A charge device is provided. The charge device includes a charge interface, a voltage detector and a control circuit. The charge interface receives a first power and provides a charge power to charge a rechargeable device accordingly. The voltage detector detects a charge voltage of the rechargeable device. The control circuit is respectively coupled to the charge interface and the voltage detector. When the charge voltage is smaller than a predetermined voltage, the control circuit makes the charge voltage and a charge current of the charge power to present a proportional relation. An electronic device and a charge method are also provided.