Critical Inductance and Critical Bandwidth (2001)
Critical inductance and critical bandwidth concepts developed by CPES have been widely accepted by industry to improve the transient response and reduce the filter size. If the control bandwidth is pushed beyond the critical value, no further improvement of the transient response is possible. The equivalent series resistance (ESR) of the output capacitors ultimately limits the transient voltage spike. The research points out that the choices of output filter capacitor type and their associated ESR will determine the optimal switching frequency and control bandwidth and, therefore, ultimately determine the system transient responses. Also, based on the critical inductance concept, a process of determining the optimal design of output filter inductors has been developed in order to improve the transient responses as well as circuit efficiency.