Stability Analysis of Higher-order Buck Converters: Participation Factors Approach

Buck converters are widely used in point of load applications. Conventional buck converters are simple and they exhibit simpler dynamics due to second-order system. To reduce the ripples in their source current it is common practice to employ an additional L-C filter. Though this solution is effective in mitigating the ripples problem but it is at the cost of increased system order. Though higher-order converters are able to improve the steady-state performance but induce stability problems. In this paper an attempt is made to identify parameters of the higher-order buck converter which are responsible for instability using participation factors approach. Case studies are presented for the modified fourth-order buck converter and compared with the buck converter with an input L-C filter. Analytical findings are validated with stability indicating simulation and measurement results.