JPH09258165A - Liquid crystal device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal device capable of preventing useless power consumption. SOLUTION: When lighting means 8a, 8b lighting a liquid crystal element don't turned on even when power is supplied, the lighting means 8a, 8b are irradiated by light from an auxiliary turn-on means 11, and the not turned on lighting means 8a, 8b are lighted, and on the other hand, a control means 15 controls so that the auxiliary turn-on means 11 performs light irradiation operation only when power is supplied through a switch means 14, and the useless power consumption is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal device for displaying an image by illuminating a liquid crystal element with a lighting means, and more particularly to a liquid crystal device provided with an auxiliary lighting means for lighting the lighting means.

[0002]

2. Description of the Related Art Conventionally, an example of a liquid crystal device for displaying an image by illuminating a liquid crystal element by an illuminating means is an EVF (Electric View Find) for a video camera.
r), and in this EVF, a fluorescent lamp is used as a light source of a backlight which is an illuminating means for illuminating a liquid crystal element.

By the way, in such an EVF,
In order to avoid the influence of external light, the structure is such that external light does not enter the interior, but if external light does not enter the interior, dark lighting may occur in which the fluorescent lamp does not light even when the power is turned on.

Therefore, conventionally, as a measure against dark lighting when the power is turned on, an auxiliary light emitting element such as a light emitting diode 21 is installed near the fluorescent lamp 20 as shown in FIG. By irradiating the fluorescent lamp 20 with light, the fluorescent lamp 20 can be reliably turned on.

[0005]

However, in such a conventional liquid crystal device, the auxiliary light emitting element is always made to emit light after the fluorescent lamp is turned on, although the auxiliary light emission is not required. There is a problem that the power of the auxiliary light emitting element is wasted.

Therefore, the present invention has been made in order to solve such a problem, and an object thereof is to provide a liquid crystal device capable of preventing wasteful consumption of electric power.

[0007]

SUMMARY OF THE INVENTION The present invention relates to a liquid crystal device for displaying an image by illuminating a liquid crystal element by means of illumination means, and when the power is turned on, the illumination means which is not turned on is turned on so that the illumination means is turned on. Auxiliary lighting means for irradiating
The auxiliary lighting means includes control means for controlling the light irradiation operation only when the power is turned on.

The present invention is also characterized in that the control means comprises switch means for supplying power to the auxiliary lighting means and switch control means for controlling the switch operation of the switch means.

Further, the present invention is characterized in that the switch control means comprises a capacitor, and the switch means is caused to perform a power supply operation only during a charging period of the capacitor.

Further, according to the present invention, the switch control means includes a current detection circuit, and a power supply operation to the switch means is performed until the current detection circuit detects that the current flowing through the lighting means reaches a predetermined magnitude. It is characterized in that it is performed.

The present invention is also characterized in that the illuminating means is a fluorescent lamp.

The present invention is also characterized in that the auxiliary lighting means is a light emitting diode.

Further, the present invention is characterized in that the switch means is a transistor.

With this configuration, when the illumination means for illuminating the liquid crystal element is not turned on when the power is turned on, the auxiliary lighting means emits light toward the illumination means and the illumination means that is not turned on is turned on. On the other hand, the control means controls the auxiliary lighting means to perform the light irradiation operation only when the power is turned on, thereby preventing wasteful power consumption.

Further, the control means causes the switch means for supplying power to the auxiliary lighting means to perform the power supply operation only during the charging period of the capacitor to prevent wasteful consumption of power.

Further, the control means causes the switch means to perform the power supply operation until the current detection circuit detects that the current flowing through the lighting means reaches a predetermined magnitude, thereby wasting power. Try to prevent it.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic sectional view of a liquid crystal device according to a first embodiment of the present invention. In the figure, 1 is a liquid crystal device, 2 is a transmissive liquid crystal cell which is a liquid crystal element, and 3 is a backlight device which is an illuminating device for illuminating the liquid crystal cell 2 from the back side. Reference numeral 4 denotes a protective plate for protecting the liquid crystal cell 2 from external impact or the like, and reference numeral 5 denotes a case for attaching the liquid crystal cell 2, the backlight device 3, and the protective plate 4.

