Smart Tool to Select Discontinuous Mode Flyback Transformers Released to Public

For discontinuous mode, flyback, SMPS designs, a 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, will return a list of prequalified, off-the-shelf transformers.

Taking the tedium out of the task, the STS searches Wurth Eletronics Midcom’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.

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 download 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


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 a 3D image showing what the part looks like. To get more detailed information one of three tabs available reveals the details of the currents, voltages and losses.

“A great feature of the STS is the ability to compare, side-by-side, how multiple transformers will function in your application,” said Mr. Huumala. “Selecting up to six transformers, you can compare a host of parameters and analysis results. 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 they want. An advanced search feature allows 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 the 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 and 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.

As an added benefit to customers, the STS lists all parts which are available off the shelf. Customers eliminate a standard wait time of up to eight weeks for transformers. There are no minimum order quantities on the products listed in the Smart Transformer Selector. Most of the parts found in the STS are stocked at Digikey or Mouser, and all are stocked
directly at Wurth Electronics Midcom, Inc. The STS tool can be accessed at