Resonant dc/dc converter with class E inverter and class E synchronous rectifier using thinned-out method

Class E switches have many advantages in comparison with PWM switches. Their low switching losses allow for high-efficiency operation at high frequency. They can operate with low electro-magnetic interference (EMI). In addition, class E synchronous rectifier has the advantage of low power dissipation in the devices. So it is effective especially in low power circuits. On the other hand, thinned-out method can regulate the output voltage easily by adding a simple logic circuit to the drive circuit. In this paper, we propose to apply the thinned-out method to a class E synchronous rectifier. The experimental circuit is Class E² resonant dc/dc converter composed of a basic class E inverter and a class E synchronous rectifier. The circuit can regulate the output voltage by controlling (thinning-out) the drive voltage waveforms of the MOSFET in the synchronous rectifier. Some experimental results are shown, and compared with other circuits. At low output power less than 0.4 W, it was maintained over 60 percent for varying the output voltage from 3.0 V to 2.1 V. The maximum measured efficiency is 78 percent