JPH06178240A - Liquid crystal display television receiver - Google Patents

Abstract

PURPOSE:To realize muting avoiding useless power consumption due to lighting of a back light through simple circuit configuration. CONSTITUTION:The receiver is provided with a back light 34 provided in the rear side of a liquid crystal display panel on which a television picture is displayed, a channel selection controller 14 generating a mute signal in the channel selection of a television broadcast reception wave and a back light drive circuit 22 having a logic circuit element stopping tentatively application of power to the back light 34 by a mute signal from the channel selection controller 14.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal television device for displaying a television image on a liquid crystal display panel having a backlight.

[0002]

2. Description of the Related Art In recent years, liquid crystal televisions using a liquid crystal display panel with a backlight for a display section have been widely used, including those for vehicles, because of their small size, light weight and excellent portability. In this type of liquid crystal television device, a video mute signal is output from a channel selection controller that controls a channel selection operation at the time of channel switching, so that a video signal after intermediate frequency detection or an RG output from a chroma demodulation circuit is output.
Muting has been performed in which the screen is darkened by a method such as setting the B signal to a black level and the display of a noisy screen is interrupted.

FIG. 4 shows a circuit configuration of a liquid crystal television device, particularly a video signal system, which adopts a mute method for setting the RGB signals output from the latter chroma demodulation circuit to a black level.

As shown in the figure, the television broadcast radio wave received by the antenna 11 is tuned by the tuner 12 by the tuning bias voltage BT from the tuning controller 14,
The amplified intermediate frequency signal IF is supplied to the video detection circuit 13.

The video detection circuit 13 detects the intermediate frequency signal IF to reproduce a video signal (Video) and sends it to the chroma demodulation circuit 15, while the automatic fine tuning control signal AF is supplied.
T is sent to the tuning controller 14.

The tuning controller 14 generates a tuning bias voltage BT to the tuner 12 based on the automatic fine tuning control signal AFT, and outputs a mute signal (MUTE) to the chroma demodulation circuit 15 during a tuning operation. To do.

The chroma demodulation circuit 15 obtains R, G, B primary color signals from the video signal from the chroma demodulation circuit 15 and outputs them to a liquid crystal display panel (LCD) 16 for display and output, and a channel selection controller. When the mute signal is input from 14, the above primary color signals are set to black level,
LCD display panel 16 Darkens the screen.

The liquid crystal display panel 16 is provided with a backlight integrally on the back side thereof, and its drive circuit (shown as "BL circuit" in the figure) 17 constantly supplies power regardless of whether or not there is a channel selection operation. Lighting is driven.

[0009]

In the muting method as described above, when the muting operation is executed by the mute signal, for example, the circuit such as the chroma demodulation circuit 15 is complicated and the number of parts is increased. In addition to this, there is a problem that power is wasted by unnecessary lighting of the backlight.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a liquid crystal television device capable of realizing muting with a simple circuit configuration and avoiding unnecessary power consumption. It is in.

[0011]

By the way, in a recent liquid crystal display television, a fluorescent tube serving as a light source of a backlight is not a cylindrical tube but an argon gas and a mercury vapor are enclosed between two plate glasses. The flat fluorescent lamp having the flat plate shape configured as described above has been commercialized. This flat fluorescent tube is excellent as a light source for a backlight of a liquid crystal display television that is required to be small and lightweight because it is thin and can obtain uniform surface emission, and it emits light for intermittent driving by pulse signals. The stop control is easy.

The present invention focuses on the characteristics of the flat fluorescent tube, and in a liquid crystal television device using the flat fluorescent tube as a backlight, a tuning controller for generating a mute signal during a tuning operation of television broadcast radio waves. The switching pulse and the mute signal are input, the flat fluorescent tube is intermittently driven in synchronization with the switching pulse by turning on / off the switching element, and the energization to the switching element is interrupted when the mute signal is input, for example, an AND circuit. And a backlight drive having a logic circuit element according to the present invention.

[0013]

With the above structure, muting for turning off the backlight at the time of channel selection can be realized simply by adding a simple logic circuit element in the backlight drive circuit, and a complicated mute in the television circuit can be realized. A circuit is unnecessary and useless power consumption can be avoided.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the circuit configuration thereof, which is basically the same as that shown in FIG. 4, and therefore, the same portions are denoted by the same reference numerals and the description thereof will be omitted.

In the figure, the video signal reproduced by the video detection circuit 13 is sent to the chroma demodulation circuit 21 and the sync separation circuit 23. The chroma demodulation circuit 21 has a configuration in which the mute circuit is deleted from the chroma demodulation circuit 15 of FIG. 4, and the R, G, B primary color signals are obtained from the video signal to the liquid crystal display panel 16 regardless of the mute signal. Send out.

