JP2001175184A - Backlight drive for liquid crystal display - Google Patents

Abstract

[PROBLEMS] To provide a liquid crystal display device capable of coping with heat generation of a power supply circuit without requiring the use of a heat sink mounted on a power semiconductor element or an unnecessarily large power semiconductor element. A backlight driving device is provided. In the backlight drive device, an air conditioner is turned on in accordance with the start of an engine, and a part of air supplied from the air conditioner for controlling a temperature in a vehicle compartment is determined by a ventilation duct. Voltage circuit 2
It is designed to be guided to zero. In addition, the temperature sensor 2
Based on the detection results of the ventilation ducts 30a, 3
By adjusting the air flow regulating valves 31a and 31b provided in the valve 0b, the temperature in the vehicle compartment and the ambient temperature T1 of the constant voltage circuit 20 can be independently adjusted to appropriate temperatures.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a backlight driving device for a vehicle-mounted liquid crystal display device.

[0002]

2. Description of the Related Art An on-vehicle battery power supply is frequently charged and discharged with a large current, so that the output voltage tends to be unstable. For this reason, many backlight driving devices for in-vehicle liquid crystal display devices use a constant voltage circuit (power supply circuit) to stabilize the voltage applied to the backlight. The constant voltage circuit uses a power semiconductor element such as a three-terminal regulator and a transistor. In general, power semiconductor elements generate heat and change in characteristics due to temperature changes. Therefore, it is necessary to take some measures such as temperature management. For example, in a power semiconductor device, an applied voltage due to a temperature rise exceeds a rated voltage due to derating (rating reduction) due to a temperature rise, and the device may be destroyed.

On the other hand, in a conventional backlight driving device for a liquid crystal display device, an external heat sink is attached to a power semiconductor element of a constant voltage circuit to suppress a temperature rise, and to reduce an applied voltage. On the other hand, by using a power semiconductor device with a large capacity that has enough room,
It supports derating due to temperature rise.

[0004]

However, in the conventional backlight driving device, the occupation area of the heat sink mounted on the power semiconductor element on the substrate is large, so that the arrangement position of the power semiconductor element on the substrate is limited. Therefore, there is a problem that the degree of freedom of the board design is greatly limited. In addition, since the mounting of the heat sink is generally performed manually by an operator, such as by screwing or bonding, the manufacturing process of the backlight driving device is complicated, and automation of the manufacturing process is required. There is also a problem that is hindering.

Further, in the conventional backlight driving device, a power semiconductor element having a larger capacity than necessary is used to cope with derating due to a rise in temperature. There is also a problem that the cost is increased.

In a liquid crystal display device using a cold-cathode tube as a backlight, a heater for heating is mounted on the backlight to adjust the temperature of the backlight in order to correct luminance at low temperatures. Although there is already a device that actively controls the temperature of the power supply circuit itself of the backlight driving device as in the present invention, it is not yet known.

In view of the above problems, the present invention can cope with heat generation of a power supply circuit without requiring the use of a heat sink mounted on a power semiconductor element or an unnecessarily large power semiconductor element. It is an object of the present invention to provide a backlight driving device for a liquid crystal display device that can be used.

[0008]

A technical means for achieving the above object is a backlight driving device of a liquid crystal display device mounted on a vehicle, wherein the backlight driving device is stabilized by the backlight of the liquid crystal display device. A power supply circuit having a power semiconductor element for supplying power, an air conditioner for supplying temperature-regulated air into the vehicle interior, and an air conditioner for controlling the temperature in the vehicle interior to a predetermined set temperature that is set by operation. Air-conditioning control means for controlling an air conditioner; and a first ventilation duct for guiding air temperature-controlled by the air conditioner from the air conditioner into the vehicle interior, and branching from the air conditioner. A second ventilation duct for guiding a part of the air guided into the vehicle interior through the one ventilation duct toward the power supply circuit.

