KR101201133B1 - Device for driving backlight - Google Patents

Abstract

Disclosed is a backlight driving apparatus capable of preventing a malfunction.

The backlight driving apparatus of the present invention has a different reference voltage in the initial section and the normal section. That is, the first section has a first reference voltage, while the normal section has a second reference voltage that is at least greater than the first reference voltage. The first and second reference voltages may be compared with the output voltages of the transformers and the output of the controller may be cut off according to the comparison result. In this case, the first and second reference voltages may be set to be positioned between an output voltage in a normal case and an output voltage in an abnormal case.

Therefore, the present invention can prevent the malfunction due to the variation between the transformer, the influence of the stray capacitance when the voltage probe test pin contacts, and the impedance of the lamp due to the temperature change.

LCD, Backlight, Malfunction, LCC, Reference Voltage

Description

Backlight driving device {Device for driving backlight}

1 is a block diagram showing a backlight driving apparatus according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating the LCC protection circuit of FIG. 1 in detail. FIG.

3 is a circuit diagram illustrating one reference voltage variable part of FIG. 2;

4 shows waveforms of reference voltages.

FIG. 5 is a diagram illustrating a relationship between a comparison voltage and a reference voltage in an initial section and a normal section in the backlight driving apparatus of FIG. 1.

6 is a block diagram illustrating a backlight driving apparatus according to a second exemplary embodiment of the present invention.

7 is a block diagram illustrating in detail the LCC protection circuit of FIG.

FIG. 8 is a diagram illustrating a relationship between a comparison voltage and a reference voltage in an initial section and a normal section in the backlight driving apparatus of FIG. 6.

9 is a block diagram illustrating a backlight driving apparatus according to a third exemplary embodiment of the present invention.

FIG. 10 is a view illustrating changes in OVP level and FB level according to normal and abnormal cases. FIG.

FIG. 11 is a block diagram illustrating the LCC protection circuit of FIG. 9 in detail. FIG.

<Explanation of symbols for the main parts of the drawings>

11: control unit

13, 21: FET 15, 23: trance

17: Lamps 19, 31, 33, 41, 43: LCC protection circuit

25, 35: DC rectifier 26: reference voltage variable

27, 37: comparison unit 28, 38: switching unit

36: reference voltage delay

The present invention relates to a backlight, and more particularly, to a backlight driving apparatus capable of preventing a malfunction.

In general, a flat panel display includes a plasma display panel, a field emission display, a light emitting diode, and a liquid crystal display. Such flat panel display devices are classified into light emitting type and light receiving type. Plasma display panels, electroluminescent devices, and light emitting diodes are light emitting, and liquid crystal displays are light receiving.

In particular, since the liquid crystal display itself does not emit light, it is a light-receiving element that forms an image by injecting light from the outside, and thus there is a problem in that an image cannot be displayed in a dark place.

In order to solve this problem, a liquid crystal display (LCD) is provided with a backlight assembly on its back to irradiate light, thereby displaying an image even in a dark place.

Typical requirements for the backlight assembly are high brightness, high efficiency, uniformity of brightness, long life, thinness, light weight and low cost. In general, in the case of a monitor of a notebook, a high efficiency long life backlight assembly is required in order to lower power consumption, and in the case of a monitor or a TV of a general purpose PC, a high brightness backlight assembly is required.

The backlight assembly is provided with a lamp as a light source for providing light. According to the arrangement of the lamp on the display surface, it is divided into edge type and direct type. In the edge type backlight assembly, a lamp is disposed at an edge to irradiate light in a horizontal direction, and the irradiated light is advanced to a liquid crystal panel in front by a light guide plate. In contrast, in the direct backlight assembly, a plurality of lamps are arranged at regular intervals so that light provided from each lamp is directly directed to the front liquid crystal panel.

Cold Cathode Fluorescent Lamps (CCFLs) include lamps that meet high brightness requirements in backlight assemblies.

The cold cathode fluorescent lamp obtains a high voltage necessary for maintaining the discharge start light of the cold cathode fluorescent lamp by using a boost transformer of a low AC voltage of several tens of kHz obtained from an LC resonant inverter. At this time, the inverter output waveform is a sine wave. The LC resonant inverter has the advantage of relatively simple device and high efficiency, but there is a problem in that it is not possible to drive a single inverter by connecting a plurality of cold cathode fluorescent lamps in parallel. Therefore, in an edge type or direct type backlight employing a cold cathode fluorescent lamp, an inverter corresponding to the number of cold cathode fluorescent lamps is required.

