Signal transmission device and gate drive device

A signal transmission device comprising:

• a primary circuit;
• an AC coupler configured to transmit a transmission signal received from the primary circuit;
• a secondary circuit configurated to receive the transmission signal transmitted from the AC coupler;
• and
• a detector configured to output a detection signal related to a noise level at a time of transmission of the transmission signal according to fluctuations of a terminal voltage based on a current flowing in at least either a first reference potential terminal of the primary circuit isolated by the AC coupler or a second reference potential terminal of the secondary circuit, wherein
• the detector comprises
• one or more first identifiers each configured to compare the terminal voltage with a positive predetermined voltage,
• one or more second identifiers each configured to compare the terminal voltage with a negative predetermined voltage,
• a first encoder configured to perform encoding of information related to a slew rate of the terminal voltage on a basis of a comparison result of the first identifiers, and
• a second encoder configured to perform encoding of information related to a slew rate of the terminal voltage on a basis of a comparison result of the second identifiers.