1. New Power Components in Multisim 12.0
NI has updated the Multisim components database with 92 new component models that are widely used in the design of power and electromechanical devices. This database features more than 1,000 power component models; metal-oxide semiconductor, field-effect transistors (MOSFETs); switching controllers; diodes; IGBTs; SCR transformers; and other components that, along with the 22,000 components in the Multisim database (including models for basic and advanced analog parts), can help you optimize your power and electromechanical design at the SPICE simulation stage. The new models include the following:
- Power switches: New generic models for diodes, gate turnoffs, silicon-controlled rectifiers, TRIACs, transistors, and transistors with a body diode were added to the Multisim database. You can change the parameters of these generic models to model the performance of power electronics devices that do not have SPICE models at the early stage of schematic capture and simulation.
- Power controllers: New generic models of phase angle controllers and PWM controllers were added to offer the possibility of modeling and simulating these vital devices in the design of high-efficiency high-speed power converter applications.
- Reconfigurable transformers: These generic models of configurable transformers were added to the database to offer the possibility of modeling the behavior of almost any transformer in the market.
- Nonideal RLCs: These help improve the modeling of resistive losses and reactive parasitic effects of circuit components.
You can find these components in the master database under the power and the basic groups options.
Figure 1. New Power Components in Multisim 12.0 Database
2. Application Areas
In newer power device designs, specifications become more and more stringent every day. Higher efficiency, higher speed, and accurate control require powerful simulation capabilities and an optimized design environment to help designers become more productive in their prototyping approaches. The capability of modeling these power components in Multisim takes advantage of the design and simulation fidelity of circuits like single-phase and 3-phase rectifiers; inverter circuits; and buck, flyback, and forward converters.
These circuits are extremely important in every power electronics application from the smaller power supplies used in the automotive industry or PCs to the large-scale converters that are critical in connecting wind turbines and solar cells to power grids or in using high-power telecom transmitters.
Below are snippets of some circuits considered to be the building blocks of any power conversion design. A snippet is a PNG image that you can simply drag and drop into Multisim to load the design.
Figure 2. 3-Phase Inverter Using the New Models for Pulse-Width Modulation (PWM) Controllers, Nonideal RLCs, and Power Transistors
Figure 3. 3-Phase Rectifier Using the New Models for SCRs, Phase Angle Controllers, and Nonideal Resistors
3. Application Examples
This section of the tutorial examines two applications that benefit from the new power component models in Multisim 12.0.
In this application, the circuit is a 2 W bias supply that steps down an input ranging from 36 V to 78 V to an output of 12 V. This application is widely used in automotive circuits as well as telecommunications systems.
The circuit design is based on the ON Semiconductor model of integrated circuit NCP1030, which is a highly integrated power switch circuit. The part symbol, model, and footprint are available in Multisim, and the theoretical background and design steps are explained in detail in ON Semiconductor application note AND8119/D.
The Figure 4 snippet (a PNG image that you can drag and drop into Multisim to directly load the design) shows the layout that includes new components of nonideal RLC models, rectifiers, and configurable transformers.
Figure 4. 48 V to 12 V Bias Supply in Multisim
The transient analysis of the design results is shown in Figure 5.
Figure 5. Transient Analysis Results of the 48 V to 12 V Bias Supply in Multisim
The transient helps you analyze the circuit by showing a buildup of time around 10 µs for the regulated voltage to stabilize at 12 V. The RLC components help you model the nonidealities and the parasitic effects associated with all impedances. The switching controller is based on the SPICE model provided by ON Semiconductor. Once you have accurately evaluated the design of this circuit using Multisim, the circuit is ready for prototyping with minimized errors in the desired specifications.
This forward converter developed by ON Semiconductor is based on controller NCP1028, which is modeled in Multisim. NCP1028 is a high-voltage switching regulator for medium power offline switched-mode power supplies (SMPSs). This circuit provides 12 V output at up to 2 A peak output current over the entire universal input range (90 to 265 VAC), which makes it suitable for almost any application that involves power supply design.
Learn more about the technical design details in ON Semiconductor application note AND8489/D.
The following models of power components in Multisim 12.0 were used in the design:
- Configurable transformers
- Diode rectifiers
- Nonideal RLCs
- NCP1028 controllers
Figure 6 is a snippet of the design.
Figure 6. 12 V AC to DC Forward Converter Schematic
You also can show the transient response of this circuit on the oscilloscope instrument built into Multisim (see Figure 7).
Figure 7. Measured Transient Response on the Built-In Virtual Oscilloscope Instrument of Multisim
As the oscilloscope measurement shows, an AC input voltage of 180 V peak amplitude is regulated to a DC level of 12 V. The setting time of this regulator circuit is less than 10 ms. You can perform further advanced analyses to evaluate the ripple level of the DC output, the efficiency of the circuit, and the sensitivity of the circuit to parametric variations. The nonideal RLC and the configurable transformers help to accurately model all of the parasitic effects while the SPICE model of the switching control provided by ON Semiconductor almost guarantees the alignment of this simulation with a fabricated physical prototype.
4. Recommendations for Power Supply Simulation
The most informative analysis for power circuit simulation is transient analysis. You can use it to visualize the transition of voltages at the nodes from one state to another and illustrate how the circuit converges to its steady state. You need to understand the voltage potential built up on energy storing elements such as capacitors and inductors (elements charging and discharging) for design specifications and performance.
Setting an accurate transient simulation requires basic knowledge of SPICE simulation fundamentals. Transient simulation starts with a DC operating point solution with all of the time-varying elements set to an initial voltage and current values and replaced by their corresponding linear models.
Figure 8. Interactive Simulation Settings
Figure 9. Modifiable SPICE Simulation Parameters of the Transient Analysis
You need to set the Table 1 simulation parameters appropriately if the circuit fails to converge. You can find these under Simulate/Interactive Simulation Settings on the Analysis options tab. Use custom settings and click the Customize box.
|RELTOL||Relative Error Tolerance||
|GMIN||Minimum circuit conductance||
|IC||Initial node voltages||
|ITL||Upper Transient Iteration Limit||
|METHOD||Time Step Integration Method||
Table 1. Simulation Parameters That Must Be Set If the Circuit Fails to Converge
You must set the simulation time, the time step, and the initial conditions to values before running the simulation, as shown in Figure 10.
Figure 10. Transient Analysis Setup
Once the transient analysis is set appropriately and the circuit is functioning to specifications, you can perform different analyses, such as Fourier, DC sweep, and sensitivity, to evaluate other responses and confirm the design applicability.
Read more about different types of analyses in Multisim.
Learn about the fundamentals of SPICE simulation.
5. Additional Resources