Laser diode driving circuit
AssigneeRicoh Company, Ltd.
InventorShinichi Kubota
Life of this patent
Estimating the term…
Abstract
A disclosed laser diode driving circuit causes a laser diode to emit light by varying a current value of a current source in accordance with a control signal input externally and supplying a current that is the same as or proportional to the current value to the laser diode. The driving circuit includes correction circuitry for generating a reference forward voltage as a reference for the laser diode in accordance with a predetermined driving current for driving the laser diode, generating a forward voltage for the laser diode in accordance with the predetermined driving current, and correcting a current supplied to the laser diode so that the forward voltage becomes the same as the reference forward voltage.
Claims21
A laser diode driving circuit for causing a laser diode to emit light by varying a current value of a current source in accordance with a control signal input externally and supplying a current that is the same as or proportional to the current value to the laser diode, comprising:
- correction circuitry for generating a reference forward voltage as a reference for the laser diode in accordance with a predetermined driving current for driving the laser diode;
- generating a forward voltage for the laser diode in accordance with the predetermined driving current;
- and
- correcting a current supplied to the laser diode so that the forward voltage becomes the same as the reference forward voltage,
- wherein the correction circuitry includes:
- first and second pseudo laser diodes having current-voltage characteristics that are the same as or proportional to that of the laser diode;
- a first current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the first pseudo laser diode;
- a second current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the second pseudo laser diode;
- a third current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the laser diode;
- a fourth current mirror circuit for outputting a current in accordance with the current value to each of the first, the second and the third current mirror circuits;
- and
- a correction circuit for adding a current to an input terminal of each of the first and the second current mirror circuits so that a forward voltage of the first pseudo laser diode becomes the same as a forward voltage of the second pseudo laser diode;
- wherein the second current mirror circuit has the same circuit structure as the third current mirror circuit;
- a consumption current of the second current mirror circuit is proportional to a consumption current of the third current mirror circuit;
- and the correction circuit adds a current to an input terminal of the third current mirror circuit, said current added to the third current mirror circuit input terminal being proportional to the current added to the second current mirror circuit input terminal.
A laser diode driving circuit for causing a laser diode to emit light by varying a current value of a current source in accordance with a control signal input externally and supplying a current that is the same as or proportional to the current value to the laser diode, comprising:
- correction circuitry for generating a reference forward voltage as a reference for the laser diode in accordance with a predetermined driving current for driving the laser diode;
- generating a forward voltage for the laser diode in accordance with the predetermined driving current;
- and
- correcting a current supplied to the laser diode so that the forward voltage becomes the same as the reference forward voltage, wherein the correction circuitry includes:
- a first pseudo laser diode having current-voltage characteristics that are the same as or proportional to that of the laser diode, the current from the current source being supplied to the first pseudo laser diode;
- a second pseudo laser diode having current-voltage characteristics that are the same as or proportional to that of the laser diode;
- a second current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the second pseudo laser diode;
- a third current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the laser diode;
- and
- a correction circuit for adding a current to an input terminal of each of the second and the third current mirror circuits so that a forward voltage of the first pseudo laser diode becomes the same as a forward voltage of the second pseudo laser diode;
- wherein the second current mirror circuit has the same circuit structure as the third current mirror circuit;
- and a consumption current of the second current mirror circuit is proportional to a consumption current of the third current mirror circuit.
A laser diode driving circuit for causing a laser diode to emit light by varying a current value of a current source in accordance with a control signal input externally and supplying a current that is the same as or proportional to the current value to the laser diode, comprising:
- correction circuitry for generating a reference forward voltage as a reference for the laser diode in accordance with a predetermined driving current for driving the laser diode;
- generating a forward voltage for the laser diode in accordance with the predetermined driving current;
- and
- correcting a current supplied to the laser diode so that the forward voltage becomes the same as the reference forward voltage, wherein the correction circuitry includes:
- a first pseudo laser diode having current-voltage characteristics that are the same as or proportional to that of the laser diode, the current from the current source being supplied to the first pseudo laser diode;
- a second pseudo laser diode having current-voltage characteristics that are the same as or proportional to that of the laser diode;
- a second current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the second pseudo laser diode;
- a third current mirror circuit for generating a current in accordance with an input current and supplying the generated current to the laser diode;
- and
- a current supplying circuit for supplying a current in accordance with a voltage at a node between the current source and the first pseudo laser diode, to input terminals of the second and third current mirror circuits;
- wherein the first and second pseudo laser diodes constitute a fourth current mirror circuit in which the first pseudo laser diode forms an output side transistor and the second pseudo laser diode forms an input side transistor;
- the second current mirror circuit has the same circuit structure as the third current mirror circuit;
- and a consumption current of the second current mirror circuit is proportional to a consumption current of the third current mirror circuit.
Dependencies are inferred from the claim text.