Preferably, the backlight driving device of the liquid crystal display device further includes a temperature measuring means provided near the power supply circuit and measuring a peripheral temperature of the power supply circuit, and the air conditioning control means comprises: When the set temperature is set, the air conditioner is controlled based on the set temperature, while when the set temperature is not set, the ambient temperature of the power supply circuit measured by the temperature measuring means. It is preferable to control the air conditioner so as to keep the temperature within a predetermined appropriate temperature range.

Preferably, the backlight driving device for the liquid crystal display device is provided near the power supply circuit, and measures temperature around the power supply circuit; First and second air volume adjustment valves provided in the second ventilation duct, respectively, for controlling air volume guided to the vehicle interior and the power supply circuit through the two ventilation ducts under the control of the air conditioning control means; The air-conditioning control means is measured by the temperature measurement means so as to maintain the temperature in the vehicle interior at the set temperature and to maintain the ambient temperature of the power supply circuit within a predetermined appropriate temperature range. Preferably, the air conditioner and the first and second air volume adjusting valves are controlled based on the ambient temperature of the power supply circuit and the set temperature.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Generally, it is necessary to display predetermined information to a driver or the like by a liquid crystal display device or the like in the interior of an automobile when the engine of the automobile is operating. During the operation of the engine, it is sufficiently possible to operate the air conditioner mounted on the vehicle (so-called air conditioner mounted on the vehicle) in terms of electric load capacity. Therefore, each embodiment described below is configured such that the ambient temperature of the power supply circuit of the backlight driving device of the liquid crystal display device becomes an appropriate temperature by using an air conditioner mounted on an automobile. .

<First Embodiment> FIG. 1 shows a backlight driving device 10 for a liquid crystal display device according to a first embodiment of the present invention.
FIG. This backlight driving device 10
0 denotes an air conditioner 10 that adjusts the temperature in the cabin of the vehicle to a predetermined set temperature that is set by operation; an air conditioning control unit (air conditioning control unit) 70 that controls the air conditioner 10; The air conditioner 10 includes a constant voltage circuit (power supply circuit) 20 for driving a backlight 13 of the liquid crystal display device 11 for displaying predetermined information to a driver or the like. A ventilation duct 30 leading to the place is arranged. In the present embodiment, the ventilation duct 30 includes a first ventilation duct 30a for guiding the air, the temperature of which has been adjusted by the air conditioner 10, to the vehicle interior side;
It is configured to branch into a second power supply circuit ventilation duct 30b for leading to the constant voltage circuit 20.

Here, the liquid crystal display device 11 comprises a liquid crystal display element 12 in which polarizing plates are attached to both sides of a liquid crystal panel.
A backlight (here, a bulb) 13, a light box 14 for guiding the light of the backlight 13 toward the liquid crystal display element 12, and a diffusion plate 15 provided on the back side of the liquid crystal display element 12. It is provided with. In the present embodiment, the backlight 13 is provided on the same substrate 16 as the constant voltage circuit 20.

The constant voltage circuit 20 is for supplying a constant voltage to the backlight 13 to drive the backlight 13. The constant voltage circuit 20 includes a power semiconductor device such as a three-terminal regulator and a transistor. Constant voltage circuit 2
The substrate 16 on which 0 is disposed is installed on a panel internal space side different from the vehicle interior side blocked by an instrument panel (hereinafter simply referred to as “panel”).
When a transistor is used as the power semiconductor element, the constant voltage circuit 20 is configured to include the transistor and the Zener diode.

FIG. 2 is a diagram showing a main part around the constant voltage circuit 20. As shown in FIG. As shown in FIG. 2, a region where the constant voltage circuit 20 is provided on the substrate 16 is surrounded by a substantially cylindrical heat insulating material 22 attached to the end of the ventilation duct 30b. A temperature sensor (temperature measuring means) 23 for detecting a peripheral temperature of the constant voltage circuit 20 is provided near the constant voltage circuit 20 in a region surrounded by the heat insulating material 22. Here, the temperature sensor 23 is provided on the substrate 16. Here, an exhaust port for exhausting the air guided from the ventilation duct 30b to the outside of the heat insulating material 22 is formed as needed in a portion near the constant voltage circuit 20 in the heat insulating material 22.

