JP3259488B2 - Light source device and color liquid crystal display device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device used as a backlight of a display unit in, for example, a liquid crystal television device or a personal computer, and a color liquid crystal display device using the light source device.

[0002]

2. Description of the Related Art In recent years, color liquid crystal panel devices have been widely used in liquid crystal televisions and personal computers. This color liquid crystal panel is usually formed by disposing a backlight light source for emitting white light on one side and a color filter on which R, G, and B filters are arranged on one side, with a transmission type liquid crystal display panel at the center. It is composed of Here, in the color filters, filters of respective primary colors of R, G, and B are regularly arranged corresponding to respective dots of a dot matrix of the liquid crystal display panel, and one of the three primary colors (three dots) of a display image is used. It corresponds to a pixel. The space between the dots of the color filter is shielded from light by a black mask, which contributes to an improvement in contrast.

[0003]

However, in the above-mentioned color liquid crystal panel device, since the space between the dots of the color filter is masked, the light transmittance is extremely low, the screen becomes dark, and the three-dot screen is formed. Therefore, there is a structural problem that the resolution is reduced in order to represent one pixel.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a light source device capable of obtaining a bright and high-resolution screen and a color liquid crystal using the light source device. A display device is provided.

[0005]

That is, the present invention uses at least three or more fluorescent tubes each emitting light of a different color, and emits each of these fluorescent tubes in a time-division manner at a ratio corresponding to the emission characteristics of the emission color. The drive is controlled.

[0006]

According to the above configuration, a color image corresponding to the color emitted by the fluorescent tube is arranged via the fluorescent tube and the diffusion plate in synchronization with the time-division light emission drive. By driving the liquid crystal panel in a time-division display mode, a color image can be displayed using one dot of the liquid crystal display panel as one pixel without requiring a color filter or the like.
In addition, a screen with a high resolution can be obtained.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a color liquid crystal television device will be described below with reference to the drawings. FIG. 1 shows the overall basic circuit configuration. A television wave received by an antenna 11 is supplied to a tuner 12. The tuner 12 selects a specified channel according to a tuning signal from the tuning control circuit 13 and converts the selected channel into an intermediate frequency signal. Then, the intermediate frequency signal output from the tuner 12 is sent to the TV linear circuit 14.

The TV linear circuit 14 comprises an intermediate frequency amplifying circuit, a video detecting circuit, a video amplifying circuit, an AFT detecting circuit, etc., and amplifies the intermediate frequency signal from the tuner 12 by the intermediate frequency amplifying circuit. The video is detected by the detection circuit. Then, an audio signal is extracted from the output signal of the video detection circuit and sent to the audio circuit 15.

The audio circuit 15 comprises an audio detection circuit and an audio amplification circuit. The audio signal from the TV linear circuit 14 is detected and converted to a low-frequency signal. I do.

The output signal of the video detection circuit in the TV linear circuit 14 is sent to a chroma circuit 17 and a sync separation circuit 18 after being amplified by a video amplification circuit. The synchronization separation circuit 18 separates the horizontal and vertical synchronization signals included in the video signal, controls the composite synchronization signal C-SYNC to the tuning control circuit 13, and controls the timing of the horizontal synchronization signal H-SYNC and the vertical synchronization signal V-SYNC. Output to the circuit 19 respectively.

The TV linear circuit 14 AFT-detects the output signal of the intermediate frequency amplifying circuit by the AFT detecting circuit, extracts an AFT signal whose voltage value changes in an S-shape, and sends it to the tuning control circuit 13.

The tuning control circuit 13 receives key inputs such as tuning setting data and tuning up / down instructions from a key input unit 20. The tuning control circuit 13 generates a tuning signal having a voltage value corresponding to a specified channel based on the operation of a tuning up / down key on the key input unit 20 and an AFT signal from the TV linear circuit 14, and the like.
Output to 12.

The timing control circuit 19 generates a timing pulse 3 based on the horizontal synchronization signal H-SYNC and the vertical synchronization signal V-SYNC sent from the synchronization separation circuit 18.
φs is created and output to the time division control circuit 21.

The chroma circuit 17 subjects the video signal supplied from the TV linear circuit 14 to chroma processing to perform R, G, B
And outputs it to the time division control circuit 21. Although not shown, the time-division control circuit 21 has an A / D converter and a field memory for each of R, G, and B signal paths, and the primary color signals from the chroma circuit 17 are A / D converters.
The data is sampled in synchronization with the timing pulse 3φs by the D converter, converted into digital video data of 3 to 4 bits per pixel, and stored in the field memory. Then, the digital video data for each primary color stored in the field memory is output to the segment drive circuit 22 in a time division manner in synchronization with the timing pulse 3φs.

