Generalized State-Plane Analysis of Soft-switching DC-DC Converters
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I nb : The normalized cell-current entering node
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0-7803-7448-7/02/$17.00 ©2002 IEEE
Generalized State-Plane Analysis of Soft-switching DC-DC Converters Abdelhalim Alsharqawi and Issa Batarseh*
School of Electrical Engineering and Computer Science University of Central Florida Orlando, FL 32826
Tel. (407) 823-0185 Fax (407) 823-6334 Email: batarseh@
ABSTRACT-Based on Generalized switching-cell approach, a generalized state-plane analysis for families of soft-switching dc-to-dc converters will be presented. It is shown the analysis of soft-switching dc-to-dc converter families can be analyzed in terms of simple two-dimensional state-plane diagram. Complete generalized design equations will also be given. It will be shown that one generalized transformation table will be given for the analyzed families. The basic generalized equations will be summarized . The concept of generalized state-plane analysis will be applied to selected soft-switching families such as ZVS-QRC, ZCS-QRC, QSW-CC, QSW-CV, ZCT-PWM, and ZVT-PWM. Other switching families can also be analyzed using the state-plane method. 1. Introduction Research in soft-switching dc-dc converters continue to generate numerous new softswitching families operating at higher and higher switching frequencies. The advantages of high frequency include smaller size and lighter weight of magnetic components. Over the last ten years, several soft-switching dc-dc families where analysis thoroughly in the open literature [4,5,6,7]. Moreover, the analysis of softswitching converters is normally accomplished by identifying the circuit modes of the converter during a switching cycle along with the boundary conditions associated with the transitions between these modes. This is a time consuming process for obtaining a steady state solution. A more simplified technique is to use the state-plane diagram where the state variables in each mode are sketched on a two-dimensional state-plane diagram. In this paper, it will be shown that the steady-state analyses of the soft switching dc-dc converters can be generalized for a given switching networks family. As a result, instead of analyzing each converter topology in a given family separately, only one switching network for each family is needed to be analyzed [1]. Once the state-plane diagram is obtained, the steady state solution in the time domain can be found easily. Moreover, the stateplan analysis method gives more insight into the converter cell operation [2,3]. Furthermore, it will be shown by using the desired converter parameters, the control characteristics of soft-switching converters can be derived from the state-plane diagram. In particular, the converter design gain as function of frequency and load value can be determined. Finally, the component’s peak values can be also obtained directly from such diagram. In Section 2, generalized switching cells are derived for selected dc-dc soft-switching PWM families including the conventional hardswitching PWM topologies. The generalized cells were derived for the following well-known soft-switching families: 1) Zero- VoltageSwitching (ZVS) and Zero-Current-Switching (ZCS) – Quasi-Resonant Converter (QRC) families [4], 2) ZVS-Clamped Voltage (CV) Quasi-Square-Wave (QSW) family [5,6], 3) ZCS-Clamped-Current (CC) QSW family [7], and 4) Zero-Voltage-Transition (ZVT) and ZeroCurrent-Transition (ZCT) PWM families [8,9]. 2. The Generalized Switching Cells and Their Corresponding State-Planes Figure (1) shows the six soft-switching cells for the above mentioned families, while Figure (2) shows the corresponding state-plane for the soft switching cells. Since each family uses the same switching network (same modes of operation) and the same state-plane, the analysis can be generalized. As mentioned in [1], steps can be used in the analysis generalization process. Various orientations of any of the cells in Figure (1) result in a family of converters. Using the three terminals a , b , and c in the switching-cells, generalized parameters can be defined and their values can be determined from the orientation of the cell in a specific converter. Let us define the following parameters: M : The overall output-to-input converter