A Multimode 1-MHz PFC Front End With Digital Peak Current Modulation

This work presents a novel mixed-signal control scheme for a boost power factor correction (PFC) rectifier. The digital controller modulates the inductor peak current to produce a low-distortion ac line current in discontinuous conduction mode (DCM) and continuous conduction mode (CCM), without the need for average current sensing. A lookup table (LUT) optimizes efficiency at low input currents, by allowing operation at 125-500-kHz DCM based on calculated thresholds. At high input currents, the converter operates at 1-MHz CCM for reduced inductor footprint. An analog off-time generator with a digital frequency locked loop facilitates CCM operation, eliminating the need for slope compensation in the current loop and reduces frequency variations. The LUT is programmed with an adaptive output voltage of 250/450 V for low/high mains line voltage (85-265 Vrms) to optimize efficiency over a broad range of conditions. The 150-W PFC prototype operates up to 1 MHz with a peak efficiency of 95% and a total harmonic distortion of 5%.