Evaluation of the behavior of switch mode power supply and voltage stabilizer under voltage variations of short duration

The sensitivity of the digital equipments to the voltage variations of short duration has raised studies and evaluations that seek a better understanding of the electric and magnetic compatibility between supply and load. To guarantee a normal operation of the personal computers, it is a common practice among individuals and companies the installation of voltage regulators just before the computers. The switch power supplies in the personal computers are sensitive to voltage variations of short duration, and the voltage regulators are adopted as additional equipment for protection of the computers against the electric disturbances. However, the voltage regulators and the switch power supplies present a similar tolerance level to voltage variations of short duration. This paper presents the results of computer simulation and experimental tests of the voltage response for switch power supplies and voltage regulators when submitted to voltage sags and interruptions of short duration. The tests were accomplished based on the international standard of IEC 61000-4-11 that defines methods of immunity test and preferential range of values for electric and/or electronic equipments connected to the low voltage of a distribution network. The behaviour of the tested equipments offers subsidies to corroborate the practical use of personal computers associated to the voltage regulators.