Fig. 3 (a) The basic schematic of buck-boost converter,
(b) Switch on for a time duration DT,
(c) Switch off for a time duration (1-D)T.
The converter has two distinct modes of operation: Continuous Conduction
Mode (CCM), and Discontinuous Conduction mode (DCM), and
may operate in both modes, which has different characteristics. Figure
4 shows the buck-boost converter current and voltage waveforms operating
in CCM. Under the steady state operation of the converter in the
CCM, the analytical expression of (Vo/Vg), (ΔiL), and (ΔVo) can be obtained.
Equating the integral to zero of the integral
Voltage over one time period yields[2].