JP2004260931A - Electronic apparatus driven by battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable stable operation to be conducted irrespective of a variety of condition changes at battery driving. <P>SOLUTION: This electronic apparatus is a liquid crystal display driven by the battery, and comprises: the battery 1; a voltage detection circuit 27 that detects an output voltage value VM from the battery 1; a regulator circuit 3 that converts an output voltage of the battery 1 to a proper voltage; a drive circuit 5 connected to an output of the battery 1; and a switch means 15 that switches whether to directly feed a voltage fed from the battery 1 to the drive circuit 5 from the battery 1, or to feed the voltage through the regulator circuit 3. The switch means 15 is switched depending on an output voltage of the voltage detection circuit 27. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a battery-driven electronic device using a battery as a power supply, and more particularly to a battery-driven electronic device provided with a liquid crystal display device.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, in a portable electronic device using a battery as a power source, particularly in a portable electronic device provided with a liquid crystal display device, a driving circuit of a backlight for a liquid crystal display is directly connected to a battery. Generally, in a liquid crystal television or the like, 50 to 60% of power consumption is consumed by a backlight. Therefore, power consumption by the backlight is particularly problematic.
[0003]
FIG. 13A is a functional block diagram showing a configuration example of a general battery-driven liquid crystal display device. FIG. 13B is a schematic diagram illustrating the operation of the battery, the driving circuit, and the backlight unit in FIG. 13A. In the liquid crystal display backlight, a DC voltage applied to the driving circuit is converted to a high-frequency voltage by the driving circuit. And a lamp used for a backlight, for example, is turned on.
[0004]
The liquid crystal display device illustrated in FIG. 13A includes a battery 121, a regulator circuit 123, a driving circuit 125, a backlight 127, and a liquid crystal display unit 131. The voltage is applied to the backlight drive circuit 125 after the voltage is adjusted via the regulator 123. By applying a voltage via the regulator 123, a constant voltage can be applied to the drive circuit 125.
[0005]
FIG. 12 is a block diagram illustrating a configuration of another liquid crystal display device. As shown in FIG. 12, the liquid crystal display device described in Japanese Patent Application Laid-Open No. 4-152776 has a power supply circuit 101, a battery 102, a VTR unit 105, a liquid crystal display unit 106, a backlight 107, and a lighting circuit 108. And Further, a switch 131 for selectively applying either the voltage of the power supply circuit 101 or the voltage of the battery 102 to the VTR unit 105, the liquid crystal display unit 106, and the lighting circuit 108 is provided. According to the device described in the publication, when the voltage applied to the VTR unit 105, the liquid crystal display unit 106, and the lighting circuit 108 is switched from the power supply circuit 101 to the battery 102 by the switch 131, the battery 102 is turned on. It is changed by the switch 132 so that the switching regulator 104 is interposed between the switching regulator 104 and the circuit 108. When the power supply circuit 101 is driven, a voltage is supplied to the lighting circuit 108 without passing through the regulator 104, and when switching to driving by the battery 102, the applied voltage reduced by the regulator 104 is supplied to the lighting circuit 108. You. By lowering the driving voltage applied to the lighting circuit 108 during battery driving, the battery duration during battery operation can be extended (for example, see Patent Document 1).
[0006]
[Patent Document 1]
JP-A-4-152776
[0007]
[Problems to be solved by the invention]
As shown in FIG. 13A, when a regulator is interposed between a battery and a drive circuit and a voltage is always supplied through the regulator, about 20% of power is normally lost by the regulator. In addition, the drive circuit and the backlight substantially consume about 80% of the output voltage energy of the battery, and the battery consumption is increased due to power loss caused by reduction in power supply efficiency due to the interposition of the regulator. was there.
[0008]
When a low voltage is applied to the drive circuit (lighting circuit) via the regulator only when switching to battery driving as shown in FIG. There is a problem in that a change in luminance causes a sense of incongruity.
[0009]
In addition, the brightness of the backlight greatly changes depending on the surrounding temperature, and the discharge capacity of the battery also changes depending on the surrounding temperature. Therefore, efficient backlight driving according to the ambient temperature has been demanded.
[0010]
Also, if the battery is switched without monitoring the voltage status of the battery, if the battery is defective or has been completely discharged, the fluorescent tube of the backlight will not suddenly light up due to a sudden drop in the battery voltage, There is also a problem such as insufficient brightness.
