2-Stage LED Driver With Multi-Channel Constant Current CLL Resonant Converter
A 2-stage LED driver is proposed, which is composed by a Buck converter and a multi-channel constant current CLL resonant converter. The CLL resonant converter is unregulated and is always working at the optimal point to achieve the best efficiency. The current of one specific LED string is sensed for feedback control to tune the duty cycle of Buck converter. The currents of other strings are cross-regulated. This invention is very suitable for multi-channel constant current LED driving, especially because there are differences among the LED numbers for each string. When the loads are unbalanced, the current sharing capability between the LED strings is very good. Meanwhile, ZVS of the primary side switches can be guaranteed even under unbalanced loads condition. Therefore, higher efficiency can be obtained with wide load range.
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