Linear bypass electrical circuit for driving led strings

A method of operating an electrical circuit for driving a light emitting diode (LED) based lamp comprising:

• driving a first light emitting diode (LED) string including at least one LED with a power supply;
• driving a second LED string including one or more color strings with the power supply, each of the one or more color strings including at least one LED, the one or more color strings electrically coupled in series, the first LED string and the second LED string electrically coupled at an anode terminal of both the first LED string and the second LED string;
• operating a first transistor in linear mode, the first transistor electrically coupled to the first LED string in series;
• operating a second transistor in linear mode, the second transistor electrically coupled to the second LED string in series;
• and
• operating a color bypass transistor in linear mode, the color bypass transistor electrically coupled to a particular color string of the one or more color strings, the bypass transistor electrically coupled in parallel to the particular color string.

A lighting apparatus comprising:

• a first light emitting diode (LED) string including at least one LED;
• a first transistor electrically coupled to the first LED string in series, the first transistor capable of operating in a linear mode;
• a second LED string including one or more color strings, each of the one or more color strings including at least one LED, the one or more color strings electrically coupled in series, the first LED string and the second LED string electrically coupled at an anode terminal of both the first LED string and the second LED string;
• a second transistor electrically coupled to the second LED string in series, the second transistor capable of operating in a linear mode;
• and
• a color bypass transistor electrically coupled to a particular color string of the one or more color strings in parallel, the color bypass transistor capable of operating in a linear mode.

An electrical circuit comprising:

• a light emitting diode (LED) string including multiple color strings, the multiple color strings electrically coupled in series, each including at least one LED;
• a set of color bypass transistors electrically coupled each of the multiple color strings in parallel, each of the color bypass transistors capable of operating in a linear mode and diverting a portion of current from each of the multiple color strings;
• and
• a control device electrically coupled to control terminals of the set of color bypass transistors to switch between voltages applied to the control terminals of the color bypass transistors;
• wherein the control device adjust the voltages applied such that current ratio through the multiple color strings produces illumination substantially tracking color intensity ratios along the Planckian locus in a chromaticity space.

An electric circuit comprising:

• first circuit contact points for attaching a first light emitting diode (LED) string;
• a first transistor electrically coupled in series to the first circuit contact points of the first LED string, the first transistor capable of operating in a linear mode;
• second circuit contact points for attaching a second LED string including one or more contact point subsets for attaching one or more color strings in series, the first circuit contact points and the second circuit contact points electrically coupled at an anode terminal of both the first LED string and the second LED string;
• a second transistor electrically coupled in series to the second circuit contact points in series, the second transistor capable of operating in a linear mode;
• and
• a color bypass transistor electrically coupled in parallel to a particular contact point subset for a particular color string of the one or more color strings, the color bypass transistor capable of operating in a linear mode.