Such a heat insulating material 22 causes the temperature around the constant voltage circuit 20 to rise even when the temperature on the vehicle interior side or the panel internal space side rises or falls during traveling or the like. It is provided to prevent dripping or falling. For example, even when the temperature of the internal space of the panel becomes about 40 ° C. when the automobile is running, since the heat insulating material 22 is provided, the constant voltage circuit 20
Can be suppressed to less than 40 ° C.

On the vehicle interior side, a temperature setting input unit 50 for operating and inputting a vehicle interior set temperature T3 desired by a driver or the like, and a vehicle interior temperature sensor 6 for detecting the vehicle interior temperature T2.
0 is provided.

Returning to FIG. 1, an air conditioner control unit 70 is electrically connected to the air conditioner 10, and the air conditioner control unit 70 sends an operation control signal CNT1 to the air conditioner 10 so that air is controlled. Operation control of the harmony machine 10 is performed.

The ambient temperature T1 of the constant voltage circuit 20 detected by the temperature sensor 23, the set temperature T3 input to the temperature setting input unit 50, and the vehicle interior temperature T2 detected by the vehicle interior temperature sensor 60 Are transmitted to the air-conditioning control unit 70, respectively. The air conditioning control unit 70 detects the start and stop of the engine based on signals from an ignition switch, a regulator attached to the generator, and the like, and turns on the air conditioner 10 with the start and stop of the engine. , Also has a function of turning off.

In the above configuration, the air-conditioning control unit 7
0 controls the operation of the air conditioner 10 as follows.

The air-conditioning control unit 70 turns on the air conditioner 10 when the engine is started, and when the driver or the like inputs a desired set temperature T3 from the temperature setting input unit 50, the air-conditioning control unit 70 turns on the cabin. The operation of the air conditioner 10 is controlled so that is set to the set temperature T3. That is, when a driver or the like inputs a desired set temperature T3 to the temperature setting input unit 50,
The air-conditioning control unit 70 sets the set temperature T3 and the vehicle interior temperature sensor 60.
The air conditioner 10 is operated so that the difference from the vehicle interior temperature T2 detected by the air conditioner disappears. As a result, the air sent from the air conditioner 10 is guided into the vehicle interior via the ventilation duct 30a, and is also guided to the constant voltage circuit 20 via the ventilation duct 30b.

Generally, the temperature at which a person feels comfortable is about 25 ° C., though there are individual differences. For this reason, when the driver or the like inputs the set temperature T3 in the vehicle interior, the set temperature T3 is often about 25 ° C. Even if the set temperature T3 is set to 25 ° C. or higher, the set temperature T3 is generally within a predetermined temperature range (for example, within a range of 18 to 32 ° C.). Are not hot enough to cause significant effects.

On the other hand, when the driver or the like does not input the set temperature T3, the air-conditioning controller 70 determines that the ambient temperature T1 of the constant voltage circuit 20 detected by the temperature sensor 23 is suitable for the operation of the constant voltage circuit 20. Appropriate temperature (for example, about 25 ° C)
The operation of the air conditioner 10 is controlled so that That is, when the driver or the like does not operate the air conditioner 10 and the ambient temperature T1 of the constant voltage circuit 20 is higher or lower than the appropriate temperature, the air conditioning control unit 70 The air conditioner 10 is operated to set the ambient temperature T1 of the constant voltage circuit 20 to the appropriate temperature on the basis of the ambient temperature T1 detected by (1). As a result, when the driver or the like does not operate the air conditioner 10, the ambient temperature T1 of the constant voltage circuit 20 can be set to an appropriate temperature.

As described above, according to the present embodiment, the air conditioner 10 is turned on when the engine is started, and a part of the air supplied from the air conditioner 10 that regulates the temperature in the vehicle compartment is supplied to the ventilation duct. 30b, the temperature of the constant voltage circuit 20 is set within a certain temperature range (for example,
(In the range of 18 to 32 ° C.), whereby the heat sink attached to the power semiconductor element is omitted, and the degree of freedom in designing the substrate 16 on which the constant voltage circuit 20 is disposed is improved. And simplification and automation of the manufacturing process. Also, since it is not necessary to consider the effects of temperature derating, it is not necessary to use a power semiconductor element larger than necessary as in the past, and a power semiconductor element with an optimum capacity can be used, The circuit 20 can be reduced in size and cost.

