Patent ID: 7525258

Claim:
An apparatus for balancing lamp currents of four lamp-cells, wherein each lamp-cell comprises multiple balanced lamps, and wherein each lamp-cell has two electrical ports, the apparatus comprising: a first transformer T 1 , having a primary and a secondary winding, wherein a capacitor is connected between a first and a second end of the secondary winding; a second transformer T 2 , having a primary and a secondary winding, wherein a capacitor is connected between a first and a second end of the secondary winding; and a balancing circuit wherein: one electrical port of a first lamp-cell is connected to the first end of the secondary winding of T 1 and the other electrical port of the first lamp-cell is connected to the second end of the secondary winding of T 2 ; one electrical port of a second lamp-cell is connected to the first end of the secondary winding of T 1 and the other electrical port of the second lamp-cell is connected to the second end of the secondary winding of T 1 ; one electrical port of a third lamp-cell is connected to the first end of the secondary winding of T 2 and the other electrical port of the third lamp-cell is connected to the second end of the secondary winding of T 1 ; and one electrical port of a fourth lamp-cell is connected to the first end of the secondary winding of T 2 and the other electrical port of the fourth lamp-cell is connected to the second end of the secondary winding of T 2 .