KR101539359B1 - A light source driving method, a light source device for performing the same, and a display device including the light source device - Google Patents

Abstract

A driving voltage is applied to one end of the plurality of light source strings connected in parallel to drive the light source strings. The peak current due to the voltage difference of each light source string is controlled to be controlled to make the average current of the light source strings constant.

Light source string, voltage deviation, peak current, switching control, average current

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention 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. BACKGROUND OF THE INVENTION 1. Field of the Invention [0001]

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, more particularly, to a light source driving method for safety, a light source device for performing the method, And a display device.

In general, liquid crystal displays are thin, light in weight and low in power consumption, and are used not only for monitors, notebooks, and mobile phones but also for large-sized TVs. The liquid crystal display device includes a liquid crystal display panel displaying an image using light transmittance of liquid crystal and a backlight assembly providing light to the liquid crystal display panel.

The backlight assembly may include a light source for generating light, and the light source may be a cold cathode fluorescent lamp, a hot cathode fluorescent lamp, a light emitting diode, or the like. Since the light emitting diode has low power consumption and high color reproducibility, it is widely used as a light source of the liquid crystal display device.

In recent years, in order to improve the contrast ratio of an image displayed on the liquid crystal display device, the liquid crystal display panel is divided into a plurality of regions, and a local dimming ) Method is being developed. The local dimming method reduces the amount of driving current supplied to the light emitting diodes located in the regions where the relatively dark images are displayed and decreases the amount of driving current supplied to the light emitting diodes located in the regions where relatively bright images are displayed Thereby increasing the amount of light.

As described above, when a local dimming scheme is employed using a light emitting diode, the backlight assembly includes a plurality of strings connected in parallel to each other and a multi-channel current control circuit for providing driving currents to the plurality of strings do. The string has a structure in which a plurality of light emitting diodes are connected in series.

The multi-channel current control circuit generally consumes voltage deviation between the light emitting diode strings to control the driving currents flowing through the light emitting diode strings equally. Therefore, there is a problem that the electronic device is damaged by the heat of the multi-channel current control circuit.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of driving a light source for protecting a light source device.

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 provided with the light source device.

According to an embodiment of the present invention, a driving voltage is applied to one end of a plurality of light source strings connected in parallel to drive the light source strings. And the peak current due to the voltage difference of each light source string is controlled to be controlled so that the average current of the light source strings is constant.

According to another aspect of the present invention, there is provided a light source apparatus including a light source module and a multi-channel current controller. The light source module receives a driving voltage at one end and a plurality of light source strings are connected in parallel. The multi-channel current controller is connected to the other end of each light source string, and controls the peak current due to the voltage difference of the light source string to control the average current of the light source strings.

According to another aspect of the present invention, there is provided a display device including a display panel, a light source module, and a multi-channel current controller. The display panel displays an image. The light source module receives a driving voltage at one end and a plurality of light source strings are connected in parallel. The multi-channel current controller is connected to the other end of each light source string, and controls the peak current due to the voltage difference of the light source string to control the average current of the light source strings.

According to the present invention, the average current of the light source strings can be maintained constant by controlling the voltage deviation of the light source strings in a switching manner in the peak current flowing through the light source strings. As a result, since the voltage deviation is not consumed as electric power, the element damage can be prevented by heat generation.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the drawings. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged from the actual size in order to clarify the present invention. The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, the terms "comprises", "having", and the like are used to specify that a feature, a number, a step, an operation, an element, a part or a combination thereof is described in the specification, But do not preclude the presence or addition of one or more other features, integers, steps, operations, components, parts, or combinations thereof. Also, where a section such as a layer, a film, an area, a plate, or the like is referred to as being "on" another section, it includes not only the case where it is "directly on" another part but also the case where there is another part in between. On the contrary, where a section such as a layer, a film, an area, a plate, etc. is referred to as being "under" another section, this includes not only the case where the section is "directly underneath"

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 170, and a light source device 290.

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

The timing controller 110 receives the control signal 101 and the video signal 102 from the outside. And generates a timing control signal for controlling the driving timing of the display panel 100 using the received control signal. The timing control signal includes a clock signal, a horizontal open signal, and a vertical start signal.

