GaN Based Multiple Output Flyback Converter with Independently Controlled Outputs

Several techniques are proposed in the literature to improve the cross-regulation performance of a multiple output flyback converter (MOFC). However, some drawbacks exist: 1) inability to completely eliminate cross-regulation, 2) reduction of power density due to a high number of additional components, 3) increased losses. To overcome these challenges, this paper presents a scheme to independently control the outputs of an MOFC, thereby achieving excellent cross-regulation performance over a wide range of loads, without any additional switching or magnetic component. The unique gate dependent reverse conduction characteristics of gallium nitride (GaN) high electron mobility transistor (HEMT) is utilized to control the flow of current to each of the output capacitors. The operational principle and the steady-state analysis is provided in detail. Moreover, design considerations such as the switching frequency, GaN gate bias, leakage inductances, output capacitance etc. are discussed, focusing on their impacts on the key design goals, particularly the efficiency, power density, and output voltage ripple. Furthermore, SPICE simulations are used to demonstrate the improvement in cross-regulation over existing schemes. Finally, a 40 W dual output laboratory prototype is built to verify the analysis. The measured maximum cross-regulation is 0.2% which validates the effectiveness of the scheme.