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117 D. Govind, Nandkumar Wagh

International Journal of Electronics, Electrical and Computational System

IJEECS

ISSN 2348-117X

Volume 6, Issue 6

June 2017

Resonant DC DC Buck - Boost Converter for the Battery Charger

and PV Applications

1D. Govind, 2 Nandkumar Wagh 1Assistant Professor, 2 Professor

Department of Electrical Engineering,

Vidya Pratishthans Kamalnayan Bajaj Institute of Engineering and Technology,

Baramati, Pune(M.S.)-India

AbstractIn power electronic switches, soft switching is

a possible way of reducing losses. Soft switching refers

to the operation of power electronic switches as zero-

voltage switches (ZVS). All the power electronic

switching devices undergoes zero-voltage switching

during turn-off. In the converter, the switches undergo

zero-capacitive turn-on losses unlike switches in other

soft-switched topologies. This soft-switching technique

can also be applied to other classical switched mode

power converters. The structure of the proposed

converter is simpler and cheaper than other resonant

power converters. In this paper, single-switch resonant

power converter offering the advantages of soft

switching, reduced switching losses, and increased

energy conversion efficiency for Photovoltaic

applications is presented. This circuit topology integrates

a single-switch resonant converter with zero-voltage-

switching. The operating principles and the steady-state

analyses of the proposed interleaved buck, boost buck-

boost converters are discussed and performance of grid

connected ZVS is verified with simulation results.

KeywordsZVS, buck, boost, buck boost.

This paper is divided in five sections. Section-I

presents the introduction of switching modes in

converters and the literature related to it.

Section-II presents all converter topologies.

Simulation results of the converter topologies are

depicted in Section-III.

Section-IV and V deals with the comparison of

converter topologies and the comparative analysis.

I. INTRODUCTION

DC-DC converters are finding more and more

use in portable applications such as cell phones,

laptops etc. In order to achieve higher power

density and high voltage profile, these converters

are usually require to operate at higher switching

frequencies with higher efficiencies[1]-[2].

When the switching frequencies continues to

increase , then in order to meet the future

requirements of power density and efficiency, the

Resonant DC-DC converters redraw peoples

attention. Resonant converters are good alternative

because of its soft-switching power transfer

characteristic. These converters can considerably

reduce the switching loss and obtain friendly EMI

characteristics [3]. Therefore we can operate the

converter at higher frequencies without sacrificing

the efficiency, so high efficiency and high power

density can be achieved simultaneously. In

Resonant converters because of smooth voltage and

current waveforms, noise and interference and

stress on switching devices are reduced and

parasitic circuit elements such as transformer

leakage inductance can be taken into account.

In the 1970s, conventional PWM power

converters were operated in a switched mode

operation. Power switches have to cut off the load

current within the turn-on and turn-off times under

the hard switching conditions. Hard switching

refers to the stressful switching behavior of the

power electronic devices. The switching trajectory

118 D. Govind, Nandkumar Wagh

International Journal of Electronics, Electrical and Computational System

IJEECS

ISSN 2348-117X

Volume 6, Issue 6

June 2017

of a hard-switched power device is shown in Fig.1.

During the turn-on and turn-off processes, the

power device has to withstand high voltage and

current simultaneously, resulting in high switching

losses and stress. Dissipative passive snubbers are

usually added to the power circuits so that the dv/dt

and di/dt of the power devices could be reduced,

and the switching loss and stress are diverted to the

passive snubber circuits [4].

However, the switching loss is proportional to

the switching frequency, thus it is required to limit

the maximum switching frequency of the power

converters. Typical converter switching frequency

was limited to a few tens of kilo-Hertz (typically 20

kHz to 50 kHz) in early 1980s.

I

VOff

On

Soft-switching

Hard-switching

Safe Operating Area

snubbered

Fi

g.1 Typical switching trajectories of power

switches

The stray inductive and capacitance in the power

circuits and power devices still cause considerable

transient effects, which in turn give rise to

electromagnetic interference (EMI) problems [3].

Fig.2. shows ideal switching waveforms and typical

practical waveforms of the switch voltage. The

transient ringing effects are major causes of EMI.

In the 1980s, lots of research efforts were diverted

towards the use of resonant converters. The concept

was to incorporate resonant tanks in the converters

to create oscillatory, usually sinusoidal voltage and

current waveforms so that zero voltage switching

(ZVS) or zero current switching (ZCS) conditions

can be created for the power switches. The

reduction of switching loss and the continual

improvement of power switches allow the

switching frequency of the resonant converters to

reach hundreds of kilo-Hertz (typically 100 kHz to

500 kHz). Consequently, sizes of elements can be

reduced and the power density of the converters is

increased. Various forms of resonant converters

have been proposed and developed.

Fig.2. Typical switching waveforms of (a) hard-

switched and (b) soft-switched devices

Resonance Technology

There are basically two types of soft-switching

techniques:

1. Zero Current Switching (ZCS)

2. Zero Voltage Switching (ZVS)

Either of this technique can greatly reduce and even

completely eliminates the switching losses in a

converter. High power level converters usually use

IGBT switches due to low conduction losses and

higher power capability, but IGBT is not as fast as

MOSFET [5]- [8] and its switching frequency

cannot be increased beyond 100 KHz even if softly

switched. On the contrary to Insulated Gate Bipolar

Junction Transistor (IGBT), Metal Oxide

Semiconductor Field Effect Transistor (MOSFET)

is resistive device. When it is turned on, the

conduction losses are higher as compared to IGBT

at higher power levels. However, MOSFET is a

faster device and is able to operate up to a few

MHzs.

Fig.3. Shows current and voltage waveforms of

hard and resonant switching system with portion of

losses in both.

Fig.3. Current and voltage waveforms of hard and

resonant switching systems

119 D. Govind, Nandkumar Wagh

International Journal of Electronics, Electrical and Computational System

IJEECS

ISSN 2348-117X

Volume 6, Issue 6

June 2017

ZVS converters have three resonant states: over

resonance (completed resonance), optimum

resonance (critical resonance) and quasi resonance

(sub resonance). Only the quasi resonance state has

two zero crossing points in a repeating period. A

resonant switch is a sub-circuit comprising a

semiconductor switch S and resonant elements, Lr

and Cr. The switch S can be implemented by a

unidirectional or bidirectional switch, which

determines the operation mode of the resonant

switch. [4].

II. ZERO VOLTAGE RESONANT SWITCH

(ZVS)

In zero voltage switching resonant converters,

the resonant capacitor provides a zero-voltage

condition for the switch to turn on and off [7]. A

quasi-resonant buck converter designed for half-

wave operation using a ZV resonant switch as

shown in Fig.4. In a ZV resonant switch, a

capacitor Cr is connected in parallel with the switch

S for achieving zero-voltage-switching (ZVS). If the

switch S is a unidirectional switch, the voltage

across the capacitor Cr can oscillate freely in both

positive and negative half-cycle. Thus, the resonant

switch can operate in full-wave mode. If a diode is

connected in anti-parallel with the unidirectional

switch, the resonant capacitor voltage is clamped by

the diode to zero during the negative half-cycle.

The resonant switch will then operate in half-wave

mode. The objective of a ZV switch is to use the

resonant circuit to shape the switch voltage

waveform during the off time in order to create a

zero-voltage condition for t

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