The panel driver 170 drives the display panel 100 under the control of the timing controller 110. The panel driver 170 includes a data driver 130 and a gate driver 150.

The data driver 130 drives the data line DL by using a data control signal and a video signal provided from the timing controller 110. That is, the data driver 130 converts the video signal into an analog data signal on the data line DL. The gate driver 150 drives the gate line GL using a gate control signal provided from the timing controller 110. [ That is, the gate driver 150 outputs a gate signal to the gate line GL.

The light source unit 290 includes a light source module 200, a local dimming control unit 210, a light source driving unit 230, a multi-channel voltage control unit 240, a multi-channel current control unit 250, and a power generation unit 270 do.

The light source module 200 is divided into a plurality of light-emitting blocks B, and each light-emitting block includes a light source string in which a plurality of light sources are connected in series. The light source includes a light emitting diode (LED), and the light emitting block includes a light emitting diode string (hereinafter referred to as an LED string) in which a plurality of light emitting diodes are connected in series. The light source module 200 includes a plurality of LED strings LS1, LS2, LS3, and LS4 connected in parallel to each other.

The local dimming control unit 210 divides the image signal into a plurality of image blocks D corresponding to the light emitting blocks B and controls the luminance of the light emitting blocks B in accordance with the gradation of each image block Thereby generating a dimming signal. For example, the dimming signal is a pulse width modulation (PWM) PWM signal.

The light source driving unit 230 boosts the input voltage Vin and provides the boosted driving voltage Vout to the common terminal connected in parallel with the plurality of LED strings LS1, LS2, LS3 and LS4. The light source driving unit 230 dims the light source module 200 for each light emitting block B using the PWM signal provided from the local dimming control unit 210.

The multi-channel voltage detector 240 is connected to the other ends of the LED strings LS1, LS2, LS3, and LS4. The multi-channel voltage detector 240 detects the voltages of the LED strings LS1, LS2, LS3, and LS4 in synchronization with the PWM signals. If the detected voltage is greater than the reference voltage, . The light source driver 230 operates in a protection mode in response to a detection voltage greater than the reference voltage. For example, the light source driver 230 does not provide the driving voltage Vout to the light source module 200. If the detected voltage is smaller than the reference voltage, the reference voltage is supplied to the light source driving unit 230, and the light source driving unit 230 operates in the normal mode.

The multi-channel current controller 250 is connected to the other ends of the LED strings LS1, LS2, LS3 and LS4. The multi-channel current controller 250 controls the peak current deviation flowing in the LED strings according to the voltage deviation of the LED strings LS1, LS2, LS3, and LS4 in synchronization with the PWM signals, The average current I _AVG of the strings LS1, LS2, LS3, LS4 is kept constant.

The power generator 270 provides the input voltage Vin to the light source driver 230.

2 is a detailed circuit diagram of the light source device shown in FIG.

1 and 2, the light source device 290 includes a light source module 200, a light source driver 230, a multi-channel voltage detector 240, and a multi-channel current controller 250.

The light source module 200 includes a plurality of LED strings connected in parallel, for example, first, second, third and fourth LED strings LS1, LS2, LS3 and LS4. Each LED string LS1 includes a plurality of light emitting diodes (LEDs).

The light source driving unit 230 includes an integrated circuit 231, a boosting circuit 233, and a feedback circuit 235. The integrated circuit 231 includes a protection terminal OVP including a gate terminal GATE electrically connected to the boosting circuit 233 and a sensing terminal CS and electrically connected to the feedback circuit 235 . The integrated circuit 231 controls the operation of the boosting circuit 233 based on the sensing signal received at the sensing terminal CS. Also, the integrated circuit 231 controls the operation of the integrated circuit 231 based on a signal received at the protection terminal OVP.

