Mixed-signal control of single-phase PFC based on a nonlinear current control method

Mixed-signal control of single-phase power factor corrected (PFC) ac-dc converters based on a new nonlinear current control method is presented. The proposed nonlinear current control combines input current feedforward with cycle-by-cycle integral control of the switch current to achieve sinusoidal input current and unity input power factor. Stability of the proposed nonlinear current control method is analyzed, and different improvement methods are presented. The resulting control performance is superior to all existing PFC control methods and can meet the requirements of various applications, including high-frequency (360–800 Hz) airborne power systems. The proposed mixed-signal implementation scheme uses an analog current controller that is simple, insensitive to noise, and independent of converter and control design parameters. A digital controller regulates the output voltage by providing a low-frequency reference to the analog current loop. A sampling rate much lower than the switching frequency can be used, thereby enabling the use of a low-speed digital control device while achieving all the benefits of digital control. A prototype design is presented to validate the theory and to demonstrate the performance of the proposed control method.