NOISE REDUCTION DEVICE, POWER CONVERSION DEVICE, VEHICLE, AND NOISE REDUCTION METHOD

A noise reduction device according to one embodiment includes a noise reduction circuit and a failure diagnosis circuit. The noise reduction circuit generates an offset signal with reverse polarity of a noise component generated in a load. The failure diagnosis circuit detects a level of the offset signal. The failure diagnosis circuit determines whether or not a detected level of the offset signal deviates from an appropriate range. The failure diagnosis circuit diagnoses, on the basis of a determination result, whether or not a failure has occurred in the noise reduction circuit.