Digital control of a bridgeless SEPIC PFC AC-DC converter with variable voltage output

Instead of constant dc-link voltage, this paper proposes a PAM/PWM for PMSM drive, which provides variable dc-link voltage to PWM inverter to reduce switching loss and improve system efficiency. An optimal dc-link voltage reference can be found for a specified operation speed for a centrifugal load condition. In order to realize the variable dc-link voltage, this paper implements a variable output voltage power factor correction (VOPFC) AC-DC converter for PMSM drive with bridgeless single ended primary inductor converter (SEPIC) topology. When it operates in DCM mode input current is in-phase with input voltage automatically and yields unit power factor. Therefore current control loop can be omitted and control system is simplified. Simulation and experimental results have been carried out to verify the performance of the PFC converter.