Color temperature controlled and low THD LED lighting devices and systems and methods of driving the same
The purposes of the devices described herein are to provide an LED lighting device capable of efficiently and economically emitting light having a selectable color temperature or a warm-on-dim feature when driven with AC power and to provide LED lighting devices which have an improved power factor and a reduced total harmonic distortion when powered with AC power.
1. An LED lighting device comprising:
at least one LED circuit having at least two LEDs connected in series;
a first active current limiting device connected in parallel with at least one LED in the at least one LED circuit to bypass the at least one LED connected in parallel with the first active current limiting device until a voltage threshold is reached, the first active current limiting device setting an upper limit on the amount of current flowing through any LEDs in the LED circuit the first active current limiting device is not connected in parallel with.
2. The LED lighting device of claim 1 further comprising at least a second active current limiting device, the second active current limiting device being connected in series with the at least one LED circuit.
3. The LED lighting device of claim 2 further comprising a bridge rectifier, the second active current limiting device connected in series with the at least one LED circuit being connected across the output of the bridge rectifier.
4. The LED lighting device of claim 3 wherein the bridge rectifier is constructed using LEDs.
5. The LED lighting device of claim 2 further comprising at least one additional LED circuit having at least two LEDs connected in series and at least one additional active current limiting device connected in parallel with at least one of the at least two LEDs in the at least one additional LED circuit, the at least one additional LED circuit being connected to the at least one LED circuit in parallel.
6. The LED lighting device of claim 5 wherein the at least one LED circuit is capable of emitting light having one or more of a different color or wavelength than the at least one additional LED circuit.
7. The LED lighting device of claim 5 wherein the at least one LED circuit has different forward operating voltage than the at least one additional LED circuit.
8. The LED lighting device of any one of claim 1 further comprising a resistor, the resistor being connected in series with the at least one LED circuit.
9. The LED lighting device of any one of claim 1 wherein the at least one active current limiting device is a constant current regulator.
10. The LED lighting device of any one of claim 1 wherein the at least one active current limiting device is a current limiting diode.
11. A method of reducing harmonic distortion in LED lighting circuits and devices, the method comprising the steps of:
connecting at least two LEDs in series;
providing a bypass around at least one of the at least two LEDs connected in series, the bypass being an active current limiting device; and,
maintaining a substantially constant current flowing through at least one LED which is not bypassed while the at least one of the at least two LEDs is bypassed by the active current limiting device.
12. The method of claim 11 further comprising the step of connecting a second active current limiting device in series with the at least two LEDs.
13. The method of claim 12 further comprising the step of rectifying the voltage provided to the at least two LEDs using a bridge rectifier.
14. An LED lighting device comprising:
at least two LED circuits connected in parallel, each of the at least two LED circuits having at least one LED, each LED circuit emitting light having one or more of a different color or wavelength than other LED circuits;
a first active current limiting device being connected in series with one of the at least two LED circuits;
a bridge rectifier, the bridge rectifier providing rectified AC voltage to each of the at least two LED circuits connected in parallel.
15. The LED lighting device of claim 14 wherein the first active current limiting device is a current limiting diode.
16. The LED lighting device of claim 14 wherein the first active current limiting device is a constant current regulator.
17. The LED lighting device of claim 14 further comprising a second active current limiting device, the second active current limiting device being connected in series with a different LED circuit than the LED circuit connected in series with the first active current limiting device.
18. The LED lighting device of claim 14 wherein the LED circuit connected in series with the first active current limiting device has at least two LEDs connected in series, and a second active current limiting device is connected in parallel with at least one of the at least two LEDs connected in series.
19. An LED lighting device comprising:
at least one LED circuit having at least two LEDs connected in series;
at least one LED of the at least two LEDs emitting light of a different color or wavelength than the other LEDs connected in series;
at least one active current limiting device, the active current limiting device being connected in parallel with at least one LED in the at least one LED circuit;
at least a second active current limiting device, the second active current limiting device being connected in series with the at least two LEDs,
wherein the LED lighting device is capable of emitting light during both a positive and negative phase of a provided AC voltage.
20. The LED lighting device of claim 19 further comprising a bridge rectifier, the bridge rectifier being connected in series with the at least one LED circuit in order to provide rectified AC voltage to the at least one LED circuit.