KR20060024052A - Inverter and inverting method for flat fluorescent lamp, backlight assembly and liquid crystal display having the same - Google Patents

Abstract

Inverters and inverting methods are disclosed that can effectively drive large lamps. The first and second drivers amplify the first and second pulse width modulated signals, respectively, and perform switching operations using the amplified signals to generate first and second AC signals. The first and second transformers receive the first and second AC signals, respectively, and convert the first and second transformer signals to output first and second converted signals having a 180 degree phase difference. The feedback unit senses a current at the secondary side of the first transformer and the second transformer to generate the feedback signal and feed it back to the controller. Therefore, a large sized lamp can be easily driven, and the current of the lamp can be effectively controlled.

Description

Inverter for flat fluorescent lamp and inverting method thereof, backlight assembly and liquid crystal display device having same.             

1 is a cross-sectional view of a flat fluorescent lamp according to the prior art.

2 is a block diagram of a backlight assembly including an inverter according to an embodiment of the present invention.

3 is a circuit diagram of an example of the controller illustrated in FIG. 2.

4 is a circuit diagram of an example of the first and second drivers illustrated in FIG. 2.

FIG. 5 is a circuit diagram of an example of the feedback unit illustrated in FIG. 2.

6 is an exploded perspective view illustrating a liquid crystal display according to the present invention.

Explanation of symbols on the main parts of the drawings

210: DC-DC conversion / oscillator 220: control unit

230: first driving unit 240: second driving unit

250: first transformer 260: second transformer

270: feedback unit 280: flat fluorescent lamp

The present invention relates to a backlight assembly technology of a liquid crystal display device, and more particularly, to an inverter for a flat fluorescent lamp and an inverting method using the same.

In general, unlike a display device having a self-luminous capability such as a cathode ray tube, a liquid crystal display such as a liquid crystal display (LCD) does not have a self-luminous capability. Therefore, a liquid crystal display device is usually provided with a lighting device having a surface shape, for example a back light, on the back of the liquid crystal element. This backlight includes a lamp for emitting white light, and the white light emitted from the surface light source device is colored and displayed by selective driving of the liquid crystal element having a color filter. Therefore, the backlight is mainly used to project light from the right side of the liquid crystal element or to form a planar light source using a light guide plate made of plastic (for example, acrylic plate).

Inverter means a device for controlling the discharge of the lamp. In order to discharge the lamp, a high voltage must first be applied to the lamp. As a result, the lamp is turned on. After lighting, a constant voltage must be applied to the lamp. This function must be performed by the inverter to operate the lamp properly.

Cold Cathode Fluorescent Lamp (CCFL) among the lamps used for the backlight is a cylindrical shape, and the backlight using it is operated by placing several cold cathode fluorescent lamps on the back of the liquid crystal panel to make a surface light source. . In the case of using a cold cathode fluorescent lamp, a plurality of tubular lamps were connected to a plurality of inverters and inverted. Therefore, a high voltage of several hundred V is applied to a single tubular lamp by using a single inverter, and as a result, a low current of several mA flows through the lamp, so there is no shortage of power in terms of the inverter and it is easy to control the current. .

Unlike cold cathode fluorescent lamps, flat fluorescent lamps (Flat Fluorescent Lamp) is a method of placing a discharge gas and a phosphor between the two sheets of glass, causing a discharge to make a surface light source.

As shown in FIG. 1, the flat fluorescent lamp 100 using two sheets of glass is a back substrate 110 and a front substrate 120 bonded to the back substrate 110 via a sealant 130. The discharge space is formed. In addition, a phosphor layer 160 is formed on a lower surface of the front substrate 120, and a dielectric layer in which a plurality of discharge electrodes 140 having a predetermined pattern is embedded on the upper surface of the back substrate corresponding to the phosphor layer 160. 150 is formed, and the discharge space is filled with a discharge gas made of neon (Ne), argon (Ar) and the like. As the flat panel fluorescent lamp 100 is powered by the discharge electrode 140, the phosphor layer 160 is excited by ultraviolet rays generated by the discharge between the discharge electrodes 140, and thus the surface of the flat fluorescent lamp 100 emits an image of the liquid crystal display. do.

