A drive circuit configured to generate an output current for driving a light emitting element, comprising: a power source; two or more current control units each configured to control an amount of current to be supplied to the light emitting element in accordance with a respective pulse modulation signal, wherein the pulse modulation signal can have a high level and a low level; and a calculation unit configured to change a respective duty ratio of the respective pulse modulation signal, wherein each current control unit includes a first switching element configured to be switched on/off in accordance with the respective pulse modulation signal; a second switching element, configured to be switched on/off in accordance with the inverse of the respective pulse modulation signal input to the first switching element, or a diode; and an inductor, the first switching element and the inductor are serially connected in case the second switching element is switched off, and are located between the power source and the light emitting element, the second switching element or the diode is connected between ground and a contact point of the first switching element and the inductor, and the two or more current control units are connected in parallel; wherein the calculation unit is configured to individually and sequentially stop said two or more current control units by setting the respective pulse modulation signal to the low level for a plurality of cycles of the respective pulse modulation signal, the drive circuit further comprises a current detection unit configured to detect the output current, and the calculation unit is configured to identify a current control unit of said two or more current control units that is faulty in accordance with a fluctuation in the output current detected when one of said two or more current control units to be stopped is stopped. a power source; two or more current control units each configured to control an amount of current to be supplied to the light emitting element in accordance with a respective pulse modulation signal, wherein the pulse modulation signal can have a high level and a low level; and a calculation unit configured to change a respective duty ratio of the respective pulse modulation signal, wherein each current control unit includes a first switching element configured to be switched on/off in accordance with the respective pulse modulation signal; a second switching element, configured to be switched on/off in accordance with the inverse of the respective pulse modulation signal input to the first switching element, or a diode; and an inductor, a first switching element configured to be switched on/off in accordance with the respective pulse modulation signal; a second switching element, configured to be switched on/off in accordance with the inverse of the respective pulse modulation signal input to the first switching element, or a diode; and an inductor, the first switching element and the inductor are serially connected in case the second switching element is switched off, and are located between the power source and the light emitting element, the second switching element or the diode is connected between ground and a contact point of the first switching element and the inductor, and the two or more current control units are connected in parallel; wherein the calculation unit is configured to individually and sequentially stop said two or more current control units by setting the respective pulse modulation signal to the low level for a plurality of cycles of the respective pulse modulation signal, the drive circuit further comprises a current detection unit configured to detect the output current, and the calculation unit is configured to identify a current control unit of said two or more current control units that is faulty in accordance with a fluctuation in the output current detected when one of said two or more current control units to be stopped is stopped.