Comparison of the characteristics between buck and buck-boost high-power-factor converters with pulse-space-modulation

The current-fed high-power-factor converters (buck and buck-boost converters) have several advantages, such as no lower-limit of the output-voltage control range and no rush-current of the input-current. However, the single-phase current-fed high-power-factor converter with PWM (pulse width modulation) produces undesirable lower order harmonics in the input-current. Thus, the PWM requires a bulky and costly inductor connected in the DC-side of the current-fed converter to reduce the DC-inductor-current ripples. To overcome the problem, the authors have proposed PSM (pulse-space-modulation). This paper describes a comparison of the characteristics (THD (total harmonic distortion of the input-current), the power factor and reducing DC-inductor's inductance) between buck and buck-boost high-power-factor converters applying PSM. The buck-boost converter has many advantages over the buck converter in the input current waveform, power factor and reducing DC-inductor's inductance. To illustrate the validity of the theory, experimental results obtained from a 1.2 kW setup and computer simulation results are shown.