JPH04328031A - Display device - Google Patents

Abstract

PURPOSE:To always obtain optimum visibility of a display device by driving a light emission driving means in accordance with a result of detecting a temperature in the periphery to control light emitting action of a light emitting means, in the case of the display device mounted on an automobile or the like where the predetermined light emitting means is used as back surface illumination. CONSTITUTION:A CFL(back light) driving gear 1, used for back surface illumination of an on-vehicle LCD(liquid crystal display), is constituted of a CFL2 and an inverter circuit 3 as a high voltage generating part for generating CFL driving voltage. In the inverter circuit 3, a photosensor 4 of phototransistor constitution for detecting brightness in the periphery, for instance, of a front window, temperature switch 5 formed of a positive characteristic thermistor placed in an on-condition when a temperature is decreased, for instance, below the freezing point by detecting the temperature in a vehicle and a variable resistor 6 for adjusting brightness of the CFL2 are provided. In this way, driving voltage is controlled in accordance with brightness in the periphery, temperature in the vehicle and a resistance value of the variable resistor 6, operated by a user, to adjust the brightness of the CFL2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display device, and can be applied to, for example, a display device mounted on an automobile.

0002

2. Description of the Related Art Conventionally, display devices installed in automobiles have been required to be small, thin, and highly visible due to the need to attach them to dashboards, etc.
isplay) is used.

[0003] Actually, as a backlight for this LCD,
For example, cold cathode fluorescent lamps (CFLs) are advantageous in terms of emission temperature and brightness.
) is used so that the user (driver) can comfortably view the LCD display.

0004

[Problem to be Solved by the Invention] However, when using a CFL as a backlight for an LCD as described above, when the surroundings are bright during the day, the LCD display can be viewed comfortably if the light is driven at maximum brightness. When the surroundings become dark at night, the CFL may be too bright and interfere with driving.

[0005] In order to solve this problem, the brightness of the CFL is dimmed in synchronization with the lighting of the headlight or small lamp, similar to the display on a car's speedometer, etc., or the CFL is adjusted using an adjustment volume. It is conceivable to vary the brightness.

However, when synchronizing the brightness of the CFL with the lighting of the headlights, etc., as described above, the brightness of the CFL can only be varied in two levels, and some drivers may find that it is too dark when the vehicle is dimmed. There is a problem that makes it hard to see.

[0007] Furthermore, when the brightness of the CFL is varied using an adjustment volume, it is necessary to perform a complicated operation of adjusting the adjustment volume while looking at the LCD display each time the ambient brightness changes. In either case, the solution was still insufficient in terms of safe driving.

[0008] In addition to these problems, in CFL,
For example, lighting is guaranteed by inputting the rated voltage in the room temperature range of 0°C to 50°C. For this reason, when the ambient temperature changes rapidly, such as in a car, if you dim the CFL according to the ambient brightness, the CFL may change depending on the ambient temperature.
There is a possibility that the FL will not turn on.

[0009] In reality, the conditions described above occur immediately after starting a car at night or early in the morning in cold weather, and in this case, the CFL does not turn on while the temperature inside the car rises to the normal temperature range of 0°C to 50°C. First, it was still unsatisfactory in terms of user-friendliness.

The present invention has been made in consideration of the above points, and is an attempt to solve the conventional problems at once and propose a display device having a backlight that emits light in response to the surrounding environment in an optimal manner. be.

[0011]

[Means for Solving the Problems] In order to solve such problems, the present invention provides a display device that uses a predetermined light emitting means 2 as a backlight. Temperature detection means 5 to detect
and a control means 7 for driving the light emitting driving means 3 and controlling the light emitting operation of the light emitting means 2 according to the detection result VSH of the temperature detecting means 5.

0012

[Operation] The light emitting driving means 3 is driven in accordance with the detection result VSH of the temperature detecting means 5 to control the light emitting operation of the light emitting means 2, so that the backlight is caused to emit light in response to the surrounding temperature. obtain.

[0013]

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

In FIG. 1, reference numeral 1 indicates a CFL driving device used for back illumination of a vehicle-mounted LCD according to the present invention;
CFL2 from the in-vehicle power supply consisting of CFL2 and DC12 [V]
It is composed of an inverter circuit 3 as a high voltage generating section that generates a driving voltage.

In the case of this embodiment, the inverter circuit 3 includes a photo sensor 4 which has a photo transistor configuration and detects the brightness around the front window, for example, and a positive temperature coefficient thermistor which detects the temperature inside the car and turns on when the temperature falls below freezing. A temperature switch 5 and a variable resistor 6 for adjusting the brightness of the CFL 2 are attached.

As a result, the inverter circuit 3 controls the driving voltage according to the brightness around the front window detected by the photo sensor 4, the temperature inside the vehicle detected by the temperature switch 5, and the resistance value of the variable resistor 6 set by the user. C.F.
The brightness of L2 can be adjusted.

That is, the inverter circuit 3 is, for example, TL4.
PWM (plus width modulat
ion) circuit 7, a switching transistor Q1 of NPN type, and drive transistors Q2 and Q of PNP type.
3. Consists of an output transformer 8.

In practice, this PWM circuit 7 compares the internally generated sawtooth wave signal with the threshold voltage VSH supplied to the No. 4 pin, and determines the period during which the sawtooth wave signal is higher than the threshold voltage VSH. A switching pulse SPWM with a rising duty is generated, which is outputted from the 8th pin and the 11th pin of the PWM circuit 7, and is supplied to the base of the switching transistor Q1 via the resistor R1.

