An isolated synchronous rectifying DC/DC converter, comprising:
- a synchronous rectification transistor disposed on a secondary side of the DC/DC converter;
- and
- a synchronous rectification controller configured to control driving of the synchronous rectification transistor,
- wherein the synchronous rectification controller includes:
- a drain terminal connected to a drain of the synchronous rectification transistor;
- a source terminal connected to a source of the synchronous rectification transistor;
- a comparator configured to compare a drain voltage of the drain terminal with a predetermined threshold voltage which is set based on a potential of the source terminal;
- a first flip-flop to which an OFF signal output from the comparator is input;
- a driver configured to output a gate signal to the synchronous rectification transistor based on an output signal of the first flip-flop;
- and
- a first abnormality detection circuit including an abnormality detection comparator configured to compare a voltage of the source terminal with a detection threshold voltage, and configured to output a first abnormality detection signal based on an output of the abnormality detection comparator,
- wherein the DC/DC converter is configured as an LLC converter having a first synchronous rectification transistor and a second synchronous rectification transistor,
- wherein the synchronous rectification controller further includes:
- a first drain terminal connected to a drain of the first synchronous rectification transistor;
- a second drain terminal connected to a drain of the second synchronous rectification transistor;
- a first source terminal connected to a source of the first synchronous rectification transistor;
- a second source terminal connected to a source of the second synchronous rectification transistor;
- a first gate terminal connected to a gate of the first synchronous rectification transistor;
- a second gate terminal connected to a gate of the second synchronous rectification transistor;
- a first driver configured to output a gate signal from the first gate terminal;
- a second driver configured to output a gate signal from the second gate terminal;
- a frequency divider to which the output signal of the first flip-flop is input;
- and
- a selector configured to switch a path of the comparator between the first drain terminal and the second drain terminal based on an output of the frequency divider, and to switch a path of the first flip-flop between the first driver and the second driver,
- wherein the predetermined threshold voltage is set based on potentials of the first source terminal and the second source terminal, and
- wherein the abnormality detection comparator is configured to compare a higher one of a voltage of the first source terminal and a voltage of the second source terminal, with the detection threshold voltage.