Study of the Asymmetrical Half-Bridge Flyback Converter as an Effective Line-Fed Solid-State Lamp Driver

This paper illustrates the design and an experimental test of a line-fed solid-state lamp driver based on the asymmetrical half-bridge flyback converter. Its favorable characteristics, in terms of soft-switching range and circuit complexity, allow the converter to operate at variable switching frequency in the range of 300-450 kHz, supplying 6 W to the load with good efficiency. The considered lamp is made up of five series-connected high-power light-emitting diodes (Cree XR-E) and is supplied with 350-mA closed-loop-regulated constant current. While presenting similar complexity and overall efficiency with respect to a conventional driver, due to an original feedforward control technique that allows shrinking the input filter capacitor, the proposed circuit allows a significant volume reduction and consequent power density improvement.