In order to overcome the shortcomings of the cold cathode fluorescent lamp and to ensure the high brightness and high efficiency of the liquid crystal display device of the large size trend, the external electrode was formed in the electrodeless glass tube in response to the demand of the development of the backlight assembly which can guarantee the long life and the light weight. External Electrode Fluorescent Lamp (EEFL) has been developed.

Recently a number of gwanoe electrode fluorescent lamp as a backlight configured in such a way that arranged in the direct type on the reflection plate, and by the high frequency operation of them can MHz gwanoe electrode fluorescent lamp has high brightness of tens of thousands of cd / m ² were achieved.

These external electrode fluorescent lamps may be driven by using a single inverter by connecting a plurality of parallel.

When driving a plurality of external electrode fluorescent lamps as described above, a considerable amount of high current may flow at the output terminal of the inverter, that is, the output terminal of the transformer. Since the high current may be fatal when the human body is in contact with the human body, a backlight driving device having an LCC (Limit Current Circuit) protection circuit that blocks the driving of the external electrode fluorescent lamp when the human body is in contact with the human body is used.

When the human body contacts the secondary side of the transformer, the LCC protection circuit generates a predetermined enable signal based on the voltage sensed at the secondary side of the transformer to block driving of the backlight driver.

In the LCC protection circuit, a reference voltage is set for comparison with the voltage sensed on the secondary side of the transformer.

However, in the conventional backlight driver, the LCC protection circuit may malfunction due to variations between the transformers, the influence of stray capacitance upon contacting the voltage probe test pins, and the impedance of the lamp due to temperature change.

Accordingly, an object of the present invention is to provide a backlight driving apparatus capable of preventing a malfunction of an LCC protection circuit.

According to a first embodiment of the present invention for achieving the above object, a backlight driving device, a plurality of lamps; First and second transformers connected to both sides of the lamp; A control unit controlling the first and second transformers; And an LCC protection circuit that cuts off an output of the controller according to output voltages of the first and second transformers, wherein the LCC protection circuit includes a first reference voltage and a second reference voltage in a first section to be compared with the output voltage. It has a second reference voltage of the interval.

According to a second embodiment of the present invention, a backlight driving apparatus includes: a plurality of lamps; First and second transformers connected to both sides of the lamp; A control unit controlling the first and second transformers; A first LCC protection circuit blocking the output of the controller according to the output voltage of the first transformer; And a second LCC protection circuit which cuts off the output of the controller according to the output voltage of the second transformer, each LCC protection circuit having a reference voltage for comparison with the output voltage in a second section except the first section. It is delayed to have a predetermined level.

According to a third embodiment of the present invention, a backlight driving apparatus includes: a plurality of lamps; First and second transformers connected to both sides of the lamp; A control unit controlling the first and second transformers; A first LCC protection circuit blocking the output of the controller according to a first level of one side of the first transformer and a second level of the other side of the first transformer; And a second LCC protection circuit blocking the output of the controller according to the first level of one side of the second transformer and the second level of the other side of the second transformer.

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

1 is a block diagram illustrating a backlight driving apparatus according to a first embodiment of the present invention, and FIG. 2 is a block diagram showing the LCC protection circuit of FIG. 1 in detail.

Referring to FIG. 1, the controller 11 modulates pulse width modulation (PWM) to drive a plurality of lamps 17 and outputs PWM signals to the first and second FETs 13 and 21. DC voltage Vin is supplied to the first and second FETs 13 and 21 from the outside. Four transistors are connected to each of the first and second FETs 13 and 21 in parallel with one capacitor therebetween. The positive DC square voltage is output by the first pulse of the PWM signal, and the negative DC square voltage is output by the second pulse. Therefore, each of the FETs 13 and 21 alternately outputs positive and negative DC spherical voltages in response to each pulse of the PWM signal continuously input.

The first and second transformers 15 and 23 boost each DC square voltage to a sine wave voltage to a certain degree and output them to the plurality of lamps 17. Here, the plurality of lamps 17 represent an external electrode fluorescent lamp, and the plurality of external electrode fluorescent lamps are connected in parallel to the first and second transformers 15 and 23. As described above, it is an advantage of a backlight employing an external electrode fluorescent lamp that can drive a plurality of parallel connected external electrode fluorescent lamps with the first and second transformers 15 and 23.

