THE NEW TOPOLOGY FOR VOLTAGE INVERTER
USING FORWARD CONVERTER
Gerson Osviani
Ana Paula Bolognini
Carlos Henrique Gonçalves Treviso
Universidade Estadual de Londrina – UEL
Centro de Tecnologia e Urbanismo – CTU
Departamento de Engenharia Elétrica – DEEL
Campus Universitário – Caixa Postal: 6001
CEP 86051-990, C.P. 000, Londrina - PR
Brasil
e-mail: [email protected]
Abstract – This work presents a new topology of a
frequency inverter with four Forward converters, in a
parallel topology configuration. These converters present
a modification to avoid a circuit intervening on the
functioning of other. The resultant power is 800W, and
its switching frequency is 20 kHz. A complete analysis of
the operating stages, as well as the design procedures for
the correct operation of this topology are presented.
Simulation results, which correspond to the complete
functioning of the circuit, are presented to validate the
analysis of the system.
1
Keywords – Voltage Inverter, New Topology of
Forward Converter.
NOVA TOPOLOGIA PARA INVERSOR DE
TENSÃO USANDO CONVERSOR
FORWARD
Resumo – Este trabalho apresenta uma nova topologia
de inversor de freqüência formado por quatro
conversores Forward em paralelo. Estes conversores
apresentam uma modificação para evitar que um circuito
interfira no funcionamento do outro. A potência
resultante é de 800W, com freqüência de chaveamento de
20 kHz. É apresentada uma completa análise das etapas
de operação bem como os procedimentos de projeto para
a correta operação dessa topologia. Resultados de
simulação, que correspondem ao funcionamento
completo do circuito, são apresentadas para validar a
análise do sistema.
Vp
Vr
f
C
R
L
Peak voltage.
Peak-peak voltage.
frequency.
Capacitance.
Resistence.
Indutance.
I. INTRODUÇÃO
The new topology of frequency inverter is formed by four
Forward converters, with 12VDC input and senoidal output
of 110V RMS and low TDH (Total Harmonic Distortion).
The signal to control of switch is the PWM (Pulse Width
Modulation). The power of the inverter is 800 W and the
switching frequency is 20 kHz.
In this work it is analyzed the Forward converter, shown
in the Figure 1 and a new topology of inverter, shown in the
Figure 2.
Fig. 1. Complete circuit of Forward converter.
Palavras-Chave – Inversor de Tensão, Nova Topologia
do Inversor Forward.
NOMENCLATURA
IDmáx
IL
Peak current.
RMS current.
Fig. 2. New topology of inverter.
Revisão 0.
II. SCHEME
The new topology of a frequency inverter is formed by
four modified Forward converters, in parallel, as shown in
Figure 1. This topology considers the converters A and B as
generator of positive pulses in the load. The converters, in
parallel, have the largest duty-cycle at the output equal to
1.0. When one of the converters is demagnetized, the other is
providing energy. The same occurs for converters C and D,
in parallel, which in turn generate the negative pulses. The
switches are MOSFETS and they are used when the
switching frequency is greater than 20kHz. They are
activated to permit that diodes conduct during defined
intervals. The four converters’ outputs are connected as
shown Figure 2.
Each converter can be seen in the Figure 3.
One cycle of the inverter, can be separated into ten
different steps, as shown in the following figures. The black
line shows the way of the current flows for each step.
Step 1 – Transfer of energy to the load using converter A:
the switches M1, M2 and M3 are controlled in order that
converter A transfers power to the load. During this period,
the other converters are disconnected, free to demagnetize
their cores if necessary.
Fig. 6. Step 1.
Step 2 – Transfer of energy to the load using converter B:
when the switches M4, M5 and M6 are controlled for the
converter B transfers energy to the load.
Fig. 3. Each Converter.
It’s necessary to use switches in secondary coil to avoid
that one converter interferes the other. The Figure 4 shows
the resulting circuit.
Fig. 7. Step 2.
Fig. 4. Circuit for each inverter.
Step 3 – Discharge of energy through converter C: the
switches M7, M8 and M9 are controlled for the converter C
transfers power to the load. But, the inductor is still loaded,
the transfer of energy is done from the load to the source
through the converter C.
The switch 2 isolate the secondary when the converter
does not transfer power, demagnetizing the core through the
demagnetizing coil and the signals coming from the others
converters.
III. OPERATION PROCESS
The steps of functioning can be divided in one cycle of the
senoidal wave, as shown in the Figure 5.
