# US 2014/0197751 A1 · Spectral Shift Control for Dimmable AC LED Lighting > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2014/0197751 A1 - Document ID: US20140197751A1 - Status: Published application - Kind: A1 - Application number: 14/160,721 - Filed: 2014-01-22 - Published: 2014-07-17 - Earliest claimed: 2010-05-24 - Assignees: Once Innovations, Inc. - Applicants: Once Innoations, Inc. - Inventors: Zdenko Grajcar - Web page: https://patentgrep.com/patent/US20140197751A1 ## CPC - H05B 45/40: Details of LED load circuits - H05B 45/20: Controlling the colour of the light - H05B 45/31: Phase-control circuits - H05B 45/35: Balancing circuits - H05B 45/36: Circuits for reducing or suppressing harmonics, ripples or electromagnetic interferences [EMI] - H05B 45/3725: Switched mode power supply [SMPS] - H05B 45/42: Antiparallel configurations - H05B: ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL ## Abstract Apparatus and associated methods involve operation of an LED light engine in which a relative intensities of selected wavelengths shift as a function of electrical excitation. In an illustrative example, current may be selectively and automatically diverted substantially away from at least one of a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level. The diversion current may be smoothly reduced in transition as the excitation current or voltage rises substantially above the predetermined threshold level. A color temperature of the light output may be substantially changed as a predetermined function of the excitation voltage. For example, some embodiments may substantially increase or decrease a color temperature output by a solid state light engine in response to dimming the AC voltage excitation (e.g., by phase-cutting or amplitude modulation). ## Claims ### Claim 1 An apparatus for a solid state light engine, the apparatus comprising: a pair of terminals to receive an applied electrical excitation for a load; a first network in the load, wherein the first network includes a first plurality of light emitting diodes (LEDs) arranged in series connection to form a first current path, the first plurality of LEDs having a first color characteristic; a second network in the load, wherein the second network includes a second plurality of LEDs arranged in series connection to form a second current path, the second plurality of LEDs having a second color characteristic that is substantially different form the first color characteristic; and, means for selectively diverting current away from at least one of the first and second networks of LEDs, wherein a color characteristic of the combined light output of the first and second networks varies between the first color characteristic and the second color characteristic as a function of the applied electrical excitation, and wherein a rate of change of intensity for a first peak wavelength is at least 40% higher than a rate of change of intensity for a second peak wavelength as the applied electrical excitation is varied within a limited range that encompasses 80% of rated voltage. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein an upper limit of the limited range of applied electrical excitation is less than about 95% of rated voltage. ### Claim 3 (depends on 1) The apparatus of claim 1, wherein a lower limit of the limited range of applied electrical excitation is about 75% of rated voltage. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein a ratio for the rate of change of intensity for the first peak wavelength to the rate of change of intensity for the second peak wavelength is at least 2 within the limited range. ### Claim 5 (depends on 4) The apparatus of claim 4, wherein the ratio is at least 3 for a portion of the limited range. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein the means for selectively diverting current operates to substantially increase a measured color temperature in response to reduction in an applied voltage. ### Claim 7 (depends on 6) The apparatus of claim 6, wherein the reduction in the applied voltage is associated with a periodic voltage signal processed by a phase-cutting module. ### Claim 8 (depends on 6) The apparatus of claim 6, wherein the reduction in the applied voltage is associated with an amplitude modulated periodic voltage signal. ### Claim 9 (depends on 6) The apparatus of claim 6, wherein the color temperature increases by at least about 3% in response to reduction in the applied voltage. ### Claim 10 (depends on 6) The apparatus of claim 6, wherein the color temperature increases by at least about 28% in response to reduction in the applied voltage. ### Claim 11 (depends on 1) The apparatus of claim 1, wherein the means for selectively diverting current operates to substantially decrease a color temperature in response to reduction in an applied voltage. ### Claim 12 (depends on 11) The apparatus of claim 11, wherein the reduction in the applied voltage is associated with a periodic voltage signal processed by a phase-cutting module. ### Claim 13 (depends on 11) The apparatus of claim 11, wherein the reduction in the applied voltage is associated with an amplitude modulated periodic voltage signal. ### Claim 14 (depends on 11) The apparatus of claim 11, wherein the color temperature decreases by at least about 16% in response to reduction in the applied voltage. ### Claim 15 (depends on 1) The apparatus of claim 1, wherein the first network further comprises at least one string of one or more series-connected LEDs arranged in a parallel connection with the first current path. ### Claim 16 (depends on 1) The apparatus of claim 1, wherein the second network further comprises at least one string of one or more series-connected LEDs arranged in a parallel connection with the second current path. ### Claim 17 (depends on 1) The apparatus of claim 1, wherein the second network is connected in a series arrangement with the first network. ### Claim 18 (depends on 1) The apparatus of claim 1, wherein the second network is connected in a parallel arrangement with the first network. ### Claim 19 (depends on 1) The apparatus of claim 1, wherein the degree of current diversion by the selective current diverting means varies as a function of the applied electrical excitation. ### Claim 20 (depends on 1) The apparatus of claim 1, wherein the applied electrical excitation comprises a substantially sinusoidal voltage. ### Claim 21 (depends on 1) The apparatus of claim 1, wherein the applied electrical excitation comprises an alternating current. ### Claim 22 (depends on 1) The apparatus of claim 1, further comprising a rectifier module to supply a substantially unidirectional current to the first network and the second network.