[0011]
SUMMARY OF THE INVENTION It is an object of the present invention to provide a battery-operated electronic device in which the use time of a battery is shortened due to a cause on the battery side or a change in ambient temperature, a point in which a fluorescent tube of a backlight suddenly does not light, or a sudden lack of luminance. The purpose is to solve the points and secure stable operation.
[0012]
[Means for Solving the Problems]
According to one aspect of the present invention, a battery, a regulator circuit for converting an output voltage value of the battery to an appropriate voltage, a backlight driving circuit connected to an output of the battery, and a supply voltage from the battery are provided. A switch for switching between supply from the battery directly to the drive circuit and supply through the regulator circuit; and state detection means for outputting a control signal for switching the switch. An electronic device is provided.
[0013]
In this way, the voltage input to the drive circuit is supplied directly to the battery during the operation period when the output voltage value of the battery is higher than a certain level, and is supplied through the regulator when the output voltage value of the battery drops below the certain level. Thus, the use efficiency of the battery can be improved, and a value close to the discharge starting voltage can be maintained even when the output voltage of the battery is greatly reduced.
[0014]
According to another aspect of the present invention, the control signal output from the voltage detection circuit further includes a voltage detection circuit for detecting an output voltage value from the battery and a liquid crystal backlight driven by the drive circuit. Accordingly, there is provided a battery-driven liquid crystal display device characterized by switching a switch means for switching between supply of a supply voltage from a battery directly to the drive circuit from the battery and supply of the supply voltage through the regulator circuit. Is done.
[0015]
As a result, even when the output voltage of the battery is greatly reduced, a value close to the discharge start voltage is maintained, and a change in luminance on the liquid crystal screen due to a decrease in the luminance of the backlight can be reduced.
[0016]
A battery-driven liquid crystal display device comprising a current detection circuit for detecting a lamp current value of a backlight for a liquid crystal, and switching a switch means in accordance with a control signal output from the current detection circuit; A temperature monitor for detecting a peripheral temperature of the backlight for use, a voltage detection circuit for detecting an output signal value from the temperature monitor and outputting a control signal, and a supply voltage from the battery to the drive circuit directly from the battery. Switch means for switching between supply and supply through the regulator circuit, wherein the switch means is switched by a control signal output from the voltage detection circuit. You.
[0017]
As a result, the lamp current value of the liquid crystal backlight decreases due to a decrease in the battery, or the ambient temperature of the liquid crystal backlight is detected, thereby compensating for the decrease in the battery voltage and the temperature characteristics, thereby compensating for the liquid crystal backlight. It is possible to prevent a decrease in the brightness of the light.
[0018]
As described above, according to the present invention, in a battery-driven electronic device, a point at which the battery is used for a short time due to a cause on the battery side or a change in ambient temperature, a point that the fluorescent tube of the backlight does not suddenly turn on, or a sudden It is possible to solve the problem of insufficient brightness and secure a stable operation.
[0019]
BEST MODE FOR CARRYING OUT THE INVENTION
Before describing embodiments of the present invention, considerations made by the inventor will be described first. The inventor uses a regulator circuit (voltage assurance circuit, hereinafter, referred to as "regulator") in a battery-driven electronic device such as a portable liquid crystal television device (hereinafter, referred to as "portable liquid crystal television"). The backlight fluorescent tube to the voltage at which the operation of the portable LCD TV shuts down, and keep the brightness of the LCD TV constant even if the battery voltage drops. We thought that it was important for users to keep.
Also, it has been considered that it is convenient for the user to keep the brightness of the portable liquid crystal television constant for a certain short period of time desired by the user.
In order to solve this problem, attention has been paid to a backlight driving control method that consumes much power in a liquid crystal television device.
[0020]
For example, as shown in the block diagram of FIG. 13B, in a backlight driving device, an input DC voltage is applied to a backlight driving circuit, and the driving circuit uses a step-up transformer or the like to apply a DC voltage of, for example, 1 kV or more. DC-AC conversion is performed to an AC voltage, and the AC voltage is applied to a backlight lamp. Here, the luminance of the backlight changes depending on factors such as the magnitude and frequency of the AC voltage value, the application period thereof, the current value, and the like.
