KR101178833B1 - Inverter circuit, backlight device, and liquid crystal display device using the same - Google Patents

Abstract

An inverter circuit and a frequency adjusting means are provided on the drive primary side of the inverter transformer. In addition, a backlight device having the inverter circuit and a plurality of cold cathode tubes connected in parallel to the inverter transformer in the inverter circuit is provided. Furthermore, a liquid crystal display device having a backlight unit and a liquid crystal panel, a display unit having a data circuit and a gate circuit connected to the liquid crystal panel, a storage container for storing the display unit and the backlight device, and a top chassis are provided.

Description

Inverter circuit, backlight device and liquid crystal display device using the same {INVERTER CIRCUIT, BACKLIGHT DEVICE, AND LIQUID CRYSTAL DISPLAY DEVICE USING THE SAME}

1 is an exploded perspective view of a liquid crystal display device according to Embodiment 1;

2 is an exploded perspective view of the backlight device according to the first embodiment.

3 is a functional block diagram of a liquid crystal display device according to the first embodiment.

4 is a schematic diagram of an equivalent circuit of the backlight device according to the first embodiment.

5 is an equivalent circuit diagram of a balance circuit of the backlight device according to the first embodiment.

6 is a schematic diagram of an equivalent circuit of the backlight device according to the second embodiment.

7 is an equivalent circuit diagram of a balance circuit of the backlight device according to the second embodiment.

8 is a schematic diagram of an equivalent circuit of the backlight device according to the third embodiment.

Description of the Related Art [0002]

100: liquid crystal display 110: display unit

111: liquid crystal display panel 112: data circuit

113: gate circuit 114: tape substrate for data circuit

115: Tape Substrate for Gate Circuit

116: TFT substrate 117: CF substrate

120: backlight unit 121: reflector

122: cold cathode tube 123: optical sheet

124: balance circuit 130: storage container

131: bottom 132: side wall

140: top chassis 150: inverter circuit

151: first power supply line 152: second power supply line

153: first electrode 154: second electrode

155: electrode substrate 156: inverter transformer

157: condenser 158: choke coil

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter circuit which can be suitably used for a backlight device having a cold cathode tube, and to a backlight device using the same, and furthermore to a liquid crystal display device.

In general, liquid crystal display devices have excellent characteristics such as low voltage driving, low power consumption, light weight, and thinness, and are widely used as display devices such as monitor devices and television receivers in personal computers. It's growing.

The liquid crystal display device is generally composed of a backlight device and a display unit disposed in front of the backlight device, the backlight device supplies light to the display panel, and the display unit is light supplied from the backlight device. Modulation is added to display as an image.

In general, a backlight device includes a reflector, a light source, and an optical sheet, and can supply light to the display unit by applying a current to the light source.

By the way, when using a cold cathode tube as a light source of a backlight device, the inverter circuit which has an inverter transformer is used to light a cold cathode tube.

In general, one cold cathode tube is often lit by one transformer, but it is necessary to light up a plurality of cold cathode tubes in parallel with the large screen of the liquid crystal display device. Moreover, as a conventional technique, the discharge light lighting apparatus which connected several discharge lights in parallel to the output side of an inverter is described by patent document 1 (Unexamined-Japanese-Patent No. 2002-313593). In addition, in the technique described in Patent Document 1 (Patent No. 2002-313593), the current detection means, a switch capable of interrupting power supply, and an input voltage to the inverter are further adjusted between one end and the other end of the output side of the inverter. A variable resistance unit may be provided, and lighting control means for adjusting the resistance in the on-off and variable resistance units of the switch may be provided.

