Patent ID: 8253682

Claim:
A backlight driving circuit, comprising: a brightness controller configured to generate a first control signal according to a brightness adjusting signal which is defined by a predetermined parameter, the brightness adjusting signal being variable according to an OSD adjustment operation from a user, a duty ratio of the first control signal being variable according to a variance of the brightness adjusting signal; a timing controller configured to generate a second control signal according to a brightness component of image data of a video image to be displayed, a duty ratio of the second control signal being variable according to a variance of the brightness component; a logic AND gate circuit configured to directly receive the first control signal from the brightness controller and the second control signal from the timing controller, perform the logical AND operation on the first control signal and the second control signal, and generate a composite signal via the logical AND operation; a pulse width modulation (PWM) circuit configured to receive the composite signal from the logic AND gate circuit, and generate a pulse signal according to the composite signal; and an inverter configured to receive the pulse signal from the PWM circuit, generate a driving voltage according to the pulse signal, and adjust the brightness of a lamp by use of the driving voltage; wherein a frequency of the first control signal is less than a frequency of the second control signal.