[0021]
Therefore, if the DC voltage applied to the driving circuit can be constantly supplied at a constant voltage, the brightness of the backlight is preferably maintained constant. However, in the case of battery driving, the supplied DC voltage value fluctuates greatly. Therefore, it has been considered that a DC voltage value of a battery supplied to the backlight drive circuit is detected, and a regulator is used based on the detected battery voltage value to make it constant (to prevent a voltage drop). For example, when the voltage of the battery falls below a certain value, it is considered that the voltage is increased to the above-mentioned constant value by a regulator circuit. The point is that a backlight driving circuit (inverter circuit) is set according to the battery voltage (or external factors such as lamp current and temperature). 1. Drive directly without regulator or That is, either option (two options) of driving via a regulator is provided. Further, the luminance of the backlight has a characteristic that the temperature dependence is large. For example, when the temperature is extremely low, such as when a portable liquid crystal television is used outdoors at a low outside temperature, for example, when the ambient temperature is about 10 ° C., the backlight of the backlight is lower than at room temperature (25 ° C.). Since the brightness becomes as low as about 1/2, it is preferable to forcibly switch the power supply source to the regulator side to increase the brightness of the backlight. In the case of a portable liquid crystal television, portability is regarded as important, so that it is often used in an environment (outdoor) where the temperature is extremely low. In such a case, the power supply source is switched to the regulator side from the beginning of use, and the brightness can be increased regardless of the temperature characteristics (brightness reduction) of the battery and the backlight.
[0022]
For example, FIG. 2 shows an example of a discharge characteristic with respect to a temporal change of a battery voltage (V) when a portable liquid crystal television is used with a battery as a power supply. As shown in FIG. 2, when the battery is used after being charged to a full charge voltage Vo by a battery charger (not shown), the voltage drop characteristic of the battery falls to a reference value V1 close to the full charge voltage Vo. It can be broadly divided into a region to be maintained and a region to be lower than the reference value V1. For example, in a range where the battery voltage is gradually discharged from Vo and is close to V1, the battery may be directly connected to the drive circuit (inverter), and in a region where the battery voltage is lower than the reference value V1, the power supply source may be switched to the regulator. By using such control means, it is possible to keep the brightness of the backlight substantially constant up to the shutdown voltage V2 of the device. Embodiments of the present invention will be described with reference to the drawings based on the above considerations. Note that, in the following embodiments, among the liquid crystal televisions, a television tuner section, an antenna section, a channel switch section, and the like are the same as those of a general liquid crystal television. The configuration related to the above will be described.
[0023]
First, a portable liquid crystal television according to a first embodiment of the present invention will be described with reference to FIG. FIG. 1 is a diagram showing a partial configuration of a liquid crystal television according to the present embodiment. As shown in FIG. 1, a liquid crystal television according to a first embodiment of the present invention is, for example, a battery 1 for supplying a DC voltage, and the DC voltage from the battery is input, converted to an appropriate DC voltage and output. It has a regulator 3, a drive circuit 5, a backlight 7, a liquid crystal display (liquid crystal panel) 11, a switch 15, and a voltage detection circuit 27 as state detection means. The switch 15 switches the connection from the battery 1 to the drive circuit 5 by switching between the point 15a and the point 15b the connection to the drive circuit 5 that generates a drive voltage required to turn on the backlight 7 from the battery 1. Which of the direct voltage and the indirect voltage Vd1 via the regulator 3 is to be applied is selected. When the voltage of the battery 1 drops, the regulator 3 compensates for a voltage value corresponding to the voltage drop and boosts the voltage to a constant voltage Vd1. The voltage detection circuit 27 monitors the output voltage of the battery 1.
[0024]
Generally, a battery maintains its output voltage high when the power supply capacity is sufficient, such as after a full charge, but the voltage gradually decreases as the discharge proceeds, and as the discharge time increases, the battery voltage decreases. The slope of the drop in the discharge characteristics increases. The voltage detection circuit 27 detects a decrease in the battery voltage, and when detecting a predetermined voltage value (V1), outputs a signal voltage Vc1 including a switch switching command to the switch 15. At this time, the indirect voltage Vd1 boosted from the battery 1 via the regulator 3 from the battery 1 and having a voltage value substantially equal to Vo to V1 in FIG. 2 is applied to the drive circuit 5. Will be.
[0025]
Therefore, even if the output voltage from the battery 1 decreases, the voltage supplied to the drive circuit 5 is kept substantially constant, and the decrease in the brightness of the backlight 7 can be compensated. Therefore, there is an advantage that the user can always enjoy a bright display screen on the liquid crystal television until the predetermined voltage (V2) at which the operation of the device is shut down due to a decrease in the battery voltage.