Certainly, in the prior art described above, since a plurality of discharge lamps are connected to and shared by one inverter transformer, the circuit scale can be reduced, which is useful, and also prevents a chain of lighting abnormalities when one discharge lamp causes an abnormality. Also useful for

However, in the state of the said technique, the subject of the fall of energy efficiency by the increase of the number of discharge lights etc. remains. Specifically, for example, in the case of driving a cold cathode tube which is a single discharge lamp with one inverter transformer, if the equivalent capacitance of the cold cathode tube is C _S , the Q value at the resonance frequency ω is expressed by the following equation (1). Is given by

Q = 1 / (ωRC _S )

(Where R is the equivalent resistance of the circuit)

On the other hand, when driving a plurality of cold cathode tubes with one inverter transformer, when the number of cold cathode tubes is N, the Q _N value at the resonance frequency? Is given by the following equation (2).

QN = 1 / (ωRC _S N)

In other words, as the N increases, the Q value at the resonance frequency ω falls to one-Nth. On the other hand, in general, when the Q value falls, the resonance energy decreases, the shape of the sine wave at the resonance point collapses, harmonic current flows through the cold cathode tube, and the loss that does not contribute to light emission increases, resulting in a decrease in energy efficiency.

Accordingly, an object of the present invention is to provide an inverter circuit, a backlight device, and a liquid crystal display device using the same, which solve the above problems, maintain energy efficiency, and consume less power even when a plurality of cold cathode tubes are provided.

MEANS TO SOLVE THE PROBLEM As a result of earnestly examining the said subject, in order to prevent the collapse of the shape of the said sine wave, a frequency adjusting means is provided in the drive primary side of an inverter transformer, and the resonance frequency in the whole circuit can be adjusted. In view of the fact that the Q value can be increased, the present invention has been reached.

That is, the backlight device which concerns on this invention has the inverter circuit which has an inverter transformer, and the some cold cathode tube connected in parallel with the inverter transformer in an inverter circuit, and an inverter circuit is provided in the drive primary side of an inverter transformer. A frequency adjusting means is provided. Here, it is a preferable aspect to implement | achieve using a choke coil and a capacitor as a frequency adjustment means. By doing in this way, this invention can adjust the resonance frequency in the whole circuit, can raise the Q value in a resonance frequency, and can suppress the increase of power consumption more.

In the backlight device according to the present invention, it is also preferable that there are a large number of inverter transformers in the inverter circuit. For example, the adjacent cold cathode tubes may be connected to different inverter transformers so that a current in a reverse phase can flow.

In the backlight apparatus according to the present invention, when the frequency adjusting means is realized by the choke coil and the capacitor, it is also preferable that they are connected in series.

Further, in the backlight device according to the present invention, it is also preferable to have a balance circuit connected to each of the plurality of cold cathode tubes in order to keep the current of each cold cathode tube more balanced.

Further, the liquid crystal display device according to the present invention can maintain low power consumption as a whole by using the above backlight device, and specifically, a display unit having a liquid crystal panel, a data circuit connected to the liquid crystal panel, and a gate circuit. And a backlight device having a inverter circuit, an inverter circuit having a frequency adjusting means on the drive primary side of the inverter transformer, and a plurality of cold cathode tubes connected in parallel to the inverter transformer in the inverter circuit, a display unit, and a backlight device. It is characterized by having a storage container and a top chassis. Here, it is preferable that the frequency adjusting means is realized by using a choke coil and a capacitor. By doing in this way, this invention can adjust the resonance frequency in the whole circuit, can raise the Q value in a resonance frequency, and can suppress the increase of power consumption more.

In the liquid crystal display device according to the present invention, it is also preferable that there are a large number of inverter transformers in the inverter circuit. For example, the adjacent cold cathode tubes may be connected to different inverter transformers so that a reverse phase current flows.

In the liquid crystal display device according to the present invention, when the frequency adjusting means is realized by the choke coil and the capacitor, it is also preferable that they are connected in series.

In the liquid crystal display device according to the present invention, it is also preferable to have a balance circuit connected to each of the plurality of cold cathode tubes in order to keep the current of each cold cathode tube more balanced.

