Multi-Level Switched-Capacitor Rectification and DC-DC Conversion

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MULTI-STEP, SWITCHED-CAPACITOR RECTIFIER AND DC-DC CONVERTER CIRCUITS AND RELATED TECHNIQUES
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Inventors
Professor David Perreault
Department of Electrical Engineering and Computer Science, MIT
External Link (www.rle.mit.edu)
Wei Li
Department of Electrical Engineering and Computer Science, MIT
Nathaniel Salazar
Department of Electrical Engineering and Computer Science, MIT
Managed By
Christopher Noble
MIT Technology Licensing Officer - Clean and Renewable Energy
Patent Protection

Apparatus for Multi-level Switched-Capacitor Rectification and dc-dc Conversion

US Patent 9,450,506
Publications
Integrated Low-Voltage Converter Architecture with AC power Delivery
2012 IEEE Energy Conversion Congress and Exposition, pp. 4584-4591, Sept. 2012

Applications

Capacitor rectification and DC-DC conversion is integral for the power supplies of applications including portable electronic devices, digital electronics, sensors, and communication circuits.

Problem Addressed

A conventional buck converter has no transformation stage, so the inverting and rectifying devices each see both high current and high voltage, making this approach unattractive for high-conversion-ratio on-die dc-dc converters. Topologies with a transformation stage (e.g. coupled-inductor buck, flyback, etc.) can operate using only low-voltage rectifier devices. However, they require coupled magnetics (or transformers) which are not readily realized on die. Moreover, the inverter devices must be both fast and high voltage, which are unavailable in current processes. The proposed apparatus is a voltage-step down rectifier topology suitable for integration on-die in CMOS. When coupled with an inverter and transformation stage, the rectifier provides a dc-dc converter having a voltage cov

Technology

The invention is a CMOS compatible voltage step-down rectifier capable of both DC-DC power conversion and AC power delivery to low-voltage electronics. The switched-capacitor rectifier consists of several stages; only the devices in the last stage must be controlled.  Since the devices in other stages of the multi-level switched-capacitor rectifier are either self-driven or driven by a DC voltage, the driving scheme is simplified. When coupled with an inductive source, the invention achieves very low-loss rectification for ease of power delivery in computation systems. Combined with inversion and transformation, the invention yields a DC-DC converter with a step-down conversion ratio of  π/4N, where input voltage is NV­.

Advantages

  • Allows high-voltage and low-current power distribution
  • Uses low-voltage CMOS rectifiers on die for fast switching speeds
  • Allows use of off-die inverter, where size and loss are less important than cost
  • Increases step-down transformation in the rectification stage for better performance