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Power-electronics interface and the technique of pulsewidth modulation have been the heart of controlling the illumination intensity of lighting devices. It is, however, observed that for some lighting devices, the use of such a methodology leads to a lower energy-conversion efficiency (with a lower light intensity for the same amount of electrical input power) than potentially possible. The main problem is related to the saturable characteristic of the electrical-to-optical energy conversion, which follows that of an exponential characteristic, and the fast nature of this reaction in these lighting devices. This paper presents an in-depth discussion on the phenomenon and offers a solution to the problem. Specifically, it is proposed that an n -level type of driving approach to be adopted in the design and construction of power-electronic drivers for fast-response saturable lighting devices to achieve a quasi-optimal lighting efficacy. The result is energy saving for the same required light illumination. Theoretical proofs and experimental results are provided for verification. The topic of discussion in this paper and the proposed approach are not only applicable to the area of electronic circuits and lighting devices, but also to general controlled systems which comprise components that inherit a saturable and fast-reactive energy conversion characteristic.