Further, the voltage is directly applied from the battery 1 without passing through the regulator 3 until the output voltage from the battery 1 decreases to V1, but the voltage drop supplied to the drive circuit 5 is small because the voltage drop during this period is small. Percentage is small. Therefore, since the user visually recognizes the change in the brightness of the backlight 7 slowly, the change in the brightness of the screen of the portable liquid crystal television is small. In addition, since the power loss can be reduced by keeping the time until switching to the regulator 3 as long as possible, the power use efficiency is improved and the driving time of the battery 1 can be extended.
[0026]
Next, a liquid crystal television according to a second embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a schematic configuration diagram illustrating a partial configuration of the liquid crystal television according to the present embodiment. In the portable liquid crystal television according to the present embodiment, a current detection circuit 33 is used instead of the voltage detection circuit 27 shown in FIG. 1 as a state detection means, and detects a change in the state of the lamp current I1 flowing through the backlight 17 therein. It has detection means.
[0027]
In the portable liquid crystal television according to this embodiment, when the battery voltage decreases, the DC voltage Vd3 input to the drive circuit 25 decreases, and accordingly, the dynamic range of the AC voltage value generated by the drive circuit decreases. Therefore, it is noted that the AC voltage value applied to the backlight also decreases, and the lamp current value flowing through the backlight decreases. Here, a lamp current I1 corresponding to the luminance of the backlight 17 is detected by, for example, a current detection resistor (not shown) connected in series with the backlight 17. The current detection circuit 33 generates a voltage drop corresponding to the change in the lamp current I1 as a detection voltage, outputs the control voltage Vc3 to the switch 26, and switches the switch 26 to the regulator 23 side. At this time, the regulator 23 converts the input voltage from the battery voltage into a constant voltage value and supplies the same, so that a constant voltage-compensated DC voltage Vd3 is applied to the input of the drive circuit 25.
[0028]
According to the above configuration, when the lamp current I1 of the backlight 17 falls below a certain value, the output of the battery 21 is switched to the regulator circuit 23 side to increase the DC voltage input to the drive circuit 25, so that the backlight 17 The output drive voltage is kept substantially constant, and a decrease in the brightness of the backlight 17 can be compensated. Therefore, there is an advantage that the user can always enjoy a bright display screen regardless of a decrease in the battery voltage in the portable liquid crystal television.
[0029]
Next, a liquid crystal television according to a first modification of the second embodiment of the present invention will be described with reference to the drawings. FIG. 4 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to the present modification, and corresponds to FIG. The liquid crystal television according to the present modification has a voltage detection circuit 27 as state detection means instead of the current detection circuit 33 shown in FIG. The voltage detection circuit 27 inputs a detection signal S1 having a correlation with a temperature change from the backlight 17 side of the liquid crystal display unit 31 or a temperature monitor provided in the backlight 17, and detects a voltage value corresponding to the temperature change. And outputs the control signal Vc4.
[0030]
Here, FIG. 6 is a diagram showing typical temperature characteristics of lamp luminance and discharge starting voltage with respect to a change in ambient temperature of a lamp used for a liquid crystal backlight. As shown in FIG. 6, the brightness of the lamp depends on the ambient temperature. Assuming that the ambient temperature is set at 20% as 100%, if the ambient temperature falls below that, the lamp luminance at the same discharge starting voltage sharply decreases and becomes about 25% at 0 ° C. On the other hand, at an ambient temperature of 20 ° C. or higher, the maximum value is 125% at 35 ° C., and at an ambient temperature higher than that, the lamp brightness gradually decreases. Therefore, it is considered that the lamp luminance can be kept constant by adjusting the discharge starting voltage according to the ambient temperature.
[0031]
Note that, as shown in FIG. 6, the brightness of the lamp shows a substantially proportional characteristic when the ambient temperature is in the range of 0 ° to 30 °, so that the liquid crystal television according to the present modification corresponds to the brightness of the backlight 17. A temperature change due to irradiation heat of the related backlight 17 is detected. When the voltage value corresponding to the temperature change is detected, the control voltage Vc4 is output from the voltage detection circuit 27 to the switch 26, and the switch 26 directly drives the drive circuit 25 by the battery 21 and outputs the control voltage Vc4 through the regulator 23. Of the driving circuit 25 is switched. Here, since the regulator 23 converts the input voltage from the battery voltage into a constant voltage value and supplies the same, a constant voltage-compensated DC voltage Vd4 is applied to the input of the drive circuit 25.
