An optimization approach for high-efficiency high-power-density boost converters

Abstract

Boost converters running in valley switching mode have the advantages of low switching loss and small inductor size. However, the switching frequency is not fixed as operating conditions vary, which can make inductor design for this converter challenging. In this paper, a systematic optimization approach is presented that is suitable for wide-input-voltage range designs such as power factor correction (PFC) converters. The loss of each component is modeled as a function of the operating point, and the efficiency is estimated over the entire input voltage range. Given a set of selected cores and Litz wire, an optimal inductor design can be found on a plot of efficiencies and air-gap lengths. Genetic algorithms can be used to find the optimal design with customizable cores. Experiments are conducted to verify the model and the approach. One of the prototypes, designed as the first stage for an ac-dc converter system, achieves around 98% efficiency over the input range of 70V to 170V, boosting to 363V at 45W. The prototype converter has a total volume of 2.8cm 3 and reaches a power density of 263W/in 3 .

A Two-Stage Universal Input Charger With Wide Output Voltage Range

“…4. The converter is topologically simple, requiring only one low-side switch, and a recently proposed optimization approach offers a means to achieve high efficiencies in volume-constrained designs operating at MHz frequencies [17]. An overview of the operation of this converter is provided in Appendix A.…”

“…The front-end boost converter is optimized according to the approach detailed in [17]. The resulting converter operates between 0.5-2MHz and the prototype parameters are listed in Table IV. A valuable degree of freedom enabled by the boost frontend is the ability to shape the line current.…”

“…This paper focuses on the trade-offs and potential of the proposed two-stage architecture and uses conversion stages which have been explored in detail in the literature [5], [17], [24]. For convenience, this appendix provides an overview of the operation of the front-and back-end stages.…”

“…2. The miniaturization potential of this active buffer is enabled by the availability of high energy density high-voltage ceramic capacitors [16] and a recently proposed optimization approach for the valley-switched boost converter [17] which takes advantage of the performance benefits of high frequency operation enabled by Gallium Nitride (GaN) devices and modern magnetic materials.…”

“…We emphasize that although the VIRT stacked-bridge LLC converter [5] and valley-switched boost converter [17] represent topologies that have been defined in the literature, this study is distinct in its exploration of the net miniaturization benefit that is achievable when using these converters in a twostage charger. Section II elucidates the design considerations involved in selecting the minimum and maximum bus voltage value, and Section III explores the trade-off between an active buffer and a passive buffer.…”