A display driving circuit and a display device including the same are provided. The display driving circuit includes a source driver which applies source data to a display panel, a power supply unit which receives an external voltage from a power module to generate an internal voltage and a logic unit which is supplied with the internal voltage to control the source driver, wherein the logic unit includes a voltage variable determination logic which determines whether a supply voltage including the internal voltage and the external voltage is changed, thereby generating a voltage variable signal, and a voltage control logic which receives the voltage variable signal to change the supply voltage.