KR100860434B1 - Driving device and driving method of fluorescent lamp - Google Patents

Abstract

At least two electrodes for applying a discharge voltage to the fluorescent lamp, a first voltage applying unit for applying a voltage of V1 to the fluorescent lamp, and applying a voltage of V2 to the fluorescent lamp independently of the voltage of V1 And a second voltage applying unit, wherein the voltage of V2 is applied only in a section in which a discharge current is generated in the fluorescent lamp. The method of driving a fluorescent lamp may include applying a voltage V2 to the fluorescent lamp in a pulse form while applying a voltage V2 such that a peak voltage equal to or greater than the discharge sustaining voltage is generated only in a section in which a discharge current is generated. to provide. According to the present invention, the efficiency of the fluorescent lamp can be increased by lowering the reactive voltage in driving the fluorescent lamp, and the discharge current can be increased by increasing the peak voltage, thereby improving the brightness of the fluorescent lamp.

Description

DRIVING UNIT AND DRIVING MEHTOD FOR FLUORESCENT LAMP}

1 is a perspective view showing an example of a fluorescent lamp.

2 is a schematic diagram showing an equivalent circuit of a fluorescent lamp.

3 is a circuit diagram of a driving device for implementing a pulse voltage.

4 is a graph showing a voltage waveform implementing pulse voltage by switch control.

5 is a graph showing a voltage of a pulse waveform applied to a fluorescent lamp.

6 is a graph showing the voltage of the pulse waveform and the current generated in the fluorescent lamp.

7 is a circuit diagram of a drive device according to the present invention.

8 is a graph showing a voltage waveform according to the fluorescent lamp composition method of the present invention.

9 is a perspective view showing a flat surface light source device.

10 is a cross-sectional view taken along the line Y-Y 'of FIG.

FIG. 11 is a cross-sectional view of an electrode unit applied to the surface light source device of FIG. 9; FIG.

The present invention relates to a driving device and a driving method of a fluorescent lamp, and proposes a driving device and a driving method for applying a pulse type voltage including a peak voltage.

The liquid crystal display displays an image by using electrical and optical characteristics of the liquid crystal. Since the liquid crystal part of the liquid crystal display is a light receiving element that does not generate light by itself, it separately requires a rear light source, that is, a backlight.

Light supplied from the rear light source sequentially passes through the pixel electrode, the liquid crystal, and the common electrode of the liquid crystal display. In this case, the display quality of the image passing through the liquid crystal largely depends on the luminance and luminance uniformity of the rear light source. In general, the higher the luminance and the uniformity of the luminance, the better the display quality.

Conventionally, a rear light source of a liquid crystal display device has been mainly used a cold cathode fluorescent lamp (CCFL) or a light emitting diode (LED). Cold cathode fluorescent lamp has the advantage of high brightness, long life, and very low heat generation compared to incandescent lamps. On the other hand, the light emitting diode has a high power consumption, but has an advantage of excellent brightness. However, cold cathode fluorescent lamps or light emitting diodes have poor luminance uniformity. Therefore, existing back light sources require optical members such as a light guide panel (LGP), a diffusion member, a prism sheet, and the like to increase luminance uniformity. As a result, the liquid crystal display has a problem in that the volume and weight of the optical member are greatly increased.

As an example of a backlight discharge lamp of a liquid crystal display device, a flat fluorescent lamp (FFL) in the form of a flat plate has been proposed. Referring to FIG. 1, an example of a surface light source device 100 having a plurality of discharge channels is illustrated. The surface light source device 100 includes a light source body 110 and electrode units 160 provided on outer surfaces of both edges of the light source body 110.

The light source body 110 includes a first substrate and a second substrate disposed to face each other at a predetermined interval. A plurality of partition walls 140 are disposed between the first substrate and the second substrate to divide the space between the first substrate and the second substrate into a plurality of discharge channels 120. A sealing member 130 is disposed between the edges of the first substrate and the second substrate to isolate the discharge channels 120 from the outside. Discharge gas is injected into the discharge space 150 inside the discharge channel 120. In order to drive the surface light source device, a pair of electrode units 160 having a band shape are formed on both surfaces of the light source body.

As the liquid crystal display device becomes larger, the demand for such a surface light source device used as a backlight is rapidly increasing, and a large area and a thinning of the surface light source device are continuously required.

In particular, in order to reduce power consumption and improve image quality of LCDs, there is an urgent need for improving luminance and increasing efficiency of fluorescent lamps such as surface light source devices. Such technical requirements require further improvement as the size of surface light source devices increases. It is becoming.

