IIT Madras is a public technical and research university located in Chennai, Tamil Nadu. Founded in 1959, it is recognised as an Institute of National Importance.

IIT Madras has been ranked as the top engineering institute in India for four years in a row by the National Institutional Ranking Framework of the MHRD

It currently offers undergraduate, postgraduate and research degrees across 16 disciplines in Engineering, Sciences, Humanities and Management. About 596 faculty belonging to science and engineering departments and centres of the Institute are engaged in teaching, research and industrial consultancy.

IIT Madras

This paper proposes an active soft-switching circuit for bridge converters aiming at improving the power conversion efficiency. The proposed circuit achieves loss-less switching for both main and auxiliary switches without increasing the main device current/voltage rating. It is capable of operating at elevated switching frequencies of several hundreds of kHz, at low and high power levels with a wide range of load variations. A winding coupled to the primary of power transformer ensures soft switching for the auxiliary switches during turn-on and turn-off. Phase Shifted Full Bridge (PSFB) topology is chosen to validate the design. Operation principle with analytical expressions for the proposed circuit are outlined. The proposed active soft switched PSFB DC-DC converter circuit is designed and implemented for 350 W, switching at 100 kHz. The simulation and experimental results are presented. Experimental results are used to validate the analysis. © 2012 IEEE.

Department of Electrical Engineering

PEDES 2012 - IEEE International Conference on Power Electronics, Drives and Energy Systems

A new active soft-switching circuit for full bridge converters

Active-clamp dcdc converters are pulsewidth-modulated converters having two switches featuring zero-voltage switching at frequencies beyond 100 kHz. Generalized equivalent circuits valid for steady-state and dynamic performance have been proposed for the family of active-clamp converters. The active-clamp converter is analyzed for its dynamic behavior under current control in this paper. The steady-state stability analysis is presented. On account of the lossless damping inherent in the active-clamp converters, it appears that the stability region in the current-controlled active-clamp converters get extended for duty ratios, a little greater than 0.5 unlike in conventional hard-switched converters. The conventional graphical approach fails to assess the stability of current-controlled active-clamp converters, due to the coupling between the filter inductor current and resonant inductor current. An analysis that takes into account the presence of the resonant elements is presented to establish the condition for stability. This method correctly predicts the stability of the current-controlled active-clamp converters. A simple expression for the maximum duty cycle for subharmonic-free operation is obtained. The results are verified experimentally. © 2011 IEEE.

IEEE Transactions on Power Electronics

Steady-state stability of current-mode active-clamp ZVS DC-DC converters

A novel soft transition push pull converter is proposed in this paper. The proposed circuit achieves loss-less switching for the two main and two auxiliary switches without increasing the main device current/voltage rating. A tapping in the isolation transformer is added for the purpose of commutation. The proposed circuit is capable of operation at elevated switching frequencies of several hundreds of kHz, in a range of line and load variations. Steady state performance, the operating principle and theoretical analysis is outlined for the proposed pushpull converter. The steady state conversion ratio and the equivalent circuit model is presented. Experimental results are presented which verifies the steady state performance of the converter. The experimental waveforms are in agreement with the theoretical. © 2011 IEEE.

IECON Proceedings (Industrial Electronics Conference)

Novel soft transition pushpull converter: Analysis, modeling, design and implementation

This paper analyzes the steady state operation of a Synchronous Soft Switched Buck Converter which has the advantages of both synchronous switching and soft switching. This topology employs an auxiliary circuit to achieve soft switching. The auxiliary circuit consists of a dependent voltage source, an auxiliary switch, a resonant diode, a resonant inductor and a resonant capacitor. The dependent voltage source is realized by a mutually coupled inductor. In this topology, the switching transitions of the active switch, the synchronous switch and the auxiliary switch are lossless. The design guidelines are presented and a 33 Watt converter is designed, simulated and fabricated to validate the operation of the converter. A microcontroller is used to generate the switching pulses. An improvement of 6% in efficiency is observed over traditional topologies. © 2011 IEEE.

2011 International Conference on Power and Energy Systems, ICPS 2011

Analysis, design and implementation of soft switching in a synchronous converter

The soft switching converters evolved through the resonant load, resonant switch, resonant transition and active clamp converters to eliminate switching losses in power converters. An improved two switch forward converter employing active clamp/reset is proposed for DC/DC conversion applications in this paper. The proposed circuit is capable of operation at elevated switching frequencies of several hundreds of kHz, in a range of line and load variations. Steady state performance, the operating principle and theoretical analysis is outlined for the proposed forward converter and a design procedure is developed. The steady state conversion ratio and the equivalent circuit model valid for steady state and dynamic model is presented. Experimental results are presented which verifies the steady state and dynamic performance of the converter. The experimental waveforms are in agreement with the theoretical.

World University root node

2010 IEEE 12th Workshop on Control and Modeling for Power Electronics, COMPEL 2010

An improved ZVS-PWM, active clamp/reset forward converter: Analysis, design and dynamic model

The soft switching converters evolved through the resonant load, resonant switch, resonant transition and active clamp converters to eliminate switching losses in power converters. This paper briefly presents the operating principle of the new family of soft transition converters; the methodology of design of these converters is presented through an example. In the proposed family of converters, the switching transitions of both the main switch and auxiliary switch are lossless. When these converters are analysed in terms of the pole current and throw voltage, the defining equations of all converters belonging to this family become identical. Such a description allows one to define simple circuit oriented model for these converters. These circuit models help in evaluating the steady state and dynamic model of these converters. The standard dynamic performance functions of the converters are readily obtainable from this model. This paper presents these dynamic models and verifies the same through measurements on a prototype converter.

