Some electromagnetic aspects of coreless PCB transformers

In this paper, some EMI aspects of using coreless PCB transformers are addressed. Based on the antenna theory, the radiated power of a coreless PCB transformer is estimated and found to be negligible. The electromagnetic field plot of a power electronic circuit using a gate drive circuit isolated with a coreless PCB transformer has been recorded. The major radiated EMI source in the frequency range of 30 MHz to 300 MHz is found to be the copper tracks of the power circuit, where switching transients occur, rather than the coreless PCB transformer. Coreless PCB transformers essentially operate at relatively low frequency (8 MHz in this case) by near-field magnetic coupling. Experimental results have confirmed that the application of a coreless PCB transformer in a gate drive circuit for power electronic circuit will not impose any serious EMI problem on the power electronic circuit