Flat fluorescent lamps have to apply a high voltage of several hundred V to a single lamp to maintain a current of several tens of mA to more than one hundred mA, which may cause a problem of stable AC power supply, and it is not easy to control the current. Therefore, there is a need for a new inverter capable of supplying a stable and highly efficient AC power supply to a flat fluorescent lamp.

An object of the present invention for solving the above problems is to provide a stable high-voltage high current to a large single flat fluorescent lamp, and to provide an inverter for a flat fluorescent lamp to ensure a stable discharge of high efficiency. .

Another object of the present invention is to provide a method for inverting a flat fluorescent lamp to supply a stable high voltage high current to a large single flat fluorescent lamp and to control the discharge of the flat fluorescent lamp with high efficiency.

Still another object of the present invention is to provide a backlight assembly having the inverter for a flat fluorescent lamp described above.

It is still another object of the present invention to provide a liquid crystal display device having the above inverter for a flat fluorescent lamp.

In order to achieve the object of the present invention as described above, an inverter for a flat fluorescent lamp receives a DC power supply from a DC-DC converter / oscillator, converts it into a DC signal of a desired level, and oscillates a DC signal to output an oscillation signal. The control unit controls the pulse width of the oscillation signal by using the oscillation signal and the feedback signal to generate the first and second pulse width modulation signals.                     

The first and second drivers amplify the first and second pulse width modulated signals, respectively, and perform switching operations using the amplified signals to generate first and second AC signals. These first and second alternating current signals correspond to the primary side signals of the transformer.

The first and second transformers receive the first and second AC signals, respectively, and convert the first and second transformer signals to output the first and second converted signals. The first and second converted signals correspond to the secondary signal of the transformer and may be high voltages of several hundred V or more.

The feedback unit detects a current at the secondary side of the first transformer and the second transformer, generates a feedback signal, and feeds it back to the controller. It is easy to control the current by sensing and feeding back the current on the secondary side.

Inverting method of a flat plate fluorescent lamp to achieve another object of the present invention, the step of converting the DC power source into a DC signal of the desired level, and generating the oscillation signal by oscillating the DC signal, by using the oscillation signal and the feedback signal Generating the first and second pulse width modulated signals by controlling the pulse width of the oscillation signal, amplifying the first and second pulse width modulated signals, and performing a switching operation using the amplified signals to perform the first and second pulse signals. Generating an AC signal, converting the first and second AC signals to output the first and second converted signals, and detecting the first and second converted signals to generate a feedback signal; . In this case, the generating of the first and second AC signals may operate in a half ground method. The half ground scheme is well known to those skilled in the art and is not described herein again. Generating the feedback signal may operate in a floating ground scheme. Floating grounding schemes are also well known to those of ordinary skill in the art.

The backlight assembly for solving the another object of the present invention consists of an inverter for a flat panel fluorescent lamp that converts the DC power input from the outside into an alternating current and a flat fluorescent lamp which is a large surface light source to generate light in response to the converted alternating current It includes a light emitting unit.

At this time, the inverter for flat fluorescent lamp receives DC power, converts it into DC signal of the desired level, and converts the oscillation signal by using the DC-DC conversion / oscillation unit which oscillates the DC signal and outputs the oscillation signal. A control unit for controlling the pulse width to generate the first and second pulse width modulated signals, amplifying the first and second pulse width modulated signals, respectively, and performing a switching operation using the amplified signals to perform the first and second alternating current signals. First and second drivers for generating the first and second, respectively, the first and second AC signals of the first and second transformers and the first and second transformers and the second and second transformers for outputting the first and second converted signals It includes a feedback unit for generating a feedback signal by sensing the current from the vehicle side.

According to another aspect of the present invention, a liquid crystal display device includes a flat panel fluorescent lamp inverter for converting a DC power input from the outside into an alternating current and an optical control for improving the brightness of light provided from the flat panel fluorescent lamp inverter. And a display assembly positioned on an upper surface of the backlight assembly having a portion and displaying an image using light provided from the light emitting portion through the light adjusting portion.

