The document discusses high step-up DC-DC converters used to boost the output voltages of photovoltaic (PV) cells and fuel cells. It proposes a new converter design that combines switched capacitor and switching mode converter topologies. This allows increasing the voltage gain while maintaining high efficiency. The design introduces multiple capacitors charged in parallel and discharged in series to boost output voltage. It can provide regulated voltage and infinitely scale voltage gain as needed for applications like powering grid-connected PV and fuel cell inverters.

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Non isolated High Step-Up DC-DC Converters
Adopting Switched-Capacitor Cell
Abstract
The mass usage of traditional fossil energy has adversely affected
the environment on a global scale, such as environmental pollution and
greenhouse effect. Meanwhile, there has been a growing demand for
energy with the development of society. Since traditional fossil energy is
not renewable, it is faced with the problem of energy shortage. Solar
energy and hydrogen energy are promising, and photovoltaic (PV) and
fuel cell power generation as the utilization method of the two new
energy types have been applied on a large scale. In a single-phase
system with a two-stage structure, if the line voltage is 220 V, the bus
voltage of the grid-connected inverter needs to be as high as 380 V.
However, the output voltages of PV and fuel cells are generally ranged
from 25 to 45 V, which are much lower than the bus voltage. Thus, a
dc–dc converter with a high voltage gain is needed to boost the outputs
of PV and fuel cells. By increasing the turns ratio of the transformer in
isolated converters, a high voltage gain can be obtained. However, a too
large turns ratio will lead to a large leakage inductor. As a result, the
voltage stress of the switch will be increased, whereas the efficiency of
the converter is degraded.
Existing system
A boost converter (step-up converter) is a DC-to-DC power
converter with an output voltage greater than its input voltage. It is a

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class of switched-mode power supply (SMPS) containing at least two
semiconductors (a diode and a transistor) and at least one energy storage
element, a capacitor, inductor, or the two in combination. Filters made of
capacitors (sometimes in combination with inductors) are normally
added to the output of the converter to reduce output voltage ripple.
Proposed system
The voltage gain of the SC converter is high, but the output voltage
is not regulated. The output regulation of the nonisolated switching-
mode dc–dc converter is excellent, but the voltage gain cannot be too
high for achieving high efficiency. This paper proposes a combination
method of the SC converter and the switching-mode dc–dc converter.
The basic approach is introducing multiple capacitors into the switching-
mode dc–dc converters. When the switch is off, the energy released from
the inductor is used to charge the capacitors in parallel. When the switch
is on, the capacitors are connected in series to supply the load. Thus, the
voltage gain is increased, and the duty cycle is decreased, leading to
small ripple current and turnoff current of the switch, and high
efficiency can be expected. Meanwhile, the voltages of the capacitors
are well regulated, thus achieving a tightly regulated output voltage. In
addition, the new converters proposed in this paper can be infinitely
extended when an enormous voltage gain is needed.

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LeMeniz Infotech
36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue,
Pondicherry-605 005.
Call: 0413-4205444, +91 9566355386, 99625 88976.
Web : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
Advantages
 Voltage gain is increased.
 High efficiency.
Applications
 PV and fuel cells.

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LeMeniz Infotech
36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue,
Pondicherry-605 005.
Call: 0413-4205444, +91 9566355386, 99625 88976.
Web : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
Block diagram:
INPUT DC
SUPPLY
LOADBOOST / BUCK–BOOST
BASED CONVERTER
12V
DC
OPTO COUPLER CIRCUIT
5V DC PIC CONTROLLER WITH
BUFFER

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LeMeniz Infotech
36, 100 Feet Road, Natesan Nagar, Near Indira Gandhi Statue,
Pondicherry-605 005.
Call: 0413-4205444, +91 9566355386, 99625 88976.
Web : www.lemenizinfotech.com / www.ieeemaster.com
Mail : projects@lemenizinfotech.com
Tools and software used:
 MPLAB – microcontroller programming.
 ORCAD – circuit layout.
 MATLAB/Simulink – Simulation.