Active cancellation of capacitor ESR and ESL effects for improving converter transient and steady-state response

An active cancellator that can reduce the capacitor equivalent series resistance (ESR) and equivalent series inductance (ESL) effects and provide capacitor current information is presented. The concept is based on connecting a linear voltage source in series with the capacitor to counteract the voltage drops caused by the ESR and ESL. Due to a reduction in the effective ESR and ESL, the damped resonant frequency of the ldquomodifiedrdquo capacitor is increased. The performance of the cancellator has been evaluated on an aluminum electrolytic capacitor. The effective values of the ESR and ESL are reduced by 1850 and 6.5 times, respectively, with the cancellator. The ldquomodifiedrdquo capacitor has been applied to a practical buck regulator. The capacitor current information provided by the cancellator is used to give an extra phase boost in the feedback loop of the regulator. Experimental results show that the proposed technique can help reduce the duration of ESL spike and magnitude of the ESR step appeared in the load transient, and steady-state output voltage ripple.