When the temperature of the air conditioner 10 is not set by the driver or the like, the ambient temperature T1 of the constant voltage circuit 20 is adapted to the operation of the constant voltage circuit 20 based on the detection result of the temperature sensor 23. Thus, the power can be supplied to the backlight 13 more stably.

Further, there is an advantage that the temperature of the constant voltage circuit 20 can be adjusted using the existing air conditioner 10.

<Second Embodiment> FIG. 3 shows a backlight driving device 10 for a liquid crystal display device according to a second embodiment of the present invention.
It is a block diagram showing 0a. In FIG. 3, members having the same functions as those shown in FIG. 1 are denoted by the same reference numerals, and descriptions of those members will be omitted. Further, in FIG. 3, the installation form of the constant voltage circuit 20 is the same as that of FIG.

The backlight driving device 100a shown in FIG.
The configuration of the backlight drive device 100 is different from that of the backlight drive device 100 in that a first air volume adjustment valve 31a is provided in the ventilation duct 30a for adjusting the air volume when the air temperature-controlled by the air conditioner 10 is guided to the vehicle interior side. A second air flow control valve 31b is provided in the ventilation duct 30b to control the air flow when the air temperature-controlled by the air conditioner 10 is guided to the constant voltage circuit 20, and the air conditioning control is provided. An air flow control unit 80 that controls the air flow adjusting valves 31a and 31b under the control of the unit 70 is provided.

The air volume adjusting valve 31a performs a rotating operation in the ventilation duct 30a based on a control signal FC1 from the air volume control section 80, and adjusts the air volume of the air introduced into the vehicle interior to an arbitrary value. Further, the air volume control valve 31b is provided with an air volume control unit 80.
A rotation operation is performed in the ventilation duct 30b based on the control signal FC2 from the controller, and the amount of air guided to the constant voltage circuit 20 is adjusted to an arbitrary value.

The air volume control unit 80 controls the air volume adjusting valves 31a, 31a based on the air volume control signal CNT2 from the air conditioning control unit 70.
Control signals FC1 and FC2 are transmitted to each of the airflow ducts 1b, and the airflow guided from the ventilation duct 30a to the vehicle interior side and the airflow guided to the constant voltage circuit 20 from the ventilation duct 30b are independently controlled.

In such a configuration, when the temperature is set through the temperature setting input section 50, the air-conditioning control section 70 turns on the air conditioner 10 with the start of the engine, and the vehicle interior temperature sensor The temperature T2 in the vehicle compartment detected by the temperature sensor 60 is maintained at the set temperature T3, and the temperature T1 around the constant voltage circuit 20 detected by the temperature sensor 23 is maintained at an appropriate temperature (for example, 25 ° C.).
Based on the ambient temperature T1 of the constant voltage circuit 20 and the set temperature T3, the air conditioner 10 and the two air volume adjusting valves 31a, 3
1b. On the other hand, when the temperature is not set through the temperature setting input unit 50, the air-conditioning control unit 70
0 is turned on and the constant-voltage circuit 2 detected by the temperature sensor 23 in a state where the air volume regulating valve 31b is kept open.
The air conditioner 10 is controlled so as to maintain the zero ambient temperature T1 at an appropriate temperature. In this case, the air volume control valve 31a may be open, but is preferably closed to suppress energy consumption.

Various methods can be considered as a control method performed by the air-conditioning control unit 70 when the temperature is being set, and the following method can be considered as an example.

At the time of cooling, if the set temperature T3 is set lower than the appropriate temperature of the constant voltage circuit 20, the air conditioner 10 is operated to set the temperature T2 in the vehicle compartment to the set temperature T3. On the other hand, the constant voltage circuit 2
Until the ambient temperature T1 of 0 becomes an appropriate temperature, both air volume adjusting valves 31a and 31b are kept open. When the ambient temperature T1 becomes an appropriate temperature, the first air volume adjusting valve 31a is opened. , The second air volume adjusting valve 31b is closed. Then, the air conditioner 10 is operated so that the temperature T2 in the vehicle compartment is set to the set temperature T3 in a state where the ambient temperature is prevented from falling below the appropriate temperature, and the temperature T2 in the vehicle compartment is adjusted to the set temperature T3. Is done. However, the second air volume control valve 31
“b” is appropriately opened even after the ambient temperature T3 has reached an appropriate temperature to prevent the ambient temperature T3 from rising.

