A voltage switching regulator includes a pulsewidth modulation (PWM) controller providing voltage regulation when the voltage switching regulator is experiencing being in an high-power mode. A pulse-frequency modulation (PFM) controller provides voltage regulation when the voltage switching regulator is experiencing being in a low-power mode. An error-voltage estimator enables switching between the low-power mode and the high-power mode while keeping the voltage switching regulator output in regulation between the desired minimum and maximum voltages.