Patent ID: 8497982

Claim:
A light source circuit for an optical sensor system, the circuit comprising: a power supply to provide a regulated direct current (DC) voltage output; a light source comprising a plurality of series connected light emitting diodes (LEDs); a current source coupled to the power supply and the light source to receive the regulated DC voltage output and to provide a current output; a switch, the switch being configured to allow the current output to through the plurality of series connected LEDs from the current source when the switch is closed and to prevent the current output through the plurality of series connected LEDs when the switch is open; a high voltage supply circuit coupled to the plurality of series connected LEDs to provide a high voltage output; a second switch, the second switch being configured to connect the high voltage output to the plurality of series connected LEDs from the high voltage supply when the second switch is closed and to disconnect the high voltage output from the plurality of series connected LEDs when the second switch is open; a drive circuit to open and close the second switch, the drive circuit being configured to close the second switch at the start of an on time for the plurality of series connected LEDs to connect the high voltage output to the plurality of series connected LEDs and to open the second switch during a remainder of the on time of the plurality of series connected LEDs to allow the current source to provide the current output to the plurality of series connected LEDs.