At this time, the inverter for flat fluorescent lamp receives DC power, converts it into DC signal of the desired level, and converts the oscillation signal by using the DC-DC conversion / oscillation unit which oscillates the DC signal and outputs the oscillation signal. A control unit for controlling the pulse width to generate the first and second pulse width modulated signals, amplifying the first and second pulse width modulated signals, respectively, and performing a switching operation using the amplified signals to perform the first and second alternating current signals. First and second drivers for generating the first and second, respectively, the first and second AC signals of the first and second transformers and the first and second transformers and the second and second transformers for outputting the first and second converted signals It includes a feedback unit for generating a feedback signal by sensing the current from the vehicle side.

Therefore, it is easy to drive a large lamp by using the high voltage output of the reverse phase and sensing the current through the secondary side, effectively controlling the current of the lamp, and improving the discharge efficiency of the lamp.

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

2 is a block diagram of a backlight assembly including an inverter according to an embodiment of the present invention. The block diagram shown in Figure 2 is shown to be simplified in order to effectively explain the technical idea of the present invention.

2, an inverter according to an embodiment of the present invention includes a DC-DC converter / oscillator 210, a controller 220, a first driver 230, a second driver 240, and a first transformer 250. ), A second transformer 260 and a feedback unit 270.

The DC-DC converter / oscillator 210 converts the input DC power into a DC signal having a desired level, and performs an oscillation operation using the DC signal to generate an AC signal and a square wave oscillation signal PULSE.

The controller 220 outputs an oscillation signal PULSE output from the DC-DC converter / oscillator 210, a PWM dimming signal DIMM input externally to adjust the brightness of the screen, and a feedback output from the feedback unit 270. In response to the signal FED, pulse width modulation of the oscillation signal PULSE is performed to generate first and second pulse width modulation signals PWM1 and PWM2 having a controlled pulse width.

The first and second drivers 230 and 240 respectively amplify the first pulse width modulated signal and the second pulse width modulated signal, and perform a switching operation using the first pulse width modulated signal and the first and second AC signals. The first and second AC signals, which are output signals of the first and second drivers 230 and 240, have a phase difference of 180 degrees to allow the inverter to operate in a half ground manner.

The first driver 230 is subdivided into an amplifier 231 and a switch 233. The amplifier 231 amplifies the input first pulse width modulated signal. By the operation of the amplifier 231, the first pulse width modulated signal is amplified to a degree suitable for switching. The switching unit 233 generates a first AC signal by performing a switching operation using the output signal of the amplifier 231.

The second driver 240 is subdivided into an amplifier 241 and a switch 243. The amplifier 241 amplifies the input second pulse width modulated signal. By the operation of the amplifier 241, the second pulse width modulated signal is amplified to an extent suitable for switching. The switching unit 243 performs a switching operation using the output signal of the amplifier 241 to generate a second AC signal. In this case, the switching unit 233 of the first driver 230 and the switching unit 243 of the second driver 240 preferably include a full bridge circuit. The full bridge circuit can be easily implemented by those skilled in the art.

The first transformer 250 converts the first AC signal to generate a first high frequency converted signal. In this case, the first converted signal may be a high voltage of several hundred V or more.

Similarly, the second transformer 260 converts the second AC signal to generate a high frequency second converted signal. In this case, the second converted signal may be a high voltage of several hundred volts or more. Preferably, the first converted signal and the second converted signal have a phase difference of 180 degrees.

One output terminal of each of the first and second transformers 250 and 260 is connected to the flat fluorescent lamp 280 to drive the flat fluorescent lamp. The other output terminals of the first and second transformers 250 and 260 are connected to the feedback unit 270.

The feedback unit 270 generates a feedback signal FED by sensing the currents of the first and second transformers 250 and 260 on the secondary side. At this time, the feedback unit 270 is preferably a floating grounding method having a common grounding terminal. The feedback signal FED is again input to the controller 220 so that the controller 220 can control the pulse width using the feedback signal FED.

