Power-supply specifications for line and load transients describe the response of a power supply to abrupt changes in line voltage and load current. By monitoring the supply as it attempts to maintain regulation in the presence of such transients, you can observe any tendency toward output overshoot or oscillation.
Line and load transients are step functions that inject disturbances into the power supply. A load transient injects disturbance into the output by stepping the load current, and a line transient does so by stepping the line voltage. The supply's output response demonstrates its ability to attenuate the various frequency components of a line or load step. The following discussion describes these tests and the information they provide about a power supply. Read full article.