Dead-zone digital controller for improved dynamic response of power factor preregulators

This paper presents a simple control method for improvement of dynamic responses in a digitally controlled low-harmonic rectifier with power factor correction (PFC). The controller uses a fixed or self-adjusting dead zone in analog-to-digital conversion to eliminate the output capacitor ripple from the voltage control loop. The proposed control methods are tested in a completely digitally controlled 200 W boost PFC operating at 200 kHz switching frequency. Experimental results show that the simple controller implementation results in low current harmonics and significantly improved output voltage transient responses.