Voltage detecting device and battery pack monitoring system

A voltage detecting device for detecting a differential voltage between two input nodes having a common mode voltage, which is not zero, the voltage detecting device comprising:

• a differential voltage detecting circuit for detecting the differential voltage by sampling each voltage of the two input nodes and for outputting a detection voltage indicating a detection result;
• a leak canceling circuit for generating a compensating current, which flows in an opposite direction to a leak current leaking from two input node sides due to an operation of the differential voltage detecting circuit;
• an operation control part for controlling the leak cancelling circuit to perform or stop a leak cancelling operation;
• and
• a failure diagnosing part for performing a failure diagnosis about the leak canceling circuit based on a difference between a first detection value and a second detection value, the first detection value and the second detection value indicating values of the detection voltages detected in periods, during which the leak canceling circuit is controlled to perform and stop the leak canceling operation, respectively.