The digitally controlled dc-dc converter has the advantage of high reliability, high controllability and high flexibility. A new digital controller for the PWM and/or PFM controlled switching dc-dc converters is presented, which is versatile in general use such as the switching frequency from 20 kHz to 70 kHz, the hard-switching and soft-switching and so forth. As an example, we apply this controller to half-bridge type series resonant dc-dc converter with auxiliary switches, in which both PWM and PFM control modes are employed, and the output characteristics of the converter are discussed. As a result, the relationships among circuit parameters of the proposed digital controller, switching frequency of the dc-dc converter, oscillation frequency of the VCO as analog to digital signal converter are defined.

The control of class DE amplifier is an important problem since its switching operations do not satisfy class E switching conditions when the load resistance varies from the initial designed values. Therefore, several of control schemes of class DE amplifier were proposed. However, the changes of the output voltage and the power conversion efficiency by using these controls can be measured only experimentally and thus, they cannot be found theoretically. In this paper, an exact analysis of class DE amplifier with FM and PWM control schemes is presented. From the analysis, we can theoretically derive the output voltage, the power conversion efficiency and so on. Moreover, the frequency and the duty ratio to keep the constant output voltage can be found when the load resistance or the input voltage varies. We indicate that the theoretical predictions are similar to the experimental results quantitatively. The measured efficiency is over 94% with 1.0 MHz and 1.8 W output.