[0032]
For example, the ambient temperature of the backlight 17 and the lamp luminance change in a proportional relationship, such as when the portable liquid crystal television starts to be turned on (when the power is turned on) in an environment where the battery voltage is lowered and the ambient temperature is about 20 degrees or less. In such a case, the brightness change of the screen becomes large when the ambient temperature of the backlight 17 becomes high, such as after a certain period of time has passed since the time when the ambient temperature of the backlight 17 was low when the power was turned on. Feels strange. In such a case, it is possible to forcibly switch to the regulator side only in a predetermined temperature range, and return the switch 26 to the direct connection to the battery when the ambient temperature of the backlight 17 becomes higher than the predetermined temperature.
[0033]
As described above, by combining the means for measuring the temperature around the liquid crystal display unit 31 with the temperature monitor and the regulator means for outputting a constant voltage regardless of the decrease in the battery voltage, the drive voltage output from the drive circuit 25 is substantially constant. , The brightness of the backlight 17 does not decrease. Therefore, there is an advantage that the user can always enjoy a bright display screen on the portable liquid crystal television. In the example of FIG. 4, the temperature monitor 35 is provided on the backlight side or inside thereof. However, since the backlight and the liquid crystal display section are generally provided at positions close to each other, the temperature monitor 35 may be provided on the liquid crystal display section side. Good.
[0034]
Note that an illuminometer for detecting the illuminance of the backlight 17 may be provided instead of or in addition to the temperature monitor. By detecting the illuminance of the backlight 17 with an illuminometer and adjusting the voltage Vc4 applied to the regulator according to the illuminance of the backlight 17, the brightness of the liquid crystal display unit 31 can be kept substantially constant.
[0035]
FIG. 5 is a schematic configuration diagram showing a partial configuration of a portable liquid crystal television according to a third embodiment of the present invention. As shown in FIG. 5, in the liquid crystal television according to the present embodiment, a voltage detecting circuit 27 is provided as a state detecting means. A temperature monitor 45 for measuring the ambient temperature is provided. A detection signal S2, which is an output signal from the temperature monitor 45 and is related to the ambient temperature of the backlight 17, is input to the voltage detection circuit 27. Here, the voltage detection circuit 27 has a ROM storing temperature characteristics of a backlight lamp as shown in FIG. From the ambient temperature of the backlight 17 measured by the temperature monitor and the ambient temperature dependence of the lamp luminance and the discharge start voltage shown in FIG. 6 stored in the ROM, a lamp driving voltage suitable for the current state is obtained. Then, the switch 36 is switched to the regulator 23 side so that the voltage Vd6 supplied to the drive circuit 25 is adjusted so that a lamp drive voltage suitable for the ambient temperature of the backlight is obtained along with the decrease in the battery voltage.
[0036]
Also in the embodiment of FIG. 5, the output voltage Vc6 from the voltage detection circuit 27 is input to a switch 36, which has two input systems of a direct input from a battery and an input from a regulator. The input system is switched to one according to the value of the output voltage Vc6 from the voltage detection circuit 27.
[0037]
Since the liquid crystal television according to the present embodiment has the ROM storing the temperature characteristics of the backlight (lamp), the voltage input to the switch can be easily obtained, and the data stored in the ROM can be rewritten. For example, there is an advantage that it is possible to flexibly cope with a case where different types of lamps or backlights are used.
[0038]
Note that an illuminometer for detecting the illuminance of the backlight 17 may be provided instead of or in addition to the temperature monitor. The illuminance meter detects the illuminance of the backlight 17, adjusts the output voltage of the regulator 23 based on the data stored in the ROM according to the illuminance of the backlight 17, and accurately outputs the switching determination information to the switch 36. Can be provided. Here, since the regulator 23 converts the input voltage from the battery voltage into a constant voltage value and supplies the same, a constant voltage-compensated DC voltage Vd6 is applied to the input of the drive circuit 25.
[0039]
Next, a liquid crystal television according to a fourth embodiment of the present invention will be described with reference to FIG. As shown in FIG. 7, a storage device (ROM) 38 is provided in the voltage detection circuit 27 of the liquid crystal television according to the present embodiment. The ROM 38 stores the discharge temperature characteristics of the battery 21 shown in the example of FIG. 8 (a: temperature characteristics of battery discharge capacity and battery voltage) and (b: temperature characteristics of battery discharge time and battery voltage value). The regulator 23 is appropriately switched based on the temperature around the battery measured by the temperature monitor 41 and the discharge temperature characteristics stored in the ROM 38.