The boosting circuit 233 includes an inductor L, a boosting transistor FET1 and a diode D1. One end of the inductor L receives the input voltage Vin and the other end thereof is connected to the input electrode of the boosting transistor FET1. The boosting transistor FET1 includes a control electrode connected to the gate terminal GATE, an input electrode connected to the inductor L, and an output electrode connected to the sensing terminal CS. The diode D1 includes an anode connected in series with the other end of the inductor L and a first common terminal CM1 of the first, second, third and fourth LED strings LS1, LS2, LS3 and LS4, Lt; / RTI >

 When the boosting transistor FET1 is turned on, the inductor L stores the input voltage Vin as energy. When the boosting transistor FET1 is turned off, the energy stored in the inductor L is boosted to the driving voltage Vout. The driving voltage Vout is applied to the first common terminal CM1 through the diode D1.

Meanwhile, the sensing terminal CS detects an output signal flowing to the output electrode of the boosting transistor FET1, and the integrated circuit 231 controls the operation of the boosting circuit 233 in accordance with the detected output signal. For example, the integrated circuit 231 turns off the boosting transistor FET1 if the output signal is greater than the reference signal.

The feedback circuit 235 includes a resistor string connected in parallel to the other end of the first diode D1 and the resistor string is connected to the protection terminal OVP of the integrated circuit 231 via the N node N . The driving voltage Vout output from the boosting circuit 233 is distributed through the resistor string and the divided voltage is provided to the protection terminal OVP via the N-node N. [ That is, if the detection voltage detected by the multi-channel voltage detector 240 is larger than the voltage of the N-node N, the protection terminal OVP receives the detection voltage. On the other hand, if the detected voltage is smaller than the voltage of the N-node (N), the protection terminal (OVP) receives the voltage of the N-node (N). Therefore, the integrated circuit 231 operates in the protection mode when the detection voltage is received on the protection terminal OVP, and operates in the normal mode when the driving voltage Vout divided by the resistance string is received.

The multi-channel voltage detector 240 is connected to the other ends of the first through fourth LED strings LS1, LS2, LS3 and LS4, and the first through fourth LED strings LS1, LS2, LS3, LS2, LS3, and LS4 in synchronization with the PWM signals of the first to fourth LED strings LS1, LS2, LS3, and LS4.

For example, the first detection circuit 241 is connected to the other end of the first LED string LS1. The first detection circuit 241 includes a resistor R connected to the other end of the first LED string LS2 and a diode D2 comprising a cathode connected to the anode connected to the resistor R and a second common terminal CM2 ). The first detection circuit 241 further includes an input unit 241a that receives the PWM signal PWM1 corresponding to the first LED string LS. The input unit 241a is connected between the resistor R and the diode D2. When the high level is received at the input unit 241a, the first detection circuit 241 detects the voltage of the first LED string LS1. When the low level is received at the input unit 241a, The voltage of the string LS1 is not detected.

In the same manner, the detection circuits connected to the other ends of the second to fourth LED strings LS2, LS3 and LS4 are connected to the second common terminal CM2. The second common terminal CM2 is connected to the N-node N through a diode D3. The diode D3 includes an anode connected to the second common terminal CM2 and a cathode connected to the N node N. [

The multi-channel current controller 250 is connected to the other ends of the first through fourth LED strings LS1, LS2, LS3 and LS4. The multi-channel current controller 250 includes a plurality of current control circuits, and the current control circuits are connected to the first to fourth LED strings LS1, LS2, LS3, and LS4 in synchronization with the PWM signals. Detects peak currents, and controls switching of peak currents flowing in the first to fourth LED strings (LS1, LS2, LS3, LS4) according to the detected peak currents. As a result, the multi-channel current controller 250 maintains the average currents of the first through fourth LED strings LS1, LS2, LS3, and LS4 constant.

For example, the first current control circuit 251 is connected to the other end of the first LED string LS1. The current control circuit 251 includes an input unit 251a, a control transistor FET2, a filter 251b, and a comparator 251c.

The input unit 251a includes a diode D4 including an anode connected to the control electrode of the control transistor FET2 and a cathode for receiving the PWM signal. The first current control circuit 251 operates when a high level is received by the input unit 251a and the first current control circuit 251 does not operate when a low level of the input unit 251a is received.