As described above, since the external electrode fluorescent lamp is driven by the sine wave voltage maintained at a constant voltage from the first and second transformers 15 and 23, light having a uniform luminance may be emitted. In this case, the output voltage of the secondary side of the first transformer 15 and the output voltage of the secondary side of the second transformer 23 may be composed of sine waves having a phase difference of 180 °.

On the other hand, the voltage on the secondary side of the first and second transformers 15, 23, that is, between the first transformer 15 and the plurality of lamps 17 and between the second transformer 23 and the plurality of lamps 17. Is detected and provided to the LCC protection circuit 19.

The LCC protection circuit 19 provides an enable signal ENA to the controller 11 when the human body is in contact with the driver 11 to block driving of the backlight, and no signal is provided to the controller 11. Allow the backlight to operate normally.

The LCC protection circuit 19 includes a DC rectifier 25, a reference voltage variable unit 26, a comparison unit 27, and a switching unit 28.

The DC rectifier 25 combines the secondary voltage of the first transformer 15 and the secondary voltage of the second transformer 23 and rectifies the combined voltages into DC voltages. In the normal case, when the secondary voltage of the first transformer 15 and the secondary voltage of the second transformer 23 are combined, the voltage is almost zero. In contrast, in an abnormal case, the secondary voltage of the first transformer 15 and the secondary voltage of the second transformer 23 have a predetermined voltage. For example, when the human body contacts the secondary side of the second transformer 23, the voltage on the secondary side of the second transformer 23 decreases while the voltage on the secondary side of the first transformer 15 increases. Accordingly, when the secondary side voltage of the first transformer 15 and the secondary side voltage of the second transformer 23 are combined, a predetermined voltage is calculated rather than zero.

The reference voltage variable part 26 varies the voltage in the initial section and the normal section differently. For example, when the voltage in the initial section is called the first reference voltage Vref1 and the voltage in the normal section is called the second reference voltage Vref2, the second reference voltage may be changed to be larger than the first reference voltage. Can be.

Thus, a specific circuit for generating different reference voltages according to the initial section and the normal section is shown in FIG. 3.

3 is a diagram illustrating an example of a circuit of the reference voltage variable part of FIG. 2.

As shown in FIG. 3, in the reference voltage variable part 26, a first resistor R1 and a second resistor R2 are connected in series, and between the first resistor R1 and the second resistor R2. The transistor T1 is switched to distinguish between the initial section and the normal section, and a third resistor R3 connected in series with the transistor T1.

Transistor T1 is turned on / off by a control signal. The control signal has a high level in the initial section and a low level in the normal section.

Accordingly, the transistor T1 is turned on during the initial period, and the output first reference voltage Vref1 is expressed by Equation 1 below.

The transistor T1 is turned off during the normal period, and the output second reference voltage Vref2 is expressed by Equation 2 below.

As can be seen from Equations 1 and 2, the second reference voltage Vref2 is greater than the first reference voltage Vef1. For example, when R1, R2, and R3 are all 1Ω, the first reference voltage Vref1 is 1/3, and the second reference voltage Vref2 is 1/2. Therefore, as shown in FIG. 4, the second reference voltage Vref2 is larger than the first reference voltage Vref1 by the difference between the second reference voltage Vref2 and the first reference voltage Vref1.

The comparison unit 27 compares the comparison voltage output from the DC rectifier 25 with the reference voltage output from the reference voltage variable unit 26 and outputs an output value according to the comparison result. The comparison unit 27 may be configured as an amplifier in which a comparison voltage is input to the non-inverting terminal (+) and a reference voltage is input to the inversion terminal (−) to output an output value through the comparison. In this case, the high level signal is output when the comparison voltage is greater than the reference voltage, and the low level signal is output when the comparison voltage is less than the reference voltage.

The switching unit 28 is controlled on / off in accordance with the output signal of the comparison unit 27. For example, when the output of the comparator 27 is a high level signal, the switching unit 28 is turned on so that the enable signal ENA is output to the controller 11. On the contrary, when the output of the comparator 27 is a low level signal, the switching unit 28 is turned off so that the enable signal ENA is not output.

