This study focused on three simplified models, namely (1) one set of single-phase DC-DC converter, (2) two sets of parallel connection single-phase DC-DC converter, and (3) two sets of series connection single-phase DC-DC converter. The purposes are: (1) to propose the simplification conditions and procedures for the three-phase AC-DC converter; (2) propose a set of new simplification steps for modeling, and present the examples of different three-phase AC-DC circuit topologies, detailed discussion on the simplification steps for modeling of a three-phase AC-DC converter is offered, to help people simplify and analyze the simplified model easily; (3) according to three types of simplified modeling in the three-phase AC-DC converter, this study established a useful reference for the design and analysis of the control systems of the three-phase AC-DC converter simply; (4) to acquire PWM control strategy beforehand based on PFC-Controlled property; (5) to reduce the switching loss for the PWM control strategy of the simplified model; (6) to maintain the original circuit topology and verify that the theory can extensively apply the knowledge of single-phase DC-DC converter to the simplified modeling of three-phase AC-DC converter.

This paper proposes spread-spectrum clock modulation algorithms for EMI reduction in digitally-controlled DC-DC converters. In switching regulators using PWM, switching noise and harmonic noise concentrated in a narrow spectrum around the switching frequency can cause severe EMI. Spread-spectrum clock modulation can be used to minimize EMI. In conventional switching regulators using analog control it is very difficult to realize complex spread-spectrum clocking, however this paper shows that it is relatively easy to implement spread-spectrum EMI-reduction using digital control. The proposed algorithm was verified using a power converter simulator (SCAT).

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.

A piezoelectric transformer (PT) converter with PWM control is presented. The combination of an active-clamp circuit and a resonant circuit makes it possible to control the output voltage of the PT converter with PWM at a constant switching frequency. The PT converter circuit is evaluated using an AC analysis, and a design procedure is presented. The PT converter implemented on a printed circuit board is experimentally evaluated and a good controllability is successfully achieved.