the feedback voltage becomes lower than a reference voltage the frequency of the clock signal input into a dc dc converter increases if the feedback voltage is lower than a predetermined voltage this indicates that the level of the first driving voltage is lower than a predetermined value and thus current consumption of the lcd panel is large it is possible to decrease power consumption and increase boosting efficiency by changing the frequency of the clock signal used for boosting of a dc dc converter according to the current consumption of the lcd panel application_number US 54029206 A description the present invention will now be described more fully with reference to the accompanying drawings in which preferred embodiments of the invention are shown like reference numerals in different drawings refer to like elements first the relationship between boosting efficiency and the frequency of a clock signal used for boosting voltages is described the frequency of the clock signal is referred to herein as u201c boosting frequency u201d fig2 is a graph illustrating the relationship between boosting efficiency and current consumption iload of an lcd panel according to the frequency fck of the clock signal referring to fig2 if the current consumption iload of the lcd panel increases boosting efficiency is decreased regardless of the value of the frequency fck of the clock signal however if the frequency fck of the clock signal is 390khz the effect on boosting efficiency due to an increase.