Single-switch three-level boost converter for PWM dimming LED lighting

In this paper, a novel single-switch three-level (TL) boost converter for PWM dimming LED lighting is presented. Taking the system efficiency and output ripple into consideration, traditional two-level boost LED driver always employs additional active switch in order to deal with the dimming issue. However, the proposed TL boost converter has overcome the dimming control problem with only one switch by utilizing the “synchronous” PWM dimming approach, hence lower the system cost. Moreover, compared with the standard TL boost converter, the proposed topology not only maintains the advantage of using a lower voltage rating power switch that is rated half the output voltage, but also eliminates one active switch and its associated driving circuit. The operating principle and dimming scheme of the proposed TL boost converter is described in detail. A prototype of 11-W dimmable LED driving converter has been implemented to verify the design and analysis. The experimental result shows that single-switch TL boost converter can regulate the LED current from zero to the rated 350 mA with fast slew rate. A peak efficiency of 95% was achieved with 400kHz switching frequency.