Since the control unit 11 blocks driving of the backlight by the enable signal ENA, the enable signal ENA should not be output from the switching unit 28 in the normal case.

Therefore, in the normal case, as shown in FIG. 5, the comparison voltage should be smaller than the reference voltage, and in the abnormal case, the comparison voltage should be larger than the reference voltage.

If the reference voltage has a constant DC voltage irrespective of the initial section and the normal section, as shown by the dotted line in FIG. 5, the comparison voltage and the reference voltage when the initial section is abnormal are crossed. In other words, a comparison voltage in an abnormal case may be smaller than a reference voltage in an initial section. This is mainly due to the variation between transformers, the effect of stray capacitance on contacting the voltage probe test pins, and the effect of the lamp's impedance with temperature changes.

When the comparison voltage in the abnormal case becomes smaller than the reference voltage, the low level signal is output from the comparator and the switching unit is turned off, so that the enable signal ENA is not output and the backlight is normally driven. This means a malfunction of the LCC protection circuit. That is, in abnormal cases, the comparison voltage should be larger than the reference voltage. However, since there is a comparison voltage smaller than the reference voltage, the LCC protection circuit malfunctions.

In order to solve this problem, the first embodiment of the present invention changes the reference voltage to different first and second reference voltages. That is, the first reference voltage is used during the initial period, and the second reference voltage is used during the normal period. In this case, the second reference voltage is preferably greater than the first reference voltage.

The first and second reference voltages may be designed by confirming the change of the comparison voltage of each of the normal case and the abnormal case in the initial section through an experiment and then confirming the result. That is, the first and second reference voltages are preferably set between the comparison voltage in the normal case and the comparison voltage in the abnormal case.

Therefore, according to the first embodiment of the present invention, the reference voltage is different from each other in the initial section and the normal section, so that the deviation between the transformer, the effect of stray capacitance at the voltage probe test pin contact, and the impedance of the lamp according to the temperature change are obtained. By improving the design margin of the impact, the malfunction of the LCC protection circuit can be prevented.

6 is a block diagram illustrating a backlight driving apparatus according to a second exemplary embodiment of the present invention, and FIG. 7 is a block diagram illustrating the LCC protection circuit of FIG. 6 in detail.

In the first embodiment of the present invention, the LCC protection circuit 19 using the sum of the voltages of the secondary side voltage of the first transformer 15 and the secondary side voltage of the second transformer 23 is provided. In the example, the first LCC protection circuit 31 using the secondary voltage of the first transformer 15 and the second LCC protection circuit 33 using the secondary voltage of the second transformer 23 are provided.

In this case, in the first embodiment of the present invention, the case where the grounded human body is in contact with the secondary side of either the first transformer 15 or the second transformer 23 will be described. In contrast, in the second embodiment of the present invention, the human body is in contact with the secondary side of the first transformer 15 and the secondary side of the second transformer 23, and the human body is not grounded.

Based on such a situation, the following description will focus on the portions that do not overlap with the first embodiment of the present invention.

As shown in FIG. 6, the backlight driving apparatus according to the second embodiment of the present invention includes a control unit 11, first and second FETs 13 and 21, first and second transformers 15 and 23, It consists of a plurality of lamps 17, first and second protection circuits 31, 33.

Since the controller 11, the first and second FETs 13 and 21, the first and second transformers 15 and 23, and the plurality of lamps 17 have been described above, further description thereof will be omitted.

The first protection circuit 31 is connected to the secondary side of the first transformer 15 to sense the secondary voltage of the first transformer 15 to determine whether there is an abnormality therefrom and take measures accordingly. Similarly, the second protection circuit 33 is connected to the secondary side of the second transformer 23 and detects the secondary voltage of the second transformer 23 to determine whether there is an abnormality therefrom and take action accordingly.

As shown in FIG. 7, the first and second protection circuits 31 and 33 each include a DC rectifier 35, a reference voltage delay unit 36, a comparator 37 and a switching unit 38. do.

The DC rectifier 35 rectifies the sinusoidal wave voltage of the secondary side of the first or second transformers 15 and 23 into a DC voltage and supplies the rectified voltage to the comparator 37.

The reference voltage delay unit 36 maintains the zero level during the initial period and delays the reference voltage by the initial period so that the reference voltage Vref2 having a predetermined level is output from the normal period.

