An LED lamp driver having its input compatible with different supply sources to drive an LED array is proposed. The driver can be powered by the ac mains, low-frequency electromagnetic ballasts, and high-frequency electronic ballasts. Its input impedance is controlled to meet the operational requirements and conditions of different sources and its output is controlled to deliver the required power to the LED array. The concept of this universal compatibility allows replacement of fluorescent lamps with the proposed retrofit LED lamps without removal or replacement of existing ballasts or modification of the lighting infrastructure. A 20W retrofit LED lamp prototype has been built.
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