JPH06160804A - Illuminating device for liquid crystal display device - Google Patents

Abstract

PURPOSE:To solve the problem of interference fringes (beat disturbance) caused by the display signal of a panel and the inverter of an illuminating device without using a transparent conductive sheet, etc., in the illuminating device for the liquid crystal panel used in a liquid crystal TV, a personal computer, a work station, etc. CONSTITUTION:The device is constituted of a liquid crystal panel module, a frequency divider circuit 12 fetching a clock signal being a video signal from the liquid crystal panel module 11 (clock frequency: f0) and frequency-dividing the signal, and a fluorescent tube driving inverter circuit 13 (oscillating frequency: f0/N) synchronizing the oscillating frequency of the inverter of the fluorescent tube driving circuit with that of the clock signal of the video signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lighting device for a liquid crystal display device used in a liquid crystal TV, a personal computer, a workstation and the like.

[0002]

2. Description of the Related Art In recent years, display devices using liquid crystals have been widely used in various fields.

A conventional lighting device for a liquid crystal display device will be described below. FIG. 2 is a block diagram of a conventional lighting device for a liquid crystal display device. In FIG. 2, 21 is a liquid crystal panel, 22 is a transparent conductive sheet, 23 is a diffusion plate, 24 is a fluorescent tube, 25 is a reflector, and 26 is an inverter.

The operation of the illuminating device for a liquid crystal display device constructed as above will be described below. First, a signal is supplied to the liquid crystal panel 21 by means not shown, and characters and figures are displayed. Fluorescent tube 24
Receives high-frequency current from the inverter 26 and emits fluorescence. The emitted light is directed in a predetermined direction by the reflection plate 25, and reaches the liquid crystal panel 21 as a uniform light beam by the diffusion plate 23. Here, in order to prevent interference fringes between the video signal of the liquid crystal panel 21 and the high frequency of the inverter 26, the transparent conductive sheet 22 connected to the ground potential is inserted between the liquid crystal panel 21 and the fluorescent tube 24. There is.

[0005]

However, in the above conventional structure, the inverter 26 for lighting the fluorescent tube 24 at a high frequency is a self-excited oscillator for cost and efficiency, and the oscillation frequency is the ambient temperature. However, there is a problem in that interference fringes appear as beat interference on the screen of the liquid crystal panel 21 due to interference with video signals and the like because the fluctuations occur gradually due to fluctuations in the power supply voltage and power supply voltage. Conventionally, in order to solve this problem, a transparent conductive sheet 22 made of ITO or the like is inserted between the liquid crystal panel 21 and the fluorescent tube 24, and countermeasures are taken. It has a problem that the cost becomes high.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a panel without beat interference without using a transparent conductive sheet.

[0007]

In order to achieve this object, a lighting device for a liquid crystal display device according to the present invention is one in which the oscillating frequency of an inverter for driving a fluorescent tube which is a lighting means of an input video signal panel is synchronized. Out.

[0008]

With this configuration, it is possible to provide a lighting device for a liquid crystal display device without beat interference.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 11 is a liquid crystal panel module, 12 is a frequency dividing circuit, and 13 is a fluorescent tube drive inverter circuit.

The operation of the illuminating device for liquid crystal display device constructed as described above will be described with reference to FIG. First, the clock signal of the video signal is taken out from the liquid crystal module 11 and connected to the frequency dividing circuit 12. The frequency dividing circuit 12 is a known circuit using a counter or the like. For example, assuming that the clock frequency is fo = 20 MHz and the frequency dividing ratio is N: 500, the oscillation frequency of the inverter 13 is 40 kHz, which is in synchronization with the video signal, thus causing beat interference. There is no gradual change in the oscillation frequency of the fluorescent tube disturbance inverter circuit 13 that causes the above.

As described above, according to this embodiment, by providing the frequency dividing circuit 12 and synchronizing the oscillation frequency of the fluorescent tube driving inverter circuit 13 with the clock signal of the video signal, beat interference can be eliminated. .

In this embodiment, the signal on which frequency division is based is the clock signal, but it goes without saying that it may be a horizontal synchronizing signal or a vertical synchronizing signal.

[0014]

As described above, according to the present invention, by providing an inverter circuit synchronized with a video signal, an excellent illuminating device for a liquid crystal display device capable of taking beat countermeasures without using a transparent conductive sheet. It can be realized.

[Brief description of drawings]

FIG. 1 is a conceptual diagram of a lighting device for a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an exploded perspective view of a conventional lighting device for a liquid crystal display device.

[Explanation of symbols]

 11 liquid crystal panel module (clock frequency: fo) 12 frequency dividing circuit (frequency dividing ratio: 1 / N) 13 fluorescent tube drive inverter circuit

Claims (1)

[Claims] 1. A lighting device for a liquid crystal display device, wherein an oscillation frequency of an inverter for driving a lighting means of the liquid crystal display device is synchronized with an input video signal.