Research On Current Source Driver Technichques For1-MHz Boost PFC Converters

With fast development of the information and semiconductor technologies, power supplies forapplications such as telecommunications and computer systems are required to have higher powerdensity, smaller volumes and higher efficiencies. The PFC stage, a key component of distributed powersystems presents in the front end of AC/DC converters, is an excellent target for increasing the powerdensity and efficiency of the power supply. In order to improve the power density of the Power FactorCorrecton (PFC) converters, pushing the switching frequency higher is the most direct method. In thePFC stage, in Continuous Conduction Mode (CCM), the inductance can be reduced when the switchingfrequency increased. Furthermore, the EMI filter stage can also be further reduced when the switchingfrequency increases over400KHz. Theoretical and experimenl results have proved that when BoostPFC converter works at1MHz frequency, the power density will be greatly improved，with the newSic, GaN devices are launched, the MHz converters are the trend in future. However, today’s PFC stageis still running at100-200KHz. The major concern of increasing the switching frequency in PFC is theexcessive frequency-dependent losses, including the switching loss, the gate drive loss and the reverserecovery loss of the diode, where the switching loss is the major loss in MHz PFC converter.To solve the problems of high frequency PFC converter, the Current Source Drivers (CSDs) areinvestigted for MHz PFC converters in this thesis. Due to the fast duty cycle change, the Half-Bridge(HB) CSD can not be used for PFC applications. To solve the problem, the Full-Bridge (FB) CSD isused instead. Two types of the FB CSD are proposed for the MHz PFC converters, continuous CSD anddiscontinuous CSD. Their structure and operation principles are analyzed in deails in this thesis andcontrol methods are also proposed. The loss analysis and design procedure are also presented for theFB CSD for the boot PFC converter. Due to the fast switching speed and the switching loss reduction,comparied to the conventional Voltage Source Driver (VSD), the FB CSD can achieve higer efficiencyfor MHz Boost PFC converters. Futhermore, both the continuous and discontinuous CSDs can achieveadaptive drive current for MHz boost PFC application, this is of great advantage for the optimazation ofthe switching loss and drive loss of MHz Boost PFC converter.Comprehensive comparison of continuous and discontinuous Current Source Drivers (CSDs) arepresented in terms of switching loss reduction, driving loss and adaptive solutions for MHz boost PFCconverters in this thesis. The optimal design is also given. The relationship between these two type ofCSDs are also revealed, which provides deep insights of the CSDs in MHz PFC application.In order to verifly the theoretical analysis, two1MHz/300W Boost PFC prototypes are built in the laborary. The experimental results verified the conclusion.