Class E Power Amplifiers using High-Q Inductors for Loosely Coupled Wireless Power Transfer System

  • Yang, Jong-Ryul ;
  • Kim, Jinwook ;
  • Park, Young-Jin
  • Received : 2013.08.26
  • Accepted : 2013.11.06
  • Published : 2014.03.01


A highly efficient class E power amplifier is demonstrated for application to wireless power transfer system. The amplifier is designed with an L-type matching at the output for harmonic rejection and output matching. The power loss and the effect of each component in the amplifier with the matching circuit are analyzed with the current ratio transmitted to the output load. Inductors with a quality factor of more than 120 are used in a dc feed and the matching circuit to improve transmission efficiency. The single-ended amplifier with 20 V supply voltage shows 7.7 W output power and 90.8% power added efficiency at 6.78 MHz. The wireless power transfer (WPT) system with the amplifier shows 5.4 W transmitted power and 82.3% overall efficiency. The analysis and measurements show that high-Q inductors are required for the amplifier design to realize highly efficient WPT system.


Class E power amplifier;High efficiency;High quality-factor;L-type matching circuit;Loosely coupled wireless power transfer system


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