H. Koizumi, H. Sekiya, M. Matsuo
IEEE Transactions on Circuits and Systems I-regular Papers
The class DE inverter offers high-efficiency power conversion under high operating frequency (megahertz order) with low switching noises and low switch voltage stress. It has been applied to DC/DC converters as high-density power sources. Conventional converters with the class DE inverter are controlled by varying the operating frequency, the switch duty ratio or the phase difference with two inverters. However, in general, frequency-modulated control requires a complex control unit. Changing the switching duty ratio puts the switch-voltage waveforms out of shape, and the phase shift control needs the double space of inverters, which is not suitable for the low output power circuit. As a remedy to these problems, we propose to combine the class DE inverter with the class E rectifier using the thinned-out method (deleting some of the pulses to the rectifier). The DC/DC converter's output power is controlled in the rectifier by eliminating its diode-voltage pulse at a desirable rate. The operating frequency is fixed and the waveforms keep the characteristics of class DE. An experimental circuit was designed at 1 MHz operating frequency and in the optimum operation, the measured DC/DC power conversion efficiency was over 80% with 2.2 W output power at 1 MHz. Characteristics of the converter for the line and load variations are given by circuit experiments. It is shown that the proposed circuit has good characteristics with high power conversion efficiency in a wide range of these variations.