12.4 A 7.5W-output-power 96%-efficiency capacitor-free single-inductor 4-channel all-digital integrated DC-DC LED driver in a 0.18μm technology

Today´s general lighting development is driven by improvements in semiconductor-based systems. It is expected that solid-state lighting (SSL) will dominate general lighting in the near future. Two main challenges that must be met in SSL are the reduction of the bill of materials (BOM), and an increase in functionality. In [1], a floating DC-DC buck controller is presented. This controller adds to the BOM, as every device of the power path is discrete and the ASIC can only drive a single LED string. In contrast to that, [2] offers a high-current fully integrated power stage. However, several external passives are introduced and the technology inhibits stacking multiple LEDs for high luminous efficacy. To overcome this, [3] presents an integrated HV power path with only the inductor as an external component. Ina parallel development, [4] reports an LED driver similar to [3], but that uses a discrete Schottky diode for asynchronous rectification. In fact, [1-4] demonstrate single output LED drivers without additional functionality or full color spectrum. To overcome these drawbacks in light spectrum and control, [5] presents a 3-channel LED driver. However, the external passives are numerous, which significantly impairs the overall BOM.