ARCHITECTURE FOR HIGH POWER FACTOR AND LOW HARMONIC DISTORTION LED LIGHTING
First Claim
1. A method of electrically exciting a light engine, the method comprising:
- processing a periodic waveform of alternating polarity to form an input excitation signal with a voltage amplitude reduced to substantially zero for a selected phase angle;
providing a network of light emitting diodes (LEDs) comprising a first group of LEDs arranged in series connection with a second group of LEDs;
applying the input excitation signal to the network of LEDs;
diverting current away from the second group of LEDs in response to the input excitation signal voltage less than an effective forward voltage of the network of LEDs;
modulating the selected phase angle within a range of phase angles below a threshold phase angle to produce a corresponding modulation in a luminance of the first group of LEDs; and
,maintaining a substantially constant luminance of the second group of LEDs while modulating the selected phase angle within the range of phase angles below the threshold phase angle.
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Accused Products
Abstract
Exemplary apparatus and associated methods involve a bypass module for modulating conductivity of one or more current paths to provide a first set of LEDs that are conducting near minimum output illumination and having a larger conduction angle than that of a second set of LEDs that conduct at a maximum output illumination. In an illustrative example, the conductivity of a bypass path in parallel with a portion of the second set of LEDs may be reduced while the AC input excitation is above a predetermined threshold voltage or current. The bypass path may be operated to provide a reduced effective turn-on voltage while the input excitation is below the predetermined threshold. For a given maximum output illumination at a maximum input excitation, the bypass module may control current through selected LEDs to construct an input current waveform with substantially improved power factor and reduced harmonic distortion.
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Citations
20 Claims
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1. A method of electrically exciting a light engine, the method comprising:
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processing a periodic waveform of alternating polarity to form an input excitation signal with a voltage amplitude reduced to substantially zero for a selected phase angle; providing a network of light emitting diodes (LEDs) comprising a first group of LEDs arranged in series connection with a second group of LEDs; applying the input excitation signal to the network of LEDs; diverting current away from the second group of LEDs in response to the input excitation signal voltage less than an effective forward voltage of the network of LEDs; modulating the selected phase angle within a range of phase angles below a threshold phase angle to produce a corresponding modulation in a luminance of the first group of LEDs; and
,maintaining a substantially constant luminance of the second group of LEDs while modulating the selected phase angle within the range of phase angles below the threshold phase angle. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. An illumination system comprising:
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a phase control input port to receive an input control signal; a phase-cut module coupled to the phase control input port and configured to process a periodic waveform of alternating polarity to form an input excitation signal with a voltage amplitude reduced to substantially zero for a phase angle selected in response to the input control signal; a rectifier for converting the input excitation signal to a unipolar voltage signal; a network of light emitting diodes (LEDs) coupled to receive the input excitation signal from the rectifier, the network of LEDs comprising a first group of LEDs arranged in series connection with a second group of LEDs; a bypass module to divert current away from the second group of LEDs in response to the input excitation signal voltage greater than an effective forward voltage of the first group of LEDs and less than an effective forward voltage of the network of LEDs; wherein a luminance of the first group of LEDs modulates in substantial correspondence with the input control signal modulating the selected phase angle within a range of phase angles below a threshold phase angle, and the second group of LEDs maintains a substantially constant luminance while modulating the selected phase angle within the range of phase angles below the threshold phase angle. - View Dependent Claims (17, 18, 19, 20)
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Specification