The timing control circuit 19 includes a TV
Horizontal synchronization signal H-SYNC supplied from the linear circuit 14
Further, a timing signal for display control is created based on the vertical synchronization signal V-SYNC, and the operation of the segment drive circuit 22 and the common drive circuit 23 is controlled.

The common drive circuit 23 generates a scanning signal in accordance with a timing signal from the timing control circuit 19, and sequentially drives the common electrodes of the transmissive LCD panel 24 for monochrome display. The segment drive circuit 22 sequentially reads 3 to 4 bits of video data supplied from the time division control circuit 21 by a timing signal from the timing control circuit 19, reads one line of video data, and responds to the video data. Thus, a gradation signal is generated, and the segment electrodes of the LCD panel 24 are driven for display.

The timing control circuit 19 outputs a display switching signal synchronized with the time division timing of the time division control circuit 21 to the backlight drive circuit 25. The backlight drive circuit 25 drives the cold-cathode tubes 26 to 28, which emit light of the R, G, and B primary colors, which are light sources of the backlight of the LCD panel 24, in a time-division manner in accordance with a display switching signal from the timing control circuit 19. The light emitted from the cold-cathode tubes 26 becomes planar uniform light via a diffusion plate (not shown) and irradiates the LCD panel 24 from the back.

Next, specific configurations of the backlight drive circuit 25 and the cold cathode tubes 26 to 28 will be described. FIG. 2 mainly shows a circuit configuration in the backlight drive circuit 25. A backlight-on signal from a control circuit (not shown) is input to the pulse generation circuit 31. This pulse generation circuit
Reference numeral 31 generates a pulse signal having a frequency sufficiently higher than the switching frequency of each color image, for example, 180 Hz, based on the backlight-on signal.

The pulse signal generated by the pulse generation circuit 31 is switched and selected by the switching circuit 32 in accordance with the display switching signal from the timing control circuit 19, and the light emission driver 3 for R
3. It is supplied to one of the G light emitting driver 34 and the B light emitting driver 35 in a time sharing manner.

The R light emission driver 33, the G light emission driver 34, and the B light emission driver 35 amplify and boost the pulse signal supplied through the switching circuit 32 to generate cold cathode fluorescent lamps (fluorescent tubes) 26 to 28. Is driven to light. The cold-cathode tubes 26 to 28 each have a light-emitting agent applied on the inner surface of the tube, for example, and emit light of each of the primary colors of R, G, and B by driving light-emitting drivers 33 to 35.

FIG. 3 exemplifies the internal circuit configuration of the R light emission driver 33 (G light emission driver 34, B light emission driver 35), and has the same structure as a general cold cathode tube driving circuit. Therefore, it will be described briefly. In the figure, the pulse signal supplied via the switching circuit 32 includes resistors R1 to R5, PN
P-type transistor Tr1, NPN-type transistor T
r2, a step-up transformer which is amplified by a DC backup power supply + VB by an amplifier circuit composed of a power FET and includes a capacitor C1 and a diode D1 for back electromotive force protection.
41 is applied across both ends of the primary winding. The cold cathode tubes 26 (to 28) are connected to the secondary winding of the step-up transformer 41, and the voltage boosted by the step-up transformer 41 is applied to emit light.

In the above configuration, one image of R (red) image data stored in the time division control circuit 21 is sequentially read out to the segment drive circuit 22 and displayed in FIG. 4 (1). While displayed on LCD panel 24 as indicated by period TR,
In synchronization with this, in the backlight drive circuit 25, the pulse signal generated by the pulse generation circuit 31 in the switching circuit 32 in response to the display switching signal from the timing control circuit 19 is shown in FIG.
The light is supplied to the R light emission driver 33 only for the period indicated by, and the cold cathode tube 26 is driven to emit light in red. As a result, LC
Although the D panel 24 itself has a monochrome structure, the cold cathode tube 26 as a backlight emits red light via the diffusion plate, so that a red image is displayed.

