Alexander Bucher

Comparison of Different Design Methods for the Parallel Resonant Converter

For the voltage-fed parallel resonant converter several different approaches to investigate its steady-state characteristics exist. The exact solution yielded by state-plane analysis is compared to the approximate solution using ing fundamental components of the waveforms and to its extension regarding the first harmonic of discontinuous capacitor voltage waveforms. In addition, the accuracy in predicting important design criteria as well as the mathematical complexity of both methods is compared.

A comparison of different design methods for the multiresonant LLC converter with capacitive output filter

Faced with ever shorter product cycles, SMPS designers require fast and reliable modeling tools. In case of resonant converters the derivation of the exact solution is complex and time-consuming. Thus, simplified calculation methods are attractive. However, the reduced accuracy of these approximation methods has to be taken into account carefully. In this paper, the concepts of the First Harmonic Approximation (FHA) and the extended First Harmonic Approximation (eFHA) of the multiresonant LLC converter with capacitive output filter are discussed. Furthermore, the accuracy of both approximation methods is evaluated in detail with respect to the results of the exact solution in the time domain.

Multi-resonant LCC converter - comparison of different methods for the steady-state analysis

Several different approaches for the investigation of the steady-state properties of resonant converters have been published. In addition to solving the occurring equations in the time domain, which turns out to be quite cumbersome, the designer can make use of approximate approaches in the frequency domain. Two of these methods are compared to the exact solution with regard to their accuracy and mathematical complexity within this paper for the multi-resonant LCC converter with inductive output filter. Additionally, a minimized set of nonlinear equations is derived in case of the exact solution based upon the state-plane technique.

Consideration of conduction losses for the series resonant converter by means of a simple extension to the SPA approach

The cumbersome derivation of the steady-state characteristics of resonant converters can be simplified by means of the state-plane analysis. Under the assumption of ideal components, a closed-form solution can be derived in case of the series resonant converter above the resonant frequency. However, losses due to parasitic resistances cannot be easily included within this approach. Nevertheless, a more precise prediction of the converterpsilas output characteristics taking the conduction losses into account is desirable. Therefore this paper describes a simple extension to the regular approach that leads to better agreement with measurements. This approach is based on the results derived under ideal assumptions, thus avoiding a more complicated and tedious analysis including the conduction losses.

Comparison of methods for the analysis of the parallel resonant converter with capacitive output filter

Several different approaches for the investigation of the steady-state properties of resonant converters have been published to date. In addition to solving the occurring equations in the time domain, which turns out to be quite cumbersome, the designer can make use of approximate approaches in the frequency domain. Two of these methods are compared to the exact solution with regard to their accuracy and mathematical complexity within this paper for the parallel loaded resonant LC converter with capacitive output filter. Some practical aspects are discussed by means of measured voltage conversion ratios.

Characterization of a modified LISN for effective separated measurements of common mode and differential mode EMI noise

The compliance with standards calls for proper designed EMI filters. EMI typically comprises common mode (cm) and differential mode (dm) noise. A systematic optimization of EMI filters requires the knowledge of the contribution and distribution of these two noise sources. The paper discusses different methods that allow the independent measurement of cm and dm noise. One suitable method described in detail integrates the separation set-up into the Line Impedance Stabilization Network (LISN). However, a correct interpretation of the measured results requires a characterization of the unavoidable modal conversion of the complete set-up - i.e. the measured level at the dm output in case of pure cm excitation and vice versa. As shown in this paper, the implementation of a standard LISN introduces a high amount of imperfections causing the undesired modal conversion. Thus, for the first time, this paper describes the characterization of the whole set-up including the LISN.

Sampled-data modeling applied to output impedance reveals missing term in state-space averaging model

The investigation of the stability of larger power systems requires knowledge about output impedances of switch mode power supplies (SMPSs). Methods for the prediction of this quantity of a SMPS comprise state-space averaging and sampleddata modeling. However, results obtained from both methods exhibit large differences. Furthermore, sampled-data modeling itself yields completely different results for different sampling points. Negative as well as positive incremental impedances may occur. Nevertheless, considerations of the steady-state in time domain prove the existence of these strongly different results, as discussed in this paper. In addition to that, it will be shown that only small additional effort is necessary to simulate the converter behavior with exact averaged quantities. This leads directly to an improvement of the state-space average model by means of adding an operating point dependent resistor.

Calculation of Core Losses in Toroids with Rectangular Cross Section

In this paper the electric and magnetic field distribution is investigated in solid toroidal cores with rectangular cross section. An analytical method is used in which the field distribution is calculated by means of orthogonal expansion. Based on the results, the influence of various parameters, such as frequency and conductivity of the core material, on the core losses is discussed. The calculated results are compared with measured data, a good agreement between the two values is achieved.

Analysis and design of a contactless power transmission system based on the extended first harmonic approximation

For the task of transferring energy inductively, resonant converters are a suitable family of converters in order to overcome the technical hurdle of the loose magnetic coupling that is often encountered in this kind of application. However, the analysis of resonant converters is in general cumbersome. In order to facilitate the design process where a vast number of converter configurations has to be computed, approximations are required in order to bring the necessary computational time to maintainable levels. A design procedure for a contactless power transmission system based on the extended first harmonic approximation for the steady-state solution of the multi-resonant LLCC converter is presented in this paper, with a new degree of simplification regarding the resulting closed-form solution. By means of this approximation, the design of the fourth-order resonant LLCC converter is significantly simplified, providing a tool for rapid simulation combined with a very high accuracy. The resulting system was designed to be very tolerant against variations of the distance between the coils, at the same time achieving a very high efficiency for this kind of application.

Method for the fast and accurate simulation of switch-mode power supplies

In order to describe the voltage and current waveforms of a switch-mode power supply (SMPS) accurately by simulation the parasitic output capacitance of the MOSFET cannot be neglected. For this reason the paper describes and compares two different simulation methods which take this capacitance into account without extending the simulation time considerably, so that a fast and accurate transient simulation of the SMPS is obtained. The first method is an analytical solution with an equivalent linear capacitance. The second method really considers the non-linear dependency of the capacitance on the voltage. The measurement at the end shows, that the second method describes the SMPS very accurately. Furthermore a comparison with a calculation which neglects the parasitic capacitance shows the relevance of the proposed method.