This example is intended to show relevant modeling and simulation capabilities of SystemVision Cloud, for electrodynamic energy harvesting (EH) systems. It is not necessarily a practical EH design itself, but rather demonstrates the tool's ability to support knowledgeable users who are creating practical designs.

The mechanical and magnetic circuit sections of the model are composed of "physical" models, in that user can directly specify size and physical properties of the components. This includes the mass of the armature, the stiffness of the resonant spring, the cross section area and length of the magnetic core, the residual flux density of the permanent magnet, and the number of winding turns.

The electronics section (rectifier and boost converter) contains a mix of passive analog circuit elements as well as abstract or "math block" models to represent the state-average (non-switching) behavior of the converter. Finally, constant power load model represents the power demand for periodic transmission of data typical of an (I)IoT sensor node.

In the simulation results displayed on the schematic, the upper right waveform viewer shows the amplitude of the external vibration source (e.g. a motor or transformer housing) of 0.07mm peak at 60 Hz, equivalent to a peak acceleration of 1g (light-blue waveform). The armature spring-mass resonance frequency is 60 Hz, so the armature displacement is seen to reach the frame's travel limit of 4mm peak-to-peak (green waveform).

In the upper left, the two waveform viewers are zoomed-in near the 1 second simulation time mark, and they show the air-gap lengths and the corresponding core flux density and winding voltage. Note that the air-gaps are configured in parallel for the flux path, so the effective path reluctance is minimized when either gap approaches zero length.

In the lower right, the relatively low value of the rectified "DC" voltage is observed (red waveform), as well as the regulated boost output voltage that supplies the transmitter load.

This model of a buck converter uses a “state-average” abstraction (i.e. the actual switching effect is removed by averaging), so that it simulates very quickly. It can be used for iterative compensator tuning because it supports small-signal AC analysis. Performance metrics include line and load transient response (time-domain), as well as the open-loop phase margin (frequency-domain).

Two companion design examples show similar results for a switching circuit implementation of this buck converter. The first, "Step-Down (Buck) DC to DC Converter - Switching", shows the line and load transient performance. The second, "TDFS Loop Stability for Step-Down (Buck) DC to DC Converter - Switching", shows the open-loop frequency response. This effective "AC" analysis is performed using the TDFS method, at time-domain simulation technique for measuring frequency response.

This design shows how an abstract model of a DC to DC converter can be used to make higher level design trade-offs, before committing to or investing engineering effort in detailed circuit design. In this case, a comparison is made between a buck converter and a linear voltage regulator. A model was calibrated to represent an MC7805B, a 5V and 1A Linear Regulator, using only information supplied in the datasheet.

The model of the buck converter uses a “state-average” abstraction (i.e. the actual switching effect is removed by averaging), so that it simulates very quickly. It can be used for iterative compensator tuning, and also supports small-signal AC analysis. The efficiency and performance of both voltage conversion methods can be analyzed and compared. Performance metrics include line and load transient response, as well as both time-domain and frequency-domain ripple rejection simulations. The results provide the information needed to make key design trade-offs.

This design uses both TDFS and standard AC Analysis methods to assess the stability of a closed-loop system. The design is the "Buck DC to DC Converter", using a state-average model for the modulator function.

The use of state-average models supports AC Analysis, but TDFS (Time Domain Frequency Sweep) is also used to show the equivalency of the methods. Note that the TDFS approach can be used for systems that do not support AC Analysis, such as switching circuits or systems that contain sampling or digital control aspects. This particular example is directly comparable to the design "TDFS Loop Stability for Buck DC to DC Converter - Switching". In that design, the TDFS method is used to measure the open loop transfer function of an operational switching circuit.

Note that the approach used to characterize the loop stability, by injecting a small sinusoidal stimulus signal in series with the loop and then measuring the complex ratio of the ground referenced return signal to the injected signal, is described in:

D. Venable, “Testing Power Sources for Stability”, Venable technical paper #1, Venable Industries

This design shows how an abstract model of a DC to DC converter can be used to make higher level design trade-offs, before committing to or investing engineering effort in detailed circuit design. In this case, a comparison is made between a buck converter and a linear voltage regulator. A model was calibrated to represent an MC7805B, a 5V and 1A Linear Regulator, using only information supplied in the datasheet.

The model of the buck converter uses a “state-average” abstraction (i.e. the actual switching effect is removed by averaging), so that it simulates very quickly. It can be used for iterative compensator tuning, and also supports small-signal AC analysis. The efficiency and performance of both voltage conversion methods can be analyzed and compared. Performance metrics include line and load transient response, as well as both time-domain and frequency-domain ripple rejection simulations. The results provide the information needed to make key design trade-offs.