Patent ID: 8004509

Claim:
A liquid crystal display device including a timing controller provided with a signal presence determiner for detecting an application of an input signal from an interface, wherein said signal presence determiner comprises: an oscillator for generating a reference clock having the same frequency as a horizontal synchronizing signal and a pre-synchronizing signal having the same frequency as a vertical synchronizing signal; a period detector for comparing a data enable signal from the exterior thereof with the reference clock to output a period of the input signal with the aid of a detection reference signal and the pre-synchronizing signal; and a period comparator for comparing a period range between a desired maximum value and a desired minimum value of the input signal, outputting a signal of a first state to a signal presence comparing means only if the period of the input signal is within the period range, and outputting the signal of the first state to a signal absence comparing means only if the period of the input signal is beyond the period range; the signal presence comparing means for determining a presence of the input signal in response to a pulse number of the input signal detected within a period range between the maximum value and the minimum value if the number of pulses of the signal of the first state is larger than a predetermined plural number during an application input interval of the detection reference signal, being different from the signal of the first state, wherein each of the pulses is to be of the first state and continuously has same values; and the signal absence comparing means for determining an absence of the input signal if the number of pulses of the signal of the first state is smaller than a predetermined plural number during an input interval of the detection reference signal, being different from the signal of the first state, wherein each of the pulses is to be of the first state and continuously has same values.