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New Loss Measurement Method For High Frequency Magnetic Core

Fig. 1. Test Circuit Schematic.
Magnetic core loss is an emerging concern for integrated POL converters. As switching frequency increase, core itself induces loss equivalent or even higher than winding loss. Accurate evaluation is important to predict magnetic material performance and converter efficiency. A widely used conventional method (European Standard CECC 25300) is improved for high frequency measurement. The original method separates the winding loss and core loss, but very sensitive to severe phase error. So it is not accurate when measuring high frequency core loss (1MHz - 100MHz). The new method adds a cap Cr resonating with magnetizing inductor, to shift the phase angle between current and voltage from near 90° to near 0°, which reduces the phase error from over 100% to <5%.

As proven by experiment, the new method can measure the loss at 10MHz or higher, and control the total error in 10%, and can be even better with high precision instruments.

Fig. 2. 1° phase error induced loss error.

Fig. 3. Test Setup.

Fig. 4. Test Result Compared with Datasheet.
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