According to one embodiment, a detection circuit includes a first filter circuit configured to output a first voltage, a ramp circuit configured to output a ramp voltage, a comparator configured to output a first result of comparison between the first voltage and the ramp voltage and a second result of comparison between a second voltage and the ramp voltage, and a controller, wherein the controller determines a first period of time between a time when the ramp voltage output is started and a time when a magnitude correlation between the first voltage and the ramp voltage is inverted, and determines a second period of time between a time when the ramp voltage output is started and a time when a magnitude correlation between the second voltage and the ramp voltage is inverted.