A power conversion apparatus (and an air conditioner including the same) may include a rectifier to rectify a voltage of an input alternating current (AC) power source and a voltage drop device to output a dropped voltage using the voltage from the rectifier. The voltage drop device may include a transformer and a communication voltage output device provided at a secondary side of the transformer to output a direct current (DC) voltage for operation of a communication device. Accordingly, a voltage may be stably supplied to the communication device while reducing standby power.