Design of an Active PFC Flyback Converter for Auxiliary Power Supply in Power Converter Applications

Power electronic converter requires a low-power auxiliary supply to operate its control circuits. This paper presents the design and implementation of an auxiliary power supply for a three-phase inverter utilizing an active power factor correction(PFC)-based flyback converter. The auxiliary power supply provides an isolated and stable DC voltage to IGBT gate drivers, DSP controller, sensing circuit, power relay circuits and heat sink fans in three-phase inverters. The active PFC flyback converter rated for 48 W, converts universal input of 90–265 V, 50 Hz AC to 24 V, 2 A DC output. The LT3798 controller IC provides a powerful and efficient solution for designing a flyback converter with active PFC. It ensures that the input current closely follows the input voltage, achieving a power factor equal to unity. This improves power quality, minimizes harmonic distortion and ensures EMI compliance with international standards such as CISPR 32. This IC regulates the output voltage and current at varying load conditions for a wide range of input voltage. The design method involves selecting the appropriate transformer, output capacitor, snubber circuit for the MOSFET and diode, an EMI filter, and protection circuits for the controller. In addition, the paper discusses practical hardware aspects related to thermal management using PCB layout. The experimental results validate the performance of the proposed design, affirming its suitability and effectiveness for the required application.