# US 2014/0197750 A1 · Systems and methods for controlling solid state lighting during dimming and lighting apparatus incorporating such systems and/or methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197750 A1 - Document ID: US20140197750A1 - Status: Published application - Kind: A1 - Application number: 13/742,008 - Filed: 2013-01-15 - Published: 2014-07-17 - Earliest claimed: 2013-01-15 - Assignees: Cree, Inc. - Applicants: Cree, Inc. - Inventors: Mark Cash - Web page: https://patentgrep.com/patent/US20140197750A1 ## CPC - H05B 45/20: Controlling the colour of the light - H05B 45/48: having LEDs organised in strings and incorporating parallel shunting devices - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract A lighting apparatus having a plurality of light-emitting devices (LEDs) can include at least one first LED that is configured to emit first chromaticity light, at least one second LED that is configured to emit second chromaticity light, and at least one additional LED that is configured to emit third chromaticity light. A control circuit can be operatively coupled to the plurality of light-emitting devices and configured to cause a color temperature produced by the plurality of LEDs to vary substantially in conformance with a Planckian locus in response to a dimming control input less than about 1800K. ## Claims ### Claim 1 A lighting apparatus comprising: a plurality of light-emitting devices (LEDs) comprising at least one first LED configured to emit first chromaticity light, at least one second LED configured to emit second chromaticity light, and at least one additional LED configured to emit third chromaticity light; and a control circuit operatively coupled to the plurality of light-emitting devices and configured to cause a color temperature produced by the plurality of LEDs to vary substantially in conformance with a Planckian locus in response to a dimming control input less than about 1800K. ### Claim 2 (depends on 1) The apparatus of claim 1 wherein the at least one first LED comprises a read/orange LED, the at least one second LED comprises a Blue-Shifted-Yellow (BSY) LED, and the at least one additional LED comprises an amber LED. ### Claim 3 (depends on 2) The apparatus of claim 2 further comprising: a bypass circuit, operatively coupled to the control circuit, the bypass circuit including a variable resistance circuit and the at least one amber LED, wherein the variable resistance circuit is configured to increasingly bypass current around the at least one BSY LED through the at least one amber LED as the dimming control input decreases a brightness level of the plurality of LEDs. ### Claim 4 (depends on 3) The apparatus of claim 3 wherein the at least one BSY LED comprises a first BSY LED configured to emit first BSY light and the plurality of LEDs comprises a second BSY LED configured to emit second BSY light having greater yellow content than the first BSY light, the apparatus further comprising: a second bypass circuit, operatively coupled to the control circuit, the second bypass circuit including a second variable resistance circuit and a second amber LED, wherein the second variable resistance circuit is configured to increasingly bypass current around the second BSY LED through the second amber LED as the dimming control input decreases the brightness level of the plurality of LEDs. ### Claim 5 (depends on 2) The apparatus of claim 2 wherein the plurality of LEDs are arranged in a serially connected LED string, the apparatus further comprising: a bypass circuit, coupled in parallel across the at least one amber LED in the LED string, the bypass circuit being operatively coupled to the control circuit and configured to increasingly bypass current around the at least one amber LED as the dimming control input increases a brightness level of the plurality of LEDs. ### Claim 6 (depends on 2) The apparatus of claim 2 wherein the plurality of LEDs comprises: a first LED string including the at least one BSY LED coupled in series with the at least one red/orange LED; and a second LED string, coupled in parallel with the first LED string, including the at least one amber LED, wherein the control circuit is configured to increase current through the first LED string while decreasing current through the second string of LEDs as the dimming control input increases a brightness level of the plurality of LEDs. ### Claim 7 (depends on 6) The apparatus of claim 6 further comprising: a bypass circuit coupled across the at least one amber LED and operatively coupled to the control circuit, the bypass circuit being configured to increasingly bypass current around the at least one amber LED as the dimming control input increases the brightness level of the plurality of LEDs. ### Claim 8 (depends on 2) The apparatus of claim 2 wherein the plurality of LEDs comprises: a first LED string including the at least one BSY LED coupled in series with the at least one red/orange LED; a second LED string, coupled in parallel with the first LED string, including the at least one amber LED; and an RC circuit coupled in series with the second LED string, and configured to discharge through the second LED string when the first string of LEDs is off. ### Claim 9 A lighting apparatus comprising: a control circuit operatively coupled to a plurality of light-emitting devices (LEDs) and configured to reduce current through at least one first chromaticity LED included in the plurality while increasing current through at least one additional chromaticity LED included in the plurality to cause a color temperature less than about 1800K produced by the plurality of LEDs to vary substantially in conformance with a Planckian locus in response to a dimming control input. ### Claim 10 (depends on 9) The apparatus of claim 9 wherein the at least one first chromaticity LED comprises at least one Blue-Shifted-Yellow (BSY) LED configured to emit BSY light, the at least one additional chromaticity LED comprises at least one additional LED configured to emit additional light, the plurality of LEDs further comprising at least one red/orange LED configured to emit red/orange light. ### Claim 11 (depends on 10) The apparatus of claim 10 wherein the additional light comprises a predominant non-blue color. ### Claim 12 (depends on 10) The apparatus of claim 10 wherein the control circuit is configured to reduce the current through the at least one BSY LED while increasing the current through the at least one additional LED at brightness levels less than about 30% of a maximum brightness level. ### Claim 13 (depends on 10) The apparatus of claim 10 wherein the additional light comprises a wavelength in a range from about 585 nm to about 500 nm. ### Claim 14 (depends on 10) The apparatus of claim 10 wherein the at least one additional LED comprises at least one amber LED configured to emit amber light. ### Claim 15 (depends on 10) The apparatus of claim 10 further comprising: a bypass circuit, operatively coupled to the control circuit, the