IEEJ Journal of Industry Applications
Online ISSN : 2187-1108
Print ISSN : 2187-1094
ISSN-L : 2187-1094
Paper
Analysis of Power Loss of Class E Amplifier with Nonlinear Shunt Capacitance
Tadashi SuetsuguXiuqin WeiMarian K. Kazimierczuk
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2014 年 3 巻 1 号 p. 68-74

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抄録

It is experimentally known that the efficiency of class E amplifiers deteriorates when the dc supply voltage is much lower than the designed value. However, the existing literature on efficiency and power loss analysis of class E amplifiers cannot explain the cause of this phenomenon at all. It is demonstrated in this paper that this deterioration of efficiency is caused by the influence of the nonlinearity of the output capacitance of the MOSFET. Owing to the nonlinearity of the output capacitance, the class E amplifier cannot achieve ZVS switching when dc supply voltage is lower than the designed value, even if the circuit is designed to achieve ZVS at the designed dc supply voltage. In this regard, this paper presents the power efficiency of the class E RF power amplifier as a function of dc supply voltage VDD when the shunt capacitance is nonlinear with the grading coefficient m =0.5 as a representative value. With this modeling of the nonlinear shunt capacitance, non-ZVS switching at a low dc supply voltage can be reproduced with the theoretical waveforms, and the switching loss can be calculated at a dc supply voltage that is lower than the designed dc supply voltage. Then, the total power loss including the switching loss can be calculated. The result of the efficiency calculation demonstrates a deterioration of efficiency at low dc supply voltages as expected, and there was good agreement with the experimental results.

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© 2014 The Institute of Electrical Engineers of Japan
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