The control transistor FET2 includes an input electrode connected to the other end of the first LED string LS1, an output electrode connected to the filter 251b, and a control electrode connected to the comparator 251c. The control transistor FET2 is turned on when the threshold voltage Vth is higher than the threshold voltage Vth and turned off when the control transistor FET2 is lower than the threshold voltage Vth.

The filter 251b is connected to the other end of the first LED string LS1 to determine a frequency of a peak current flowing in the first LED string LS1. For example, the filter 251b includes a resistor R connected to the output electrode of the control transistor FET2 and a capacitor C connected in parallel to the resistor R. The filter 251b may be different in frequency depending on the voltage deviation of the LED strings by setting the values of the resistor R and the capacitor C by predicting the state where the voltage deviation is the highest. Further, it is possible to set the frequency of the PWM signal higher than the frequency of the PWM signal when setting the time constant RC.

The filter 251b determines the frequency of the output signal of the control transistor FET2 corresponding to the peak current flowing in the first LED string LS1. The filter 251b inputs the comparison signal V _FED whose frequency has been determined to the comparator 251c.

The comparator 251c includes a reference terminal (+) for receiving the reference signal V _REF and a comparison terminal (-) for receiving the comparison signal V _FED . The comparator 251c outputs an output signal for controlling the turn-on and turn-off of the control transistor FET2 according to a comparison result between the reference signal V _REF and the comparison signal V _FED . For example, than the comparator (251c) is the comparison signal (V _FED) is the reference signal (V _REF) is smaller than the output signal of a low level, and the comparison signal (V _FED) is the reference signal (V _REF) And outputs a high level signal.

FIG. 3 is a circuit diagram for explaining driving of the light source device shown in FIG. 2. FIG. 4A and 4B are waveform diagrams of signals of the light source device shown in FIG.

2 to 4A, the light source apparatus includes a first LED string LS1 and a current control circuit 251 for controlling a peak current flowing through the LED string LS. The current control circuit 251 includes an input unit 251a, a control transistor (FET2), a filter 251b, and a comparator 251c.

One end of the first LED string LS1 receives the driving voltage Vout. The input unit 251a receives the PWM signal PWM1. When the PWM signal PWM1 is at the high level, the current control circuit 251 operates, and when the PWM signal PWM1 is at the low level, the current control circuit 251 does not operate.

The LED strings may have a resistance variation due to a design deviation, and a voltage deviation may occur accordingly. Relatively large current flows through the LED strings with relatively large voltage deviations. Therefore, when a voltage deviation Vf exists in the first LED string LS1, a high peak current I _LS corresponding to the voltage deviation Vf flows in the first LED string LS1.

The peak current I _LS flowing through the first LED string LS1 is input to the filter 251b via the control transistor FET2. The filter 251b determines the frequency of the peak current I _LS by the resistor R and the capacitor C. [ The peak current I _{LS for which} the frequency is determined is received at the comparator (-) of the comparator 251c, and the comparison signal V _FED is received. The frequency of the comparison signal V _FED has a frequency significantly greater than the frequency of the PWM signal. For example, the frequency of the comparison signal V _FED may be about 30 Hz which is about 20 times faster than the frequency of the PWM signal. Therefore, when the LED string is dimmed by the PWM signal, the comparison signal does not affect the resolution.

The comparator 251c compares the reference signal V _REF with the comparison signal V _FED . It said comparator (251c) is, if the comparison signal (V _FED), the output signals of the reference large low level than the signal (V _REF), and the comparison signal (V _FED) is less than the reference signal (V _REF) High Level signal.

Hereinafter, the operation of the current control circuit 251 will be described when a high-level PWM signal PWM1 is received at the input unit 251a.

3 and 4B, at a time T1 when the comparison signal V _FED reaches a level higher than the reference signal V _REF , the comparator 251 compares the comparison signal V _FED with the reference signal V _REF , And outputs a low level signal because it is larger than the reference signal V _REF . The output terminal (B node) of the comparator 251c drops to a low voltage and a voltage lower than the threshold voltage Vth is applied to the control electrode of the control transistor FET2. Accordingly, the control transistor (FET2) is turned off.

