LED lamps becomemore and more economically attractive in the lighting market, primarily thanks to their great energy saving, long lifetime and ever decreasing cost compared with the conventional lighting solutions, such as incandescent or fluorescent ones. A traditional fluorescent lighting system consists of a fluorescent lamp(s) and a magnetic/electronic ballast. A direct replacement of a fluorescent lamp by a LED lamp with the same formfactor and pin connection avoids any rewiring or removal of the ballast, which is known as the retrofit concept. The retrofit LED lamps further guarantee a minimal total cost of ownership.
This work investigates the compatibility issues between the T5 Retrofit LED lamps and the legacy electronic ballasts. The compatibility design focuses on the following points: 1. The LED lamps should generate stable light output at the specified lumen level; 2. The lifetime and reliability of the LED lamps and ballasts fulfill the given specifications; 3. The driver design should fit into the T5
tubes.
Two methods to ensure the compatibility have been studied, a passivemethod and an active method. The passive method utilizes inductance and capacitance to increase the load impedance seen by the ballasts so as to reduce the ballast output current and control the ballast thermal issues. Four structures with inductance and capacitance haven been analyzed by means of mathematical analysis and simulations. The active method realizes the LED current control that is absent in the passive method. Efforts are conducted to reduce the size of the two proposed active circuits. After the simulation analysis of each designs, a demonstration board has been built for experimental verification.
Combining the passive methods with the active ones, four possible solutions that satisfy the design requirements are found. The comparisons between these solutions and the design suggestions are given in the last chapter.