This document describes a new transformerless buck-boost converter with a positive output voltage that was proposed by Sepuri Mahesh and Sepuri Yasaswini. The proposed converter has a simpler structure than traditional buck-boost converters and can achieve higher voltage gains. Simulation results show that the converter can operate in both step-up and step-down modes with positive output voltages. The converter has applications in portable electronics, electric vehicles, communication systems, and household appliances due to its ability to provide high voltage gains without an extreme duty cycle.

1. GATES INSTITUTE OF TECHNOLOGY
( Department of Electrical and Electronics Engineering)
A NEW TRANSFORMERLESS BUCK-BOOST
CONVERTER WITH POSITIVE OUTPUT VOLTAGE
Submitted by
SEPURI MAHESH
SEPURI YASASWINI
Under The Guidance of
Mr.N.GANGADHAR M.Tech
Associate professor
EEE.

2. ABSTRACT:
A new transformer less buck-boost converter with simple
structure is proposed in this study .
Compared with the traditional buck-boost converter, the
proposed buck-boost converter , voltage gain is squared times of
the former’s and its output voltage polarity is positive.
In the continuous conduction mode two inductors are
magnetised and two capacitors are discharged during the switch
on period, While two inductors are demagnetised and two
capacitors are charged during the switch of period.

3. OBJECTIVE:
•In this project a buck-boost converter is used in order to replace
the transfomer.
•A buck-boost converter gives higher efficiency and it is simple in
structure but it has some limited voltage gain with positive output
voltage.Due to this reason here we are using a buck-boost converter.

4. INTRODUCTION:
As is well known, switching-mode power supply is the core of
modern power conversion technology which is widely used in
electric power, communication system, house hold appliances,
and many other fields.
As the basis of switching mode power supply, converter
topologies attract a deal of attention and many converter
and many converter topologies have been proposed.
 The operating principles the steady state analyses , and the
small signal model for the proposed buck-boost converter
operating in continuous conduction mode are presented
in detail.

5. EXISTING SYSTEM:
 Luo converter can obtain high voltage gain by employing
the voltage lift technique, but the topological complexity,
cost, volume and losses increases the same time .
 Interleaved converters can achieve high step up or step
down conversion ratio with low voltage stress, while their
operating mode ,converter structure and control strategy
are complicated.

6. •In this proposed system, An additional switched network is inserted into
the traditional buck-boost converter a new transformerless buck-boost
converter is proposed.
•The main part of the proposed buck-boost converter is that its voltage
gain is quadratic of the traditional buck-boost converter so that it can
operate in a wide range of output voltage, that is, the proposed
buck-boost converter can achieve high or low voltage gain without
extreme duty cycle.
•Moreover, the output voltage of this new transformerless buck-boost
converter is common-ground with the input voltage, and its polarity is
positive.
PROPOSED SYSTEM:

7. CIRCUIT DIAGRAM:
Fig: Proposed transformer less buck–boost
converter

8. WORKING OF BUCK-BOOST CONVERTER
 According to the state of the power switches and diodes, some typical
time-domain waveforms for this new transformer less buck–boost
converter operating in CCM are displayed in and the possible operation
states for the proposed buck–boost converter are shown in fig.
 For it denotes that the power switches S1 and S2 are turned on,
whereas the diodes D1 and D0 do not conduct. Consequently, both the
inductor L1 and the inductor L2 are magnetized, and both the charge
pump capacitor C1 and the output capacitor C0 are discharged.
 It describes that the power switches S1 and S2 are turned off while the
diodes D1 and D0 conduct for its forward biased voltage. Hence, both
the inductor L1 and the inductor L2 are demagnetized, and both the
charge pump capacitor C1 and the output capacitor C0 are charged.
 Here, in order to simplify the circuit analyses and deduction, we
assumed that the converter operates in steady state, all components are
ideal, and all capacitors are large enough to keep the voltage across
them const

9. STEP-DOWN MODE:
Fig. Simulink model of step down mode

10. STEP-DOWN OUTPUT:
Fig capacitor (C1) and load resistances voltage wave forms of step down mode (voltage on Y-axis, time on X-axis)

11. STEP-DOWN OUTPUT:
Fig Voltage output at load in step down mode (voltage on Y axis ,time on X axis)
)

12. STEP-DOWN OUTPUT:

Fig.6.2.4: voltage across the Capacitor (voltage on Y axis, time on X axis)

13. STEP-DOWN OUTPUT:
Fig Current 𝐼𝐿1across inductor 1(current on Y axis, time
on X axis)

14. STEP-DOWN OUTPUT:
Fig. Current 𝐼𝐿2across inductor 2(current on Y axis, time
on X axis)

15. STEP-UP MODE:
Fig Simulink model of step up mode

16. STEP-UP OUTPUT:
• Fig capacitor (C1) and load resistances voltage waveform of step up mode
(voltage on Y axis, time on X axis)

17. STEP-UP OUTPUT:
Fig: 6.2.9 Current 𝐼𝐿1 across the inductor 1(current on Y axis, time on X axis)

18. Portable electronic devices
Car electronic devices
Communication system
Industrial device
House hold appliances
APPLICATIONS:

19. COMPARISION OF CONVERTERS

20. CONCLUSION:
 This Project has proposed a new transformer less buck–
boost converter as a fourth-order circuit, which realizes the
optimization between the topology construction and the
voltage gain to overcome the drawbacks of the traditional
buck–boost converter. The operating principles, steady-
state analyses, small signal modeling, and comparisons
with other converters are presented. from the MATLAB
simulations, it is proved that the new transformer less
buck–boost converter possesses the merits such as high
step-up/step-down voltage gain, positive output voltage.
Hence, the proposed buck–boost converter is suitable for
the industrial applications requiring high step-up or step-
down voltage gain.

21. REFERENCES:
[1] W. H. Li and X. N. He, “Review of non-isolated high
step-up DC/DC converters in photovoltaic grid-
connected applications,” IEEE Trans. Ind. Electron.,
vol. 58, no. 4, pp. 1239–1250, Apr. 2011.
[2] C. T. Pan and C. M. Lai, “A high-efficiency high
step-up converter with low switch voltage stress for
fuel-cell system applications,” IEEE Trans. Ind.
Electron., vol. 57, no. 6,
[3] T. F. Wu and Y. K. Chen, “Modeling PWM DC–DC
converters out of basic converter units,” IEEE Trans.
Power