When the control transistor FET2 is turned off, a high voltage is applied to the other end (A node) of the first LED string LS1 connected to the input electrode of the control transistor FET2, and the peak current I _LS is almost It will not flow. The peak current I _LS does not flow in the first LED string LS1 during the first period TI1 during which the control transistor FET2 is turned off.

Thereafter, the comparison signal V _FED falls to a low level by the determined frequency. The comparator 251c outputs a high level signal because the comparison signal V _FED is smaller than the reference signal V _REF . The control transistor FET2 turns on at a time T2 when a voltage higher than the threshold voltage Vth is applied to the output terminal of the comparator 251c and the control electrode of the control transistor FET2 after a predetermined time, do. When the control transistor FET2 is turned on, a low voltage is applied to the other end (A node) of the first LED string LS1 and a peak current I _LS flows.

A peak current I _LS flows through the first LED string LS1 during the second period TI2 during which the control transistor FET2 is turned on.

As a result, the average current I _AVG of the LED strings is kept constant by controlling the turn-on and turn-off of the control transistor FET2 using the peak current deviation of the LED strings according to the voltage deviation. For example, if the peak current I _LS flowing through the LED string is large, the turn-off time of the control transistor FET 2 is increased. If the peak current I _LS is small, And keeps the average current I _AVG constant in a manner that reduces the turn-off time.

5 is a current waveform diagram according to a voltage deviation of the light source strings shown in FIG.

Referring to FIGS. 2 and 5, the voltage across the first LED string LS1 is 28.2V, the voltage across the second LED string LS2 is 27.1V, Second and third LED strings LS1, LS2, and LS3 when the voltage Vf3 across both terminals LS1, LS2, and LS3 is 26.0V.

The first LED string LS1 has a first current I1 having a first peak current PI1 and a first width W1. For example, the first peak current PI1 was about 75 mA. Wherein the second LED string LS2 is a current of a second frequency having a second peak current PI2 larger than the first peak current PI1 and a second width W2 smaller than the first width W1 I2) flowed. For example, the second peak current PI2 was about 150 mA. The third LED string LS3 is a third LED string LS3 having a third peak current PI3 larger than the second peak current PI2 and a third frequency W3 having a third width W3 smaller than the second width W2 I3). For example, the third peak current PI3 was about 230 mA.

On the other hand, the first to third currents I3 have the same average current I _AVG . For example, the average current I _AVG was about 65 mA.

Thus, different peak currents flowed in the LED strings according to the voltage deviation of the LED strings, but the peak currents were controlled in a switching manner so that the same average current flowed through the LED strings.

According to embodiments of the present invention, the average current of the light source strings can be kept constant by controlling switching of the peak current flowing through the light source strings according to the voltage deviation of the light source strings. As a result, since the voltage deviation is not consumed as electric power, the element damage can be prevented by heat generation.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. You will understand.

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

2 is a detailed circuit diagram of the light source device shown in FIG.

FIG. 3 is a circuit diagram for explaining driving of the light source device shown in FIG. 2. FIG.

4A and 4B are waveform diagrams of signals of the light source device shown in FIG.

5 is a current waveform diagram according to a voltage deviation of the light source strings shown in FIG.

Description of the Related Art

100: display panel 110: timing controller

130: Data driver 140: Gate driver

150: panel driving unit 300: light source device

210: local dimming control unit 230: light source driving unit

240: multi-channel voltage detector 250: multi-channel current controller

LS1: first LED string 251: current control circuit

251a: input unit 251b: filter

251c: comparator FET2: control transistor

Claims (18)

1. Driving the light source strings by applying a driving voltage to one end of the plurality of light source strings connected in parallel; And

   And controlling a peak current due to a voltage difference of each light source string to control an average current of the light source strings,

   And a comparator for comparing the reference signal and the comparison signal, and for controlling switching of the peak current, determining a frequency of the peak current flowing in the light source string, outputting the comparison signal in which the frequency is determined, And outputs an output signal for controlling turn-off to a control electrode of the control transistor.
2. The method of claim 1, wherein driving the light source strings

