A 3-Phase Resonant Switched Capacitor Converter Delivering 7.7 W at 85% Efficiency Using 1.1 nH PCB Trace Inductors

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Abstract
In recent years, there has been a push towards high-density and monolithic DC-DC converters to support applications such as performance and mobile computing, consumer electronics, and renewable energy. Switched capacitor (SC) converters have started to gain traction for a number of these applications, but are still subject to fundamental limitations that drive them towards expensive process options and high switching frequencies. Variable regulation is challenging with the SC approach, and comes at the cost of lower power density and efficiency. This work presents a resonant switched capacitor (ReSC) topology that addresses some of these challenges by introducing a small amount of inductance in series with the flying capacitor, eliminating charge-sharing losses and thus allowing efficient operation in a low-cost process option. The three-phase interleaved topology can deliver up to 7.7 W at 85% efficiency (power density of 0.91 W/mm 2 or 6.4 kW/in 3) using a bootstrapped n-channel power train and single-digit nH inductors embedded in a flip-chip assembly. We also present the first implementation of efficient, fully-variable conversion ratios in a silicon ReSC integrated circuit without reconfiguration or gain-hopping .

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