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Comprehensive design environments cut through the clutter for power system designers

Wed, 02/19/2014 - 8:19am
Mike Model and Anurag Jagota, Application Engineers, GE Critical Power

Meeting the unrelenting demands of tight design schedules will always be a challenge for developers of board-mounted power architectures with point-of-load (POL) DC-DC power modules. As board complexities grow—driving drastic increases in the number of POL power rails—designers must rapidly respond with solutions that are cost-effective, reliable, efficient, can perform to spec and deliver on time. Wading through some of the material available today, such as lengthy data sheets, complex application notes and endless component databases, can actually slow down the process rather than accelerate it.

Instead, power designers need tools that embody a unified, methodical and intelligent approach to the design process, not just component selection or access to generic technical content. Central to such design environments are simulation and modeling capabilities that enable engineers to quickly focus on solutions that meet their technical requirements and help predict how alternative solutions will perform within the framework of their specific design. During a design, requirements change frequently. Having access to an integrated tool helps designers keep pace with the project.

More than a parts selector
Embedded power system designers are often bombarded with information, but are given little guidance. Having access to the specifications for POL power modules and the various support components that surround them is just the first step toward the kind of functionality that engineers need in a comprehensive design tool. A more capable toolset would encompass the entire design environment that is typically encountered whenever a POL power module is being designed into a system. Such an environment would assist with the evaluation of the available power modules that meet the requirements of the design and would guide the designer through the rest of the process of selecting, evaluating, simulating and analyzing the probable performance of the external components that will be required. Lastly, the environment should be able to illustrate the schematic of the complete power supply design, capture the bill of materials and encapsulate the full design content so it can be shared with the rest of the design team.

As a first step, a more helpful design tool would start by getting the designer in the right neighborhood of appropriate power modules based on the objective electrical and environmental specifications of the application. So, for example, if the engineer were to provide the electrical requirements—such as the input and output voltages, number of outputs, current level—as well as environmental requirements like typical temperature, minimum airflow and space restrictions to the design tool, it would produce an extensive list of power modules to consider.

Adding several subjective preferences that the designer might have in mind can narrow the field further. For example, the tool might ask the developer to make a judgment call across a range of possible responses on the importance of certain criteria such as cost, area and efficiency. The tool would then order modules that meet the objective electrical and environmental requirements by the previously identified subjective criteria.

Simulation capabilities built into the design environment would help the engineer evaluate whether the values and tolerances of the power modules being considered operate within the bounds of the design’s requirements. For example, the designer might be interested in the relationship between the maximum current outputs of the power modules being considered and the environmental requirements of the design. Alternatively, he/she might want to take a closer look at the efficiency of the power modules given the specific electrical design requirements. 

These simulations help engineers understand the tradeoffs between design requirements, as well as the tolerances and costs of the power solutions—which include complementary external devices such as resistors and capacitors. For instance, the tool might alert the designer when a resistor with unnecessarily tight tolerances is selected. This might be a case of over-design—which could drive up the cost of the system—where a resistor with looser tolerances would suffice.

Design analytics
Once all of the components have been selected, a comprehensive design environment should automatically integrate the actual power supply circuitry and generate the schematics. At this point, powerful analytics would predict how the supply would behave. The results of these analytics may lead the developer to alter the design and iterate it to determine the system’s optimal design. The ability to easily experiment with alternative design options, such as a different set of input/output capacitor banks, would give the engineer a better understanding of the circuitry’s behavior and accelerate the overall design process.

Having a number of analytical tools at the ready can be quite powerful. For example, a stability analysis could generate a Bode plot, enabling the engineer to check the crossover frequency and the phase margin for the design. Another tool might confirm whether the supply’s output voltage would remain within the required voltage range before, during and after a transient condition. This type of transient analysis would generate a plot of the output voltage and current waveforms when transients are encountered. An analysis of the design’s performance with regards to boundary conditions is also important. This would show how effectively the design would perform within the overall operating parameters of the application. This type of analytics is very important to designers with complex circuit configurations who need access to more sophisticated simulation capabilities on demand.

Determining cost
Of course, no design is complete without a cost projection. To help here, the design environment would create a comprehensive bill of materials based on the parts and automatically check online with parts distributors to determine availability and pricing. With this information, the tool can generate a cost estimate that designers can benchmark against. Once the estimated cost is established, the full design with all of its associated support materials should be gathered together in a comprehensive report that can be shared with others on the product design team.

Tools designed for power designers
The most critical characteristic of a comprehensive design environment for developers of power supplies will be that it mirror, support and automate the best practices that engineers follow. GE’s Power Module Wizard is an example of such tool. It’s free and accessible anytime, anywhere at http://ge.transim.com.  

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