The comparison unit 37 compares the comparison voltage output from the DC rectifier 35 with the reference voltage output from the reference voltage variable unit 36 and outputs an output value according to the comparison result. The comparison unit 37 may be configured as an amplifier in which a comparison voltage is input to the inverting terminal (−) and a reference voltage is input to the non-inverting terminal (+) to output an output value through the comparison. In this case, the low level signal is output when the comparison voltage is greater than the reference voltage, and the high level signal is output when the comparison voltage is less than the reference voltage.

The switching unit 38 is controlled on / off in accordance with the output signal of the comparison unit 37. For example, when the output of the comparator 37 is a high level signal, the switching unit is turned on so that the enable signal ENA is output to the controller 11. On the contrary, when the output of the comparator 37 is a low level signal, the switching unit 38 is turned off so that the enable signal ENA is not output.

Since the control unit 11 blocks driving of the backlight by the enable signal ENA, the enable signal ENA should not be output from the switching unit 38 in the normal case.

Therefore, in the normal case, as shown in FIG. 8, the comparison voltage should be larger than the reference voltage, and in the abnormal case, the comparison voltage should be smaller than the reference voltage.

If the reference voltage has a constant DC voltage regardless of the initial section and the normal section, as shown by the dotted line in FIG. 8, the comparison voltage and the reference voltage in the normal section in the initial section cross each other. In other words, it may occur that the comparison voltage in the normal case becomes smaller than the reference voltage in the initial section. This is mainly due to the variation between transformers, the effect of stray capacitance on contacting the voltage probe test pins, and the effect of the lamp's impedance with temperature changes.

When the comparison voltage in the normal case is smaller than the reference voltage, the high level signal is output from the comparator and the switching unit is turned on, so that the enable signal ENA is output, resulting in abnormal driving of the backlight. This means a malfunction of the LCC protection circuit. That is, in the normal case, the comparison voltage should be larger than the reference voltage. However, since there is a comparison voltage smaller than the reference voltage, the LCC protection circuit malfunctions.

In order to solve this problem, the second embodiment of the present invention is maintained at zero level during the initial period, and is then delayed to output a reference voltage having a predetermined level from the normal period. That is, a zero level is used during the initial period, and a reference voltage having a predetermined level is used during the normal period.

In the normal period, the reference voltage is preferably set between the comparison voltage in the normal case and the comparison voltage in the abnormal case.

Therefore, the second embodiment of the present invention maintains the reference voltage at zero level during the initial period, and delays the output of the reference voltage having a predetermined level from the normal period, thereby causing the parasitic capacitance between the transformer and the voltage probe test pin contact. It is possible to prevent the malfunction of the LCC protection circuit by improving the design margin of the influence of stray capacitance and the impedance effect of the lamp according to the temperature change.

9 is a block diagram illustrating a backlight driving apparatus according to a third exemplary embodiment of the present invention.

In the third embodiment of the present invention, since the control unit 11, the first and second FETs 13 and 21 and the plurality of lamps 17 have been described in the first embodiment of the present invention, further description thereof will be omitted. .

Each of the first and second transformers 15 and 23 is divided into one side and the other side on the secondary side. One side of the secondary side of each of the first and second transformers 15 and 23 is connected to a plurality of lamps 17 while an OVP level is detected from one side of the secondary side to prevent over voltage protection (OVP). It is supplied to an OVP protection circuit (not shown) provided for the purpose. A FB (Feed-Back) level is detected from the other side of the secondary side of each of the first and second transformers 15 and 23 and supplied to the control unit 11 to be used to adjust the luminous luminance.

In the third embodiment of the present invention, the OVP level and the FB level are supplied to the inputs of the first and second protection circuits 41 and 43, respectively, and the OVP level and the FB level are compared and normal or abnormal according to the comparison result. Judge and take action accordingly.

FIG. 10 is a diagram illustrating changes in OVP level and FB level according to normal and abnormal cases.

As shown in FIG. 10, in a normal case, the OVP level is greater than the FB level, and in an abnormal case, the FB level is greater than the OVP level. As such, the OVP level and the FB level show a very large rate of change depending on normal and abnormal cases. Therefore, the first and second LCC protection circuit is designed using this change rate.

