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System Effects. The stability and performance of a switching-mode power supply installed in a system may be radically different than the stability and performance of the power supply measured by itself.
Cause. Problems are usually caused by the addition of an input EMI filter, but can also be caused by long cables to the input power source, and in some cases, by added load capacitance.
Programming. Duty-ratio (voltage) programmed power supplies usually show degradation in the loop-gain and output impedance before going unstable. This is not necessarily true of current-programmed power supplies which may show no degradation of the open voltage-loop gain or phase or the closed loop output impedance before going unstable.
Worst Case. The worst-case condition is at low line and full load. For current-programmed converters operating conditions near the discontinuous conduction mode boundary may also be a problem.
Do not use this information for design without independent verification of the information.
