Automatic voltage regulators that incorporate Pulse Width Modulated (PWM) technology in their output power stages typically employ a substantial amount of capacitance.
There are several advantages in using PWM Power stage such as higher forcing, wide frequency input range and greater immunity to waveform distortion.
Nevertheless they still require special attention when being powered from low impedance sources or when the power supply is already at nominal and switched onto the PWM power stage. Under these conditions applying the power may result in undesirable inrush current levels for a few cycles due to the large capacitance mentioned above.
The inrush current level is directly proportional to the input voltage and inversely to the power source impedance. Failure to take care of this parameter can drastically reduce the life time of your AVR. Solutions such as an inrush current limiter exists, so make sure you don’t forget to consider it.