In addition, the inverter circuit according to the present invention may have the above functions together with a plurality of cold cathode tubes. However, the inverter circuit alone can be distributed in the market as a component such as a liquid crystal display device or a backlight device. And an inverter transformer and frequency adjusting means provided on the drive primary side of the inverter transformer. Here, it is preferable that the frequency adjusting means is realized by using a choke coil and a capacitor. By doing in this way, this invention can adjust the resonance frequency in the whole circuit of several cold cathode tubes connected in parallel, can raise the Q value in a resonance frequency, and can suppress the increase of power consumption further. .

In the inverter circuit according to the present invention, it is also preferable that there are many inverter transformers. For example, in a plurality of cold cathode tubes connected thereto, adjacent cold cathode tubes can be connected to different inverter transformers, and the current can be reversed.

In the inverter circuit according to the present invention, when the frequency adjusting means is realized by the choke coil and the condenser, it is also preferable that they are connected in series.

EMBODIMENT OF THE INVENTION Embodiment of this invention is described below with reference to drawings. However, this invention can be implemented with many other forms, and is not interpreted limited to description content of embodiment shown below. Moreover, in the drawings referred to in the present embodiment, the same reference numerals are given to the same portions or portions having the same functions, and repetitive description thereof will be omitted.

Embodiment 1

1 is an exploded perspective view of a liquid crystal display device (hereinafter referred to as "liquid crystal display device") according to the present embodiment.

As shown in FIG. 1, the liquid crystal display device 100 includes a display unit 110, a backlight unit 120, a storage container 130 for storing them, and a top chassis 140.

The display unit 110 further has a liquid crystal display panel 111 for displaying an image, a data circuit 112 and a gate circuit 113 for providing a drive signal for driving the liquid crystal display panel 111. The data circuit 112 and the gate circuit 113 are electrically connected to the liquid crystal display panel 111 through the tape substrate 114 for the data circuit and the tape substrate 115 for the gate circuit, respectively.

The liquid crystal display panel 111 is further disposed between the thin film transistor (hereinafter referred to as "TFT") substrate 116 and the color filter (hereinafter referred to as "CF") disposed opposite the TFT substrate 116 and the substrate 117 and these substrates. It has a liquid crystal.

The TFT substrate 116 is not particularly limited as long as it can form a TFT and an electrode. For example, a transparent glass substrate can be suitably used, and a plurality of gate electrodes intersect with the gate electrode on the TFT substrate. And a plurality of TFTs arranged in the vicinity of intersections of the plurality of data electrodes and the gate electrode and the data electrode, and the pixel electrodes connected to each of the plurality of TFTs and connected to the gate electrode and the data electrode. Have at least Furthermore, the common electrode provided corresponding to the pixel electrode may be formed on the TFT substrate 116 or may be formed on the CF substrate 117.

Also in the CF substrate 117, as long as the CF can be formed, similarly to the TFT substrate 116, the CF substrate 117 is not particularly limited. For example, a transparent glass substrate can be suitably used. CF formed on the CF substrate can be realized by arranging an organic layer containing a dye which transmits red (R), green (G), or blue (B) color corresponding to each pixel electrode of the TFT substrate. . In addition, the liquid crystal display device 100 is provided with a backlight unit 120 on the back side, and in order to display light as an image by controlling the light from the backlight device using an optical change by the liquid crystal display panel, the TFT substrate 116 and the CF substrate 117. It is a preferable aspect that both are transparent substrates.

The storage container 130 has the bottom face 131 and the side wall 132 provided in the short side of this bottom face 131, and accommodates a display unit 110, a backlight device 120, etc. In addition, the storage container 130 is fitted with the top chassis 140 to fix the display unit 110 and the like stored therein and to prevent damage due to external impact.

2 is an exploded perspective view of the backlight unit 120 in the liquid crystal display device 100.

