KR100679214B1 - Error detection device for back light unit - Google Patents

Abstract

An error detector for a backlight unit is provided to detect the error of respective lamps constituting the backlight unit in real-time, thereby improving the operative efficiency of the backlight unit. First and second substrates(20a,20b) are configured to fix both terminals of cold cathode fluorescent lamps(10). First and second capacitors are electrically connected to the both terminals of the cold cathode fluorescent lamp. The first capacitors are commonly connected to a first common terminal(22a), and the second capacitors are commonly connected to a second common terminal(22b). An inverter(30) is configured to supply voltage between the first common terminal and the second common terminal. A pattern capacitor series(410) is composed of capacitors, which receive the voltages between the cold cathode fluorescent lamps and the first capacitors. An error detector(420) compares the common output voltage of the capacitors constituting the pattern capacitor series with reference voltage applied between the cold cathode fluorescent lamp and the capacitor to transfer the comparing result to the inverter.

Description

Error detection device for backlight unit

1 is a view illustrating an error detection apparatus for a general backlight unit and an error detection method using the same;

2 is a view for explaining an error detection apparatus for a backlight unit according to the present invention;

3 is a detailed configuration diagram of the malfunction detection unit illustrated in FIG. 2.

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

10: lamp 20a, 20b: substrate

22a, 22b: common terminal 30: inverter

32: switching unit 34: transformer

36: current detector 38: pulse width modulator

410: pattern capacitor series 420: malfunction detection unit

The present invention relates to an error detection device for a circuit element, and more particularly, to an error detection device for a backlight unit for immediately detecting an error by detecting the operation of a lamp used as a light source of the backlight unit.

The liquid crystal display (LCD) has a wide range of applications due to characteristics such as light weight, thinness, and low power consumption, and transmits light beams according to image signals applied to a plurality of control switches arranged in a matrix. To display the desired image on the screen. Since the LCD is not a self-luminous display device, a light source such as a backlight is required, and a cold cathode fluorescent lamp (hereinafter referred to as 'CCFL') is a typical light source.

CCFL is a light source tube using the cold cathode emission phenomenon has the characteristics of low heat generation, high brightness, long life and easy full color. The CCFL includes a light guide type, a direct type type, a reflective type plate, and the like, and a light source tube of a suitable type is adopted according to the requirements of the LCD.

In the backlight unit using the CCFL, when the fastening of the CCFL occurs, there is a problem such as high voltage is generated due to overheating and fire in severe cases. You must stop it.

1 is a view illustrating an error detection apparatus for a backlight unit implemented using a general CCFL and an error detection method using the same.

As shown, the plurality of CCFLs 10 have both terminals fixed to the first and second substrates 20a and 20b, respectively, and capacitors C are connected to the respective terminals, and the first substrate 20a. The capacitor on the side is connected to the first common terminal 22a, and the capacitor on the second substrate 20b side is connected to the second common terminal 22b.

In order to drive the CCFL, an AC voltage of several tens of KHz and several hundred volts are required. An inverter 30 is used as a means for applying the driving voltage. The inverter 30 is connected between the first common terminal 22a and the second common terminal 22b to input the input voltage Vin input from a power supply (not shown) to the first and second common terminals 22a and 22b. ) Or block it if necessary.

More specifically, the inverter 30 converts the voltage supplied by the switching unit 32 and the switching unit 32 to switch the voltage from the voltage source Vin according to the switching control signal to the lamp driving voltage. Transformer 34, a current detector 36 for detecting tube current of each CCFL, and a pulse width modulator 38 for switching the switch 32 in response to a feedback signal from the current detector 36. .

On the other hand, two capacitors are connected in series between one end and the other end of the secondary winding of the transformer 34, and the error detection device 40 having a voltage difference between the two capacitors as an input includes a voltage applied to the output terminal of the transformer and a reference voltage Vref. ), When the difference between the output voltage and the reference voltage is greater than the set level, it is detected that an error has occurred, and the switching unit 32 is turned off to prevent the voltage from being supplied to the CCFL 10.

In more detail, when a plurality of CCFLs 10 are connected in parallel and controlled by one inverter 30, when one CCFL is separated from the connection terminal, the current induced in the output terminal does not change. , The voltage rises for example 20-30Vac. When the voltage rises as described above, the error detection apparatus 40 compares the increased output voltage with the reference voltage and turns off the switching unit 32 so that the voltage is no longer supplied when the difference is greater than or equal to the specified level.

