Patent ID: 11917737
Assignee: BIO-RAD LABORATORIES, INC.
Field: Electrical machinery, apparatus, energy (Electrical engineering)
Classification: CPC H | IPC H

Claim 15:
16. A method of controlling current through parallel LED pathways, the method comprising:
generating a current with a current source coupled with a first LED pathway and a second LED pathway, wherein,
the first LED pathway comprises:
a first set of LEDs, the first set of LEDs comprising one or more first LEDs;
a first transistor coupled to the first set of LEDs and configured to control a first current through the first set of LEDs by altering a first conductivity between a first source and a first drain based on a first voltage applied to a first gate of the first transistor; and
a first measurement node comprising a first sensed voltage; and

wherein the second LED pathway comprises:
a second set of LEDs, the second set of LEDs comprising one or more second LEDs;
a second transistor coupled to the second set of LEDs and configured to control a second current through the second set of LEDs by altering a second conductivity between a second source and a second drain based on a second voltage applied to a second gate of the second transistor; and
a second measurement node comprising a second sensed voltage;

applying a first bias voltage to the first non-inverting input of a first differential amplifier;
applying a second bias voltage to the second non-inverting input of a second differential amplifier;
receiving a first sense voltage and a second sense voltage as inputs to a first differential amplifier;
adjusting the first conductivity of the first transistor by applying a first voltage output from the first differential amplifier to the first gate of the first transistor;
receiving the first sense voltage and the second sense voltage as inputs to a second differential amplifier; and
adjusting the second conductivity of the second transistor by applying a second voltage output from the second differential amplifier to the second gate of the second transistor, wherein the first conductivity of the first transistor and the second conductivity of the second transistor are adjusted to match the first current passing through the first LED pathway to the second current passing through the second LED pathway.