Improved Online Software Tools Accelerate Power Supply Design

By Ashok Bindra

Contributed By Hearst Electronic Products


Software tools have been around for decades now, and they have helped engineers design and develop custom power supply solutions. These high-level tools are easy to use and they enable you to generate, optimize, and simulate designs that conform to your unique specifications. What’s more, they allow you to make value-based trade-offs at a design, system, and supply chain level before committing to production.

Recently, power semiconductor suppliers like Texas Instruments, Linear Technology, Fairchild Semiconductor and Intersil, to name a few, have been upgrading their online design tools with features such as expanded component libraries, new editing and simulation capabilities, and faster verification time.

TI, for instance, has updated its WEBENCH power designer tool for its SIMPLE SWITCHER DC/DC converter series with a Schematic Editor that allows engineers to modify the power supply design that was created using the online design tool, conduct Spice simulations on the new circuit, and then export the modified schematic to a computer-aided design (CAD) platform. This new feature dramatically reduces design and verification time from hours to minutes, according to the supplier.

Besides incorporating features such as multiple-mixed-output capacitors, filtering, board parasitic, and snubber circuits into the WEBENCH tool, Schematic Editor offers a library of over 40,000 components to customize the design. In addition, it allows a power designer to simulate custom power designs within the WEBENCH environment before exporting the design to industry-leading CAD development platforms (Figure 1), such as Cadence OrCAD Capture CIS, Mentor Graphics Xpedition xDX Designer, CADSoft EAGLE, and Altium Designer.

Image of TI’s Schematic Editor

Figure 1: TI’s Schematic Editor allows a power designer to simulate custom power designs within WEBENCH before exporting it to industry-leading CAD development platforms.

Schematic Editor is a major enhancement to the WEBENCH design environment as it allows a designer to edit power supply design schematics, as well as add or modify circuitry to boost functionality and performance. Finally, when the editing of a schematic is complete, it permits the designer to simulate the new modified/custom design using the Spice simulator within WEBENCH.

Prior to the addition of Schematic Editor, a designer was not able to change or modify the suggested schematic using the WEBENCH power design tool. One could change a few components within the schematic, but not the topology, notes TI. Now, with the addition of Schematic Editor, a designer can edit the suggested schematic with ease, the company says.

To fully understand how it works, go to the Schematic Editor site¹ and enter your power supply requirements in the WEBENCH Designer on the right side of the page (Figure 2). For instance, enter minimum input as 12 VDC with a maximum of 22 VDC and 3.3 VDC output at 1.5 A with ambient temperature of 30°C, and click on the “Start Design” button. Once the “Start Design” button is clicked, the tool begins to process the parameters and within seconds spills out three different types of power supply solutions to choose from. These include module, IC and controller-based solutions. Pick the one that best suits your needs. For instance, if you click on the module button, it will generate a list of parts from the SIMPLE SWITCHER family with full schematics, including external components.

Image of WEBENCH Designer tool parameters

Figure 2: Before starting the design process, enter your power supply parameters into the WEBENCH Designer tool.

The part closest to meeting your requirements is right on the top of this page. In our case, it was the TI LMZ12003. The desired input and output parameters are well within the rated specs of the suggested part. Now, click the “Open Design” button to see your schematic (Figure 3), bill of materials, duty cycle chart, operating values like efficiency and footprint, and a product folder with options to order an evaluation board, generate a Gerber file, view design documentation, export the file to CAD, share this design or edit it further.

Image of Schematic Editor

Figure 3: The Schematic Editor allows the designer to edit each and every component in the circuit with the ability to add or delete components and filters to change topology.

The new design can now be edited using the online schematic capture tools and simulated using the integrated Spice simulator. These features are easily accessible via the WEBENCH navigation toolbar on top, which allows the user to easily switch between different steps in the WEBENCH Schematic Editor. A note of caution here: the user must register online before accessing the WEBENCH power design tool from TI’s website.

Tools from Linear, Fairchild and Intersil

Similarly, Linear Technology continues to enhance its power design tool LTpowerCAD with new features and new additions to the program. As a result, the updated LTpowerCAD II provides recommendations for component values and performance estimates specific to the user’s application with Linear’s μModule and monolithic DC/DC regulator products. It guides the user through the entire design process, reducing design effort and speeding up design time (Figure 4).

Image of Linear’s LTpowerCAD tool

Figure 4: A step-by-step power supply design and simulation guide using Linear’s LTpowerCAD tool.

Unlike conventional tools, LTpowerCAD guides users throughout the entire supply design process. Aside from searching suitable Linear parts according to user specifications, LTpowerCAD guides the user to select and optimize circuit component values with suggestions and warnings. It shows real-time results of feedback loop bode plots, as well as the power stage performance. In addition, the design created can be exported to an LTspice simulation circuit for further verification of the workings of the design. The tool also provides printed circuit board (PCB) layout examples. With an Internet connection, the user can make real-time updates of the program and its component library.

Fairchild Semiconductor has also enhanced its online design and simulation tool Power Supply WebDesigner² with power train discrete (MOSFET/IGBT/Rectifier) device power loss and efficiency analysis capabilities. Intended for 100 W to 3 kW AC/DC designs as a function of input and output conditions, these new modules provide designers with power-factor correction (PFC), phase-shifted full-bridge plus secondary side synchronous rectification (PSFB+SR), power-train discrete device analysis, and a matrix of device combinations associated with these topologies. From user-specified input and output specifications with operating conditions, the tool recommends the power discrete device part numbers and displays a dashboard view of device junction temperatures, power loss analysis, and efficiency (Figure 5). Optimized for use with controllers like TI’s UCC28950 and UCC3895 where PSFB + SR is needed, it delivers the high accuracy under varying line and load conditions required in real-world applications. Like TI, Fairchild also requires registration before accessing its design tools.

Image of Fairchild’s Power Supply WebDesigner

Figure 5: After entering system input and output requirements, Fairchild’s Power Supply WebDesigner will recommend power discrete device part numbers and display a dashboard view for device junction temperatures, power loss analysis, and efficiency.

Intersil also has been refurbishing its online tool iSim³ with new features that support increasing power densities, wide input-voltage and temperature ranges, maximum efficiency, fast transient response, and other vital specifications. It is designed to help users select and simulate parts from the manufacturer’s broad portfolio of power management devices. In four simple steps, which are input/output specs, design configuration, verification and simulation, and BOM, the tool offers solutions for complex problems.

In summary, several online design tools are available today to design and develop a variety of AC/DC and DC/DC power supplies. However, each tool is tailored to serve the suppliers’ dedicated product lines. Hence, it is up to the user to investigate the pluses and minuses of each before picking the most appropriate parts for the job.

For more information on the products discussed in this article, use the links provided to access product pages on the Digi-Key website.

References
  1. TI Schematic Editor
  2. Fairchild Power Supply Web Designer
  3. Intersil iSim
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