Patent ID: 8648572

Claim:
A protection circuit, comprising: a connecting terminal which is connected to an external circuit and which inputs and outputs a charging and discharging current of a secondary battery to and from the external circuit; a voltage detection unit for detecting an output voltage of the secondary battery; a current detection unit for detecting the discharging current of the secondary battery; a power consumption calculation unit for calculating power consumption of the external circuit by multiplying a value of the output voltage detected by the voltage detection unit by a value of the discharging current detected by the current detection unit; a first communication unit for receiving a power threshold, which is set to a value that is not less than a maximum value of the power consumption of the external circuit, and is sent from a control unit of the external circuit via a second communication unit of the external circuit; and an external protection unit for executing external protection processing of protecting the external circuit when the power consumption calculated by the power consumption calculation unit exceeds the power threshold received by the first communication unit.