Here, in the liquid crystal cell 2, the ferroelectric liquid crystal 7 is sandwiched between the pair of glass substrates 6a and 6b, and the transmittance is controlled by the electro-optical effect of the ferroelectric liquid crystal 7 to the information display surface 6c side. It is for displaying information. In addition, the backlight device 3 includes fluorescent lamps 8a and 8 that are illumination means.
b, a light guide body 9 that has been surface-treated for uniform brightness,
It is provided with a reflection plate, a diffusion plate and the like (not shown).

By the way, FIG. 2 is a circuit diagram of such a backlight device 3. In FIG. 2, reference numeral 11 designates a light emitting diode 10 which is an auxiliary lighting means for lighting the fluorescent lamps 8a and 8b which do not light up, as a measure against dark lighting. Its power, 12
Is a power supply for the fluorescent lamps 8a and 8b, 13 is a power supply for the light emitting diode 10 and a power supply 12 for the fluorescent lamp, and is turned on when the power switch (not shown) of the liquid crystal device 1 is turned on to supply power to each load. Power relay to control,
Reference numeral 14 is a transistor which is a switch means for supplying power to the light emitting diode 11 to turn on the light emitting diode 11.

Further, R1 is a first resistor for limiting the current flowing through the light emitting diode 11, and 15 is a control circuit which is a switch control means for controlling the switching operation of the transistor 14, and this control circuit 15 has a capacitor C1 and a second and It is composed of third resistors R2 and R3. The control circuit 15 and the transistor 14 allow the light emitting diode 1
The control unit 1 is configured to be turned on only when the power is turned on to perform the light irradiation operation.

The control circuit 15 is for turning on the transistor 14 and turning on the light emitting diode 11 when the power relay 13 is turned on to turn on the fluorescent lamps 8a and 8b when the power switch is turned on. is there.
When the power relay 13 is turned on, the fluorescent lamp 8
AC power is supplied from the fluorescent lamp power source 12 to the a and 8b, but since the light emitting diode 11 is turned on by the control circuit 15, the fluorescent lamps 8a and 8b are always turned on.

Further, the control circuit 15 is adapted to turn off the transistor 14 by charging the capacitor C1 when the charging period of the capacitor C1 elapses,
As a result, the light emitting diode 11 is turned off after the charging period. Then, after turning on the fluorescent lamps 8a and 8b by turning on the power switch as described above, the light emitting diode 11 is turned off after the charging period elapses so that the light emitting diode 11 performs the light irradiation operation only when the power is turned on. Become. As a result, it is possible to reduce the wasteful power consumption.

Next, the illuminating operation of the liquid crystal device thus constructed will be described.

When the power supply relay 13 is turned on when the power switch is turned on, the first resistor R from the light-emitting diode power supply 10 is turned on.
1 and the control means 15 are supplied with a DC voltage, and the fluorescent lamp power supply 12 supplies an AC voltage to the fluorescent lamps 8a and 8b.

When a direct current voltage is supplied to the control circuit 15 in this way, first, a current flows through the capacitor C1 → the resistor R2 → the base of the transistor 14, so that the transistor 14 is turned on and the collector and the emitter are conducted, As a result, a current flows through the light emitting diode 11, and the light emitting diode 11 lights up. At the same time, the fluorescent lamp 8
AC power is also supplied from the fluorescent lamp power source 12 to the a and 8b, but since the light emitting diode 11 emits light in this way, the fluorescent lamps 8a and 8b do not turn on in the dark but always turn on.

On the other hand, when the charging period of the capacitor C1 elapses thereafter, the capacitor C1 is charged and the transistor 1
Since the base current of 4 stops flowing, the transistor 14
Is turned off and the light emitting diode 11 is turned off.

As described above, the control circuit 15 turns on the light emitting diode 11 only when the power is turned on, so that it is possible to reduce the wasteful power consumption.

On the other hand, FIG. 3 is a circuit diagram of a backlight of a liquid crystal device according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 2 indicate the same or corresponding portions.

