DVM  Design Verification Module

The SIMPLIS Periodic Operating Point (POP) analysis followed by an AC analysis has a proven record of quickly and accurately measuring the AC loop response of switching power supplies. This analysis works well for stable systems where the feedback signals are represented by double precision numbers. Two distinct classes of converters exist which are incompatible with the SIMPLIS POP analysis:
The MultiTone AC Analysis was designed for these types of converters.
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In digitally controlled systems where the signals in the feedback loop are quantized into discrete levels, the POP/AC analysis is typically not applicable. The extremely small perturbation of the injected signal during the AC analysis is not large enough to produce a controlloop response. The MultiTone AC analysis, now available in the Design Verification Module (DVM) in SIMetrix/SIMPLIS 7.1, is able to provide an AC analysis of such digitally controlled systems, including closedloop response, input and output impedance, as well as conducted susceptibility. Below is a comparison of closedloop gain and phase results from a digitally controlled DC/DC converter.
The red curves represent the POP/AC data where the PID control signals are modeled as double precision numbers. The blue curves are generated by the new MultiTone AC analysis where the quantized finite bitwidth of the PID feedback signals are modeled. In both cases, the PID coefficients and the power stage components are identical.
For PFC converters using an AC input and variable frequency control, the POP/AC analysis is not appropriate. In these cases, the MultiTone AC analysis offers a way to characterize virtually any control loop. Below are the loop gain and phase results from a singlephase, continuousconduction mode PFC converter.
The red curves represent the POP/AC data using a PWM multiplier; the blue curves show the MultiTone AC results using the full NLB multiplier.
The MultiTone AC analysis injects multiple frequencies into the circuit under test during a transient simulation and then calculates the AC results using a Fourier analysis. The signal amplitude is set by the user to be large enough to insure the control loop is perturbed and that there will be a valid AC response to the perturbation. Because MultiTone AC analysis uses a transient simulation, the technique can be applied to any converter. POP convergence is not a requirement.
Both linear and decade frequency sweep modes are available with the four MultiTone tests objectives that are built in to DVM:
Using the builtin testplans for DC/DC and AC/DC converters, you can, in five minutes or less, convert a working design to run the MultiTone AC analysis.
For more details, see MultiTone AC Analysis Theory.
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