The backlight unit 120 includes a reflecting plate 121, a plurality of cold cathode tubes 122 disposed substantially parallel to the reflecting plate 121, an optical sheet 123 disposed above the plurality of cold cathode tubes, and a plurality of cold cathode tubes 122. The first electrode 153 and the plurality of second electrodes 154 provided in each of the plurality of cold cathode tubes are connected. A plurality of cold cathode tubes among the backlight units are electrically connected in parallel to form a circuit on the backlight unit side. The plurality of second electrodes 154 are formed on the electrode substrate 155, and a balance circuit described later is formed on the electrode substrate 155.

Further, an inverter circuit 150 is connected to the backlight unit 120, and the inverter circuit 150 is disposed outside the storage container 130. The inverter circuit 150 generates a discharge voltage for driving the backlight unit 120 and applies a voltage to the backlight unit 120 through the first power supply line 151 and the second power supply line 152. Specifically, the first power supply line 151 and the second power supply line 152 are connected to the first electrode 153 and the electrode substrate 155 formed on both sides of the backlight unit 120, respectively. Moreover, it is appropriately possible to provide at least part of the inverter circuit 150 side on the backlight unit side. In the present specification, in principle, the inverter circuit refers to a circuit for controlling the backlight unit among the entire inverter circuits. In the case of the backlight device, a circuit used for controlling the backlight unit among the inverter circuits is used. This includes the backlight unit.

In addition, the optical sheet 123 is provided in order to improve the characteristics of the light supplied by the backlight device 110. The optical sheet 123 may be a diffusion sheet for diffusing light or a prism sheet for condensing light. The number of cold cathode tubes 122 in the backlight device 120 is not particularly limited, but is preferably 10 or more, more preferably 14 or 16.

3 is a functional block diagram of the present liquid crystal display device. As described above, in the present liquid crystal display device, an alternating voltage supplied from an external power source is applied to the cold cathode tube 122 via an inverter circuit. The inverter circuit 150 also applies a gate voltage or the like to the gate electrode, the data electrode, and the common electrode in the display unit 110 (however, illustration is omitted).

4 is a functional block diagram of the backlight device according to the present embodiment, and is a diagram for explaining the details of the backlight device in FIG.

The backlight device includes an inverter circuit 150 and a circuit on the backlight side including a plurality of cold cathode tubes 122 connected in parallel to the inverter circuit. The inverter circuit 150 includes a power supply, an inverter transformer 156, and a capacitor 157 and a choke coil 158 provided on the drive primary side of the inverter transformer 156. Here, the power supply can adopt various well-known structures which can generate an alternating current, and are not specifically limited (it abbreviate | omits about detail). In addition, the circuit on the backlight unit side has a plurality of cold cathode tubes 122 connected in parallel and a balance circuit 124 connected in series with each of these cold cathode tubes on the side opposite to the side connected with the inverter transformer of these cold cathode tubes. Consists of. In this backlight device, by arranging a balance circuit 124, the current of each cold cathode tube can be maintained in equilibrium. 5 shows an example of an equivalent circuit diagram of a part of the balance circuit according to the present embodiment.

The balance circuit shown in FIG. 5 is comprised with the some balance transformer 125, and one side of the coil in each of the some balance transformer 125 is connected to the adjacent cold cathode tube 122, respectively. On the other hand, one of the coils is connected in series with the other balance transformer to form a circuit and is grounded. In this way, the present balance circuit can maintain the current between the cold cathode tubes in equilibrium. Moreover, various structures can also be considered about the structure of a balance circuit.

