1. A voice wakeup detecting device for an electronic product, the voice wakeup detecting device comprising: a digital microphone, for controlling a first interrupt signal by judging whether a digital voice signal contains a subword, wherein if the digital microphone confirms that the digital voice signal contains the subword, the digital microphone asserts the first interrupt signal; a speech recognition processor connected to the digital microphone, wherein the speech recognition receives the digital voice signal when the first interrupt signal is asserted; and a main processor connected to the speech recognition processor; wherein when the first interrupt signal is not asserted, the digital microphone is powered, the speech recognition processor is not powered and the main processor is in a sleep state; wherein when the first interrupt signal is asserted, the digital microphone and the speech recognition processor are powered and the main processor is in the sleep state; and wherein the speech recognition processor selectively asserts a second interrupt signal by judging whether the digital voice signal contains a keyword, wherein if the speech recognition processor confirms that the digital voice signal contains the keyword, the main processor is waked up from the sleep state to a normal working state in response to the second interrupt signal.