[0040]
Since the liquid crystal television according to the present embodiment has a ROM storing the discharge temperature characteristics of the battery 21 as described above, the output voltage Vc5 from the voltage detection circuit 27 is used to drive the drive circuit 25 via the switch 46. There is an advantage that the timing for switching the power supply can be accurately and easily obtained.
[0041]
The remaining capacity of the battery 21 can be calculated by predicting the relationship between the terminal voltage (or discharge current) of the battery and the ambient temperature from the discharge temperature characteristics shown in FIG. Therefore, for example, the drive circuit is connected to the drive circuit via the regulator for a specific short time (for example, about several tens of minutes to about one hour) predetermined based on the remaining capacity of the battery 21 from the ambient temperature and the battery voltage value at a certain point in time. It is also possible to supply a constant voltage. For example, under the condition that the user takes out the portable LCD TV to the yard of his house and desires to be able to operate the battery only for several tens of minutes, for example, the brightness of the backlight is set to the maximum brightness within the remaining capacity of the battery 21. It is also possible to set to keep it constant (bright).
[0042]
Next, a liquid crystal television according to a fifth embodiment of the present invention will be described with reference to FIG. As shown in the figure, the liquid crystal television according to the present embodiment has first and second two batteries 51 and 52. Which battery is used can be selected by a switch 55. The voltage detection circuit 27 detects at least the output voltage of the currently used battery among the output voltages VM11 and VM12 of the first battery 51 and the second battery 52, and drives the battery based on the output voltage. The control voltage Vc7 is supplied to the switch 56 so that the output voltage from the circuit 25 becomes substantially constant, and the mode is switched between power supply from the battery and power supply via the regulator 53. For example, when the voltage of the first battery 51 decreases to near the shutdown voltage V2 in FIG. 2, the connection to the second battery 52 is switched using the switch 55 before the shutdown operation is performed. Thus, there is an advantage that the operation of the portable liquid crystal television can be continued for a long time even if any of the battery capacities suddenly decreases.
[0043]
In the embodiment of FIG. 9, two batteries are used. However, by using two or more batteries and switching them in order, a longer operation is possible. Alternatively, the use order of the first and second batteries may be alternately used so that the battery capacity of each battery is reduced as evenly as possible. For example, a comparator using the output voltages VM11 and VM12 from the batteries 1 and 2 as input values is incorporated in either the switch 55 or the voltage detection circuit 27, and the switch 55 is switched based on the comparison result from the comparator. Consider the configuration. Then, by switching the signal of the comparator every time the difference between the two voltage values reaches a certain value, the switch 55 is switched to switch between the first and second batteries. Thus, it is possible to provide a liquid crystal display device that does not cause extreme luminance fluctuation on the screen from the start of lighting to the end of discharge of two batteries.
[0044]
Next, a partial configuration of a liquid crystal television according to a sixth embodiment of the present invention will be described with reference to the drawings. FIG. 10 is a diagram showing a configuration example of the liquid crystal television according to the present embodiment. As shown in FIG. 10, the liquid crystal television according to the present embodiment has one set of one battery (61, 62) and one regulator circuit (63, 64), and a plurality of these sets (two sets in FIG. 10). One drive circuit (inverter circuit) 25 is connected to the prepared set of power supply circuits (61, 63 or 62, 64), and the voltage of the battery to be used is detected by the voltage detection circuit 27. The power supply circuit that actually applies the voltage to the backlight 17 via the drive circuit 25 from among the plurality of power supply circuits (61, 63 or 62, 64) is switched by the switch 67 in response to the decrease of the battery (Vc8). And Vc9) are also possible. By switching between a plurality of batteries and a regulator as described above, the same type or different types of batteries can be used together, and a liquid crystal television can be enjoyed on a bright screen for a long time.
[0045]
The technology according to the present embodiment is applicable to the liquid crystal television according to each of the first to fourth embodiments. Of course, as long as the number of batteries is two or more, the number is not limited within a practical range. Further, if one is a main battery having a large battery capacity and the other is a sub-battery, that is, a small-capacity battery or a spare battery for rescue, a configuration is employed in which the voltage is not lowered to the end as in the liquid crystal television according to the present embodiment. As a result, even if the power consumption is large and the battery capacity suddenly decreases, the operation is maintained for a short time by the sub-battery, and if the main battery is replaced in the meantime, the driving of the LCD TV can be watched without interruption can do.