The circuit on the backlight unit side functions as a resonant circuit due to the capacity of the cold cathode tube, the resistance in the circuit, and the like, and can drive the cold cathode tube with a sine wavelength voltage current through an inverter transformer. On the other hand, in the backlight device according to the present embodiment, since the capacitor 157 and the choke coil 158 are disposed on the inverter circuit side, the frequency can be adjusted by appropriately adjusting the constant. As a result, the Q value can be increased, the shape of the sine wave suppressing the harmonic current at the resonance point can be maintained, the effective luminous efficiency can be achieved by pressing the reactive current of the resonance circuit, and the power consumption can be reduced. The capacitor is not particularly limited in its function, and for example, the capacitor may have a predetermined capacitance based on an integer obtained at the time of manufacturing the backlight unit. You may use it. Moreover, it is also extremely useful to set it as the structure which the winding direction in the drive primary side of an inverter transformer and the winding direction of a choke coil are connected in the reverse direction from a frequency adjustment viewpoint. Furthermore, as described above, the value of the current and the capacity of the capacitor used in the backlight device can be appropriately adjusted to realize the desired frequency. However, for example, the amplitude of the voltage in the inverter circuit is about ± 150 to 200 V The voltage value in the circuit on the backlight unit side is about ± 1 kV, and the capacity of the capacitor is preferably about 5 nF to 100 nF. In addition, the inductance of the choke coil is preferably about 100 uH to 700 uH.

As described above, according to the present embodiment, a backlight device having lower power consumption, a liquid crystal display device using the same, and an inverter circuit for realizing this backlight device are maintained even if the energy efficiency is kept high and a plurality of cold cathode tubes are provided. Can be provided.

Embodiment 2

6 is a functional block diagram of a backlight device according to the present embodiment.

The liquid crystal display device according to the present embodiment is almost the same as the liquid crystal display device described in Embodiment 1, but the circuit configuration in the backlight device is different. More specifically, in the first embodiment, a plurality of cold cathode tubes are connected in parallel to one inverter transformer and configured as one resonant circuit. In the present embodiment, the plurality of cold cathode tubes have two inverter transformers. Each of the cold cathode tubes is connected to an inverter transformer different from the adjacent cold cathode tubes, and constitutes two resonant circuits. In detail, the inverter circuit 150 includes a power supply, a frequency converting means including a condenser 157 and a choke coil 158 connected to the power supply, and two inverters connected in parallel to the frequency converting means. It is configured with inverter transformer 156. As mentioned above, also with this embodiment, the effect similar to Embodiment 1 can be acquired. Furthermore, in this case, it is preferable that the cold cathode tubes connected to the inverter transformers are equal in number, respectively, from the viewpoint of uniformity of the current, and in the case of having two inverter transformers, the total number of cold cathode tubes is preferably even. An equivalent circuit diagram in an example of a part of the balance circuit according to the present embodiment is also shown in FIG.

As in the first embodiment, the balance circuit shown in FIG. 7 includes a plurality of balance transformers 125, and one of the coils in each of the plurality of balance transformers 125 is connected to an adjacent cold cathode tube 122, respectively. . On the other hand, one of the coils is connected in series with another balance transformer to form a circuit, and although grounded, the balance transformers of cold cathode tubes connected to the same inverter transformer are connected to form two circuits. By doing this, the present balance circuit can maintain the current between the cold cathode tubes in a balanced manner.

As described above, the present invention also provides a backlight device with a lower power consumption, a liquid crystal display device using the same, and an inverter circuit for realizing the backlight device even when the energy efficiency is kept high and a plurality of cold cathode tubes are provided. Can provide.

Moreover, in this embodiment, since the conditions of a cold cathode irrigation stage are made the same, the example which arrange | positions one frequency conversion means with respect to several inverter transformer is shown, As an application example of this embodiment, each inverter transformer is shown. It is also possible to arrange one frequency conversion means with respect to each other and to adjust the frequencies individually. In this way, finer adjustment is possible, and a backlight device with higher power efficiency and less power consumption can be realized.

Embodiment 3

8 is a functional block diagram of a backlight device according to the present embodiment.

