Synchronous rectification controller and isolated synchronous rectification type dc/dc converter

A synchronous rectification controller that controls driving a synchronous rectification transistor arranged on a secondary side, comprising:

• a gate terminal capable of being electrically connected to a gate of the synchronous rectification transistor;
• a drain terminal capable of being electrically connected to a drain of the synchronous rectification transistor via a first resistor;
• a first comparator configured to compare a drain terminal voltage generated at the drain terminal with a negative first threshold voltage;
• a second comparator configured to compare the drain terminal voltage with a negative second threshold voltage higher than the negative first threshold voltage;
• and
• a driver configured to perform an on/off control of the synchronous rectification transistor based on a result of the comparison by the first comparator and a result of the comparison by the second comparator,
• wherein when the synchronous rectification transistor is turned on, a voltage is added to the drain terminal voltage by a current flowing through the first resistor according to a second resistor.