US Patent 8996892 Power smart peripheral devices with external power supplies

A peripheral device includes a host interface, a power interface, a switch, a control module, and a regulator. The host interface transfers data between the peripheral device and a host. The power interface receives power from a power source. The power source is separate from the peripheral device and the host. The control module monitors the host interface and generates a control signal to transition the switch from a first state to a second state when the host interface does not receive an expected signal from the host. The regulator powers the control module and a circuit of the peripheral device based on the power received from the power source. The control module is separate from the circuit. The switch activates the control module, the regulator and the circuit when in the first state and deactivates the control module, the regulator and the circuit when in the second state.