[0046]
Next, a configuration of a liquid crystal television according to a seventh embodiment of the present invention will be described with reference to FIG. FIG. 11 is a diagram illustrating an example of the configuration of the liquid crystal television according to the first embodiment of the present invention illustrated in FIG. 1, in which DC power to be supplied to a drive circuit is supplied from an AC power supply via an AC adapter 39 or supplied from a battery. An example is shown in which a switch 75 (switching is performed by the microcomputer 37) for switching whether to do so is provided. FIG. 11 shows an example in which the configuration is applied to the first embodiment. However, the configuration in FIG. 11 can be applied to the liquid crystal televisions according to the second to sixth embodiments.
[0047]
According to the embodiment shown in FIG. 11, the power supplied to the drive circuit in accordance with the instruction of the microcomputer 37 in accordance with the power supply situation can be switched between the AC power supply 39 and the battery 1 as appropriate.
[0048]
In the above-described embodiment, the control signal generated by the voltage detection circuit or the current detection circuit is used only for switching of the switch means for switching between the direct connection to the battery and the regulator side. And the DC voltage value generated by the regulator can be controlled to be changed according to various environmental conditions.
[0049]
As the backlight dimming method, there are methods such as voltage dimming, duty dimming, and current dimming, but the liquid crystal television according to the present embodiment can be applied to any dimming method. Needless to say,
Further, although the description has been made using the lamp as the backlight, it is obvious that the present invention can be applied to a backlight device using, for example, an LED.
[0050]
Further, in the present embodiment, a portable liquid crystal television has been described as an example, but the present invention is also applied to a battery-driven electronic device including a liquid crystal display device such as a notebook personal computer (PC) or a mobile phone. it can. Further, the present invention can be applied to a portable electronic device having no liquid crystal display device and a battery-driven electronic device. In addition, both AC driving and battery driving can be used by switching, and the means of the present embodiment can be used at the time of battery driving. As described above, the liquid crystal television according to each embodiment has been specifically described. However, it is needless to say that the present invention is not limited to the above embodiment, and various modifications are possible.
[0051]
【The invention's effect】
As described above, in the electronic device according to the present invention, stable operation is enabled and battery use efficiency is improved irrespective of changes in various conditions when the battery is driven. Further, according to the liquid crystal display device of the present invention, the drive voltage supplied to the backlight drive circuit based on the voltage value supplied from the battery, the operating temperature or the current value flowing through the backlight is controlled by a battery directly connected drive or via a regulator. A high-quality liquid crystal display device that can prolong the operation time of the battery and suppress a change in screen brightness regardless of a decrease in the battery voltage because it is possible to appropriately control whether the battery is driven or not. can do.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a partial configuration of a liquid crystal television according to a first embodiment of the present invention.
FIG. 2 is a diagram showing an example of a discharge characteristic of a battery voltage (V).
FIG. 3 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a second embodiment of the present invention.
FIG. 4 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a modification of the second embodiment of the present invention.
FIG. 5 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a third embodiment of the present invention.
FIG. 6 is a diagram showing typical temperature characteristics of lamp luminance and discharge starting voltage in a liquid crystal backlight lamp.
FIG. 7 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a fourth embodiment of the present invention.
FIG. 8 is a diagram illustrating an example of a discharge temperature characteristic of a battery.
FIG. 9 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a fifth embodiment of the present invention.
FIG. 10 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a sixth embodiment of the present invention.
FIG. 11 is a schematic configuration diagram showing a partial configuration of a liquid crystal television according to a seventh embodiment of the present invention.
FIG. 12 is a block diagram showing a configuration of a liquid crystal display device described in JP-A-4-152776.
13A and 13B are functional blocks illustrating a configuration example of a general battery-driven liquid crystal display device, and a diagram illustrating an operation outline of a drive circuit.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Battery, 3 ... Regulator circuit, 5 ... Drive circuit, 7 ... Backlight, 11 ... Liquid crystal display part, 15, 26, 36, 46, 55, 56, 65, 66, 67, 75 ... Switch, 27 ... Voltage detection circuit, 33: current detection circuit, 35: temperature monitor, 37: microcomputer, 39: AC adapter.