The liquid crystal display device according to the present embodiment is almost the same as the liquid crystal display device described in Embodiment 2, but the circuit configuration of the backlight device is different. More specifically, in Embodiment 2, it has two inverter transformers, and each of the some cold cathode tubes is connected to the inverter transformer different from the adjacent cold cathode tubes, and comprises two resonant circuits. In the embodiment, the inverter transformer is one, but the one coil on the driving primary side and the two coils on the secondary side are different, and the coils on the driving primary side are common. In this manner, the same effects as in the second embodiment can be obtained. In particular, according to the present embodiment, since an inverter transformer can be realized in one, there is an advantage that the size can be reduced. In this case, the number of cold cathode tubes in each resonant circuit is preferably the same, and as a result, the total number of cold cathode tubes is preferably even. Moreover, about the equivalent circuit diagram in the example of one part of the balance circuit which concerns on this embodiment, it can be made the same as the case of Embodiment 2. As shown in FIG. That is, it can be made similar to FIG.

As described above, even in the present embodiment, a backlight device having low energy consumption, a liquid crystal display device using the same, and an inverter circuit for realizing the backlight device are maintained even when the energy efficiency is maintained and a plurality of cold cathode tubes are provided. Can provide.

As mentioned above, the backlight apparatus which concerns on this invention can be used suitably for a liquid crystal display device. The liquid crystal display device is useful as a display device such as a monitor device or a television receiver in a personal computer. Moreover, the inverter circuit is useful as such a component, and therefore the present invention has industrial applicability.

As described above, the present invention provides a backlight device having a lower power consumption, a liquid crystal display device using the same, and an inverter circuit for realizing the backlight device even when the energy efficiency is kept high and the plurality of cold cathode tubes are provided. can do.

Claims (12)

delete delete delete A plurality of balances having an inverter circuit having a frequency adjusting means on a drive primary side of the inverter transformer and a plurality of cold cathode tubes connected in parallel to the inverter transformer in the inverter circuit, a first coil and a second coil In a backlight device with a trance, And said first coil of each of said plurality of balance transformers is connected to said adjacent cold cathode tube, respectively, and said second coil is connected in series with another balance transformer to form a circuit, and is grounded. The method of claim 4, wherein The frequency adjusting means includes a choke coil and a capacitor connected in series. An inverter circuit having a plurality of inverter transformers and frequency adjusting means connected in parallel to a drive primary side of the plurality of inverter transformers, a plurality of cold cathode tubes and first coils connected in parallel to the inverter transformers in the inverter circuits; In a backlight device having a plurality of balance transformers having a second coil, The first coils of each of the plurality of balance transformers are respectively connected to the adjacent cold cathode tube, and the second coils are connected in series with other balance transformers to form a circuit, grounded, and connected to the same inverter transformer. A balance transformer between cathode tubes is connected. A plurality of balance transformers having a plurality of cold cathode tubes, a first coil and a second coil connected in parallel to an inverter circuit having an inverter transformer and a frequency adjusting means on a drive primary side of the inverter transformer and an inverter transformer in the inverter circuit. In the backlight device having a, The inverter transformer, The coil of the driving primary side is composed of one, and the coil of the secondary side connected to the cold cathode tube is composed of two, And said first coil of each of said plurality of balance transformers is connected to said adjacent cold cathode tube, respectively, and said second coil is connected in series with another balance transformer to form a circuit, and is grounded. A display unit having a liquid crystal panel, a data circuit and a gate circuit connected to the liquid crystal panel; A plurality of balance transformers having a plurality of cold cathode tubes, a first coil and a second coil connected in parallel to an inverter circuit having an inverter transformer and a frequency adjusting means on a drive primary side of the inverter transformer and an inverter transformer in the inverter circuit. Backlight device with A storage container and a top chassis for storing the display unit and the backlight device; And the first coil of each of the plurality of balance transformers is connected to the adjacent cold cathode tube, respectively, and the second coil is connected in series with another balance transformer to form a circuit, and is grounded. 9. The method of claim 8, And the frequency adjusting means has a choke coil and a capacitor connected in series. delete delete delete

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