Solid state lighting apparatuses, circuits, methods, and computer program products providing targeted spectral power distribution output using pulse width modulation control
View Patent ↗A solid state lighting apparatus can include a variable color input signal configured to indicate a target color of light output from the apparatus. A string current Pulse Width Modulation (PWM) controller circuit can be coupled to the variable color input signal, where the string current PWM controller circuit can be configured to generate a plurality of PWM signals having respective variable duty cycles to enable/disable respective particular string currents for respective variable times as the variable color input signal changes.
1. A solid state lighting apparatus comprising:
a variable color input signal configured to change a target color of light output from the apparatus; and
a string current Pulse Width Modulation (PWM) controller circuit coupled to the variable color input signal, the string current PWM controller circuit configured to generate a plurality of PWM signals having respective variable duty cycles to enable/disable respective particular string currents for respective variable times to change the light output from the apparatus as the variable color input signal changes,
wherein the particular string currents comprise respective full-on string currents, and
wherein at least two of the respective full-on string currents are different from one another.
2. The apparatus of claim 1 further comprising:
a plurality of solid state Light Emitting Device (LED) strings, each of the LED strings configured to conduct one of the respective full-on string currents; and
a plurality of string current switching circuits, each configured to receive a respective one of the PWM signals to enable/disable one of the respective full-on string currents to flow through a respective one of the LED strings using the respective variable duty cycle.
3. The apparatus of claim 2 wherein the string current PWM controller circuit includes a plurality of PWM circuits configured to generate the plurality of PWM signals based on a level of the variable color input signal.
4. The apparatus of claim 3 wherein each of the PWM circuits has access to a PWM duty cycle value for the respective one of the LED strings at the level of the variable color input signal.
5. The apparatus of claim 3 further comprising:
a variable brightness input signal configured to indicate a target brightness level of the light output from the apparatus, wherein the string current PWM controller circuit is configured to combine the level of the variable color input signal with a level of the variable brightness input signal to provide the plurality of PWM signals.
6. The apparatus of claim 5 wherein the string current PWM controller circuit is configured to multiply the level of the variable color input signal with the level of the variable brightness input signal to provide a combined color/brightness input signal.
7. The apparatus of claim 6 wherein each of the PWM circuits has access to a PWM duty cycle value for the respective one of the LED strings at a level of the combined color/brightness input signal.
8. The apparatus of claim 2 wherein the string current PWM controller circuit includes a plurality of tuned current indications, each corresponding to a predetermined color value for one of the LED strings.
9. The apparatus of claim 8 wherein the string current PWM controller circuit includes a plurality of temperature compensation current indications, each corresponding to a predetermined current adjustment for the respective one of the LED strings based on a temperature of that LED string.
10. The apparatus of claim 9 wherein each of the tuned current indications is combined with a respective one of the temperature compensation current indications to provide an indication of the respective full-on string current.
11. The apparatus of claim 10 wherein the string current PWM controller circuit is configured to multiply a level of the variable color input signal with a level of a variable brightness input signal to provide a combined color/brightness input signal, the string current PWM controller circuit further including:
a plurality of average string current circuits, each configured to combine the respective indication of the full-on string current with a level of the combined color/brightness input signal to provide a respective average string current for each of the LED strings.
12. The apparatus of claim 5 wherein the string current PWM controller circuit further includes:
a plurality of brightness PWM circuits, each configured to generate a brightness PWM signal for the respective one of the LED strings based on the level of the variable brightness input signal;
a plurality of color PWM circuits, each configured to generate a color PWM signal for the respective one of the LED strings based on the level of the variable color input signal; and
a plurality of PWM combination circuits, each configured to combine a respective color PWM signal with a respective brightness PWM signal to provide one of the plurality of PWM signals.
13. The apparatus of claim 2 wherein the plurality of string current switching circuits each comprises a linear regulator circuit, a voltage controlled current source, a shunt circuit, or a switched converter circuit.
14. The apparatus of claim 12 wherein a frequency of the color PWM signals is at least 10 times greater than a frequency of the brightness PWM signals or wherein the frequency of the brightness PWM signals is at least 10 times greater than the frequency of the color PWM signals.
15. The apparatus of claim 1 wherein the variable color input signal is configured for manual input to change the target color of the light output from the apparatus.
16. A solid state lighting apparatus comprising:
a plurality of solid state Light Emitting Device (LED) strings, each of the LED strings configured to conduct a respective one of a plurality of particular string currents;
a variable color input signal configured to indicate a target color of light output from the apparatus;
a variable brightness input signal configured to indicate a target brightness level of the light output from the apparatus;
a string current Pulse Width Modulation (PWM) controller circuit including:
a color/brightness combiner circuit configured to multiply a level of the variable color input signal with a level of the variable brightness input signal to provide a combined color/brightness input signal; and
a plurality of PWM circuits configured to generate a plurality of PWM signals at respective variable duty cycles to enable/disable the respective particular string current for a respective variable time based on a level of the combined color/brightness input signal; and
a plurality of string current switching circuits, each configured to receive a respective one of the plurality of PWM signals and configured to enable/disable the respective particular string current to flow through a respective one of the LED strings using the respective variable duty cycle.
17. The apparatus of claim 16 wherein the respective particular string current comprises a respective full-on string current, wherein each of the PWM circuits has access to a PWM duty cycle value for the respective one of the LED strings at a level of the combined color/brightness input signal.
18. The apparatus of claim 17 wherein the string current PWM controller circuit includes a plurality of tuned current indications, each corresponding to a predetermined color value for one of the LED strings.
19. The apparatus of claim 18 wherein the string current PWM controller circuit includes a plurality of temperature compensation current indications, each corresponding to a predetermined current adjustment for the respective one of the LED strings based on a temperature of that LED string.
20. A solid state lighting apparatus comprising:
a plurality of solid state Light Emitting Device (LED) strings, each of the LED strings configured to conduct a respective one of a plurality of particular string currents;
a first variable spectral power distribution input signal configured to change a first target spectral characteristic of light output from the apparatus;
a second variable spectral power distribution input signal configured to change a second target spectral characteristic of the light output from the apparatus; and
a string current Pulse Width Modulation (PWM) controller circuit coupled to the first and second variable spectral power distribution input signals, the string current PWM controller circuit configured to combine respective levels of the first and second variable spectral power distribution input signals to provide a combined variable spectral power distribution input signal, and configured to generate a plurality of PWM signals having respective variable duty cycles to enable/disable respective particular string currents for respective variable times to change the light output from the apparatus as a level of the combined variable spectral power distribution input signal changes,
wherein the particular string currents comprise respective full-on string currents, and
wherein at least two of the respective full-on string currents are different from one another.
21. The apparatus of claim 20 wherein the first and second variable spectral power distribution input signals respectively comprise:
a variable color input signal configured to indicate a target color of light output from the apparatus; and
a variable input indicating a target value for the light emitted by the apparatus including a Color Quality Scale (CQS), a dominant wavelength, a Gamut Area Index (GAI), a peak wavelength, a scotopic luminance (or lumens) versus photopic luminance (S/P) ratio, a luminous efficacy, and/or a CRI value.