Implementation of Discontinuous PWM and possible Impact to TinyDIP/SMD Smart Power Modules without Heat Sink

Cost-sensitive appliances are the driving force for the use of smart power modules (SPM) without heat sinking. However, the increased thermal resistance from junction to ambient limits the maximum permissible output current.

There are two different techniques to optimize the overall application: The first is the use a module with lower R_DS(on) and lower switching energies. The second is to use discontinuous PWM which causes lower switching losses. The differences between continuous and discontinuous PWM will be compared, showing how this choice affects the current range, device temperature and other factors. This article investigates the use of the Fairchild Semiconductor TinyDIP/SMD Motion-SPM™(Smart Power Module) without heat sinking.

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About the author

Dr. Stephan Chmielus is Field Application Engineer at Fairchild Semiconductor Corp. He received the Ph.D. degree from the Technical University of Braunschweig/Germany in the field of physics of high-power semiconductors. His main interests are inverter topologies for AC motor drives including hardware and software.