A sleep/awake circuit includes an infrared receiving/sending module, a micro-control circuit, and a bus control circuit. The micro-control circuit sends a command signal to the infrared receiving/sending module at predetermined intervals. The infrared receiving/sending module detects the presence or absence of a user and then sends a signal back to the micro-control circuit indicating a result. According to the result, the micro-control circuit exchanges data and clock signals with the bus control circuit. The bus control circuit then sends control signals to the computer to control sleep/awake states of the computer.