However, when the reliability test of the backlight unit is performed at cryogenic temperatures (for example, -20 ° C), the efficiency of the CCFL is lowered and the tube voltage is increased by about 150 to 200 Vac. Accordingly, when the error detection criterion of the backlight unit is determined based on this, the circuit driving may be stopped even when no error occurs in the CCFL when the backlight unit is actually driven. In order to solve this problem, in actual backlight unit production, margins are set to stop the operation of the backlight unit when 7 to 8 CCFLs have an error.

In other words, it is currently difficult to accurately detect errors for each CCFL constituting the backlight unit. Therefore, a larger range than necessary is applied to stop the operation of the backlight unit. have.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and there is a technical problem to improve the operation efficiency of the backlight unit by accurately detecting an error for each lamp constituting the backlight unit in real time.

According to an aspect of the present invention, a first and a second substrate on which both terminals of a plurality of cold cathode fluorescent lamps are fixed, a capacitor connected to both terminals of the cold cathode fluorescent lamp, and the first substrate side An error of a backlight unit including a first common terminal to which a capacitor is commonly connected, a second common terminal to which a capacitor on the second substrate side is commonly connected, and an inverter for supplying or blocking voltage between the first and second common terminals. A detection apparatus, comprising: a pattern capacitor series comprising a plurality of capacitors each receiving a voltage applied between the cold cathode fluorescent lamp and the capacitor on the first substrate side; And a malfunction detection unit for transferring the comparison result to the inverter by comparing the common output voltages of the plurality of capacitors constituting the pattern capacitor series with a reference voltage applied between the cold cathode fluorescent lamp and the capacitor. do.

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

2 is a view for explaining an error detection apparatus for a backlight unit according to the present invention, a case where a backlight unit is configured using a CCFL will be described as an example.

As shown, an error detecting apparatus for a backlight unit according to the present invention includes a pattern capacitor series 410 and a malfunction detection unit 420. The structure of the backlight unit to which such an error detecting apparatus is connected will be described below. Same as

In the plurality of CCFLs 10, both terminals thereof are fixed to the first and second substrates 20a and 20b, respectively, and capacitors C are connected to the respective terminals, and the capacitors on the side of the first substrate 20a It is connected to one common terminal 22a, and the capacitor of the 2nd board | substrate 20b side is connected to the 2nd common terminal 22b.

In order to drive the CCFL, an AC voltage of several tens of KHz and several hundred volts are required. An inverter 30 is used as a means for applying the driving voltage. The inverter 30 is connected between the first common terminal 22a and the second common terminal 22b to input the input voltage Vin input from a power supply (not shown) to the first and second common terminals 22a and 22b. ) Or block it if necessary.

More specifically, the inverter 30 converts the voltage supplied by the switching unit 32 and the switching unit 32 to switch the voltage from the voltage source Vin according to the switching control signal to the lamp driving voltage. Transformer 34, a current detector 36 for detecting tube current of each CCFL, and a pulse width modulator 38 for switching the switch 32 in response to a feedback signal from the current detector 36. .

Here, the switching unit 32 includes at least one switch element for switching the voltage to the transformer 34 according to the switching control signal. In addition, the transformer 34 is composed of a primary winding having both ends connected to the switching unit 32 and a secondary winding having one end connected to the first common terminal 22a and the other end being grounded, and by the turns ratio of the primary and secondary windings. The voltage supplied to the primary winding is converted and induced in the secondary winding. The voltage induced in the secondary winding is supplied to the CCFL 10 through the first common terminal 22a to turn on the CCFL 10. The pulse width modulator 38 controls the voltage supplied to the transformer 34 by controlling the switching period of the switching element constituting the switch 32 in response to the output signal of the current detector 36.

Here, the voltages of the first node N1 and the second node N2 of the capacitor connected between the CCFL 10 and the first common terminal 22a may be, for example, when the backlight unit operates normally. The voltage of N1 is 850 Vac and the voltage of the second node N2 is 530 Vac. When one CCFL 10 is separated from the substrate, the voltage of the first node N1 is almost unchanged, but the second node N2 is not changed. ) Drops to about 200Vac, for example, 305Vac. Therefore, when the voltage change of the second node N2 is sensed and the voltage change amount is greater than or equal to the specified level, if the voltage is not supplied to the CCFL 10, the malfunction of the backlight unit may be prevented.

In this way, in the cryogenic test of the backlight unit, it is possible to solve the problem that a reference value for error detection cannot be accurately set due to an increase in tube voltage. That is, the error of the backlight unit can be accurately detected without being affected by the change in the tube voltage caused by the temperature change of the CCFL 10.

