How Adaptive Cell Topology Benefits AC Applications

June 11, 2013
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With the wide variation in AC line voltages around the world, universal power supplies are typically designed to accept 85VRMS to 264VRMS inputs. This range has imposed significant design trade-offs on the power factor corrected AC rectification typically used in front end converters. The Vicor PFM isolated AC-DC converter with PFC, and the AC Front End Module both have Adaptive Cell™ topology at their heart, providing a breakthrough in AC front end power factor correction that addresses these trade-offs to provide a consistently efficient solution. It does so by introducing innovation at three different levels – Component, Cell and Brick.

At component level, it utilizes Double Clamp ZVS, while its Adaptive Cell converter architecture dynamically interconnects two such Double Clamp ZVS ‘Cells’ to meet prevailing line voltage levels.

Power factor correction control designs have traditionally been referenced to boost converter technology. Output voltage is regulated by varying the amplitude of the input current, which closely follows the shape of the line voltage. One of the main concerns is the rating of power semiconductors and magnetic components for worst case scenarios which never concurrently occur.

The first aspect of Vicor’s solution, the Double Clamp, Zero Voltage Switching Converter (DC-ZVS) comprises a full bridge primary and a single ended rectifier secondary. Using both the inductor and the capacitor CCL as ‘double clamp’ energy storage elements allows switching at either zero-voltage i.e. ‘Zero-voltage-switching’ This avoids switching losses and enables very high switching frequency. More importantly, it also allows switches with lower voltage ratings, resulting in isolated converters with power densities exceeding 700 W/in2 (43W/cm3).

To learn more, download the complete white paper, “The Adaptive Cell Converter Topology Enables Constant Efficiency Over Universal Input AC Line in Front-End, High Density Power Factor Correction Applications”.

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