Fig. 8. Step 3.
Fig. 5. Steps of functioning of the inverter.
Step 4 – Discharge of energy through converter D: the
switches M10, M11 and M12 are controlled for discharge the
load in the source through the converter D.
the transfer of energy is done from load to the source through
the converter A.
Fig. 12. Step 7.
Fig. 9. Step 4.
Step 5 – Transfer of energy for the load with the converter
C: the load is discharged and the switches M7, M8 e M9 are
controlled to the converter C transfers energy for the load.
This is similar to step 1 except that now there is a negative
voltage on the load.
Step 8 – Discharge of energy through converter B: the
switches M4, M5 and M6 are controlled for discharging the
load in the source through the converter B.
Fig. 13. Step 8.
Fig. 10. Step 5.
Step 6 – Transfer of energy for the load with the converter
D: the switch M10, M11 and M12 are controlled for the
converter D transfers energy to the load.
Fig. 11. Step 6.
Step 7 – Discharge of energy through the converter A: the
switches M1, M2 and M3 are controlled for the converter A
transfers power for the load. But, the inductor is just loaded,
Step 9 – Dead time between the switches A and B: the
switch M13 is controlled providing a way for the current
ILOAD during the time between the controlling for the
converter A and B. The control must guarantee the switch
M13 is not controlled during the steps 3, 4, 5 and 6 and
during the time between these steps. This might damage to
converters short-circuit in the output of the converters C and
D.
Fig. 14. Step 9.
Step 10 – Dead time between the switches C and D: the
switch M14 is controlled providing a way for the current
ILOAD during the time between the control for the converters
C and D. Your are not controlling must be guaranteed during
the steps 1, 2, 7 and 8 among them, to avoid a burn out in the
output of the converters A and B.
The RMS current in secondary of each converter is [4].
Is =
IoTOTAL
= 1,85 (A)
4
(2)
The RMS current in primary is [4].
Ip =
1,85
= 37 (A)
0,05
(3)
The peak of current for loads with rectifier in input can be
given by Equation 4 [8].

(4)
Vp 

i Dmáx = IL 1+ 2π

2 × VR 

Fig. 15. Step 10.
VR = VP
In the secondary of the converter is connected a reactive
load, composed by the output filter and the load. Then, there
are cycles of power transfer to the load and cycles of
discharge form load to source.
The dead time is from the period which does not transfer
energy and it is used by the free wheeling diode to maintain
the current stored by the inductor.
The Figure 16 shows the switching of transistors. The
switch M13 is the counterpart of the switches M1, M2, M3,
M4, M5 and M6; and the switch M14 is the counterpart of
the switches M7, M8, M9, M10, M11 and M12.
1
2 × f × C× R
(5)
With frequency of 60Hz, peak voltage 110V, load 21,1Ω
and the capacitor of 440µF, the peak-peak voltage is found
by Equation 5 [8].
1
(6)
f =
c
2π LC
With Equation (6), considering fc equal 2kHz and a
capacitor of 10µF, we can obtain a inductor of 280µH.
For this project, the value of current found is 40,45A
(by Equation 4).
For this peak of current and this value of inductor, it is
necessary an air coil, because the coil of Fe does not tolerate
this peak of energy. Wrapping 180 spirals in a tube of
diameter 2cm and 9cm of width, we obtain an inductance of
280µH.
The area of Cu necessary for primary is 108,82.10-3cm2,
considering Skin Effect, because the component of the
current in high frequency, corresponding 14 thread of 25
AWG.
V. SIMULATION RESULTS
Simulate the operation of the new topology of the voltage
inverter the software package PSpice® AD 8.0 was used. The
complete circuit simulated is shown in Figures 17.a, 17.b,
17.c and 18.
Fig. 16. Waveforms.
IV. DESIGN EXAMPLE
The output power for the inverter is 800W, and each
inverter has 200W. The input voltage is 12V for all
converters. The output voltage is 110VAC RMS. With
relation transformations of 0,05, the output voltage is 240V.
The RMS output current in the inverter is [1].
IoTOTAL =
Ps
=
800
(1)
= 7,3 (A)
Fig. 17.a. Output differential amplifier and inverting adder with a
proportional integrator compensator.
TABLE I
Parameters
Apparatus and Values
Fig. 17.b. Pulse comparator and separator.
