**Author details**

For high current LED string the LLC converter with multiple-output secondary of the HF transformer can be considered [66]. In the secondary side as described in **Figure 20b** and **Figure 20c** a switching or linear type current regulator is added to

*Multi-channel LED driver circuits (a) block scheme of general AC LED driver system for multi-channel LED string. (b) Flyback converter solution with linear regulator on the secondary side. (c) Flyback converter solution*

*Light-Emitting Diodes and Photodetectors - Advances and Future Directions*

*Multi-channel LED driver circuits with single-inductor multiple-output solution.*

The LED driver circuits in several applications needs are investigated. The passive and active circuits are critically evaluated in terms of power request, topology simplicity, efficiency, reliability, and cost. The LED driver circuits are evaluated based on the different supply sources and power request. The DC-DC converters connected directly to a DC source such as battery are classified and pro and cons are

drive the LED strings.

**5. Conclusion**

**84**

**Figure 21.**

**Figure 20.**

*with switching type synchronous Buck current regulator.*

Salvatore Musumeci Department of Energy "G. Ferraris", Politecnico di Torino, Torino, Italy

\*Address all correspondence to: salvatore.musumeci@polito.it

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