Spectral shift control for dimmable ac led lighting

A method of conditioning current in a light engine steps comprising:

• providing a pair of input terminals that 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 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 increasing in a range above a threshold current value;
• and
• diverting the current from the first network with dimming conditioning circuitry as a function of the waveform of the periodic excitation voltage.