On the other hand, when the set temperature T3 is set higher than the proper temperature of the constant voltage circuit 20, the air conditioner 1 sets the ambient temperature T1 of the constant voltage circuit 20 to the proper temperature.
0 is operated, while the temperature T2 in the vehicle interior is set to the set temperature T3.
At this time, the first air flow control valve 31a is closed with the second air flow control valve 31b opened, so that the temperature T2 in the vehicle compartment is prevented from dropping below the set temperature T3. It has become.

During heating, if the set temperature T3 is set higher than the proper temperature of the constant voltage circuit 20, the air conditioner 10 operates to set the temperature T2 in the passenger compartment to the set temperature T3. On the other hand, from the start of heating to the time when the ambient temperature T1 of the constant voltage circuit 20 reaches the appropriate temperature, both the air volume regulating valves 31a and 31b are kept open. When the ambient temperature T1 reaches the appropriate temperature, the first Air flow control valve 31a
Is opened, the second air volume adjusting valve 31b is closed. Then, in a state in which the ambient temperature is prevented from rising to an appropriate temperature or more, the air conditioner 10 is operated to set the temperature T2 in the vehicle compartment to the set temperature T3, and the temperature T2 in the vehicle compartment is adjusted to the set temperature T3. Is done. However, the second air flow control valve 3
1b is appropriately opened even after the ambient temperature T3 has reached an appropriate temperature to prevent the ambient temperature T3 from dropping.

On the other hand, when the set temperature T3 is set lower than the proper temperature of the constant voltage circuit 20, the air conditioner 1 sets the ambient temperature T1 of the constant voltage circuit 20 to the proper temperature.
0 is operated, while the temperature T2 in the vehicle interior is set to the set temperature T3.
At this point, the first airflow control valve 31a is closed with the second airflow control valve 31b opened, so that the temperature T2 in the vehicle compartment is prevented from rising to the set temperature T3 or higher. It has become.

Note that the air volume control unit 80 is
When closing the air volume regulating valves 31a, 31b provided in the a, 30b, the ventilation ducts 30a, 30b are not completely closed, and the vehicle interior temperature T2 or the peripheral temperature T1 of the constant voltage circuit 20 is set to a set temperature or an appropriate temperature. A small amount of constant air volume may be supplied to the vehicle interior or the constant voltage circuit 20 so that the air volume can be kept constant.

As described above, in the backlight driving device 100a having the configuration of FIG. 3, the set temperature T3 set by the driver or the like is set.
Is set to, for example, 18 ° C. or 30 ° C., the air-conditioning control unit 70 and the air volume control unit 80 operate to maintain the ambient temperature T1 of the constant voltage circuit 20 at an appropriate temperature, T2 can be maintained at a set temperature (18 ° C., 30 ° C., etc.) T3. Therefore, the temperature T in the vehicle compartment
Regardless of 3, the ambient temperature T1 of the constant voltage circuit 20 can be maintained at an appropriate temperature.

Here, at the time of starting the engine or the like, it is possible to prevent the air (for example, high-temperature air) in the ventilation duct 30 from being blown to the constant voltage circuit 20 before the temperature is adjusted particularly in summer or the like. Therefore, it is preferable that the ventilation duct 30b be closed by the air volume control valve 31b for a predetermined time (time until the temperature of the air in the ventilation duct 30 is adjusted) from the start of the engine.

As described above, according to the present embodiment, the first
Almost the same effects as those of the embodiment can be obtained, and the surrounding temperature T1 of the constant voltage circuit 20 can be adjusted to an appropriate temperature independently of the temperature T2 in the vehicle compartment, so that the power supply by the constant voltage circuit 20 is more stabilized. Can be done.

