Design of Step-Up Converter For A Constant Output in A High Power Design
Design of Step-Up Converter For A Constant Output in A High Power Design
Design of Step-Up Converter For A Constant Output in A High Power Design
Correspondence:
Ashwan A Busanur
M. Tech, (VLSI Design and
Embedded systems), The
Oxford College of Engineering
Bangalore, Karnataka, India.
1. Introduction
The industry nowadays moving toward more efficient high power designs and more efficient
electronics has led to the development of the Switch Mode Power Supply (SMPS). There are
several topologies commonly used to implement SMPS. In several technical applications,
there is a requirement to convert a DC source voltage into a variable-voltage DC output. A
DC to DC voltage can be obtained using simply a DC-DC switching converter and is simply
known as a DC Converter. AC transformer with a continuously variable turns ratio is similar
to a DC converter. It can be used to step down or step up a DC voltage source, as a
transformer.
In the current market field we can find many high power Switch Mode Power Supply
(SMPS) module, but the power density and efficiency is still less. Hence the demand for
higher efficiency with smaller design is in very much need for the current and the future
world. High-switching-frequency operation is necessary to achieve small size of the
converter. However, the switching loss will increase as the switching frequency is increased.
To solve this problem, soft switching techniques are necessary. The zero-voltage-switched
(ZVS) technique and zero-current-switched (ZCS) technique are two commonly used soft
switching methods [2]. By implementing these techniques, either voltage or current is zero
during switching transitions, which largely reduces the switching loss and increases the
efficiency and also increases the reliability of the power supplies.
The selection of the soft-switching technique, i.e., ZCS or ZVS, these considered techniques
is the technology of the semiconductor device that is accounted and will be used. For
instance, when commutated under ZVS the Power MOSFETSs present a better performance,
as when operating in ZCS they exhibit turn-on capacitive losses with increasing the
switching losses and EMI. On the other hand, the IGBTs present better results when are
commutated under ZCS which can avoid their lath up and the turn-off losses caused by the
tail current. However, the ZCS techniques suffers from some drawbacks such as, a
significant voltage stress on the main diode, which increases the conduction losses, and the
presence of the resonant inductor in series with the main switch, which increases the
magnetic losses [3].
2. Proposed Topology
Fig 1, is the proposed block diagram, the three phase diode bridge rectifier is used to convert
the ac line input voltage to the dc value. The circuit consists of an interleaved boost
converter. With the help of this interleaving technique, inductor current of interleaved boost
~125~
blocking the conduction. A low-pass filter using nondissipative passive components such as inductors and
capacitors is placed after the semiconductor switch, to
provide constant DC output voltage. The semiconductor
switches (IGBT) used to implement switch mode power
supplies are continuously switched on and off at high
frequencies (20 kHz) to transfer electrical energy from the
input to the output through the passive components.
The main inductor is added in series with interleaved boost
converter to reduce the peak current which reduces the turnon losses, and the interleaved technique reduces the
switching frequency by half which reduces size of the
auxiliary inductors. Hence we can have higher efficiency and
higher power density with reduced size at high power
designs. Using of nano-crystalline core for inductor
components reduces the size of overall circuit.
The output voltage is controlled by varying the duty cycle,
frequency or phase of the semiconductor devices transition
periods. As the switching frequency is inversely proportional
to the size of the passive components, a high switching
frequency results in smaller sizes for magnetics and
capacitors.
3. Design Procedure
The design procedure for the proposed soft switched
interleaved boost converter where main inductor operating in
continuous conduction mode (CCM) and auxiliary inductors
in discontinuous conduction mode (DCM), are presented in
this section.
4. Operating Requirements
Pout (max):
33 kW
Vin range:
415 AC
Line frequency range:
50Hz
Output voltage:
650 VDC
5. Switching Frequency
The selection of switching frequency is generally somewhat
arbitrary. The switching frequency must such that it should
be high enough to make the power circuits small and
minimize the distortion and must be low enough to keep the
efficiency high. Switching frequency range in most
~126~
Ipk =
...(11)
Iripple
=
rms
-I
avg
...(14)
....(15)
...(3)
Rectified voltage
Cout
..(16)
D = 0.13846
Vg = 560V
Io = 50.78A
Po = 33kW
Ro = 13
..(4)
Output current
..(5)
Iavg = 59.92A
Ipk = 68.35A
Irms = 63.46A
Iripple = 23.6A
Lmain = 163uH
Laux =1.38uH
Cout = 168uF
Output power
(6)
.....(7)
From the above equation
Ro =
..(12)
..(13)
Lmain =
Laux =
Vo =
Vg ....(1)
Iin = 58.92A ....(2)
.......(10)
.............................................(8)
7. Selection of Inductors
The inductor determines the amount of high frequency ripple
current in the input and its value is chosen to give some
specific value of ripple current. Inductor value selection
begins with the peak current of the input sinusoid.
8. Simulation Results
The computer simulation of proposed converter is done using
TINA and the results are presented. The simulation result of
input voltage and input current is shown in figure 2(a) and
figure 2(b) respectively. The simulation result of rectifier
output voltage, output voltage, output current, output of pulse
generators are shown
Iavg = 58.92A.........(9)
~129~