Reduction of harmonic distortion for LED loads

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;
• substantially smoothly and continuously reducing current flow through the bypass path in response to a substantially smooth and continuous increase in a voltage drop across the bypass path in a range above a forward threshold voltage associated with the second network;
• rectifying the excitation voltage to form a substantially unipolar excitation voltage to drive said current;
• modulating the excitation voltage;
• wherein modulating the excitation voltage comprises receiving a control signal and, in response to information contained in the control signal, applying the excitation voltage waveform that corresponds to the information in the control signal;
• wherein applying the excitation voltage to the input terminals only during a portion of the period of the excitation voltage waveform that corresponds to the information contained in the control signal comprises delaying application of the excitation voltage to the input terminals during at least one of the periods, wherein a length of the delay is responsive to the information contained in the control signal;
• wherein the light engine operates with a power factor above 90%.