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Power Supply Output Filter Design - Overshoot(2 of 4)
Relevance
Applies to all switching mode power supplies with output filters using inductors. The problem is illustrated with an LC filter of the type used on the output of the simple buck converter. The general problem identification process is to determine the energy that is stored in circuit inductance and capacitance under normal and abnormal conditions and make sure it causes no damage when released under normal and abnormal conditions. Two such conditions are load shedding and clearing of a shorted output.
Solvability
Make overshoot a major selection criteria in the design of the output filter and in the selection of short-circuit or overvoltage protection.
Overshoot can be minimized by minimizing the filter characteristic impedance, Zo, by decreasing inductance or increasing capacitance or both.
Some overcurrent protection circuits limit the maximum current that can flow in the output filter inductor. Others do not. For overshoot control purposes, the former are preferred.
Independent overvoltage protection circuits should be considered mandatory until careful analysis of operation in normal and abnormal operation indicate they can be eliminated or modified to the semi-independent variety.
Do not use this information for design without independent verification of the information.