Components
Primary of
transformer
Simulation
VDSmax = 24V
IRMS = 16,5A
Secondary of
transformer
VDsmax = 240V
IRMS = 1,8A
Diodes
VDsmax = 240V
IRMS = 3,6A
Diodes of
demagnetizition
VRmax = 24V
IRMS = 2,9A
Diodes of
magnetizition
VRmax = 240V
IRMS = 3,6A
Real
IRFZ48N
VDS = 55V
ID = 64A
IRF740
VDS = 400V
ID = 10A
IRF740
VDS = 400V
ID = 10A
UF5404
VR = 400V
ID = 3A.
MUR850
VR = 500V
ID = 8A
Also due to switching frequency, every diode is Ultra-fast
Recovery rectifier.
The Simulation produced the waveform shown in Figure
19.
Fig. 19. Output voltage of the simulation.
In this figure, there is a little distortion in the waveform,
because it is difficult to adapt the cut’s frequencies of the
control circuit with the power circuit.
VI. ACTUAL RESULTS
Fig. 17.c. Multiplexer.
In order to verify the operation of the new topology of the
voltage inverter, the circuit shown in the Figures 17.a, 17.b,
17.c, and 18 were implemented.
The output waveform of the inverter for a non-reactive
load is shown in Figure 20.
Fig. 18. Isolator.
Fig. 20. Output voltage of the prototype.
In this figure, the waveform has senoidal component with
low TDH, because the implementation of a closed loop and
adjustments were exity possible in the laboratory including
charging some capacitors.
Power". USA, 1992.
VII. PHOTO OF PROTOTYPE
[3] Martins, Denizar C., "Inversor Ponte Completa ZVS
PWM com Grampeamento Ativo utilizando a Energia
de Recuperação Reversa D” (in Portuguese), CBA 2002
– Natal – RN – Brasil.
After the simulation result, it was done and tested in
laboratory the prototype of the converter with closed loop.
[4] Mello, Luiz F. P., "Projeto de Fontes Chaveadas” (in
th
Portuguese), Ed. Érica, 3 ed., 1990.
[5] Motorola Semiconductor, "Cmos Logic Data", 1985.
[6] Ogata, K., "Engenharia de Controle Moderno” (in
Portuguese). Prentice – Hall do Brasil Ltda, 1982.
[7] Rashid, Muhammad H., "Power Eletronic," MAKRON
nd
Books Ed., 2 ed., 1993.
Fig. 21. Photo of the circuit done in laboratory.
VIII. CONCLUSION
In this work it was described a new topology for the
voltage inverter with high frequency transformer and PWM
modulation.
The simulation of the circuit and the tests of prototype
produced good results, including low noise, even necessary,
the converters needed to be isolated. increasing the number
of components and as a consequent increasing a complexity
of the circuit. With power divisor among four Forward
converters it was possible the design of a high
power
inverter (800W) with small magnetics cores.
This topology, compounded by four converters in parallel,
offers a good efficiency with a single step of convertion,
justifying its application for commercial purposes even
though it was designed with fourteen switches. Owing to its
effeciency this prototype can be easyly adapted for audium
amplifiers.
REFERENCES
[1] Chryssis, G. C., "High – Frequency Switching Power
Supplies / Theory and Design". McGRAW Hill
International, Editions 1989.
[2] Harris Semiconductor, "Power MOSFETs / IGBT /
Ultrafast Rectifiers / Intelligent Discretes / Intelligent
[8] Sedra, Adel S., SmithH Kenneth, "Microelectronic
Circuits". MAKRON Books Ed, São Paulo – Brazil,
2000.
[9] Treviso, Carlos H. G., "Retificador de 6kW, Fator de
Potência Unitário, Trifásico, Comutação não-dissipativa
na Conversão CC/CC e Controle Sincronizado em
Freqüência, (in Portuguese)". Tese de Doutorado,
Uberlândia – MG – Brazil, March, 1999.
BIOGRAPHY
Carlos Henrique Gonçalves Treviso, was born on
05/05/1968 in Pontal – São Paulo – Brazil, received the B.Sc.
degree in electronics engineering (1991), the M.S. (1994)
and Dr. in electrical engineering (1999) from Federal
University of Uberlandia.
He was, from 2000 to 2001, coordinated the Electrical
Engineering Course. He is Professor and Vice-Director of
Center of Technology and Urbanism of State University of
Londrina.
He did many consult for companies. His areas of research
include: power electronics, electrical energy processing
quality, electronics control systems and electrical machines
starting.