| Summary: | In this paper, the optimization of the power and control stages of a previously proposed topology for an off-line LED electronic driver is presented. The full system avoids the use of electrolytic capacitors at the <inline-formula> <math display="inline"> <semantics> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </semantics> </math> </inline-formula> link, therefore increasing the lifespan and reliability of the driver. As a consequence of having a relatively small capacitance, the <inline-formula> <math display="inline"> <semantics> <mrow> <mi>D</mi> <mi>C</mi> </mrow> </semantics> </math> </inline-formula> link operates with a large Low-Frequency (<inline-formula> <math display="inline"> <semantics> <mrow> <mi>L</mi> <mi>F</mi> </mrow> </semantics> </math> </inline-formula>) voltage ripple. This work presents a design optimization for the power and control stages of a current-fed bidirectional buck converter, operating as the LED current control stage. As this block processes only the <inline-formula> <math display="inline"> <semantics> <mrow> <mi>A</mi> <mi>C</mi> </mrow> </semantics> </math> </inline-formula> power arising from the <inline-formula> <math display="inline"> <semantics> <mrow> <mi>L</mi> <mi>F</mi> </mrow> </semantics> </math> </inline-formula> voltage ripple, it can increase the system efficiency against the typical two-stage solution. In the original proposal, the main drawback was the high inductor losses due to the resulting large inductor currents and large inductance value. The proposed optimization ensures an enhanced design of the inductor while keeping a constant current through the LEDs. A new optimization methodology is proposed and the theoretical results have been validated in a built prototype for a 40 W LED lamp.
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