Apparatus for driving lamp of liquid crystal display device
View Patent ↗An apparatus for driving a lamp of a liquid crystal display device includes a transformer to supply a voltage to a lamp and a voltage detector having a first resistance connected between a secondary winding wire of the transformer and a ground voltage source, a rectifier connected to the secondary winding wire of the transformer, and a second resistance connected between the rectifier and the ground voltage source to detect a voltage induced onto the secondary winding wire of the transformer.
1. An apparatus for driving a lamp of a liquid crystal display device comprising:
a transformer to supply a voltage to a lamp;
a voltage detector including a first resistance connected between a secondary winding wire of the transformer and a ground voltage source, a rectifier connected to the secondary winding wire of the transformer, and a second resistance connected between the rectifier and the ground voltage source to detect a voltage induced onto the secondary winding wire of the transformer; and
an over current protecting part having one end connected to the secondary winding wire of the transformer, and another end connected to a feedback line connected to a controller to prevent an excessive tube current from passing through the lamp,
wherein the first resistance has a resistance value in range of about 200Ω to 430Ω and the second resistance has a resistance value in a range of 15 kΩ to 35 kΩ.
2. The apparatus according to claim 1 , wherein the first resistance and the second resistance are connected in parallel with each other.
3. The apparatus according to claim 1 , wherein a combined resistance of the first and the second resistances has a value in a range of 200Ω to 430Ω.
4. The apparatus according to claim 1 , wherein the rectifier includes:
a first diode connected between the ground voltage source and a first node of both the secondary winding wire of the transformer and the first resistance; and
a second diode connected between the second resistance and a second node of both the secondary winding wire of the transformer and the first diode.
5. The apparatus according to claim 1 , further comprising:
a switch device to provide a supply voltage from a voltage source to the transformer; and
the controller to control the switch device in response to the voltage from the voltage detector.
6. The apparatus according to claim 5 , further comprising a voltage dropping part to drop the voltage detected by the second resistance.
7. The apparatus according to claim 5 , further comprising a third diode to reduce the voltage detected by the rectifier.
8. The apparatus according to claim 1 , wherein the over current protecting part includes:
a fourth diode connected between an input terminal of the rectifier and an input terminal of the controller to rectify a signal;
a third resistance connected between one side of the fourth diode and the ground voltage source to detect a voltage of the signal rectified by the fourth diode;
a fourth resistance connected to the third resistance in parallel to divide the signal rectified by the fourth diode;
a fifth diode to rectify a signal supplied to the fourth resistance;
a fifth resistance connected between the fifth diode and the ground voltage source to a voltage of the signal rectified by the fifth diode; and
a capacitor connected to the fifth resistance in parallel to maintain the voltage detected by the fifth resistance.
9. The apparatus according to claim 8 , wherein the over current protecting part includes:
a driving voltage source;
a sixth resistance to drop a voltage of the driving voltage source;
a first switch connected between the sixth resistance and the ground voltage source to be turned on or turned off by the voltage detected by the fifth resistance; and
a second switch connected between the controller and the ground voltage source to be turned off when the first switch is turned on.
10. An apparatus for driving a lamp of a liquid crystal display device comprising:
a transformer to supply a voltage to a lamp;
a switch device switched by a switching control signal to provide a supply voltage from a voltage source to the transformer;
a voltage detector to detect the voltage supplied from the transformer and generate a feedback voltage;
a controller to switch the switch device in response to the feedback voltage from the voltage detector,
wherein the voltage detector includes:
a first resistance connected between a secondary winding wire of the transformer and the ground voltage source to have a first resistance value to detect the voltage from a first current portion out of a total current induced onto the secondary winding wire of the transformer;
a rectifier to rectify a second current portion out of a total current induced onto the secondary winding wire of the transformer; and
a second resistance connected between the rectifier and the ground voltage source to have a second resistance value to detect the voltage with the second current portion rectified by the rectifier; and
an over current protecting part having one end connected to the secondary winding wire of the transformer, and another end connected to a feedback line connected to the controller to prevent an excessive tube current from passing through the lamp,
wherein the first resistance has a resistance value in range of about 200Ω to 430Ω and the second resistance has a resistance value in a range of 15 kΩ to 35 kΩ.
11. The apparatus according to claim 10 , further comprising a diode connected between the second resistance and the controller to drop the voltage detected by the second resistance.
12. The apparatus according to claim 10 , further comprising a diode connected between the rectifier and the second resistance to drop a voltage detected by the rectifier.