Inverter and liquid crystal display including inverter
View Patent ↗An inverter is provided, which includes: a voltage converter that converts a DC voltage from an external device into an AC voltage to drive at least a lamp and includes a primary coil and first and second secondary coils connected in series; a current sensor that senses at least a current flowing in the first or second secondary coil and generate at least a sensing signal based on the sensed at least a current; a feedback signal generator that generates a feedback signal based on the at least a sensing signal from the current sensor; and a controller that controls the voltage converter based on the feedback signal such that a tube current flowing in the at least a lamp keeps substantially constant.
1. An inverter comprising:
a voltage converter that converts a DC voltage from an external device into an AC voltage to drive at least a lamp and includes a primary coil and first and second secondary coils connected in series;
a current sensor that senses at least a current flowing in the first or second secondary coil and generates at least a sensing signal based on the sensed at least a current, wherein the current sensor comprises first and second resistors connected in series between the first secondary coil and the second secondary coil, and a third resistor connected between a predetermined constant voltage and a first node between the first resistor and the second resistor, and further wherein a voltage at the first node is different from the predetermined constant voltage;
a feedback signal generator that generates a feedback signal based on the at least a sensing signal from the current sensor; and
a controller that controls the voltage converter based on the feedback signal such that a tube current flowing in the at least a lamp keeps substantially constant.
2. The inverter of claim 1 , wherein the at least a lamp comprises a plurality of lamps connected in parallel.
3. The inverter of claim 1 , wherein the voltage converter applies voltages having the same magnitude and different polarities to respective ends of the at least a lamp.
4. The inverter of claim 1 , wherein the at least a lamp comprises an external electrode lamp.
5. The inverter of claim 1 , wherein the first to third resistors have the same resistance.
6. The inverter of claim 1 , wherein the at least a sensing signal includes a first voltage at a second node between the first secondary coil and the first resistor.
7. The inverter of claim 6 , wherein the feedback signal generator rectifies the first voltage to generate the feedback signal.
8. The inverter of claim 6 , wherein the at least a sensing signal further includes a second voltage at the first node between the first resistor and the second resistor.
9. The inverter of claim 8 , wherein the feedback signal generator comprises:
a rectifier that rectifies the first and the second voltages; and
an operation unit that generates the feedback signal expressed as a first-order function of the rectified first and second voltages from the rectifier.
10. The inverter of claim 9 , wherein the operation unit comprises:
a first amplifier that inverts the rectified first voltage; and
a second amplifier that doubles the rectified second voltage, adds the inverted first voltage from the first amplifier and the doubled rectified second voltage to generate a third voltage, and inverts the third voltage.
11. The inverter of claim 8 , wherein the at least a sensing signal further includes a third voltage at a third node between the second secondary coil and the second resistor.
12. The inverter of claim 11 , wherein the feedback signal generator comprises:
a rectifier that rectifies the first to third voltages;
a first operation unit that generates a first feedback signal expressed as a first-order function of the rectified first and second voltages; and
a second operation unit that generates a second feedback signal expressed as a first-order function of the rectified second and third voltages,
wherein the feedback signal includes a smaller one of the first and second feedback signals.
13. The inverter of claim 12 , wherein the first operation unit comprises:
a first amplifier that inverts the rectified first voltage; and
a second amplifier that doubles the rectified second voltage, adds the inverter first voltage from the first amplifier and the doubled rectified second voltage to generate a fourth voltage, and inverts the fourth voltage, and
the second operation unit comprises:
a third amplifier that inverts the rectified third voltage; and
a fourth amplifier that doubles the rectified second voltage, adds the inverted third voltage from the third amplifier and the doubled rectified second voltage to generate a fifth voltage, and inverts the fifth voltage.
14. The inverter of claim 6 , wherein the at least a sensing signal further includes a second voltage at a third node between the second secondary coil and the second resistor.
15. The inverter of claim 14 , wherein the feedback signal generator comprises:
a rectifier that rectifies the first and second voltages;
a first operation unit that generates a first feedback signal expressed as a first-order function of the rectified first and second voltages; and
a second operation unit that generates a second feedback signal expressed as another first-order function of the rectified first and second voltages,
wherein the feedback signal includes a smaller one of the first and second feedback signals.
16. The inverter of claim 15 , wherein the first operation unit comprises:
a fourth resistor;
a fifth resistor;
a first feedback resistor; and
a first amplifier that receives the first and second voltages through the fourth and fifth resistors, respectively, and has a negative feedback connection through the first feedback resistor, and
the second operation unit comprises:
a sixth resistor;
a seventh resistor;
a second feedback resistor; and
a second amplifier that receives the first and second voltages through the sixth and seventh resistors, respectively, and has a negative feedback connection through the second feedback resistor.
17. The inverter of claim 16 , wherein a resistance ratio of the first feedback resistor, the fourth resistor, and the fifth resistor is about 1:3:1.5, and a resistance ratio of the second feedback resistor, the sixth resistor, and the seventh resistor, is about 1:1.5:3.
18. The inverter of claim 1 , wherein the primary coil comprises a first portion coupled with the first secondary coil to form a first transformer and a second portion coupled with the second secondary coil to form a second transformer, and the first transformer and a second transformer is spaced apart from each other on a printed circuit board.
19. The inverter of claim 18 , wherein the first and second transformers are located near respective ends of the printed circuit board in a length direction.