condition as a result leds forming the back light 600 are driven by the pwm signals and the driving voltages provided from the back light driving circuit 500 so that the back light 600 emits light having a predetermined chromaticity and a predetermined luminance fig4 is a schematic block diagram of the back light 600 and the back light driving circuit 500 according to one embodiment of the invention the back light driving circuit 500 drives the back light 600 based on driving data provided for the leds by the lcd driving circuit 400 in this regard the driving voltage generator 510 receives the driving conditions for the forward driving voltage of the r g and b leds from among the driving conditions provided from the lcd driving circuit 400 as its input signal and the pwm signal generator 520 receives the driving conditions for the pwm signals of the r g and b leds as its input signal accordingly the driving voltage generator 510 receives the driving conditions for the forward driving voltages provided from the back light driving circuit 400 to sequentially generate the driving voltages namely rvf gvf and bvf of the r g and b leds rled gled and bled in addition the pwm signal generator 520 receives the driving conditions for the pwm signals.