LIQUID CRYSTAL DISPLAY BACKLIGHT INVERTER

Abstract

An LCD backlight inverter includes a soft starter for generating a soft-start reference voltage gradually increasing as the driving power begins to be supplied. The LCD backlight inverter also includes a first error detector for receiving a first feedback voltage indicating the magnitude of driving current of the lamp and for comparing a smaller value out of a predetermined first reference voltage and the soft-start reference voltage with the first feedback voltage to generate a first error signal corresponding to the difference between the smaller value and the soft-start reference voltage. The LCD backlight inverter further includes a pulse width modulation comparator for comparing the first error signal and a triangle wave oscillation signal to output the pulse width modulation control signal with a predetermined duty ratio. The LCD backlight inverter prevents application of over-current and over-voltage to the LCD backlight to prolong the lifetime of the backlight.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features and other advantages of the present invention will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a circuit diagram illustrating a conventional Liquid Crystal Display (LCD) backlight inverter for generating a Pulse Width Modulation (PWM) control signal;

FIG. 2 is a circuit diagram illustrating an LCD backlight inverter for generating a PWM control signal according to an embodiment of the present invention;

FIG. 3 is a circuit diagram illustrating a soft starter of the LCD backlight inverter according to an embodiment of the present invention;

FIG. 4 is a circuit diagram illustrating an LCD backlight inverter for generating a PWM control signal according to another embodiment of the present invention; and

FIG. 5 is a waveform diagram for explaining the operation of the LCD backlight inverter according to the present invention.

Claims

1. A liquid crystal display backlight inverter, which generates a pulse width modulation control signal to regulate the magnitude of driving power of a liquid crystal display backlight lamp, comprising: a soft starter for generating a soft-start reference voltage gradually increasing as the driving power begins to be supplied;a first error detector for receiving a first feedback voltage indicating the magnitude of driving current of the lamp and for comparing a smaller value out of a predetermined first reference voltage and the soft-start reference voltage with the first feedback voltage to generate a first error signal corresponding to the difference between the smaller value and the soft-start reference voltage; anda pulse width modulation comparator for comparing the first error signal and a triangle wave oscillation signal to output the pulse width modulation control signal with a predetermined duty ratio.

2. The liquid crystal display backlight inverter according to claim 1, wherein the soft starter comprises: a switch connected to one end of a power source, the switch being turned on as the driving power is supplied to the lamp; anda capacitor connected between the other end of the switch and a ground,wherein the soft-starter provides the voltage generated at a connection point of the switch and the capacitor as the soft-start reference voltage.

3. The liquid crystal display backlight inverter according to claim 1, further comprising: a second error detector for receiving a second feedback voltage indicating the magnitude of driving voltage of the lamp and for comparing a smaller value out of a predetermined second reference voltage and the soft-start reference voltage with the second feedback voltage to generate a second error signal corresponding to the difference between the smaller value and the soft-start reference voltage,wherein the pulse width modulation comparator compares a smaller value of the first error signal and the second error signal with the triangle wave oscillation signal to determine the duty ratio of the pulse width modulation control signal.