Adaptive On-Time Average Current Control Tracking in Critical Conduction Mode Three- Level Boost PFC

Constant on-time (COT) modulation is popular among boost and totem-pole power factor correction (PFC) circuits under critical conduction mode (CrM) of operation due to its inherent average current tracking ability while achieving unity power factor. However, the same technique cannot be directly used for a flying capacitor-based multilevel boost PFC under the CrM operation because of different circuit configurations for different switching states. On the other hand, multilevel boost PFC converters with high frequency and low voltage GaN devices have been gaining growing interest for their high power density and high efficiency. This paper proposes an adaptive on-time modulation technique for a three-level flying capacitor boost PFC (3LFCB-PFC) under the CrM operation, ensuring its average current tracking ability. The expressions for the required on-time for different duty ratio ranges are analytically derived. These expressions are easily implementable using the input and output voltages and load current. A comparative study shows the reduction in the effective switching frequency of the 3LFCB- PFC circuit compared to the conventional two-level counterpart. The simulation results verify a superior tracking performance. The proposed technique will help to design compact power supplies/ chargers for LED drivers, data centers, electric vehicles, telecom servers, etc.