Build

 1. Cannot find a suitable module to do the job.

 2. Existing modules with acceptable outputs do not have certain desired features.

 3. There is suitable time and personnel to do the design.

 4. Company wants to develop the technology.

 5. Magnetics already produced for other projects, so nothing new here.

 6. Manufacturing can handle new product without error or re-learning.

 7. Greater control of the power supply as part of a project. No control if purchased.

 8. Volume needed not supported by vendor.

 9. Purchased module has unknown reliability and MTBF.

10. No worst case analysis can be done without internal details of the purchased module.

11. Cannot make changes to module design.

12. Patent questions if module is already patented.

13. Company requires two vendors for safety. Must look far and wide to find two vendors     providing the same purchased module, physically as well as electrically.

14. Purchased module becomes obsolete by vendor. No replacement available.

15. Module cannot be internally repaired. Must be removed and replaced if failure occurs.

16. Difficult to properly design I/O filters for a purchased module, since one doesn't know its     internal characteristics.

17. When you buy a module, you are buying someone else's work. Is it a good design with no     faults, or was it rushed to market too quickly. You never know.

 If many problems with a purchased module are suspected, and the above reasons are mostly true,  then engineers and managers should definitely "build." A consultant, like Power Electronic  Systems, Inc., can help or do the design and analyses if experienced people are not available.  (Management: the fees are far less than the cost of maintaining a design engineer.)

 Buy

 1. Just interested in hooking up inputs and outputs and forgetting the module.

 2. Module is O.K. as is. Do not need any other features, specs, or analyses.

 3. No changes to module are ever contemplated. Vendor willing to make any changes if needed     (maybe).

 4. Saves engineering design time on tight budgets and schedules.

 5. No one available capable of designing power systems.

 6. Testing complete by vendor. Have confidence in vendor.

 7. Only need a low module quantity.

 8. Satisfied with minimum vendor facts and figures. Have bigger problems elsewhere.

 9. Easy to purchase: one part number for one vendor, rather than a parts list of many vendors     requiring more work to obtain.

10. Can get a sample module, install it on a board, and be on with the project.

 Engineers and management agreeable with the above terms should definitely "buy" and relax.