JP2005347141A - Driving device and driving method of electroluminescent device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To extend the life of an electroluminescent device by control based on various elements determining the life. <P>SOLUTION: A controlling microcomputer 12 controls voltage and frequency for making the electroluminescent device 18 emit light. The output voltage of an inverter 16 is fed back to the controlling microcomputer 12. Thereby, a trouble of the electroluminescent device 18 is detected. In addition, the controlling microcomputer 12 controls an output voltage for making the electroluminescent device 18 emit light according to atmosphere temperature information outputted from a temperature sensor 20 and atmosphere humidity information outputted from a humidity sensor 22. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electroluminescence driving apparatus and driving method, and more particularly to a technique for supplying a driving voltage to an electroluminescence element.

  Electroluminescence is a phenomenon that emits light when a voltage is applied to zinc sulfide (ZnS) or the like, and an electroluminescence element using this phenomenon is widely used in display devices and electronic devices.

  For example, electroluminescence is used in automobiles and the like. In this case, the electroluminescence element may be exposed to sunlight, and the ambient temperature may be extremely high. When a voltage is applied to electroluminescence and light is emitted, if the ambient temperature of the electroluminescence becomes high, there is a problem that the life of the electroluminescence is extremely shortened due to the application of the voltage and the high temperature. Arise.

  In order to solve this, a technique for controlling the voltage applied to electroluminescence according to the ambient temperature is known (see Patent Document 1).

JP 07-263142 A

  However, since the lifetime of electroluminescence is affected by the voltage application time and humidity in addition to the ambient temperature, control based solely on the ambient temperature has not always been sufficient.

  Therefore, the present invention aims to extend the lifetime of electroluminescence by control based on various factors that determine the lifetime.

  In order to achieve the above object, an electroluminescence driving apparatus according to a preferred aspect of the present invention includes a humidity sensor disposed in the vicinity of the electroluminescence, and a control unit that controls the driving voltage of the electroluminescence. Then, based on the humidity detected by the humidity sensor, the drive voltage is lowered as the humidity increases.

  Preferably, the apparatus further includes a temperature sensor disposed in the vicinity of the electroluminescence, and at least one of the humidity and the temperature is increased based on the humidity detected by the humidity sensor and the temperature detected by the temperature sensor. The drive voltage is lowered.

  More preferably, the drive voltage is increased as the drive time elapses to compensate for a decrease in luminance of the electroluminescence.

  In order to achieve the above object, a driving method of electroluminescence which is a preferred embodiment of the present invention is based on humidity near electroluminescence, temperature near the electroluminescence, and driving time of the electroluminescence. And controlling the drive voltage.

  Control based on various factors that determine lifetime can extend the lifetime of electroluminescence.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

  FIG. 1 shows a preferred embodiment of the present invention, and FIG. 1 is an overall configuration diagram of an electroluminescence driving device. The drive device is mounted on, for example, an automobile, and an electroluminescence (EL) 18 is attached to the back side of a design part as night illumination in the vehicle. Of course, the electroluminescence (EL) 18 may be used for a display device or an electronic device in a vehicle.

  If the power supply circuit 10 is for automobiles, it converts the voltage of the vehicle battery (for example, 12V) to the power supply terminal voltage (for example, about 2.5V to 5V) of the control microcomputer 12.

  The temperature sensor 20 is disposed in the vicinity of the electroluminescence 18 and monitors the ambient temperature. For example, the temperature sensor 20 changes the resistance value according to the detected temperature, and transmits the voltage according to the resistance value to the control microcomputer 12 as temperature information.

  The humidity sensor 22 is disposed in the vicinity of the electroluminescence 18 and monitors the atmospheric humidity. For example, the humidity sensor 22 changes the resistance value according to the detected humidity, and transmits the voltage according to the resistance value to the control microcomputer 12 as humidity information.

  The voltage control circuit 14 outputs a voltage based on the control signal output from the control microcomputer 12 to the inverter 16 at the next stage.

  The inverter 16 is a circuit that generates an output voltage proportional to the input voltage. That is, the inverter 16 converts, for example, an input voltage having an amplitude of about 5V into a drive voltage for the electroluminescence 18 having an amplitude of about 100V. The electroluminescence 18 emits light by this driving voltage.

  The control microcomputer 12 controls the voltage and frequency for causing the electroluminescence 18 to emit light. The control microcomputer 12 is fed back with the output voltage of the inverter 16 in order to confirm the drive voltage actually output to the electroluminescence 18. Thereby, the control microcomputer 12 can detect a defect of the electroluminescence 18. For example, when the feedback voltage is extremely lowered, it is considered that a problem such as a short circuit has occurred on the electroluminescence 18 side, and the supply of the drive voltage is stopped, or when the feedback voltage is extremely increased, a problem such as disconnection occurs. The supply of drive voltage is stopped.

  The control microcomputer 12 further controls the output voltage for causing the electroluminescence 18 to emit light based on the atmospheric temperature information output from the temperature sensor 20 and the atmospheric humidity information output from the humidity sensor 22.

