||NAVSO P-3641A: More Power For The Dollar
Analyses performed to achieve early design maturity include, but
are not limited to, stress and stress/strength, worst case tolerance, sneak
circuit, failure modes and effects, and thermal analysis. Additional
details may be found in NAVSO P-3686, related Government publications, and
corporate design policies.
One example of the type of details that
should be pursued is represented by worst case analysis. Worst-case
parametric variations on regulator control loops must be identified and
characterized. Parametric sensitivities of critical components must be
identified. Thermal analyses should be performed for worst-case
Worst Case Analysis (WCA) is a powerful tool
for minimizing the degradation of system performance. When properly
done, WCA minimizes system failures due to variation in component parameters
caused by factors such as environmental effects and aging. A WCA is a
rigorous analytical evaluation of a circuit's performance, considering the
simultaneous existence of worst case conditions for all components. WCA
requires a detailed database for all component parameter variations which
could affect circuit or system functions. The analysis is necessary to
achieve high-reliability circuit design.
pertaining to design analysis is the use of computer aided design and analysis
tools to facilitate the analysis process. In this regard, the following
should be considered:
- Circuit simulations are useful for design and verification and must
include circuit performance and component stress analyses relative to all
large signals (e.g., voltage and current step). Small signal analysis
is useful but only valid for the selected static operating points.
Both switch frequency simulations and averaged models should be used to
support the analyses. Circuit simulations should be validated by
empirically measured data. Once validated, circuit simulation can be
used to investigate both steadystate and transient stresses which are
extremely difficult to obtain by direct measurement on power conditioning
components. Furthermore, component parameters can be varied to
facilitate design trade-offs. Although validated power supply circuit
simulations require significant engineering effort, the simulations are
significantly more versatile for evaluating design and component changes
compared to the use of circuit breadboards.
- Finite element analysis during the design process is useful for
evaluating mechanical, structural, and thermal performance. To
validate the analyses, at least two element resolutions must be used to
establish the rate of convergence of the solution.