The inverter and the flat fluorescent lamp 280 described above constitute a backlight assembly. The inverter shown in FIG. 2 operates in a half ground floating grounding manner, senses current on the secondary side, and stably provides a high voltage and a relatively large current required to drive the flat fluorescent lamp 280.

3 is a circuit diagram of an example of the controller illustrated in FIG. 2. Figure 3 shows that it is simplified in order to effectively explain the technical idea of the present invention.

The control unit shown in FIG. 3 includes seven resistors R1, R2, R3, R4, R5, R6 and R7, three capacitors C1, C2 and C3, two switches SW1 and SW2 and a diode D1. And a BIT3105 chip 310.

The feedback signal FED and the PWM dimming signal DIMM allow the BIT3105 chip 310 to properly control current through seven resistors, three capacitors, two switches, and a diode. At this time, the two switches SW1 and SW2 change the size of the resistor by making the resistors R4 and R5 visible or invisible in the paths of the feedback signal FED and the PWM dimming signal DIMM. .

The BIT3105 chip 310 is an LCD cold cathode fluorescent lamp (CCFL) controller chip, manufactured by BITEK. The BIT3105 chip is used in cold cathode fluorescent lamp systems, notebook computers, LCD monitors, LCD TVs, and personal digital assistants (PDAs). The BIT3105 chip 310 has an operating voltage of 4.5V to 13.2V and supports built-in PWM dimming.

In the controller of FIG. 3, the BIT3105 chip 310 performs pulse width control based on a feedback signal FED and a PWM dimming signal DIMM input through seven resistors, three capacitors, two switches, and a diode. The pulse width modulated signal PWM1 and the second pulse width modulated signal PWM2 are output. At this time, the first pin input signal INN of the sawtooth type and the comparison signal CMP of the DC type are input through the BIT3105 chip 310 to correspond to the waveform corresponding to the input signal INN of a level higher than the comparison signal CMP. Pulse width modulation is performed depending on how much is done.

The pulse width modulated first and second pulse width modulation signals PWM1 and PWM2 are output through the BIT3105 chip 310 to the POUT1 and POUT2 pins of the BIT3105 chip 310, respectively.

The controller may be implemented by various methods, but may be easily implemented using an LCD controller chip as shown in FIG. 3.

4 is a circuit diagram of an example of the first and second drivers illustrated in FIG. 2. 4 shows that the components corresponding to the reference numerals shown in FIG. 2 are shown as the same components.

Referring to FIG. 4, the first driver 230 includes an amplifier 231 and a switch 233, and the second driver 240 includes an amplifier 241 and a switch 243.

The amplifiers 231 and 241 of the first driver 230 and the second driver 240 respectively input the first pulse width modulation signals PW_AH and PW_AL and the second pulse width modulation signals PW_BH and PW_BL. Amplify. By the operation of the amplifiers 231 and 241, the first and second pulse width modulated signals are amplified to a degree suitable for switching.

In FIG. 4, the amplifying units 231 and 241 of the first and second driving units 230 and 240 use IR2100 chips manufactured by International Rectifier, respectively. IR2100 chip is a driver chip that can withstand a voltage of about 500V, and detailed chip operation is performed by International Rectifier's Data sheet No. It is disclosed in detail in PD60147K. In FIG. 4, the two IR2100 chips amplify the first pulse width modulated signals PW_AH and PW_AL and the second pulse width modulated signals PW_BH and PW_BL, respectively, to generate a signal sufficient for the switching operation.

The switching units 233 and 243 of each of the first driver 230 and the second driver 240 shown in FIG. 4 are full-bridged by using signals amplified to a sufficient level for switching in the amplifiers 231 and 241. The switching generates the first and second alternating current signals O1 and O2. The two switching units 233 and 243 shown in FIG. 4 operate in a full bridge circuit. Full bridge circuits are well known to those of ordinary skill in the art and are not described herein separately. The switching operation is performed using four MOS transistors in the two switching units 233 and 243 constituting the full bridge circuit. As a result, the first and second drivers 230 and 240 illustrated in FIG. 4 receive the first and second pulse width modulated signals, respectively, and amplify and switch them to generate the first and second AC signals.

