Kanakasabai Viswanathan

A novel tri-state boost converter with fast dynamics

A challenging problem in the design of boost converters operating in continuous-conduction mode is posed by the dynamically shifting right-half-plane (RHP) zero in the converters small-signal control-to-output transfer function. The paper proposes a novel tri-state boost converter without such a zero in the transfer function. The additional degree of freedom introduced in the converter in the form of a freewheeling interval has been exploited through an easy control technique to achieve this elimination. The absence of the RHP zero allows the control scheme to achieve larger bandwidth under closed-loop conditions, resulting in fast response. Analytical, simulation and experimental results of the tri-state boost converter have been presented and compared with those of the classical boost converter both under open-loop and under closed-loop operating conditions. The results clearly demonstrate the superior dynamic performance of the proposed converter. The proposed converter can be used in applications wherever fast-response boost action is needed.

A Metric for Evaluating the EMI Spectra of Power Converters

The inherent switching of power devices in a switch mode power supply generates electromagnetic interference (EMI) noise. This noise is dependent on several factors such as component layout, circuit parasitics, and the control techniques implemented. Several methods have been reported in literature to mitigate the EMI problem. However, until now, a metric to characterize and compare the EMI spectra of power converters is not available in literature. This paper proposes a simple metric to measure and characterize the EMI spectrum of power converters. The proposed technique is based upon the specification and thereby the size of an external passive filter required to meet the given EMI standards. The proposed metric is useful in evaluating and comparing the severity of the EMI noise generated by different implementations of a power converter. Thus, it allows the designer to choose the better implementation option from an EMI noise perspective. The use of the proposed metric is demonstrated through the comparison of the quality of spectra of a power converter with two different switching schemes.

Design and analysis of SISO fuzzy logic controller for power electronic converters

Power converters are non-linear systems that usually employ linear controllers designed to offer good small signal performance at the nominal operating point. Yet, the converters large-signal response is generally poor. Fuzzy logic controllers (FLCs) used in such cases improve the response, but their small-signal response is not as good as that of linear controller. In this paper, design of a SISO-FLC that offers good small and large-signal performance in a boost converter is presented. Besides reducing control complexity, the FLC offers better transient response in the converter than the linear controller. Simulation results are presented to show this. Using describing function method, the system stability margins are also analyzed.

Evaluation of Power Losses in a Boost PFC Unit by Temperature Measurements

High power conversion efficiency is an important requirement of the front-end power-factor-corrected (PFC) boost rectifier that is used in shaping the ac input current in a typical modern switch-mode power supply. A reasonably accurate estimate of the power losses in individual components is essential in order to improve the efficiency of the PFC rectifier. In this paper, difficulties in the measurement of individual component power losses with particular reference to an ac-dc converter are brought out. A method of loss evaluation by measurement of temperatures of individual components and surrounding ambient is presented. Experimental results that are carried out on the front-end boost PFC rectifier of a commercial ac-dc converter are presented to validate the loss estimation method.

Tri-state boost converter with no right half plane zero

A challenging problem in the design of boost converters operating in continuous conduction mode is posed by the dynamically shifting right half plane (RHP) zero in the converters small signal control-to-output, transfer function. The paper proposes a novel tri-state boost converter without such a zero in the transfer function. The additional degree of freedom introduced in the converter in the form of a freewheeling interval has been exploited through an easy control technique to achieve this. The absence of the RHP zero allows the control scheme to achieve larger bandwidth under closed loop conditions, resulting in fast response. Analytical, simulation and experimental results of the tri-state boost converter have been presented and compared with the classical boost converter both under open loop and under closed loop operating conditions. The results clearly demonstrate the superior dynamic performance of the proposed converter. The proposed converter can be used in applications where fast response boost action is needed such as for single-phase power factor correction.

Evaluation of power losses in a boost PFC unit by temperature measurements

High power conversion efficiency is an important requirement of the front-end power-factor corrected (PFC) boost rectifier used in shaping the ac input current in a typical modern off-line power supply. A reasonably accurate estimate of the power losses in individual components is essential in order to improve the efficiency of the PFC rectifier. In this paper, difficulties in the measurement of individual component power losses with particular reference to an ac-dc converter are brought out. A method of loss evaluation by measurement of temperatures of individual components and surrounding ambient is presented. Experimental results carried out on the front-end boost PFC rectifier of a commercial ac-dc converter are presented to validate the loss estimation method.

Design and evaluation of tri-state boost converter

A tri-state boost converter proposed earlier avoids the dynamic response problem of single-switch boost converter operating in continuous-conduction mode by providing an additional inductor-free-wheeling interval. The converter offers an additional degree of control-freedom. Two variations of a multi-variable dual-mode control (DMC) scheme that effectively exploit this control freedom and aim to attain a good compromise between the contradictory multiple-goals of achieving good dynamic performance and high efficiency have also been proposed earlier. The dynamic and steady-state performances of the converter under DMC are closely interrelated and in turn decide the size and rating of power components and also the design of feedback controllers. The aim of this paper is to investigate the trade-offs involved in the design of DMC based tri-state boost converter and to present a systematic design procedure for both variations of the DMC schemes. The relation between dynamic and steady-state performances is investigated and used appropriately in selecting the power and control components. An example design is presented and the design is validated through simulations and experiments.

A Metric for Comparing the EMI Spectra of Power Converters

The inherent switching of power devices in a switch mode power supply generates electromagnetic interference (EMI) noise. This noise is dependent on several factors such as component layout, circuit parasitics, and the control techniques implemented. Several methods have been reported in literature to curtail the EMI problem. However, until now, a metric to compare the EMI spectra of power converters is not available in literature. In this paper, a simple metric to measure and characterize the EMI spectrum of a power converter is presented. The proposed technique is based upon the specification and thereby the size of an external passive filter required to meet the given EMI standards. The use of the metric is demonstrated through the comparison of the quality of spectra of two different implementations of an industrial power converter. The metric is also used to compare the spectra of a converter with two different switching schemes