To obtain sufficient luminance and achieve higher reliability, light-emitting diodes (LEDs) are usually arranged in parallel strings in many high-power applications. Since current imbalance should be avoided among the parallel LED strings, a multi-channel constant current LED driver based on high-frequency AC bus is proposed in this study. The proposed driver is composed of one resonant inverter followed by passive resonant rectifiers according to the number of LED strings. The amplitude of the high-frequency AC bus voltage is regulated by the resonant inverter and each LED string is individually powered with constant current by its corresponding passive resonant rectifier. The proposed driver is characterised by low cost and high efficiency. Finally, a prototype is built to verify the performance of the proposed driver.

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With the significant development in the manufacturing process of LEDs, LEDs are promising for various lighting applications. In order to achieve better performance and higher reliability, the multiple LED strings structure is adopted in many applications, such as street lighting and tunnel lighting. This paper is aimed to describe a multi-channel constant current LED driver which is composed of a master AC source and some slave passive constant current sources according to the number of LED strings.The high frequency resonant inverter is controlled to operate as the master AC source, whose output forms the high frequency AC bus, each LED string is individually powered by its corresponding salve passive constant current source driven by the high frequency AC bus.By employing the LED's u-i model instead of the constant resistive load, the performance and characteristics of the driver are analyzed in detail and the experimental results are provided to verify the concept.