Multi-stage power adapter techniques are described in which a power adapter for a device is configured to selectively switch between a relatively low power supply and a relatively high power supply. The low power supply may be employed upon initial connection of the adapter to a host device to ensure that the adapter is safe when disconnected and does not supply full power before the device is ready to receive the high power supply. The low power supply may supply enough power for the host device to detect the connection of the adapter and establish initial communication with the adapter. A switch to the high power supply by the adapter may then occur in response to a notification from the host device that indicates the host device is ready for the high power supply. The switch to high power supply enables normal operation of the host device.