Patent ID: 8373348

Claim:
A drive circuit configured to drive a parallel array of light emitting diodes (LEDs), the drive circuit comprising: a switching control signal generator including: an oscillator configured to receive a light-adjusting square wave signal, a first D flip-flop having a clock input terminal configured to receive the light-adjusting square wave signal, wherein a D input terminal is shorted with a negative output terminal, a second D flip-flop having a clock input terminal connected to a clock signal output terminal of the oscillator, wherein a D input terminal is shorted with a negative output terminal, and a logic gate having a first input terminal connected to a positive output terminal of the second D flip-flop, a second input terminal connected to a positive output terminal of the first D flip-flop, and an output terminal configured to deliver a switching control signal having a period distributed substantially equally between a first state and a second state during the LEDs are lighting; a plurality of switches, each configured to be coupled to a respective LED in the parallel array of LEDs; a plurality of sampling resistors, each coupled to a respective switch in the plurality of switches and configured to receive a drive current when the respective switch is in a closed state; a plurality of chopper operational amplifiers, each chopper operational amplifier configured to receive a reference voltage and the switching control signal and generate an input offset voltage configured to control a respective switch in the plurality of switches, wherein each chopper operational amplifier includes a differential amplifier including an input transistor pair and a current mirror transistor pair; wherein the input transistor pair and current mirror transistor pair are mismatched, such that when the switching control signal is switched between the first state and the second state, electrical positions of the input transistor pair switch and electrical positions of the current mirror transistor pair switch to thereby cause a reversing of polarity of the input offset voltage of the chopper operational amplifier.