SMPS Non-Isolated Converters – The Three Types - Miracle Electronics

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Switched Mode Power Supplies (SMPS) are much
complex as compared to linear regulated power
supplies, but the complexity results in stable
regulated DC supply, delivering more efficiency
at a lesser weight and cost. There are two main
categories of SMPS topologies isolated
converters and non-isolated converters. But, in
this blog, well take a closer look at only
non-isolated converter topologies, focusing on
three main types of converters buck, boost,
and buck-boost.
Buck converters Buck converters convert high
input voltage into a stabilized lower output
voltage. It is a simple non-isolating circuit
with the inductor current controlled by a top
switch and diode, making it absolutely suitable
for step down voltages as a DC-to-DC
converter. Working When the switch is switched
on, the energy is transferred to the load as
well as the inductor. And, when it is switched
off, the inductor voltage reverses and the
freewheeling diode becomes forward biased, with
the energy stored in the inductor supplying the
load, providing effective filtering of the
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inductor current. Thus, the buck and its
derivatives all have very low output ripple
characteristics. The buck is generally always
operated in continuous mode where peak currents
are lower, and the smoothing capacitor
requirements are smaller. Advantages
disadvantages As you can see, buck converters
are very simple, requiring only one power
switch. Moreover, the size and cost of such
converters are comparatively very low, with the
efficiency being as large as 90, and the line
voltage variation having large tolerance.
However, with all these advantages, there is one
small disadvantage that the PWM regulator
feedback circuit requires a minimum output
ripple to regulate properly. But, despite the
drawback, many applications like RAMs, CPUs, and
USBs utilize buck converters due to the number
of advantages they offer. Boost converters Boost
converters convert lower input voltage into a
stabilized higher output voltage. When the
switch is switched on, the diode is reverse
biased, and the energy is stored in the
inductor, and the capacitor supplies current to
the load. And, when it is switched off, the
energy stored in the inductor is transferred to
the load. Here, the output voltage can be higher
than the input due to the summation of the
voltage pre-stored in the inductor and
Voltage-In. Working The current supplied to the
output smoothing capacitor from the converter
must be large, with a low equivalent series
resistance, in order to produce a relatively
acceptable output ripple. In addition, the boost
input current provides low input ripple
characteristics, making the boost converter
ideal for power factor correction applications to
regulate the input supply and improve the line
power factor. Advantages disadvantages The
boost converter is thus able to step up the
voltage at lowest component count, with a
continuous input current. And, the switch used
here has common ground with the source, making
the drive circuit and control circuit
arrangement easier. However, one disadvantage
here is that the charging current of the output
capacitor is discontinuous, resulting in a
larger capacitor size and EMI issues. Boost
converters are mainly used in applications
having power factor correction circuits such as
battery power systems and electric cars.
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Buck-Boost converters As the name itself
suggests, these converters are a combination of
the buck and boost converters, which helps to
produce an inverted output voltage, greater or
lesser than the input voltage, based on the duty
cycle. Here, the inverting converter only
delivers the energy stored by the inductor into
the load, but very large output filter
capacitors are required, and low ripple levels
are very difficult to achieve with buck-boost
converters. Working When the switch is switched
on, the diode is reverse biased and the energy
is stored in the inductor, and the capacitor
supplies current to the load. And, when it is
switched off, the energy stored in the inductor
is transferred to the load through the inductor
and forward biased diode. Advantages
disadvantages With buck-boost converters, the
input voltage can be higher or lower than the
regulated output voltage. But, the switch does
not have a ground connection, meaning that a
level translator is needed in the PWM output
circuit, which can add cost and complexity to the
design. Such converters are used mainly in
stabilizing photovoltaic cell outputs. So, what
kind of converters are suited to your
application? Find out the same and get in touch
with a trusted SMPS transformer manufacturer in
India, one like Miracle Electronics, where you
can get both off-the-shelf as well as customized
SMPS transformers, both kinds being RoHS and
REACH compliant, thus assuring quality.