[0041]

According to the first aspect of the invention, a part of the air supplied from the air conditioner for controlling the temperature in the vehicle compartment is guided to the power supply circuit by the second ventilation duct. Therefore, the temperature of the power supply circuit can be maintained within a certain temperature range (for example, within a range of 18 to 32 ° C.) corresponding to the set temperature in the vehicle interior, and thereby, the radiator plate attached to the power semiconductor can be maintained. By omitting it, the degree of freedom in designing the substrate on which the power supply circuit is provided can be improved, and the manufacturing process can be simplified and automated. Also,
Since there is no need to consider the effects of temperature derating, it is not necessary to use a power semiconductor element larger than necessary as in the past, a power semiconductor element with the optimum capacity can be used, and the power supply circuit can be reduced in size. And cost reduction.

Another advantage is that the temperature of the power supply circuit can be adjusted using existing air conditioning means.

According to the second aspect of the present invention, there is further provided a temperature measuring means which is provided near the power supply circuit and measures the peripheral temperature of the power supply circuit. While controlling the air conditioner based on the set temperature, if the set temperature is not set, the ambient temperature of the power supply circuit measured by the temperature measuring means is maintained within a predetermined appropriate temperature range. Since the air conditioner is controlled, the temperature of the power supply circuit can be adjusted with a relatively simple configuration.

According to the third aspect of the present invention, the temperature inside the vehicle compartment can be maintained at the set temperature, and the temperature around the power supply circuit can be kept within a predetermined appropriate temperature range. Can be maintained within an appropriate temperature range.

[Brief description of the drawings]

FIG. 1 is a configuration diagram illustrating a backlight driving device of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a main part around a constant voltage circuit provided in the backlight driving device of FIG. 1;

FIG. 3 is a configuration diagram illustrating a backlight driving device of a liquid crystal display device according to a second embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 Air conditioner 11 Liquid crystal display device 13 Backlight 20 Constant voltage circuit 22 Insulation material 23 Temperature sensor 30, 30a, 30b Ventilation duct 31a, 31b Air flow control valve 70 Air conditioning control unit 80 Air flow control unit 100, 100a Back of liquid crystal display device Light drive

Claims (3)

[Claims] 1. A backlight driving device for a liquid crystal display device mounted on a vehicle, comprising: a power supply circuit including a power semiconductor element for supplying stabilized power to the backlight of the liquid crystal display device; An air conditioner that supplies temperature-controlled air into a vehicle interior; an air conditioning control unit that controls the air conditioner so that the temperature in the vehicle interior becomes a predetermined set temperature that is set by operation; A portion of the air that is branched from a first ventilation duct for guiding the temperature-controlled air from the air conditioner into the vehicle interior and that is guided from the air conditioner to the interior of the vehicle through the first ventilation duct. And a second ventilation duct for guiding toward the power supply circuit. 2. The backlight driving device for the liquid crystal display device further includes a temperature measurement unit provided near the power supply circuit and measuring a peripheral temperature of the power supply circuit. If the temperature is set, the air conditioner is controlled based on the set temperature, while if the set temperature is not set, the ambient temperature of the power supply circuit measured by the temperature measurement unit is set. The backlight driving device for a liquid crystal display device according to claim 1, wherein the air conditioner is controlled so as to be maintained within a predetermined appropriate temperature range. 3. A backlight driving device for the liquid crystal display device, comprising: a temperature measurement unit provided near the power supply circuit for measuring a peripheral temperature of the power supply circuit; A first and a second air volume adjustment valve provided in each of the ventilation ducts and configured to adjust the air volume of air guided to the vehicle interior and the power supply circuit through the two ventilation ducts under the control of the air conditioning control means. The air conditioning control unit is configured to maintain the temperature in the vehicle cabin at the set temperature and to maintain the ambient temperature of the power supply circuit within a predetermined appropriate temperature range. The liquid according to claim 1, wherein the air conditioner and the first and second air volume adjustment valves are controlled based on a peripheral temperature of a circuit and the set temperature. Backlight driving device for crystal display device.