As shown in FIG. 11, each of the first and second LCC protection circuits 41 and 43 is switched according to an output result of the comparator 45 and the comparator 45 comparing the OVP level and the FB level. It may be made of a switching unit 47.

The comparison unit 45 may include an amplifier having an inverting terminal (-) to which the OVP level is input and a non-inverting terminal to which the FB level is input.

The comparator 45 outputs a low level signal when the OVP level is greater than the FB level, that is, a normal level, and outputs a high level signal when the OVP level is smaller than the FB level, that is, abnormal.

When the low level signal is output from the comparator 45, the switching unit 47 maintains the off state, so that no enable signal ENA is supplied to the control unit 11 so that the backlight is normally driven. . On the contrary, since the switching unit 47 is turned on when the high level signal is output from the comparator 45, the enable signal ENA is supplied to the controller to block driving of the backlight.

Therefore, the LCC protection circuits 41 and 43 determine the normal or abnormal using the OVP level and the FB level having a large rate of change, so that the variation between transformers, the influence of stray capacitance on contacting the voltage probe test pin, and the temperature change It is not affected at all by the impedance effect of the lamp, thereby completely blocking the possibility of malfunction.

As described above, according to the present invention, by dividing the reference voltage into different first and second reference voltages or by delaying the reference voltage for a predetermined period, the parasitic capacitance at the time of contact between the transformer and the voltage probe test pin ( It is possible to prevent a malfunction from occurring due to the influence of stray capacitance and the impedance of the lamp according to the temperature change.

According to the present invention, by driving the LCC protection circuit using the OVP level and the FB level, malfunction due to the variation between the transformer, the effect of stray capacitance at the contact of the voltage probe test pin, and the impedance of the lamp due to the temperature change Can prevent this from happening.

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 invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

Claims (12)

A plurality of lamps; First and second transformers connected to both sides of the lamp; A control unit controlling the first and second transformers; And LCC protection circuit for blocking the output of the control unit in accordance with the output voltage of the first and second transformer, The LCC protection circuit generates a first reference voltage in an initial section and a second reference voltage in a normal section to be compared with output voltages of the first and second transformers. And a first reference voltage in the initial section is set at least lower than a second reference voltage in the normal section. delete The backlight driving apparatus of claim 1, wherein the first and second reference voltages are set to be positioned between the output voltage in a normal case and the output voltage in an abnormal case. The method of claim 1, wherein the LCC protection circuit, A rectifier for rectifying the output voltage; A reference voltage varying unit generating the first reference voltage in the initial section and generating the second reference voltage in the normal section; A comparator comparing the output voltage of the rectifier with the first or second reference voltage; And A switching unit switched according to a comparison result of the comparing unit Backlight driving device comprising a. A plurality of lamps; First and second transformers connected to both sides of the lamp; A control unit controlling the first and second transformers; A first LCC protection circuit blocking the output of the controller according to the output voltage of the first transformer; And A second LCC protection circuit which blocks the output of the controller according to the output voltage of the second transformer; Including, Each of the LCC protection circuits generates a first reference voltage in an initial period and a second reference voltage in a normal period for comparison with output voltages of the first and second transformers, The first reference voltage of the initial section is set to zero level, And a second reference voltage of the normal section is set to be larger than a first reference voltage of the initial section. delete 6. The backlight driving apparatus of claim 5, wherein the reference voltage is set to be located between the output voltage in a normal case and the output voltage in an abnormal case. The method of claim 5, wherein each LCC protection circuit, A rectifier for rectifying the output voltage; A reference voltage delay unit for maintaining a zero level during the initial period and delaying a reference voltage to have a predetermined level in the normal period; A comparator comparing the output voltage of the rectifier with the reference voltage; And A switching unit switched according to a comparison result of the comparing unit Backlight driving device comprising a. A plurality of lamps; First and second transformers connected to both sides of the lamp; A control unit controlling the first and second transformers; Outputting an enable signal for blocking the output of the controller according to a comparison between the first signal detected for overvoltage protection from one side of the first transformer and the second signal detected for luminance adjustment from the other side of the first transformer A first LCC protection circuit; And Outputting an enable signal for blocking the output of the controller according to a comparison between the first signal detected for overvoltage protection from one side of the second transformer and the second signal detected for luminance adjustment from the other side of the second transformer; Second LCC protection circuit Backlight driving device comprising a. delete delete delete

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