DCM detection for on-line adaption of control parameters for totem-pole PFC rectifier

This paper presents a current control method for totem-pole PFC-rectifiers which avoids the need for expensive sensing circuits. The design makes use of only one switch current as current feedback signal. The control method is based on a detection algorithm for conduction mode detection in mixed conduction mode (MCM) operation. Using a DSP the mode detection is calculated on-line and based on the detection state the control algorithm adapts the control parameters in a few DSP cycles. This simple current assessment enables calculation of the a control-to-inductor model for discontinuous operation mode (DCM) to modify the current loop characteristic. The controller design was performed offline and is based on the nonlinear average current mode control. Control characteristics and performance of the new method are verified by measurement results on an interleaved totem-pole PFC-rectifier for on-board charger applications with 3600 W output power. Conducted efficiency and power factor measurements illustrate the excellent performance of the converter.