The emitter of this transistor Q1 has DC
An on-vehicle power supply +V of 12 [V] is inputted, and this on-vehicle power supply +V is inputted to the base of the transistor Q1 via a resistor R2.

In addition, the vehicle power supply +V is supplied to the 12th pin of the PWM circuit 7 as a driving power supply, and the 1st pin, the 7th pin, the 9th pin, the 10th pin, the 13th pin, the 1st pin
The 6th pin is connected to the earth line GND and grounded.
Furthermore, the 5th and 6th pins are connected to the ground line G through capacitor C1 and resistor R3, which are external constants, respectively.
Connected to ND and grounded.

Furthermore, the 2nd, 14th, and 15th pins of the PWM circuit 7 are commonly connected, and the 2nd pin is connected to the 4th pin through a resistor R4. Further, a photo sensor 4, a thermistor 5, and a variable resistor 6 are connected to the 4th pin of the PWM circuit 7, respectively.

Further, the collector of the transistor Q1 is connected to a reverse diode D whose one end is connected to the earth line GND.
1 and the coil L1 to the center tap of the first primary winding L10 of the transformer 8, and the emitter is connected to the ground line G through resistors R5 and R6, respectively.
Drive transistors Q2, Q connected to ND and grounded
3 base is supplied.

A resonant circuit formed by connecting a first primary winding L10 and a capacitor C2 in parallel is connected between the collectors of the transistors Q2 and Q3.
and the bases of Q3 are connected to both ends of the second primary winding L11.

As a result, the secondary winding L12 of the transformer 8 outputs D in accordance with the switching operation of the transistor Q1.
From the onboard power supply +V consisting of C12 [V], for example, AC12
A driving voltage VC consisting of a high voltage of 00 [V] is output,
This is supplied to CFL2 through capacitor C3, and as a result, CFL2 is turned on.

In the case of the CFL driving device 1 of this embodiment, the threshold voltage VSH supplied to the 4th pin of the PWM circuit 7 is controlled by the photo sensor 4, the temperature sensor 5, and the variable resistor 6. There is.

Of these, the photo sensor 4 detects the brightness around the front window, and when it becomes bright, the threshold voltage VSH decreases, so that the PWM
The rising pulse width of the switching pulse SPWM sent out from the circuit 7 is widened, and as a result, the driving voltage VC is increased and the CFL2 is lit more brightly.

On the contrary, when the brightness around the front window becomes dark, the threshold voltage VSH increases, and the rising pulse width of the switching pulse SPWM sent out from the PWM circuit 7 becomes narrower, and as a result, the CFL2
is dimly lit. In fact, in this way, there is a substantially proportional relationship between the illuminance representing the brightness around the front window and the lighting illuminance of the CFL 2.

Note that when the area around the front window is sufficiently bright, the resistance value of the variable resistor 6 can be ignored because the photo sensor 4 becomes conductive, whereas when the area around the front window is dark, the resistance value of the variable resistor 6 decreases. The threshold voltage VSH changes depending on the value, and as a result, if the user controls the variable resistor 6 according to his/her preference, CFL2
The lighting brightness can be adjusted.

Furthermore, when the area around the front window is dark and the temperature inside the vehicle is lower than the normal temperature (for example, 0° C. to 50° C.) at which lighting is guaranteed with the rated voltage input of the CFL 2, the temperature switch 5 is turned on. . As a result, the threshold voltage VSH becomes the lowest value of 0 [V], and therefore the driving voltage VC has the highest value, and as a result, CFL2
is easily lit.

Furthermore, this temperature switch 5 is turned off when the temperature inside the vehicle rises to room temperature, and as a result, the lighting illuminance of the CFL 2 is changed by the photo sensor 4 and the variable resistor 6 as described above.
controlled by

According to the above configuration, the temperature inside the vehicle is detected by the temperature switch 5, and the inverter circuit 3 is controlled according to the detection result to control the lighting intensity of the CFL 2, so that the temperature inside the vehicle can be adjusted. The CFL 2 can reliably emit light even when the temperature is below room temperature, at which lighting is guaranteed with the rated voltage input, and thus an LCD with a backlight suitable for use in a vehicle can be realized.

In the above embodiment, the photo sensor is placed around the front window, and the brightness of the backlight is controlled in response to the brightness around the front window. However, the present invention is not limited to this, and it may be placed, for example, around the dash board in the car or at other locations.

Furthermore, in the above-mentioned embodiments, the case where the present invention is applied to a display device consisting of a vehicle-mounted LCD has been described, but the present invention is not limited to this, and can be applied to, for example, a display device of a personal computer, etc. It is widely applicable and suitable for various display devices having illumination.

[0034]

As described above, according to the present invention, the light emitting driving means is driven in accordance with the detection result of the temperature detecting means to control the light emitting operation of the light emitting means. It is possible to realize a display device that can emit light in response to the environment in an optimal manner, thereby significantly improving usability for the user.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a CFL driving device of an embodiment of a display device according to the present invention.

FIG. 2 is a connection diagram showing a circuit configuration of a CFL driving device.

[Explanation of symbols]

1... CFL drive device, 2... CFL, 3... Inverter circuit, 4... Photo sensor, 5... Temperature switch, 6
...Variable resistor, 7...PWM circuit for inverter, 8...
Transformer, Q1...Switching transistor, Q2,
Q3...Drive transistor.

Claims (1)

[Claims] 1. A display device using a predetermined light emitting means as a backlight, comprising: a light emitting driving means for causing the light emitting means to emit light; a temperature detecting means for detecting ambient temperature; . A display device comprising: a control means for driving the light emitting drive means to control the light emitting operation of the light emitting means.