Reduction of harmonic distortion for LED loads
First Claim
1. A system for a solid state light engine comprising:
- an AC input providing an input voltage that is modified by a dimmer module;
a rectifier receiving an applied electrical excitation from the dimmer module and supplying a unidirectional current to 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;
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;
a transistor that selectively diverts current away from at least one of the first and second networks of LEDs;
wherein the solid state engine is substantially and continuously dimmable.
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Accused Products
Abstract
Apparatus and associated methods reduce harmonic distortion of a excitation current by diverting the excitation current substantially away from a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level, and ceasing the current diversion while the excitation current or voltage is substantially above the predetermined threshold level. In an illustrative embodiment, a rectifier may receive an AC (e.g., sinusoidal) voltage and deliver unidirectional current to a string of series-connected LEDs. An effective turn-on threshold voltage of the diode string may be reduced by diverting current around at least one of the diodes in the string while the AC voltage is below a predetermined level. In various examples, selective current diversion within the LED string may extend the input current conduction angle and thereby substantially reduce harmonic distortion for AC LED lighting systems.
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Citations
16 Claims
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1. A system for a solid state light engine comprising:
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an AC input providing an input voltage that is modified by a dimmer module; a rectifier receiving an applied electrical excitation from the dimmer module and supplying a unidirectional current to 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; 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; a transistor that selectively diverts current away from at least one of the first and second networks of LEDs; wherein the solid state engine is substantially and continuously dimmable. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of dimming a solid state light engine step comprising:
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supplying an AC input voltage from an AC input; modifying the AC input voltage with a dimmer module to form an applied electrical excitation; supplying a current based on the applied electrical excitation to a plurality of light emitting diodes (LEDs) arranged in a first network; providing a plurality of LEDs arranged in a second network; providing a bypass path between the first network and the second network; dynamically increasing an impedance of the bypass path as a substantially smooth and continuous function of said current amplitude in response to said current amplitude changing in a range above a threshold current value; and dimming said solid state light engine with the dimmer module. - View Dependent Claims (9, 10, 11)
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12. A system for a solid state light engine comprising:
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an AC input providing an input voltage that is modified by a dimmer module to provide an applied electrical excitation; a plurality of light emitting diodes (LEDs) arranged in a first network that receives a load current based on the applied electrical excitation; wherein the solid state engine is substantially and continuously dimmable without use of a DC power source after the input voltage is modified by the dimmer module. - View Dependent Claims (13, 14, 15, 16)
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Specification