Patent ID: 7667683

Claim:
A light source driving circuit for driving a series of Light Emitting Diodes (LEDs), a first end of the series of LEDs electrically connected to a ground end, the light source driving circuit comprising: a voltage signal source; a voltage-controlled current source comprising: a first amplifier comprising: a positive input end, electrically connected to the voltage signal source; a negative input end; and an output end; a first Bipolar Junction Transistor (BJT), comprising: an emitter, electrically connected to the negative input end of the first amplifier; a base, electrically connected to the output end of the first amplifier; and a collector; a first resistor, electrically connected between the negative input end of the first amplifier and the ground end; a second amplifier comprising: a positive input end, electrically connected to the collector of the first BJT; a negative input end; and an output end; a second resistor, electrically connected between the collector of the first BJT and a biasing source; a third resistor, electrically connected between the negative input end of the second amplifier and the biasing source; and a second BJT comprising: an emitter, electrically connected to the negative end of the second amplifier; a base, electrically connected to the output end of the second amplifier; and a collector, electrically connected to a second end of the series of LEDs.