The reading of the R (red) image data from the time-sharing control circuit 21 is completed, and then the G (green) image is read and sequentially read to the segment driving circuit 22.
As indicated by the display period TG in FIG.
The backlight drive circuit is synchronized with this while
In step 25, the pulse signal generated by the pulse generation circuit 31 in the switching circuit 32 in response to the display switching signal from the timing control circuit 19 is used for the G light emission driver 34 for a period indicated by II in FIG.
To drive the cold-cathode tube 27 to emit light in green. As a result, although the LCD panel 24 itself has a monochrome structure, the cold cathode fluorescent lamp 27 as a backlight is provided through the diffusion plate.
Emits green light, so that a green image is displayed.

Similarly, G from the time-sharing control circuit 21
The reading of the image data for (green) is completed, and then B
The image for (blue) is read out and the segment drive circuit 22 is sequentially read.
Is read out, and as indicated by the display period TB in FIG.
While the image is displayed on the CD panel 24, the backlight driving circuit 25 synchronizes with the pulse signal generated by the pulse generation circuit 31 in the switching circuit 32 in response to the display switching signal from the timing control circuit 19, as shown in FIG. Is supplied to the B light emission driver 35 only for the period indicated by III, and the cold cathode tube 28 is driven to emit light in blue. As a result, although the LCD panel 24 itself has a monochrome structure, the cold cathode tube 28 as a backlight emits blue light via the diffusion plate, so that a blue image is displayed.

The display periods TR, TG of the images of the respective primary colors
, YB, a time obtained by adding the blanking period BL and the writing period WR of the image data of each primary color read from the time division control circuit 21 to the segment driving circuit 22 is added.
A period of display suspension is provided.

The cold cathode tubes 26 have afterglow characteristics, and the period of the cold cathode tubes 26 differs depending on the color.
As indicated by III, the display driving time of the cold cathode tubes 26 to 28 is shorter than the image display periods TR, TG, and YB. In FIG. 4 (2), the ratio of I: II: III is 3: 2: 4.
Can be arbitrarily set in advance in consideration of the afterglow characteristics. Further, the timing of starting the light emission driving of the cold cathode tubes 26 to 28 is set to be slightly earlier because a slight time lag occurs between the start of the light emission driving and the actual light emission. Become.

As described above, 1/60 seconds to 1/5
R, G, B color images of one screen in time division in 0 seconds
By displaying each image data three times, L
Color display can be realized while using one display dot of the CD panel 24 as one pixel as it is. In this embodiment, a cold cathode tube is used as a fluorescent tube. However, it goes without saying that a similar structure can be obtained by using a hot cathode tube.

[0028]

As described above in detail, according to the present invention, a color image can be displayed with one dot of the liquid crystal display panel as one pixel without requiring a color filter or the like. A light source device capable of obtaining a screen and a color liquid crystal display device using the light source device can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a circuit configuration of a color liquid crystal television device according to one embodiment of the present invention.

FIG. 2 is a block diagram mainly showing a configuration in a backlight driving circuit of FIG. 1;

FIG. 3 is a diagram showing a circuit configuration in the light emitting driver of FIG. 2;

FIG. 4 is an exemplary view for explaining the operation according to the embodiment.

[Explanation of symbols]

11 ... antenna, 12 ... tuner, 13 ... tuning control circuit, 14 ... TV linear circuit, 15 ... audio circuit, 16 ... speaker, 17 ... chroma circuit, 18 ... sync separation circuit, 19 ... timing control circuit, 20 ... key input Section, 21 ... time division control circuit, 22
... Segment drive circuit, 23 ... Common drive circuit, 24 ... LC
D panel, 25 backlight driving circuit, 26 to 28 cold cathode tube, 31 pulse generating circuit, 32 switching circuit, 33 light emitting driver for R, 34 light emitting driver for G, 35 light emitting driver for B.

Claims (2)

(57) [Claims] At least three or more fluorescent tubes each emitting light of a different color, and time-division driving means for controlling light-emitting driving of each of these fluorescent tubes in a time-division manner at a ratio corresponding to the emission characteristic of the emission color. A light source device characterized in that: 2. At least three or more fluorescent tubes each emitting light of a different color, time-division driving means for controlling light-emitting driving of each of these fluorescent tubes in a time-division ratio at a ratio corresponding to the emission characteristics of the emission colors, A transmission type liquid crystal panel arranged and arranged via a fluorescent tube and a diffusion plate; and a time division display driving of the liquid crystal panel with image data corresponding to a color emitted by the fluorescent tube in synchronization with the time division driving means. A color liquid crystal display device comprising: an image display driving means.