Power Tips: Giving thanks to power supply tools

Thanksgiving and football

Thanksgiving is my favorite holiday.  Food, football, more food, what is not to love?  There is no stress of buying gifts, no costumes to find.  It is also a great time to spend with family and friends and give thanks for all that is in our lives.  This makes for the perfect time to discuss tools that every power supply designer should be thankful to have.

The first place to start with a power supply design is the specifications.  The important details to know are: input voltage range, output voltage, output current, max output ripple, transient requirements, efficiency goals and many others.  The more details the engineer has before the design is started, the better.  Once all of the specifications are known, design calculations need to be made.  This leads me to the first design tool I am thankful for, Mathcad. 

Mathcad is mathematical software that allows design engineers to easily calculate both simple and complicated formulas.  The tool helps to keep track of multiple variables and allows a spreadsheet type of design procedure.  The best part of Mathcad is that it truly saves time.  Once a spreadsheet has been built, it is very quick to run through value changes and create a new design.  I have found that the more time I spend at the beginning of the design ensuring that the calculations are correct, the less time I have to spend in the lab fixing issues.

Mathcad is great for calculating formulas and keeping track of design equations.  However, sometimes the equations can be too complicated.  In these cases, it can be very easy to use a circuit simulation tool.  Every electrical engineer has used some sort of SPICE simulator in there design work.  I am most thankful for SPICE simulators. Some of the most useful simulations are very simple schematics.  I use these tools to show how ripple current is shared between different types of capacitors (ceramic and aluminum for example).  I also use a SPICE simulator to ease the complication of loop compensation.  In seconds, I can run simulations and reconfigure the loop of a buck converter.

The two previous tools are necessary to designing power supplies, but what do you do when you have the power supply board in your hand?  The equations and simulations must be verified with real hardware.  Generally speaking, the supply will behave a bit different in the real world vs. simulations and equations.  In addition to verifying the behavior, documentation is absolutely necessary to prove the operation.  Automation in the lab is definitely something to be thankful for.  We have an automated efficiency test setup in our lab.  This setup has literally saved me days of testing time.  The setup uses a simple computer program to control the multi-meters, bench supplies and electronic loads.  The program also logs the data and generates plots.  This test bench is crucial for doing power supply optimization; it allows multiple runs over many different operating conditions.  Based on this data, the designer can pick components and conditions that will maximize the efficiency.

Another tool to be thankful for is the network analyzer.  A network analyzer is necessary for debugging and documentation.  The most common use is to measure the loop response of the power supply.  It can measure the loop to help debug stability issues or improve the crossover frequency.  The network analyzer can also be used for other functions such as measuring power supply rejection ratio or input and output impedance of the power supply.  This is one tool that is necessary for every power supply designer.

The last tool that I want to cover might be the one that you are most thankful for and will save you the most time.  Of course I am talking about PowerLab!  There is no point in trying to reinvent the wheel.  The first place that I start when I get a new set of specifications is Power lab to see if there is something close.  If nothing else, starting with a previous design is always easier than a blank sheet of paper.  Power lab has over 1000 tested designs and more are added every week.  Chances are there is probably something that is close out there already.

Hopefully everyone can agree that these tools make our lives easier as power supply designers and for that I am very thankful.  Enjoy the new designs and the turkey!

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