Technologies Related to Variable-Load Voltage Converters and Their Control Schemes

Abstract

Researchers at the University of California, Davis have developed voltage converters systems – with associated control schemes – that span a broad spectrum of potential applications.

Full Description

Switched-capacitor power converters are non-linear circuits that can transition quickly to another circuit configuration under certain conditions. For overall system efficiency reasons, switched-capacity power converters have not been used historically as part of high-density power solutions. More recently, switched-capacitor-inductor (LC) converters have demonstrated improved performance at high conversion ratios and found some appropriate applications in this space. Split-phase Dickson converters have been introduced in the literature which are efficient under heavy loads but which suffer increased component voltage stress with increasing conversion ratio [1],[2]. Additionally, like most conventional DC-DC converters, split-phase converters suffer reduced efficiency at light load due to maximized switch utilization.

Researchers at the University of California, Davis have developed a converter which leverages three key innovations to yield an improved solution:

First, this technology applies split-phase switching to a Cockcroft-Walton ladder variant; dramatically reducing voltage stress and allowing for a significantly smaller solution size.

Second, a new highly efficient clocking scheme, termed “N-Phase” switching, was developed for the exact same hardware and which offers improved light-load efficiency relative to split-phase switching due to its reduced switch utilization [3].

Lastly, this technology allows for optimal merging of switching between N-phase and split-phase control yielding the advantages of both. The control system automatically selects the most appropriate switching scheme based on the operating point and associated power load.

Since both N-phase and split-phase converters employ identical hardware, a control method that selects the optimal conversion technique for any operational environment provides the highest energy efficiency across a wide and variable load range. This technology thus has applications in mobile devices, aviation, biomedical markets and power distribution. 

Applications

•         Efficient and high-energy voltage conversion/control across diverse power requirement ranges

Features/Benefits

•         Voltage stress is reduced on most converter components
•         Allows for physically smaller capacitors that exhibit the same effective capacitance
•         Higher efficiency across entire load range
•         Suitable for large conversion ratios

Patent Status

Additional Patent Pending

Related Materials

• Y. Lei, R. May, and R.C.N. Pilawa-Podgurski. "Split-phase control: Achieving complete soft-charging operation of a Dickson switched capacitor converter." IEEE Transactions on Power Electronics 31, no. 1 (2015): 770-782. - 10/28/2019
• Seo, Gab-Su, Ratul Das, and Hanh-Phuc Le. "A 95%-Efficient 48V-to-1V/10A VRM Hybrid Converter Using Interleaved Dual Inductors." In 2018 IEEE Energy Conversion Congress and Exposition (ECCE), pp. 3825-3830. IEEE, 2018. - 10/28/2019
• N.M. Ellis, and R. Amirtharajah. “A Resonant Cockcroft-Walton Switched-Capacitor Converter Achieving Full ZCS and >10kW/inch3 Power Density” In 2019 IEEE Energy Conversion Congress and Exposition (ECCE)