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Sadhana - Academy Proceedings in Engineering Sciences

A new family of soft transition converters: Design and dynamic model

A novel auxiliary switch dc-dc converter with coupled inductor is presented in this paper. The proposed circuit achieves loss-less switching for both the main and auxiliary switches without increasing the main device current/voltage rating. A tapping in the pole inductor is added for the purpose of commutation. The proposed circuit is capable of operation at elevated switching frequencies of several hundreds of kHz, in a range of line and load variations. The proposed circuit is applicable to all isolated and non-isolated dc-dc converters. The performance and the design equations of the ZVS are identical for all types of dc-dc converters when the throw voltage and the pole current are properly defined. In the sections that follow, operating principle and theoretical analysis of the proposed circuit is outlined through the example of buck converter. Simulation and experimental results of 33 W, 400 kHz boost converter are presented. © 2007 IEEE.

A family of auxiliary switch ZVS-PWM DC-DC converters with coupled inductor

In the education of physical sciences, the role of the laboratory cannot be overemphasised. It is the laboratory exercises which enable the student to assimilate the theoretical basis, verify the same through bench-top experiments, and internalize the subject discipline to acquire mastery of the same. However the resources essential to put together such an environment is substantial. As a result, the students go through a curriculum which is wanting in this respect. This paper presents a low cost alternative to impart such an experience to the student aimed at the subject of switched mode power conversion. The resources are based on an open source circuit simulator (Sequel) developed at IIT Mumbai, and inexpensive construction kits developed at IISc Bangalore. The Sequel programme developed by IIT Mumbai, is a circuit simulation program under linux operating system distributed free of charge. The construction kits developed at IISc Bangalore, is fully documented for anyone to assemble these circuit which minimal equipment such as soldering iron, multimeter, power supply etc. This paper puts together a simple forward dc to dc converter as a vehicle to introduce the programming under sequel to evaluate the transient performance and small signal dynamic model of the same. Bench tests on the assembled construction kit may be done by the student for study of operation, transient performance and closed loop stability margins etc.

Proceedings of India International Conference on Power Electronics, IICPE 2006

A do-it-yourself (DIY) switched mode power conversion laboratory

A novel ZVS auxiliary switch commutated variation for all DC-DC converter topologies has been proposed in 2006. With proper designation of the circuit variables (throw current I and the pole voltage V), all these converters are seen to be governed by an identical set of equations. With idealized switches, the steady-state performance is obtainable in an analytical form. The conversion ratio of the converter topologies is obtained. A generalized equivalent circuit emerges for all these converters from the steady-state conversion ratio. It also provides a dynamic model as well. With these generalized steady-state equivalent circuits, small signal analysis of these converters may be carried out readily. It enables one to use the familiar state space averaged results of the standard PWM DC-DC converters for the resonant counterparts. Th dc and ac models reveals that dc and low frequency behaviour of the proposed family of converters is similiar to that of its PWM parent. ©2006 IEEE.

2006 International Conference on Power Electronics, Drives and Energy Systems, PEDES '06

A unified model for auxiliary switch commutated DC-DC converters

Active-clamp DC-DC converters belong to the family of two-switch pulse-width modulated converters featuring zero-voltage switching. The topological structure of these converters in relation to their hard-switched PWM converters is highlighted. With proper designation of the circuit variables (throw current I and the pole voltage V), all these converters are seen to be governed by an identical set of equations. In this framework, these circuits exhibit 6 subperiods per cycle with identical current waveform in the resonant inductor. With idealized switches, steady-state performance is obtainable in an analytical form. This set of equations may be solved through a simple spreadsheet programme, which provides a design constraint on the normalized current. A generalized equivalent circuit emerges for all these converters from this steady-state conversion ratio. It also provides a dynamic model as well. The circuit model proposed in this paper enables one to use familiar state-space averaged results of the standard PWM DC-DC converters (steady-state and dynamic) for their ZVS active-clamp counterparts. With these equivalent circuits, small-signal analysis of these converters is akin to that of hard-switched converters. As an extension of the work, a unified dynamic model for ZVS active-clamp converters is proposed in this paper. Small-signal transfer functions like audio-suceptibility, control gain, output impedance, input admittance of buck, boost, buck-boost active-clamp converters are derived. Simulation and experimental results showing the steady-state and dynamic performance of these family of converters are presented. © Indian Institute of Science.

Journal of the Indian Institute of Science

Unified model for ZVS DC-DC converters with active clamp

Active clamp dc-dc converters are recently introduced family of two switch pulse width modulated converters featuring zero-voltage switching. The topological structure of these converters in relation to their hard-switched PWM converters is highlighted. With proper designation of the circuit variables (throw voltage V and the pole current I), all these converters are seen to be governed by an identical set of equations. In this framework, these circuits exhibit 6 sub-periods per cycle with identical current waveform in the resonant inductor. With idealized switches, the steady-state performance is obtainable in an analytical form. This set of equations may be solved through a simple spreadsheet programme. The steady-state performance provides a design constraint on the normalized current. The conversion ratio of the converter is also readily available. A generalized equivalent circuit emerges for all these converters from this steady-state conversion ratio. It is interesting to note that this equivalent circuit provides a dynamic model as well. The circuit model proposed in this paper enables one to use the familiar state space averaged results of the standard PWM dc-to-dc converters (both steady-state and dynamic) for their ZVS active clamp counterparts.