Backlight unit for liquid crystal display
View Patent ↗The invention provides a cost effective way of determining the status of a light emitting device, such as a light emitting device in a non-emitting display device. The apparatus includes a light emitting device, a voltage supply coupled to the light emitting device for making a current flow through the light emitting device, and an electrically conductive device spaced apart from the light emitting device for inducing a voltage proportional to the voltage across the light emitting device. A status determining device determines the status of the light emitting device based on the voltage from the electrically conductive device.
1. An apparatus for checking a status of a light emitting device, the apparatus comprising:
a light emitting device including at least two electrodes and a light emitting body between the electrodes;
a voltage supply coupled to at least one electrode of the light emitting device so as to generate a voltage across the light emitting body;
an electrically conductive device positioned proximate to the light emitting body, the light emitting body inducing a voltage in the electrically conductive device, the induced voltage being proportional to the voltage across the light emitting body; and
a status determining device for determining the status of the light emitting device based on the induced voltage.
2. The apparatus of claim 1 , wherein the status determining device comprises a shut off device for stopping the current from flowing through the light emitting device if the voltage fulfills a predefined condition.
3. The apparatus of claim 2 , wherein the predefined condition comprises the induced voltage being in a predefined range.
4. The apparatus of claim 2 , wherein the predefined condition indicates that the light emitting device is operating abnormally.
5. The apparatus of claim 1 further comprising a rectifier circuit having a first node and a second node, wherein the first node is connected to the electrically conductive device and the second node is connected to a signal detector.
6. The apparatus of claim 1 wherein the induced voltage having a level below a threshold value indicates that the light emitting device is operating abnormally.
7. The apparatus of claim 1 , wherein the light emitting device is one of an external electrode fluorescent lamp, a cold cathode fluorescent lamp, and a light emitting diode.
8. The apparatus of claim 1 , wherein the light emitting device switches on and off periodically at a predetermined on/off duty ratio.
9. A method of checking a status of a light emitting device, the light emitting device including at least two electrodes and a light emitting body between the electrodes, the method comprising:
inducing a voltage proportional to the voltage across the light emitting body in an electrically conductive device positioned proximate to the light emitting body; and
determining which one of a plurality of predefined voltage ranges encompasses the induced voltage,
wherein each of the predefined ranges corresponds to a particular state of the light emitting device.
10. A method of checking a status of a light emitting array, wherein the light emitting array includes a plurality of light emitting devices, each including at least two electrodes and a light emitting body extending between the electrodes, the method comprising:
inducing a voltage proportional to the voltage across each of the light emitting bodies in an electrically conductive device positioned proximate to the light emitting bodies;
determining whether any of the light emitting devices is in an abnormal operational state based on the output voltage.
11. The method of claim 10 further comprising: receiving an error prevention signal that is generated if any of the light emitting devices is in a normal inactive state; and using the error prevention signal for the determining of whether any of the light emitting devices is in an abnormal operational state.
12. A liquid crystal display device comprising:
a liquid crystal display panel; electrodes for generating an electric field in the liquid crystal display panel; and
a backlight assembly including:
a first light emitting device including at least two electrodes and a light emitting body between the electrodes,
a voltage supply coupled to at least one electrode of the light emitting body so as to generate a voltage across the light emitting body;
a first electrically conductive device positioned proximate to from the light emitting body, the light emitting body inducing a voltage in the first electrically conductive device, the induced voltage being proportional to the voltage across the light emitting body; and
a status determining device for determining the status of the light emitting device based on the induced voltage.
13. The liquid crystal display device of claim 12 , wherein the status determining device comprises a shut off device for stopping the current from flowing through the light emitting device if the induced voltage fulfills a predefined condition.