Reduction of Harmonic Distortion for LED Loads
First Claim
1. A method of conditioning current in a light engine, the method comprising:
- providing a pair of input terminals adapted to receive a periodic excitation voltage;
receiving a current of equal magnitude and opposite polarity into each one of the pair of terminals, said current flowing in response to the excitation voltage;
providing a plurality of light emitting diodes (LEDs) arranged in a first network, said first network arranged to conduct said current in response to the excitation voltage exceeding at least a forward threshold voltage associated with the first network;
providing a plurality of LEDs arranged in a second network in series relationship with said first network;
providing a bypass path in parallel with said second network and in series relationship with said first 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 increasing in a range above a threshold current value;
permitting said current to flow through said first network and substantially diverting said current away from said second network while a voltage drop across the bypass path is substantially below a forward threshold voltage associated with the second network; and
,smoothly and continuously transitioning substantially all of said current from said bypass path to said second network in response to said current increasing in a substantially smooth and continuous manner while the voltage drop across the bypass path exceeds a forward threshold voltage associated with the second network.
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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.
61 Citations
19 Claims
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1. A method of conditioning current in a light engine, the method comprising:
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providing a pair of input terminals adapted to receive a periodic excitation voltage; receiving a current of equal magnitude and opposite polarity into each one of the pair of terminals, said current flowing in response to the excitation voltage; providing a plurality of light emitting diodes (LEDs) arranged in a first network, said first network arranged to conduct said current in response to the excitation voltage exceeding at least a forward threshold voltage associated with the first network; providing a plurality of LEDs arranged in a second network in series relationship with said first network; providing a bypass path in parallel with said second network and in series relationship with said first 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 increasing in a range above a threshold current value; permitting said current to flow through said first network and substantially diverting said current away from said second network while a voltage drop across the bypass path is substantially below a forward threshold voltage associated with the second network; and
,smoothly and continuously transitioning substantially all of said current from said bypass path to said second network in response to said current increasing in a substantially smooth and continuous manner while the voltage drop across the bypass path exceeds a forward threshold voltage associated with the second network. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
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14. A light engine comprising:
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a pair of input terminals adapted to receive a periodic excitation voltage and receive a current of equal magnitude and opposite polarity into each one of the pair of terminals, said current flowing in response to the excitation voltage; a plurality of light emitting diodes (LEDs) arranged in a first network, said first network arranged to conduct said current in response to the excitation voltage exceeding at least a forward threshold voltage associated with the first network; a plurality of LEDs arranged in a second network in series relationship with said first network; a bypass path in parallel with said second network and in series relationship with said first network; a controllable impedance element in the bypass path; and
,a dynamic impedance control module coupled to the controllable impedance element, said dynamic impedance control module adapted to dynamically operate the controllable impedance element to increase an impedance of the bypass path as a substantially smooth and continuous function of said current amplitude in response to said current amplitude increasing above a threshold current value, and to permit said current to flow through said first network and to divert substantially all of said current away from said second network while a voltage drop across the bypass path is less than a forward threshold voltage associated with the second network, and smoothly and continuously transitioning substantially all of said current from said bypass path to said second network as said current increases in a substantially smooth and continuous manner while the voltage drop across the bypass path exceeds a forward threshold voltage associated with the second network. - View Dependent Claims (15, 16, 17, 18, 19)
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Specification