Methods and apparatus for controlling series-connected LEDs

A method of energizing a plurality of LEDs connected in series between a first node and a second node, wherein a series current flows between the first node and the second node when an operating voltage is applied across the first node and the second node, the method comprising:

• A) monitoring at least one parameter representative of the operating voltage;
• B) determining a maximum number of LEDs of the at least two LEDs that can be energized by the operating voltage;
• and
• C) when the maximum number is less than a total number of all of the at least two LEDs connected in series, shorting out at least one of the plurality of LEDs so that less than all of the plurality of LEDs are simultaneously energized.

An apparatus, comprising:

• a plurality of LEDs connected in series between a first node and a second node, wherein a series current flows between the first node and the second node when an operating voltage is applied across the first node and the second node;
• a plurality of controllable current paths, each current path connected in parallel with a corresponding one of the plurality of LEDs for diverting the series current around the corresponding one of the plurality of LEDs;
• a current source connected in series with the plurality of LEDs between the first node and the second node for setting the series current;
• and
• at least one controller for monitoring at least one parameter related to the operating voltage and for intermittently controlling the plurality of controllable current paths so as to divert the series current around respective corresponding ones of the plurality of LEDs in a timed sequence when the at least one monitored parameter indicates that the operating voltage is less than a predetermined threshold value, such that less than all of the plurality of LEDs are simultaneously energized.

An automotive lighting apparatus, comprising:

• at least one integrated circuit chip, comprising:
• a first number of LEDs connected in series between a first node and a second node, wherein a series current flows between the first node and the second node when an operating voltage is applied across the first node and the second node;
• a second number of controllable current paths, wherein the second number is equal to or less than the first number, each current path connected in parallel with a corresponding one of the first number LEDs for diverting the series current around the corresponding one of the first number of LEDs;
• a current source connected in series with the first number of LEDs between the first node and the second node for setting the series current;
• and
• at least one controller for monitoring at least one parameter representative of the operating voltage and determining a maximum number of LEDs of the first number of LEDs that can be energized by the operating voltage, the at least one controller controlling the second number of controllable current paths so as to divert the series current around respective corresponding ones of the first number of LEDs when the maximum number is less than the first number, such that less than all of the first number of LEDs are simultaneously energized;
• and
• a package for the at least one integrated circuit chip, the package including at least one first electrical connector configured to mate with a complimentary electrical connector or wire harness of an automobile, the at least one first electrical connector including at least a first lead electrically connected to the first node and a second lead electrically connected to the second node for applying the operating voltage across the first node and the second node.