HF Transformer Measurement and Modeling
How to measure and model high-frequency magnetics for switching power supplies. Essential steps for both custom-designed parts, or purchased components.
Power Supply Design Tips
This article points out some of the issues involved in designing, measuring, and modeling high-frequency magnetics for switching power supplies.
Despite efforts from some magnetics vendors to provide off-the-shelf components to power supply designers, almost all high-performance magnetics are custom. There are many deep and complex issues involved in the design of magnetics. I will try to cast some light on just a few of these issues.
Transformer Design Example
Figure 1 shows a simple 1:1 transformer. The transformer uses an ungapped EPC-25 core from TDK, made from PC-44 material. This transformer was designed for use in a 60 W forward converter with 36-60 V input and 12 V output.
Figure 1: A simple 1:1 transformer designed for a 100 kHz, 60 W forward converter.
Figure 2 shows the winding layout, with just a single layer of 18 turns for the primary winding, a layer of thin insulation tape, and a single layer of 18 turns for the secondary winding.
Figure 2: Winding layout of the transformer of Figure 1.
This is a very straightforward, easy-to-manufacture design of a two-winding transformer. However, as you will see below, the resulting circuit element created is anything but simple.
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