It is therefore an object of the present invention to reduce power consumption and improve luminance of fluorescent lamps, such as surface light source devices.

Further, another object of the present invention is to provide a driving device and a driving method suitable for a large area surface light source device.

The present invention provides at least two electrodes for applying a discharge voltage to a fluorescent lamp, a first voltage applying unit for applying a voltage of V1 to the fluorescent lamp, and a voltage of V2 independent of the voltage of V1 to the fluorescent lamp. It includes a second voltage applying unit for applying a voltage, the voltage of the V2 provides a driving device of the fluorescent lamp, characterized in that is applied only in the section in which the discharge current is generated in the fluorescent lamp.

In order to increase the peak voltage to improve the brightness while reducing the reactive power to increase the efficiency, it is preferable that the voltage of V1 is equal to or greater than the minimum discharge sustain voltage, and the sum of the voltage of V1 and V2 is equal to or greater than the discharge sustain voltage.

The present invention includes a first switch unit for controlling the application of the V1 voltage to the fluorescent lamp and a second switch unit for controlling the application of the V2 voltage to the fluorescent lamp.

The voltages V1 and V2 are applied in the form of pulses such that (+) and (-) are alternately repeated to the fluorescent lamp, and this pulse waveform is easy to control the dimming range of the fluorescent lamp.

In the present invention, the fluorescent lamp is more effective for a large area fluorescent lamp in the form of a surface light source as well as a conventional tubular lamp, as shown in FIG. As described above, an embodiment in which electrodes are disposed on both sides of a fully flat light source body is also possible.

The present invention also provides a driving method for applying a discharge voltage to a fluorescent lamp, while applying a voltage V1 corresponding to the minimum discharge sustain voltage in the form of a pulse, so that a peak voltage equal to or greater than the discharge sustain voltage is generated only in a section in which the discharge current is generated. Provided is a driving method of a fluorescent lamp, characterized by applying a voltage.

The voltage V1 may be applied to the fluorescent lamp in the form of a pulse in which a positive voltage and a negative voltage are repeated while being controlled by at least four switches, and the voltage V2 is controlled by at least two switches. The negative voltage and the positive voltage may be applied to the lamp in the form of repeated pulses.

The voltage V1 and voltage V2 are preferably set to voltages of opposite polarities with respect to the fluorescent lamp.

The present invention relates to a driving apparatus and a driving method of a fluorescent lamp, and proposes a driving unit for applying a pulse type voltage including a peak voltage and implementing the same.

Fluorescent lamps with discharge space and emitting light by dielectric barrier discharge can be regarded as a kind of capacitor from the circuit point of view. Electrodes are disposed at both ends of the fluorescent lamp, and as shown in FIG. 2, a discharge voltage in the form of a sine wave or a pulse wave is applied to the X electrode and the Y electrode which are disposed to face each other in the fluorescent lamp Cp. The X electrode and the Y electrode may be, for example, strip-shaped electrode portions 160 disposed opposite to the edges of the surface light source device shown in FIG. 1, and disposed on both sides of the flat light source body as described below. It may be a surface electrode.

In order to apply, for example, a square wave pulse voltage to a fluorescent lamp, mutually alternating voltages may be applied to two opposite electrodes. For this purpose, a circuit as shown in FIG. 3 may be considered.

Vx and Vy voltages are applied to the X and Y electrodes based on the fluorescent lamp, respectively, and the voltages applied to the fluorescent lamp are controlled by a total of four switches SW1, SW2, SW3, and SW4. The on / off operation of the switch may be controlled to apply a pulse waveform voltage to the fluorescent lamp. For example, referring to FIG. 4, a discharge voltage is applied to the X electrode and the Y electrode according to the switch control. As shown. SW1 and SW2 are selectively turned on / off, and SW3 and SW4 are preferably selectively turned on / off.

First, SW1 and SW3 are turned on to apply a Vx corresponding to the discharge sustain voltage (Vs) to the X electrode to discharge the fluorescent lamp, then SW2 is turned on (in this case SW1 is turned off) and SW4 is turned on at the same time. (In this case, SW3 is off.) Do not apply discharge voltage. Next, SW2 and SW3 are turned on to apply a Vy corresponding to the discharge sustain voltage Vs to the Y electrode to discharge the fluorescent lamp, and then SW2 and SW4 are turned on to block the discharge voltage.

As described above, the discharge voltage in the form of pulse can be applied to the fluorescent lamp by controlling four switches, and the positive voltage and the negative voltage are repeated as shown in FIG. 5. Pulse form.

