KR20080062534A - Device for driving backlight unit - Google Patents

Abstract

An apparatus for driving backlight unit is provided to detect waveforms of output voltages of a master and a slave and supply a detected signal to a control IC(Integrated Circuit) to control the master and the slave according to the detected signal and adjust a tube current of a lamp to thereby achieve a stabilized operation of a backlight unit. An apparatus for driving a backlight unit includes a detector(173a,173b) and a control IC(Integrated Circuit)(171). The backlight unit includes an inverter having a master driver(130) and a slave driver(150) for applying high voltages respectively having opposite phases to both terminals of a lamp(120). The detector compares voltages output from the master driver and the slave driver with each other to detect whether the inverter normally operates. The control IC controls a tube current of the lamp in response to a signal detected by the detector.

Description

Backlight Unit Driver {DEVICE FOR DRIVING BACKLIGHT UNIT}

1 is a view showing the structure of a backlight unit according to an embodiment of the present invention.

2 is a view showing the internal configuration of the inverter of FIG.

3 is a detailed view of the sensing circuit of FIG.

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

120: lamp 130: master

150: slave 170: control unit

171: control IC 173a: first sensing circuit

173b: second sensing circuit 201: first comparator

203: first latch portion 205: second comparison portion

207: second latch portion

The present invention relates to a backlight unit driving device, and more particularly to a stable and reliable backlight unit driving device.

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.

Among these, the liquid crystal display device is an element that changes the optical anisotropy by applying an electric field to the liquid crystal having the liquidity and the optical properties of the crystal, the power consumption is low and the volume is smaller than the conventional cathode ray tube (CRT) It is widely used because it can be enlarged and fixed.

In recent years, as the screen size of a liquid crystal display device increases, the demand for a high brightness backlight unit increases. In order to implement this, development of a direct type backlight unit that arranges a plurality of lamps under the display screen or bends one lamp is continuing.

Fluorescent lamps mainly used in the direct type backlight unit are classified according to the position of the electrode. ), There is an External Electrode Fluorescent Lamp (EEFL) with an external electrode.

In addition, an inverter is used to drive the backlight unit. The inverter converts direct current (DC) power into alternating current (AC) power to supply driving power required for a lamp. In such an inverter, feedback control for controlling the set brightness is used, and in this case, a pulse width modulation (PWM) scheme is applied to control the brightness in the feedback control.

The backlight unit using the external electrode fluorescent lamp (EEFL) drives the lamp on / off by applying a high voltage having a different phase to each side of the external electrode fluorescent lamps (EEFL).

As such, in the backlight unit having the external electrode fluorescent lamp EEFL, a large amount of high current may flow at the output terminal of the inverter, that is, at 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 unit having a protection circuit that blocks the driving of the external electrode fluorescent lamp (EEFL) when the human body is in contact with the human body is used.

In general, the protection circuit includes a detection unit that detects an electrical characteristic signal, that is, a current signal or a voltage signal, and a determination unit that compares the signal detected by the detection unit with a reference value and determines whether to shut off the backlight unit based on the result.

The protective circuit loses its operation upon test or body contact. That is, when the protective circuit test or body contact, the detection unit is open or shorted so that no signal can be detected. As a result, the judgment unit also cannot make any judgments, which eventually causes the function of the protection circuit to be lost.

An object of the present invention is to provide a backlight unit driving apparatus that can improve the reliability.

In addition, an object of the present invention is to provide a driving device of a backlight unit that can be stably operated.

Driving device of the backlight unit according to an embodiment of the present invention for achieving the above object,

In the inverter comprising a master driver and a slave driver for applying a high voltage of the inverted phase to both ends of the lamp,

A detector for detecting an abnormality of the inverter by comparing the voltages output from the master driver and the slave driver;

It includes a control IC for adjusting the tube current of the lamp in response to the sensed signal supplied from the detection unit.

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

1 is a view showing the structure of a backlight unit according to an embodiment of the present invention, Figure 2 is a view showing the internal configuration of the inverter of FIG.

As shown in FIG. 1 and FIG. 2, the backlight unit according to an exemplary embodiment of the present invention is configured to apply a driving voltage to a plurality of lamps 120 arranged at regular intervals and both sides of the lamp 120. It includes a master (130) and a slave (slave: 150), and a controller 170 for controlling the master 130 and the slave 150.

Usually, the inverter includes the controller 170, the master 130, the slave 150, and the like.

The master 130 includes a first driver 131 including a field effect transistor (FET) and a first transformer for converting a current output from the first driver 131 into a voltage for supplying the lamp 120. transformer 133 and a first feedback circuit 135 for feeding back the waveform of the first transformer 133.

The slave 150 may include a second driver 151, a second transformer 153, corresponding to the first driver 131, the first transformer 133, and the first feedback circuit 135 of the master 130. The second feedback circuit 155 is included.

