Improved zero-crossing distortion of a boundary-conduction-mode boost converter with digital average-current-mode control

Constant-on-time control (COTC) is typically used to regulate the output voltage of boundary-conduction-mode (BCM) boost converters, while also ensuring the input line current has a near-unity power factor. The downside of COTC is that the input line current drawn by the converter suffers from zero-crossing distortion. This distortion of the input line current reduces the converter's power factor. In this work, a digital closed-loop control scheme is designed to reduce the zero-crossing distortion based on the average-current-mode control (ACMC) technique, which is commonly used in the control of continuous-conduction-mode (CCM) boost converters. A digital controller is designed for a 600 W interleaved BCM boost converter using a TMS320F28069 microcontroller. The performance of the ACMC controller is compared to that of a COTC controller.