Advanced Inrush Current Mitigation ‎Techniques for Microprocessor-Less High ‎Power AC/DC/DC Synch-Buck ‎Converters: A Start-up Perspective

This paper investigates the starting current of an AC/DC/DC converter, consisting of a ‎three-phase diode bridge rectifier and a synchronous buck converter. The use of ‎microprocessors in such converters increases the total cost and also reduces reliability due ‎to EMI phenomena. For this reason, by removing the microprocessor, a start-up plan ‎including a limiting starting resistor and then soft starting the switching module is proposed ‎in this paper. By modeling the system under different operating modes, a solution is ‎presented to minimize the circuit startup period, which includes minimizing the bypass time ‎of the startup resistor and reducing the switching soft startup period as possible. The ‎proposed method has been implemented on a 15-kW converter feeding from a three-phase ‎‎380 V power grid and provides up to 300 Vdc/50 Adc to supply an electroplating pool. The ‎results show that the sequential startup procedure, including using a 50 ohm/1500 w resistor ‎for 3 seconds, and then bypassing it, then starting soft switching after half a second and ‎during 1.5 s, can move this circuit to a steady state in 5 seconds, keeping current in all parts ‎below half rated current.‎