How to avoid custom flyback transformer design


Power supplies incorporating flyback transformers are used in many different products. The topology is well documented and multiple specialized ICs are available for designers to use when developing a power supply for a specific application.
However, the component most impacting flyback power stage design is the transformer. Variables such as input/output voltage and current, number of windings, turns ratio of windings and switching frequency are used to determine the transformer characteristics needed to meet the required power supply performance. Unless the designer can follow a reference design with readily available parts they will need to either design a custom flyback transformer or find an off the shelf transformer with the appropriate characteristics. Pros of using a custom transformer is a part that exactly meets the requirements. Cons of a custom transformer are the costs and time needed to design, prototype and acquire the custom part. The challenge involved in finding an off the shelf part are all the variables and analysis involved in determining an appropriate transformer.

Würth Elektronik has developed tools to help customers with the task of finding potential off the shelf transformers for their power stage designs. REDEXPERT is an online collection of component selection and design tools.

“Power Stage Design Tools” within REDEXPERT contain transformer design tools for Discontinuous Mode (DCM), Boundary Mode (BM) and Quasi Resonant (QR) flyback power stage topologies. Once you select the power stage topology you enter design inputs for input voltage, output voltage(s)/current(s), PWM Controller and MOSFET Switch. The tool takes the design inputs and reverse engineers the database of transformers to find parts that work in that application.

Detailed discussion and examples for using the transformer tools are available in the archived Avoid Flyback Transformer Design with REDEXPERT webinar with speaker George Slama of Wurth.

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