In the figure, 20 is a switch control means, which is provided with a current detection circuit 21. Here, the current detection circuit 21 detects the current flowing through the fluorescent lamps 8a, 8b, and the switch control means 20 determines the amount of the detected current detected by the current detection circuit 21. The transistor 14 is turned on / off by determining whether or not the 8b is turned on.

That is, if the value of the detected current is small, it is determined that the fluorescent lamps 8a and 8b are not turned on, and the transistor 14 is turned on to turn on the light emitting diode 11. By turning on the light emitting diode 11 in this manner, the fluorescent lamps 8a, 8a
b comes on.

On the other hand, when the fluorescent lamps 8a and 8b are turned on in this manner and the magnitude of the current flowing through the fluorescent lamps 8a and 8b reaches a predetermined value, the fluorescent lamps 8a and 8b are turned on.
Is determined to be turned on, the transistor 14 is turned off, and the light emitting diode 11 is turned off. Then, after it is determined that the fluorescent lamps 8a and 8b are turned on in this manner, the light emitting diode 11 is turned off, so that the light emitting diode 11 can be caused to emit light only when the power is turned on, which is wasted. Power consumption can be reduced.

Next, the illuminating operation of the liquid crystal device thus constructed will be described.

When the power relay 13 is turned on when the power switch is turned on, no current flows because the fluorescent lamps 8a and 8b do not emit light even when AC voltage is initially supplied. However, the switch control means 20 determines that the fluorescent lamps 8a and 8b are not turned on from the current flowing through the fluorescent lamps 8a and 8b detected by the current detection circuit 21, and turns on the transistor 14 to turn on the light emitting diode 11. .
As a result, the fluorescent lamps 8a and 8b are irradiated with light, dark lighting is avoided, and the fluorescent lamps 8a and 8b are turned on.

When the fluorescent lamps 8a and 8b are turned on, the current flowing through the fluorescent lamps 8a and 8b is increased, whereby the switch control means 20 judges that the fluorescent lamps 8a and 8b are turned on and turns off the transistor 14. The light emitting diode 11 is turned off.

[0036]

As described above, according to the present invention, it is possible to prevent wasteful power consumption by controlling the auxiliary lighting means to perform the light irradiation operation only when the power is turned on.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a liquid crystal device according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram of a backlight device of the liquid crystal device.

FIG. 3 is a circuit diagram of a backlight of a liquid crystal device according to a second embodiment of the present invention.

FIG. 4 is a circuit diagram of a backlight of a conventional liquid crystal device.

[Explanation of symbols]

 1 Liquid Crystal Device 2 Liquid Crystal Cell 3 Backlight Device 8a, 8b Fluorescent Lamp 10 Power Supply for Light Emitting Diode 11 Light Emitting Diode 12 Power Supply for Fluorescent Lamp 14 Transistor 15 Control Circuit 20 Switch Control Means 21 Current Detection Circuit C1 Capacitor

Claims (7)

[Claims] 1. A liquid crystal device for displaying an image by illuminating a liquid crystal element with an illuminating means, and an auxiliary lighting means for irradiating light to the illuminating means in order to light the illuminating means when the power is turned on. A liquid crystal device, comprising: a control unit that controls the auxiliary lighting unit to perform the light irradiation operation only when the power is turned on. 2. The liquid crystal device according to claim 1, wherein the control means includes a switch means for supplying power to the auxiliary lighting means and a switch control means for controlling a switch operation of the switch means. . 3. The liquid crystal device according to claim 1, wherein the switch control means includes a capacitor, and the switch means is caused to perform a power supply operation only during a charging period of the capacitor. 4. The switch control means includes a current detection circuit, and causes the switch means to perform a power supply operation until the current detection circuit detects that the current flowing through the lighting means reaches a predetermined magnitude. The liquid crystal device according to claim 1 or 2, wherein 5. The liquid crystal device according to claim 1, wherein the lighting unit is a fluorescent lamp. 6. The liquid crystal device according to claim 1, wherein the auxiliary lighting means is a light emitting diode. 7. The liquid crystal device according to claim 1, wherein the switch means is a transistor.