To this end, in the present invention, a plurality of capacitors constituting a pattern capacitor series 410 and a pattern capacitor series 410 including a plurality of capacitors receiving voltages applied to each second node N2 of the capacitor C, respectively. When the difference between the common output voltage of the pattern capacitor series 410 and the second node reference voltage is greater than the set level, compared to the common output voltage V _Cp and the preset second node reference voltage Vref_N2, the switching unit ( An error detection device including a malfunction detection unit 420 for turning off 32 is provided.

In a preferred embodiment of the present invention, the pattern capacitor series 410 may be formed on the first substrate 20a or the second substrate 20b, and the malfunction detection unit 420 may be implemented as shown in FIG. 3. In addition, the second node reference voltage may be changed according to the number of CCFLs 10 constituting the backlight unit, a required input voltage value, and the number of allowable deviation CCFLs.

3 is a detailed configuration diagram of the malfunction detection unit illustrated in FIG. 2.

As illustrated, the malfunction detection unit 420 is connected between the ground terminal and the input terminal of the malfunction detection unit 420 to prevent the signal backflow, and thus the output voltage V _Cp of the first diode D1 and the pattern capacitor series 410. ) Is a first resistor element R1 and a first resistor element R1 connected in series to an output terminal of a second diode D2, a second diode D2 for rectifying an AC signal inputted as a DC signal. And a second resistor element R2 connected between the output terminal of the first resistor element R1 and the ground terminal, and a capacitor C1 connected in parallel with the second resistor element R2 between the output terminal of the first resistor element R1 and the ground terminal. 1 When the voltage input through the resistor R1 and the preset second node reference voltage Vref_N2 are compared, and the difference between the two voltage values is greater than the preset level, a control signal for turning off the switching unit 32 is provided. Output comparator (R2 and C1 Please briefly explain the function).

That is, the second node DC voltage of the capacitor connected to the CCFL 10 is sensed as 38.5V in a normal operating state, for example, when the CCFL 10 is separated from the substrate, it is sensed as 32.4V, The voltage change value is compared with the second node reference voltage to prevent the voltage from being supplied to the backlight unit when the difference is more than the set level.

The second node voltage of the capacitor connected to the CCFL 10 can be measured accurately, and since it is not influenced by the tube voltage of the CCFL 10, an error situation due to departure of the CCFL can be accurately detected in real time. .

As such, those skilled in the art will appreciate that the present invention can be implemented in other specific forms without changing the technical spirit or essential features thereof. Therefore, the above-described embodiments are to be understood as illustrative in all respects and not as restrictive. The scope of the present invention is shown by the following claims rather than the detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

According to the present invention, the backlight unit in which a plurality of CCFLs are connected in parallel can detect the state of each CCFL in real time and immediately stop the operation of the backlight unit when an error occurs. As a result, problems such as overvoltage flow through the backlight unit and damage to the circuit may occur, and the reliability of the backlight unit may be improved.

Claims (3)

First and second substrates on which both terminals of the plurality of cold cathode fluorescent lamps are fixed, a capacitor connected to both terminals of the cold cathode fluorescent lamp, respectively, a first common terminal to which the capacitors on the first substrate side are commonly connected, and An error detection apparatus for a backlight unit including a second common terminal to which a capacitor on a second substrate side is commonly connected, and an inverter for supplying or blocking a voltage between the first and second common terminals, A pattern capacitor series including a plurality of capacitors each receiving a voltage applied between the cold cathode fluorescent lamp and the capacitor on the first substrate side; And A malfunction detection unit for transferring the comparison result to the inverter by comparing the common output voltages of the plurality of capacitors constituting the pattern capacitor series with a reference voltage applied between the cold cathode fluorescent lamp and the capacitor; Error detection device for a backlight unit comprising a. The method of claim 1, The malfunction detection unit detects an error for the backlight unit when the difference between the common output voltage of the pattern capacitor series and the reference voltage is greater than a preset value, the inverter cuts off the voltage supply. Device. The method of claim 1, The malfunction detection unit may include a first diode connected between the ground terminal and the input terminal to prevent signal backflow; A second diode for rectifying an AC signal input by using a common output voltage of the pattern capacitor series as a DC signal; A first resistor element connected in series with the output terminal of the second diode; A second resistance element connected between an output terminal of the first resistance element and a ground terminal; A capacitor connected in parallel with a second resistance element between an output terminal of the first resistance element and a ground terminal; And A comparator for comparing a voltage input through the first resistance element with a preset reference voltage and transmitting a control signal according to a difference between two voltage values to the inverter; Error detection device for a backlight unit comprising a.

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