Nonlinear-carrier control for high-power-factor rectifiers based on flyback, Cuk or Sepic converters

In this paper, nonlinear-carrier (NLC) control is proposed for high-power-factor rectifiers based on flyback, Cuk or Sepic converters operated in the continuous conduction mode. In the NLC controller, the switch duty ratio is determined by comparing a signal proportional to the integral of the switch current with a periodic nonlinear carrier waveform. The shape of the NLC waveform is determined so that the resulting input line current follows the input line voltage, as required for unity-power-factor rectification. A simple exponential carrier waveform generator is described. Using the NLC controller, input line voltage sensing, error amplifier in the current-shaping loop, and the multiplier/divider circuitry in the voltage feedback loop are eliminated. The simple, high-performance controller is well-suited for integrated-circuit implementation. Results of experimental verification on a 150 W flyback rectifier are presented.