Self-Excitation, Balanced, Passive Variable Inductor for Fast-Response Buck Converter

To improve the transient response speed of single-phase voltage regulators (VRs), this paper proposes a self-excitation, balanced, passive variable inductor for a fast-response Buck converter. The DC bias component of the Buck converter's inductor current intensifies with increasing load, acting as an excitation source that induces magnetic core saturation, achieving inductance reduction. This method eliminates reliance on external excitation. Firstly, an analytical model for the proposed inductor structure is established and the iterative process is used to solve for the nonlinear magnetic flux density in this paper. Then, the optimal design of the structure is achieved by the PSO (particle swarm optimization) algorithm. Finally, three 12V/3.3V@50kHz Buck converters were built for experimental comparison. Compared to a fixed inductor, the inductance of the proposed inductor decreases from 33μH to 16μH when switching the power from 50W to 75W, and the response time of the Buck converter decreases from 4ms to 1.2ms.