  The output voltage control by the control microcomputer (reference numeral 12 in FIG. 1) will be described below with reference to FIGS. In the following description, the parts already shown in FIG.

  FIG. 2 is a diagram for explaining the relationship between the ambient temperature and humidity and the output voltage supplied to the electroluminescence 18.

  In the present embodiment, the control microcomputer 12 controls the output voltage of the inverter 16 according to the ambient temperature and humidity. Specifically, for example, when the humidity is less than 80%, the output voltage is made constant at a predetermined value, and when the humidity is 80% or more, the output voltage is controlled to decrease as the humidity increases.

  By this control, it is possible to suppress the life reduction of the electroluminescence 18 in the high humidity atmosphere.

  Furthermore, it is desirable to perform control in consideration of the ambient temperature. For example, when the humidity is as high as 80% or higher or the temperature is as high as 60 degrees or higher, the output voltage is controlled to decrease as indicated by the solid line 30. Depending on the rise in temperature and humidity, for example, when the temperature and humidity both exceed a predetermined value, the output voltage is further lowered than the solid line 30 as indicated by the dotted line 32. Depending on the rise in temperature and humidity, the output voltage may be lowered as indicated by the alternate long and short dash line 34.

  By control based on both humidity and temperature, it is possible to suppress a decrease in the lifetime of the electroluminescence 18 in a high-temperature and high-humidity atmosphere.

  Furthermore, the luminance change of the electroluminescence 18 can be suppressed by changing the output voltage according to the drive (elapsed) time.

  FIG. 3 is a diagram for explaining the relationship between the driving time and the output voltage supplied to the electroluminescence 18.

  When driving is continued with the output voltage kept constant, the luminance of the electroluminescence 18 changes as indicated by a dotted line 40. That is, the luminance decreases as the driving time elapses. In order to compensate for this decrease in luminance, the output voltage is changed as indicated by a solid line 42. That is, the output voltage is increased with the lapse of the driving time to compensate for the decrease in luminance. You may combine the increase control of the output voltage accompanying progress of this drive time, and the control based on the above-mentioned humidity and temperature.

  That is, the output voltage is changed as indicated by the solid line 42 in the range of normal temperature and low humidity, and the output voltage is changed in the range of high temperature and high humidity taking into account the decrease in output voltage due to high temperature and high humidity. For example, in the case of high temperature and high humidity, the output voltage is reduced as shown in FIG. 2, so the output voltage reduction rate in the case of high temperature and high humidity is multiplied by the solid line 42 shown in FIG.

  Specifically, when at least one of temperature and humidity exceeds a predetermined value after a predetermined time elapses and then rapidly returns to room temperature and low humidity, the output voltage is changed as indicated by a correction curve 44. In the portion of the correction curve 44, the reduction rate of the output voltage in the case of high temperature and high humidity is taken into consideration.

  If the life of the electroluminescence 18 is more important than suppressing the decrease in luminance with the lapse of the driving time, the output voltage is not increased with the lapse of the driving time, and the process proceeds in the range of high temperature and high humidity. It is desirable to perform control so as to decrease to a predetermined output voltage regardless of time.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

  For example, since a vehicle is provided with a temperature sensor and a humidity sensor for controlling an air conditioner, these air conditioner control sensors may be used in combination as a temperature sensor and a humidity sensor for electroluminescence control. As a result, cost reduction is expected.

  The vehicle may be provided with a vehicle LAN that connects a plurality of devices to be mounted. In this case, each unit shown in FIG. 1 may be connected to the vehicle LAN and exchange signals through the vehicle LAN. Incidentally, since a high voltage is output from the inverter to the electroluminescence, a dedicated high voltage cable may be used between the inverter and the electroluminescence instead of the vehicle LAN.

1 is an overall configuration diagram of an electroluminescence driving device according to the present invention. It is a figure for demonstrating the relationship between atmospheric temperature, humidity, and the output voltage supplied to electroluminescence. It is a figure for demonstrating the relationship between drive time and the output voltage supplied to electroluminescence.

Explanation of symbols

12 control microcomputer, 16 inverter, 18 electroluminescence (EL), 20 temperature sensor, 22 humidity sensor.

Claims (4)

A humidity sensor located in the vicinity of the electroluminescence,
A control unit for controlling the driving voltage of the electroluminescence;
Have
Based on the humidity detected by the humidity sensor, the drive voltage is reduced as the humidity increases.
An electroluminescence driving device characterized by that. The electroluminescent driving device according to claim 1,
Further comprising a temperature sensor disposed in the vicinity of the electroluminescence,
Based on the humidity detected by the humidity sensor and the temperature detected by the temperature sensor, the drive voltage is decreased as at least one of humidity and temperature increases.
An electroluminescence driving device characterized by that. The electroluminescence driving device according to claim 2,
Increasing the drive voltage as drive time elapses to compensate for a decrease in luminance of the electroluminescence,
An electroluminescence driving device characterized by that. Humidity near electroluminescence,
The temperature in the vicinity of the electroluminescence,
Driving time of the electroluminescence,
Control the driving voltage based on
An electroluminescence driving method characterized by the above.

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