Enhancing the efficiency in the light-emitting-diode (LED) drivers is a noteworthy issue as it not only helps saving energy but also causes the long life span of the drivers. In this paper, a new LED driver with improved efficiency is proposed. Efficiency improvement is achieved without using any active or passive component to perform soft switching conditions. In the proposed driver, buck and buck-boost converters are integrated. The freewheeling diodes and inductors - of the two converters - are replaced by one diode and one inductor. So, the proposed driver constitutes a single-stage driver with a simple structure that uses only one controlled switch, one freewheeling diode, and one inductor. Besides its simple structure, the driver works with a constant frequency, which leads to using a simple controller. Efficiency improvement is obtained by changing the inductor size and LEDs arrangement rather than using the active clamp or snubber circuits. To decrease the switching losses in the proposed driver, the average of the input current is kept constant while the peak of the pulsating input current - which passes from the switch and freewheeling diode - is decreased. Moreover, power losses of the semiconductor components in the proposed driver are investigated, and consequently decreased, leading to improvement in the system's overall efficiency. Finally, a 10 W experimental driver is built and tested. The experimental results are consistent with theoretical analysis.
Key words: Buck converter; High-efficient LED driver; Single stage driver; Integrated converters; Power losses.
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