The sync separation circuit 23 separates and generates a horizontal sync signal and a vertical sync signal in the video signal, sends both sync signals to the chroma demodulation circuit 21, and drives, for example, only the horizontal sync signal as a backlight. Send to circuit 22.

However, the mute signal output from the tuning controller 14 is output to the backlight drive circuit 22.
The backlight driving circuit 22 is for driving a backlight using a flat fluorescent tube described later to turn on, and temporarily turns off the flat fluorescent tube when a mute signal is input.

FIG. 2 shows a specific circuit configuration in the backlight drive circuit 22. The mute signal is input to the AND circuit 31. The AND circuit 31 also receives a horizontal sync signal (Hsync) from the sync separation circuit 23.
Is inputted as a switching pulse for intermittently driving the flat fluorescent tube 34, and its output is inputted to the gate terminal of the N-channel FET 32 as a switching element. The source terminal of the FET 32 is grounded, and the drain terminal is connected to one end of the primary winding of the inverter transformer 33. The supply voltage VCC is applied to the other end of the primary winding of the inverter transformer 33,
Both ends of the secondary winding are connected to both electrodes of the flat fluorescent tube 34.

In the circuit configuration as described above, when the normal flat fluorescent tube 34 is driven to light, the mute signal input from the tuning controller 14 to the AND circuit 31 in the backlight drive circuit 22 is shown in FIG. ), The horizontal synchronizing signal as shown in FIG. 3A is input to the FET 32 via the AND circuit 31.

The FET 11 is turned on only while this horizontal synchronizing signal is at "H" level, and during that time, the supply voltage V
CC is boosted by the inverter transformer 33 and applied as a voltage having a waveform as shown in FIG. 3C to the flat fluorescent tube 34, and the flat fluorescent tube 34 is driven to light.

Since the flat fluorescent tube 34 has an afterglow characteristic, the flat fluorescent tube 34 maintains the light emitting state while gradually lowering the brightness until the horizontal synchronizing signal becomes "H" level next time. By performing the lighting drive intermittently in this way, as a result, it is possible to perform constant lighting, and it is possible to realize stable driving.

However, during the tuning operation, the tuning controller 14 sets the mute signal to "L" as shown in FIG. 3 (2).
When it is inverted to the level, the gate of the AND circuit 31 is closed, and the horizontal synchronizing signal shown in FIG. 3A is cut off by the AND circuit 31 and is not supplied to the FET 32. Therefore, as shown in FIG. 3C, the voltage application to the flat fluorescent tube 34 is stopped and the fluorescent lamp 34 is turned off.

In the above embodiment, the horizontal synchronizing signal is used as the switching pulse for intermittently driving the flat fluorescent tube 34 which is the light source of the backlight, but the vertical synchronizing signal is not limited to the horizontal synchronizing signal. It goes without saying that they may be used or other clock pulses may be used.

[0024]

As described above, according to the present invention, in a liquid crystal television device using a flat fluorescent tube as a backlight, a channel selection controller for generating a mute signal at the time of a channel selection operation of television broadcast radio waves, and switching. A pulse and the mute signal are input, the flat fluorescent tube is intermittently driven in synchronization with the switching pulse by turning on / off the switching element, and the energization to the switching element is interrupted when the mute signal is input. Since it is equipped with a backlight drive having circuit elements, it is possible to realize muting that turns off the backlight at the time of channel selection simply by adding a simple logic circuit element in the backlight drive circuit, which complicates the television circuit. Unnecessary mute circuit and avoid unnecessary power consumption Rukoto it is possible to provide a liquid crystal television device capable.

[Brief description of drawings]

FIG. 1 is a block diagram showing a circuit configuration according to an embodiment of the present invention.

FIG. 2 is a diagram showing a detailed circuit configuration in the backlight drive circuit of FIG.

FIG. 3 is a diagram showing each signal waveform of FIG.

FIG. 4 is a block diagram showing the configuration of a video signal processing circuit of a conventional liquid crystal television device.

[Explanation of symbols]

11 ... Antenna, 12 ... Tuner, 13 ... Video detection circuit, 14 ...
Channel selection controller, 15, 21 ... Chroma demodulation circuit, 16 ... Liquid crystal display panel (LCD), 17, 22 ... Backlight drive circuit (BL circuit), 23 ... Sync separation circuit, 31 ... AND circuit, 32
... FET, 33 ... Inverter transformer, 34 ... Flat fluorescent tube.

Claims (1)

[Claims] 1. In a liquid crystal television device using a flat fluorescent tube as a backlight, a tuning control means for generating a mute signal during a tuning operation of a television broadcast wave, a switching pulse and the mute signal are input, and switching is performed. And a backlight driving unit having a logic circuit element for intermittently driving the flat fluorescent tube in synchronism with the switching pulse by turning the element on and off, and for interrupting energization to the switching element when the mute signal is input. Characteristic liquid crystal television device.