED string

Claims (20)

In a light source driving method of a light source module including a light emitting diode string in which a plurality of light emitting diodes are connected in series,
Adjusting a frequency of a boosting switching signal based on a dimming signal for controlling the brightness of the LED string; And
Controlling a main transistor that transmits a driving voltage to the light emitting diode string in response to the boosting switching signal. The method of claim 1, wherein adjusting the frequency of the boosting switching signal comprises:
Generating a triangular wave of a first driving frequency when the level of the dimming signal is greater than a predetermined value; And
And generating a first boosting switching signal by using the triangular wave of the first driving frequency. 3. The method of claim 2, wherein adjusting the frequency of the boosting switching signal
Generating a triangular wave of a second driving frequency that is higher in frequency than the first driving frequency when the level of the dimming signal is smaller than a predetermined value; And
And generating a second boosting switching signal using the triangular wave of the second driving frequency. The method of claim 3, wherein the set value corresponds to the dimming signal having a pulse duty ratio of 1% to 2%. The light source driving method of claim 1, further comprising outputting the boosting switching signal by comparing an output current of the light emitting diode string with a reference signal. A light source module including a light emitting diode string in which a plurality of light emitting diodes are connected in series; And
And a main transistor configured to transfer a driving voltage to the light emitting diode string, wherein the main transistor adjusts a driving frequency of a boosting switching signal based on a dimming signal for controlling the brightness of the light emitting diode string. And a driving signal generator for transmitting the driving voltage to the light emitting diode string. The method of claim 6, wherein the driving signal generating unit
A frequency oscillator for generating triangular waves;
A frequency modulator configured to modulate the driving frequency of the triangular wave into a first driving frequency and a second driving frequency higher than the first driving frequency based on the dimming signal; And
A light source device including the main transistor and a DC / DC converter configured to transfer the driving voltage to the light emitting diode string in response to a first or second boosting switching signal based on a triangular wave of the first or second driving frequency. . The method of claim 7, wherein the frequency modulator
An input unit to receive the dimming signal;
A voltage divider dividing a voltage of the dimming signal;
A diode unit connecting the input unit and the voltage divider unit;
An oscillation transistor for driving in response to the division voltage provided from the voltage division unit; And
And a resistor unit including at least one second resistor element included in the frequency oscillator and connected in parallel with a first resistor element determining a driving frequency of the triangle wave. The light source device of claim 8, wherein the frequency modulator is implemented as one integrated circuit with the frequency oscillator. The oscillation transistor of claim 9, wherein the oscillation transistor is turned off when the division voltage is greater than a threshold voltage of the oscillation transistor.
And the frequency oscillator generates a triangular wave of the first driving frequency. The oscillation transistor of claim 9, wherein the oscillation transistor is turned on when the division voltage is less than a threshold voltage of the oscillation transistor.
The frequency oscillator generates a triangular wave of the second driving frequency based on the first and second resistance elements connected in parallel. 10. The light source device of claim 9, wherein the threshold voltage of the oscillation transistor corresponds to a division voltage of a dimming signal having a pulse duty ratio of 1% to 2%. The method of claim 8, wherein the input unit
A first input terminal for receiving a dimming signal of an AC signal;
A digital-to-analog converter connected to the first input terminal to convert the AC signal into a DC signal; And
And a second input terminal for receiving a dimming signal of a direct current signal. The method of claim 7, wherein the drive signal generator further comprises a current feedback,
The current feedback unit
A first OP amplifier comparing the output current of the LED string with a reference signal and outputting a comparison signal; And
And a second OP amplifier configured to output the boosting switching signal using the comparison signal and the triangle wave. A display panel displaying a received video signal;
A light source module including a light emitting diode string in which a plurality of light emitting diodes are connected in series; And
And a main transistor configured to transfer a driving voltage to the light emitting diode string, wherein the main transistor adjusts a driving frequency of a boosting switching signal based on a dimming signal for controlling the brightness of the light emitting diode string. And a light source driver configured to transfer the driving voltage to the light emitting diode string. The method of claim 15, wherein the light source driver
An image analyzer configured to analyze the image signal to determine a target luminance value of the LED string;
A dimming level determiner configured to determine a dimming signal of the LED string using the target luminance value; And
And a driving signal generator configured to adjust the driving frequency of a boosting switching signal based on the dimming signal and to drive the main transistor in response to the boosting switching signal. The method of claim 16, wherein the drive signal generation unit
A frequency oscillator for generating triangular waves;
A frequency modulator for modulating the driving frequency of the triangular wave into a first driving frequency and a second driving frequency that is higher than the first driving frequency based on the dimming signal; And
A display device including the main transistor and a DC / DC converter configured to transfer the driving voltage to the light emitting diode string in response to a first or second boosting switching signal based on a triangular wave of the first or second driving frequency. . The method of claim 17, wherein the frequency modulator
An input unit to receive the dimming signal;
A voltage divider dividing a voltage of the dimming signal;
A diode unit connecting the input unit and the voltage divider unit;
An oscillation transistor for driving in response to the division voltage provided from the voltage division unit; And
And a resistor unit including at least one second resistor element included in the frequency oscillator and connected in parallel with a first resistor element determining a driving frequency of the triangle wave. 19. The display device according to claim 18, wherein the oscillation transistor is a PNP type. The display device of claim 15, wherein the display panel is divided into a plurality of display blocks.
The light source module may include a plurality of light emitting blocks corresponding to the display blocks, and each light emitting block may include at least one light emitting diode string.

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