A per-phase quick response generation circuit generates a quick response signal to determine a quick response pulse to be inserted into a pulse width modulation signal of the corresponding phase. The quick response pulse will force the upper power switch of the corresponding phase on to increase the current supply ability during load transition. A multi-phase voltage regulator with the quick response generation circuit can have different quick response pulse widths for the interleaved phases, so as to decrease the current imbalance period of the voltage regulator after load transition.