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.