A driving circuit uses a plurality of transformers to provide currents for driving a plurality of LEDs associated with a plurality of current paths. Each transformer has two induction coils with a coil turn ratio between to the number of turns in each induction coil. One induction coil is used to provide an output current to a different current path and the other induction coil is connected to the corresponding induction coil of other transformers for forming a current loop. The output current of each transformer has a relationship with the output current of the other transformers depending on the coil turn ratios of the connected transformers. LEDs in red, blue and green colors can be connected to different current paths so that the brightness of the LEDs in each color can be determined by the current in a current path.