The master 130 and the slave 150 are disposed at both sides of the plurality of lamps 120, and high voltages having different phases from the master 130 and the slave 150 are respectively provided at both electrodes of the lamps 120. Is approved.

The controller 170 detects an abnormal operation by detecting an output voltage of the control IC 171 for controlling the operations of the master 130 and the slave 150 and the output voltages of the master 130 and the slave 150. And first and second sensing circuits 173a and 173b.

The control IC 170 is composed of a two-channel IC having two channels capable of adjusting output voltages output from the master 130 and the slave 150, respectively.

The inverter of the backlight unit having the above structure outputs high voltages from the master 130 and the slave 150, and applies them to the plurality of lamps 120. At this time, the phase difference between the voltage output from the master 130 and the slave 150 is usually a half period (180 degrees).

When the phase of the output voltage output from the master 130 and the output voltage output from the slave 150 overlaps with each other, the control IC 171 controls a low tube current such that the driving of the lamp 120 does not stop.

In addition, the control IC 171 uses the signals input from the first and second sensing circuits 173a and 173b to output the normal voltages of the master 130 and the slave 150, that is, the master 130. When the phase difference between the output voltage outputted from the output voltage and the output voltage outputted from the slave 150 is 180 degrees, the high tube current flows to allow the lamp 120 to be driven normally.

It can be seen that the first and second sensing circuits 173a and 173b are formed in parallel. That is, the first and second sensing circuits 173a and 173b are configured in parallel to detect an abnormal driving by operating the other one even if one of the first and second sensing circuits 173a and 173b does not operate. For sake.

The first and second sensing circuits 173a and 173b sense voltages output from the master 130 and the slave 150 to detect abnormal operation and supply the sensed signals to the control IC 171. . That is, the first and second sensing circuits 173a and 173b control the output signal detecting an abnormal state in which phases of voltages output from the master 130 and the slave 150 overlap and a normal state in which phases do not overlap. It can be seen that the IC 171 is supplied.

As described above, the inverter according to an embodiment of the present invention detects the voltage waveform of the output voltage of the master (master) and the slave (slave) to supply the detected signal to the control IC (171), the control The IC 171 may realize stable driving of the backlight unit by adjusting the tube current of the lamp 120 according to the sensed signal.

In addition, according to the present invention, the operation of the lamp 120 is not stopped during the test or the body contact, and the tube current is controlled to flow such that the operation is low, thereby improving reliability compared to the conventional protection circuit. .

3 is a view illustrating in detail the sensing circuit of FIG. 2.

As shown in FIGS. 2 and 3, the first and second sensing circuits 173a and 193b of the present invention each have two input stages (master, slave) to which output voltages of a master and a slave are input. ), A power supply voltage charged by the first and second comparators 201 and 205 for comparing the signals input from the input terminals (master and slave) and the first and second comparators 201 and 205. The first and second latch units 203 and 207 for supplying (Vdd1 and Vdd2) and the output terminals S1 and S2 are configured.

The first comparator 201 of the first sensing circuit 173a is turned on or off according to a "high" or "low" signal input from an input terminal (master, slave). Q1 and Q2 and resistors R1, R2, R3 and R4.

The first switch Q1 may be turned on (PNP type bipolar transistor) by a “high” signal input from a master input terminal. Here, the first switch Q1 may be made of an NPN type bipolar transistor according to the circuit configuration.

The second switch Q2 may be turned on (NMOS transistor) according to a "high" signal input from a slave input terminal. Here, the second switch Q2 may be formed of a PMOS transistor according to the circuit configuration.

The first latch unit 203 of the first sensing circuit 173a includes a third switch Q3, a power supply voltage Vdd1, capacitors C1 and C2, and resistors R5 and R6.

The third switch Q3 may be turned on (NMOS transistor) by a "high" signal determined by the first comparator 201. Here, the third switch Q3 may be formed of a PMOS transistor according to the circuit configuration.

The output terminals S1 and S2 are provided with first rectifying units D1 and D2 for preventing reverse current and rectifying current.

The second comparator 205 of the second sensing circuit 173b is turned on or turned off according to the "high" or "low" signal input from the master (slave). Switches Q4 and Q5 and resistors R7, R8, R9 and R10.

The fourth switch Q4 may be turned on (PNP type bipolar transistor) by a “high” signal input from a slave input terminal. Here, the fourth switch Q4 may be made of an NPN type bipolar transistor according to the circuit configuration.

The fifth switch Q5 may be turned on (NMOS transistor) according to a “high” signal input from a master input terminal. Here, the fifth switch Q5 may be formed of a PMOS transistor according to the circuit configuration.

The second latch unit 207 of the second sensing circuit 173b includes a sixth switch Q6, a power supply voltage Vdd2, capacitors C3 and C4, and resistors R11 and R12.

The sixth switch Q6 may be turned on (NMOS transistor) by a “high” signal determined by the second comparator 205. Here, the sixth switch Q6 may be formed of a PMOS transistor according to the circuit configuration.

