In this paper, we present a practical comparison on a range of circuit topologies suitable for passive LED drivers. These circuits consist of passive components and do not require any semiconductor controlled switches, auxiliary power supply and control integrated circuits. The power loss components, the energy efficiency and the output current ripple are examined. These passive LED drivers are particularly suitable for outdoor applications such as street lighting in which extreme weather conditions including lightning and wide temperature range, and maintenance issues are major concerns but the size of the LED drivers is not critical. With extremely simple and reliable circuitry, these passive LED drivers achieve remarkably high energy efficiency. Energy efficiency of 92-94% has been achieved for LED systems of 50W in this study.

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