A display apparatus, a power supply apparatus and a power supply method thereof are provided. The display apparatus includes: a signal processor which processes an image signal; a display unit which displays thereon an image corresponding to the processed image signal; and a power supply unit which receives an input of AC power and supplies operating power to the display unit. The power supply unit includes a discharging circuit unit which discharges a remaining voltage of the power supply unit if the input of the AC power is suspended, and does not discharge the voltage if the AC power is input. Accordingly, a remaining voltage from a power supply unit is effectively removed if an input of AC power is suspended, and power consumption does not occur if the AC power is input.