Smart Tool to Select Discontinuous Mode Flyback Transformers Released to Public

Off the shelf custom flyback transformers

For discontinuous mode flyback SMPS designs a clever online tool has been launched by Wurth Electronics Midcom Inc. Entering as little information as input voltage range, switching frequency, output voltages and current; the Smart Transformer Selector, or STS as Wurth Electronics Midcom Inc. likes to call it, will return a list of prequalified transformers where all are production released and hundreds have samples ready for off the shelf orders.

Taking the tedium out of the task, the STS searches Wurth Eletronics Midcom Inc.’s database of hundreds of SMPS transformers designed for discontinuous mode flyback operation. The STS uses power supply parameters and searches the database for parts that will not saturate, will provide the proper output voltages, will not over stress your switch, so on and so forth. “Essentially the STS looks at each transformer one at a time and does a reverse design to make sure that it will function properly under the operating conditions that you specify”, said Dean Huumala, Product Marketing and Development Manager for Wurth Electronics Micom Inc.

Analysis tabs show theoretical operation

The search results are returned in a table that lists many of the typical transformer parameters such as inductance, turns ratio and saturation current along with mechanical and safety parameters for the parts. Full specifications of the part are available for immediate down load in pdf format right from the table. The STS finds all suitable transformers, even those that were not designed specifically with the given application in mind.

The table itself can be sorted in various fashions giving the ability to hone in on those designs that best suit the specified application. Selecting any part from the list will populate an analysis tab directly below the chart which summarizes the part and its performance in the application. It shows everything from current wave forms, voltage levels and power losses to mechanical dimensions, a schematic for the application and even a 3D image showing just what the part looks like. To get more detailed information one clicks on one of the other three tabs available which reveals the details of the currents, voltages and losses.

Multiple parts compared

“A great feature of the STS is the ability to compare side by side how multiple transformers will function in your application”, adds Mr. Huumala “Selecting up to six transformers you can compare a host of parameters and analysis results side by side. This makes the final selection from the list a breeze.”

While the STS is designed for a novice, it can also be used by the experienced SMPS designer who knows just what he wants. An advanced search feature will allow those who wish to specify the inductance, saturation current and/or turns ratio themselves. The other basic parameters still must be entered as the tool needs to verify the design.

Specifying duty cycle, MOSFET and diode rating as well as controller used are all options that can be used by the advanced user. The STS will take all of these requirements into account when searching for a transformer. For all users a limited list of controllers from the IC manufacturers is provided for selection. Specifying the controller will automatically populate the duty cycle, MOSFET parameters as well as the UVLO-LO and UVLO-HI parameters as they pertain to the controller. One can still override the auto settings if they wish as in the case of an external switch being chosen rather than using the one internal to the controller.

Direct access to parts

The greatest thing about the STS is that samples for hundreds of parts are available off the shelf. No more waiting up weeks for your transformer. No minimum quantities either, if one wants to order 100, 10 or even a single piece, they can. Many of the parts found in the STS are stocked at either Digikey or Mouser and all of them direct at Wurth Electronics Midcom Inc. All of the parts listed have been proven out in the lab, are released to production and ready for order.The STS tool can be accessed at