The invention provides an application device, a motor assembly, and a motor driving circuit thereof. The motor driving circuit comprises a controllable bidirectional AC switch serially connected between a motor and an external AC power supply, a switch control circuit used to control the connection or the disconnection of the controllable bidirectional AC switch in a preset way, and a delay circuit. The delay circuit is used to delay the connection of the controllable bidirectional AC switch for a predetermined while, and then a phase difference between current flowing across the motor and counter electromotive force is reduced. The motor driving circuit is used to improve the power efficiency of the motor.