MODELLING AND SIMULATION OF SOFT-SWITCHING DC/DC CONVERTER WITH HIGH VOLTAGE GAIN


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INTRODUCTION

Recently, the demand for dc/dc converters with high
voltage gain has increased. The energy shortage and
atmosphere pollution have led to more researches on the
renewable and green energy sources such as the solar
arrays and the fuel cells. Moreover, the power systems
based on battery sources and super capacitors have been
increased. Unfortunately, the output voltages of these
sources are relatively low. Therefore, the step-up power
conversion is required in these systems. Besides the
step-up function, the demands such as low current
ripple, high efficiency, fast dynamics, light weight, and
high power density have also increased for various
applications .Input current ripple is an important factor
in a high step-up dc/dc converter.


ANALYSIS OF THE PROPOSED CONVERTER

the circuit diagram of the proposed soft
switching dc/dc converter with high voltage gain. The
switches S1 and S2 are operated asymmetrically and the
duty ratio D is based on the switch S1. D1 and D2 are
intrinsic body diodes of S1 and S2. Capacitors C1 and
C2 are the parasitic output capacitances of S1 and S2
.The proposed converter contains a CCM boost cell. It
consists of LB , S1 , S2, Co1, and Co2. The CCM boost
cell provides a continuous input current. When the
switch S1 is turned on, the boost inductor current iLB
increases linearly from its minimum value ILB2 to its
maximum value ILB1 .



Voltage Stress of Devices

Generally, high output voltage will impose high-voltage
stress across the switching devices in dc/dc converters.
In the proposed dc/dc converter, the voltage stresses
across the switching devices are smaller than the output
voltage.


CONCLUSION
A soft-switching dc/dc converter with high voltage gain
has been proposed in this paper. The proposed converter
can minimize the voltage stresses of the switching
devices and lower the turn ratio of the coupled inductor.
It provides a continuous input current, and the ripple
components of the input current can be controlled by
using the inductance of the CCM boost cell. Soft
switching of power switches and the alleviated reverserecovery
problem of the output rectifiers improve the
overall efficiency.