a microphone configured to receive utterance data in a suspend mode state;

a digital signal processor comprising a first buffer, and configured to receive first utterance data from the—microphone, recognize a trigger word in the suspend mode state, temporarily store the first utterance data in the first buffer, and transmit a buffering command to a microcontroller when the trigger word is recognized;

wherein the microcontroller comprises a second buffer, and is configured to output a first command-to a main controller, transmit a reset command to the digital signal processor, receive second utterance data subsequent to the first utterance data from the microphone, and temporarily store the second utterance data in the second buffer in response to the buffering command; and

the main controller is configured to boot in response to the first command, request and receive the first utterance data to the digital signal processor, verify the trigger word on a basis of the first utterance data, when verification of the trigger word is successful, request and receive the second utterance data to the microcontroller, request and receive a third utterance data to the microphone, and join the third utterance data and the second utterance data stored in the second buffer, to perform voice recognition;

wherein the microcontroller starts storing the second utterance data in response to the buffering command, and stops storing the second utterance data in response to a request for the second utterance data from the main controller,

wherein the image display device switches from the suspend mode state to a standby mode state according to the first command.