FIG. 5 is a circuit diagram of an example of a feedback circuit of the inverter shown in FIG. 2.

As shown in FIG. 5, the feedback circuit includes four resistors R1, R2, R3, and R4, four diodes D1, D2, D3, and D4, and a capacitor C1. In the feedback circuit illustrated in FIG. 5, both terminals are connected to the secondary sides of the first and second transformers, respectively, to sense the current at the secondary side and send the feedback signal to the feedback signal (FED) controller to control the current.                     

At this time, the feedback circuit operates in a floating ground scheme. Furthermore, it operates in a half-ground manner in which a high-voltage signal in a reverse phase is applied to a flat fluorescent lamp connected to an inverter. Therefore, high voltage can be effectively applied to the flat fluorescent lamp.

6 is an exploded perspective view showing a liquid crystal display device according to the present invention, particularly showing a liquid crystal display device employing a direct type backlight assembly.

Referring to FIG. 6, the direct type liquid crystal display device 900 according to the present invention includes a liquid crystal panel assembly 910 representing a screen and a direct type backlight assembly 920 that provides light to the liquid crystal panel assembly 910.

The liquid crystal panel assembly 910 is a thin film transistor (hereinafter, referred to as TFT) substrate (or array substrate) 911a and the color filter substrate 911b and the array substrate 911a and the color filter substrate 911b. It has a liquid crystal panel 911 made of a liquid crystal layer (not shown) injected into it. The data printed circuit board 915, the gate printed circuit board 914, the data side tape carrier package (hereinafter referred to as TCP) 913, and the gate side TCP 912 are provided.

On the other hand, the direct type backlight assembly 920 is a lamp unit 921 for generating a first light, a reflector 923 for reflecting the first light generated from the lamp unit 921, and diffuses the first light uniformly A light control unit 922 for emitting the second light having a one-time distribution and a bottom chassis 925 for accommodating the lamp unit 921 and the reflecting plate 923. Here, the light control unit 922 is a diffusion plate 922a, a diffusion sheet 922b sequentially disposed on the diffusion plate 922a, a low prism sheet 922c, an upper prism sheet 922d, and a protective sheet ( 922e).

The bottom chassis 925 is formed in a box shape of a rectangular parallelepiped with an open top surface. A storage space having a predetermined depth is formed inside the bottom chassis 925, and a reflecting plate 923 is disposed along an inner surface of the storing space, and a lamp unit 921 is installed above the reflecting plate 923. In addition, the bottom chassis 925 is spaced apart from the lamp unit 921 by a predetermined interval, the light control unit 922 is seated.

Here, the lamp unit 921 is connected to both ends of the flat fluorescent lamp 921a, the flat fluorescent lamp 921a, and the first and second lamp clips 921b and 921c for supplying a power voltage, and the first and second lamps. First and second power supply lines 921d and 921e supply power voltages to the clips 921b and 921c, respectively. In this case, the first and second power supply lines 921d and 921e are respectively connected to the inverter 927 for the flat fluorescent lamp generating the first and second power supply voltages.

The flat fluorescent lamp inverter 927 is an inverter described with reference to FIG. 2 and provides first and second power supply voltages to a flat fluorescent lamp as a large surface light source. The inverter 927 for a flat fluorescent lamp operates in a half ground and floating ground manner to effectively provide a high voltage, and sense current on the secondary side to facilitate current control.

On the other hand, the middle chassis 930 is disposed on the upper portion of the light control unit 922, the liquid crystal panel 911 is mounted on the stepped member of the middle chassis 930. Thereafter, a top chassis 940 is provided on the liquid crystal panel 911 so as to be opposed to the bottom chassis 925. Thereby, a direct type liquid crystal display device is completed.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

According to the present invention as described above, by sensing the current through the secondary side can react quickly and accurately even for a small change of the fluorescent lamp it is possible to stably control the output current of the drive unit. Furthermore, control of the duty ratio and the like as well as the magnitude of the current is possible. The half-ground method also allows the use of antiphase high voltage outputs. Therefore, by supplying and controlling a stable high voltage and high current to a large single lamp, the flat fluorescent lamp can be stably discharged with high efficiency.