The output terminals S1 and S2 are provided with second rectifying units D3 and D4 for preventing reverse current and rectifying current.

An operation of the first and second sensing circuits 173a and 173b having the above structure will be described by way of example.

The case in which the voltage waveforms output from the master and the slave are both "high" signals, that is, an abnormal state will be described.

First, in the first sensing circuit 173a, "high" signals are input to input terminals (master and slave), respectively.

The first and second switches Q1 and Q2 of the first comparator 201 are both turned on in response to a "high" signal input from an input terminal (master, slave).

When the first and second switches Q1 and Q2 are turned on, the input node of the third switch Q3 is grounded with the ground voltage GND and turned off. That is, the power supply voltage Vdd1 is supplied to the output node N1 of the third switch Q3, and a "high" signal is output to the output terminals S1 and S2.

In the second sensing circuit 173b, the fourth and fifth switches Q4 and Q5 are all turned on according to the "high" signal input from the input terminals (master and slave).

When both the fourth and fifth switches Q4 and Q5 are turned on, the input node of the sixth switch Q6 is grounded with the ground voltage GND and turned off. That is, the power supply voltage Vdd2 is supplied to the output node N2 of the sixth switch Q6, and a "high" signal is output to the output terminals S1 and S2.

Accordingly, in the present invention, when the abnormal state in which the phases overlap, that is, the voltage waveforms output from the master and the slave are both "high", the first and second sensing circuits 173a and 173b are output stages S1. , S2) is outputted. The control IC 171 may be configured such that a low tube current flows through the lamp 120 such that driving is not stopped in response to the "high" signals input from the first and second sensing circuits 173a and 173b. ) And the slave (slave).

The case where the voltage waveforms output from the master and the slave are the "high" and "low" signals, that is, the case of the normal state will be described.

A "high" signal is input from the master to an input terminal of the first sensing circuit 173a, and a "low" signal from a slave is input to the input terminal of the first sensing circuit 173a. ), The first switch Q1 of the first comparator 201 is turned on by the "high" signal input from the input master, and the second switch Q2 is turned off from the input slave. It is turned off by the input "low" signal.

The first comparator 201 is short-circuited with the second latch part 203 as the second switch Q2 is turned off. As a result, the "high" signal of the power supply voltage Vdd1 is input to the input node of the third switch Q3, and the third switch Q3 is turned on.

When the third switch Q3 is turned on, the output node N1 of the third switch Q3 is grounded with the base voltage GND to output a "low" signal to the output terminals S1 and S2.

The second sensing circuit 173b may be operated in the same manner as the first sensing circuit 173a described above to output a "low" signal to the output terminals S1 and S2.

As described above, the first and second sensing circuits 173a and 173b transmit a "low" signal to the control IC 171 when the voltage waveforms input from the master and the slave are inverted with each other. The control IC 171 controls the master and the slave so that the lamp 120 can be normally driven in response to the input "low" signal.

As described above, the inverter according to an embodiment of the present invention detects the voltage waveform of the output voltage of the master (master) and the slave (slave) to supply the detected signal to the control IC (171), the control The IC 171 may control the master and the slave according to the sensed signal to adjust the tube current of the lamp 120 to realize stable driving of the backlight unit.

In addition, according to the present invention, the operation of the lamp 120 is not stopped during the test or the body contact, and the tube current is controlled to flow such that the operation is low, thereby improving reliability compared to the conventional protection circuit. .

As described above, the present invention detects the voltage waveform of the output voltage of the master and the slave (slave) to supply the detected signal to the control IC, the control IC according to the detected signal (master) And by controlling the slave (slave) to adjust the tube current of the lamp, there is an effect that can realize the driving of the stable backlight unit.

In addition, the present invention by controlling the tube current so that the operation of the lamp does not stop at the time of testing or body contact flows, thereby improving the reliability compared to the conventional protection circuit accordingly. .

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present 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 (7)

In the inverter comprising a master driver and a slave driver for applying a high voltage of the inverted phase to both ends of the lamp, A detector for detecting an abnormality of the inverter by comparing the voltages output from the master driver and the slave driver; And a control IC controlling the tube current of the lamp in response to the sensed signal supplied from the detector. The method of claim 1, And the control IC is a two-channel IC capable of controlling the master driver and the slave driver, respectively. The method of claim 1, And the sensing unit comprises a first and a second sensing circuit formed in parallel. The method of claim 3, wherein The detector may include an input terminal to which voltages output from the master driver and the slave driver are respectively input; A comparator for comparing voltages input from the master driver and the slave driver; A latch unit supplying a power voltage charged by the comparison unit; And And two output terminals output from the latch unit. The method of claim 4, wherein And a rectifier is provided at the output terminal. The method of claim 4, wherein The comparison unit includes a first switch switched according to a voltage input from a master driver, and a second switch switched according to a voltage input from the slave driver. The method of claim 4, wherein And the latch unit includes a third switch switched according to a signal input from the comparator.

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