A light sensing circuit includes a sensor unit, a voltage generator and a readout circuit. The sensor unit includes a first sensor that detects an external light to output a first current value, a third sensor that detects an internal light generated from the backlight unit to output a third current value, and a second sensor that detects a peripheral light isolated from the external light and the internal light to output a second current value. The sensor unit outputs a first differential value between the third current value and the second current value and a second differential value between the first current value and the second current value. The voltage generator generates a reference voltage based on the first differential value and a sensing voltage based on the second differential value. The readout circuit outputs brightness information of the external light using the reference voltage and the sensing voltage.