Claims (16)

A DC-DC converter / oscillator that receives a DC power source and converts the DC signal into a desired level, and oscillates the DC signal to output an oscillation signal; A controller configured to perform pulse width control using a feedback signal and the oscillation signal to generate first and second pulse width modulated signals; First and second drivers respectively amplifying the first and second pulse width modulated signals and generating first and second AC signals by performing a switching operation using the amplified signals; First and second transformers receiving the first and second AC signals and converting the first and second AC signals to output first and second converted signals, respectively; And And a feedback unit configured to generate a feedback signal by sensing a current at a secondary side of the first transformer and the second transformer. The method of claim 1, And the first and second converted signals have a phase difference of 180 degrees, and the first and second driving units operate in a half ground manner. The method of claim 2, And said feedback unit is a floating grounding system. The method of claim 3, wherein And the first driving unit and the second driving unit include a full bridge circuit. Converting a DC power source into a DC signal having a desired level, and oscillating the DC signal to generate an oscillation signal; Generating first and second pulse width modulated signals by performing pulse width control using a feedback signal and the oscillation signal; Amplifying the first and second pulse width modulated signals, respectively, and performing a switching operation using the amplified signal to generate first and second AC signals; Converting the first and second AC signals to output first and second converted signals, respectively; And And detecting the first converted signal and the second converted signal to generate the feedback signal. The method of claim 5, wherein And the first and second converted signals have a phase difference of 180 degrees. The method of claim 6, The inverting method of the planar fluorescent lamp is an inverting method of a flat fluorescent lamp, characterized in that to operate in a half ground floating ground method. The method of claim 6, Generating the first and second alternating current signals in a full bridge manner. Inverter for flat fluorescent lamp which converts the DC power input from the outside into AC; And Comprising a planar fluorescent lamp which is a large surface light source, comprising a light emitting unit for generating light in response to the converted alternating current, The inverter for a flat fluorescent lamp, A DC-DC converter / oscillator for receiving the DC power and converting the signal into a DC signal having a desired level, and oscillating the DC signal to output an oscillation signal; A controller configured to perform pulse width control using a feedback signal and the oscillation signal to generate first and second pulse width modulated signals; First and second drivers respectively amplifying the first and second pulse width modulated signals and generating first and second AC signals by switching using the amplified signals; First and second transformers receiving the first and second AC signals and converting the first and second AC signals to output first and second converted signals, respectively; And And a feedback unit configured to generate a feedback signal by sensing a current at a secondary side of the first transformer and the second transformer. The method of claim 9, And the first and second converted signals have a phase difference of 180 degrees and the first and second drivers operate in a half ground manner. The method of claim 10, And the feedback part is a floating ground type. The method of claim 11, And the first driver and the second driver include a full bridge circuit. A flat panel fluorescent lamp inverter for converting and outputting DC power input from the outside into alternating current, a light emitting unit for generating light using alternating current provided from the flat panel fluorescent lamp inverter, and brightness of light provided from the light emitting unit A backlight assembly having a light control portion for improving; And Located on the upper surface of the light control unit, and includes a display assembly for displaying an image based on the light provided from the light emitting unit through the light control unit, The inverter for a flat fluorescent lamp, A DC-DC converter / oscillator for receiving the DC power and converting the signal into a DC signal having a desired level, and oscillating the DC signal to output an oscillation signal; A controller configured to perform pulse width control using a feedback signal and the oscillation signal to generate first and second pulse width modulated signals; First and second drivers respectively amplifying the first and second pulse width modulated signals and generating first and second AC signals by performing a switching operation using the amplified signals; First and second transformers receiving the first and second AC signals and converting the first and second AC signals to output first and second converted signals, respectively; And And a feedback unit configured to generate a feedback signal by sensing a current at a secondary side of the first transformer and the second transformer. The method of claim 13, And the first and second converted signals have a phase difference of 180 degrees, and the first and second spheres are operated in a half ground manner. The method of claim 14, And the feedback part is a floating grounding system. The method of claim 15, And the first driver and the second driver comprise a full bridge circuit.

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