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Buck-Boost Converter basics
The buck-boost DC-DC converter offers a greater level of capability than
the buck converter of boost
converter
individually, it as expected it extra components may be required
to provide the level of
functionality needed.
There are several formats that can be used for buck-boost converters:
+Vin, -Vout:
This configuration of a buck-boost converter circuit
uses the same number of
components as the simple buck or boost converters. However this buck-boost regulator or DC-DC
converter produces a negative output for a positive input. While this may be required or can be
accommodated for a
limited number of applications, it is not normally
the most convenient
format.
Figure: 3.27 circuit diagram of buck boost regulator
When the switch in closed, current builds up through the inductor. When the switch is opened the
inductor
supplies
current
through
the
diode
to
the
load.
Obviously the polarities (including the diode) within the buck-boost converter can be reversed to
provide a positive output voltage from a negative input voltage.
+Vin, +Vout:
The second buck-boost converter circuit allows both
input and output to be the
same polarity. However to achieve this, more components are required. The circuit for this buck
boost converter is shown below.
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