Claims (10)

Battery powered electronic equipment,
Battery and
A regulator circuit for converting an output voltage value of the battery into an appropriate voltage;
A drive circuit for a backlight connected to the output of the battery;
Switch means for switching whether the supply voltage from the battery is supplied directly from the battery to the drive circuit or through the regulator circuit;
A battery-driven electronic device comprising: a state detection unit that outputs a control signal for switching the switch unit. A battery-operated liquid crystal display device,
Battery and
A voltage detection circuit for detecting an output voltage value from the battery;
A regulator circuit for converting an output voltage value of the battery into an appropriate voltage;
A drive circuit for a backlight connected to the output of the battery;
A liquid crystal backlight driven by the drive circuit, and switch means for switching between supply of a supply voltage from the battery to the drive circuit directly from the battery or supply through the regulator circuit,
A liquid crystal display device driven by a battery, wherein the switch means is switched by a control signal output from the voltage detection circuit. A battery-operated liquid crystal display device,
Battery and
A regulator circuit for converting an output voltage value of the battery into an appropriate voltage;
A drive circuit for a backlight connected to the output of the battery;
A liquid crystal backlight driven by the driving circuit;
A current detection circuit for detecting a lamp current value of the liquid crystal backlight;
Switch means for switching whether the supply voltage from the battery is supplied directly from the battery to the drive circuit or supplied through the regulator circuit,
A liquid crystal display device driven by a battery, wherein the switch means is switched by a control signal output from the current detection circuit. A battery-operated liquid crystal display device,
Battery and
A regulator circuit for converting an output voltage of the battery to an appropriate voltage;
A drive circuit for a backlight connected to the output of the battery;
A liquid crystal backlight driven by the driving circuit;
A temperature monitor for detecting an ambient temperature of the liquid crystal backlight;
A voltage detection circuit that detects an output signal value from the temperature monitor and outputs a control signal;
Switch means for switching whether the supply voltage from the battery is supplied directly from the battery to the drive circuit or supplied through the regulator circuit,
A liquid crystal display device driven by a battery, wherein the switch means is switched by a control signal output from the voltage detection circuit. A battery-operated liquid crystal display device,
Battery and
A regulator circuit for converting an output voltage value of the battery into an appropriate voltage;
A drive circuit for a backlight connected to the output of the battery;
A liquid crystal backlight driven by the driving circuit;
A temperature monitor for detecting an ambient temperature of the liquid crystal backlight;
A voltage detection circuit that detects an output signal value from the temperature monitor and outputs a control signal;
Switch means for switching whether the supply voltage from the battery is supplied directly from the battery to the drive circuit or supplied through the regulator circuit,
By a control signal output from the voltage detection circuit based on the temperature measured by the temperature monitor and at least one or both of the temperature characteristics of the luminance of the lamp of the liquid crystal backlight or the discharge starting voltage of the lamp, A battery-driven liquid crystal display device characterized by switching the switch means. 6. The liquid crystal display device according to claim 5, further comprising storage means for storing temperature characteristics of one or both of a lamp luminance and a lamp discharge starting voltage with respect to an ambient temperature of the liquid crystal backlight. A battery-operated liquid crystal display device,
Battery and
A voltage detection circuit for detecting an output voltage value from the battery;
A temperature monitor for detecting an ambient temperature of the battery;
A regulator circuit for converting an output voltage value of the battery into an appropriate voltage;
A drive circuit for a backlight connected to the output of the battery;
A liquid crystal backlight driven by the driving circuit;
Switch means for switching whether the supply voltage from the battery is supplied directly from the battery to the drive circuit or supplied through the regulator circuit,
The temperature measured by the temperature monitor and the output voltage of the battery are input to the voltage detection circuit, and the remaining voltage based on the temperature characteristics is determined by the voltage detection circuit based on the respective input information. A battery-driven liquid crystal display device, wherein the switch means is switched according to a control signal output from a detection circuit. The liquid crystal display device according to claim 7, further comprising a storage unit configured to store a temperature characteristic between a discharge capacity or a discharge time of the battery and a battery voltage. Has at least a plurality of batteries,
9. A switch according to claim 1, further comprising a switch for switching an output to said drive circuit from said battery to said another battery when a remaining capacity of a battery connected to said drive circuit becomes a predetermined value or less. The liquid crystal display device according to any one of the above items. The liquid crystal display device according to any one of claims 1 to 9, further comprising a plurality of sets each of the battery, the regulator, and the switch means.

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