Drive circuit and light source device

A drive circuit comprising:

• a switching circuit configured to switch between a first state and a second state to cause a light-emitting element to perform pulse oscillation, wherein,
• in the first state, light is emitted from the light-emitting element by supplying the light-emitting element with a current having a magnitude equal to or greater than a threshold current that enables the light-emitting element to emit light having an output equal to or greater than a predetermined output, and
• in the second state, the magnitude of the current supplied to the light-emitting element is less than the threshold current;
• and
• a direct current adjustment circuit configured to supply, to the light-emitting element, a bias current within a range less than the threshold current of the light-emitting element in the second state, the bias current having a magnitude corresponding to a magnitude of undershoot occurring at a falling edge of the pulse oscillation, wherein
• the direct current adjustment circuit includes:
• a transistor configured to adjust a magnitude of the bias current;
• a resistive element configured to detect the magnitude of the bias current;
• and
• a circuit configured to control a current supplied to the transistor based on a reference signal serving as a reference of the magnitude of the bias current and a detection signal corresponding to a detection result obtained by the resistive element such that the bias current having the magnitude corresponding to the reference signal is supplied to the light-emitting element.

A light source device comprising:

• a light-emitting element;
• and
• a drive circuit configured to drive the light-emitting element, wherein
• the drive circuit comprises:
• a switching circuit configured to switch between a first state and a second state to cause the light-emitting element to perform pulse oscillation, wherein,
• in the first state, light is emitted from the light-emitting element by supplying the light-emitting element with a current having a magnitude equal to or greater than a threshold current that enables the light-emitting element to emit light having an output equal to or greater than a predetermined output, and
• in the second state, the magnitude of the current supplied to the light-emitting element is less than the threshold current;
• a direct current adjustment circuit configured to supply, to the light-emitting element, a bias current within a range less than the threshold current of the light-emitting element in the second state, the bias current having a magnitude corresponding to a magnitude of undershoot occurring at a falling edge of the pulse oscillation;
• and
• a control circuit configured to control operation of the direct current adjustment circuit to detect the magnitude of the undershoot occurring at the falling edge of the pulse oscillation based on a detection result of at least one of a voltage applied to the light-emitting element or the current supplied to the light-emitting element, such that the bias current having the magnitude corresponding to the magnitude of the detected undershoot is supplied to the light-emitting element.

A light source device comprising:

• a light-emitting element;
• and
• a drive circuit configured to drive the light-emitting element, wherein
• the drive circuit comprises:
• a switching circuit configured to switch between a first state and a second state to cause the light-emitting element to perform pulse oscillation, wherein,
• in the first state, light is emitted from the light-emitting element by supplying the light-emitting element with a current having a magnitude equal to or greater than a threshold current that enables the light-emitting element to emit light having an output equal to or greater than a predetermined output, and
• in the second state, the magnitude of the current supplied to the light-emitting element is less than the threshold current;
• and
• a direct current adjustment circuit configured to supply, to the light-emitting element, a bias current within a range less than the threshold current of the light-emitting element in the second state, the bias current having a magnitude corresponding to a magnitude of undershoot occurring at a falling edge of the pulse oscillation, wherein
• the direct current adjustment circuit includes:
• a transistor configured to adjust a magnitude of the bias current;
• a resistive element configured to detect the magnitude of the bias current;
• and
• a circuit configured to control a current supplied to the transistor based on a reference signal serving as a reference of the magnitude of the bias current and a detection signal corresponding to a detection result obtained by the resistive element such that the bias current having the magnitude corresponding to the reference signal is supplied to the light-emitting element.