However, the voltage waveform actually applied to the fluorescent lamp has a pulse rising time and a pulse falling time, not a perfect square wave. In addition, the actual discharge current If only exists in the initial stage even in the period where the discharge sustain voltage Vs is applied. Referring to FIG. 6, the displacement current Id is present in the pulse rising section t1 and the pulse falling section t3, respectively, and the discharge current If is generated only at the beginning of the actual section t2 to which the discharge sustain voltage is applied. You can see it exists. The brightness of the fluorescent lamp is correlated with the discharge current, and the time for which the voltage is applied does not significantly affect the increase in brightness. Therefore, the voltage applied in the remaining section t 'in which the discharge current does not flow actually corresponds to an invalid voltage in which only the voltage exists without the current, which is a factor of increasing power consumption without contributing to the discharge, and consequently the fluorescence The driving efficiency of the lamp is reduced.

In order to solve the above disadvantages, the present invention generates a high discharge current during the discharge of the fluorescent lamp by increasing the peak voltage after the pulse rising period in the discharge voltage of the pulse waveform, and improves the efficiency by lowering the driving voltage after the discharge current is generated. We propose a driving device that can.

Thus, the lowering of the reactive voltage not only increases the efficiency of the fluorescent lamp, but also increases the peak voltage to increase the discharge current, thereby achieving the dual effect of improving the brightness of the fluorescent lamp.

It is preferable to configure the driving device according to the present invention in a circuit of a different type than the inverter circuit, because the inverter requires a transformer, so that it is difficult to control the voltage with a pulse waveform and the circuit configuration is expensive.

The drive device of the preferred embodiment proposed in the present invention can be explained by the schematic circuit diagram of FIG. 7. In addition to the discharge voltage V1, a separate discharge voltage V2 is applied to the fluorescent lamp Cp in the pulse waveform implementation circuit shown in FIG. 3, and additionally, switches SW5 and SW6 are included to control the voltage V2. . The voltages V1 and V2 have opposite polarities so that the actual voltage applied to the fluorescent lamp is V1 + V2.

The additionally included switches SW5 and SW6 serve to control peak voltages applied to both ends of the fluorescent lamp by combining On / Off control with switches SW1, SW2, SW3, and SW4 for realizing a conventional pulse waveform. do. As a result, a basic pulse waveform is generated by the first voltage applying unit and the first switch units SW1, SW2, SW3, and SW4 that generate the V1 voltage, and in connection with the switch on / off operation of the first voltage applying unit. The second voltage applying unit generating the voltage and the second switch units SW5 and SW6 generate the peak voltage. The voltages V1 and V2 may be designed to be direct voltages, respectively.

The voltage waveform applied to the fluorescent lamp by the drive device having the circuit element of FIG. 7 will be described with reference to FIG. 8.

The Vxy voltage is applied to the fluorescent lamp by the combination of the Vx voltage applied to the X electrode and the Vy voltage applied to the Y electrode, and the overall driving voltage is a pulse waveform in which a positive voltage and a negative voltage are repeated. The form has in part a peak voltage of V1 + V2.

Referring to the section-specific driving method, first, in the section A, SW1 and SW6 are turned on so that the voltage V1 is applied to the X electrode and the voltage -V2 is applied to the Y electrode. The potential difference across the fluorescent lamp is Vx-Vy. As a result, a peak voltage of V1 + V2 is applied to the fluorescent lamp to discharge the lamp. SW6 is turned on until the lamp starts discharging and the discharge current reaches 0A. Since the peak voltage is applied, the discharge current generated in the fluorescent lamp increases, which may lead to an improvement in luminance.

Next, in section B, after the discharge current becomes 0 A in section A, SW6 is turned off and SW4 is turned on so that only V1 voltage is applied to both ends of the fluorescent lamp. The discharge is maintained even when only the voltage V1 is applied due to the wall voltage inside the fluorescent lamp. The smaller the voltage V1 is, the more the reactive voltage can be reduced within the limit of the discharge. Therefore, the power consumption of the fluorescent lamp can be reduced and the efficiency can be increased.

In section C, SW1 is off and SW2 and SW4 are on. No voltage is applied across the fluorescent lamp.

In section D, SW3 and SW5 are turned on to apply the voltage -V2 to the X electrode and the voltage V1 to the Y electrode. The potential difference across the lamp is Vx-Vy, and a peak voltage of-(V1 + V2) is applied to the lamp to discharge the lamp. Compared with the A section, the potential difference between the two ends of the lamp is 180 degrees out of phase with the same operating characteristics.

