Analysis and Design of Choke Inductors for Switched-Mode Power Inverters

This paper presents the design, analytical estimation of power losses, and experimental measurement of choke inductors for switched-mode power inverters. The described approach is applicable to a wide variety of circuits such as Class-E inverters and converters. The expressions required to design the magnetic core in the choke inductor using the Area-Product (Ap) method are given. The equations for the dc resistance, ac resistance at high frequencies, and dc and ac power losses are provided for the solid round winding wire. To validate the presented approach, an example Class-E zero-voltage switching power inverter with practical specifications is considered. A core with air gap is selected to avoid core saturation in the choke inductor, which conducts dc current and a small ac current. The gapped core power loss density and power loss are estimated using Steinmetz empirical equation. It is shown that the winding power loss due to the dc current is dominant for the given design. A comparison between the area-product Ap method and the preexisting core geometry coefficient Kg method is presented. The measured magnitude of the inductor impedance has shown that the designed choke is useful up to 10 times the switching frequency.