   Wherein the light source strings are driven in synchronization with dimming signals for controlling the luminance of each of the light source strings.
3. 3. The method of claim 2, wherein the frequency of the switching controlled peak currents is greater than the frequency of the dimming signals.
4. 2. The method of claim 1, wherein the step of < RTI ID = 0.0 >

   Wherein when the peak current of the light source string is large, the time during which the peak current flows is reduced, and when the peak current of the light source string is small, the time during which the peak current flows is increased.
5. A light source module which receives a driving voltage at one end and to which a plurality of light source strings are connected in parallel; And

   And a multi-channel current controller connected to the other end of each light source string for controlling the peak current due to the voltage difference of the light source string to control the average current of the light source strings,

   Wherein the multi-channel current controller includes a plurality of current control circuits connected to the light source strings,

   A filter connected to the other end of the light source string to determine a frequency of the peak current flowing through the light source string and to output a comparison signal in which the frequency is determined;

   A control transistor including an input electrode connected to the other end of the light source string and an output electrode connected to the filter; And

   And a comparator for outputting an output signal for controlling the turn-on and turn-off of the control transistor to the control electrode of the control transistor according to a result of comparison between the reference signal and the comparison signal.
6. 6. The semiconductor memory device according to claim 5, wherein each of the current control circuits

   Wherein when the peak current of each light source string is large, the time for which the peak current flows is reduced, and when the peak current of each light source string is small, the time for which the peak current flows is increased.
7. delete
8. The liquid crystal display of claim 5, wherein the current control circuit further comprises a first input connected between an output terminal of the comparator and a control electrode of the control transistor, for receiving a dimming signal for controlling the brightness of the light source string .
9. The light source device according to claim 8, wherein the frequency of the peak current is larger than the frequency of the dimming signal.
10. The apparatus of claim 8, further comprising: a multi-channel voltage detector connected to the other ends of the light source strings to detect a detection voltage from the light source strings; And

    And a light source driving unit for controlling the generation of the driving voltage according to the detection voltage.
11. 11. The image pickup apparatus according to claim 10, wherein the multi-channel voltage detector includes a plurality of detection circuits connected to the other ends of the light source strings,

    A resistor connected to the other end of each light source string; a diode connected to the resistor; and a second input connected between the resistor and the diode to receive the dimming signal.
12. A display panel for displaying an image;

    A light source module which receives a driving voltage at one end and to which a plurality of light source strings are connected in parallel; And

    And a multi-channel current controller connected to the other end of each light source string for controlling the peak current due to the voltage difference of the light source string to control the average current of the light source strings,

    Wherein the multi-channel current controller includes a plurality of current control circuits connected to the light source strings,

    A filter connected to the other end of the light source string to determine a frequency of the peak current flowing through the light source string and to output a comparison signal in which the frequency is determined;

    A control transistor including an input electrode connected to the other end of the light source string and an output electrode connected to the filter; And

    And a comparator for outputting an output signal for controlling the turn-on and turn-off of the control transistor to the control electrode of the control transistor according to a result of comparison between the reference signal and the comparison signal.
13. 13. The semiconductor device according to claim 12, wherein each of the current control circuits

    Wherein when the peak current of each light source string is large, the time for which the peak current flows is reduced, and when the peak current of each light source string is small, the time for which the peak current flows is increased.
14. delete
15. 13. The light emitting device of claim 12, wherein the current control circuit further comprises a first input connected between the output terminal of the comparator and the control electrode of the control transistor, for receiving a dimming signal for controlling the brightness of the light source string / RTI >
16. 16. The display device according to claim 15, wherein a frequency of the peak current is larger than a frequency of the dimming signal.
17. 16. The apparatus of claim 15, further comprising: a multi-channel voltage detector connected to the other ends of the light source strings to detect a detection voltage from the light source strings; And

    And a light source driving unit for controlling the generation of the driving voltage according to the detection voltage.
18. 18. The apparatus of claim 17, wherein the multi-channel voltage detector includes a plurality of detection circuits connected to the other ends of the light source strings,

    A resistor connected to the other end of each light source string; a diode connected to the resistor; and a second input connected between the resistor and the diode to receive the dimming signal.

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