Design and Implementation of CRM PFC Converter to Minimize Inductor Peak Current for LED TVs

A power factor correction (PFC) converter is essential for a switching mode power supply (SMPS), which is used in light-emitting diode televisions to comply with the harmonic current standard of IEC 61000-3-2 Class D. However, because of the high inductor peak current of a boost PFC converter, large-sized inductors and output electrolytic capacitors are employed. Consequently, the power density of the SMPS decreases, while the associated cost increases. This article presents a novel control method to minimize the inductor peak current in the widely used boost critical conduction mode PFC converters. The proposed scheme employs constant on-time control to satisfy the harmonic standard as well as peak current mode control to reduce the inductor current, thereby shaping the inductor current into a trapezoidal form. Thus, the proposed method reduces the size of the inductor and output electrolytic capacitors while satisfying the harmonic standards. The detailed analysis and comprehensive design procedures for the proposed method are presented. The effectiveness of the proposed approach has been verified using a 300 W prototype.