Patent ID: 8305011

Claim:
A driving circuit which drives a plurality of light emitting elements, comprising: a plurality of driving terminals which are respectively provided to the plurality of light emitting elements, and each of which is to be connected to the anode of the corresponding light emitting element; a booster circuit which receives an input voltage and boosts the input voltage; a plurality of constant current sources which are respectively provided to the plurality of light emitting elements, and one terminal of each of which is connected to the respective light emitting element via the driving terminal; a plurality of switches which are respectively provided to the plurality of constant current sources, and each of which receives the input voltage and the output voltage of the booster circuit and selectively applies a voltage selected from the input voltage and the output voltage of the booster circuit across the corresponding constant current source and the corresponding light emitting element; and a control circuit which monitors the voltage at each of the plurality of driving terminals, and which controls the connection state of each of the switches based upon the voltage at the corresponding driving terminal, wherein the driving circuit is monolithically integrated on a single semiconductor substrate, and wherein the control circuit controls the connection state of each of the switches based upon the voltage across the constant current source connected to the corresponding driving terminal, and wherein the control circuit includes a plurality of comparators which are respectively provided to the plurality of driving terminals, and each of which compares the voltage across the corresponding constant current source with a predetermined threshold voltage, and wherein the control circuit switches the connection state of each of the switches based upon the output of the corresponding comparator.