Patent ID: 7642724

Claim:
A light emitting element driving circuit comprising: a driving current supply circuit, connected to a light emitting element in series between a first power supply and a second power supply, adapted to supply a driving current to the light emitting element according to a voltage of a control terminal; a driving current determination circuit adapted to determine and output the current according to an amount of output light of the light emitting element; a current/voltage conversion circuit adapted to convert the current determined by the driving current determination circuit into a voltage and output the converted voltage to the control terminal of the driving current supply circuit in a case where a control signal is in a first state, and to electrically shield its output voltage terminal from the control terminal of the driving current supply circuit in a case where the control signal is in a second state; and a reset circuit adapted to connect the control terminal of the driving current supply circuit to the second power supply in the case where the control signal is in the second state, wherein the current/voltage conversion circuit includes a first field effect transistor of which a drain is connected to an output terminal of the driving current determination circuit, a source is connected to the second power supply, and a gate is connected to a control terminal of the driving current supply circuit, and a first switch which is connected between the drain of the first field effect transistor and the control terminal of the driving current supply circuit, comes to be in a conductive state in the case where the control signal is in the first state, and comes to be in a non-conductive state in the case where the control signal is in the second state, and wherein the reset circuit includes a second switch which is connected between the control terminal of the driving current supply circuit and the second power supply, comes to be in a non-conductive state in the case where the control signal is in the first state, and comes to be in a conductive state in the case where the control signal is in the second state.