In general, LED drivers with a passive current balancing function are cheaper and smaller than active current balancing drivers thanks to the lack of current sensors and control circuits. Conventional passive current balancing drivers, however, tend to suffer from its poor extendibility because a multi-winding transformer is required for the extension of the LED strings. Although capacitive current balancing LED drivers with no multi-winding transformer achieve high extendibility, numerous capacitors are necessary for extension process. In this paper, a highly-extendable capacitive current balancing multi-channel LED driver is proposed. Not only can the number of LED strings be arbitrarily extended by adding capacitors and diodes, but also the capacitor count can be reduced compared to the conventional capacitive current balancing LED drivers. The operation analysis and current balancing mechanism are discussed in detail. The experimental verification using a prototype for eight LED strings demonstrated the efficacy of the proposed LED driver.
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