bypass circuit including a variable resistance circuit and the at least one additional LED, wherein the variable resistance circuit is configured to increasingly bypass current around the at least one BSY LED through the at least one additional LED as the dimming control input decreases the brightness level of the plurality of LEDs. ### Claim 16 (depends on 15) The apparatus of claim 15 wherein the at least one BSY LED comprises a first BSY LED configured to emit first BSY light and the plurality of LEDs comprises a second BSY LED configured to emit second BSY light having greater yellow content than the first BSY light, the apparatus further comprising: a second bypass circuit, operatively coupled to the control circuit, the second bypass circuit including a second variable resistance circuit and a second additional LED, wherein the second variable resistance circuit is configured to increasingly bypass current around the second BSY LED through the second additional LED as the dimming control input decreases the brightness level of the plurality of LEDs. ### Claim 17 (depends on 9) The apparatus of claim 9 wherein the plurality of LEDs are arranged in a serially connected LED string, the apparatus further comprising: a bypass circuit, coupled in parallel across the at least one additional LED in the LED string, the bypass circuit being operatively coupled to the control circuit and configured to increasingly bypass current around the at least one additional LED as the dimming control input increases a brightness level of the plurality of LEDs. ### Claim 18 (depends on 10) The apparatus of claim 10 wherein the plurality of LEDs comprises: a first LED string including the at least one BSY LED coupled in series with the at least one red/orange LED; and a second LED string, coupled in parallel with the first LED string, including the at least one additional LED, wherein the control circuit is configured to increase current through the first LED string while decreasing current through the second string of LEDs as the dimming control input increases a brightness level of the plurality of LEDs. ### Claim 19 (depends on 18) The apparatus of claim 18 further comprising: a bypass circuit coupled across the at least one additional LED and operatively coupled to the control circuit, the bypass circuit being configured to increasingly bypass current around the at least one additional LED as the dimming control input increases the brightness level of the plurality of LEDs. ### Claim 20 (depends on 10) The apparatus of claim 10 wherein the plurality of LEDs comprises: a first LED string including the at least one BSY LED coupled in series with the at least one red/orange LED; a second LED string, coupled in parallel with the first LED string, including the at least one additional LED; and an RC circuit coupled in series with the second LED string, and configured to discharge through the second LED string when the first LED string switches off. ### Claim 21 A method of operating a lighting apparatus including a plurality of light- emitting devices (LEDs) comprising at least one first LED configured to emit first chromaticity light, at least one second LED configured to emit second chromaticity light, and at least one additional LED configured to emit additional chromaticity light, the method comprising: reducing current through the at least one second LED; and increasing current through the at least one additional LED, while reducing the current through the at least one second LED, to cause a color temperature produced by the plurality of LEDs to vary substantially in conformance with a Planckian locus in response to a dimming control input. ### Claim 22 (depends on 21) The method of claim 21 wherein the at least one first LED comprises a read/orange LED configured to emit red/orange chromaticity light, the at least one second LED comprises a Blue-Shifted-Yellow (BSY) LED configured to emit BSY chromaticity light, and the at least one additional LED comprises an amber LED configured to emit amber chromaticity light. ### Claim 23 (depends on 21) The method of claim 21 wherein the additional light comprises a predominant non-blue color. ### Claim 24 (depends on 22) The method of claim 22 wherein reducing the current comprises reducing the current through the at least one BSY LED while increasing the current through the at least one additional LED at brightness levels less than about 30% of a maximum brightness level. ### Claim 25 (depends on 21) The method of claim 21 wherein the additional light comprises a wavelength in a range from about 585 nm to about 500 nm. ### Claim 26 (depends on 21) The method of claim 21 wherein the at least one additional LED comprises at least one amber LED configured to emit amber light. ### Claim 27 (depends on 22) The method of claim 22 further comprising: increasingly bypassing current around the at least one BSY LED through the at least one additional LED as the dimming control input decreases the brightness level of the plurality of LEDs. ### Claim 28 (depends on 22) The method of claim 22 wherein the at least one BSY LED comprises a first BSY LED configured to emit first BSY light and the plurality of LEDs comprises a second BSY LED configured to emit second BSY light having greater yellow content than the first BSY light, the method further comprising: increasingly bypassing current around a second BSY LED through a second additional LED as the dimming control input decreases the brightness level of the plurality of LEDs. ### Claim 29 (depends on 22) The method of claim 22 wherein the plurality of LEDs are arranged in a serially connected LED string, the method further comprising: increasingly bypassing current around the at least one additional LED as the dimming control input increases a brightness level of the plurality of LEDs. ### Claim 30 (depends on 22) The method of claim 22 wherein the plurality of LEDs comprises: a first LED string including the at least one BSY LED coupled in series with the at least one red/orange LED and a second LED string, coupled in parallel with the first LED string, including the at least one additional LED, the method further comprising: increasing current through the first LED string while decreasing current through the second string of LEDs as the dimming control input increases a brightness level of the plurality of LEDs. ### Claim 31 (depends on 30) The method of claim 30 further comprising: increasingly bypassing current around the at least one additional LED as the dimming control input increases the brightness level of the plurality of LEDs. ### Claim 32 (depends on 22) The method of claim 22 wherein the plurality of LEDs comprises a first LED string including the at least one BSY LED coupled in series with the at least one red/orange LED, a second LED string, coupled in parallel with the first LED string, including the at least one additional LED, the method further comprising: discharging current through the second LED string when the first LED string switches off.