II. INTEGRATED BUCK-BUCKBOOST CONVERTER
The circuit diagram of integrated buck-buckboost
converter consisting two input voltage sources high voltage
source Iand low voltage source I A and output voltage VQ is
shown in Fig. 1 [11], Input sources can be batteries,
ultracapacitors, or any other dc source of power. When the
power MOSFETs A/, andAT are turned off, diodes /A, and D2
will provide the path for the inductor current to flow
continuously. Through the operation of the power switches A/,
and AT. the converter is able to draw power from the two
sources simultaneously or singly.
It can be easily observed that if transistor AT is off for the
entire switching period, i.e. when input source Iis the only
source of power, the converter operates like a conventional
buck converter. Similarly, if transistor AI} is off for the entire
switching period, i.e. when input source IA is operating alone.
the converter operates like a conventional buckboost
converter. This discussion leads to the necessary conclusion
that for single use of Isource, its voltage level has to be greater
the output voltage. Different inodes of operation of this
integrated buck-buckboost converter is presented in [11] and
the voltage transfer ratio is derived as