SW5 maintains the ON state while the lamp starts discharging and generates a discharge current. When the discharge current reaches 0 A (E section), SW5 is turned off and SW2 is turned on, so that only V1 voltage is applied across the lamp. In this case, the discharge is maintained even when only the voltage V1 is applied due to the wall voltage inside the lamp.

In section F, like in section C, SW1 is turned off and SW2 and SW4 are turned on. No voltage is applied across the lamp.

As described above, the peak voltage is applied to the pulsed driving voltage as well as the discharge start, and the driving voltage is lowered at the time when the discharge current becomes 0, thereby achieving the effect of improving the luminance and increasing the efficiency.

For example, the present invention can be effectively applied to various types of fluorescent lamps as well as fluorescent lamps in the form of surface light sources having a plurality of discharge channels as shown in FIG. 1. 9 shows a fully planar surface light source device 200 without a discharge channel. The surface light source device 200 includes a flat plate type first substrate 210 and a flat plate type second substrate 220 having the same shape as a light source body, and there is a closed discharge space having a fine vertical thickness therein. The first substrate 210 and the second substrate 220 may be maintained at predetermined intervals, and side spacers 230 may be inserted into edges to form a sealed internal discharge space 240 as shown in FIG. 10. Alternatively, the edges of both substrates may be directly fused by heating to form a sealed internal discharge space.

A surface electrode at least partially covering the surface may be formed on one surface of the surface light source device (for example, the surface 210 ′ of the first substrate). For example, as illustrated in FIG. 11, surface electrodes 260a and 260b may be formed on outer surfaces of the first substrate 210 and the second substrate 220. The surface electrodes 260a and 260b may apply high voltages to the discharge gas injected into the discharge space by opposing each other with a very fine height of the discharge space. Discharge gas may be injected to cause discharge. The surface electrode may be formed, for example, in a mesh form or a stripe pattern.

Supplying a square wave voltage from the driving device according to the present invention to each of the surface electrodes can improve the luminance and increase the efficiency. Pulse width modulation (PWM) enables dimming of the surface light source device. It is easy to provide a liquid crystal display device employing a surface light source device to provide a variety of brightness-adjusted image.

The present invention has been exemplarily described through the preferred embodiments, but the present invention is not limited to such specific embodiments, and various forms within the scope of the technical idea presented in the present invention, specifically, the claims. May be modified, changed, or improved.

As described above, according to the present invention, the efficiency of the fluorescent lamp may be increased by lowering the reactive voltage in driving the fluorescent lamp, and the discharge current may be increased by increasing the peak voltage to improve the brightness of the fluorescent lamp. . Since the driving device implements a pulse waveform by simple switch control of the first voltage applying unit and the second voltage applying unit, fewer circuit elements are required to reduce the overall volume of the driving device and contribute to slimming of the backlight.

Claims (9)

At least two electrodes for applying a discharge voltage to the fluorescent lamp, A first voltage applying unit applying a voltage of V1 to the fluorescent lamp; A second voltage applying unit configured to apply a voltage of V2 to the fluorescent lamp independently of the voltage of V1, The voltage of V2 is characterized in that it is applied only in the section in which the discharge current is generated in the fluorescent lamp Driving device of fluorescent lamps. The apparatus of claim 1, wherein the voltage of V1 is equal to or greater than the minimum discharge sustain voltage, and the sum of the voltage of V1 and V2 is equal to or greater than the discharge sustain voltage. The apparatus of claim 1, further comprising: a first switch unit controlling the application of the V1 voltage to the fluorescent lamp and a second switch unit controlling the application of the V2 voltage to the fluorescent lamp. The driving device of the fluorescent lamp according to claim 1, wherein V1 and V2 voltages are applied to the fluorescent lamp alternately with the fluorescent lamp. The apparatus of claim 1, wherein the fluorescent lamp includes a flat light source body, and the electrodes are disposed opposite to each other at both ends of the light source body. The apparatus of claim 1, wherein the fluorescent lamp includes a flat light source body, and the electrodes are disposed on both sides of the light source body. A driving method for applying a discharge voltage to a fluorescent lamp, While applying the voltage of V1 or more above the minimum discharge sustain voltage in the form of a pulse, the voltage V2 is applied so that the peak voltage or more above the discharge sustain voltage is generated only in a section where the discharge current is generated. How to drive a fluorescent lamp. The method of claim 7, wherein the voltage V1 is controlled by at least four switches and is applied to the fluorescent lamp in the form of a pulse in which a positive voltage and a negative voltage are repeated. The method of claim 7, wherein the voltage V2 is controlled by at least two switches and is applied to the fluorescent lamp in the form of a pulse in which a negative voltage and a positive voltage are repeated.

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